novel-integrated patch antennas with multi-band

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Published in IET Microwaves, Antennas & Propagation

Received on 21st May 2010

Revised on 19th May 2011

doi: 10.1049/iet-map.2010.0515

ISSN 1751-8725

Novel-integrated patch antennas with multi-bandcharacteristicsK. Jhamb L. Li K. Rambabu

Department of Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta, Canada

E-mail: [email protected]

Abstract: In this study, two integrated multi-band microstrip patch antennas have been proposed for the next-generation wireless

systems. The first design consists of a right isosceles triangular patch integrated with a pair of monopoles. The patch resonates at3.5 GHz (WiMAX, worldwide interoperability for microwave access) and the monopoles at 2.45 GHz (WLAN, wireless localarea network) and 1.96 GHz (PCS frequency), respectively. Furthermore, to improve the gain profile and to achieve directiveradiation characteristics towards zenith, a reflector ground plane has been placed below the patch. The detailed analysis of the

pattern synthesis technique has been explained. Similarly, the second proposed design consists of a semi-circular patchresonating at 3.5 GHz integrated with a slot and a monopole. The slot and monopole resonate at 5.5 GHz (WiMAX) and2.45 GHz, respectively. Both the designs are realised on a 1.58 mm-thick FR4 substrate (dielectric constant 4.4) and have areturn loss better than 10 dB with desired radiation characteristics at the specified resonant frequencies. Prototypes of the

proposed designs have been fabricated and their radiation characteristics have been measured. A close agreement has beenfound between simulation and measurements.

1 Introduction

Emerging trends and growing technologies in the wirelessindustry demand products that are capable of providingmultiple services with a single device. The desired scenariowill be miniaturised multi-frequency antennas that can besuited for multi-band usability with the desired radiationcharacteristics [16]. Nowadays, wireless systems have

become an integral part of the lives of most people. Hence,the integration of technologies such as WLAN, WiMAX andPCS into a single device is a perfect combination for thecommercial advancements. WLAN (wireless local areanetwork) enables wireless connectivity among personaldigital assistant (PDAs), laptops, mobile phones and manyother electronic devices using a single-node access point. Itis based on IEEE 802.11 b and g configurations and operatesin 2.4 GHz band [7, 8]. HomeRF and Bluetooth also operatein the same band, thus making this band useful for manyapplications. Recently, WiMAX (worldwide interoperabilityfor microwave access) is also attracting many users towardsits advantageous features. It operates in the 2.5/3.5/5.5 GHz

bands and is based on IEEE 802.16 standard (Broadbandwireless access) [9]. This wireless technology offers betterquality of service, range and throughput as compared withWLAN. Similarly, PCS operates in the 1900 MHz band thatis being used for digital mobile phone services [10]. Usingthis technology, a user can avail facilities such as call

mobility, instant messaging or voice mails that make thisband quite popular in the public domain.

A microstrip patch configuration has been used for theproposed designs because of low cost, low profile, ease of

fabrication and its compatibility with integrated circuits[11, 12]. Among various shapes of microstrip patchantenna, triangular and semi-circular configurations are

preferred because of their miniaturised configuration andsuitability for wireless applications [13, 14]. As inferredfrom the literature, there are various multi-band microstrip

patch designs with triangular and semi-circular shapeconfigurations using slots [15, 16], active elements [17],shorting pins [18], excitation of higher-order modes by the

patch [19], shorting planes [14], different feedingtechniques [20, 21] or achieving single wideband resonanceinstead of multiple resonances [22]. However, the proposeddesigns are novel in terms of integration with monopolesand slots. At the same time simplicity, flexibility andindependent frequency tunability in the design have also

been maintained. For the stated wireless applications, theradiation pattern should be omni-directional towards zenith,so that the connectivity with the base station antennas ismaintained ubiquitously.

