Research Article Highly Compact MIMO Antenna System for...
11
Research Article Highly Compact MIMO Antenna System for LTE/ISM Applications Lingsheng Yang, Tao Li, and Su Yan Jiangsu Key Laboratory of Meteorological Observation and Information Processing, Nanjing University of Information Science & Technology, Ningliu Road, Nanjing 210044, China Correspondence should be addressed to Lingsheng Yang; [email protected] Received 13 June 2015; Revised 24 August 2015; Accepted 6 September 2015 Academic Editor: Miguel Ferrando Bataller Copyright © 2015 Lingsheng Yang et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Planar monopole antenna is proposed as the antenna element to form a compact dual-element multiple-input-multiple-output (MIMO) antenna system for LTE2300 (used in Asia and Africa) and ISM band operation. e system can cover a 310 MHz (2.20– 2.51 GHz) operating bandwidth, with the total size of 15.5 mm × 18 mm × 1.6 mm. Measured isolation higher than 16 dB is obtained without any specially designed decoupling structures, while the edge-to-edge element spacing is only 7.8 mm (0.08 at 2.20 GHz). Radiation characteristics, correlation coefficient, and the performance of the whole system with a metal sheet and a plastic housing show this system is competitive for practical MIMO applications. e antenna element is further used to build an eight-element MIMO antenna system; also good results are achieved. 1. Introduction MIMO antenna systems are widely used in modern wireless terminals [1, 2]. e use of multiple antennas can increase the data rate without extra need of bandwidth and power levels. However, in practical mobile terminal design, the space for antenna system is highly limited. When elements are close to each other, strong electromagnetic coupling will occur. How to obtain a compact MIMO antenna system with a wide bandwidth while maintaining adequate isolation between the elements becomes a challenging task [3–5]. Electromagnetic band-gap (EBG) structures [6, 7] are used to suppress the surface wave and enhance the isolation. But for this method, the size of the EBG elements is always larger than 0.1 0 and the structure is complicated in practical design and can affect the radiation characteristics of the whole system. Defected ground plane structures (DGS) are used in [8]; the performance will be deteriorated when placed closely to conductive objects. Elements are placed orthogo- nally in [9]; the arrangement makes the antenna elements have orthogonal polarization which can reduce the mutual coupling between the antennas. Besides the arrangement of antenna elements, placing metal strips between elements [10, 11], changing the structure of the ground [12–14], and adding lumped element on the ground [15] are used to further improve the isolation of the whole system. In [16, 17], filtering structures like slotted meander-line resonators and modi- fied serpentine structure are used to enhance the isolation between two microstrip patch antennas. e structures are complicated in design and only effective at single resonant frequency, and the total systems are large in size and not wide in bandwidth (60 MHz for [17]). In this paper, two symmetric planar monopole antennas are used to form the MIMO antenna system. e total dimension of the MIMO system is only 15.5 × 18 mm 2 , less than 12.8% of the size reported in [17]. A measured operating band of 310 MHz (2.20–2.51 GHz) is obtained to cover the LTE 2300/ISM2.45 GHz operation. Isolation higher than 16 dB can be achieved with a small edge-to-edge separation of 2.6 mm (0.02). e correlation coefficients between the two elements are well less than 0.3 and total efficiencies are larger than 78%, which made this MIMO antenna system competitive for mobile MIMO terminal designs. Hindawi Publishing Corporation International Journal of Antennas and Propagation Volume 2015, Article ID 714817, 10 pages http://dx.doi.org/10.1155/2015/714817
Transcript of Research Article Highly Compact MIMO Antenna System for...
Research ArticleHighly Compact MIMO Antenna System forLTEISM Applications
Lingsheng Yang Tao Li and Su Yan
Jiangsu Key Laboratory of Meteorological Observation and Information ProcessingNanjing University of Information Science amp Technology Ningliu Road Nanjing 210044 China
Correspondence should be addressed to Lingsheng Yang ylsinchina163com
Received 13 June 2015 Revised 24 August 2015 Accepted 6 September 2015
Academic Editor Miguel Ferrando Bataller
Copyright copy 2015 Lingsheng Yang et alThis is an open access article distributed under the Creative CommonsAttribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited
Planar monopole antenna is proposed as the antenna element to form a compact dual-element multiple-input-multiple-output(MIMO) antenna system for LTE2300 (used in Asia and Africa) and ISM band operation The system can cover a 310MHz (220ndash251 GHz) operating bandwidth with the total size of 155mm times 18mm times 16mm Measured isolation higher than 16 dB is obtainedwithout any specially designed decoupling structures while the edge-to-edge element spacing is only 78mm (008120582 at 220GHz)Radiation characteristics correlation coefficient and the performance of the whole system with a metal sheet and a plastic housingshow this system is competitive for practical MIMO applications The antenna element is further used to build an eight-elementMIMO antenna system also good results are achieved
1 Introduction
MIMO antenna systems are widely used in modern wirelessterminals [1 2]The use of multiple antennas can increase thedata rate without extra need of bandwidth and power levelsHowever in practical mobile terminal design the space forantenna system is highly limited When elements are closeto each other strong electromagnetic coupling will occurHow to obtain a compact MIMO antenna system with a widebandwidth while maintaining adequate isolation between theelements becomes a challenging task [3ndash5]
Electromagnetic band-gap (EBG) structures [6 7] areused to suppress the surface wave and enhance the isolationBut for this method the size of the EBG elements is alwayslarger than 01120582
0and the structure is complicated in practical
design and can affect the radiation characteristics of thewhole system Defected ground plane structures (DGS) areused in [8] the performancewill be deteriorated when placedclosely to conductive objects Elements are placed orthogo-nally in [9] the arrangement makes the antenna elementshave orthogonal polarization which can reduce the mutualcoupling between the antennas Besides the arrangement
of antenna elements placing metal strips between elements[10 11] changing the structure of the ground [12ndash14] andadding lumped element on the ground [15] are used to furtherimprove the isolation of the whole system In [16 17] filteringstructures like slotted meander-line resonators and modi-fied serpentine structure are used to enhance the isolationbetween two microstrip patch antennas The structures arecomplicated in design and only effective at single resonantfrequency and the total systems are large in size and not widein bandwidth (60MHz for [17])
In this paper two symmetric planar monopole antennasare used to form the MIMO antenna system The totaldimension of the MIMO system is only 155 times 18mm2less than 128 of the size reported in [17] A measuredoperating band of 310MHz (220ndash251 GHz) is obtainedto cover the LTE 2300ISM245GHz operation Isolationhigher than 16 dB can be achieved with a small edge-to-edgeseparation of 26mm (002120582) The correlation coefficientsbetween the two elements are well less than 03 and totalefficiencies are larger than 78 which made this MIMOantenna system competitive for mobile MIMO terminaldesigns
Hindawi Publishing CorporationInternational Journal of Antennas and PropagationVolume 2015 Article ID 714817 10 pageshttpdxdoiorg1011552015714817
2 International Journal of Antennas and Propagation
②①
Wsub
Lsu
b
W0
W1
W4
W2
W3
Wn
Wg
Wf
x
yz
Lm Wm
L1
L2 L
f
Ln
Lg
Wp
Figure 1 Proposed antenna configuration
200
150
100
50
0
J(A
m)
Figure 2 Surface current distribution when both elements are excited at 245GHz
2 MIMO Antenna Design
21 Proposed Antenna Configuration Figure 1 shows thegeometry of the proposed dual-element MIMO antenna forLTEISM operation In this paper the presented antennasystem is formed by two symmetric planar monopole anten-nas and is printed on a 16mm thick FR4 substrate ofrelative permittivity 44 and loss tangent 002 The detaileddimensions of the proposed MIMO antenna system are asfollows 119871 sub = 155mm 119882sub = 18mm 119882
0= 18mm
1198821= 33mm 119882
2= 2mm 119882
3= 06mm 119882
4= 09mm
119882119891= 04mm119882
119892= 02mm119882
119898= 1mm119882
119899= 02mm
119882119901= 46mm 119871
1= 54mm 119871
2= 4mm 119871
119891= 55mm
119897119892= 78mm 119871
119898= 26mm and 119871
119899= 3mm
22 Design Procedure The limitation of space becomesthe most challenging task in designing antennas for mod-ern wireless devices Meanwhile electrically small antenna
always faces a narrow bandwidth problem Planar monopoleantenna has attractive characteristics such as simple struc-ture omnidirectional radiation pattern low profile and widebandwidth whichmade it a competitive candidate forMIMOantenna systems
In this paper the radiation patch and ground of theantenna are on the same side of the substrate In order todesign the antenna to resonate at the desired frequency weuse the following two equations in parameters optimization
120582 =
119888
radic120576eff119891 (1)
with
120576eff =120576119903+ 1
2
(2)
In Figure 2 both elements are excited and when 119882119892=
02mm the resonant frequency is 245GHz and the length
International Journal of Antennas and Propagation 3
Wg = 01mmWg = 02mmWg = 03mm
Wg = 04mmWg = 05mm
0
minus5
minus10
minus15
minus20
minus2520 22 24 26 28 30
Frequency (GHz)
S 11
(dB)
(a)
0
minus5
minus10
minus15
minus20
minus2520 22 24 26 28 30
Frequency (GHz)
S 11
(dB)
Wf = 02mmWf = 03mm
Wf = 04mmWf = 05mm
(b)
0
minus5
minus10
minus15
minus20
minus2520 22 24 26 28 30
Frequency (GHz)
S 11
(dB)
Wn = 01mmWn = 02mm
Wn = 03mmWn = 04mm
(c)
Figure 3 Simulated reflection coefficients as a function of (a)119882119892 (b)119882
119891 and (c)119882
119899
of the surface current path (the dot line in Figure 2) at thisfrequency is 186mm which is one-quarter of the wavelengthcalculated by (1) When 119882
119892= 04mm the resonant
frequency shifts to 253GHz and the length of the surfacecurrent path changed to 180mm which is just one-fourth ofthe wavelength at this frequency The changes of119882
119899and119882
119891
have similar effect on the antenna resonance Figure 3 showsthe relationship between the width of 119882
119892 119882119899 and 119882
119891and
the reflection coefficientsFigure 4 is the surface current when only element number
1 is excited at 245GHz Because of the high isolation betweenantenna elements little coupling current is on the otherelement Compared to the current rotation in Figure 2 thedirection of the coupling current on element number 2 in
Figure 4 is opposite with the excited current on elementnumber 2 in Figure 2
Two types of dual-element antenna arrays are demon-strated in Figures 5(a) and 6(a) The two elements are nolonger symmetrical but are in the same direction For TypeI the edge-to-edge separation of the ground is the same withthe proposed one considering the shape of the radiationpatch the distance between the two elements is decreased andthe isolation deteriorated shown in Figure 5(b)
For Type II the space between the two radiation patchesis kept the same with the proposed one the actual dis-tance between the antenna elements is increased but theisolation is still lower than the proposed MIMO antenna
4 International Journal of Antennas and Propagation
200
150
100
50
0
J(A
m)
Figure 4 Surface current distribution when only one element isexcited at 245GHz
system So the isolation is affected not only by the dis-tance between elements but also by the rotation of thecurrents on the radiation patch Due to the well knownskin effect the two elements can be seen acting like twoloop antennas at the operating band So when only oneantenna is excited the coupled current on the other elementhas the same rotation or polarization with the exited one(Figure 4) while two elements are excited simultaneouslythe rotation or the polarization is just opposite (Figure 2)this to some extent reduced the coupling between theelements
The two antenna elements can also be orthogonallyplaced as shown in Figure 7(a) Compared to the proposedMIMO antenna system the isolation is 1-2 dB higher dueto the arrangement of the antenna element However thesize of the total system is larger than the proposed one Sothe final choice is a compromise between space and systemperformance
3 Results and Discussion
31 Measured Results Figure 8 shows the photograph of thefabricated antenna The antenna elements are fed by 50ΩMCX connectors [18]
The simulated and measured 119878 parameters of the MIMOantenna system are shown in Figure 9 The simulated resultswere achieved by Ansoft HFSS version 15 while the mea-sured results were obtained by using Agilent 85058E vectornetwork analyzer The simulated bandwidth was 320MHz(226ndash258GHz) the simulated 119878
11curve coincides with
the simulated 11987822
curve and the measured bandwidth was310MHz (220ndash251 GHz) The difference between them wasprobably due to the fabricated imperfections and the lossof the feeding cable and connectors The measured minus10 dBimpedance bandwidth can cover the desired LTE 2300 and245GHz ISM band
Lm
Size 18mm times 155mm(a)
0
minus5
minus10
minus15
minus20
minus25
Spa
ram
eter
s (dB
)
20 22 24 26 28
Frequency (GHz)
S11S22
S12(S21)S21 prototype
(b)
Figure 5 (a) MIMO antenna system Type I (b) 119878 parameters ofType I
Figure 10 shows the isolation between antenna elementsThrough the whole operating band the isolation is higherthan 16 dB
The correlation coefficient (120588) is an important parameterto evaluate the diversity performance of the multiantennasystems The lower 120588 results in better MIMO system perfor-mance It is usually calculated from 3D radiation patternsHowever this procedure is rather complicate recent researchindicates that the correlation coefficient can be easily derivedfrom the 119878-parameters [19] with the following expression
10038161003816100381610038161003816120588119894119895
10038161003816100381610038161003816=
10038161003816100381610038161003816119878119894119894
lowast119878119894119895+ 119878119894119895
lowast119878119895119895
10038161003816100381610038161003816
radic10038161003816100381610038161003816(1 minus1003816100381610038161003816119878119894119894
21003816100381610038161003816minus
10038161003816100381610038161003816119878119895119894
210038161003816100381610038161003816) (1 minus
10038161003816100381610038161003816119878119895119895
210038161003816100381610038161003816minus
10038161003816100381610038161003816119878119894119895
210038161003816100381610038161003816) 120578119894120578119895
10038161003816100381610038161003816
(3)
International Journal of Antennas and Propagation 5
Lg
Size 216mm times 155mm
(a)
0
minus5
minus10
minus15
minus20
minus2520 22 24 26 28
Frequency (GHz)
Spa
ram
eter
s (dB
)
S11S22
S12(S21)S21 prototype
(b)
Figure 6 (a) MIMO antenna system Type II (b) 119878 parameters of Type II
78mm
Size 315mm times 155mm
(a)
0
minus5
minus10
minus15
minus25
minus35
minus20
minus30
20 22 24 26 28
Frequency (GHz)
Spa
ram
eter
s (dB
)
S11S22
S12(S21)S21 prototype
(b)
Figure 7 (a) Orthogonally arranged MIMO antenna system (b) 119878 parameters
Figure 11 shows the correlation coefficient between theantenna elements of the proposed MIMO antenna systemThe antenna efficiency was higher than 78 through theworking band The results are well below 03 which is themaximum value set for 4G standards [20]
The gain of the proposedMIMOantenna system is shownin Figure 12 The simulated peak gain in the +119911 direction is072 dBi at 241 GHz and the measured peak gain is 062 dBiat 24GHz
The radiation pattern of the proposed MIMO antennasystem is shown in Figure 13 The radiation pattern wasobtained when one element was excited and the other is
terminated with a 50 ohm load The radiation pattern is justlike a monopole which has an omnidirectional radiation inthe119867 plane at the resonant frequency
32 Eight-Element MIMO Systems According to [21] theincrease of the number of transmitter antennas and receiverantennas can improve the communication quality andincrease the channel capacity without extra radiation powerand spectrum bandwidth An eight-element MIMO antennasystem was also fabricated and measured Its measured
