gsm based dual frequency antenna

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IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 51, NO. 8, AUGUST 2003 1947

Design of Dual-Frequency Probe-Fed MicrostripAntennas With Genetic Optimization Algorithm

Ozlem Ozgun, Selma Mutlu, M. I. Aksun, Senior Member, IEEE, and Lale Alatan, Member, IEEE

AbstractDual-frequency operation of antennas has become anecessity for many applications in recent wireless communicationsystems, such as GPS, GSM services operating at two different fre-quency bands, and services of PCS and IMT-2000 applications. Al-though there are various techniques to achieve dual-band opera-tion from various types of microstrip antennas, there is no efficientdesign tool that has been incorporated with a suitable optimiza-tion algorithm. In this paper, the cavity-model based simulationtool along with the genetic optimization algorithm is presented forthe design of dual-band microstrip antennas, using multiple slotsin the patch or multiple shorting strips between the patch and theground plane. Since this approach is based on the cavity model,the multiport approach is efficiently employed to analyze the ef-fects of the slots and shorting strips on the input impedance. Then,the optimization of the positions of slots and shorting strips is per-formed via a genetic optimization algorithm, to achieve an accept-able antenna operation over the desired frequency bands. The an-tennas designed by this efficient design procedure were realized ex-perimentally, and the results are compared. In addition, these re-sults are also compared to the results obtained by the commercialelectromagnetic simulation tool, the FEM-based software HFSS byANSOFT.

Index TermsGenetic algorithms, microstrip antennas, mul-tiple band antennas, multiport circuits.

I. INTRODUCTION

RECENT advances in wireless communications systems,such as GSM and DCS in Europe, PCS in America, wire-

less local area networks (WLAN), wireless local loops (WLL),future broadband 3G systems and etc., have instigated a flurry ofinterest in microstrip antennas. This is mainly due to the uniquefeatures of microstrip antennas; which are, namely, low in pro-file, compact in structure, light in weight, conformable to non-planar surfaces, easy and inexpensive for mass production, andwell suited for integration withfeeding networks and microwavedevices, especially with the modern monolithic microwave in-tegrated circuit technology. In addition, from the applications

Manuscript received September 28, 2001; revised April 28, 2002.O. Ozgun was with the Electrical and Electronics Engineering Department,Bilkent University, Bilkent 06533, Ankara, Turkey. She is now with The Scien-tific and Technical Research Council of Turkey (TBITAK)-National ResearchInstitute of Electronics & Cryptology (UEKAE), 06100 Ankara, Turkey.

S. Mutlu was with the Bilkent University, Electrical and Electronics Engi-neering Department, Bilkent 06533, Ankara, Turkey. She is now with BasariCompany, 06070 Ankara, Turkey.

M. I. Aksun was with the Electrical and Electronics Engineering Department,Koc University, Sariyer 80910, Istanbul, Turkey. He is now with the Electricaland Electronics Engineering Department, Bilkent University, Bilkent 06533,Ankara, Turkey.

L. Alatan is with the Electrical and Electronics Engineering Department,Middle East Technical University, 06531 Ankara, Turkey.

Digital Object Identifier 10.1109/TAP.2003.814732

point of view, the microstrip antennas can be designed to per-form any function that other antenna structures can perform,such as, circularly polarized radiation, multiband operations,etc.Sincemost wireless communicationssystems co-exist in thesame geographic area, one handset needs to cover some of theseservices, which requires multimode or at least dual-mode opera-tion. For example, since services from GSM900 and GSM1800have been provided in Europe over thesame regions forthe samecustomers, dual-band mobile phones covering both frequencybands have become necessity for the expansion of the systems.Therefore, it is of paramount importance to devise a compu-

tationally efficient approach to design dual or multiband mi-crostrip antennas that also satisfy other specifications like inputvoltage standing wave radio (VSWR) over each band. In thispaper, an efficient algorithm based on the cavity model and a ge-netic optimization algorithm is developed to design multibandmicrostrip antennas with shorting strips or slots. This approachis very versatile and efficient, that is, one can optimize any setof characteristics of the antenna with the optimization of thenumber and locations of the shorting strips or slots.

