A Compact Dual-Band Dual-Polarized Patch Antenna

1936 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 51, NO. 8, AUGUST 2003

A Compact Dual-Band Dual-Polarized Patch Antennafor 900/1800-MHz Cellular Systems

Tzung-Wern Chiou and Kin-Lu Wong, Senior Member, IEEE

AbstractA novel compact design for achieving dual-banddual-polarized radiation suitable for applications in the900/1800-MHz cellular systems is presented. The proposedantenna consists of a rectangular ring patch (for the 900-MHzoperation) and a notched rectangular patch (for the 1800-MHzoperation), which are printed on the same layer, and each patch isaperture-coupled by two H-shaped coupling slots to generate twoorthogonal linearly polarized waves. By further incorporating aproperly designed feed network, the proposed antenna shows goodport decoupling of less than 39 dB and 34 dB for dual linearpolarizations in the 900- and 1800-MHz bands, respectively. De-tails of the antenna design and experimental results are presented.

Index TermsAntennas, dual-band antennas, dual-polarizedantennas, patch antennas.

I. INTRODUCTION

PATCH antennas capable of dual-polarized operations arevery suitable for applications in modern mobile communi-cation systems to combat the multipath fading problem, whichusually causes larger degradation in the system performance[1]. For such applications, a variety of dual-polarized patch an-tennas have also been reported recently [2][10] in which gooddual-polarized radiation over a wide bandwidth of about 10% orlarger and high isolation between the two feeding ports ( lessthan 30 dB) across the entire bandwidth have been achieved.These antennas, however, are mainly designed for single-bandoperation. Very few designs are reported for dual-band dual-polarized operations for mobile communication systems [11].For the reported design in [11], the dual-band dual-polarizedpatch antenna shows a 10-dB return-loss bandwidth coveringboth the 900-MHz (890960 MHz, GSM cellular system) and1800-MHz (17101880 MHz, DCS cellular system) frequencybands. Measured isolation less than 32 dB in both bandshas also been obtained. However, this antenna uses a structureof three stacked patches, and has a total height of aboutat 900 MHz.

In this paper, we propose a new compact dual-band dual-po-larized patch antenna suitable for the 900- and 1800-MHz bandoperations. The proposed antenna has two coplanar radiatingpatches, one rectangular-ring patch for the 900-MHz operationand one notched rectangular patch placed within the rectan-gular-ring patch for the 1800-MHz operation, and the total an-

Manuscript received December 12, 2000; revised March 21, 2001.T.-W. Chiou was with the Department of Electrical Engineering, National Sun

Yat-Sen University, Kaohsiung 804, Taiwan, R.O.C. He is now with PhycompTaiwan Limited, Kaohsiung 811, Taiwan, R.O.C.

K.-L. Wong are with the Department of Electrical Engineering, National SunYat-Sen University, Kaohsiung 804, Taiwan.

Digital Object Identifier 10.1109/TAP.2003.814728

tenna height is only about at 900 MHz. To feed the an-tenna, the aperture-coupled feed method is used. Four H-shapedcoupling slots are cut in the antennas ground plane to couplethe electromagnetic energy from the feed network to the two ra-diating patches. To obtain good port decoupling in both of the900- and 1800-MHz bands, these H-shaped coupling slots arecarefully oriented. The feed network is also designed such thatthe 1800-MHz signal into the radiating patch for the 900-MHzband operation (the rectangular-ring patch) is blocked, so is thecase for the 900-MHz signal into the radiating patch for the1800-MHz band operation (the notched rectangular patch). Inthis condition, the possible excitation of unwanted modes canbe suppressed, and easy impedance matching in both of the 900-and 1800-MHz bands can also be obtained. Details of the pro-posed antenna are described, and experimental results of thedual-band dual-polarized operation are presented.