6 International Journal of Antennas and Propagation
Figure 8 Photograph of the fabricated MIMO antenna system
0
minus5
minus10
minus15
minus20
minus30
minus25
20 22 24 26 28
Frequency (GHz)
Spa
ram
eter
s (dB
)
S11 simulatedS22 simulated
S11 measurementS22 measurement
Figure 9 Simulated and measured 119878 parameters of the proposedMIMO antenna system
minus10 dB bandwidth is 340MHz (218ndash252GHz) as shownin Figure 14(a) good agreement is realized for the sake ofclarity we only put the results of four antennas here Themeasured isolation between antennas is lower than minus15 dB atthe whole operating band The simulated radiation efficiencyof the antenna element is higher than 77 over the wholeband The correlation coefficient can be calculated by using(3) As plotted in Figure 14(d) the value is far smaller than03
33 Practical Applications For practical applications MIMOantenna system is integrated with other components suchas circuit board and LCD screen which means that aconductive plane under the system should be taken intoconsideration
In Figure 15(a) the MIMO antenna system was placedabove a metal sheet separated by free space The separationbetween the conductive board and antenna bottom sidewas varied from 1 to 5mm in 1-mm steps Figures 15(b)and 15(c) show the reflection coefficients and the isolationcharacteristics of the antenna element over a metal sheet atdifferent distances
minus15
minus20
minus2520 22 24 26 28
Frequency (GHz)
Isol
atio
n (d
B)
S12(S21) simulatedS12(S21) measurement
Figure 10 Isolation of MIMO antenna system
Frequency (GHz)
0016
0014
0012
0010
0008
0006
0004
0002
000020 22 24 26 28 30
Antenna 1 and antenna 2
Cor
relat
ion
coeffi
cien
t
Figure 11 Correlation coefficient curve for the proposed MIMOantenna system
Frequency (GHz)
SimulationMeasurement
10
05
00
minus05
minus10
minus15
minus20
minus25
Gai
n (d
Bi)
21 22 23 24 25 26
Figure 12 Gain of MIMO antenna system
International Journal of Antennas and Propagation 7
0
minus10
minus20
minus30
minus40
minus30
minus20
minus10
0
0
30
60
90
120
150
180
210
240
270
300
330
245GHz-Phi-simulation245GHz-Theta-simulation245GHz-Phi-measurement245GHz-Theta-measurement
XZ
(a)
0
minus10
minus20
minus30
minus20
minus10
0
0
30
60
90
120
150
180
210
240
270
300
330
245GHz-Phi-simulation245GHz-Theta-simulation245GHz-Phi-measurement245GHz-Theta-measurement
YZ
(b)
0
minus10
minus20
minus30
minus20
minus10
0
0
30
60
90
120
150
180
210
240
270
300
330
245GHz-Phi-simulation245GHz-Theta-simulation245GHz-Phi-measurement245GHz-Theta-measurement
XY
(c)
Figure 13 Radiation pattern of the proposed MIMO antenna at 245GHz (a) 119909119911-plane (b) 119910119911-plane and (c) 119909119910-plane
It was found that by using a metal sheet the resonantfrequency of the individual antenna element shifted Asthe distance between the antenna and conductive planeincreased the effect weakens When the board is closelyplaced under the system like 1mm the resonant frequencychanged most but the working band can still cover theLTE2300 and 245GHz ISM band This is unlike the systemreported in [22] the antenna system does not have any
special designed structures on the back side of the sub-strate so it is not obligatory to place the system carefullysuch that its bottom side maintains a minimum distancelike 3 to 5mm from any conductive plane for practicaldesign
Figure 16(a) shows a 1mm thick plastic housing which isused to simulate the practical case of thewireless terminals Insimulation the relative permittivity of the plastic housing is
8 International Journal of Antennas and Propagation
340
95
78
54
46
95
55
580
150
215
55
215
40
09
20
40
30
18
02
020418
06
10
33
xy
z
05
➃➄➅➆
➀➇
➁➂
(a)
20 22 24 26 28
Frequency (GHz)
minus10
minus5
0
minus15
minus20
minus25
minus30
minus35
Spa
ram
eter
s (dB
)
S11 simulationS22 simulationS33 simulationS44 simulation
S11 measurementS22 measurementS33 measurementS44 measurement
(b)
Isol
atio
n (d
B)
20 22 24 26 28
Frequency (GHz)
S12S13S14
S16S17S18
S15
minus10
minus15
minus20
minus25
minus30
minus35
minus40
minus45
minus50
(c)
0024
0020
0016
0012
0008
0004
0000
Cor
relat
ion
coeffi
cien
t
20 22 24 26 28 30
Frequency (GHz)
Antennas 1 and 2
Antennas 1 and 3
Antennas 1 and 4
Antennas 1 and 5
Antennas 1 and 6Antennas 1 and 7Antennas 1 and 8
(d)
Figure 14 (a) Geometry of the 8-element MIMO antenna system (b) Reflection coefficients of the MIMO antenna system (c) Measuredisolation between MIMO antenna elements (d) Correlation coefficient |120588| curves for the proposed MIMO antenna system
set as 33 and the loss tangent is 002 the same as [23] Figures16(b) and 16(c) show the influence of the plastic housing onreflection coefficients and isolation Differences between thetwo cases are small and acceptable and show this MIMOsystem is competitive for practical application
4 Conclusion
Symmetric planar monopole antenna for compact multiele-ment MIMO antenna systems is proposed Isolation higher
than 15 dB over the operating band is realized by using polar-ization diversity of the antenna elements Correlation coeffi-cient 119878-parameters radiation characteristics and acceptableperformance when placed with conductive plane and plastichousing show that the proposed antenna arrays can be usedfor practical MIMO applications
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
International Journal of Antennas and Propagation 9
Metal sheet(a)
20 22 24 26 28
Frequency (GHz)
minus10
minus5
0
minus15
minus20
minus25
minus30
minus35
Spa
ram
eter
s (dB
)
Without metal sheet1mm2mm
3mm4mm5mm
(b)
20 22 24 26 28
Frequency (GHz)
minus15
minus20
minus25
minus30
minus35
Isol
atio
n (d
B)
S12 and S211mm2mm
3mm4mm5mm
(c)
Figure 15 (a) Proposed MIMO antenna with a metal sheet sepa-rated by free space (b) Reflection coefficients of theMIMO antennasystemwith ametal sheet (c) Isolation of theMIMOantenna systemwith a metal sheet
Plastichousing
(a)
20 22 24 26 28
Frequency (GHz)
minus10
minus5
0
minus15
minus20
minus25
Spa
ram
eter
s (dB
)
S11 with plastic housingS11 without plastic housing
(b)
20 22 24 26 28
Frequency (GHz)
Isol
atio
n (d
B)
minus15
minus20
minus30
minus25
S12 and S21 with plastic housingS12 and S21 without plastic housing
(c)
Figure 16 (a) Proposed antenna with plastic housing (b) Reflectioncoefficients (c) Isolation
10 International Journal of Antennas and Propagation
Acknowledgment
This work was supported by the Priority Academic Pro-gram Development of Jiangsu Higher Education Institutions(PAPD)
References
[1] T Kokkinos E Liakou and A P Feresidis ldquoDecouplingantenna elements of PIFAarrays onhandheld devicesrdquoElectron-ics Letters vol 44 no 25 pp 1442ndash1444 2008
[2] H Li J Xiong Z Ying and S L He ldquoCompact and low profileco-locatedMIMO antenna structure with polarisation diversityand high port isolationrdquo Electronics Letters vol 46 no 2 pp108ndash110 2010
[3] S Zhang P Zetterberg and S He ldquoPrinted MIMO antennasystem of four closely-spaced elements with large bandwidthand high isolationrdquo Electronics Letters vol 46 no 15 pp 1052ndash1053 2010
[4] C Yang J Kim H Kim J Wee B Kim and C Jung ldquoQuad-band antenna with high isolation MIMO and broadbandSCS for broadcasting and telecommunication servicesrdquo IEEEAntennas and Wireless Propagation Letters vol 9 pp 584ndash5872010
[5] S Park and C Jung ldquoCompact MIMO antenna with highisolation performancerdquo Electronics Letters vol 46 no 6 pp390ndash391 2010
[6] H S Farahani M Veysi M Kamyab and A Tadjalli ldquoMutualcoupling reduction in patch antenna arrays using a UC-EBGsuperstraterdquo IEEE Antennas and Wireless Propagation Lettersvol 9 pp 57ndash59 2010
[7] G Exposito-Domınguez J M Fernandez-Gonzalez P Padillaand M Sierra-Castaner ldquoNew EBG solutions for mutual cou-pling reductionrdquo in Proceedings of the 6th European Conferenceon Antennas and Propagation (EUCAP rsquo12) pp 2841ndash2844IEEE Prague Czech Republic March 2012
[8] A Habashi J Nourinia and C Ghobadi ldquoA rectangulardefected ground structure (DGS) for reduction of mutualcoupling between closely-spaced microstrip antennasrdquo in Pro-ceedings of the 20th Iranian Conference on Electrical Engineering(ICEE rsquo12) pp 1347ndash1350 IEEE Tehran Iran May 2012
[9] L Wang and B Huang ldquoDesign of ultra-wideband MIMOantenna for breast tumor detectionrdquo International Journal ofAntennas and Propagation vol 2012 Article ID 180158 7 pages2012
[10] M Gallo E Antonino-Daviu M Ferrando-Bataller MBozzetti J M Molina-Garcia-Pardo and L Juan-Llacer ldquoAbroadband pattern diversity annular slot antennardquo IEEE Trans-actions on Antennas and Propagation vol 60 no 3 pp 1596ndash1600 2012
[11] D-G Kang J Tak and J Chio ldquoMIMO antenna with highisolation for WBAN applicationsrdquo International Journal ofAntennas and Propagation vol 2015 Article ID 370763 7 pages2015
[12] Y K Choukiker S K Sharma and S K Behera ldquoHybrid fractalshape planar monopole antenna covering multiband wirelesscommunications with MIMO implementation for handheldmobile devicesrdquo IEEE Transactions on Antennas and Propaga-tion vol 62 no 3 pp 1483ndash1488 2014
[13] Q Zeng Y Yao S Liu J Yu P Xie and X Chen ldquoTetrabandsmall-size printed strip MIMO antenna for mobile handset
applicationrdquo International Journal of Antennas and Propagationvol 2012 Article ID 320582 8 pages 2012
[14] KWang R AMMauermayer and T F Eibert ldquoCompact two-element printedmonopole arraywith partially extended groundplanerdquo IEEE Antennas and Wireless Propagation Letters vol 13pp 138ndash140 2014
[15] J Park J Choi J-Y Park and Y-S Kim ldquoStudy of a T-shaped slot with a capacitor for high isolation between MIMOantennasrdquo IEEE Antennas andWireless Propagation Letters vol11 pp 1541ndash1544 2012
[16] M G N Alsath M Kanagasabai and B BalasubramanianldquoImplementation of slotted meander-line resonators for isola-tion enhancement in microstrip patch antenna arraysrdquo IEEEAntennas and Wireless Propagation Letters vol 12 pp 15ndash182013
[17] H Arun A K Sarma M Kanagasabai S Velan C Ravitejaand M G N Alsath ldquoDeployment of modified serpentinestructure for mutual coupling reduction in MIMO antennasrdquoIEEEAntennas andWireless Propagation Letters vol 13 pp 277ndash280 2014
[18] httpsenwikipediaorgwikiMCX connector[19] S Blanch J Romeu and I Corbella ldquoExact representation of
antenna system diversity performance from input parameterdescriptionrdquo Electronics Letters vol 39 no 9 pp 705ndash707 2003
[20] 3GPP ldquoEUTRA user equipment radio transmission and recep-tionrdquo 3GPP TS 36101 V830 September 2008
[21] L Song and J Shen Evolved Cellular Network Planning andOptimization for UMTS and LTE CRCPress London UK 2011
[22] M S Sharawi M U Khan A B Numan and D N Aloi ldquoACSRR loaded MIMO antenna system for ISM band operationrdquoIEEE Transactions on Antennas and Propagation vol 61 no 8pp 4265ndash4274 2013
[23] Y-L Ban J-H Chen J L-W Li and Y J Wu ldquoSmall-sizeprinted coupled-fed antenna for eight-band LTEGSMUMTSwireless wide area network operation in an internal mobilehandsetrdquo IET Microwaves Antennas amp Propagation vol 7 no6 pp 399ndash407 2013
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Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
2 International Journal of Antennas and Propagation
②①
Wsub
Lsu
b
W0
W1
W4
W2
W3
Wn
Wg
Wf
x
yz
Lm Wm
L1
L2 L
f
Ln
Lg
Wp
Figure 1 Proposed antenna configuration
200
150
100
50
0
J(A
m)
Figure 2 Surface current distribution when both elements are excited at 245GHz
2 MIMO Antenna Design
21 Proposed Antenna Configuration Figure 1 shows thegeometry of the proposed dual-element MIMO antenna forLTEISM operation In this paper the presented antennasystem is formed by two symmetric planar monopole anten-nas and is printed on a 16mm thick FR4 substrate ofrelative permittivity 44 and loss tangent 002 The detaileddimensions of the proposed MIMO antenna system are asfollows 119871 sub = 155mm 119882sub = 18mm 119882
0= 18mm
1198821= 33mm 119882
2= 2mm 119882
3= 06mm 119882
4= 09mm
119882119891= 04mm119882
119892= 02mm119882
119898= 1mm119882
119899= 02mm
119882119901= 46mm 119871
1= 54mm 119871
2= 4mm 119871
119891= 55mm
119897119892= 78mm 119871
119898= 26mm and 119871
119899= 3mm
22 Design Procedure The limitation of space becomesthe most challenging task in designing antennas for mod-ern wireless devices Meanwhile electrically small antenna
always faces a narrow bandwidth problem Planar monopoleantenna has attractive characteristics such as simple struc-ture omnidirectional radiation pattern low profile and widebandwidth whichmade it a competitive candidate forMIMOantenna systems
In this paper the radiation patch and ground of theantenna are on the same side of the substrate In order todesign the antenna to resonate at the desired frequency weuse the following two equations in parameters optimization
120582 =
119888
radic120576eff119891 (1)
with
120576eff =120576119903+ 1
2
(2)
In Figure 2 both elements are excited and when 119882119892=
02mm the resonant frequency is 245GHz and the length
International Journal of Antennas and Propagation 3
Wg = 01mmWg = 02mmWg = 03mm
Wg = 04mmWg = 05mm
0
minus5
minus10
minus15
minus20
minus2520 22 24 26 28 30
Frequency (GHz)
S 11
(dB)
(a)
0
minus5
minus10
minus15
minus20
minus2520 22 24 26 28 30
Frequency (GHz)
S 11
(dB)
Wf = 02mmWf = 03mm
Wf = 04mmWf = 05mm
(b)
0
minus5
minus10
minus15
minus20
minus2520 22 24 26 28 30
Frequency (GHz)
S 11
(dB)
Wn = 01mmWn = 02mm
Wn = 03mmWn = 04mm
(c)
Figure 3 Simulated reflection coefficients as a function of (a)119882119892 (b)119882
119891 and (c)119882
119899
of the surface current path (the dot line in Figure 2) at thisfrequency is 186mm which is one-quarter of the wavelengthcalculated by (1) When 119882
119892= 04mm the resonant
frequency shifts to 253GHz and the length of the surfacecurrent path changed to 180mm which is just one-fourth ofthe wavelength at this frequency The changes of119882
119899and119882
119891
have similar effect on the antenna resonance Figure 3 showsthe relationship between the width of 119882
119892 119882119899 and 119882
119891and
the reflection coefficientsFigure 4 is the surface current when only element number
1 is excited at 245GHz Because of the high isolation betweenantenna elements little coupling current is on the otherelement Compared to the current rotation in Figure 2 thedirection of the coupling current on element number 2 in
Figure 4 is opposite with the excited current on elementnumber 2 in Figure 2
Two types of dual-element antenna arrays are demon-strated in Figures 5(a) and 6(a) The two elements are nolonger symmetrical but are in the same direction For TypeI the edge-to-edge separation of the ground is the same withthe proposed one considering the shape of the radiationpatch the distance between the two elements is decreased andthe isolation deteriorated shown in Figure 5(b)
For Type II the space between the two radiation patchesis kept the same with the proposed one the actual dis-tance between the antenna elements is increased but theisolation is still lower than the proposed MIMO antenna
4 International Journal of Antennas and Propagation
200
150
100
50
0
J(A
m)
Figure 4 Surface current distribution when only one element isexcited at 245GHz
system So the isolation is affected not only by the dis-tance between elements but also by the rotation of thecurrents on the radiation patch Due to the well knownskin effect the two elements can be seen acting like twoloop antennas at the operating band So when only oneantenna is excited the coupled current on the other elementhas the same rotation or polarization with the exited one(Figure 4) while two elements are excited simultaneouslythe rotation or the polarization is just opposite (Figure 2)this to some extent reduced the coupling between theelements
The two antenna elements can also be orthogonallyplaced as shown in Figure 7(a) Compared to the proposedMIMO antenna system the isolation is 1-2 dB higher dueto the arrangement of the antenna element However thesize of the total system is larger than the proposed one Sothe final choice is a compromise between space and systemperformance
3 Results and Discussion
31 Measured Results Figure 8 shows the photograph of thefabricated antenna The antenna elements are fed by 50ΩMCX connectors [18]
The simulated and measured 119878 parameters of the MIMOantenna system are shown in Figure 9 The simulated resultswere achieved by Ansoft HFSS version 15 while the mea-sured results were obtained by using Agilent 85058E vectornetwork analyzer The simulated bandwidth was 320MHz(226ndash258GHz) the simulated 119878
11curve coincides with
the simulated 11987822
