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Simulation and Design of Wide-Band Patch Antennas for Wireless TechnologyMimi Aminah, Nurfaridah Saman, and Hany AbdEl-Raouf

Department of Electrical and Computer Engineering College of Engineering

International Islamic University Malaysia

53100 Kuala Lumpur, Malaysia

ABSTRACT This paper presents the design of a dual bandmicrostrip antenna for wireless communication.This antenna has a bandwidth of 24% with center frequency 5.57 GHz. The antenna is designed asa patch with two slots. The outer dimensions of the patch are designed so that the antennaresonates at the upper resonant frequency. Thedimensions of the slots are designed to controlthe lower resonant frequency and the bandwidth.

The paper presents how to choose thedimensions of the patch and the slots to controlthe resonant frequencies and the bandwidth of the antenna. A design and simulation of a patchantenna based on this geometry for WiMaxtechnology is also presented.

1. INTRODUCTIONThe design of antennas for WiMax technologyrequires antennas that operates at more than justone frequency whilst maintaining a small size.Although patch antennas suffer from narrow

bandwidths [1], parasitic patches have been used

to increase bandwidths of patch antennas [2,3].In [4], E-shaped patch antenna using two slots isintroduced to design an antenna resonating attwo resonant frequencies.In [5], the design of patch antennas withswitchable slots have been presented for different wireless communication applications,e.g., dual band, circular polarized antennas for the UHF band. Another design for a wideband,multiple frequency microstrip patch antenna

based on multi-slots hole-coupled in a substratehas been presented in [6].In this paper we present how to synthesis an E-

shaped patch antenna for frequency bandssuitable for the Wimax technology. This studyshows also the effect of different parameters inthis antenna structure.

2. ANTENNA DESIGNIn this section we design a dual band antenna for the two frequency bands of (4.95 GHz 5.15GHz) and (5.7 GHz 6.0 GHz) which have

center frequencies 5.05 GHz and 5.85 GHzrespectively. Figure 1 shows the shape of thedual band patch antenna. The height of the patchis h= 4.596 mm above the substrate. The firstresonance (higher frequency) will be obtaineddue to the current flow between the two edges inthe middle part of the antenna with a path lengthW, as the single band conventional patch antenna.In order to achieve a resonance in the lower frequency band (4.95 GHz 5.15 GHz), two slots

are introduced in the patch as shown in Fig. 1.The slots are used to allow another path for thecurrent flow. The currents from the edge of the

patch would flow around the slots through a path,which is longer than the length W of the first

path. This path should cause additionalresonance at a lower frequency. In the followingwe will synthesis a patch antenna to get therequired dual band behavior by varying thedimensions of the patch and the slots.To design the patch antenna that would resonatein the two required bands, we will start by aninitial design and then we will modify thedimensions of the patch and the slots based onthe above theory until we get the dimensions thatgive us the required frequency response. As aninitial design we simulated a patch antenna withthe following dimensions: h=4.596mm,W=25.5mm, L=43mm, Ps=6mm, Ls=17mm,Ws=2mm and L1=L2=13.5mm. The antenna isfed at (Xf, Yf)=(21.5,3.2173). We simulated thisantenna using the commercial IE3d Zelandsoftware and the return loss is shown in Fig.2.The antenna is seen to resonate at 4.3 GHz (-16.7dB) and 5.1 GHz (-16.5 dB). Both the resonatingfrequencies are shifted left, from the intended5.05 GHz and 5.85 GHz. In order to shift theupper resonant frequency from 5.1 GHz towards5.85 GHz we need to reduce the width W of theantenna and in order to shift the lower resonantfrequency from 4.3 GHz up to 5.25 GHz we needto reduce the lengths of the slots. We did manytrails in changing the outer dimensions of the

patch and the dimensions of the slots. As a resultof these trails, we reduced the width of theantenna from 25.5mm to 21.4mm and the slot

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Proc. EuCAP 2006, Nice, France610 November 2006 (ESA SP-626, October 2006)

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length Ls from 17mm to 16.1mm, while the feed position remains at the same location. Increasingthe slot length is done to reduce the path currenttaken from the feed to the outer boundaries of the

patch, thus increasing the resonant frequency.The new dimensions of the antenna for thisdesign are: h=4.596mm, W=21.4mm, L=38.3mm,Ps=2.6mm, Ls=16.1mm, Ws=2mm andL1=L2=14.6mm. The antenna is fed at (Xf,Yf)=(20,3.2173). The return loss of the antennais shown in Fig. 3. The antenna is seen toresonate at 5.05 GHz and 5.85 GHz with returnloss of -20.2 dB and -26.2 dB respectively whichis our objective in this design. It is seen that the5.05 GHz corresponds to a current flow in a pathlength equals that around the slot as weexplained earlier. The gain of the antenna isshown in Fig. 4 The peak antenna gain isapproximately 10 dBi for both of the resonating