Recent studies on microstrip antennas have primarily con-centrated on the improvement of bandwidth and on the designof multifunction operations [1][9]. As a result, almost 100%bandwidth in terms of VSWR, and dual-band operations for

GSM900 and GSM1800 WLAN services have been success-fully accomplished and demonstrated [1], [6]. Along with thisrevived interest on the applications of microstrip antennas,development of efficient and accurate simulation tools to helpanalyze and design such antennas has gained some interestas well. For the simulations of printed antennas, there havebeen three major approaches, namely, the transmission linemodel, the cavity model and the full-wave techniques, orderedaccording to increasing accuracy [10]. Among these, the cavitymodel has a special place for providing physical intuition on theelectrical characteristics and radiation mechanism of microstripantennas, in addition to better accuracy as compared to thetransmission line model, and better computational efficiency as

compared to the full-wave approaches [11][13]. Therefore, thecavity model is often used to design the first trial antenna, andthen the fine-tuning is performed with a full-wave approach,like HFSS by ANSOFT. Since the cavity model is numericallyquite efficient and capable of handling variety of microstripantennas with shorting pins and slots, when it is coupled witha suitable optimization algorithm, the combination would be avery efficient and effective design tool, at least during the initialphase of the design. During this study, a genetic algorithmwas chosen as the suitable optimization tool that would becoupled with the cavity model. This choice was motivated

0018-926X/03$17.00 2003 IEEE
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1948 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 51, NO. 8, AUGUST 2003

by the earlier study of the optimization algorithms applied tomicrostrip antennas, in conjunction with a full-wave simulationtool [14], where it was concluded that the genetic optimizationalgorithms with binary encoding are quite suitable for problemswith discrete choices of the optimization parameters.

The idea of using a single patch in dual-frequency oper-ation was first proposed and developed by Derneryd [15],

where a single disc-shaped patch was connected to a compleximpedance matching network, resulting in two narrowlyspaced frequency bands. Since then, a variety of single-patch,dual-band microstrip antennas have been proposed and de-signed, some of which use patches loaded with shorting pins[16][18], some others use patches with slots [19][22], andpatches with more than one port [6], [8]. In addition, there aresome other approaches to achieve the dual-band operation:triangular microstrip antenna with a V-shaped slot loading [23];circular microstrip antenna with an open-ring slot [24]; stackedquarter wavelength rectangular patch elements [25]; anddrum-shaped patches [26] are just the few of these examplesavailable in the literature.

Considering that microstrip antennas are resonant structuresand can resonate at many discrete frequencies, they are bound tooperate more than one frequency by nature. However, the dual-frequency operation with just a single patch antenna is mostlyuseful if the antenna over both frequency bands of interest hassimilar radiation patterns, polarizations and input impedancecharacteristics. Therefore, in the design of dual-band microstripantennas, one needs to decide on the useful modes of resonancesatisfying these constraints. For example, if an antenna is to bedesigned for linear polarization on the same direction over bothfrequency bands, then the two lowest useful modes of resonanceare (0,1) and (0,3) modes according to the cavity model. Fur-

thermore, since the frequencies associated with these modes arefixed (the ratio of the frequencies of the modes is 3), they needto be tuned according to the specification of the required bandsof frequencies. In this respect, shorting pins (or strips) locatedbetween the patch and the ground plane and slots in the patchgeometry play very important roles in tuning the modal frequen-cies to the desired frequencies. By properly placing the shortingpins under the patch orslots in the patch, the ratio of the frequen-cies corresponding to the lowest useful cavity modes, namely(0,1) and (0,3), can be adjusted to any value less than 3. Note,that a shorting pin placed at the nodal lines of (0,3) mode doesnot affect the resonant frequency of (0,3) mode significantly,but increases the resonant frequency of (0,1) mode, by forcing

the electric field to be zero at the position of the shorting pin asseen in Fig. 1(a). Similarly, when a slot is placed on the patchwhere the magnetic field of (0,3) mode is maximum, the radia-tion from theslot results in a perturbationof thefield distributionthat gives rise to a decrease in the operating frequency of (0,3)mode [Fig. 1(b)].