In this study, two designs have been proposed for theabove-stated wireless applications with return loss betterthan 10 dB and desired radiation characteristics. The firstdesign is a right isosceles triangular patch antennaintegrated with a pair of monopoles. This design realisesresonances at 1.96, 2.45 and 3.5 GHz, respectively, thusmaking this design capable of multi-band operation (PCS,WLAN and WiMAX). A pattern synthesis technique to

achieve desired directive radiation characteristics has alsobeen introduced. Similarly, the second design is also basedon a microstrip patch configuration and consists of a semi-circular patch integrated with a slot and monopole. The

IET Microw. Antennas Propag., 2011, Vol. 5, Iss. 12, pp. 13931398 1393

doi: 10.1049/iet-map.2010.0515 & The Institution of Engineering and Technology 2011

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patch resonates at 3.5 GHz, while the slot and the monopoleresonate at 5.5 and 2.45 GHz, respectively. The prototypes for

both the designs have been fabricated. Good agreement hasbeen found between simulation and measurement results.

2 Antenna design

2.1 Design 1

In this section, an antenna design is presented for WLAN,WiMAX and PCS applications. The proposed structureconsists of a right isosceles triangular patch integrated witha pair of monopoles as shown in Fig. 1. The patch hasresonance at 3.5 GHz (WiMAX), and monopoles resonateat 2.45 and 1.96 GHz, respectively. The monopole fusedalong the base of the isosceles triangular patch (bottom) isresponsible for WLAN frequency (2.45 GHz) operation,while the other monopole fused along the height of thetriangular patch (side) is responsible for the PCS(1.96 GHz) application (refer Fig. 1). The design principleof the patch has been introduced in [19]. However, themonopoles are a quarter wavelength long including the

fringe field depth. As shown in Fig. 1, a part of the printedmonopoles acts as a microstrip feed line while the other

part acts as a radiating strip. The width and location of themonopoles have been optimised using electromagnetic (EM)solvers in such a way that maximum current flows into themonopole, thus achieving better impedance match at 2.45and 1.96 GHz. Furthermore, the monopoles have been bentto achieve miniaturisation in the design (Fig. 1). The noveltyin this design is the integration of the design with twomonopoles thus making it capable of multi-band operationand at the same time simplicity in the design is alsomaintained. The proposed design is a probe- fed design andis realised on a 1.58 mm-thick glassy epoxy substrate with a

dielectric constant of 4.4. The structural view and dimensionsof the proposed design are also shown in Fig. 1. A prototypeof the design has been fabricated and is shown in Fig. 2.

2.1.1 Pattern synthesis: The major drawback of theproposed design was that the boresight radiation from thepatch and the monopoles was not in the same direction. Theradiation beam from the patch was focussed towards zenith,while, the beam due to the monopoles was tilted towardsthe backward direction (below the patch) owing to the

existence of dielectric substrate below the radiating strip ofthe printed monopoles. Hence, to overcome this radiation

concern, a reflector ground plane has been added below theactual ground plane of the patch to accomplish a high-gain

profile with desired radiation characteristics. The location ofthe reflector plane has been optimised at 5 mm below theground plane of the patch. The basic concept of thistechnique is to choose the location of the reflector planesuch a way that the reflected signal from this plane shouldadd in phase with the radiated signal from the patch toimprove the gain profile of the proposed design, as well asthe major lobe of the radiation pattern focused in thedesired direction. A parametric study on the location of thereflector plane has been carried out using EM solvers (CSTMicrowave Studio and Ansoft HFSS Designer) and it has

been found that minimum dimension of the reflector planeis 80 80 mm2. However, in practice, the mountingplatform can be used as the reflector plane to achieve statedradiation and gain characteristics.

2.1.2 Measurement and simulation results: Theantenna operation was verified using two EM solvers CSTMicrowave Studio and Ansoft HFSS designer and theexperimental measurements. The simulated and measuredreturn loss has been shown in Fig. 3. The simulated (CST)

Fig. 1 Triangular patch antenna (design 1)

Fig. 2 Prototype antenna for the design 1

1394 IET Microw. Antennas Propag., 2011, Vol. 5, Iss. 12, pp. 13931398

& The Institution of Engineering and Technology 2011 doi: 10.1049/iet-map.2010.0515