curve and the measured bandwidth was310MHz (220ndash251 GHz) The difference between them wasprobably due to the fabricated imperfections and the lossof the feeding cable and connectors The measured minus10 dBimpedance bandwidth can cover the desired LTE 2300 and245GHz ISM band
Lm
Size 18mm times 155mm(a)
0
minus5
minus10
minus15
minus20
minus25
Spa
ram
eter
s (dB
)
20 22 24 26 28
Frequency (GHz)
S11S22
S12(S21)S21 prototype
(b)
Figure 5 (a) MIMO antenna system Type I (b) 119878 parameters ofType I
Figure 10 shows the isolation between antenna elementsThrough the whole operating band the isolation is higherthan 16 dB
The correlation coefficient (120588) is an important parameterto evaluate the diversity performance of the multiantennasystems The lower 120588 results in better MIMO system perfor-mance It is usually calculated from 3D radiation patternsHowever this procedure is rather complicate recent researchindicates that the correlation coefficient can be easily derivedfrom the 119878-parameters [19] with the following expression
10038161003816100381610038161003816120588119894119895
10038161003816100381610038161003816=
10038161003816100381610038161003816119878119894119894
lowast119878119894119895+ 119878119894119895
lowast119878119895119895
10038161003816100381610038161003816
radic10038161003816100381610038161003816(1 minus1003816100381610038161003816119878119894119894
21003816100381610038161003816minus
10038161003816100381610038161003816119878119895119894
210038161003816100381610038161003816) (1 minus
10038161003816100381610038161003816119878119895119895
210038161003816100381610038161003816minus
10038161003816100381610038161003816119878119894119895
210038161003816100381610038161003816) 120578119894120578119895
10038161003816100381610038161003816
(3)
International Journal of Antennas and Propagation 5
Lg
Size 216mm times 155mm
(a)
0
minus5
minus10
minus15
minus20
minus2520 22 24 26 28
Frequency (GHz)
Spa
ram
eter
s (dB
)
S11S22
S12(S21)S21 prototype
(b)
Figure 6 (a) MIMO antenna system Type II (b) 119878 parameters of Type II
78mm
Size 315mm times 155mm
(a)
0
minus5
minus10
minus15
minus25
minus35
minus20
minus30
20 22 24 26 28
Frequency (GHz)
Spa
ram
eter
s (dB
)
S11S22
S12(S21)S21 prototype
(b)
Figure 7 (a) Orthogonally arranged MIMO antenna system (b) 119878 parameters
Figure 11 shows the correlation coefficient between theantenna elements of the proposed MIMO antenna systemThe antenna efficiency was higher than 78 through theworking band The results are well below 03 which is themaximum value set for 4G standards [20]
The gain of the proposedMIMOantenna system is shownin Figure 12 The simulated peak gain in the +119911 direction is072 dBi at 241 GHz and the measured peak gain is 062 dBiat 24GHz
The radiation pattern of the proposed MIMO antennasystem is shown in Figure 13 The radiation pattern wasobtained when one element was excited and the other is
terminated with a 50 ohm load The radiation pattern is justlike a monopole which has an omnidirectional radiation inthe119867 plane at the resonant frequency
32 Eight-Element MIMO Systems According to [21] theincrease of the number of transmitter antennas and receiverantennas can improve the communication quality andincrease the channel capacity without extra radiation powerand spectrum bandwidth An eight-element MIMO antennasystem was also fabricated and measured Its measured
6 International Journal of Antennas and Propagation
Figure 8 Photograph of the fabricated MIMO antenna system
0
minus5
minus10
minus15
minus20
minus30
minus25
20 22 24 26 28
Frequency (GHz)
Spa
ram
eter
s (dB
)
S11 simulatedS22 simulated
S11 measurementS22 measurement
Figure 9 Simulated and measured 119878 parameters of the proposedMIMO antenna system
minus10 dB bandwidth is 340MHz (218ndash252GHz) as shownin Figure 14(a) good agreement is realized for the sake ofclarity we only put the results of four antennas here Themeasured isolation between antennas is lower than minus15 dB atthe whole operating band The simulated radiation efficiencyof the antenna element is higher than 77 over the wholeband The correlation coefficient can be calculated by using(3) As plotted in Figure 14(d) the value is far smaller than03
33 Practical Applications For practical applications MIMOantenna system is integrated with other components suchas circuit board and LCD screen which means that aconductive plane under the system should be taken intoconsideration
In Figure 15(a) the MIMO antenna system was placedabove a metal sheet separated by free space The separationbetween the conductive board and antenna bottom sidewas varied from 1 to 5mm in 1-mm steps Figures 15(b)and 15(c) show the reflection coefficients and the isolationcharacteristics of the antenna element over a metal sheet atdifferent distances
minus15
minus20
minus2520 22 24 26 28
Frequency (GHz)
Isol
atio
n (d
B)
S12(S21) simulatedS12(S21) measurement
Figure 10 Isolation of MIMO antenna system
Frequency (GHz)
0016
0014
0012
0010
0008
0006
0004
0002
000020 22 24 26 28 30
Antenna 1 and antenna 2
Cor
relat
ion
coeffi
cien
t
Figure 11 Correlation coefficient curve for the proposed MIMOantenna system
Frequency (GHz)
SimulationMeasurement
10
05
00
minus05
minus10
minus15
minus20
minus25
Gai
n (d
Bi)
21 22 23 24 25 26
Figure 12 Gain of MIMO antenna system
International Journal of Antennas and Propagation 7
0
minus10
minus20
minus30
minus40
minus30
minus20
minus10
0
0
30
60
90
120
150
180
210
240
270
300
330
245GHz-Phi-simulation245GHz-Theta-simulation245GHz-Phi-measurement245GHz-Theta-measurement
XZ
(a)
0
minus10
minus20
minus30
minus20
minus10
0
0
30
60
90
120
150
180
210
240
270
300
330
245GHz-Phi-simulation245GHz-Theta-simulation245GHz-Phi-measurement245GHz-Theta-measurement
YZ
(b)
0
minus10
minus20
minus30
minus20
minus10
0
0
30
60
90
120
150
180
210
240
270
300
330
245GHz-Phi-simulation245GHz-Theta-simulation245GHz-Phi-measurement245GHz-Theta-measurement
XY
(c)
Figure 13 Radiation pattern of the proposed MIMO antenna at 245GHz (a) 119909119911-plane (b) 119910119911-plane and (c) 119909119910-plane
It was found that by using a metal sheet the resonantfrequency of the individual antenna element shifted Asthe distance between the antenna and conductive planeincreased the effect weakens When the board is closelyplaced under the system like 1mm the resonant frequencychanged most but the working band can still cover theLTE2300 and 245GHz ISM band This is unlike the systemreported in [22] the antenna system does not have any
special designed structures on the back side of the sub-strate so it is not obligatory to place the system carefullysuch that its bottom side maintains a minimum distancelike 3 to 5mm from any conductive plane for practicaldesign
Figure 16(a) shows a 1mm thick plastic housing which isused to simulate the practical case of thewireless terminals Insimulation the relative permittivity of the plastic housing is
8 International Journal of Antennas and Propagation
340
95
78
54
46
95
55
580
150
215
55
215
40
09
20
40
30
18
02
020418
06
10
33
xy
z
05
➃➄➅➆
➀➇
➁➂
(a)
20 22 24 26 28
Frequency (GHz)
minus10
minus5
0
minus15
minus20
minus25
minus30
minus35
Spa
ram
eter
s (dB
)
S11 simulationS22 simulationS33 simulationS44 simulation
S11 measurementS22 measurementS33 measurementS44 measurement
(b)
Isol
atio
n (d
B)
20 22 24 26 28
Frequency (GHz)
S12S13S14
S16S17S18
S15
minus10
minus15
minus20
minus25
minus30
minus35
minus40
minus45
minus50
(c)
0024
0020
0016
0012
0008
0004
0000
Cor
relat
ion
coeffi
cien
t
20 22 24 26 28 30
Frequency (GHz)
Antennas 1 and 2
Antennas 1 and 3
Antennas 1 and 4
Antennas 1 and 5
Antennas 1 and 6Antennas 1 and 7Antennas 1 and 8
(d)
Figure 14 (a) Geometry of the 8-element MIMO antenna system (b) Reflection coefficients of the MIMO antenna system (c) Measuredisolation between MIMO antenna elements (d) Correlation coefficient |120588| curves for the proposed MIMO antenna system
set as 33 and the loss tangent is 002 the same as [23] Figures16(b) and 16(c) show the influence of the plastic housing onreflection coefficients and isolation Differences between thetwo cases are small and acceptable and show this MIMOsystem is competitive for practical application
4 Conclusion
Symmetric planar monopole antenna for compact multiele-ment MIMO antenna systems is proposed Isolation higher
than 15 dB over the operating band is realized by using polar-ization diversity of the antenna elements Correlation coeffi-cient 119878-parameters radiation characteristics and acceptableperformance when placed with conductive plane and plastichousing show that the proposed antenna arrays can be usedfor practical MIMO applications
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
International Journal of Antennas and Propagation 9
Metal sheet(a)
20 22 24 26 28
Frequency (GHz)
minus10
minus5
0
minus15
minus20
minus25
minus30
minus35
Spa
ram
eter
s (dB
)
Without metal sheet1mm2mm
3mm4mm5mm
(b)
20 22 24 26 28
Frequency (GHz)
minus15
minus20
minus25
minus30
minus35
Isol
atio
n (d
B)
S12 and S211mm2mm
3mm4mm5mm
(c)
Figure 15 (a) Proposed MIMO antenna with a metal sheet sepa-rated by free space (b) Reflection coefficients of theMIMO antennasystemwith ametal sheet (c) Isolation of theMIMOantenna systemwith a metal sheet
Plastichousing
(a)
20 22 24 26 28
Frequency (GHz)
minus10
minus5
0
minus15
minus20
minus25
Spa
ram
eter
s (dB
)
S11 with plastic housingS11 without plastic housing
(b)
20 22 24 26 28
Frequency (GHz)
Isol
atio
n (d
B)
minus15
minus20
minus30
minus25
S12 and S21 with plastic housingS12 and S21 without plastic housing
(c)
Figure 16 (a) Proposed antenna with plastic housing (b) Reflectioncoefficients (c) Isolation
10 International Journal of Antennas and Propagation
Acknowledgment
This work was supported by the Priority Academic Pro-gram Development of Jiangsu Higher Education Institutions(PAPD)
References
[1] T Kokkinos E Liakou and A P Feresidis ldquoDecouplingantenna elements of PIFAarrays onhandheld devicesrdquoElectron-ics Letters vol 44 no 25 pp 1442ndash1444 2008
[2] H Li J Xiong Z Ying and S L He ldquoCompact and low profileco-locatedMIMO antenna structure with polarisation diversityand high port isolationrdquo Electronics Letters vol 46 no 2 pp108ndash110 2010
[3] S Zhang P Zetterberg and S He ldquoPrinted MIMO antennasystem of four closely-spaced elements with large bandwidthand high isolationrdquo Electronics Letters vol 46 no 15 pp 1052ndash1053 2010
[4] C Yang J Kim H Kim J Wee B Kim and C Jung ldquoQuad-band antenna with high isolation MIMO and broadbandSCS for broadcasting and telecommunication servicesrdquo IEEEAntennas and Wireless Propagation Letters vol 9 pp 584ndash5872010
[5] S Park and C Jung ldquoCompact MIMO antenna with highisolation performancerdquo Electronics Letters vol 46 no 6 pp390ndash391 2010
[6] H S Farahani M Veysi M Kamyab and A Tadjalli ldquoMutualcoupling reduction in patch antenna arrays using a UC-EBGsuperstraterdquo IEEE Antennas and Wireless Propagation Lettersvol 9 pp 57ndash59 2010
[7] G Exposito-Domınguez J M Fernandez-Gonzalez P Padillaand M Sierra-Castaner ldquoNew EBG solutions for mutual cou-pling reductionrdquo in Proceedings of the 6th European Conferenceon Antennas and Propagation (EUCAP rsquo12) pp 2841ndash2844IEEE Prague Czech Republic March 2012
[8] A Habashi J Nourinia and C Ghobadi ldquoA rectangulardefected ground structure (DGS) for reduction of mutualcoupling between closely-spaced microstrip antennasrdquo in Pro-ceedings of the 20th Iranian Conference on Electrical Engineering(ICEE rsquo12) pp 1347ndash1350 IEEE Tehran Iran May 2012
[9] L Wang and B Huang ldquoDesign of ultra-wideband MIMOantenna for breast tumor detectionrdquo International Journal ofAntennas and Propagation vol 2012 Article ID 180158 7 pages2012
[10] M Gallo E Antonino-Daviu M Ferrando-Bataller MBozzetti J M Molina-Garcia-Pardo and L Juan-Llacer ldquoAbroadband pattern diversity annular slot antennardquo IEEE Trans-actions on Antennas and Propagation vol 60 no 3 pp 1596ndash1600 2012
[11] D-G Kang J Tak and J Chio ldquoMIMO antenna with highisolation for WBAN applicationsrdquo International Journal ofAntennas and Propagation vol 2015 Article ID 370763 7 pages2015
[12] Y K Choukiker S K Sharma and S K Behera ldquoHybrid fractalshape planar monopole antenna covering multiband wirelesscommunications with MIMO implementation for handheldmobile devicesrdquo IEEE Transactions on Antennas and Propaga-tion vol 62 no 3 pp 1483ndash1488 2014
[13] Q Zeng Y Yao S Liu J Yu P Xie and X Chen ldquoTetrabandsmall-size printed strip MIMO antenna for mobile handset
applicationrdquo International Journal of Antennas and Propagationvol 2012 Article ID 320582 8 pages 2012
[14] KWang R AMMauermayer and T F Eibert ldquoCompact two-element printedmonopole arraywith partially extended groundplanerdquo IEEE Antennas and Wireless Propagation Letters vol 13pp 138ndash140 2014
[15] J Park J Choi J-Y Park and Y-S Kim ldquoStudy of a T-shaped slot with a capacitor for high isolation between MIMOantennasrdquo IEEE Antennas andWireless Propagation Letters vol11 pp 1541ndash1544 2012
[16] M G N Alsath M Kanagasabai and B BalasubramanianldquoImplementation of slotted meander-line resonators for isola-tion enhancement in microstrip patch antenna arraysrdquo IEEEAntennas and Wireless Propagation Letters vol 12 pp 15ndash182013
[17] H Arun A K Sarma M Kanagasabai S Velan C Ravitejaand M G N Alsath ldquoDeployment of modified serpentinestructure for mutual coupling reduction in MIMO antennasrdquoIEEEAntennas andWireless Propagation Letters vol 13 pp 277ndash280 2014
[18] httpsenwikipediaorgwikiMCX connector[19] S Blanch J Romeu and I Corbella ldquoExact representation of
antenna system diversity performance from input parameterdescriptionrdquo Electronics Letters vol 39 no 9 pp 705ndash707 2003
[20] 3GPP ldquoEUTRA user equipment radio transmission and recep-tionrdquo 3GPP TS 36101 V830 September 2008
[21] L Song and J Shen Evolved Cellular Network Planning andOptimization for UMTS and LTE CRCPress London UK 2011
[22] M S Sharawi M U Khan A B Numan and D N Aloi ldquoACSRR loaded MIMO antenna system for ISM band operationrdquoIEEE Transactions on Antennas and Propagation vol 61 no 8pp 4265ndash4274 2013
[23] Y-L Ban J-H Chen J L-W Li and Y J Wu ldquoSmall-sizeprinted coupled-fed antenna for eight-band LTEGSMUMTSwireless wide area network operation in an internal mobilehandsetrdquo IET Microwaves Antennas amp Propagation vol 7 no6 pp 399ndash407 2013
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
International Journal of Antennas and Propagation 3
Wg = 01mmWg = 02mmWg = 03mm
Wg = 04mmWg = 05mm
0
minus5
minus10
minus15
minus20
minus2520 22 24 26 28 30
Frequency (GHz)
S 11
(dB)
(a)
0
minus5
minus10
minus15
minus20
minus2520 22 24 26 28 30
Frequency (GHz)
S 11
(dB)
Wf = 02mmWf = 03mm
Wf = 04mmWf = 05mm
(b)
0
minus5
minus10
minus15
minus20
minus2520 22 24 26 28 30
Frequency (GHz)
S 11
(dB)
Wn = 01mmWn = 02mm
Wn = 03mmWn = 04mm
(c)
Figure 3 Simulated reflection coefficients as a function of (a)119882119892 (b)119882
119891 and (c)119882
119899
of the surface current path (the dot line in Figure 2) at thisfrequency is 186mm which is one-quarter of the wavelengthcalculated by (1) When 119882
119892= 04mm the resonant
frequency shifts to 253GHz and the length of the surfacecurrent path changed to 180mm which is just one-fourth ofthe wavelength at this frequency The changes of119882
119899and119882
119891
have similar effect on the antenna resonance Figure 3 showsthe relationship between the width of 119882
119892 119882119899 and 119882
119891and
the reflection coefficientsFigure 4 is the surface current when only element number
1 is excited at 245GHz Because of the high isolation betweenantenna elements little coupling current is on the otherelement Compared to the current rotation in Figure 2 thedirection of the coupling current on element number 2 in
Figure 4 is opposite with the excited current on elementnumber 2 in Figure 2
Two types of dual-element antenna arrays are demon-strated in Figures 5(a) and 6(a) The two elements are nolonger symmetrical but are in the same direction For TypeI the edge-to-edge separation of the ground is the same withthe proposed one considering the shape of the radiationpatch the distance between the two elements is decreased andthe isolation deteriorated shown in Figure 5(b)
For Type II the space between the two radiation patchesis kept the same with the proposed one the actual dis-tance between the antenna elements is increased but theisolation is still lower than the proposed MIMO antenna
4 International Journal of Antennas and Propagation
200
150
100
50
0
J(A
m)
Figure 4 Surface current distribution when only one element isexcited at 245GHz