Brief review of the cavity model in conjunction with the mul-tiport analysis for a microstrip antenna with shorting strips andslots is provided in Section II. Then, the design process of mi-crostrip antennas with strips and slots via the genetic optimiza-tion algorithm is discussed in Section III, where some exam-ples and discussions on the proposed algorithm for the designof multifrequency antennas are also included. In addition, the

(a)

(b)

Fig. 1. Cavity modes of the patch antenna (solid line: (0,1) mode, dashed line:(0,3) mode).

electrical characteristics of the designed antennas, as obtainedby the multiport analysis, are compared to those obtained exper-imentally and to those obtained by the full-wave method, HFSSby ANSOFT. This is followed by the conclusion in Section IV.

II. CAVITYMODELWITHSHORTINGPINS ANDSLOTS

The cavity model wasfirst proposed in 1979 forprobe-fed mi-

crostrip antennas [11]. Since then, the method has been furtherimproved to predict the input impedance of microstrip antennaswith multiple strips or slots, and to cover microstrip antennasfed by slots in the ground plane [17], [19], [27]. The major re-striction of the cavity model is on the thickness of the substrate,which is supposed to be not more than a few hundredths of awavelength. This is mainly because the model assumes that nei-ther field components nor the source can be a function of thevertical coordinate under the patch. As a result of this assump-tion, the electric field has only z component, while the mag-netic field has only x and y components in the region boundedby the microstrip patch and the ground plane, Fig. 2. In addition,using the fact that the electric current density on the microstrip
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of the slots are effective lengths, which are slightly smaller thanthe physical lengths [27].

For the application of the multiport analysis to such geome-tries, slots need to be defined as additional ports, across whichvoltage sources would be suitable to define. Therefore, sinceboth a vertical strip as the feed and slots exist, the matrix thatcharacterizes the system is not a pure impedance matrix any

more, as in the case of multiple shorting strips. For example,the matrix and its entries for the system depicted in Fig. 3. aregiven as follows:

(5)

where the matrix is of a hybrid type, mixed with impedance ,admittance , current gain and voltage gain parameters.Since there is only one vertical strip, which is used for feeding,in this example and throughout this study, only exists in thisformulation. However, this approach can be easily extended to

multiple vertical strips and slots together, for which case thecharacterization matrix would be formed by block matrices of

, , , and . Referring back to the example givenin Fig. 3, the parameter has already been introduced in (2);the others can be obtained easily from the following definitions:

(6)

(7)

(8)

(9)

where denotes the magneticvolumecurrentdensityat theslot j(k) and the volume below it down to the ground plane, andthe field components are defined with the two subscripts: the

first defines the polarization of the field; and the second definesthe port that was generated from. Note that slots are modeledas uniform magnetic current densities, not only at the surfacewhere slots reside but also in the volume just below it down tothe ground plane [19], [27]. The reason for the extension of themagnetic current at the slot into the volume below is that, as itwas mentioned in the introduction, source models used in thecavity model must be independent of the coordinate perpendic-ular to the patch in the substrate.

Once the matrix representation of the patch with a feed andslots is obtained, the input impedance seen by the probe feed canbe obtained in terms of the load admittances and acrosstheslot terminalsat port-jand port-k, respectively [28].By using

the port relations at slot terminals , theinput impedance seen by the probe feed at port-i is found as

(10)

For the sake of completeness, the definition of the inputimpedance of a slot with given dimensions is given in Ap-pendix A.

