Design A Rectangular Microstrip Patch Antenna for WLAN Application

Design A Rectangular Microstrip Patch Antenna for WLAN Application

Sanjay Singp, Kishor Chandra Arya2, Rachna Arya3

1,2M.Tech scholar, 3Assistant professor Department of Electronics & Communication Bipin Tripathi Kumaon Institute of Technology Dwarahat, Uttarakhand (India) 263653

Abstract – This paper presents a rectangular microstrip patch antenna for WLAN applications operating in a single band of frequency 2.4 GHz. Design and simulation processes are carried out with the aid of the HFSS (High Frequency Structural Simulator). The proposed antenna is designed on a

1.59 mm thick Rogers TMM 4 ™ with a relative permittivity of 4.5. and achieve a gain of 4.96 dB with a return loss of -27.50 dB. The key parameters like -Return loss, Input impedance, Gain are simulated, analyzed and optimized using HFSS v12.1.

Keywords- Microstrip Antenna, Co-axial probe feed, S Parameter, Return loss, Gain, VSWR (voltage standing wave ratio), WLAN, Ansoft HFSSv12.1

INTRODUCTION

A microstrip patch antenna consist of a radiating patch which is placed above the dielectric substrate and a ground plane is placed on the other side of dielectric substrate. The EM waves firing off the top patch into the substrate and are radiated out into the air after reflecting off the ground plane. The feed of microstrip antenna can have many configurations like microstrip line, coaxial, aperture coupling and proximity coupling. But microstrip line and the coaxial feeds are relatively easier to fabricate. However, the microstrip line limits the bandwidth to 2 to 5% as spurious radiation increase with the increase in the substrate thickness. Therefore, we are using coaxial feed [1].

disadvantage associated with microstrip antenna is their narrow bandwidth.

In this paper a compact size rectangular microstrip patch antenna is proposed using dielectric substrate as Rogers TMM 4 ™ with r =4.5 and all the dimensions are based on resonant frequency. Various attempts are made to adjust the dimensions of the patch to improve the parameters like bandwidth, return loss, gain along , Ø direction, radiation pattern in 2-D and 3-D, E and H field Distributions , current Distributions using HFSS 12.1.

Fig.1- Co-axial feeding technique

DESIGN SPECIFICATION

The IEEE 802.11 standard was proposed in 1997 for WLANs application. After few years new standard was proposed operating on the 2.4 GHz ISM band (2.4-2.484 GHz) ,is called 802.11b or 802.11 HR(High Rate), which provides a data rate up 11Mbps.The IEEE 802.11y standard was approved in 2008,operating on the 3.6 GHz frequency. The IEEE 802.11a standard was approved in 1999, operating on the 5 GHz ISM band (5.15-5.35 GHz and 5.725-5.825 GHz. The change of band shows that 802.11a and 802.11b products are not compatible. Therefore, the IEEE proposed 802.11g standard which is compatible with both 802.11b and 802.11a technology. The 802.11g standard was accepted in 2003.since 802.11b and 802.11g are using 2.4 GHz frequency band .So a dual band antenna is requirement for WLAN application [2].

The microstrip patch antenna has the advantage of low profile, light weight, small size and low cost. But the main

Fig 2- Designed rectangular microstrip patch antenna

The antenna is simulated on Rogers TMM4 substrate with a dielectric constant of 4.5, the thickness of substrate is

1.59 mm. The length and width of the antenna can be calculated by transmission line method as given below Width of antenna is given by

Table 1- Antenna dimensions

W =

2

2. +1

The effective dielectric constant

(1)

Frequency	2.4 GHz
Height	1.59 mm
Dielectric constant	4.5
Width of patch (W)	37.68 mm
reff	4.17
Extension length (L)	1.2244 mm
Length of patch(L)	28.35 mm

reff = + 1 1

SIMULATION RESULTS

2 2

The extension length is given by

reff + 0.3 W + 0.264

L = 0.412*h* h W

(3)

The simulated result of variation in S11 parameter as a function of frequency for the proposed antenna is shown in fig.3.This antenna is working on the frequency of 2.4 GHz

and the obtained Return Loss of -27.50 dB.

reff 0.258 ) (

h + 0.8

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0.00

XY Plot 1

ve Info

Cur

HFSSDesign2 ANSOFT

The effective length is given by

S

rt_T1))

w avep

port_T1

t(w ave

dB(

S , o

etup1 : Sw eep1

L

(4)

-5.00

dB(St(waveport_T1,waveport_T1))

eff = 2.