system So the isolation is affected not only by the dis-tance between elements but also by the rotation of thecurrents on the radiation patch Due to the well knownskin effect the two elements can be seen acting like twoloop antennas at the operating band So when only oneantenna is excited the coupled current on the other elementhas the same rotation or polarization with the exited one(Figure 4) while two elements are excited simultaneouslythe rotation or the polarization is just opposite (Figure 2)this to some extent reduced the coupling between theelements
The two antenna elements can also be orthogonallyplaced as shown in Figure 7(a) Compared to the proposedMIMO antenna system the isolation is 1-2 dB higher dueto the arrangement of the antenna element However thesize of the total system is larger than the proposed one Sothe final choice is a compromise between space and systemperformance
3 Results and Discussion
31 Measured Results Figure 8 shows the photograph of thefabricated antenna The antenna elements are fed by 50ΩMCX connectors [18]
The simulated and measured 119878 parameters of the MIMOantenna system are shown in Figure 9 The simulated resultswere achieved by Ansoft HFSS version 15 while the mea-sured results were obtained by using Agilent 85058E vectornetwork analyzer The simulated bandwidth was 320MHz(226ndash258GHz) the simulated 119878
11curve coincides with
the simulated 11987822
curve and the measured bandwidth was310MHz (220ndash251 GHz) The difference between them wasprobably due to the fabricated imperfections and the lossof the feeding cable and connectors The measured minus10 dBimpedance bandwidth can cover the desired LTE 2300 and245GHz ISM band
Lm
Size 18mm times 155mm(a)
0
minus5
minus10
minus15
minus20
minus25
Spa
ram
eter
s (dB
)
20 22 24 26 28
Frequency (GHz)
S11S22
S12(S21)S21 prototype
(b)
Figure 5 (a) MIMO antenna system Type I (b) 119878 parameters ofType I
Figure 10 shows the isolation between antenna elementsThrough the whole operating band the isolation is higherthan 16 dB
The correlation coefficient (120588) is an important parameterto evaluate the diversity performance of the multiantennasystems The lower 120588 results in better MIMO system perfor-mance It is usually calculated from 3D radiation patternsHowever this procedure is rather complicate recent researchindicates that the correlation coefficient can be easily derivedfrom the 119878-parameters [19] with the following expression
10038161003816100381610038161003816120588119894119895
10038161003816100381610038161003816=
10038161003816100381610038161003816119878119894119894
lowast119878119894119895+ 119878119894119895
lowast119878119895119895
10038161003816100381610038161003816
radic10038161003816100381610038161003816(1 minus1003816100381610038161003816119878119894119894
21003816100381610038161003816minus
10038161003816100381610038161003816119878119895119894
210038161003816100381610038161003816) (1 minus
10038161003816100381610038161003816119878119895119895
210038161003816100381610038161003816minus
10038161003816100381610038161003816119878119894119895
210038161003816100381610038161003816) 120578119894120578119895
10038161003816100381610038161003816
(3)
International Journal of Antennas and Propagation 5
Lg
Size 216mm times 155mm
(a)
0
minus5
minus10
minus15
minus20
minus2520 22 24 26 28
Frequency (GHz)
Spa
ram
eter
s (dB
)
S11S22
S12(S21)S21 prototype
(b)
Figure 6 (a) MIMO antenna system Type II (b) 119878 parameters of Type II
78mm
Size 315mm times 155mm
(a)
0
minus5
minus10
minus15
minus25
minus35
minus20
minus30
20 22 24 26 28
Frequency (GHz)
Spa
ram
eter
s (dB
)
S11S22
S12(S21)S21 prototype
(b)
Figure 7 (a) Orthogonally arranged MIMO antenna system (b) 119878 parameters
Figure 11 shows the correlation coefficient between theantenna elements of the proposed MIMO antenna systemThe antenna efficiency was higher than 78 through theworking band The results are well below 03 which is themaximum value set for 4G standards [20]
The gain of the proposedMIMOantenna system is shownin Figure 12 The simulated peak gain in the +119911 direction is072 dBi at 241 GHz and the measured peak gain is 062 dBiat 24GHz
The radiation pattern of the proposed MIMO antennasystem is shown in Figure 13 The radiation pattern wasobtained when one element was excited and the other is
terminated with a 50 ohm load The radiation pattern is justlike a monopole which has an omnidirectional radiation inthe119867 plane at the resonant frequency
32 Eight-Element MIMO Systems According to [21] theincrease of the number of transmitter antennas and receiverantennas can improve the communication quality andincrease the channel capacity without extra radiation powerand spectrum bandwidth An eight-element MIMO antennasystem was also fabricated and measured Its measured
6 International Journal of Antennas and Propagation
Figure 8 Photograph of the fabricated MIMO antenna system
0
minus5
minus10
minus15
minus20
minus30
minus25
20 22 24 26 28
Frequency (GHz)
Spa
ram
eter
s (dB
)
S11 simulatedS22 simulated
S11 measurementS22 measurement
Figure 9 Simulated and measured 119878 parameters of the proposedMIMO antenna system
minus10 dB bandwidth is 340MHz (218ndash252GHz) as shownin Figure 14(a) good agreement is realized for the sake ofclarity we only put the results of four antennas here Themeasured isolation between antennas is lower than minus15 dB atthe whole operating band The simulated radiation efficiencyof the antenna element is higher than 77 over the wholeband The correlation coefficient can be calculated by using(3) As plotted in Figure 14(d) the value is far smaller than03
33 Practical Applications For practical applications MIMOantenna system is integrated with other components suchas circuit board and LCD screen which means that aconductive plane under the system should be taken intoconsideration
In Figure 15(a) the MIMO antenna system was placedabove a metal sheet separated by free space The separationbetween the conductive board and antenna bottom sidewas varied from 1 to 5mm in 1-mm steps Figures 15(b)and 15(c) show the reflection coefficients and the isolationcharacteristics of the antenna element over a metal sheet atdifferent distances
minus15
minus20
minus2520 22 24 26 28
Frequency (GHz)
Isol
atio
n (d
B)
S12(S21) simulatedS12(S21) measurement
Figure 10 Isolation of MIMO antenna system
Frequency (GHz)
0016
0014
0012
0010
0008
0006
0004
0002
000020 22 24 26 28 30
Antenna 1 and antenna 2
Cor
relat
ion
coeffi
cien
t
Figure 11 Correlation coefficient curve for the proposed MIMOantenna system
Frequency (GHz)
SimulationMeasurement
10
05
00
minus05
minus10
minus15
minus20
minus25
Gai
n (d
Bi)
21 22 23 24 25 26
Figure 12 Gain of MIMO antenna system
International Journal of Antennas and Propagation 7
0
minus10
minus20
minus30
minus40
minus30
minus20
minus10
0
0
30
60
90
120
150
180
210
240
270
300
330
245GHz-Phi-simulation245GHz-Theta-simulation245GHz-Phi-measurement245GHz-Theta-measurement
XZ
(a)
0
minus10
minus20
minus30
minus20
minus10
0
0
30
60
90
120
150
180
210
240
270
300
330
245GHz-Phi-simulation245GHz-Theta-simulation245GHz-Phi-measurement245GHz-Theta-measurement
YZ
(b)
0
minus10
minus20
minus30
minus20
minus10
0
0
30
60
90
120
150
180
210
240
270
300
330
245GHz-Phi-simulation245GHz-Theta-simulation245GHz-Phi-measurement245GHz-Theta-measurement
XY
(c)
Figure 13 Radiation pattern of the proposed MIMO antenna at 245GHz (a) 119909119911-plane (b) 119910119911-plane and (c) 119909119910-plane
It was found that by using a metal sheet the resonantfrequency of the individual antenna element shifted Asthe distance between the antenna and conductive planeincreased the effect weakens When the board is closelyplaced under the system like 1mm the resonant frequencychanged most but the working band can still cover theLTE2300 and 245GHz ISM band This is unlike the systemreported in [22] the antenna system does not have any
special designed structures on the back side of the sub-strate so it is not obligatory to place the system carefullysuch that its bottom side maintains a minimum distancelike 3 to 5mm from any conductive plane for practicaldesign
Figure 16(a) shows a 1mm thick plastic housing which isused to simulate the practical case of thewireless terminals Insimulation the relative permittivity of the plastic housing is
8 International Journal of Antennas and Propagation
340
95
78
54
46
95
55
580
150
215
55
215
40
09
20
40
30
18
02
020418
06
10
33
xy
z
05
➃➄➅➆
➀➇
➁➂
(a)
20 22 24 26 28
Frequency (GHz)
minus10
minus5
0
minus15
minus20
minus25
minus30
minus35
Spa
ram
eter
s (dB
)
S11 simulationS22 simulationS33 simulationS44 simulation
S11 measurementS22 measurementS33 measurementS44 measurement
(b)
Isol
atio
n (d
B)
20 22 24 26 28
Frequency (GHz)
S12S13S14
S16S17S18
S15
minus10
minus15
minus20
minus25
minus30
minus35
minus40
minus45
minus50
(c)
0024
0020
0016
0012
0008
0004
0000
Cor
relat
ion
coeffi
cien
t
20 22 24 26 28 30
Frequency (GHz)
Antennas 1 and 2
Antennas 1 and 3
Antennas 1 and 4
Antennas 1 and 5
Antennas 1 and 6Antennas 1 and 7Antennas 1 and 8
(d)
Figure 14 (a) Geometry of the 8-element MIMO antenna system (b) Reflection coefficients of the MIMO antenna system (c) Measuredisolation between MIMO antenna elements (d) Correlation coefficient |120588| curves for the proposed MIMO antenna system
set as 33 and the loss tangent is 002 the same as [23] Figures16(b) and 16(c) show the influence of the plastic housing onreflection coefficients and isolation Differences between thetwo cases are small and acceptable and show this MIMOsystem is competitive for practical application
4 Conclusion
Symmetric planar monopole antenna for compact multiele-ment MIMO antenna systems is proposed Isolation higher
than 15 dB over the operating band is realized by using polar-ization diversity of the antenna elements Correlation coeffi-cient 119878-parameters radiation characteristics and acceptableperformance when placed with conductive plane and plastichousing show that the proposed antenna arrays can be usedfor practical MIMO applications
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
International Journal of Antennas and Propagation 9
Metal sheet(a)
20 22 24 26 28
Frequency (GHz)
minus10
minus5
0
minus15
minus20
minus25
minus30
minus35
Spa
ram
eter
s (dB
)
Without metal sheet1mm2mm
3mm4mm5mm
(b)
20 22 24 26 28
Frequency (GHz)
minus15
minus20
minus25
minus30
minus35
Isol
atio
n (d
B)
S12 and S211mm2mm
3mm4mm5mm
(c)
Figure 15 (a) Proposed MIMO antenna with a metal sheet sepa-rated by free space (b) Reflection coefficients of theMIMO antennasystemwith ametal sheet (c) Isolation of theMIMOantenna systemwith a metal sheet
Plastichousing
(a)
20 22 24 26 28
Frequency (GHz)
minus10
minus5
0
minus15
minus20
minus25
Spa
ram
eter
s (dB
)
S11 with plastic housingS11 without plastic housing
(b)
20 22 24 26 28
Frequency (GHz)
Isol
atio
n (d
B)
minus15
minus20
minus30
minus25
S12 and S21 with plastic housingS12 and S21 without plastic housing
(c)
Figure 16 (a) Proposed antenna with plastic housing (b) Reflectioncoefficients (c) Isolation
10 International Journal of Antennas and Propagation
Acknowledgment
This work was supported by the Priority Academic Pro-gram Development of Jiangsu Higher Education Institutions(PAPD)
References
[1] T Kokkinos E Liakou and A P Feresidis ldquoDecouplingantenna elements of PIFAarrays onhandheld devicesrdquoElectron-ics Letters vol 44 no 25 pp 1442ndash1444 2008
[2] H Li J Xiong Z Ying and S L He ldquoCompact and low profileco-locatedMIMO antenna structure with polarisation diversityand high port isolationrdquo Electronics Letters vol 46 no 2 pp108ndash110 2010
[3] S Zhang P Zetterberg and S He ldquoPrinted MIMO antennasystem of four closely-spaced elements with large bandwidthand high isolationrdquo Electronics Letters vol 46 no 15 pp 1052ndash1053 2010
[4] C Yang J Kim H Kim J Wee B Kim and C Jung ldquoQuad-band antenna with high isolation MIMO and broadbandSCS for broadcasting and telecommunication servicesrdquo IEEEAntennas and Wireless Propagation Letters vol 9 pp 584ndash5872010
[5] S Park and C Jung ldquoCompact MIMO antenna with highisolation performancerdquo Electronics Letters vol 46 no 6 pp390ndash391 2010
[6] H S Farahani M Veysi M Kamyab and A Tadjalli ldquoMutualcoupling reduction in patch antenna arrays using a UC-EBGsuperstraterdquo IEEE Antennas and Wireless Propagation Lettersvol 9 pp 57ndash59 2010
[7] G Exposito-Domınguez J M Fernandez-Gonzalez P Padillaand M Sierra-Castaner ldquoNew EBG solutions for mutual cou-pling reductionrdquo in Proceedings of the 6th European Conferenceon Antennas and Propagation (EUCAP rsquo12) pp 2841ndash2844IEEE Prague Czech Republic March 2012
[8] A Habashi J Nourinia and C Ghobadi ldquoA rectangulardefected ground structure (DGS) for reduction of mutualcoupling between closely-spaced microstrip antennasrdquo in Pro-ceedings of the 20th Iranian Conference on Electrical Engineering(ICEE rsquo12) pp 1347ndash1350 IEEE Tehran Iran May 2012
[9] L Wang and B Huang ldquoDesign of ultra-wideband MIMOantenna for breast tumor detectionrdquo International Journal ofAntennas and Propagation vol 2012 Article ID 180158 7 pages2012
[10] M Gallo E Antonino-Daviu M Ferrando-Bataller MBozzetti J M Molina-Garcia-Pardo and L Juan-Llacer ldquoAbroadband pattern diversity annular slot antennardquo IEEE Trans-actions on Antennas and Propagation vol 60 no 3 pp 1596ndash1600 2012
[11] D-G Kang J Tak and J Chio ldquoMIMO antenna with highisolation for WBAN applicationsrdquo International Journal ofAntennas and Propagation vol 2015 Article ID 370763 7 pages2015
[12] Y K Choukiker S K Sharma and S K Behera ldquoHybrid fractalshape planar monopole antenna covering multiband wirelesscommunications with MIMO implementation for handheldmobile devicesrdquo IEEE Transactions on Antennas and Propaga-tion vol 62 no 3 pp 1483ndash1488 2014
[13] Q Zeng Y Yao S Liu J Yu P Xie and X Chen ldquoTetrabandsmall-size printed strip MIMO antenna for mobile handset
applicationrdquo International Journal of Antennas and Propagationvol 2012 Article ID 320582 8 pages 2012
[14] KWang R AMMauermayer and T F Eibert ldquoCompact two-element printedmonopole arraywith partially extended groundplanerdquo IEEE Antennas and Wireless Propagation Letters vol 13pp 138ndash140 2014
[15] J Park J Choi J-Y Park and Y-S Kim ldquoStudy of a T-shaped slot with a capacitor for high isolation between MIMOantennasrdquo IEEE Antennas andWireless Propagation Letters vol11 pp 1541ndash1544 2012
[16] M G N Alsath M Kanagasabai and B BalasubramanianldquoImplementation of slotted meander-line resonators for isola-tion enhancement in microstrip patch antenna arraysrdquo IEEEAntennas and Wireless Propagation Letters vol 12 pp 15ndash182013
[17] H Arun A K Sarma M Kanagasabai S Velan C Ravitejaand M G N Alsath ldquoDeployment of modified serpentinestructure for mutual coupling reduction in MIMO antennasrdquoIEEEAntennas andWireless Propagation Letters vol 13 pp 277ndash280 2014
[18] httpsenwikipediaorgwikiMCX connector[19] S Blanch J Romeu and I Corbella ldquoExact representation of
antenna system diversity performance from input parameterdescriptionrdquo Electronics Letters vol 39 no 9 pp 705ndash707 2003
[20] 3GPP ldquoEUTRA user equipment radio transmission and recep-tionrdquo 3GPP TS 36101 V830 September 2008
[21] L Song and J Shen Evolved Cellular Network Planning andOptimization for UMTS and LTE CRCPress London UK 2011
[22] M S Sharawi M U Khan A B Numan and D N Aloi ldquoACSRR loaded MIMO antenna system for ISM band operationrdquoIEEE Transactions on Antennas and Propagation vol 61 no 8pp 4265ndash4274 2013
[23] Y-L Ban J-H Chen J L-W Li and Y J Wu ldquoSmall-sizeprinted coupled-fed antenna for eight-band LTEGSMUMTSwireless wide area network operation in an internal mobilehandsetrdquo IET Microwaves Antennas amp Propagation vol 7 no6 pp 399ndash407 2013
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
4 International Journal of Antennas and Propagation
200
150
100
50
0
J(A
m)
Figure 4 Surface current distribution when only one element isexcited at 245GHz
system So the isolation is affected not only by the dis-tance between elements but also by the rotation of thecurrents on the radiation patch Due to the well knownskin effect the two elements can be seen acting like twoloop antennas at the operating band So when only oneantenna is excited the coupled current on the other elementhas the same rotation or polarization with the exited one(Figure 4) while two elements are excited simultaneouslythe rotation or the polarization is just opposite (Figure 2)this to some extent reduced the coupling between theelements
