A Low-Profile Dual-Polarized Magneto-Electric Dipole Antenna

DING, Chen; LUK, Kwai-Man

Published in:IEEE Access

Published: 01/01/2019

Document Version:Final Published version, also known as Publisher’s PDF, Publisher’s Final version or Version of Record

License:CC BY

Publication record in CityU Scholars:Go to record

Published version (DOI):10.1109/ACCESS.2019.2960125

Publication details:DING, C., & LUK, K-M. (2019). A Low-Profile Dual-Polarized Magneto-Electric Dipole Antenna. IEEE Access, 7,181924-181932. [8933367]. https://doi.org/10.1109/ACCESS.2019.2960125

Citing this paperPlease note that where the full-text provided on CityU Scholars is the Post-print version (also known as Accepted AuthorManuscript, Peer-reviewed or Author Final version), it may differ from the Final Published version. When citing, ensure thatyou check and use the publisher's definitive version for pagination and other details.

General rightsCopyright for the publications made accessible via the CityU Scholars portal is retained by the author(s) and/or othercopyright owners and it is a condition of accessing these publications that users recognise and abide by the legalrequirements associated with these rights. Users may not further distribute the material or use it for any profit-making activityor commercial gain.Publisher permissionPermission for previously published items are in accordance with publisher's copyright policies sourced from the SHERPARoMEO database. Links to full text versions (either Published or Post-print) are only available if corresponding publishersallow open access.

Take down policyContact lbscholars@cityu.edu.hk if you believe that this document breaches copyright and provide us with details. We willremove access to the work immediately and investigate your claim.

Download date: 13/05/2022

Received November 26, 2019, accepted December 12, 2019, date of publication December 16, 2019,date of current version December 26, 2019.

Digital Object Identifier 10.1109/ACCESS.2019.2960125

A Low-Profile Dual-Polarized Magneto-ElectricDipole AntennaCHEN DING 1, (Student Member, IEEE), AND KWAI-MAN LUK 1,2, (Fellow, IEEE)1Department of Electrical Engineering, City University of Hong Kong, Hong Kong2State Key Laboratory of Terahertz and Millimeter Wave, City University of Hong Kong, Hong Kong

Corresponding author: Kwai-Man Luk (eekmluk@cityu.edu.hk)

ABSTRACT Anovel low-profile dual-polarizedmagneto-electric dipole antennawith two choices of feedingprobes are proposed and investigated. The antenna utilizes a radiating structure which adopts equilateraltriangular cavities with small gaps as the magnetic dipole while maintaining the original rectangular planarpatches as the electric dipole, reducing the thickness to 0.15λ0 (where λ0 is the free-space wavelength atthe center frequency). Each type of the feeding probe has its own merit and demerit in terms of mechanicalrobustness, performance and assembly tolerance.Measurement results show that the prototypes achieve wideimpedance bandwidth of 48% (SWR < 2), high gain (7.7 to 11 dBi) and unidirectional radiation patternswith low cross-polarizations (< −22dB) and back-radiation level.

INDEX TERMS Low profile, magneto-electric dipole, unidirectional patterns, wideband antennas, dual-polarized antennas.

I. INTRODUCTIONFast evolving wireless communication systems requiresmaller antennas with better performances in terms of band-width, gain and radiation patterns. Conventional designs suchas horn, log-periodic and reflector antenna are incompatiblewith most modern wireless communication systems due totheir bulky structure [1]. Microstrip patch antennas have beenwidely used for its low profile and convenience of fabrica-tion. To cope with their major limit in narrow bandwidth,many techniques have been studied, such as aperture-coupledfeed [2]–[4], capacitive feed [5], L-probe [6], M-probefeed [7]–[9] and high-order mode [10]–[13]. However, thesedesigns have one or more disadvantages of large area, largegain variation, high cross polarization and high back radia-tion. Therefore, compactness, bandwidth and radiation prop-erties need to be considered simultaneously during designingprocess.

In 2006, Wong and Luk developed a new kind of comple-mentary antenna called magneto-electric (ME) dipole whichcombines a shorted patch antenna with an electric dipole [14].This type of antenna possesses advantages of wide band-width, high gain, low cross polarization and low backloberadiation. However, a noticeable shortcoming of the ME

The associate editor coordinating the review of this manuscript and

approving it for publication was Kwok L. Chung .

dipole is its relatively large thickness of around 0.25λ0, result-ing in inconvenience in practical applications. Throughoutyears, a series of studies have been done to lower downthe thickness of linearly polarized ME dipole to less than0.1λ0 [15]–[22].