In summary, the multiport analysis of a microstrip antennawith some shorting pins and/or slots is performed by followingthese steps: 1) vertical strips (shorting or feeding) and slots areconsidered as the ports of an N-port network; 2) voltage and cur-rent sources are assigned to the slots and vertical strips, respec-tively; 3) independent parameters of the ports (voltage and cur-rent for strips and slots, respectively) are written in terms of thedependent parameters (current and voltage for strips and slots,

respectively); 4) circuit parameters, like impedance, admittance,current gain and voltage gain, are obtained by short-circuitingsome slots and by open-circuiting some strips; and finally 5) theinput impedance at the feed port is obtained in terms of the cir-cuit parameters, and hence the effects of the slots or strips onthe input impedance are quantitatively obtained.

III. RESULTS ANDDISCUSSION

After having introduced and reviewed the cavity model andmultiport analysis of microstrip antennas with shorting stripsand slots, these approaches have been combined with a robustoptimization algorithm, the genetic algorithm. Since the geneticalgorithm has been well studied and reviewed in the literature[31][33], it is not repeated here in detail. Instead, the stepsof the algorithm are provided for being able to discuss the pa-rameters used in the optimization algorithm. The first step is tocode the parameters of the optimization as finite length strings(chromosomes), then to generate a population of these strings,which will be multiple starting points as contrary to a single ini-tial point in gradient based optimization algorithms. Therefore,this approach increases the probability of finding the global op-timum by searching the whole parameter space in parallel. Thenext step is to evaluate the cost function at each member of thepopulation and to assign some fitness value. Then, the geneticalgorithm employs some probabilistic transition rules (random-

ized operators) to guide the search for optimum, which are re-production, crossover and mutation.

A. Multiple strips

In this study, thegenetic optimization algorithmwas firstusedto find the appropriate locations and widths of the shorting stripsin a microstrip patch antenna to match the input impedancesto 50 at both low and high frequencies and to satisfy a de-sired frequency ratio , where and denote the highand lowfrequencies, respectively, for a dual-band operation. Forthe optimization, the feed location, its width and orientation, thenumber of shorting strips, their orientations and the desired fre-quency ratio are used as known and fixed parameters, while the
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OZGUN et al.: DESIGN OF DUAL-FREQUENCY PROBE-FED MICROSTRIP ANTENNAS 1951

and coordinates, and the width of each shorting strip areused as the optimization parameters. So, the objective functionis written as

(11)

where is the desired frequency ratio, andare the input impedances at and , respectively, and 100

is just a positive number determined empirically to makemaximum at the point of optimization.

For the presentation of the algorithm discussed so far in thispaper, two microstrip antennas with some shorting strips havebeen designed for dual-band operation via the genetic optimiza-tion algorithm. The first example is an air-filled antenna andits fixed parameters are as follows: cm, cm,

cm, mho cm, , the positionof the feed, cm cm , the width of the feed,

cm and the lateral extension of the feed is in direc-

tion.The genetic algorithm has five internal properties: chromo-some length, population size, generation number, crossoverprobability, and mutation probability. Since each variableparameter, real or integer, is transformed into a binary stringwith the length defined by the precision required for thatvariable, the chromosome length is the length of the member inthe population, that is, the length of the binary string combinedfor all variables. For the study of these two antennas, thechromosome length is chosen as 25 chromosomes per unknownparameter, so that the total length of each chromosome (or amember in the population) for a patch with shorting stripsis , 3 being the number of the variable parameters foreach strip. The crossover probability and mutation probabilityused are 0.65 and 0.008, respectively, and two-point crossoveris applied in each trial. The population size and generationnumber determine the speed and efficiency of the geneticalgorithm. The optimization parameters and results for theair-filled antenna with at most two shorting strips for differentpopulation sizes and generation numbers are given in Table I,where ( , ) and ( , ) denote the coordinates of the first and second strips, respectively, and are thewidths of the strips, while and G are the population size andthe generation number, respectively, and is the desiredfrequency ratio. To guide the search algorithm, the limits ofthe and coordinates of the shorting strips are determinedby the patch dimensions, while the strip widths are varied in

the range of 0.11.5 cm. Case-1 corresponds to the patch withone shorting strip extended laterally in direction, case-2 andcase-3 correspond to the patches with two shorting strips: theformer has both strips extended inxdirection, the latter has oneextended inxdirection and the other extended inydirection.