The two antenna elements can also be orthogonallyplaced as shown in Figure 7(a) Compared to the proposedMIMO antenna system the isolation is 1-2 dB higher dueto the arrangement of the antenna element However thesize of the total system is larger than the proposed one Sothe final choice is a compromise between space and systemperformance
3 Results and Discussion
31 Measured Results Figure 8 shows the photograph of thefabricated antenna The antenna elements are fed by 50ΩMCX connectors [18]
The simulated and measured 119878 parameters of the MIMOantenna system are shown in Figure 9 The simulated resultswere achieved by Ansoft HFSS version 15 while the mea-sured results were obtained by using Agilent 85058E vectornetwork analyzer The simulated bandwidth was 320MHz(226ndash258GHz) the simulated 119878
11curve coincides with
the simulated 11987822
curve and the measured bandwidth was310MHz (220ndash251 GHz) The difference between them wasprobably due to the fabricated imperfections and the lossof the feeding cable and connectors The measured minus10 dBimpedance bandwidth can cover the desired LTE 2300 and245GHz ISM band
Lm
Size 18mm times 155mm(a)
0
minus5
minus10
minus15
minus20
minus25
Spa
ram
eter
s (dB
)
20 22 24 26 28
Frequency (GHz)
S11S22
S12(S21)S21 prototype
(b)
Figure 5 (a) MIMO antenna system Type I (b) 119878 parameters ofType I
Figure 10 shows the isolation between antenna elementsThrough the whole operating band the isolation is higherthan 16 dB
The correlation coefficient (120588) is an important parameterto evaluate the diversity performance of the multiantennasystems The lower 120588 results in better MIMO system perfor-mance It is usually calculated from 3D radiation patternsHowever this procedure is rather complicate recent researchindicates that the correlation coefficient can be easily derivedfrom the 119878-parameters [19] with the following expression
10038161003816100381610038161003816120588119894119895
10038161003816100381610038161003816=
10038161003816100381610038161003816119878119894119894
lowast119878119894119895+ 119878119894119895
lowast119878119895119895
10038161003816100381610038161003816
radic10038161003816100381610038161003816(1 minus1003816100381610038161003816119878119894119894
21003816100381610038161003816minus
10038161003816100381610038161003816119878119895119894
210038161003816100381610038161003816) (1 minus
10038161003816100381610038161003816119878119895119895
210038161003816100381610038161003816minus
10038161003816100381610038161003816119878119894119895
210038161003816100381610038161003816) 120578119894120578119895
10038161003816100381610038161003816
(3)
International Journal of Antennas and Propagation 5
Lg
Size 216mm times 155mm
(a)
0
minus5
minus10
minus15
minus20
minus2520 22 24 26 28
Frequency (GHz)
Spa
ram
eter
s (dB
)
S11S22
S12(S21)S21 prototype
(b)
Figure 6 (a) MIMO antenna system Type II (b) 119878 parameters of Type II
78mm
Size 315mm times 155mm
(a)
0
minus5
minus10
minus15
minus25
minus35
minus20
minus30
20 22 24 26 28
Frequency (GHz)
Spa
ram
eter
s (dB
)
S11S22
S12(S21)S21 prototype
(b)
Figure 7 (a) Orthogonally arranged MIMO antenna system (b) 119878 parameters
Figure 11 shows the correlation coefficient between theantenna elements of the proposed MIMO antenna systemThe antenna efficiency was higher than 78 through theworking band The results are well below 03 which is themaximum value set for 4G standards [20]
The gain of the proposedMIMOantenna system is shownin Figure 12 The simulated peak gain in the +119911 direction is072 dBi at 241 GHz and the measured peak gain is 062 dBiat 24GHz
The radiation pattern of the proposed MIMO antennasystem is shown in Figure 13 The radiation pattern wasobtained when one element was excited and the other is
terminated with a 50 ohm load The radiation pattern is justlike a monopole which has an omnidirectional radiation inthe119867 plane at the resonant frequency
32 Eight-Element MIMO Systems According to [21] theincrease of the number of transmitter antennas and receiverantennas can improve the communication quality andincrease the channel capacity without extra radiation powerand spectrum bandwidth An eight-element MIMO antennasystem was also fabricated and measured Its measured
6 International Journal of Antennas and Propagation
Figure 8 Photograph of the fabricated MIMO antenna system
0
minus5
minus10
minus15
minus20
minus30
minus25
20 22 24 26 28
Frequency (GHz)
Spa
ram
eter
s (dB
)
S11 simulatedS22 simulated
S11 measurementS22 measurement
Figure 9 Simulated and measured 119878 parameters of the proposedMIMO antenna system
minus10 dB bandwidth is 340MHz (218ndash252GHz) as shownin Figure 14(a) good agreement is realized for the sake ofclarity we only put the results of four antennas here Themeasured isolation between antennas is lower than minus15 dB atthe whole operating band The simulated radiation efficiencyof the antenna element is higher than 77 over the wholeband The correlation coefficient can be calculated by using(3) As plotted in Figure 14(d) the value is far smaller than03
33 Practical Applications For practical applications MIMOantenna system is integrated with other components suchas circuit board and LCD screen which means that aconductive plane under the system should be taken intoconsideration
In Figure 15(a) the MIMO antenna system was placedabove a metal sheet separated by free space The separationbetween the conductive board and antenna bottom sidewas varied from 1 to 5mm in 1-mm steps Figures 15(b)and 15(c) show the reflection coefficients and the isolationcharacteristics of the antenna element over a metal sheet atdifferent distances
minus15
minus20
minus2520 22 24 26 28
Frequency (GHz)
Isol
atio
n (d
B)
S12(S21) simulatedS12(S21) measurement
Figure 10 Isolation of MIMO antenna system
Frequency (GHz)
0016
0014
0012
0010
0008
0006
0004
0002
000020 22 24 26 28 30
Antenna 1 and antenna 2
Cor
relat
ion
coeffi
cien
t
Figure 11 Correlation coefficient curve for the proposed MIMOantenna system
Frequency (GHz)
SimulationMeasurement
10
05
00
minus05
minus10
minus15
minus20
minus25
Gai
n (d
Bi)
21 22 23 24 25 26
Figure 12 Gain of MIMO antenna system
International Journal of Antennas and Propagation 7
0
minus10
minus20
minus30
minus40
minus30
minus20
minus10
0
0
30
60
90
120
150
180
210
240
270
300
330
245GHz-Phi-simulation245GHz-Theta-simulation245GHz-Phi-measurement245GHz-Theta-measurement
XZ
(a)
0
minus10
minus20
minus30
minus20
minus10
0
0
30
60
90
120
150
180
210
240
270
300
330
245GHz-Phi-simulation245GHz-Theta-simulation245GHz-Phi-measurement245GHz-Theta-measurement
YZ
(b)
0
minus10
minus20
minus30
minus20
minus10
0
0
30
60
90
120
150
180
210
240
270
300
330
245GHz-Phi-simulation245GHz-Theta-simulation245GHz-Phi-measurement245GHz-Theta-measurement
XY
(c)
Figure 13 Radiation pattern of the proposed MIMO antenna at 245GHz (a) 119909119911-plane (b) 119910119911-plane and (c) 119909119910-plane
It was found that by using a metal sheet the resonantfrequency of the individual antenna element shifted Asthe distance between the antenna and conductive planeincreased the effect weakens When the board is closelyplaced under the system like 1mm the resonant frequencychanged most but the working band can still cover theLTE2300 and 245GHz ISM band This is unlike the systemreported in [22] the antenna system does not have any
special designed structures on the back side of the sub-strate so it is not obligatory to place the system carefullysuch that its bottom side maintains a minimum distancelike 3 to 5mm from any conductive plane for practicaldesign
Figure 16(a) shows a 1mm thick plastic housing which isused to simulate the practical case of thewireless terminals Insimulation the relative permittivity of the plastic housing is
8 International Journal of Antennas and Propagation
340
95
78
54
46
95
55
580
150
215
55
215
40
09
20
40
30
18
02
020418
06
10
33
xy
z
05
➃➄➅➆
➀➇
➁➂
(a)
20 22 24 26 28
Frequency (GHz)
minus10
minus5
0
minus15
minus20
minus25
minus30
minus35
Spa
ram
eter
s (dB
)
S11 simulationS22 simulationS33 simulationS44 simulation
S11 measurementS22 measurementS33 measurementS44 measurement
(b)
Isol
atio
n (d
B)
20 22 24 26 28
Frequency (GHz)
S12S13S14
S16S17S18
S15
minus10
minus15
minus20
minus25
minus30
minus35
minus40
minus45
minus50
(c)
0024
0020
0016
0012
0008
0004
0000
Cor
relat
ion
coeffi
cien
t
20 22 24 26 28 30
Frequency (GHz)
Antennas 1 and 2
Antennas 1 and 3
Antennas 1 and 4
Antennas 1 and 5
Antennas 1 and 6Antennas 1 and 7Antennas 1 and 8
(d)
Figure 14 (a) Geometry of the 8-element MIMO antenna system (b) Reflection coefficients of the MIMO antenna system (c) Measuredisolation between MIMO antenna elements (d) Correlation coefficient |120588| curves for the proposed MIMO antenna system
set as 33 and the loss tangent is 002 the same as [23] Figures16(b) and 16(c) show the influence of the plastic housing onreflection coefficients and isolation Differences between thetwo cases are small and acceptable and show this MIMOsystem is competitive for practical application
4 Conclusion
Symmetric planar monopole antenna for compact multiele-ment MIMO antenna systems is proposed Isolation higher
than 15 dB over the operating band is realized by using polar-ization diversity of the antenna elements Correlation coeffi-cient 119878-parameters radiation characteristics and acceptableperformance when placed with conductive plane and plastichousing show that the proposed antenna arrays can be usedfor practical MIMO applications
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
International Journal of Antennas and Propagation 9
Metal sheet(a)
20 22 24 26 28
Frequency (GHz)
minus10
minus5
0
minus15
minus20
minus25
minus30
minus35
Spa
ram
eter
s (dB
)
Without metal sheet1mm2mm
3mm4mm5mm
(b)
20 22 24 26 28
Frequency (GHz)
minus15
minus20
minus25
minus30
minus35
Isol
atio
n (d
B)
S12 and S211mm2mm
3mm4mm5mm
(c)
Figure 15 (a) Proposed MIMO antenna with a metal sheet sepa-rated by free space (b) Reflection coefficients of theMIMO antennasystemwith ametal sheet (c) Isolation of theMIMOantenna systemwith a metal sheet
Plastichousing
(a)
20 22 24 26 28
Frequency (GHz)
minus10
minus5
0
minus15
minus20
minus25
Spa
ram
eter
s (dB
)
S11 with plastic housingS11 without plastic housing
(b)
20 22 24 26 28
Frequency (GHz)
Isol
atio
n (d
B)
minus15
minus20
minus30
minus25
S12 and S21 with plastic housingS12 and S21 without plastic housing
(c)
Figure 16 (a) Proposed antenna with plastic housing (b) Reflectioncoefficients (c) Isolation
10 International Journal of Antennas and Propagation
Acknowledgment
This work was supported by the Priority Academic Pro-gram Development of Jiangsu Higher Education Institutions(PAPD)
References
[1] T Kokkinos E Liakou and A P Feresidis ldquoDecouplingantenna elements of PIFAarrays onhandheld devicesrdquoElectron-ics Letters vol 44 no 25 pp 1442ndash1444 2008
[2] H Li J Xiong Z Ying and S L He ldquoCompact and low profileco-locatedMIMO antenna structure with polarisation diversityand high port isolationrdquo Electronics Letters vol 46 no 2 pp108ndash110 2010
[3] S Zhang P Zetterberg and S He ldquoPrinted MIMO antennasystem of four closely-spaced elements with large bandwidthand high isolationrdquo Electronics Letters vol 46 no 15 pp 1052ndash1053 2010
[4] C Yang J Kim H Kim J Wee B Kim and C Jung ldquoQuad-band antenna with high isolation MIMO and broadbandSCS for broadcasting and telecommunication servicesrdquo IEEEAntennas and Wireless Propagation Letters vol 9 pp 584ndash5872010
[5] S Park and C Jung ldquoCompact MIMO antenna with highisolation performancerdquo Electronics Letters vol 46 no 6 pp390ndash391 2010
[6] H S Farahani M Veysi M Kamyab and A Tadjalli ldquoMutualcoupling reduction in patch antenna arrays using a UC-EBGsuperstraterdquo IEEE Antennas and Wireless Propagation Lettersvol 9 pp 57ndash59 2010
[7] G Exposito-Domınguez J M Fernandez-Gonzalez P Padillaand M Sierra-Castaner ldquoNew EBG solutions for mutual cou-pling reductionrdquo in Proceedings of the 6th European Conferenceon Antennas and Propagation (EUCAP rsquo12) pp 2841ndash2844IEEE Prague Czech Republic March 2012
[8] A Habashi J Nourinia and C Ghobadi ldquoA rectangulardefected ground structure (DGS) for reduction of mutualcoupling between closely-spaced microstrip antennasrdquo in Pro-ceedings of the 20th Iranian Conference on Electrical Engineering(ICEE rsquo12) pp 1347ndash1350 IEEE Tehran Iran May 2012
[9] L Wang and B Huang ldquoDesign of ultra-wideband MIMOantenna for breast tumor detectionrdquo International Journal ofAntennas and Propagation vol 2012 Article ID 180158 7 pages2012
[10] M Gallo E Antonino-Daviu M Ferrando-Bataller MBozzetti J M Molina-Garcia-Pardo and L Juan-Llacer ldquoAbroadband pattern diversity annular slot antennardquo IEEE Trans-actions on Antennas and Propagation vol 60 no 3 pp 1596ndash1600 2012
[11] D-G Kang J Tak and J Chio ldquoMIMO antenna with highisolation for WBAN applicationsrdquo International Journal ofAntennas and Propagation vol 2015 Article ID 370763 7 pages2015
[12] Y K Choukiker S K Sharma and S K Behera ldquoHybrid fractalshape planar monopole antenna covering multiband wirelesscommunications with MIMO implementation for handheldmobile devicesrdquo IEEE Transactions on Antennas and Propaga-tion vol 62 no 3 pp 1483ndash1488 2014
[13] Q Zeng Y Yao S Liu J Yu P Xie and X Chen ldquoTetrabandsmall-size printed strip MIMO antenna for mobile handset
applicationrdquo International Journal of Antennas and Propagationvol 2012 Article ID 320582 8 pages 2012
[14] KWang R AMMauermayer and T F Eibert ldquoCompact two-element printedmonopole arraywith partially extended groundplanerdquo IEEE Antennas and Wireless Propagation Letters vol 13pp 138ndash140 2014
[15] J Park J Choi J-Y Park and Y-S Kim ldquoStudy of a T-shaped slot with a capacitor for high isolation between MIMOantennasrdquo IEEE Antennas andWireless Propagation Letters vol11 pp 1541ndash1544 2012
[16] M G N Alsath M Kanagasabai and B BalasubramanianldquoImplementation of slotted meander-line resonators for isola-tion enhancement in microstrip patch antenna arraysrdquo IEEEAntennas and Wireless Propagation Letters vol 12 pp 15ndash182013
[17] H Arun A K Sarma M Kanagasabai S Velan C Ravitejaand M G N Alsath ldquoDeployment of modified serpentinestructure for mutual coupling reduction in MIMO antennasrdquoIEEEAntennas andWireless Propagation Letters vol 13 pp 277ndash280 2014
[18] httpsenwikipediaorgwikiMCX connector[19] S Blanch J Romeu and I Corbella ldquoExact representation of
antenna system diversity performance from input parameterdescriptionrdquo Electronics Letters vol 39 no 9 pp 705ndash707 2003
[20] 3GPP ldquoEUTRA user equipment radio transmission and recep-tionrdquo 3GPP TS 36101 V830 September 2008
[21] L Song and J Shen Evolved Cellular Network Planning andOptimization for UMTS and LTE CRCPress London UK 2011
[22] M S Sharawi M U Khan A B Numan and D N Aloi ldquoACSRR loaded MIMO antenna system for ISM band operationrdquoIEEE Transactions on Antennas and Propagation vol 61 no 8pp 4265ndash4274 2013
[23] Y-L Ban J-H Chen J L-W Li and Y J Wu ldquoSmall-sizeprinted coupled-fed antenna for eight-band LTEGSMUMTSwireless wide area network operation in an internal mobilehandsetrdquo IET Microwaves Antennas amp Propagation vol 7 no6 pp 399ndash407 2013
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
International Journal of Antennas and Propagation 5
Lg
Size 216mm times 155mm
(a)
0
minus5
minus10
minus15
minus20
minus2520 22 24 26 28
Frequency (GHz)
Spa
ram
eter
s (dB
)
S11S22
S12(S21)S21 prototype
(b)
Figure 6 (a) MIMO antenna system Type II (b) 119878 parameters of Type II
78mm
Size 315mm times 155mm
(a)
0
minus5
minus10
minus15
minus25
minus35
minus20
minus30
20 22 24 26 28
Frequency (GHz)
Spa
ram
eter
s (dB
)
S11S22
S12(S21)S21 prototype
(b)
Figure 7 (a) Orthogonally arranged MIMO antenna system (b) 119878 parameters
Figure 11 shows the correlation coefficient between theantenna elements of the proposed MIMO antenna systemThe antenna efficiency was higher than 78 through theworking band The results are well below 03 which is themaximum value set for 4G standards [20]
The gain of the proposedMIMOantenna system is shownin Figure 12 The simulated peak gain in the +119911 direction is072 dBi at 241 GHz and the measured peak gain is 062 dBiat 24GHz
The radiation pattern of the proposed MIMO antennasystem is shown in Figure 13 The radiation pattern wasobtained when one element was excited and the other is
terminated with a 50 ohm load The radiation pattern is justlike a monopole which has an omnidirectional radiation inthe119867 plane at the resonant frequency