Linearly polarized ME dipole antenna was later expandedto dual polarization [23]–[26]. Similar to linearly polarizeddesigns, dual-polarized ME dipole exhibits wide bandwidthand good unidirectional radiation properties for both ports.However, the antennas kept the same height of 0.25λ0 to theoriginal linearly polarized design and few efforts have beendone to lower the thickness for dual polarization. In 2016, Laideveloped a dual-polarized dual complementary source ME(DCS-ME) dipole antenna with thickness of 0.192λ0 usingdual open-ended slot excitation [27]. Such design brings sig-nificant impairment to the radiation characteristics includingthe cross-polarization level. The design in [28] has a 0.16λ0thickness for the radiating element yet requires cavity wallsof 0.37λ0 in height.

In this paper, a new ME dipole with low profile with twooptions of feeding probes are presented. The design abandonsthe shorted patch as the source of magnetic current. Instead,it adopts equilateral triangular cavity with small gap to actas the magnetic dipole, reducing the thickness from 0.25λ0to 0.15λ0 by 40%. Such modification does not result inimpairing performance inherited from the original ME dipole

181924 This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see http://creativecommons.org/licenses/by/4.0/ VOLUME 7, 2019

C. Ding, K.-M. Luk: Low-Profile Dual-Polarized ME Dipole Antenna

FIGURE 1. Operating principle of (a) the original dual-polarized ME dipoleantenna with vertical shorted patch and (b) the proposed low-profiledual-polarized ME dipole with triangular cavities (with dual 0-probes).(c) The equivalent circuit of a single polarization in the proposed antenna.

antenna in terms of bandwidth and radiation properties. Twokinds of structures are provided to form the feeding probe ofthe antenna.

This paper is organized as follows. Section II presents theprinciple of the radiating components of the dual-polarizedME dipole antenna. Section III and IV introduce the geome-try, working principle and performance of dual-polarized MEdipoles with dual 0-probes and flat 0-probes, respectively.Comparison and discussion between two types of feedingstructures are presented in Section V. A parametric study forseveral crucial parameters is conducted in Section VI. Finally,the conclusion is given in Section VII.

II. PRINCIPLE OF OPERATIONThe original design of linearly polarized ME dipole [14]was interpreted as a combination of electric dipole and mag-netic dipole placed orthogonally to each other. The electricdipole is constructed by a horizontal planar half-wave dipolewhile the magnetic dipole is realized by a shorted quarter-wavelength patch antenna. Similar configuration was foundin the dual-polarized case, as shown in Fig. 1(a). The feeding

TABLE 1. Dimensions for the proposed antenna with dual 0-probes.

probes are omitted for the convenience of demonstration.The two orthogonal gaps intersected in the middle cut thehorizontal dipole plates and vertical shorted patches into fourbi-symmetric parts. The whole radiating components couldbe illustrated as two complementary feeding sources withthe same phase. Each source is composed of an electric anda magnetic current orthogonal to each other. The relativelylarge thickness mainly results from the vertically placed mag-netic dipole. Therefore, the direction of reducing the heightshould be focused on improving the magnetic dipole.

The radiation of a shorted quarter-wavelength patchantenna as the magnetic dipole is mainly from the open end,by the classical cavity model theory. The open end couldbe treated as the virtual magnetic current, which could alsobe generated by an equilaterally triangular metallic cavity ofλ0/2 perimeter with open end at one of its vertex, as shownin [29]. Inspired by this idea, the magnetic dipoles in dualpolarized ME dipole could also be replaced by a pair oftriangular cavities located orthogonally, as shown in Fig. 1(b).The feeding probes are omitted and will be illustrated withdetail in section III and IV. Each triangular cavity is desig-nated to serve one polarization. The metallic walls of twocavities are connected to each other in the central intersection.The electric dipoles remain unchanged and connected to thetriangular cavity in the central gap. By applying this config-uration, the thickness of dual-polarized ME dipole could bereduced from 0.25λ0 to 0.15λ0 by 40%. The equivalent circuitis shown in Fig. 1(c). The impedance formula could be foundin [30]. No metamaterial [31], [32] is deployed for thicknessreduction since this work focuses on structural evolution.

III. DUAL-POLARIZED ME DIPOLE ANTENNAWITH DUAL 0-PROBESA. ANTENNA GEOMETRYThe geometry of the proposed dual-polarized ME dipoleantenna with dual 0-probes is illustrated in Fig. 1. All partsof the design are made of metal. The ground plane is madeof aluminum with thickness of 2 mm, while all other partsexcept the connectors are made of brass plates with thicknessof 0.2 mm. All dimensions of the proposed design, whichare optimized by simulation using High Frequency StructureSimulator (HFSS), are shown in Table 1.