Therefore the actual length of the patch is calculated by L = Leff – 2 L (5)

-10.00

Nam

e

X

Y

m1

2.4

030 -2

7.5001

-15.00

By substuting the value of operating frequency 2.4 GHZ, C

= 3×108m/s, r = 4.5 and h = 1.59mm the width of the patch (W) becomes 37.68 mm and Leff = 30.60 mm, substituting eff = 4.17 and the values of W and h, we get L = 1.2244 mm. In final, we obtain the length of the patch using this equation.

L=Leff – 2L (6)

L = 30.60 mm 2.4488 mm = 28.35 mm.

-20.00

-25.00

-30.00

m1

2.00 2.20 2.40 2.60 2.80 3.00

Freq [GHz]

Fig.3 Return loss of design antenna

The transmission line model is applicable to infinite ground planes only. However, for practical considerations, it is essential to have a finite ground plane. Similar results for

The VSWR of rectangular microstrip patch antenna is shown in Fig, 4. The value of VSWR should be less than 2. Here the value of VSWR for the proposed microstrip antenna is 0.7421 at the specified resonating frequency.

finite and infinite ground plane can be obtained if the size of the ground plane is greater than the patch dimensions by approximately six times the substrate thickness all around the periphery. Hence, for this design, the ground plane dimensions would be given as:

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45.00

40.00

35.00

XY Plot 2

HFSSDesign2 ANSOFT

Curve Info dB(VSWRt(w aveport_T1))

Setup1 : Sw eep1

L(g) = 6h+ L (7)

L (g) = 6*(1.59 mm) + 28.35 mm = 37.89 mm W(g) =6h + W (8)

W (g) = 6*(1.59 mm) + 37.68 mm

= 47.22 mm

Hence after calculating all the parameters using the above formulae, the rectangular microstrip patch antenna was designed.

30.00

dB(VSWRt(waveport_T1))

25.00

20.00

15.00

10.00

5.00

0.00

Name	X	Y
m1	2.4040	0.7421

m1

2.00 2.20 2.40 2.60 2.80 3.00

Freq [GHz]

Fig.4- VSWR of design antenna

Fig 5 and 6 show the simulated E-plane gain pattern and radiation pattern for the proposed antenna. In this design a gain of 4.96dB have been investigated at the resonating frequency.

CONCLUSION

In this paper, a small size Microstrip patch antenna for WLAN application by using co-axial probe feed technique is designed. The simulation is carried out using Ansoft

Ansoft LLC

Name	Theta	Ang	Mag
m1	0.0000	p>0.0000	4.9610

-90

-60

-120

-30

-150

Radiation Pattern 1

0

m1

0.00

-10.00

-20.00

-30.00

-180

30

150

60

90

120

HFSSDesign2 ANSOFT

Curve Info dB(GainTotal)

Setup1 : LastAdaptive Freq='2.4GHz' Phi='0deg'

dB(GainTotal) Setup1 : LastAdaptive Freq='2.4GHz' Phi='90deg'

HFSS v 12.1 software. The Return loss of 27.50 dB and Gain of antenna is 4.96 dB. VSWR is 0.7421. The results shows that the proposed antenna suitable for WLAN applications.

REFERENCES

[1]. Balanis, C. A. Microstrip Antennas, Antenna theory, Analysis and Design , Third Edition, john Wiley & Sons, pp-811-876, 2010.

[2]. Richards, W.F., S.E. Davidson, and S.A. Long, Dual band reactively loaded microstrip antenna,IEEE Trans. Ant.Prop., Vol. AP-33,No.5,556-561,1985.

[3]. D.M.Pozar,Microstrip antenna aperture-coupled to a microstripline, Electron. Lett., vol.21,no.2,pp.49-50, jan.1985.

[4]. Michael Paul Civerolo, Aperture Coupled Microstrip Antenna Design and Analysis Thesis, California Polytechnic State University, June 2010.

[5]. J.kaur,R. Khanna and M.Kartikeyan, Design of co-axial fed broadband single layer rectangular microstrip patch antenna for wireless applications J.Engg.Technol., Vol.3,No.2,

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Fig.5- Gain pattern of design antenna

Radiation Pattern 2

0

HFSSDesign2 ANSOFT

[6]. Jun-Hai Cui, Shun-Shi Zhong,Compact microstrip patch antenna with C-shaped slot Microwave Conference, Asia-pacific,2000.

-60

-30

Curve Info

dB(rETotal) Setup1 : LastAdaptive Freq='2.4GHz' Phi='0deg'

dB(rETotal) Setup1 : LastAdaptive Freq='2.4GHz' Phi='90deg'

30

0.00

-10.00

60

-20.00

-30.00

-90 90

-120 120

-150 150

-180

Fig.6- Radiation pattern of design antenna