32 Eight-Element MIMO Systems According to [21] theincrease of the number of transmitter antennas and receiverantennas can improve the communication quality andincrease the channel capacity without extra radiation powerand spectrum bandwidth An eight-element MIMO antennasystem was also fabricated and measured Its measured
6 International Journal of Antennas and Propagation
Figure 8 Photograph of the fabricated MIMO antenna system
0
minus5
minus10
minus15
minus20
minus30
minus25
20 22 24 26 28
Frequency (GHz)
Spa
ram
eter
s (dB
)
S11 simulatedS22 simulated
S11 measurementS22 measurement
Figure 9 Simulated and measured 119878 parameters of the proposedMIMO antenna system
minus10 dB bandwidth is 340MHz (218ndash252GHz) as shownin Figure 14(a) good agreement is realized for the sake ofclarity we only put the results of four antennas here Themeasured isolation between antennas is lower than minus15 dB atthe whole operating band The simulated radiation efficiencyof the antenna element is higher than 77 over the wholeband The correlation coefficient can be calculated by using(3) As plotted in Figure 14(d) the value is far smaller than03
33 Practical Applications For practical applications MIMOantenna system is integrated with other components suchas circuit board and LCD screen which means that aconductive plane under the system should be taken intoconsideration
In Figure 15(a) the MIMO antenna system was placedabove a metal sheet separated by free space The separationbetween the conductive board and antenna bottom sidewas varied from 1 to 5mm in 1-mm steps Figures 15(b)and 15(c) show the reflection coefficients and the isolationcharacteristics of the antenna element over a metal sheet atdifferent distances
minus15
minus20
minus2520 22 24 26 28
Frequency (GHz)
Isol
atio
n (d
B)
S12(S21) simulatedS12(S21) measurement
Figure 10 Isolation of MIMO antenna system
Frequency (GHz)
0016
0014
0012
0010
0008
0006
0004
0002
000020 22 24 26 28 30
Antenna 1 and antenna 2
Cor
relat
ion
coeffi
cien
t
Figure 11 Correlation coefficient curve for the proposed MIMOantenna system
Frequency (GHz)
SimulationMeasurement
10
05
00
minus05
minus10
minus15
minus20
minus25
Gai
n (d
Bi)
21 22 23 24 25 26
Figure 12 Gain of MIMO antenna system
International Journal of Antennas and Propagation 7
0
minus10
minus20
minus30
minus40
minus30
minus20
minus10
0
0
30
60
90
120
150
180
210
240
270
300
330
245GHz-Phi-simulation245GHz-Theta-simulation245GHz-Phi-measurement245GHz-Theta-measurement
XZ
(a)
0
minus10
minus20
minus30
minus20
minus10
0
0
30
60
90
120
150
180
210
240
270
300
330
245GHz-Phi-simulation245GHz-Theta-simulation245GHz-Phi-measurement245GHz-Theta-measurement
YZ
(b)
0
minus10
minus20
minus30
minus20
minus10
0
0
30
60
90
120
150
180
210
240
270
300
330
245GHz-Phi-simulation245GHz-Theta-simulation245GHz-Phi-measurement245GHz-Theta-measurement
XY
(c)
Figure 13 Radiation pattern of the proposed MIMO antenna at 245GHz (a) 119909119911-plane (b) 119910119911-plane and (c) 119909119910-plane
It was found that by using a metal sheet the resonantfrequency of the individual antenna element shifted Asthe distance between the antenna and conductive planeincreased the effect weakens When the board is closelyplaced under the system like 1mm the resonant frequencychanged most but the working band can still cover theLTE2300 and 245GHz ISM band This is unlike the systemreported in [22] the antenna system does not have any
special designed structures on the back side of the sub-strate so it is not obligatory to place the system carefullysuch that its bottom side maintains a minimum distancelike 3 to 5mm from any conductive plane for practicaldesign
Figure 16(a) shows a 1mm thick plastic housing which isused to simulate the practical case of thewireless terminals Insimulation the relative permittivity of the plastic housing is
8 International Journal of Antennas and Propagation
340
95
78
54
46
95
55
580
150
215
55
215
40
09
20
40
30
18
02
020418
06
10
33
xy
z
05
➃➄➅➆
➀➇
➁➂
(a)
20 22 24 26 28
Frequency (GHz)
minus10
minus5
0
minus15
minus20
minus25
minus30
minus35
Spa
ram
eter
s (dB
)
S11 simulationS22 simulationS33 simulationS44 simulation
S11 measurementS22 measurementS33 measurementS44 measurement
(b)
Isol
atio
n (d
B)
20 22 24 26 28
Frequency (GHz)
S12S13S14
S16S17S18
S15
minus10
minus15
minus20
minus25
minus30
minus35
minus40
minus45
minus50
(c)
0024
0020
0016
0012
0008
0004
0000
Cor
relat
ion
coeffi
cien
t
20 22 24 26 28 30
Frequency (GHz)
Antennas 1 and 2
Antennas 1 and 3
Antennas 1 and 4
Antennas 1 and 5
Antennas 1 and 6Antennas 1 and 7Antennas 1 and 8
(d)
Figure 14 (a) Geometry of the 8-element MIMO antenna system (b) Reflection coefficients of the MIMO antenna system (c) Measuredisolation between MIMO antenna elements (d) Correlation coefficient |120588| curves for the proposed MIMO antenna system
set as 33 and the loss tangent is 002 the same as [23] Figures16(b) and 16(c) show the influence of the plastic housing onreflection coefficients and isolation Differences between thetwo cases are small and acceptable and show this MIMOsystem is competitive for practical application
4 Conclusion
Symmetric planar monopole antenna for compact multiele-ment MIMO antenna systems is proposed Isolation higher
than 15 dB over the operating band is realized by using polar-ization diversity of the antenna elements Correlation coeffi-cient 119878-parameters radiation characteristics and acceptableperformance when placed with conductive plane and plastichousing show that the proposed antenna arrays can be usedfor practical MIMO applications
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
International Journal of Antennas and Propagation 9
Metal sheet(a)
20 22 24 26 28
Frequency (GHz)
minus10
minus5
0
minus15
minus20
minus25
minus30
minus35
Spa
ram
eter
s (dB
)
Without metal sheet1mm2mm
3mm4mm5mm
(b)
20 22 24 26 28
Frequency (GHz)
minus15
minus20
minus25
minus30
minus35
Isol
atio
n (d
B)
S12 and S211mm2mm
3mm4mm5mm
(c)
Figure 15 (a) Proposed MIMO antenna with a metal sheet sepa-rated by free space (b) Reflection coefficients of theMIMO antennasystemwith ametal sheet (c) Isolation of theMIMOantenna systemwith a metal sheet
Plastichousing
(a)
20 22 24 26 28
Frequency (GHz)
minus10
minus5
0
minus15
minus20
minus25
Spa
ram
eter
s (dB
)
S11 with plastic housingS11 without plastic housing
(b)
20 22 24 26 28
Frequency (GHz)
Isol
atio
n (d
B)
minus15
minus20
minus30
minus25
S12 and S21 with plastic housingS12 and S21 without plastic housing
(c)
Figure 16 (a) Proposed antenna with plastic housing (b) Reflectioncoefficients (c) Isolation
10 International Journal of Antennas and Propagation
Acknowledgment
This work was supported by the Priority Academic Pro-gram Development of Jiangsu Higher Education Institutions(PAPD)
References
[1] T Kokkinos E Liakou and A P Feresidis ldquoDecouplingantenna elements of PIFAarrays onhandheld devicesrdquoElectron-ics Letters vol 44 no 25 pp 1442ndash1444 2008
[2] H Li J Xiong Z Ying and S L He ldquoCompact and low profileco-locatedMIMO antenna structure with polarisation diversityand high port isolationrdquo Electronics Letters vol 46 no 2 pp108ndash110 2010
[3] S Zhang P Zetterberg and S He ldquoPrinted MIMO antennasystem of four closely-spaced elements with large bandwidthand high isolationrdquo Electronics Letters vol 46 no 15 pp 1052ndash1053 2010
[4] C Yang J Kim H Kim J Wee B Kim and C Jung ldquoQuad-band antenna with high isolation MIMO and broadbandSCS for broadcasting and telecommunication servicesrdquo IEEEAntennas and Wireless Propagation Letters vol 9 pp 584ndash5872010
[5] S Park and C Jung ldquoCompact MIMO antenna with highisolation performancerdquo Electronics Letters vol 46 no 6 pp390ndash391 2010
[6] H S Farahani M Veysi M Kamyab and A Tadjalli ldquoMutualcoupling reduction in patch antenna arrays using a UC-EBGsuperstraterdquo IEEE Antennas and Wireless Propagation Lettersvol 9 pp 57ndash59 2010
[7] G Exposito-Domınguez J M Fernandez-Gonzalez P Padillaand M Sierra-Castaner ldquoNew EBG solutions for mutual cou-pling reductionrdquo in Proceedings of the 6th European Conferenceon Antennas and Propagation (EUCAP rsquo12) pp 2841ndash2844IEEE Prague Czech Republic March 2012
[8] A Habashi J Nourinia and C Ghobadi ldquoA rectangulardefected ground structure (DGS) for reduction of mutualcoupling between closely-spaced microstrip antennasrdquo in Pro-ceedings of the 20th Iranian Conference on Electrical Engineering(ICEE rsquo12) pp 1347ndash1350 IEEE Tehran Iran May 2012
[9] L Wang and B Huang ldquoDesign of ultra-wideband MIMOantenna for breast tumor detectionrdquo International Journal ofAntennas and Propagation vol 2012 Article ID 180158 7 pages2012
[10] M Gallo E Antonino-Daviu M Ferrando-Bataller MBozzetti J M Molina-Garcia-Pardo and L Juan-Llacer ldquoAbroadband pattern diversity annular slot antennardquo IEEE Trans-actions on Antennas and Propagation vol 60 no 3 pp 1596ndash1600 2012
[11] D-G Kang J Tak and J Chio ldquoMIMO antenna with highisolation for WBAN applicationsrdquo International Journal ofAntennas and Propagation vol 2015 Article ID 370763 7 pages2015
[12] Y K Choukiker S K Sharma and S K Behera ldquoHybrid fractalshape planar monopole antenna covering multiband wirelesscommunications with MIMO implementation for handheldmobile devicesrdquo IEEE Transactions on Antennas and Propaga-tion vol 62 no 3 pp 1483ndash1488 2014
[13] Q Zeng Y Yao S Liu J Yu P Xie and X Chen ldquoTetrabandsmall-size printed strip MIMO antenna for mobile handset
applicationrdquo International Journal of Antennas and Propagationvol 2012 Article ID 320582 8 pages 2012
[14] KWang R AMMauermayer and T F Eibert ldquoCompact two-element printedmonopole arraywith partially extended groundplanerdquo IEEE Antennas and Wireless Propagation Letters vol 13pp 138ndash140 2014
[15] J Park J Choi J-Y Park and Y-S Kim ldquoStudy of a T-shaped slot with a capacitor for high isolation between MIMOantennasrdquo IEEE Antennas andWireless Propagation Letters vol11 pp 1541ndash1544 2012
[16] M G N Alsath M Kanagasabai and B BalasubramanianldquoImplementation of slotted meander-line resonators for isola-tion enhancement in microstrip patch antenna arraysrdquo IEEEAntennas and Wireless Propagation Letters vol 12 pp 15ndash182013
[17] H Arun A K Sarma M Kanagasabai S Velan C Ravitejaand M G N Alsath ldquoDeployment of modified serpentinestructure for mutual coupling reduction in MIMO antennasrdquoIEEEAntennas andWireless Propagation Letters vol 13 pp 277ndash280 2014
[18] httpsenwikipediaorgwikiMCX connector[19] S Blanch J Romeu and I Corbella ldquoExact representation of
antenna system diversity performance from input parameterdescriptionrdquo Electronics Letters vol 39 no 9 pp 705ndash707 2003
[20] 3GPP ldquoEUTRA user equipment radio transmission and recep-tionrdquo 3GPP TS 36101 V830 September 2008
[21] L Song and J Shen Evolved Cellular Network Planning andOptimization for UMTS and LTE CRCPress London UK 2011
[22] M S Sharawi M U Khan A B Numan and D N Aloi ldquoACSRR loaded MIMO antenna system for ISM band operationrdquoIEEE Transactions on Antennas and Propagation vol 61 no 8pp 4265ndash4274 2013
[23] Y-L Ban J-H Chen J L-W Li and Y J Wu ldquoSmall-sizeprinted coupled-fed antenna for eight-band LTEGSMUMTSwireless wide area network operation in an internal mobilehandsetrdquo IET Microwaves Antennas amp Propagation vol 7 no6 pp 399ndash407 2013
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
6 International Journal of Antennas and Propagation
Figure 8 Photograph of the fabricated MIMO antenna system
0
minus5
minus10
minus15
minus20
minus30
minus25
20 22 24 26 28
Frequency (GHz)
Spa
ram
eter
s (dB
)
S11 simulatedS22 simulated
S11 measurementS22 measurement
Figure 9 Simulated and measured 119878 parameters of the proposedMIMO antenna system
minus10 dB bandwidth is 340MHz (218ndash252GHz) as shownin Figure 14(a) good agreement is realized for the sake ofclarity we only put the results of four antennas here Themeasured isolation between antennas is lower than minus15 dB atthe whole operating band The simulated radiation efficiencyof the antenna element is higher than 77 over the wholeband The correlation coefficient can be calculated by using(3) As plotted in Figure 14(d) the value is far smaller than03
33 Practical Applications For practical applications MIMOantenna system is integrated with other components suchas circuit board and LCD screen which means that aconductive plane under the system should be taken intoconsideration
In Figure 15(a) the MIMO antenna system was placedabove a metal sheet separated by free space The separationbetween the conductive board and antenna bottom sidewas varied from 1 to 5mm in 1-mm steps Figures 15(b)and 15(c) show the reflection coefficients and the isolationcharacteristics of the antenna element over a metal sheet atdifferent distances
minus15
minus20
minus2520 22 24 26 28
Frequency (GHz)
Isol
atio
n (d
B)
S12(S21) simulatedS12(S21) measurement
Figure 10 Isolation of MIMO antenna system
Frequency (GHz)
0016
0014
0012
0010
0008
0006
0004
0002
000020 22 24 26 28 30
Antenna 1 and antenna 2
Cor
relat
ion
coeffi
cien
t
Figure 11 Correlation coefficient curve for the proposed MIMOantenna system
Frequency (GHz)
SimulationMeasurement
10
05
00
minus05
minus10
minus15
minus20
minus25
Gai
n (d
Bi)
21 22 23 24 25 26
Figure 12 Gain of MIMO antenna system
International Journal of Antennas and Propagation 7
0
minus10
minus20
minus30
minus40
minus30
minus20
minus10
0
0
30
60
90
120
150
180
210
240
270
300
330
245GHz-Phi-simulation245GHz-Theta-simulation245GHz-Phi-measurement245GHz-Theta-measurement
XZ
(a)
0
minus10
minus20
minus30
minus20
minus10
0
0
30
60
90
120
150
180
210
240
270
300
330
245GHz-Phi-simulation245GHz-Theta-simulation245GHz-Phi-measurement245GHz-Theta-measurement
YZ
(b)
0
minus10
minus20
minus30
minus20
minus10
0
0
30
60
90
120
150
180
210
240
270
300
330
245GHz-Phi-simulation245GHz-Theta-simulation245GHz-Phi-measurement245GHz-Theta-measurement
XY
(c)
Figure 13 Radiation pattern of the proposed MIMO antenna at 245GHz (a) 119909119911-plane (b) 119910119911-plane and (c) 119909119910-plane
It was found that by using a metal sheet the resonantfrequency of the individual antenna element shifted Asthe distance between the antenna and conductive planeincreased the effect weakens When the board is closelyplaced under the system like 1mm the resonant frequencychanged most but the working band can still cover theLTE2300 and 245GHz ISM band This is unlike the systemreported in [22] the antenna system does not have any
special designed structures on the back side of the sub-strate so it is not obligatory to place the system carefullysuch that its bottom side maintains a minimum distancelike 3 to 5mm from any conductive plane for practicaldesign
Figure 16(a) shows a 1mm thick plastic housing which isused to simulate the practical case of thewireless terminals Insimulation the relative permittivity of the plastic housing is
8 International Journal of Antennas and Propagation
340
95
78
54
46
95
55
580
150
215
55
215
40
09
20
40
30
18
02
020418
06
10
33
xy
z
05
➃➄➅➆
➀➇
➁➂
(a)
20 22 24 26 28
Frequency (GHz)
minus10
minus5
0
minus15
minus20
minus25
minus30
minus35
Spa
ram
eter
s (dB
)
S11 simulationS22 simulationS33 simulationS44 simulation
S11 measurementS22 measurementS33 measurementS44 measurement
(b)
Isol
atio
n (d
B)
20 22 24 26 28
Frequency (GHz)
S12S13S14
S16S17S18
S15
minus10
minus15
minus20
minus25
minus30
minus35
minus40
minus45
minus50
(c)
0024
0020
0016
0012
0008
0004
0000
Cor
relat
ion
coeffi
cien
t
20 22 24 26 28 30
Frequency (GHz)
Antennas 1 and 2
Antennas 1 and 3
Antennas 1 and 4
Antennas 1 and 5
Antennas 1 and 6Antennas 1 and 7Antennas 1 and 8
(d)
Figure 14 (a) Geometry of the 8-element MIMO antenna system (b) Reflection coefficients of the MIMO antenna system (c) Measuredisolation between MIMO antenna elements (d) Correlation coefficient |120588| curves for the proposed MIMO antenna system
set as 33 and the loss tangent is 002 the same as [23] Figures16(b) and 16(c) show the influence of the plastic housing onreflection coefficients and isolation Differences between thetwo cases are small and acceptable and show this MIMOsystem is competitive for practical application
4 Conclusion
Symmetric planar monopole antenna for compact multiele-ment MIMO antenna systems is proposed Isolation higher
than 15 dB over the operating band is realized by using polar-ization diversity of the antenna elements Correlation coeffi-cient 119878-parameters radiation characteristics and acceptableperformance when placed with conductive plane and plastichousing show that the proposed antenna arrays can be usedfor practical MIMO applications