VOLUME 7, 2019 181925

C. Ding, K.-M. Luk: Low-Profile Dual-Polarized ME Dipole Antenna

FIGURE 2. Geometry of the proposed dual-polarized ME dipole antennawith dual 0-probes in prospective view and side view.

The structure of the radiating element is described insection II. There are four radiating parts in total, locatedbisymmetrically around the central axis. The bottoms of theradiating elements are fixed to the ground plane by screws.The size of the ground plane is 1λ0× 1λ0, where λ0 refers tothe free-space wavelength at the centre frequency.

The two feeding probes are located orthogonally inside thetriangular cavities formed by slanted walls and the ground.Each probe is soldered to the inner conductor of the SMAconnector in the lower center. From the connection point,it divides into two opposite microstrip lines with character-istic impedance of 100 Ohms. At the end of the microstripline, it is connected to two 0-shaped flat strips. The croppedcorners at 90-degree bends of probes are the same as those inmicrostrip line bends. The upper horizontal parts of the twoprobes are different in height so the two ports are isolated.When the probe is near the triangular cavity, the gap betweenthem is 2 mm.

Each probe could be treated as three parts in the perspec-tive of circuit. The first part is the microstrip line whichtransmits the energy from the SMA connector. The sec-ond part, which acts as a balun, is the portion that passesthrough the gap between the opposing triangular cavities.The third part is at the end of 0-shaped flat strip, acting asa capacitor and coupling energy from probe to the nearbywalls.

B. WORKING PRINCIPLEDuring operation, signals are launched into the two dual0-shaped probes through the two SMA connectors. For eachpolarization, the signal is then divided into two branches and

FIGURE 3. Current distributions on the upper patches and electric fieldsin the gaps of the proposed dual-polarized ME dipole antenna with dual0-probes. (a) Port 1. (b) Port 2.

carried by the microstrip line formed by the brass strip andthe adjacent ground or slanted walls. This microstrip linewith 3.2 mm strip width and 2 mm strip-ground distance hascharacteristic impedance of 100Ohms. The signal then passesthrough the crossed gap which acts as a balun and excites thehorizontal planar dipoles and triangular cavities at the sametime.

The benefit of complementary antenna such as wide band-width and good unidirectional radiation pattern results fromthe electric dipole and magnetic dipole excited simultane-ously with similar amplitude. To further investigate the oper-ating principle of the proposed antenna, the simulated currentdistributions on the antenna surface and the electric fieldsin the gaps between upper patches for both ports at differ-ent phases of the center frequency are analyzed as shownin Fig. 3. At time t = 0, the currents on the horizontalpatches reach maximum strength, whereas the electric fieldsin the gaps between patches attain minimum strength. Thisindicates that the electric currents in the electric dipole andthe magnetic currents in the magnetic dipole reach maximummagnitude at the same time. At time t = T/4, where Tis one period of the operation, the currents on the horizon-tal patches attain minimum strength, whereas the electricfields in the gaps between patches reach maximum strength.This indicates that both the electric currents in the electricdipole and the magnetic currents in the magnetic dipole attainminimum. These results show that two degenerate modesof similar magnitude in strength are excited on the planardipole (electric dipole) and the gaps of the triangular cavities

181926 VOLUME 7, 2019

C. Ding, K.-M. Luk: Low-Profile Dual-Polarized ME Dipole Antenna

FIGURE 4. Fabricated prototype of proposed dual-polarized ME dipoleantenna with dual 0-probes.

FIGURE 5. Simulated and measured SWRs and gains of the proposeddual-polarized ME dipole antenna with dual 0-probes.

(magnetic dipole) simultaneously. Therefore, this structurecould be interpreted as a complementary source.

C. ANTENNA PERFORMANCEA prototype of the antenna as shown in Fig. 4 was fabri-cated to verify the proposed design. Measurement of SWRsand port isolations were accomplished using an AgilentE5071C network analyzer. Radiation patterns and antennagains were measured by a Satimo Starlab near-field measure-ment system.

Simulated and measured SWRs along with the gains areshown in Fig. 5. The measured impedance bandwidths are48% (SWR < 2) from 1.22 to 2 GHz for both ports. Theoperating frequency ranges for the two ports are slightlydifferent due to the unequal heights of the two orthogonalprobes. When compared to the simulation, the operating fre-quency bands for both ports are shifted to higher frequencydue to fabrication error. Within operating frequency range,the measured boresight gain varies from 8.1 to 10.6 dBi andfrom 7.9 to 11 dBi for port 1 and 2, respectively. Nearly iden-tical antenna gains are obtained for the two ports due to thebisymmetrical geometry of the proposed design. As shown

FIGURE 6. Simulated and measured port isolation of the proposeddual-polarized ME dipole antenna with dual 0-probes.

