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JOURNAL OF ELECTRONIC SCIENCE AND TECHNOLOGY OF CHINA, VOL. 7, NO. 2, JUNE 2009 185

A Compact Diversity Antenna for Handheld Terminals

Hai-Lin Xiao, Zai-Ping Nie, and Yu-Jing Wu

AbstractThe handheld terminals antenna should

have a small size, sufficient gain and big bandwidth. In

this paper, a compact planar inverted-L diversity

antenna for handheld terminals is proposed. Three

diversity antennas operating at 2.15GHz are designed

and the effect of important parameters of the proposed

antenna is measured. The isolation is found to be better

than 13 dB, the usable bandwidth is about 13%.

Moreover, the measured radiation patterns are alsoobtained that thebackward radiation is decreased.

Index TermsDiversity antenna, diversity gain,

isolation, radiation pattern.

1. IntroductionIn order to improve the quality of wireless downlink

signal, more than one antenna can be used at terminal side.

In these kinds of handheld terminals, two or more antenna

elements are envisaged and thus the limited space available

for antenna is an open issue. It is difficult to implement

multiple antennas on handheld terminal as small as a

handset. In [1], Yang Ding et al. introduced a novel

dual-band printed diversity antenna operating at UMTS

(1920MHz to 2170MHz) and 2.4-GHz WLAN (2400 MHz

to 2484 MHz), but it is too big for the small handheld

terminals. Dual-printed inverted-F antenna diversity

systems for terminal devices operating at 5.2GHz with both

switched and combing schemes were presented in [2].

However, the relatively large antenna volume and the

strong coupling between its two elements restrict its

application for handheld terminals. To date, there have been

considerable researched compacted antennas for handheld

terminals[3]-[5]. Many of these configurations are not

Manuscript received March 14, 2008; revised June 18, 2008. This work

was supported in part by the National Basic Research Program of China

973 under Grant No. 2008CB317109, Guangxi Science Foundation

under Grant No. 0991241, the Foundation of Guangxi Key laboratory of

Information and Communication under Grant No. 10903.

H.-L. Xiao is with the School of Information and Communication,

Guilin University of Electronic Technology, Guilin, 541004, China (e-mail:

xhl_xiaohailin@yahoo.com.cn).

Z.-P. Nie is with the School of Electronic Engineering, University of

Electronic Science and Technology of China, Chengdu, 610054, China.

Y.-J. Wu is with TongYu Communication Equipment Co.Ltd,

Zhongshan, 52847, China

suitable for handheld devices due to space limitation[6]-[8].

The basic requirements of the antenna elements at the

handheld terminals are low profile and low cost while

maintaining high bandwidth, good isolation and antenna

diversity employment.

Traditionally, monopole antennas are often used in

handheld terminals due to their low cost and attractive

bandwidth and radiation characteristics. However,

monopole antennas are easily damaged, due to theirnonrigid structure. Damage of the monopole antenna

accounts for approximately one half of faults in

vehicle-mounted cellular telephone use[9],[10]. Also, more

than half of the radiated power from a handset-mounted

monopole antenna may be absorbed in the users body

[11],[12]. The absorbed power is a potential health concern,

and it results in reduced antenna efficiency. A compact

planar inverted-L diversity antenna is an alternative to

monopole antennas that can be designed to reduce these

problems. It can be made conformal with the handset for

protection from damage.A compact planar inverted-L diversity antenna for

handheld terminals is proposed. The effect of important

parameters of the proposed antenna is measured and the

design methodology is described. Because back radiation is

suppressed through reasonable design, it can also be made

conformal with the handset for protection from users body

damage.

2. Handheld Terminals Antenna DesignThe planar inverted-L diversity antenna for handheldterminals is designed to operate at 2.15 GHz. The

configuration of one antenna element is illustrated in Fig. 1.

The diversity antenna consists of three ports fed by co-axial

cables. The antenna is mounted on the grounded FR4

substrate with dimension 42mm42mm1mm and relative

permittivity 4.26r = . Each antenna volume is only

00.14 0.1 0.06 ( 0 is vacuum wavelength).