II. ANTENNA CONFIGURATION AND DESIGN CONSIDERATIONSThere are four major parts in the design of the proposed an-

tenna shown in Fig. 1. The first two parts are the dimensionsdetermination of the rectangular-ring patch and notched rectan-gular patch for the 900- and 1800-MHz operations, respectively.As shown in Fig. 1(b), the two patches are printed on the samedielectric substrate (patch substrate), and the notched rectan-gular patch is placed within the rectangular-ring patch to obtaina compact structure. The third part is the arrangement of the cou-pling slots in the antennas ground plane [see Fig. 1(c)], and thefourth one is the feed network design [Fig. 1(d)]. The couplingslots and the feed network are printed on two sides of a dielectricsubstrate (feed substrate). In this study, both the patch and feedsubstrates used were inexpensive FR4 substrates of thickness0.8 mm and relative permittivity 4.4. The two substratesare also separated by an air layer of thickness [see Fig. 1(a);the supporting posts not shown in the figure]. The IE3D simula-tion software was helpful in obtaining proper parameters of theproposed antenna. The design considerations for the four majorparts are described in detail in the following subsection.

A. Rectangular-Ring Patch Design for the 900-MHzBand Operation

The rectangular-ring patch is designed for achieving the900-MHz band operation, and is aperture-coupled by usingtwo H-shaped coupling slots [slot 1X and slot 2Y in Fig. 1(c)]for obtaining dual linear polarizations. The two H-shaped slotshave a center arm of width 0.5 mm and two side arms of width1 mm. As for the lengths of the slots center arm and side arm,owing to the width limitation of the rectangular-ring patch, slot

0018-926X/03$17.00 2003 IEEE

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CHIOU AND WONG: COMPACT DUAL-BAND DUAL-POLARIZED PATCH ANTENNA 1937

(a)

(b)

(c)

(d)Fig. 1. Geometry of the proposed dual-band dual-polarized patch antenna;dimensions given in the figure are in millimeters. (a) Side view of the antenna.(b) Patches in layer 1. (c) Coupling slots in layer 2. (d) Microstrip-line feednetwork.

1X is designed to be narrow (i.e., a relatively shorter center armand a relatively longer side arm) and slot 2Y is with a wideH shape, having a relatively longer center arm and a relativelyshorter side arm. Also, since the coupling-slot size can affectthe resonant frequency of the antenna, the dimensions of therectangular-ring patch in parallel to the and axes are chosento be different to achieve the same operating frequencies around900 MHz. The designed patch dimensions are given in Fig. 1(b).

B. Notched Rectangular Patch Design for the 1800-MHzBand Operation

A notched rectangular patch is designed for the 1800-MHzband operation, and the designed patch dimensions are alsogiven in Fig. 1(b). By inserting a pair of slits (length and width1 mm) along the direction [see Fig. 1(b)], the side lengthof the notched rectangular patch along the direction can bereduced, which is helpful in obtaining a larger gap betweenthe notched rectangular patch and the rectangular-ring patch toreduce the possible coupling between the two radiating patches.In this study, it is found that a gap of 5 mm is required betweenthe two radiating patches. In this case, very small effects on themeasured return loss and port isolation of the proposed antennaare observed. Also, note that since the coupling slots (slot 2Xand slot 1Y) are arranged along the direction, no slits areintroduced in the notched rectangular patch in the directionto avoid the decreasing in the electromagnetic energy couplingfrom the feed line to the patch. For this reason, the requiredside length of the notched rectangular patch in the directionis larger than that in the direction. This also leads to a largerside length of the rectangular-ring patch in the direction thanin the direction.

C. Coupling Slots Arrangement in the Ground PlaneAll the H-shaped coupling slots (slots 1X, 1Y, 2X, and 2Y)

have the same slot widths (0.5 and 1 mm for the slots center armand side arm, respectively), and the lengths of the slots centerarms and side arms are given in Fig. 1(c). In order to obtainhigh port decoupling, slots 1X and 2Y for the 900-MHz bandoperation are arranged such that the center arm of slot 1X is inthe direction of the microstrip feed line of slot 2Y. For slots 1Yand 2X for the 1800-MHz band operation, the same arrangementis applied. In this case, high isolation between ports 1 and 2 isobtained for the proposed antenna.