FIGURE 7. Simulated and measured radiation patterns for port 1 of theproposed antenna with dual 0-probes.

in Fig. 6, the measured isolation between the two ports islarger than 28 dB over the operating frequency range, whichis agrees well with the simulation.

The measured and simulated radiation patterns at1.2, 1.6 and 2GHz for port 1 and 2 are depicted in Fig. 7 and 8,respectively. Good agreement between measurement and

VOLUME 7, 2019 181927

C. Ding, K.-M. Luk: Low-Profile Dual-Polarized ME Dipole Antenna

FIGURE 8. Simulated and measured radiation patterns for port 2 of theproposed antenna with dual 0-probes.

TABLE 2. measured 3-dB beamwidth of the proposed antenna with dual0-probes.

simulations is achieved. The antenna exhibits good uni-directional radiation characteristic. The measured cross-polarization levels for two ports are below −24 dB in bothE- and H-plane. The measured front-to-back ratios are over12 dB over the operating frequency range. The measured3-dB beamwidth for both ports are listed in Table 2. The 3-dBbeamwidth in both E- and H-planes decreases with frequencydue to the electrical size of the antenna and the ground planeas the reflector.

IV. DUAL-POLARIZED ME DIPOLE ANTENNA WITHFLAT 0-PROBESA. ANTENNA GEOMETRYThe geometry of the dual-polarized ME dipole antenna withflat 0-probes is illustrated in Fig. 9. All designs are the sameto the previous antenna except for the structure of the two

TABLE 3. Dimensions for the proposed flat 0-probes.

FIGURE 9. Geometry of the proposed dual-polarized ME dipole antennawith flat 0-probes in prospective view and side view.

probes. All dimensions of the proposed design, which areoptimized by simulation, are shown in Table 3.

The two feeding probes are located orthogonally insidethe triangular cavities, as in the dual 0-probes design. Thelower middle part of each probe is soldered to the centralcore of SMA connector. The probe is originally flat withtwo trapezoidal parts at the sides and one rectangular partin the middle and is bent to 0-shape at the two junctionsbetween the rectangle and the two trapezoids. The brass stripof the probe, together with two adjacent slant walls, formsa modified stripline structure with the strip perpendicular tothe ground and the strip width changes with the cavity width.The surfaces of adjacent metallic walls perform as the groundplanes and the middle probe strip transmits the signal. Thegap distance between the probe strip and the triangular cavityis 1.2 mm. The middle horizontal parts of the two probes aredifferent in height so the two ports are isolated.

Each probe could be treated as three parts in the perspectiveof circuit. The first part is the transmission line which trans-mits the energy along the gap between the edge of the flat0-probe and the triangular cavity from the SMA connector.The second part, which acts as a balun, is the portion thatpasses through the gap formed by opposing triangular cavi-ties. The third part is at the end of 0-shaped flat probe whose

181928 VOLUME 7, 2019

C. Ding, K.-M. Luk: Low-Profile Dual-Polarized ME Dipole Antenna

FIGURE 10. Fabricated prototype of flat 0-probes soldered to the SMAconnectors.

gap with the triangular cavity acts as a capacitor and couplesenergy to the radiating elements.

B. WORKING PRINCIPLEDuring operation, signals are launched into two flat 0-shapedprobes through the two SMA connectors. For each polar-ization, the signal is then transmitted through the modifiedstripline with varying strip width formed by the flat strip andthe surfaces of adjacent triangular cavity. The signal thenpasses through the intersection between the two triangularcavities which acts as a balun and excites the horizontal planardipoles and triangular cavities at the same time. The workingprinciples of the radiating elements are the same with theprevious antenna design with dual 0-probes.

C. ANTENNA PERFORMANCEA prototype of the antenna was fabricated to verify theproposed design. The fabricated flat 0-probes are shown inFig. 10. Measurement of SWRs, port isolations, radiationpatterns and antenna gains were accomplished by the sameinstruments used by the previous design. Measured antennaperformances are also similar to the previous design.