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return loss at 1.96, 2.45 and 3.5 GHz is 223.46, 216.55 and214.12 dB, respectively, while the measured return loss isaround212.97, 210.87 and28.6 dB, respectively, at thespecified resonant frequencies. The typical error between

the simulation and measurements with regard to shift in theresonant frequency is around 1.9, 1.45 and 2% at 1.96, 2.45and 3.5 GHz, respectively. The real and imaginaryimpedances of the antenna have also been shown in Fig. 4.The simulated and measured impedance (Fig. 4) plotsillustrate a good impedance match at the resonantfrequencies, that is, the real part of the impedance is close to50 V while the imaginary value is as low as 0 V. Thesimulated and measured radiation patterns of the antenna atPCS, WLAN and WiMAX frequencies have been shown inFigs. 5, 6 and 7, respectively. The measured radiation

patterns are quite similar to the simulated patterns, that is,omni-directional with the boresight towards the zenith thusmaking this design suitable for the stated applications. Thesimulated beamwidth in E-plane (XZ-plane) and H-plane(YZ-plane) at the specified resonant frequencies is around778 and 808, respectively. However, in terms of comparison

between the simulated and the measured patterns, thetypical error in the E-plane and H-plane beamwidth is about4.9 and 13.3%, respectively. The simulated and measured

realisable gain has also been shown in Fig. 8. Thesimulated (CST) realisable gain at all the resonantfrequencies is better than 5 dBi, which explains the role of

the reflector ground plane below the patch to achieve

Fig. 4 Simulated and measured impedances against frequency

Fig. 5 Simulated (solid line) and measured (dash line) radiation

pattern at 1.96 GHz


pattern at 2.45 GHz


pattern at 3.5 GHz

Fig. 8 Realisable gain against frequency

Fig. 3 Return loss against frequency



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directive radiation characteristics. The simulated realisablegain at 1.96, 2.45 and 3.5 GHz is 5.8, 7.9 and 7.5 dBi,respectively, while the measured gain at the resonantfrequencies is around 1.3, 6.28 and 7.95 dBi, respectively. Itis found that measured impedance bandwidth is smaller thanthe simulated impedance bandwidth. However, to improvethe bandwidth of the antenna, broadband monopoleconfigurations can be integrated at different resonantfrequencies [23, 24].

2.2 Design 2

The proposed design is also a single probe-fed designcomprises a semi-circular patch integrated with a slot and amonopole. The patch resonates at 3.5 GHz (WiMAX),while the slot and the monopole resonate at 5.5 GHz(WiMAX) and 2.45 GHz (WLAN), respectively. The designand structural view of the proposed design is shown inFig. 9. The design principle of the semi-circular patch can

be followed using this empirical equation

D lg (1)

where D is the diameter of the patch and

lg = cf0

1reff

where c is the speed of the light, f0 is the frequency of theoperation and1reff is the effective dielectric constant.

The empirical equation is stated based on detailedparametric study and current distribution analysis. Thecurrent distribution at 3.5 GHz is shown in Fig. 10. Twohalf-wavelength variations can be easily observed from thecurrent pattern shown in Fig. 10, which supports the statedmathematical interpretation.

The monopole is a quarter wavelength monopole includingfringing field depth. As shown in Fig. 9 the tapers have been

added to the monopole to enhance the flow of current into themonopole. The taper width has been optimised in accordancewith the return loss characteristics at 2.45 GHz using EMsolvers. A part of the monopole acts as a feeding microstrip

line (with ground plane) and the other part as the radiatingstrip (without ground plane).

However, the slot has been cut on the patch at the locationwhere the surface current is maximum for 5.5 GHz. Thedimension of the slot has been calculated based on theanalysis that slot acts as a l/2 electric dipole in the far fieldincluding the effect of effective dielectric constant [12].Hence, the length of the slot can be approximated as

l lg/2 (2)

where lis the length of the slot. However, the width of the slot

is optimised for impedance matching at 5.5 GHz. Thedimension of the proposed design has been shown inFig. 9. This design is also realised on a 1.58 mm-thick FR4substrate (1r 4.4). A prototype of the proposed design has

been fabricated and is shown in Fig. 11.