D. Feed Network DesignIn addition to the coupling-slot arrangement described in part

C of this section, the feed network is also designed such thatthe 1800-MHz (900-MHz) signal into the rectangular-ring patch(notched rectangular patch) is blocked. In this condition, thepossible excitation of unwanted modes is suppressed, and easyimpedance matching of the proposed antenna in the 900- and1800-MHz bands is also obtained. To achieve this goal, the mi-crostrip-line feed network shown in Fig. 1(d) is designed. Thearrangement of the feed networks for ports 1 and 2 is the same.The characteristic impedance of all the microstrip-line sectionsin the feed network, except and sections, is chosen to be

. The parameters of the microstrip-line sections in



TABLE ILENGTH AND WIDTHS OF THE MICROSTRIP-LINE SECTIONS IN THE FEED NETWORK. (= 182:4 mm) IS THE GUIDED WAVELENGTH IN THE FEED SUBSTRATE AT

900 MHz, DETERMINED FROM =p" ( IS THE FREE-SPACE WAVELENGTH AND " IS THE EFFECTIVE RELATIVE PERMITTIVITY)

(a)

(b)Fig. 2. Measured return loss against frequency; ` = 13 mmground plane size = 150 150 mm . Other design dimensions areshown in Fig. 1 and Table I. (a) Port-1 excitation. (b) Port-2 excitation.

the feed network are given in Table I. The section has a lengthof and is placed at a distance of away from pointa ( denotes the guided wavelength in the feed substrate at 900MHz). In this case, the impedance at point b seen into the an-tenna at 900 MHz is zero (short-circuit condition), and thus isinfinite (open-circuit condition) at point a. This indicates that the900-MHz signal into the notched rectangular patch is blocked.Also note that the bandwidth of the single-stub band-stop filterusing the above-described microstrip-line section is about 25%,

Fig. 3. Measured isolation against frequency.

which is larger than the operating bandwidth studied here. Onthe other hand, since and sections all have a half wave-length at 1800 MHz, no impedance mismatch for the 1800-MHzsignal is expected; and thus good excitation of the notched rect-angular patch in the 1800-MHz band is still obtained.

For the case of the 900-MHz excitation, the blocking of the1800-MHz signal into the rectangular-ring patch is achieved bythe adding of the microstrip-line section with a length of

( is again the guided wavelength in the feed sub-strate at 900 MHz). However, the section will also affectthe 900-MHz signal into the rectangular-ring patch. To solvethis problem, the microstrip-line section is added at a dis-tance away from point c. In this case, the 1800-MHzsignal into the rectangular-ring patch is still blocked, and theimpedance at point c seen into the antenna at 900 MHz can bederived to be

(1)

where is the impedance at point c seen into the antenna,and and are the characteristic impedance of andsections, respectively; . From (1), it can be foundthat by choosing and to be 100 and 125 , respectively,the impedance has a real value of 62.5 . To achieve an


CHIOU AND WONG: COMPACT DUAL-BAND DUAL-POLARIZED PATCH ANTENNA 1939

(a)

(b)Fig. 4. Measured radiation patterns in two principal planes. (a) Port 1 at 900 MHz. (b) Port 1 at 1800 MHz.

(a)

(b)Fig. 5. Measured radiation patterns in two principal planes. (a) Port 2 at 900 MHz. (b) Port 2 at 1800 MHz.

impedance very close to 50 for , increasing values ofand need to be selected, which quickly decreases

the widths of the microstrip-line sections. Since decreasingmicrostrip-line widths requires more care in the fabricationof the feed network, and in this study are chosen tobe 100 and 125 , respectively. In this case, the impedancemismatch for the 900-MHz signal is slight, and good measuredreturn loss for the proposed antenna operated in the 900-MHzband is obtained. Also, as shown in Fig. 1(d), , , ,and are tuning-stub lengths for slots 1X, 2X, 1Y, and 2Y,respectively. In this design, , , , and are selectedto be 7.0, 3.5, 5.5, and 6.5 mm, respectively. It should also benoted that the feed network design described here is not theunique solution for the proposed antenna. However, the presentfeed network provides good results for the proposed antenna.