frequencies. This shows that the antenna will beable to provide the same characteristics at eachof the two resonant frequencies.In the following, we will follow the above

procedure to design a patch antenna which can be used for WiMax technology. This antennashould be resonating in the two frequency bands(3.2 GHz 3.4 GHz) and (3.6 GHz 3.8 GHz).We used a height h=7.19 mm for the patch abovethe ground plane. The dimensions of the patchesand the results of the lower resonant frequency(F low ) and the upper resonant frequency (F up) aregiven in Table 1, for the different. The feeding

position at (27.98 mm , 5.03 mm) for all casesexcept the first case is (25.16 mm , 5.03 mm).The return loss of the last case is shown in Fig.5,which shows that this antenna resonates in thetwo frequency bands (3.2 GHz 3.4 GHz) and(3.6 GHz 3.8 GHz).

Table 1: Dimensions in mm of the patch for different trails and theresonant frequencies for each case in GHz.

W L L1 L3 Ws1 Ws2 Ls1 Ls2 F low(GHz) (S11) F up (GHz) (S11)

35.35 50.32 15.82 15.82 2.87 2.87 25.16 25.16 3.12(-9.6dB) 3.85(-15.8dB)

32.31 55.97 17.88 20.21 2.87 2.0 21.77 20.66 3.37(-23.7dB) 3.88(33.6dB)

32.31 57.71 17.88 21.95 2.87 2.0 21.77 20.66 3.36(-25.2dB) 3.86(-29.7dB)

33.28 60.87 17.88 21.95 2.87 2.03 21.77 20.66 3.3(-17.1dB) 3.8(-27.9dB)

33.28 60.87 19.6 21.96 2.87 2.03 21.77 20.66 3.28(-27.12dB) 3.74(-30.78dB)

4. CONCLUSIONA single element dual-band patch antenna for theWiMax application has been proposed.The antenna is air filled between the ground

plane and the radiating patch. The antennaoperates in the (4950 5150) MHz and (5650 6000) MHz bands, which lies in the 5 GHzU-NII bands specified for the WiMax operation.The antenna has a bandwidth of approximately24 %. The peak gain of the antenna for both of the bands is approximately 10 dBi.

5. REFERENCES[1] C. A. Balanis, Antenna Theory,

Analysis and Design, Third Edition,John Wiley and Sons

[2] G. Kumar and K. C. Gupta,Directlycoupled multiple resonator wide-bandmicrostrip antenna, IEEE Trans.Antennas Propagat., vol. AP-33, pp.599-593, June 1985

[3] D. M. Pozar ,Microstrip antenna

coupled to a microstrip line, Electron.Lett., vol. 21, no.2, pp. 49-50, Jan 1985[4] F.Yang, et al.,Wide-band E-shaped

patch antennas for wirelesscommunications, IEEE Trans.Antennas Propagat., vol. 49, No.7, pp.1094-1100, July 2001

[5] F.Yang and Y.Rahmat-Samii, PatchAntennas with Switchable Slots (PASS)in Wireless Communications: Concepts,Designs, and Applications, IEEEAntennas and Propagation Magazine,Vol. 47, No.2, pp. 13-29, April 2005.

[6] D.Neog, et al., Design of WidebandMicrostrip Antenna and the Use of Artificial Neural Networks in Parameter Calculation, IEEE Antennas andPropagation Magazine, Vol. 47, No.3,

pp. 60-65, June 2005.

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Figure 1. The Dual-Band Antenna

Figure 2. of the dual band patch antenna of Fig.1 with dimensions:

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h=4.596mm, W=25.5mm, L=43mm, Ps=6mm,Ls1=Ls2=17mm, Ws1=Ws2=2mm,

and (Xf, Yf)=(21.5,3.2173).

Figure 3. of the dual band patch antenna of Fig.1 with dimensions:

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h=4.596mm, W=21.4mm, L=38.3mm,L2=5.2mm, Ls1=Ls2=16.1mm,Ws1=Ws2=2mm, and (Xf, Yf)=(20,3.2173).

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Figure 5. of the dual band patchantenna of Fig.1 with dimensions:

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Figure4. Gain in the two planes XZ

(=0O) and YZ ( =90 O) of the dual band patch antenna of Fig.3 .

h=7.19mm, W=33.3mm, L=60.87mm,L1=19.6 mm, L3= 21.9 mm, Ws1= 2.88mm, Ws2= 2.03 mm, Ls1= 21.77mm,Ls2=20.66 mm, and (Xf,Yf)=(27.98mm,5.03mm).