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
International Journal of Antennas and Propagation 9
Metal sheet(a)
20 22 24 26 28
Frequency (GHz)
minus10
minus5
0
minus15
minus20
minus25
minus30
minus35
Spa
ram
eter
s (dB
)
Without metal sheet1mm2mm
3mm4mm5mm
(b)
20 22 24 26 28
Frequency (GHz)
minus15
minus20
minus25
minus30
minus35
Isol
atio
n (d
B)
S12 and S211mm2mm
3mm4mm5mm
(c)
Figure 15 (a) Proposed MIMO antenna with a metal sheet sepa-rated by free space (b) Reflection coefficients of theMIMO antennasystemwith ametal sheet (c) Isolation of theMIMOantenna systemwith a metal sheet
Plastichousing
(a)
20 22 24 26 28
Frequency (GHz)
minus10
minus5
0
minus15
minus20
minus25
Spa
ram
eter
s (dB
)
S11 with plastic housingS11 without plastic housing
(b)
20 22 24 26 28
Frequency (GHz)
Isol
atio
n (d
B)
minus15
minus20
minus30
minus25
S12 and S21 with plastic housingS12 and S21 without plastic housing
(c)
Figure 16 (a) Proposed antenna with plastic housing (b) Reflectioncoefficients (c) Isolation
10 International Journal of Antennas and Propagation
Acknowledgment
This work was supported by the Priority Academic Pro-gram Development of Jiangsu Higher Education Institutions(PAPD)
References
[1] T Kokkinos E Liakou and A P Feresidis ldquoDecouplingantenna elements of PIFAarrays onhandheld devicesrdquoElectron-ics Letters vol 44 no 25 pp 1442ndash1444 2008
[2] H Li J Xiong Z Ying and S L He ldquoCompact and low profileco-locatedMIMO antenna structure with polarisation diversityand high port isolationrdquo Electronics Letters vol 46 no 2 pp108ndash110 2010
[3] S Zhang P Zetterberg and S He ldquoPrinted MIMO antennasystem of four closely-spaced elements with large bandwidthand high isolationrdquo Electronics Letters vol 46 no 15 pp 1052ndash1053 2010
[4] C Yang J Kim H Kim J Wee B Kim and C Jung ldquoQuad-band antenna with high isolation MIMO and broadbandSCS for broadcasting and telecommunication servicesrdquo IEEEAntennas and Wireless Propagation Letters vol 9 pp 584ndash5872010
[5] S Park and C Jung ldquoCompact MIMO antenna with highisolation performancerdquo Electronics Letters vol 46 no 6 pp390ndash391 2010
[6] H S Farahani M Veysi M Kamyab and A Tadjalli ldquoMutualcoupling reduction in patch antenna arrays using a UC-EBGsuperstraterdquo IEEE Antennas and Wireless Propagation Lettersvol 9 pp 57ndash59 2010
[7] G Exposito-Domınguez J M Fernandez-Gonzalez P Padillaand M Sierra-Castaner ldquoNew EBG solutions for mutual cou-pling reductionrdquo in Proceedings of the 6th European Conferenceon Antennas and Propagation (EUCAP rsquo12) pp 2841ndash2844IEEE Prague Czech Republic March 2012
[8] A Habashi J Nourinia and C Ghobadi ldquoA rectangulardefected ground structure (DGS) for reduction of mutualcoupling between closely-spaced microstrip antennasrdquo in Pro-ceedings of the 20th Iranian Conference on Electrical Engineering(ICEE rsquo12) pp 1347ndash1350 IEEE Tehran Iran May 2012
[9] L Wang and B Huang ldquoDesign of ultra-wideband MIMOantenna for breast tumor detectionrdquo International Journal ofAntennas and Propagation vol 2012 Article ID 180158 7 pages2012
[10] M Gallo E Antonino-Daviu M Ferrando-Bataller MBozzetti J M Molina-Garcia-Pardo and L Juan-Llacer ldquoAbroadband pattern diversity annular slot antennardquo IEEE Trans-actions on Antennas and Propagation vol 60 no 3 pp 1596ndash1600 2012
[11] D-G Kang J Tak and J Chio ldquoMIMO antenna with highisolation for WBAN applicationsrdquo International Journal ofAntennas and Propagation vol 2015 Article ID 370763 7 pages2015
[12] Y K Choukiker S K Sharma and S K Behera ldquoHybrid fractalshape planar monopole antenna covering multiband wirelesscommunications with MIMO implementation for handheldmobile devicesrdquo IEEE Transactions on Antennas and Propaga-tion vol 62 no 3 pp 1483ndash1488 2014
[13] Q Zeng Y Yao S Liu J Yu P Xie and X Chen ldquoTetrabandsmall-size printed strip MIMO antenna for mobile handset
applicationrdquo International Journal of Antennas and Propagationvol 2012 Article ID 320582 8 pages 2012
[14] KWang R AMMauermayer and T F Eibert ldquoCompact two-element printedmonopole arraywith partially extended groundplanerdquo IEEE Antennas and Wireless Propagation Letters vol 13pp 138ndash140 2014
[15] J Park J Choi J-Y Park and Y-S Kim ldquoStudy of a T-shaped slot with a capacitor for high isolation between MIMOantennasrdquo IEEE Antennas andWireless Propagation Letters vol11 pp 1541ndash1544 2012
[16] M G N Alsath M Kanagasabai and B BalasubramanianldquoImplementation of slotted meander-line resonators for isola-tion enhancement in microstrip patch antenna arraysrdquo IEEEAntennas and Wireless Propagation Letters vol 12 pp 15ndash182013
[17] H Arun A K Sarma M Kanagasabai S Velan C Ravitejaand M G N Alsath ldquoDeployment of modified serpentinestructure for mutual coupling reduction in MIMO antennasrdquoIEEEAntennas andWireless Propagation Letters vol 13 pp 277ndash280 2014
[18] httpsenwikipediaorgwikiMCX connector[19] S Blanch J Romeu and I Corbella ldquoExact representation of
antenna system diversity performance from input parameterdescriptionrdquo Electronics Letters vol 39 no 9 pp 705ndash707 2003
[20] 3GPP ldquoEUTRA user equipment radio transmission and recep-tionrdquo 3GPP TS 36101 V830 September 2008
[21] L Song and J Shen Evolved Cellular Network Planning andOptimization for UMTS and LTE CRCPress London UK 2011
[22] M S Sharawi M U Khan A B Numan and D N Aloi ldquoACSRR loaded MIMO antenna system for ISM band operationrdquoIEEE Transactions on Antennas and Propagation vol 61 no 8pp 4265ndash4274 2013
[23] Y-L Ban J-H Chen J L-W Li and Y J Wu ldquoSmall-sizeprinted coupled-fed antenna for eight-band LTEGSMUMTSwireless wide area network operation in an internal mobilehandsetrdquo IET Microwaves Antennas amp Propagation vol 7 no6 pp 399ndash407 2013
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
International Journal of Antennas and Propagation 7
0
minus10
minus20
minus30
minus40
minus30
minus20
minus10
0
0
30
60
90
120
150
180
210
240
270
300
330
245GHz-Phi-simulation245GHz-Theta-simulation245GHz-Phi-measurement245GHz-Theta-measurement
XZ
(a)
0
minus10
minus20
minus30
minus20
minus10
0
0
30
60
90
120
150
180
210
240
270
300
330
245GHz-Phi-simulation245GHz-Theta-simulation245GHz-Phi-measurement245GHz-Theta-measurement
YZ
(b)
0
minus10
minus20
minus30
minus20
minus10
0
0
30
60
90
120
150
180
210
240
270
300
330
245GHz-Phi-simulation245GHz-Theta-simulation245GHz-Phi-measurement245GHz-Theta-measurement
XY
(c)
Figure 13 Radiation pattern of the proposed MIMO antenna at 245GHz (a) 119909119911-plane (b) 119910119911-plane and (c) 119909119910-plane
It was found that by using a metal sheet the resonantfrequency of the individual antenna element shifted Asthe distance between the antenna and conductive planeincreased the effect weakens When the board is closelyplaced under the system like 1mm the resonant frequencychanged most but the working band can still cover theLTE2300 and 245GHz ISM band This is unlike the systemreported in [22] the antenna system does not have any
special designed structures on the back side of the sub-strate so it is not obligatory to place the system carefullysuch that its bottom side maintains a minimum distancelike 3 to 5mm from any conductive plane for practicaldesign
Figure 16(a) shows a 1mm thick plastic housing which isused to simulate the practical case of thewireless terminals Insimulation the relative permittivity of the plastic housing is
8 International Journal of Antennas and Propagation
340
95
78
54
46
95
55
580
150
215
55
215
40
09
20
40
30
18
02
020418
06
10
33
xy
z
05
➃➄➅➆
➀➇
➁➂
(a)
20 22 24 26 28
Frequency (GHz)
minus10
minus5
0
minus15
minus20
minus25
minus30
minus35
Spa
ram
eter
s (dB
)
S11 simulationS22 simulationS33 simulationS44 simulation
S11 measurementS22 measurementS33 measurementS44 measurement
(b)
Isol
atio
n (d
B)
20 22 24 26 28
Frequency (GHz)
S12S13S14
S16S17S18
S15
minus10
minus15
minus20
minus25
minus30
minus35
minus40
minus45
minus50
(c)
0024
0020
0016
0012
0008
0004
0000
Cor
relat
ion
coeffi
cien
t
20 22 24 26 28 30
Frequency (GHz)
Antennas 1 and 2
Antennas 1 and 3
Antennas 1 and 4
Antennas 1 and 5
Antennas 1 and 6Antennas 1 and 7Antennas 1 and 8
(d)
Figure 14 (a) Geometry of the 8-element MIMO antenna system (b) Reflection coefficients of the MIMO antenna system (c) Measuredisolation between MIMO antenna elements (d) Correlation coefficient |120588| curves for the proposed MIMO antenna system
set as 33 and the loss tangent is 002 the same as [23] Figures16(b) and 16(c) show the influence of the plastic housing onreflection coefficients and isolation Differences between thetwo cases are small and acceptable and show this MIMOsystem is competitive for practical application
4 Conclusion
Symmetric planar monopole antenna for compact multiele-ment MIMO antenna systems is proposed Isolation higher
than 15 dB over the operating band is realized by using polar-ization diversity of the antenna elements Correlation coeffi-cient 119878-parameters radiation characteristics and acceptableperformance when placed with conductive plane and plastichousing show that the proposed antenna arrays can be usedfor practical MIMO applications
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
International Journal of Antennas and Propagation 9
Metal sheet(a)
20 22 24 26 28
Frequency (GHz)
minus10
minus5
0
minus15
minus20
minus25
minus30
minus35
Spa
ram
eter
s (dB
)
Without metal sheet1mm2mm
3mm4mm5mm
(b)
20 22 24 26 28
Frequency (GHz)
minus15
minus20
minus25
minus30
minus35
Isol
atio
n (d
B)
S12 and S211mm2mm
3mm4mm5mm
(c)
Figure 15 (a) Proposed MIMO antenna with a metal sheet sepa-rated by free space (b) Reflection coefficients of theMIMO antennasystemwith ametal sheet (c) Isolation of theMIMOantenna systemwith a metal sheet
Plastichousing
(a)
20 22 24 26 28
Frequency (GHz)
minus10
minus5
0
minus15
minus20
minus25
Spa
ram
eter
s (dB
)
S11 with plastic housingS11 without plastic housing
(b)
20 22 24 26 28
Frequency (GHz)
Isol
atio
n (d
B)
minus15
minus20
minus30
minus25
S12 and S21 with plastic housingS12 and S21 without plastic housing
(c)
Figure 16 (a) Proposed antenna with plastic housing (b) Reflectioncoefficients (c) Isolation
10 International Journal of Antennas and Propagation
Acknowledgment
This work was supported by the Priority Academic Pro-gram Development of Jiangsu Higher Education Institutions(PAPD)
References
[1] T Kokkinos E Liakou and A P Feresidis ldquoDecouplingantenna elements of PIFAarrays onhandheld devicesrdquoElectron-ics Letters vol 44 no 25 pp 1442ndash1444 2008
[2] H Li J Xiong Z Ying and S L He ldquoCompact and low profileco-locatedMIMO antenna structure with polarisation diversityand high port isolationrdquo Electronics Letters vol 46 no 2 pp108ndash110 2010
[3] S Zhang P Zetterberg and S He ldquoPrinted MIMO antennasystem of four closely-spaced elements with large bandwidthand high isolationrdquo Electronics Letters vol 46 no 15 pp 1052ndash1053 2010
[4] C Yang J Kim H Kim J Wee B Kim and C Jung ldquoQuad-band antenna with high isolation MIMO and broadbandSCS for broadcasting and telecommunication servicesrdquo IEEEAntennas and Wireless Propagation Letters vol 9 pp 584ndash5872010
[5] S Park and C Jung ldquoCompact MIMO antenna with highisolation performancerdquo Electronics Letters vol 46 no 6 pp390ndash391 2010
[6] H S Farahani M Veysi M Kamyab and A Tadjalli ldquoMutualcoupling reduction in patch antenna arrays using a UC-EBGsuperstraterdquo IEEE Antennas and Wireless Propagation Lettersvol 9 pp 57ndash59 2010
[7] G Exposito-Domınguez J M Fernandez-Gonzalez P Padillaand M Sierra-Castaner ldquoNew EBG solutions for mutual cou-pling reductionrdquo in Proceedings of the 6th European Conferenceon Antennas and Propagation (EUCAP rsquo12) pp 2841ndash2844IEEE Prague Czech Republic March 2012
[8] A Habashi J Nourinia and C Ghobadi ldquoA rectangulardefected ground structure (DGS) for reduction of mutualcoupling between closely-spaced microstrip antennasrdquo in Pro-ceedings of the 20th Iranian Conference on Electrical Engineering(ICEE rsquo12) pp 1347ndash1350 IEEE Tehran Iran May 2012
[9] L Wang and B Huang ldquoDesign of ultra-wideband MIMOantenna for breast tumor detectionrdquo International Journal ofAntennas and Propagation vol 2012 Article ID 180158 7 pages2012
[10] M Gallo E Antonino-Daviu M Ferrando-Bataller MBozzetti J M Molina-Garcia-Pardo and L Juan-Llacer ldquoAbroadband pattern diversity annular slot antennardquo IEEE Trans-actions on Antennas and Propagation vol 60 no 3 pp 1596ndash1600 2012
[11] D-G Kang J Tak and J Chio ldquoMIMO antenna with highisolation for WBAN applicationsrdquo International Journal ofAntennas and Propagation vol 2015 Article ID 370763 7 pages2015
[12] Y K Choukiker S K Sharma and S K Behera ldquoHybrid fractalshape planar monopole antenna covering multiband wirelesscommunications with MIMO implementation for handheldmobile devicesrdquo IEEE Transactions on Antennas and Propaga-tion vol 62 no 3 pp 1483ndash1488 2014
[13] Q Zeng Y Yao S Liu J Yu P Xie and X Chen ldquoTetrabandsmall-size printed strip MIMO antenna for mobile handset
applicationrdquo International Journal of Antennas and Propagationvol 2012 Article ID 320582 8 pages 2012
[14] KWang R AMMauermayer and T F Eibert ldquoCompact two-element printedmonopole arraywith partially extended groundplanerdquo IEEE Antennas and Wireless Propagation Letters vol 13pp 138ndash140 2014
[15] J Park J Choi J-Y Park and Y-S Kim ldquoStudy of a T-shaped slot with a capacitor for high isolation between MIMOantennasrdquo IEEE Antennas andWireless Propagation Letters vol11 pp 1541ndash1544 2012
[16] M G N Alsath M Kanagasabai and B BalasubramanianldquoImplementation of slotted meander-line resonators for isola-tion enhancement in microstrip patch antenna arraysrdquo IEEEAntennas and Wireless Propagation Letters vol 12 pp 15ndash182013
[17] H Arun A K Sarma M Kanagasabai S Velan C Ravitejaand M G N Alsath ldquoDeployment of modified serpentinestructure for mutual coupling reduction in MIMO antennasrdquoIEEEAntennas andWireless Propagation Letters vol 13 pp 277ndash280 2014
[18] httpsenwikipediaorgwikiMCX connector[19] S Blanch J Romeu and I Corbella ldquoExact representation of
antenna system diversity performance from input parameterdescriptionrdquo Electronics Letters vol 39 no 9 pp 705ndash707 2003
[20] 3GPP ldquoEUTRA user equipment radio transmission and recep-tionrdquo 3GPP TS 36101 V830 September 2008
[21] L Song and J Shen Evolved Cellular Network Planning andOptimization for UMTS and LTE CRCPress London UK 2011
[22] M S Sharawi M U Khan A B Numan and D N Aloi ldquoACSRR loaded MIMO antenna system for ISM band operationrdquoIEEE Transactions on Antennas and Propagation vol 61 no 8pp 4265ndash4274 2013
[23] Y-L Ban J-H Chen J L-W Li and Y J Wu ldquoSmall-sizeprinted coupled-fed antenna for eight-band LTEGSMUMTSwireless wide area network operation in an internal mobilehandsetrdquo IET Microwaves Antennas amp Propagation vol 7 no6 pp 399ndash407 2013
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
8 International Journal of Antennas and Propagation
340
95
78
54
46
95
55
580
150
215
55
215
40
09
20
40
30
18
02
020418
06
10
33
xy
z
05
➃➄➅➆
➀➇
➁➂
(a)
20 22 24 26 28
Frequency (GHz)
minus10
minus5
0
minus15
minus20
minus25
minus30
minus35
Spa
ram
eter
s (dB
)
S11 simulationS22 simulationS33 simulationS44 simulation
S11 measurementS22 measurementS33 measurementS44 measurement
(b)
Isol
atio
n (d
B)
20 22 24 26 28
Frequency (GHz)
S12S13S14
S16S17S18
S15
minus10
minus15
minus20
minus25
minus30
minus35
minus40
minus45
minus50
(c)
0024
0020
0016
0012
0008
0004
0000
Cor
relat
ion
coeffi
cien
t
20 22 24 26 28 30
Frequency (GHz)
Antennas 1 and 2
Antennas 1 and 3
Antennas 1 and 4
Antennas 1 and 5
Antennas 1 and 6Antennas 1 and 7Antennas 1 and 8
(d)
Figure 14 (a) Geometry of the 8-element MIMO antenna system (b) Reflection coefficients of the MIMO antenna system (c) Measuredisolation between MIMO antenna elements (d) Correlation coefficient |120588| curves for the proposed MIMO antenna system
set as 33 and the loss tangent is 002 the same as [23] Figures16(b) and 16(c) show the influence of the plastic housing onreflection coefficients and isolation Differences between thetwo cases are small and acceptable and show this MIMOsystem is competitive for practical application
4 Conclusion
Symmetric planar monopole antenna for compact multiele-ment MIMO antenna systems is proposed Isolation higher
than 15 dB over the operating band is realized by using polar-ization diversity of the antenna elements Correlation coeffi-cient 119878-parameters radiation characteristics and acceptableperformance when placed with conductive plane and plastichousing show that the proposed antenna arrays can be usedfor practical MIMO applications