For the first antenna, with the optimized positions and widthsof the shorting strips given in Table I, the simulation results areprovided in Table II. To assess the accuracy of the simulationtechnique used in conjunction with the optimization algorithm,the results of a full-wave approach, namely HFSS, are also pro-vided. It is observed from Table II that the resonant frequenciesand the reflection coefficients for both low and high bands agreevery well with those predicted by HFSS.

TABLE IOPTIMIZATION PARAMETERS ANDRESULTS FOR THEAIR-FILLEDANTENNA

(DIMENSIONS INCENTIMETERS)

TABLE IISIMULATIONRESULTS FOR THEAIR-FILLEDANTENNA

TABLE IIIRESONANTFREQUENCIES ANDREFLECTIONCOEFFICIENTS FOR THE

DIELECTRIC-FILLEDANTENNA

TABLE IVOPTIMIZATIONPARAMETERS ANDRESULTS FOR

The second antenna was designed to demonstrate the appli-cability of the proposed algorithm for microstrip antennas over

a dielectric material , for which the fixed parametersare: cm, cm, cm, mho cm,

, cm cm , cm.For dual frequency operation, this antenna was designed withone shorting strip located at cm, cm, andwith a width of cm, extending inxdirection laterally.The low and the high resonance frequencies together with thereflection coefficients at resonance are presented and comparedin Table III.

From the designs of these two dual-band antennas, a total offour cases, it is observed that the antennas designed by the ge-netic optimization algorithm with the multiport analysis agreewith the specifications, as confirmed by the results of a rigorous


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(a)

(b)

Fig. 4. Measured and computed impedance loci of the first patch antenna in

Table IV: (a) low band and (b) high band.

full-wave method, HFSS. This observation suggests that the al-gorithm presented here can make an efficient and accurate CADtool, at least for the initial design of dual-band microstrip an-tennas with multiple shoring strips. Another point worth notingis that, during the design iterations, the strip locations tend toconverge to the nodal field lines of the third cavity mode, asexpected.

B. Multiple Slots

The proposed design algorithm for microstrip antennas,which is the multiport analysis in conjunction with the cavity

(a)

(b)

Fig. 5. Measured and computed impedance loci of the second patch antennain Table IV: (a) low band and (b) high band.

model and genetic optimization algorithm, is further tested onmicrostrip antennas with slots etched in the patch, with a viewof designing dual-band antennas. For this study, a rectangularpatch antenna (made of bronze) fed by a vertical strip is de-signed with the following fixed parameters: cm,

cm, cm, , , S m,cm cm , and cm. As in the case

of the patch antenna with shorting strips, the goal of the opti-mization is again to find the appropriate coordinates and lengthof the slots used, to satisfy the specifications on the frequency


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OZGUN et al.: DESIGN OF DUAL-FREQUENCY PROBE-FED MICROSTRIP ANTENNAS 1953

ratio and on the input impedance over the high and low fre-quency bands. So, using the objective function defined in (11),xandycoordinates, and the length of each slot are optimized. Itis worth mentioning that the cavity model is applicable to patchantennas with narrow slots, therefore the width of each slot isfixed to 0.15 cm. For the optimization algorithm, the chromo-some length, crossover and mutation probabilities are set to 20

(for each optimization parameter), 0.65 and 0.008, respectively.Also, two-point crossover is used in each process.

The frequency ratio is set to 2.7, and optimizations are per-formed for different numbers ofx oriented slots. In each opti-mization with different number of slots, the population size andgeneration number are fixed to 1000 and 200, respectively. Theoptimization results are summarized in Table IV, where the firstcolumn gives the number ofx oriented slots, and the last columngives the optimized positions and lengths of the slots. For all thecases studied here, the specifications on the frequency ratio andthe input impedances have been very well satisfied. To verifythe optimization results, the first and second optimized antennasin Table IV were realized and tested experimentally. Then, the

input impedances obtained from the multiport analysis in con-junction with the cavity model, from measurements and fromHFSS are compared over both low and high bands as shown inFigs. 4 and 5.