There are three antenna elements, the antenna 1,

antenna 2 and 3, which are orthogonal, polarization

magnetic dipoles. In order to enhance the isolation between

antenna 1 and 3, two slots ( ) are designed on both

sides of the FR4 substrate as Fig. 2 (a) shows.

sW L s

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JOURNAL OF ELECTRONIC SCIENCE AND TECHNOLOGY OF CHINA, VOL. 7, NO. 2, JUNE 2009186

5W

4W

3W

2W

1W

3L

2L

1L

4L

3L

1W

(a) (b)

Radiating Slot

Ground

Capactive Load

Microstrip line

FR4 Substrate

(c)

Fig. 1. Construction of the diversity antenna elements: (a) plan

view, (b) folding view and (c) installation view.

y

x

fd cL

cW

ddS

sL

sW

Port1 P o rt 2 P or t3

ad

antenna 2

antenna

3

antenna1

(a)

Z

X

1Lh

1t=Ground Slot

3L

Microstrip line (b)

Fig. 2. Configuration of the proposed diversity antenna: (a) top

view and (b) side view.

Fig. 3. Photograph of the planar inverted-L diversity antenna.

To analyze the performance of the antenna scheme, it is

useful to define the initial dimensions of test-antenna

geometry. By optimizing the design, the final dimension of

the antenna is obtained: mm, ,1 8L = 3 9 mmL = 4L =

,5.5 mm d 8 mmf=

, c 1.5L=

, ,

o

45=

f 5d=

, cW=

,6.5 s 16W = , s 2.5L = , ,1 2 10 mmW W= = 6d= , ad =

,17 3 4 5 14 mmW W W= = = , (for antenna 1

and 3),

2 20 mmL =

221 mmL = (for antenna 2) , ,5 25 mmW = sL =

2.6 mm. From Fig. 2 and Fig. 3, the proposed diversity

antenna is characterized by compact size, no additional cost,

and easy manipulation.

Fig. 4. Measured S parameters of the diversity antenna.

Fig. 4 illustrates the measured S-parameters. It shows

that the usable bandwidth is about 13%, and the isolation is

below 13dB at the resonance frequency.The gain is about2 dB while the isolations between the designed antennas are

greater than 13

dB.

(a) (b)

(c) (d)

Fig. 5 Measured radiation patterns of the planar inverted-L

antenna at 2.15GHz, (solid line) co-polarization and (dotted line)

cross polarization: (a) E-plane radian pattern (antenna 1), (b)

H-plane radian pattern (antenna 1), (c) E-plane radian pattern(antenna 2), and (d) H-plane radian pattern (antenna 2).

5

10

15

20

1900 2000 2100 2200 2300 2400Frequency (MHz)

25

S11/S33

S13

S-parame

ters(dB)

S12/S32

S22

=0 (+z)

xoz plane

=0 (+z)=0 (+z)

=0 (+z)

90

(+y)90

(+x)090

yoz plane

90

(+y)90

(+x)

0 90

xoz planeyoz plane

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XIAO et al.: A Compact Diversity Antenna for Handheld Terminals 187

In this design, the antenna 3 has the same symmetric

geometry configuration as the antenna 1, and thus the two

antennas can be used to obtain space and radiation pattern

diversity. Moreover, the antenna 1 (or the antenna 3) and

the antenna 2 can be used to support three kinds of diversity

techniques, such as space diversity, radiation pattern

diversity and polarization diversity. From Fig. 5, it is

observed that the reduction of backward radiation is

obtained, because most of energy is radiated into +z

direction. The measured radiation patterns also show that

such design antenna is suitable for handheld terminals. The

proposed diversity antenna is characterized by compact size,

large bandwidth, omnidirectional radiation pattern, and

reduction of backward radiation. More importantly, it

supports the employment of diversity techniques.

3.

ConclusionsA planar inverted-L diversity antenna for handheld

terminals was proposed in this paper. The effects of

important parameters of the proposed antenna are discussed

and the design methodology is described. The proposed

diversity antenna has compact size, large bandwidth, high

isolation and gains, and reduction of backward radiation.

Moreover, it can be easily manipulated, and it can supports

three kinds of different diversity employment, and protects

from users body damage. The proposed diversity antenna

will be used on the user equipment side of MIMO systems.