V. COMPARISON BETWEEN TWO TYPES OF PROBESThe two types of probes adopted in the design of the low-profileMEdipole antenna have different operating principles,performances and mechanical structures. The cross sectionof the electric fields between the probes and the triangularcavity for two types of probes are shown in Fig. 11. Theedge of dual 0-probe works as a standard microstrip linewith gap g1 = 2mm. The characteristic impedances of thismicrostrip line is around 100 Ohms. The flat 0-probe worksas a modified stripline structure with the strip perpendicularto the ground and gap g2 = 1.2 mm. The strip width changeswith the triangular cavity. Each type of the probes has its ownmerits and demerits in different aspects. Mechanically, theflat0-probe is more robust due to simpler structure and largerarea. In comparison, the dual 0-probe is more susceptibleto vibration and deformation, resulting from its long andthin metal strips. On the other hand, the dual 0-probe is

FIGURE 11. Cross Section of electric fields around probes for (a) MEdipole antenna with dual 0-probes and (b) proposed ME dipole antennawith flat 0-probes.

more tolerant to assembly error than the flat 0-probe, sincethe gap distance g1 is much larger than g2. For more stablefixture of the probes, light foams could be applied to fix theprobes against vibration and deformation without affectingthe performance.

VI. PARAMETRIC STUDYIn order to investigate the effect of parameter dimensions onthe performance of the antenna design, a parametric studywas performed by simulation. Since the performance of theantenna with two proposed probes are similar, only the designin Section III is used in the simulation.

A. ELECTRIC DIPOLETo study the effect of the electric dipole on the antenna perfor-mance, the edge lengths of the rectangular patches, L1 and L2,were studied. Fig. 12 shows the effect on SWR and gain byvarying L1 for both ports with L2 fixed. It can be observed thatby increasing L1, the impedance matching becomes worseand the first resonance of port 1 is shifted to a lower frequencywhile a fixed second resonance occurs at around 1.65 GHz.This phenomenon indicates that the first resonance is formedby the electric dipole. The local peaks of the gain curve movewith the resonance point. The performance of port 2 is lessaffected by L1. Fig. 13 shows the effect on SWR and gain byvarying L2 for both ports with L1 fixed. Compared to Fig. 12,the effect on port 1 and port 2 are interchanged since L1 is thelength of the electric dipole of port 1 while L2 is the length ofthe electric dipole of port 2. To balance between impedancebandwidth and impedance matching, L1 and L2 were chosento be 50 mm and 49 mm, respectively.

B. MAGNETIC DIPOLEThe vertical height of the slanted walls under the rectangularpatches H was studied firstly. It can be seen from Fig. 14 thatby increasing H, the impedance matching becomes worse andthe second resonances of both port 1 and port 2 are shifted to

VOLUME 7, 2019 181929

C. Ding, K.-M. Luk: Low-Profile Dual-Polarized ME Dipole Antenna

FIGURE 12. Effect of the edge length L1 of the electric dipole.

FIGURE 13. Effect of the edge length L2 of the electric dipole.

FIGURE 14. Effect of the wall height H of the magnetic dipole.

a lower frequency while a fixed resonance occurs at around1.25 GHz. This indicates that the second resonance is formedby themagnetic dipole. It could be noticed that the impedancematching in the middle part of the operating band will dete-riorate if the two resonant frequencies are far away fromeach other. Separation of the two resonances of electric andmagnetic dipoles will defeat the purpose of complementarysources and create two separate frequency bands instead of a

FIGURE 15. Effect of the wall width W of the magnetic dipole.

FIGURE 16. Effect of the edge size GL of the ground reflector.

coherent wide band. And yet two overlapped resonances willresult in a narrow usable band. Therefore, H was chosen to be28 mm.

Fig. 15 shows the impact to antenna performance by widthof the slanted wall W, while keeping wall height H andinclination angle constant. The impedance matching and gainare sensitive to the value of W. Relatively small W will resultin impedance mismatch while relatively large W will narrowthe impedance bandwidth. Hence, W should be neither toolarge nor too small and was chosen to be 26mm.

C. METALLIC REFLECTORThe metallic ground acts as a reflector, making the antennaradiate unidirectionally. Fig. 16 show the simulated SWRand front-to-back ratio for different ground size GL. It canbe observed that the ground length has minor effect on theimpedance matching of the antenna. However, it greatlyaffects the front-to-back ratio since the metallic groundreflects the energy to boresight and reduce the backloberadiation. As the ground size GL increases, the front-to-back ratio becomes larger. However, the antenna size cannotbe infinitely large due to the requirement of compactness.

181930 VOLUME 7, 2019

C. Ding, K.-M. Luk: Low-Profile Dual-Polarized ME Dipole Antenna

Thus, the ground length GL was chosen to be 190 mm, whichis exactly 1λ0.