2.2.1 Measurement and simulation results: Two EMsolvers (CST Microwave Studio and Ansoft HFSSDesigner) have been used for the verification of the antennacharacteristics. An agreeable match has been found betweensimulated and measurement results. The simulated and

Fig. 9 Semi-circular patch antenna (design 2)

Fig. 10 Current distribution at 3.5 GHz



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measured return loss has been shown in Fig. 12. The typicalerror in terms of the shift in the resonant frequency betweenthe simulation and the measurements is around 7.9, 6.8 and1.8% at 2.45, 3.5 and 5.5 GHz, respectively. The simulatedand measured impedances of the antenna have also been

shown in Fig. 13. The simulated and measured radiationpatterns of the antenna at WLAN (2.45 GHz) and WiMAX(3.5/5.5 GHz) frequencies have been shown in Figs. 1416,respectively. The typical simulated beamwidth in E-plane(YZ-plane) and H-plane (XZ-plane) at specified resonant

frequencies is around 127 and 728, respectively. However,the percentage difference between the simulated andmeasured beamwidth is around 8.5 and 21 for the E-planeand H-plane, respectively. The simulated and measuredrealisable gain has also been shown in Fig. 17. Thesimulated realisable gain at 2.45 and 3.5 GHz and 5.5 GHzis 1.2, 1.5 and 1.8 dBi, respectively. However, the measuredgain at the resonant frequencies is around 1.7, 2 and3.9 dBi, respectively. The stated comparisons between thesimulation and the measurements support the designoperation and its usability for the specified applications.

Fig. 12 Return loss against frequency

Fig. 13 Simulated and measured impedances against frequency


pattern at 5.5 GHz

Fig. 11 Prototype antenna for the design 2


pattern at 2.45 GHz


pattern at 3.5 GHz



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3 Conclusion

Two multi-band probe-fed microstrip patch antenna designs

have been proposed. Both the designs are realised on a1.58 mm-thick FR4 substrate with a dielectric constant of 4.4.The first design consists of a right isosceles triangular patchintegrated with a pair of monopoles. The patch resonates at3.5 GHz (WiMAX frequency), however, the monopolesrealise resonances at 2.45 GHz (WLAN frequency) and1.96 GHz (PCS frequency), respectively. Furthermore, toachieve better radiation characteristics and high gain, areflector ground plane has been placed below the patch. Thesecond proposed design consists of a semi-circular patchintegrated with a slot and a monopole. The patch resonates at3.5 GHz; however, the slot and monopole resonate at 5.5 and2.45 GHz, respectively. For the analysis of the proposed

designs, two EM solvers are used CST Microwave Studioand Ansoft HFSS designer. A reasonable agreement has beenfound between simulation and experimental results.

4 References

1 Chen, S. B., Jiao, Y.-C., Wang, W., Zhang, F.-S.: Modified T-shapedplanar monopole antennas for multiband operation, IEEE Trans.Microw. Theory Techn., 2006, 54, (8), pp. 32673270

2 Martinez-Vazquez, M., Litschke, O., Geissler, M., Heberling, D.,Martinez-Gonzalez, A.M., Sanchez-Hernandez, D.: Integrated planarmultiband antennas for personal communication handsets, IEEETrans. Antennas Propag., 2006, 54, (2), pp. 384391

3 Raj, R.K., Joseph, M., Paul, B., Mohanan, P.: Compact planarmultiband antenna for GPS, DCS, 2.4/5.8 GHz WLAN applications,

Electron. Lett., 2005, 41, (6), pp. 2902914 Lau, P.Y., Yung, E.K.N., Yung, K.K.O.: Compact dual-band patch

antenna for wireless communication applications. IEEE AntennasPropagation Int. Symp., June 2007, pp. 633636

5 Choi, H.S., Jong Park, K., Sun Kim, K., Hak Kim, S.: Design of dual-band antenna for the ISM band using a backed microstrip line, Microw.Opt. Technol. Lett., 2004, 41, (6), pp. 457460