III. EXPERIMENTAL RESULTS AND DISCUSSION

A prototype of the proposed antenna was constructed andstudied. Fig. 2 shows the measured return loss for port-1 andport-2 excitation. The total height of the radiating patch to theantennas ground plane is 13.6 mm, corresponding to about 0.04free-space wavelength at 900 MHz. The simulated results fromthe IE3D simulation software are also shown for comparison.Good agreement is observed, and the IE3D simulation softwareis helpful in the design of the proposed antenna. The obtained10-dB impedance bandwidths for the 900- and 1800-MHz bandsare about 10% and cover the 900-MHz (890960 MHz, GSMcellular system) and 1800-MHz (17101880 MHz, DCS cellularsystem) frequency bands. The measured and simulated isolationbetween ports 1 and 2 is also presented in Fig. 3. From the mea-



sured results, the isolation across the 900- and 1800-MHzbands is less than 39 and 34 dB, respectively. Very good portdecoupling is obtained for the proposed antenna.

Radiation characteristics of the proposed antenna were alsostudied. Measured radiation patterns in two principal planes at900 and 1800 MHz for port-1 and port-2 excitation are plottedin Figs. 4 and 5, respectively. Good broadside radiation patternsare obtained, and the obtained antenna gain is about 6.5 to 7.3dBi. The estimated antenna efficiency is about 60%. For boththe 900- and 1800-MHz band operations, the dual linearly po-larized waves excited by ports 1 and 2 are also seen to be withorthogonal polarizations.

IV. CONCLUSIONA dual-band dual-polarized patch antenna operated in the

900- and 1800-MHz frequency bands with a compact structurehas been proposed and experimentally studied. The proposedantenna has impedance bandwidths of about 10% in the 900-and 1800-MHz bands, and shows high isolation between thetwo feeding ports (less than 39 and 34 dB for the 900- and1800-MHz bands, respectively). If the design can be improvedto have a higher return loss (14 dB or 1.5:1 VSWR), the pro-posed antenna would be very suitable for applications in the900/1800-MHz cellular systems for dual-polarized operations.Also, it is possible for the proposed antenna to have 2 2 portsinstead of 2 ports studied here, if preferred.

REFERENCES[1] U. Wahlberg, S. Widell, and C. Beckman, The performance of polar-

ization diversity antennas at 1800 MHz, in Proc. IEEE Antennas Prop-agation Soc. Int. Symp. Dig., 1997, pp. 13681371.

[2] S. Hienonen, A. Lehto, and A. V. Raisanen, Simple broadband dual-polarized aperture-coupled microstrip antenna, in Proc. IEEE AntennasPropagation Soc. Int. Symp. Dig., 1999, pp. 12281231.

[3] T. W. Chiou, H. C. Tung, and K. L. Wong, A dual-polarization wide-band circular patch antenna with hybrid feeds, Microw. Opt. Technol.Lett., vol. 26, pp. 3739, 2000.

[4] J.-F. Zuercher and P.Ph. Gay-Balmaz, Dual polarized, single- anddouble-layer strip-slot-foam inverted patch (SSFIP) antennas, Microw.Opt. Technol. Lett., vol. 7, pp. 406410, 1994.

[5] P. Brachat and J. M. Baracco, Printed radiating element with two highlydecoupled input ports, Electron. Lett., vol. 31, pp. 245246, 1995.

[6] F. Rostan and W. Wiesbeck, Design considerations for dual polarizedaperture-coupled microstrip patch antennas, in Proc. IEEE AntennasPropagation Soc. Int. Symp. Dig., 1995, pp. 20862089.

[7] J. A. Sanford and A. Tengs, A two substrate dual polarized aperturecoupled patch, in Proc. IEEE Antennas Propagation Soc. Int. Symp.Dig., 1996, pp. 15441547.