It is observed from Table IV that the design algorithm pre-sented in this paper provides positions and lengths of the slotsquiteaccurately for the design of dual-bandmicrostrip antennas.The input impedance loci presented in Figs. 4 and 5 imply thatthe multiport method proposed in this paper performs well, asfar as the accuracy is concerned.

IV. CONCLUSION

Dual-frequency operation of rectangular patch antennas with

shorting strips and slots has been investigated via the cavitymodel in conjunction with the multiport theory. By combiningthis approach with the genetic optimization algorithm, an ef-ficient and accurate design tool was proposed for dual-bandmicrostrip antennas using multiple vertical strips or slots. Forthe examples provided in this study, the frequency ratio of thehigh-band and low-band frequencies, and the input impedancesover these bands were used as the specifications, while the coor-dinates and dimensions of the strips or slots were the optimiza-tion parameters. The antennas so designed have been realized,and dual-band operation was verified experimentally as well asby simulation of the antennas rigorously via HFSS by Ansoft. Itis observed that the theoretical results agree well with the exper-imental results. Therefore, this approach can be safely proposedas an efficient CAD tool for dual-band microstrip antennas thatwould use slots or vertical strips, at least for the initial design ofthe antennas.

APPENDIX AIMPEDANCE OF ASLOT

The impedance of a slot in an infinite ground plane can beapproximately obtained by the impedance of a short dipole viawell-known Babinets principle [29], [30]

(A.1)

where is the intrinsic impedance of the free space, and thedipole is assumed to be the complement of the slot. Sincethe input impedance of a short dipole can be modeled as aseries connection of radiation resistance, ohmic resistance,inductance, and capacitance, which are expressed as follows[30]:

(A.2)

where is the magnitude of the current distribution, and isthe half-length of the dipole

(A.3)

(A.4)

(A.5)

where s is the half of the gap provided for the voltage source,and is the radius of the dipole, i.e., is the width of the slot.Hence, the input impedance of the short dipole is obtained as

(A.6)

REFERENCES

[1] N. Herscovici, A wide-band single-layer patch antenna,IEEE Trans.Antennas Propagat., vol. 46, pp. 471474, Apr. 1998.

[2] , New considerations in the design of microstrip antennas,IEEETrans. Antennas Propagat., vol. 46, pp. 807812, June 1998.

[3] J.-Y.Jia-Yi Sze and K.-L.Kin-Lu Wong, Slotted rectangular microstripantenna for bandwidth enhancement,IEEE Trans. Antennas Propagat.,vol. 48, pp. 11491152, Aug. 2000.

[4] K. L. Wong and J. Y. Jan, Broadband circular microstrip antenna withembedded reactive loading, Electron. Lett., vol. 34, pp. 18041805,1998.

[5] J. R. James and G. Andrasic, Multifunction printed antennas, inAd-vances in Microstrip and Printed Antennas, K. F. Lee and W. Chen,Eds. New York: Wiley, 1997.

[6] J. F. Zurcher, A. Skrivervik, O. Staub, and S. Vaccaro, A compactdual-port dual-frequency printed antenna with high decoupling, Mi-crow. Opt. Technol. Lett., vol. 19, pp. 131137, Oct. 1998.

[7] M. Kijima, Y. Ebine, and Y. Yamada, Development of a dual-frequencybase stationantenna forcellular mobile radios,IEICE Trans.Commun.,vol. E82-B, pp. 636643, Apr. 4, 1999.

[8] J. F. Zrcher, Q. Xu, A. Skrivervik, and J. R. Mosig, Dual-frequency,dual-polarization four port printed planar antenna, Microw. Opt.Technol. Lett., vol. 23, pp. 7578, Oct. 20, 1999.

[9] G. S. Binoy, C. K. Aanandan, P. Mohanan, K. Vasudevan, and K.G. Nair, Single-feed dual-frequency dual-polarized slotted squaremicrostrip antenna,Microw. Opt. Technol. Lett., vol. 25, pp. 395397,June 20, 2000.