6 Ben Ahmed, M., Bouhorma, M., Elouaai, F., Mamouni, A.: Designof new multi standard patch antenna GSM/PCS/UMTS/HIPERLAN for mobile cellular phones, Eur. J. Sci. Res., 2009, 32,(2), pp. 151157

7 Kerry, S.: Popular wireless local area networks gain large boost inspeed (Piscataway, NJ, USA, june 2003), http:/standards.ieee.org/announcements/80211gfinal.html

8 IEEE-td-802.11-2007: IEEE standard for information technology telecommunications and information exchange between systems local and metropolitan area networks-specific requirements Part 11:wireless LAN medium access control (MAC) and physical layer(PHY) specifications (LAN/MAN Standards Committee, New York,NY, USA, June 2007), pp. C1 C1184

9 Hossain, E.: IEEE802.16/WiMAX-based broadband wireless networks:protocol engineering, applications, and services. Fifth Annual Conf.Communication Networks and Services Research, 2007. CNSR 07,May 2007, vol. 1417, pp. 34

10 BroadbandPCS [Online]. http://wireless.fcc.gov/services/index.htm?job=service_bandplan &id=broadband_pcs

11 James, J.R., Hall, P.S.: Handbook of microstrip patch antennas (PeterPeriginus, London, 1989)

12 Balanis, C.A.: Antenna theory analysis and design (John Wiley &Sons, New Jersey, 2005)

13 Hassani, H.R., Mirshekar-Syahkal, D.: Analysis of triangular patchantennas including radome effects, Microw. Antennas Propag. IEEProc. H, 1992, 139, (3), pp. 251256

14 Guo, Y.X., Luk, K.M., Lee, K.F.: Small broadband semicircular patchantenna with an L Probe feeding, Microw. Opt. Technol. Lett., 2001, 29,(5), pp. 289290

15 Wong, K.L., Pan, M.C., Hsu, W.H.: Single feed dual frequencytriangular microstrip antenna with a V shaped slot, Microw. Opt.Technol. Lett., 1999, 20, pp. 133134

16 Fang, S.T., Wong, K.L.: A dual frequency equilateral-triangularmicrostrip antenna with a pair of narrow slots, Microw. Opt. Technol.Lett., 1999, 23, pp. 8284

17 Lee, K.-M., Sung, Y.-J., Baik, J.-W., Kim, Y.-S.: A triangularmicrostrip patch antenna for multi-band applications. APMC 2008,Microwave Conf., 2008., Asia-Pacific, December 2008, vol. 16 20,pp. 1 4

18 Pan, S.C., Wong, K.L.: Dual frequency triangular microstrip antennawith a shorting pin, IEEE Trans. Antennas Propag., 1997, 45,pp. 1889 1891

19 Sharma, V., Shekhawat, S., Saxena, V.K., et al.: Right Isoscelestriangular microstrip antenna with narrow l-shaped slot, Microw. Opt.Technol. Lett., 2009, 51, (12), pp. 30063010

20 Chen, W., Li, B., Tao, X.: Compact dual-frequency semi-circularmicrostrip antenna, Microw. Opt. Technol. Lett., 2004, 4, (5),pp. 430 432

21 Guo, Y.X., Luk, K.M., Lee, K.F.: Regular circular and compactsemicircular patch antennas with a T-probe feeding, Microw. Opt.Technol. Lett., 2001, 31, (1), pp. 6871

22 Danideh, A., Sadeghi Fakhr, R., Hassani, H.R.: Wideband co-planarmicrostrip patch antenna, Prog. Electromagn. Res. Lett., 2008, 4,pp. 81 89

23 Johnson, J.M., Rahmat-Samii, Y.: The tab monopole, IEEE Trans.Antennas Propag., 1997, 45, (1), pp. 187188

24 Yan, X.-R., Zhong, S.-S., Yang, X.-X.: Compact printed monopoleantenna with super-wideband. Int. Symp. on Microwave, Antenna,Propagation and EMC Technologies for Wireless Communications,2007, August 2007, vol. 1617, pp. 605607

Fig. 17 Realisable gain against frequency



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novel-integrated patch antennas with multi-band

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