International Journal of Scientific & Engineering Research, Volume 3, Issue 11, November-2012 1

ISSN 2229-5518

DESIGN AND SIMULATION OF MICROSTRIP PATCH ARRAYANTENNA FOR WIRELESS COMMUNICATIONS AT 2.4 GHZ

B.SAI SANDEEP S.SREENATH KASHYAP
Assistant Professor Assistant Professor
QIS College of Engineering &Technology Marwadi Education Foundation
Ongole, Andhra Pradesh Rajkot, Gujarat INDIA INDIA Sandeep6sandeep@gmail.com kashyap.foru3@gmail.com

AbstractDue to the existence of growth in development of low cost, less weight, highly reliable, minimal profile antennas for wireless devices, it poses a new challenge for the design of antenna in wireless communications. This paper presents design and simulation of a rectangular micro strip patch array antenna at 2.4 GHz for wireless communications that provides a radiation pattern along a wide angle of beam and achieves a gain of 11.6 dBi.The rectangular micro strip patch antenna was analysed using Ansof/Ansys HFSS and also made a comparision among the different substrates which shows different results based on same parameters.

Keywords-Microstrip patch antenna, Frequency, Gain, Beamwidth,HFSS,Wireless communication.

1. INTRODUCTION

In recent years there is a need for more compact antennas due to rapid decrease in size of personal communication devices.As communication devices become smaller due to greater integration of electronics, the antenna becomes a significantly larger part of the overall package volume. This results in a demand for similar reductions in antenna size. In addition to this, low profile antenna designs are also important for fixed wireless application.The microstrip antennas used in a wide range of applications from communication systems to satellite and biomedical applications.
In order to simplify analysis and performance prediction, the patch is generally square,rectangular,circular, triangular, elliptical or some other common shape.The rectangular microstrip patch antenna is the widely used of all the types of microstrip antennas that are present The substrate material, dimension of antenna, feeding technique will detemines the performance of microstrip antenna.To enhance the gain,the array of patch elements is used instead of single patch.Hence among different feeding techniques,edge fed technique is used for the design of rectangular microstrip patch antenna at
2.4GHzThe substrate material mainly used for design
technique is Rogers RT duroid 5880(tm) with 𝜖r=2.2.The
software tool HFSS is used because it is a high performance
full wave electromagnetic (EM) field simulator for arbitrary
3D volumetric passive device modeling.It integrates simulation, visualization, solid modelling, and automation in an easy to learn environment where solutions to your 3D EM problems are quickly and accurate obtained.

BACKGROUND

A microstrip patch antenna is very simple in the
construction using a conventional microstrip fabrication technique[1].The most two models of the rectangular patch antenna are transmission line model and the cavity model.

Antenna shape

Microstrip patch antenna has a ground plane on the one side of a dielectric substrate which other side has a radiating patch as shown in Fig. (1) A rectangular patch is used as the main radiator. The patch is generally made of conducting material such as copper or gold and can take any possible
shape.Dielectric constant of the substrate (𝜖r) is typically in the range 2.2< 𝜖r <12 [2].

Fig(1) Microstrip antenna
For good antenna performance,a low dielectric constant with thick dielectric substrate is desirable,as it provides better radiation,better efficiency and larger bandwidth.

ANALYSINNG METHOD

Transmission line model depicts the microstrip antenna by two slots of width W and height h seprated by transmission line of length L.The microstrip is a non homogeneous of two dielectrics,typically,substrate and the air .Most of the electric field lines reside some part in the air and rest in the substrate.This results that transmission line

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International Journal of Scientific & Engineering Research, Volume 3, Issue 11, November-2012 2

ISSN 2229-5518

does not support transverse electric-magnetic(TEM) mode of transmission,as phase velocities would be different in substrate and in the air.So,dominant mode of propogation will be the quasi-TEM mode.An effective dielectric
constant(𝜖reff) must be obtained to account for wave propagation in the line and fringing.The value of 𝜖reff must be smaller than 𝜖r, as fringing fields across patch periphery was
not totally included in the substrate ,it also spread in the air as
shown in Fig(2) below.

Fig (2) Electric field lines
To design the patch antenna, following things has to be determined
𝜖reff= Effective dielectric constant
𝜖r = Dielectric constant of substrate
h = Height of dielectric substrate
W = Width of the patch
L = Length of the patch

Assume Fig(3),a rectangular microstrip antenna of width W,length L resting on the height of a substrate h.The coordinate axis was selected as the height along z direction,length along x direction and width along y direction.
Fig (3) Microstrip patch antenna
In order to operate in tne fundamental mode,length of the
patch should be slightly less than λ/2,where λ is the

wavelength equal to λ0/√ .The TM10 implies that field
varies a cycle of λ/2 along the length,and width of the patch

has no variation.