[10] D. M. Pozar and J. R. James, A review of CAD for microstrip an-tennas and arrays, in Microstrip Antennas: The Analysis and Designof Microstrip Antennas and Arrays, D. M. Pozar and D. H. Schaubert,Eds. New York: IEEE Press, 1995.

[11] Y. T. Lo, D. Solomon, and W. F. Richards, Theory and experiment onmicrostrip antennas,IEEE Trans. Antennas Propagat., vol. AP-27, pp.137145, Mar. 1979.
http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-


8/8


[12] W. F. Richards, Y. T. Lo, and D. D. Harrison, An improved theory formicrostrip antennas and applications,IEEE Trans.Antennas Propagat.,vol. 29, pp. 3846, Jan. 1981.

[13] W. F.William F. Richards, Microstrip antennas, inAntenna Handbook,Y. T. Lo and S. W. Lee, Eds. New York: Van Nostrand Reinhold, 1993.

[14] L. Alatan, M. I. Aksun, K. Leblebicioglu, and M. T. Birand, Useof computationally efficient method of moments in the optimizationof printed antennas, IEEE Trans. Antennas Propagat., vol. 47, pp.725732, Apr. 1999.

[15] A. G. Derneryd, Microstrip disc antenna covers multiple frequencies,Microw. J., pp. 7779, May 1978.[16] D. H. Shaubert, F. G. Garrar, A. Sindoris, and S. T. Hayes, Microstrip

antennas with frequency agility and polarization diversity, IEEE Trans.Antennas Propagat., vol. 29, pp. 118123, Jan. 1981.

[17] W. F. Richards and Y. T. Lo, Theoretical and experimental investiga-tion of a microstrip radiator with multiple lumped linear loads, Elec-tromagn., vol. 3, no. 34, pp. 371385, JulyDec. 1983.

[18] S. C. Pan and K. L. Wand, Dual frequency triangular microstrip an-tenna with shorting pin,IEEE Trans. Antennas Propagat., vol. 45, pp.18891891, Dec. 1997.

[19] B. F. Wang and Y. T. Lo, Microstrip antennas for dual-frequency op-eration, IEEE Trans. Antennas Propagat., vol. 32, pp. 938943, Sept.1984.

[20] Y. M. M. Antar, A. I. Ittipiboon, and A. K. Bhattacharyya, A dual fre-quency antenna using a single patch and an inclined slot,Microw. Opt.Technol. Lett., vol. 8, pp. 309311, Apr. 20, 1995.

[21] J. H. Lu, Dual-frequency operation of a single-feed rectangularmicrostrip antenna with a pair of comb-shaped slots, Microw. Opt.Technol. Lett., vol. 23, pp. 183186, Nov. 5, 1999.

[22] , Slot-loaded rectangular microstrip antenna for dual-frequencyoperation, Microw. Opt. Technol. Lett., vol. 24, pp. 234237, Feb., 202000.

[23] K.-L.Kin-Lu Wong, M.-C.Mon-Chun Pan, and W.-H.Wen-Hsiu Hsu,Single-feed dual-frequency triangular microstrip antenna with aV-shaped slot,Microw. Opt. Technol. Lett., vol. 20, pp. 133134, Jan.20, 1999.

[24] J. Y. Jan and K. L. Wong, Single-feed dual-frequency circular mi-crostrip antenna with an open-ring slot, Microw. Opt. Technol. Lett.,vol. 22, no. 3, pp. 157159, Aug. 1999.

[25] L.Lakhdar Zaid, G.Georges Kossiavas, J.-Y.Jean-Yves Dauvignac,J.Josiane Cazajous, and A.Albert Papiernik, Dual-frequency andbroad-band antennas with stacked quarter wavelength elements, IEEETrans. Antennas Propagat., vol. 47, pp. 654660, Apr. 1999.

[26] S.O. Kundukulam, M.Manju Paulson, C. K. Aanandan,P.Mohanan, andK. Vasudevan, Dual-band dual-polarized compact microstrip antenna,Microw. Opt. Technol. Lett., vol. 25, pp. 328330, June 5, 2000.