References

[1] Y. Ding, Z. Du, K. Gong, and Z. Feng, A novel dual-band

printed diversity antenna for mobile terminals, IEEE Trans.

on Antennas and Propagation, vol. 55, no.7, pp. 2088-2096,

2007.

[2] M. Karaboikis, C. Soras, G. Tsachtsiris, et al., Compact

dual-printed inverted-F antenna diversity systems for portable

wireless devices, IEEE Antennas and Wireless Propagation

Letters, vol. 3, no. 1, pp. 9-14, 2004.

[3] S. B. Yeap, X. Chen, J. A. Dupuy, et al., Low profile

diversity antenna for MIMO applications,Electronics Letters,

vol. 42, no. 2, pp. 69-71. 2006.

[4] M. G. Douglas, M. Okoniewski, and M. A. Stuchly, A planar

diversity antenna for handheld PCS devices,IEEE Trans. on

Vehicular Technology,vol. 47, no. 3, pp. 747-754, 1998.

[5] J. O, Nielsen and G. F. Pedersen, Mobile handset

performance evaluation using radiation pattern

measurements, IEEE Trans. on Antennas and Propagation,

vol. 54, no. 7, pp. 2154-2165, 2006.

[6] S.-L. Wang, Z.-K. Dong, J. K. Ki, et al., Wideband planar

monopole antennas with dual band-notched characteristics,

IEEE Trans. on Microwave Theory and Techniques, vol. 54,

no. 6, pp. 2800-2806, 2006.

[7] K. Lan, S. K. Chaudhuri, and S. Safavi-Naeini, Design and

analysis of a combination antenna with rectangular dielectric

resonator and inverted L-plate,IEEE Trans. on Antennas and

Propagation, vol. 53, no. 1, pp. 495-501, 2005.

[8] J. E. Pallesen, O. Kim, and O Breinbjerg, Augmentation of

crossed-slot antenna with inverted-L wires for enhancement

of hemispherical coverage, Electronics Letters, vol. 42, no.

15, pp. 836-837, 2006.[9] M. A. Jensen and Y. Rahmat-Samii, The electronmagnetic

interaction between biological tissue and antennas on a

transceiver handset, in Proc. of IEEE AP-S International

Symposium Digest, Seattle, WA, USA, 1994, pp. 367-370.

[10] J. Tpftgard, S. Hornslet, and J. Bach Andersen, Effects on

portable antennas of the presence of a person, IEEE Trans.

Antennas Propagation, vol. 41, no. 6, pp. 739-746, 1993.

[11] T. H. Taminiau, F. B. Segerink, N. F. van Hulst, et al., A

monopole antenna at optical frequencies: single-molecule

near-field measurements, IEEE Trans. on Antennas and

Propagation, vol. 55, no. 11, pp. 3010-3017, 2007.

[12] J. H. Jung, H. Choo, and I. Park, Design and performance of

small electromagnetically coupled monopole antenna for

broadband operation,Microwaves, Antennas & Propagation,

vol. 1, no. 2, pp. 536-541, 2007.

Hai-Lin Xiao was born in Hubei Province,

China, in 1976. He received the B.S. from

Wuhan University in 1998, M.S. degrees from

Guangxi Normal University in 2004, and Ph.D.

degree from School of Electronic Engineering,

University of Electronic Science and

Technology of China (UESTC) in 2007. Now

he is an assistant professor in the School ofInformation and Communication, Guilin University of Electronic

Technology (GUET), His research interests include MIMO

wireless communication and smart antenna techniques.

Zai-Ping Nie was born in Shanxi Province,

China, in 1946. He received the B.S degree

and the M. S degree from UESTC, in 1968

and 1981 respectively. He is currently a full

professor with the Department of Microwave

Engineering, School of Electronic

Engineering, UESTC. His research interests

include electromagnetic radiation, scattering, inverse scattering,

wave and field in inhomogeneous media, computational

electromagnetics, smart antenna technique in mobile

communications and MIMO wireless communications.

Yu-Jiang Wu was born in Guangdong

Province, China, in 1971. He received the B.S,

M.S and Ph.D. degrees from University of

Electronic Science and Technology (UESTC)

in 1993, 2004 and 2007, respectively. Now he

is a manager of TongYu Communication

Equipment Co. Ltd, His research interests

include array signal processing, antenna

designs, and antenna numerical calculations.