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
International Journal of Antennas and Propagation 9
Metal sheet(a)
20 22 24 26 28
Frequency (GHz)
minus10
minus5
0
minus15
minus20
minus25
minus30
minus35
Spa
ram
eter
s (dB
)
Without metal sheet1mm2mm
3mm4mm5mm
(b)
20 22 24 26 28
Frequency (GHz)
minus15
minus20
minus25
minus30
minus35
Isol
atio
n (d
B)
S12 and S211mm2mm
3mm4mm5mm
(c)
Figure 15 (a) Proposed MIMO antenna with a metal sheet sepa-rated by free space (b) Reflection coefficients of theMIMO antennasystemwith ametal sheet (c) Isolation of theMIMOantenna systemwith a metal sheet
Plastichousing
(a)
20 22 24 26 28
Frequency (GHz)
minus10
minus5
0
minus15
minus20
minus25
Spa
ram
eter
s (dB
)
S11 with plastic housingS11 without plastic housing
(b)
20 22 24 26 28
Frequency (GHz)
Isol
atio
n (d
B)
minus15
minus20
minus30
minus25
S12 and S21 with plastic housingS12 and S21 without plastic housing
(c)
Figure 16 (a) Proposed antenna with plastic housing (b) Reflectioncoefficients (c) Isolation
10 International Journal of Antennas and Propagation
Acknowledgment
This work was supported by the Priority Academic Pro-gram Development of Jiangsu Higher Education Institutions(PAPD)
References
[1] T Kokkinos E Liakou and A P Feresidis ldquoDecouplingantenna elements of PIFAarrays onhandheld devicesrdquoElectron-ics Letters vol 44 no 25 pp 1442ndash1444 2008
[2] H Li J Xiong Z Ying and S L He ldquoCompact and low profileco-locatedMIMO antenna structure with polarisation diversityand high port isolationrdquo Electronics Letters vol 46 no 2 pp108ndash110 2010
[3] S Zhang P Zetterberg and S He ldquoPrinted MIMO antennasystem of four closely-spaced elements with large bandwidthand high isolationrdquo Electronics Letters vol 46 no 15 pp 1052ndash1053 2010
[4] C Yang J Kim H Kim J Wee B Kim and C Jung ldquoQuad-band antenna with high isolation MIMO and broadbandSCS for broadcasting and telecommunication servicesrdquo IEEEAntennas and Wireless Propagation Letters vol 9 pp 584ndash5872010
[5] S Park and C Jung ldquoCompact MIMO antenna with highisolation performancerdquo Electronics Letters vol 46 no 6 pp390ndash391 2010
[6] H S Farahani M Veysi M Kamyab and A Tadjalli ldquoMutualcoupling reduction in patch antenna arrays using a UC-EBGsuperstraterdquo IEEE Antennas and Wireless Propagation Lettersvol 9 pp 57ndash59 2010
[7] G Exposito-Domınguez J M Fernandez-Gonzalez P Padillaand M Sierra-Castaner ldquoNew EBG solutions for mutual cou-pling reductionrdquo in Proceedings of the 6th European Conferenceon Antennas and Propagation (EUCAP rsquo12) pp 2841ndash2844IEEE Prague Czech Republic March 2012
[8] A Habashi J Nourinia and C Ghobadi ldquoA rectangulardefected ground structure (DGS) for reduction of mutualcoupling between closely-spaced microstrip antennasrdquo in Pro-ceedings of the 20th Iranian Conference on Electrical Engineering(ICEE rsquo12) pp 1347ndash1350 IEEE Tehran Iran May 2012
[9] L Wang and B Huang ldquoDesign of ultra-wideband MIMOantenna for breast tumor detectionrdquo International Journal ofAntennas and Propagation vol 2012 Article ID 180158 7 pages2012
[10] M Gallo E Antonino-Daviu M Ferrando-Bataller MBozzetti J M Molina-Garcia-Pardo and L Juan-Llacer ldquoAbroadband pattern diversity annular slot antennardquo IEEE Trans-actions on Antennas and Propagation vol 60 no 3 pp 1596ndash1600 2012
[11] D-G Kang J Tak and J Chio ldquoMIMO antenna with highisolation for WBAN applicationsrdquo International Journal ofAntennas and Propagation vol 2015 Article ID 370763 7 pages2015
[12] Y K Choukiker S K Sharma and S K Behera ldquoHybrid fractalshape planar monopole antenna covering multiband wirelesscommunications with MIMO implementation for handheldmobile devicesrdquo IEEE Transactions on Antennas and Propaga-tion vol 62 no 3 pp 1483ndash1488 2014
[13] Q Zeng Y Yao S Liu J Yu P Xie and X Chen ldquoTetrabandsmall-size printed strip MIMO antenna for mobile handset
applicationrdquo International Journal of Antennas and Propagationvol 2012 Article ID 320582 8 pages 2012
[14] KWang R AMMauermayer and T F Eibert ldquoCompact two-element printedmonopole arraywith partially extended groundplanerdquo IEEE Antennas and Wireless Propagation Letters vol 13pp 138ndash140 2014
[15] J Park J Choi J-Y Park and Y-S Kim ldquoStudy of a T-shaped slot with a capacitor for high isolation between MIMOantennasrdquo IEEE Antennas andWireless Propagation Letters vol11 pp 1541ndash1544 2012
[16] M G N Alsath M Kanagasabai and B BalasubramanianldquoImplementation of slotted meander-line resonators for isola-tion enhancement in microstrip patch antenna arraysrdquo IEEEAntennas and Wireless Propagation Letters vol 12 pp 15ndash182013
[17] H Arun A K Sarma M Kanagasabai S Velan C Ravitejaand M G N Alsath ldquoDeployment of modified serpentinestructure for mutual coupling reduction in MIMO antennasrdquoIEEEAntennas andWireless Propagation Letters vol 13 pp 277ndash280 2014
[18] httpsenwikipediaorgwikiMCX connector[19] S Blanch J Romeu and I Corbella ldquoExact representation of
antenna system diversity performance from input parameterdescriptionrdquo Electronics Letters vol 39 no 9 pp 705ndash707 2003
[20] 3GPP ldquoEUTRA user equipment radio transmission and recep-tionrdquo 3GPP TS 36101 V830 September 2008
[21] L Song and J Shen Evolved Cellular Network Planning andOptimization for UMTS and LTE CRCPress London UK 2011
[22] M S Sharawi M U Khan A B Numan and D N Aloi ldquoACSRR loaded MIMO antenna system for ISM band operationrdquoIEEE Transactions on Antennas and Propagation vol 61 no 8pp 4265ndash4274 2013
[23] Y-L Ban J-H Chen J L-W Li and Y J Wu ldquoSmall-sizeprinted coupled-fed antenna for eight-band LTEGSMUMTSwireless wide area network operation in an internal mobilehandsetrdquo IET Microwaves Antennas amp Propagation vol 7 no6 pp 399ndash407 2013
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
International Journal of Antennas and Propagation 9
Metal sheet(a)
20 22 24 26 28
Frequency (GHz)
minus10
minus5
0
minus15
minus20
minus25
minus30
minus35
Spa
ram
eter
s (dB
)
Without metal sheet1mm2mm
3mm4mm5mm
(b)
20 22 24 26 28
Frequency (GHz)
minus15
minus20
minus25
minus30
minus35
Isol
atio
n (d
B)
S12 and S211mm2mm
3mm4mm5mm
(c)
Figure 15 (a) Proposed MIMO antenna with a metal sheet sepa-rated by free space (b) Reflection coefficients of theMIMO antennasystemwith ametal sheet (c) Isolation of theMIMOantenna systemwith a metal sheet
Plastichousing
(a)
20 22 24 26 28
Frequency (GHz)
minus10
minus5
0
minus15
minus20
minus25
Spa
ram
eter
s (dB
)
S11 with plastic housingS11 without plastic housing
(b)
20 22 24 26 28
Frequency (GHz)
Isol
atio
n (d
B)
minus15
minus20
minus30
minus25
S12 and S21 with plastic housingS12 and S21 without plastic housing
(c)
Figure 16 (a) Proposed antenna with plastic housing (b) Reflectioncoefficients (c) Isolation
10 International Journal of Antennas and Propagation
Acknowledgment
This work was supported by the Priority Academic Pro-gram Development of Jiangsu Higher Education Institutions(PAPD)
References
[1] T Kokkinos E Liakou and A P Feresidis ldquoDecouplingantenna elements of PIFAarrays onhandheld devicesrdquoElectron-ics Letters vol 44 no 25 pp 1442ndash1444 2008
[2] H Li J Xiong Z Ying and S L He ldquoCompact and low profileco-locatedMIMO antenna structure with polarisation diversityand high port isolationrdquo Electronics Letters vol 46 no 2 pp108ndash110 2010
[3] S Zhang P Zetterberg and S He ldquoPrinted MIMO antennasystem of four closely-spaced elements with large bandwidthand high isolationrdquo Electronics Letters vol 46 no 15 pp 1052ndash1053 2010
[4] C Yang J Kim H Kim J Wee B Kim and C Jung ldquoQuad-band antenna with high isolation MIMO and broadbandSCS for broadcasting and telecommunication servicesrdquo IEEEAntennas and Wireless Propagation Letters vol 9 pp 584ndash5872010
[5] S Park and C Jung ldquoCompact MIMO antenna with highisolation performancerdquo Electronics Letters vol 46 no 6 pp390ndash391 2010
[6] H S Farahani M Veysi M Kamyab and A Tadjalli ldquoMutualcoupling reduction in patch antenna arrays using a UC-EBGsuperstraterdquo IEEE Antennas and Wireless Propagation Lettersvol 9 pp 57ndash59 2010
[7] G Exposito-Domınguez J M Fernandez-Gonzalez P Padillaand M Sierra-Castaner ldquoNew EBG solutions for mutual cou-pling reductionrdquo in Proceedings of the 6th European Conferenceon Antennas and Propagation (EUCAP rsquo12) pp 2841ndash2844IEEE Prague Czech Republic March 2012
[8] A Habashi J Nourinia and C Ghobadi ldquoA rectangulardefected ground structure (DGS) for reduction of mutualcoupling between closely-spaced microstrip antennasrdquo in Pro-ceedings of the 20th Iranian Conference on Electrical Engineering(ICEE rsquo12) pp 1347ndash1350 IEEE Tehran Iran May 2012
[9] L Wang and B Huang ldquoDesign of ultra-wideband MIMOantenna for breast tumor detectionrdquo International Journal ofAntennas and Propagation vol 2012 Article ID 180158 7 pages2012
[10] M Gallo E Antonino-Daviu M Ferrando-Bataller MBozzetti J M Molina-Garcia-Pardo and L Juan-Llacer ldquoAbroadband pattern diversity annular slot antennardquo IEEE Trans-actions on Antennas and Propagation vol 60 no 3 pp 1596ndash1600 2012
[11] D-G Kang J Tak and J Chio ldquoMIMO antenna with highisolation for WBAN applicationsrdquo International Journal ofAntennas and Propagation vol 2015 Article ID 370763 7 pages2015
[12] Y K Choukiker S K Sharma and S K Behera ldquoHybrid fractalshape planar monopole antenna covering multiband wirelesscommunications with MIMO implementation for handheldmobile devicesrdquo IEEE Transactions on Antennas and Propaga-tion vol 62 no 3 pp 1483ndash1488 2014
[13] Q Zeng Y Yao S Liu J Yu P Xie and X Chen ldquoTetrabandsmall-size printed strip MIMO antenna for mobile handset
applicationrdquo International Journal of Antennas and Propagationvol 2012 Article ID 320582 8 pages 2012
[14] KWang R AMMauermayer and T F Eibert ldquoCompact two-element printedmonopole arraywith partially extended groundplanerdquo IEEE Antennas and Wireless Propagation Letters vol 13pp 138ndash140 2014
[15] J Park J Choi J-Y Park and Y-S Kim ldquoStudy of a T-shaped slot with a capacitor for high isolation between MIMOantennasrdquo IEEE Antennas andWireless Propagation Letters vol11 pp 1541ndash1544 2012
[16] M G N Alsath M Kanagasabai and B BalasubramanianldquoImplementation of slotted meander-line resonators for isola-tion enhancement in microstrip patch antenna arraysrdquo IEEEAntennas and Wireless Propagation Letters vol 12 pp 15ndash182013
[17] H Arun A K Sarma M Kanagasabai S Velan C Ravitejaand M G N Alsath ldquoDeployment of modified serpentinestructure for mutual coupling reduction in MIMO antennasrdquoIEEEAntennas andWireless Propagation Letters vol 13 pp 277ndash280 2014
[18] httpsenwikipediaorgwikiMCX connector[19] S Blanch J Romeu and I Corbella ldquoExact representation of
antenna system diversity performance from input parameterdescriptionrdquo Electronics Letters vol 39 no 9 pp 705ndash707 2003
[20] 3GPP ldquoEUTRA user equipment radio transmission and recep-tionrdquo 3GPP TS 36101 V830 September 2008
[21] L Song and J Shen Evolved Cellular Network Planning andOptimization for UMTS and LTE CRCPress London UK 2011
[22] M S Sharawi M U Khan A B Numan and D N Aloi ldquoACSRR loaded MIMO antenna system for ISM band operationrdquoIEEE Transactions on Antennas and Propagation vol 61 no 8pp 4265ndash4274 2013
[23] Y-L Ban J-H Chen J L-W Li and Y J Wu ldquoSmall-sizeprinted coupled-fed antenna for eight-band LTEGSMUMTSwireless wide area network operation in an internal mobilehandsetrdquo IET Microwaves Antennas amp Propagation vol 7 no6 pp 399ndash407 2013
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
10 International Journal of Antennas and Propagation
Acknowledgment
This work was supported by the Priority Academic Pro-gram Development of Jiangsu Higher Education Institutions(PAPD)
References
[1] T Kokkinos E Liakou and A P Feresidis ldquoDecouplingantenna elements of PIFAarrays onhandheld devicesrdquoElectron-ics Letters vol 44 no 25 pp 1442ndash1444 2008
[2] H Li J Xiong Z Ying and S L He ldquoCompact and low profileco-locatedMIMO antenna structure with polarisation diversityand high port isolationrdquo Electronics Letters vol 46 no 2 pp108ndash110 2010
[3] S Zhang P Zetterberg and S He ldquoPrinted MIMO antennasystem of four closely-spaced elements with large bandwidthand high isolationrdquo Electronics Letters vol 46 no 15 pp 1052ndash1053 2010
[4] C Yang J Kim H Kim J Wee B Kim and C Jung ldquoQuad-band antenna with high isolation MIMO and broadbandSCS for broadcasting and telecommunication servicesrdquo IEEEAntennas and Wireless Propagation Letters vol 9 pp 584ndash5872010
[5] S Park and C Jung ldquoCompact MIMO antenna with highisolation performancerdquo Electronics Letters vol 46 no 6 pp390ndash391 2010
[6] H S Farahani M Veysi M Kamyab and A Tadjalli ldquoMutualcoupling reduction in patch antenna arrays using a UC-EBGsuperstraterdquo IEEE Antennas and Wireless Propagation Lettersvol 9 pp 57ndash59 2010
[7] G Exposito-Domınguez J M Fernandez-Gonzalez P Padillaand M Sierra-Castaner ldquoNew EBG solutions for mutual cou-pling reductionrdquo in Proceedings of the 6th European Conferenceon Antennas and Propagation (EUCAP rsquo12) pp 2841ndash2844IEEE Prague Czech Republic March 2012
[8] A Habashi J Nourinia and C Ghobadi ldquoA rectangulardefected ground structure (DGS) for reduction of mutualcoupling between closely-spaced microstrip antennasrdquo in Pro-ceedings of the 20th Iranian Conference on Electrical Engineering(ICEE rsquo12) pp 1347ndash1350 IEEE Tehran Iran May 2012
[9] L Wang and B Huang ldquoDesign of ultra-wideband MIMOantenna for breast tumor detectionrdquo International Journal ofAntennas and Propagation vol 2012 Article ID 180158 7 pages2012
[10] M Gallo E Antonino-Daviu M Ferrando-Bataller MBozzetti J M Molina-Garcia-Pardo and L Juan-Llacer ldquoAbroadband pattern diversity annular slot antennardquo IEEE Trans-actions on Antennas and Propagation vol 60 no 3 pp 1596ndash1600 2012
[11] D-G Kang J Tak and J Chio ldquoMIMO antenna with highisolation for WBAN applicationsrdquo International Journal ofAntennas and Propagation vol 2015 Article ID 370763 7 pages2015
[12] Y K Choukiker S K Sharma and S K Behera ldquoHybrid fractalshape planar monopole antenna covering multiband wirelesscommunications with MIMO implementation for handheldmobile devicesrdquo IEEE Transactions on Antennas and Propaga-tion vol 62 no 3 pp 1483ndash1488 2014
[13] Q Zeng Y Yao S Liu J Yu P Xie and X Chen ldquoTetrabandsmall-size printed strip MIMO antenna for mobile handset
applicationrdquo International Journal of Antennas and Propagationvol 2012 Article ID 320582 8 pages 2012
[14] KWang R AMMauermayer and T F Eibert ldquoCompact two-element printedmonopole arraywith partially extended groundplanerdquo IEEE Antennas and Wireless Propagation Letters vol 13pp 138ndash140 2014
[15] J Park J Choi J-Y Park and Y-S Kim ldquoStudy of a T-shaped slot with a capacitor for high isolation between MIMOantennasrdquo IEEE Antennas andWireless Propagation Letters vol11 pp 1541ndash1544 2012
[16] M G N Alsath M Kanagasabai and B BalasubramanianldquoImplementation of slotted meander-line resonators for isola-tion enhancement in microstrip patch antenna arraysrdquo IEEEAntennas and Wireless Propagation Letters vol 12 pp 15ndash182013
[17] H Arun A K Sarma M Kanagasabai S Velan C Ravitejaand M G N Alsath ldquoDeployment of modified serpentinestructure for mutual coupling reduction in MIMO antennasrdquoIEEEAntennas andWireless Propagation Letters vol 13 pp 277ndash280 2014
[18] httpsenwikipediaorgwikiMCX connector[19] S Blanch J Romeu and I Corbella ldquoExact representation of
antenna system diversity performance from input parameterdescriptionrdquo Electronics Letters vol 39 no 9 pp 705ndash707 2003
[20] 3GPP ldquoEUTRA user equipment radio transmission and recep-tionrdquo 3GPP TS 36101 V830 September 2008
[21] L Song and J Shen Evolved Cellular Network Planning andOptimization for UMTS and LTE CRCPress London UK 2011
[22] M S Sharawi M U Khan A B Numan and D N Aloi ldquoACSRR loaded MIMO antenna system for ISM band operationrdquoIEEE Transactions on Antennas and Propagation vol 61 no 8pp 4265ndash4274 2013
[23] Y-L Ban J-H Chen J L-W Li and Y J Wu ldquoSmall-sizeprinted coupled-fed antenna for eight-band LTEGSMUMTSwireless wide area network operation in an internal mobilehandsetrdquo IET Microwaves Antennas amp Propagation vol 7 no6 pp 399ndash407 2013
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