[27] M. I. Aksun, S. L. Chuang, and Y. T. Lo, On slot-coupled microstripantennas and their applications to CP operationtheory and experi-ment, IEEE Trans. Antennas Propagat., vol. AP-38, pp. 12241230,Aug. 1990.

[28] P. K. Park and C. T. Tai, Receiving antennas, in Antenna Handbook,Y. T. Lo and S. W. Lee, Eds. New York: Van Nostrand Reinhold, 1993.

[29] R. F. Harrington, Time-Harmonic Electromagnetic Fields. New York:McGraw-Hill, 1961.

[30] M. Kominami, D. M. Pozar, and D. H. Schaubert, Dipole and slot el-ements and arrays on semi-infinite substrates, IEEE Trans. AntennasPropagat., vol. AP-33, no. 6, pp. 600607, June 1985.

[31] D. E. Goldberg,Genetic Algorithms in Search, Optimization, and Ma-chine Learning. Reading, MA: Addison-Wesley, 1989.

[32] F. J. Ares-Pena, J. A. Rodriguez-Gonzalez, E. Villaneuva-Lopez, and

S. R. Rengarajan, Genetic algorithms in the design and optimizationof antenna array patterns,IEEE Trans. Antennas Propagat., vol. 47, p.506, Mar. 1999.

[33] J. M. Johnson and Y. Rahmat-Samii, Genetic algorithms and methodof moments (GA/MOM) for the design of integrated antennas, IEEETrans. Antennas Propagat., vol. 47, p. 1606, Oct. 1999.

Ozlem Ozgunwas born in Turkey on July 8, 1976.She received the B.S. and M.S. degrees in electricalengineering fromBilkent University, Ankara, Turkey,in 1998 and 2001, respectively.

Currently, she is a Research Scientist at TheScientific and Technical Research Council ofTurkey (TBITAK)National Research Institute ofElectronics & Cryptology (UEKAE), Ankara. Herresearch interests include numerical electromag-

netics, electromagnetic propagation and scattering,microstrip antennas and microwave theory.

Selma Mutlu was born in Turkey on January 22,1975. She received the B.S. and M.S. degrees inelectrical engineering from Bilkent University,Ankara, Turkey, in 1998 and 2001, respectively.

Currently, she is a Software Developer at BasariCompany, Ankara. Her research interests includenumerical electromagnetics, microstrip antennas andmicrowave theory.

M. I. Aksun (M92SM99) received the B.S. and M.S. degrees in electricaland electronics engineering at the Middle East Technical University, Ankara,Turkey, in 1981 and 1983, respectively, and the Ph.D. degree in electrical andcomputer engineering at the University of Illinois at Urbana-Champaign, in1990.

From 1990 to 1992, he was a Postdoctoral Pellow in the ElectromagneticCommunication Laboratory at the University of Illinois at Urbana-Champaign.From 1992 to 2001, he was on the faculty of the Department of Electrical andElectronics Engineering at Bilkent University, Ankara, Turkey, where he wasa Professor since 1999. In 2001, he joined the Department of Electrical andElectronics Engineering at Koc University, Istanbul, Turkey, as a Professor.

His research interests include numerical methods for electromagnetics,microstrip antennas, indoor and outdoor propagation models, and microwaveand millimeter-wave integrated circuits.

Lale Alatan (S91M97) received the B.S., M.S.,and Ph.D. degrees in electrical engineering from theMiddle East Technical University (METU), Ankara,Turkey, in 1990, 1993, and 1997, respectively.

From 1997 to 1998, she was a PostdoctoralFellow in the Electrical and Computer EngineeringDepartment at Carnegie Mellon University, Pitts-burgh, PA, and from 1998 to 1999, in the Electrical

and Computer Engineering Department at the NewJersey Institute of Technology, Newark. Currently,she is an Assistant Professor with the Electrical and

Electronics Engineering Department at METU. Her research interests includenumerical analysis of printed structures, microstrip antennas, phased arrays,and optimization techniques.

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