VII. CONCLUSIONA novel low-profile dual-polarized magneto-electric dipoleantenna with two choices of feeding probes has been pro-posed and investigated in this paper. The antenna designhas a radiating structure which adopts equilateral triangularcavity with small gap on the top as the magnetic dipolewhile keeping the original rectangular planar patches as theelectric dipole, reducing the antenna thickness to 0.15λ0.Each type of the feeding probe has its own merit and demeritin terms of mechanical robustness, performance and assem-bly tolerance. Measurement result shows that the low-profileME dipole with dual 0-probes has impedance bandwidthof 48% (SWR < 2) from 1.22 to 2 GHz for both ports withport isolation more than 28 dB. Within operating frequencyrange, its measured boresight gain varies from 8.1 to 10.6 dBiand from 7.9 to 11 dBi for port 1 and 2, respectively. Theantenna design with flat 0-probes has a similar performance.Both designs have excellent unidirectional radiation patternswith low cross-polarizations (< −23 dB) and back-radiationlevel. With low profiles and good electrical characteristics,the proposed antenna will find applications in various wire-less communication systems.

ACKNOWLEDGMENTThe authors would like to thank C. Y. Lau and C. K. Lau forassisting in fabrication process.

REFERENCES[1] C. A. Balanis,Antenna Theory: Analysis andDesign. NewYork, NY, USA:

Wiley, 2005.[2] Y. Zhang, K. Wei, Z. Zhang, and Z. Feng, ‘‘A broadband patch antenna

with tripolarization using quasi-cross-slot and capacitive coupling feed,’’IEEE Antennas Wireless Propag. Lett., vol. 12, pp. 832–835, 2013.

[3] W. M. Abdel-Wahab and S. Safavi-Naeini, ‘‘Wide-bandwidth 60-GHzaperture-coupled microstrip patch antennas (MPAs) fed by substrate inte-grated waveguide (SIW),’’ IEEE Antennas Wireless Propag. Lett., vol. 10,pp. 1003–1005, 2011.

[4] K. L. Wong, H. C. Tung, and T. W. Chiou, ‘‘Broadband dual-polarizedaperture-coupled patch antennas with modified H-shaped coupling slots,’’IEEE Trans. Antennas Propag., vol. 50, no. 2, pp. 188–191, Feb. 2002.

[5] J.-D. Zhang, L. Zhu, Q.-S. Wu, N.-W. Liu, and W. Wu, ‘‘A com-pact microstrip-fed patch antenna with enhanced bandwidth and har-monic suppression,’’ IEEE Trans. Antennas Propag., vol. 64, no. 12,pp. 5030–5037, Dec. 2016.

[6] H. Wong, K.-L. Lau, and K.-M. Luk, ‘‘Design of dual-polarized L-probepatch antenna arrays with high isolation,’’ IEEE Trans. Antennas Propag.,vol. 52, no. 1, pp. 45–52, Jan. 2004.

[7] Z. N. Chen and M. Y. W. Chia, ‘‘Broad-band suspended probe-fedplate antenna with low cross-polarization levels,’’ IEEE Trans. AntennasPropag., vol. 51, no. 2, pp. 345–346, Feb. 2003.

[8] H.-W. Lai and K.-M. Luk, ‘‘Design and study of wide-band patch antennafed by meandering probe,’’ IEEE Trans. Antennas Propag., vol. 54, no. 2,pp. 564–571, Feb. 2006.

[9] H. Wong, Q. W. Lin, H. W. Lai, and X. Y. Zhang, ‘‘Substrate inte-grated meandering probe-fed patch antennas for wideband wirelessdevices,’’ IEEE Trans. Compon., Packag., Manuf. Technol., vol. 5, no. 3,pp. 381–388, Feb. 2015.

[10] N.-W. Liu, L. Zhu, X. Zhang, and W.-W. Choi, ‘‘A wideband differential-fed dual-polarized microstrip antenna under radiation of dual improvedodd-order resonant modes,’’ IEEE Access, vol. 5, pp. 23672–23680, 2017.

[11] N.-W. Liu, L. Zhu, and W.-W. Choi, ‘‘A differential-fed microstrip patchantenna with bandwidth enhancement under operation of TM10 and TM30Modes,’’ IEEE Trans. Antennas Propag., vol. 65, no. 4, pp. 1607–1614,Apr. 2017.

[12] N.-W. Liu, L. Zhu, W.-W. Choi, and J.-D. Zhang, ‘‘A low-profile aperture-coupled microstrip antenna with enhanced bandwidth under dual reso-nance,’’ IEEE Trans. Antennas Propag., vol. 65, no. 3, pp. 1055–1062,Mar. 2017.