[8] M. Yamazaki, E. T. Rahardjo, and M. Haneishi, Construction of a slot-coupled planar antenna for dual polarization, Electron. Lett., vol. 30,pp. 18141815, 1994.

[9] B. Lindmark, A novel dual polarized aperture coupled patch elementwith a single layer feed network and high isolation, in Proc. IEEE An-tennas Propagation Soc. Int. Symp. Dig., 1997, pp. 21902193.

[10] I. Nystrom and D. Karlsson, Reduction of back radiation and cross-coupling in dual polarized aperture coupled patch antennas, in Proc.IEEE Antennas Propagation Soc. Int. Symp. Dig., 1997, pp. 22222225.

[11] B. Lindmark, A dual polarized dual band microstrip antenna forwireless communications, in Proc. IEEE Aerospace Conf., 1998, pp.333338.

Tzung-Wern Chiou was born in Taipei, Taiwan,R.O.C., in 1971. He received the B.S. degree fromNational Taipei Institute of Technology, Taipei,Taiwan, R.O.C., in 1993 and the Ph.D. degree infrom National Sun Yat-Sen University, Kaohsiung,Taiwan, R.O.C., in 2002, both in electrical engi-neering.

Currently, he is with Phycomp Taiwan Limited,Kaohsiung, Taiwan, Kaohsiung. His current researchinterests are in antenna theory and design.

Dr. Chiou was one of the winners of the StudentPaper Competition at the 2000 National Symposium on Telecommunications,Chungli, Taiwan, R.O.C. and received a Graduate Student Scholarship fromPhycomp Taiwan Limited in 2001.

Kin-Lu Wong (M91SM97) received the B.S.degree from National Taiwan University, Taipei,Taiwan, R.O.C., and the M.S. and Ph.D. degreesfrom Texas Tech University, Lubbock, in 1981, 1984,and 1986, respectively, all in electrical engineering.

From 1986 to 1987, he was a Visiting Scientistat the Max-Planck-Institute for Plasma Physics,Munich, Germany. Since 1987, he has been with theDepartment of Electrical Engineering, National SunYat-Sen University, Kaohsiung, Taiwan, R.O.C.,where he became a Professor in 1991 and, from 1994

to 1997, served as Chairman of the Electrical Engineering Department. From1998 to 1999, he was a Visiting Scholar with the ElectroScience Laboratory,The Ohio State University, Columbus. He has published more than 270 refereedjournal papers and numerous conference articles and has graduated 33 Ph.D.students. He also holds more than 50 patents and has many patents pending. Heis the author of Design of Nonplanar Microstrip Antennas and TransmissionLines (New York: Wiley, 1999), Compact and Broadband Microstrip Antennas(New York: Wiley, 2002), and Planar Antennas for Wireless Communication(New York: Wiley, 2003).

Dr. Wong is a Member of the National Committee of the Republic of Chinafor the International Scientific Radio Union (URSI), Microwave Society of theRepublic of China, and Chinese Institute of Electrical Engineers. He receivedthe Outstanding Research Award from the National Science Council of the Re-public of China in 1994, 2000, and 2002. He also received the Young ScientistAward from URSI in 1993, the Excellent Young Electrical Engineer Award fromChinese Institute of Electrical Engineers in 1998, the Excellent Textbook Awardfor Microstrip Antenna Experiment (in Chinese) from the Ministry of Educationof the Republic of China in 1998, and the Outstanding Research Award fromNational Sun Yat-Sen University in 1994 and 2000. In 2001, he also receivedthe ISI Citation Classic Award for a published paper highly cited in the field.He has been on the editorial board of the IEEE TRANSACTIONS ON MICROWAVETHEORY AND TECHNIQUES and Microwave Optical Technology Letters. He hasalso been on the Board of Directors of the Microwave Society of the Republic ofChina. He is listed in Whos Who of the Republic of China and Marquis WhosWho in the World.


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A Compact Dual-Band Dual-Polarized Patch Antenna