[13] N.-W. Liu, L. Zhu, W.-W. Choi, and X. Zhang, ‘‘Wideband shorted patchantenna under radiation of dual-resonant modes,’’ IEEE Trans. AntennasPropag., vol. 65, no. 6, pp. 2789–2796, Jun. 2017.

[14] K.-M. Luk and H. Wong, ‘‘A new wideband unidirectional antenna ele-ment,’’ Int. J. Microw. Opt. Technol., vol. 1, no. 1, pp. 35–44, 2006.

[15] H. Wong, K. M. Mak, and K. M. Luk, ‘‘Wideband shorted bowtie patchantenna with electric dipole,’’ IEEE Trans. Antennas Propag., vol. 56,no. 7, pp. 2098–2101, Jul. 2008.

[16] L. Ge and K.-M. Luk, ‘‘A low-profile magneto-electric dipole antenna,’’IEEE Trans. Antennas Propag., vol. 60, no. 4, pp. 1684–1689,Apr. 2012.

[17] L. Ge and K. M. Luk, ‘‘A wideband magneto-electric dipole antenna,’’IEEE Trans. Antennas Propag., vol. 60, no. 11, pp. 4987–4991, Nov. 2012.

[18] M. J. Li and K. M. Luk, ‘‘A low-profile wideband planar antenna,’’ IEEETrans. Antennas Propag., vol. 61, no. 9, pp. 4411–4418, Sep. 2013.

[19] L. Ge and K. M. Luk, ‘‘A magneto-electric dipole antenna with low-profileand simple structure,’’ IEEE Antennas Wireless Propag. Lett., vol. 12,pp. 140–142, 2013.

[20] M. Li and K.M. Luk, ‘‘A low-profile, low-backlobe and wideband comple-mentary antenna for wireless application,’’ IEEE Trans. Antennas Propag.,vol. 63, no. 1, pp. 7–14, Jan. 2015.

[21] C. Ding and K. M. Luk, ‘‘Low-profile magneto-electric dipole antenna,’’IEEE Antennas Wireless Propag. Lett., vol. 15, pp. 1642–1644,2016.

[22] C. Ding and K. Luk, ‘‘Compact differential-fed dipole antenna with widebandwidth, stable gain and low cross-polarisation,’’ Electron. Lett., vol. 53,no. 15, pp. 1019–1021, Jul. 2017.

[23] B. Q. Wu and K. M. Luk, ‘‘A broadband dual-polarized magneto-electricdipole antenna with simple feeds,’’ IEEE Antennas Wireless Propag. Lett.,vol. 8, pp. 60–63, 2009.

[24] Q. Xue, S. W. Liao, and J. H. Xu, ‘‘A differentially-driven dual-polarizedmagneto-electric dipole antenna,’’ IEEE Trans. Antennas Propag., vol. 61,no. 1, pp. 425–430, Jan. 2013.

[25] Y. Gou, S. Yang, J. Li, and Z. Nie, ‘‘A compact dual-polarized printeddipole antenna with high isolation for wideband base station applica-tions,’’ IEEE Trans. Antennas Propag., vol. 62, no. 8, pp. 4392–4395,Aug. 2014.

[26] M. Li and K.-M. Luk, ‘‘Wideband magnetoelectric dipole antennas withdual polarization and circular polarization,’’ IEEE Antennas Propag. Mag.,vol. 57, no. 1, pp. 110–119, Feb. 2015.

[27] H. W. Lai, K. K. So, H. Wong, C. H. Chan, and K. M. Luk, ‘‘Magnetoelec-tric dipole antennas with dual open-ended slot excitation,’’ IEEE Trans.Antennas Propag., vol. 64, no. 8, pp. 3338–3346, Aug. 2016.

[28] A. S. Kaddour, S. Bories, A. Bellion, and C. Delaveaud, ‘‘Low profiledual-polarized wideband antenna,’’ in Proc. Int. Symp. Antennas Propag.(ISAP), 2016, pp. 86–87.

[29] K.-M. Luk and B.Wu, ‘‘The magnetoelectric dipole—Awideband antennafor base stations in mobile communications,’’ Proc. IEEE, vol. 100, no. 7,pp. 2297–2307, Jul. 2012.

[30] M. Li and K.-M. Luk, ‘‘Wideband magneto-electric dipole antennas,’’in Handbook Antenna Technologies. Singapore: Springer, 2015,pp. 1967–2019.

[31] B. Feng, L. Li, Q. Zeng, and C.-Y.-D. Sim, ‘‘A low-profile metamaterialloaded antenna arraywith anti-interference and polarization reconfigurablecharacteristics,’’ IEEE Access, vol. 6, pp. 35578–35589, 2018.

[32] B. Feng, K. L. Chung, J. Lai, and Q. Zeng, ‘‘A conformal magneto-electricdipole antenna with wide H-plane and band-notch radiation characteristicsfor sub-6-GHZ 5G base-station,’’ IEEE Access, vol. 7, pp. 17469–17479,2019.

VOLUME 7, 2019 181931

C. Ding, K.-M. Luk: Low-Profile Dual-Polarized ME Dipole Antenna

CHEN DING (S’16) was born in Weifang,Shandong, China. He received the B.S. degreein mathematics from The Chinese University ofHong Kong, in 2012, and the M.S. degree inelectronic and information engineering from theCity University of Hong Kong, in 2015, where heis currently pursuing the Ph.D. degree in electri-cal engineering with the Department of ElectricalEngineering.

He joined the industry as an Electronic andSoftware Engineer, from 2012 to 2014. From 2015 to 2016, he was aResearch Assistant with the State Key Laboratory of Millimeter-Waves,City University of Hong Kong. His current research interests include low-profile antennas, millimeter-wave antennas, circularly-polarized antennas,and antenna measurement methods. He is the First Prize Winner of BestStudent Paper Award at the IEEE International Symposium on Antennas andPropagation (AP-S 2019)whichwas held inAtlanta, USA, in 2019. He is alsothe Winner for the Best Student Paper Prize at the Asia-Pacific MicrowaveConference (APMC 2019) held in Singapore, in 2019.

KWAI-MAN LUK (M’79–SM’94–F’03) receivedthe B.Sc.Eng. and Ph.D. degrees in electricalengineering from The University of Hong Kong,in 1981 and 1985, respectively.

He joined the Department of Electronic Engi-neering, City University of Hong Kong, as aLecturer, in 1985. Two years later, he moved tothe Department of Electronic Engineering, TheChinese University of Hong Kong, where he spentfour years. In 1992, he returned to the City Uni-

versity of Hong Kong, where he served as the Head of the Department ofElectronic Engineering, from 2004 to 2010, and the Director of the State KeyLaboratory of Millimeter Waves, from 2008 to 2013, where he is currently

the Chair Professor of electronic engineering. He is the author of four books,11 research book chapters, over 360 journal articles, and 250 conferencearticles. His recent research interests include design of patch antennas,magneto-electric dipole antennas, dense dielectric patch antennas, and openresonator antennas for various wireless applications.

Prof. Luk is a Fellow of the UK Royal Academy of Engineering, theChinese Institute of Electronics, PRC, the Institution of Engineering andTechnology, U.K., the Institute of Electrical and Electronics Engineers, USA,and the Electromagnetics Academy, USA. He was awarded ten US andmore than ten PRC patents on the design of a wideband patch antennawith an L-shaped probe feed. He received the Japan Microwave Prize at the1994 Asia Pacific Microwave Conference held in Chiba, in December 1994,the Best Paper Award at the 2008 International Symposium on Antennasand Propagation held in Taipei, in October 2008, and the Best Paper Awardat the 2015 Asia-Pacific Conference on Antennas and Propagation held inBali, in July 2015. He was awarded the very competitive 2000 CroucherFoundation Senior Research Fellow in Hong Kong. He also received the2011 State Technological Invention Award (2nd Honor) of China. He wasa recipient of the 2017 IEEE APS John Kraus Antenna Award. He wasthe Technical Program Chairperson of the 1997 Progress in Electromag-netics Research Symposium (PIERS), the General Vice-Chairperson of the1997 and 2008 Asia-Pacific Microwave Conference (APMC), the GeneralChairman of the 2006 IEEE Region Ten Conference (TENCON), the Techni-cal Program Co-Chairperson of 2008 International Symposium on Antennasand Propagation (ISAP), and the General Co-Chairperson of 2011 IEEEInternational Workshop on Antenna Technology (IWAT), and the GeneralCo-Chair of 2014 IEEE International Conference on Antenna Measure-ments and Applications (CAMA) and the 2015 International Conferenceon Infrared, millimeter, and Terahertz Waves (IRMMW-THz 2015). He isalso the General Chair of the 2020 Asia-Pacific Microwave Conference tobe held in Hong Kong, in November 2020. He was the Chief Guest Editorfor a special issue on Antennas inWireless Communications published in theProceedings of the IEEE, in July 2012. He is also the Deputy Editor-in-Chiefof PIERS Journals and an Associate Editor of the IETMicrowaves, Antennasand Propagation.

181932 VOLUME 7, 2019