The microstrip patch antenna is represented by two slots, separated by a transmission line of length L and open circuited at both the ends as shown in Fig (4).

Fig (4) Rectangular microstrip antenna
The voltage is maximum along the width of the patch and due to the open ends,the current is minimum. With respect to the ground plane the fields at the edges can be resolved into tangential and normal components.
The normal components of the electric field at the two edges along the width are in opposite directions and thus out of phase as seen in Fig(5). since the patch is λ/2 long and hence they cancel each other in the broadside direction.The tangential components which are in phase, means that the resulting fields combine to give maximum radiated field normal to the surface of the structure. Hence the edges along the width can be represented as two radiating slots, which are λ/2 apart and excited in phase and radiating in the half space above the ground plane. The fringing fields along the width can be modeled as radiating slots and electrically the patch of the microstrip antenna looks greater than its physical dimensions. The dimensions of the patch along its length have now been extended on each end by a distance ΔL.
1.
2. Fig (5) side view of antenna

3.

4. DESIGN CONSIDERATION

5. We have designed an array of rectangular patch antenna of the
center frequency 2.4 GHz, sweeping between 1.2-3.6 GHz.Gain required as 11.5dBi. We have employed a hybrid structure where we are using rogers RT duroid 5880 as a substrate. The three essential parameters for the design of microstrip patch antenna are: 1) Frequency of operation (f 0 ): The resonant frequency of the antenna must be selected appropriately. 2)
Dielectric constant of the substrate (𝜖 r) [3]. 3) Height of
dielectric substrate (H): For the microstrip patch antenna the
height of the dielectric substrate is critical since the antenna should not be bulky. The transmission line model will be used to design the antenna.The edge type feed is used in this design.

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Antenna Design Calculations

A)Frings factor:



( )( )
( )( )
B) Calculation of length:
= - 2

C) For a rectangular Micro strip patch antenna, the resonance
Frequency for any TM10 mode is given as


[( ) ( ) ]

Where m and n are modes along L and W respectively. D)Calculation of width:
For efficient radiation, the width W is given as



E)Calculation of height of dielectric substrate (H):
The equation to determine the height of the dielectric substrate is:


F)Calculation of the ground plane dimensions ( Lg and Wg ):
The transmission line model is applicable to infinite ground planes only. However, for practical considerations, it is essential to have a finite ground plane. It has been shown by [9] that similar results for 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:
L(g)=6h+L=6(12)+46.23mm=118.23mm
W(g)=6h+W=6(12)+62.04mm=134.04mm
Hence after calculating all the parameters using the above formulae,the rectangular microstrip patch antenna was designed.
G) Determination of feed point location:
The feed co-ordinates were calculated Yf =W/2 and Xf=X0
-ΔL where,



X0 = cos-1√ and

Z0 = √

H) Dielectric Substrate

It was found suitable to select a thin dielectric substrate with low dielectric constant by considering the trade-off between the antenna dimensions and its performance.Thin substrate permits to reduce the size and also spurious radiation as surface wave, and low dielectric constant – for higher bandwidth, better efficiency and low power loss. The simulated results were found satisfactory.
Table 1: Dimensions of patch antenna

I) Software tool

The software used to model and simulate the microstrip patch antenna is HFSS. HFSS is a high-performance full-wave electromagnetic(EM) field simulator for arbitrary 3D volumetric passive device modeling that takes advantage of the familiar Microsoft Windows graphical user interface. It integrates simulation,visualization, solid modeling, and automation in an easy-to-learn environment where solutions to your 3D EM problems are quickly and accurately obtained. Ansoft HFSS employs the Finite Element Method (FEM), adaptive meshing, and brilliant graphics to give you unparalleled performance and insight to all of your 3D EM problems. Ansoft HFSS can be used to calculate parameters such as S-Parameters, Resonant Frequency, and Fields[4].

STRUCTURE OF PATCH ANTENNA DESIGN IN HFSS

A)The 2x2 patch array antenna design is shown in below
figure in 3D model.It consists of patch elements on one side of a dielectric substate and a planar ground on the other side.It was assigned with a airbox boundary and virtual radiation to
create far field radiation pattern and assigned with a excitation

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of lumped port.

Fig (6) Design of single patch antenna in HFSS
SIMULATION RESULTS
The 2x2 patch array antenna is simulated using Ansoft HFSS.The parameters evaluated were gain, beamwidth and return loss.

A)Figure of 3D polar plot for patch array antenna

CONCLUSION

Thus the design and simulation of microstrip patch array
antenna was successfully designed and analysed using Ansoft/Ansys HFSS.The performance parameters was achieved with gain 12 dB and beamwidth 40 degrees in E- plane and 26 degrees in H-plane for patch array antenna.The fabrication of this patch array antenna will be our targeted work

Fig(7) 3D polar plot of patch array antenna

From the figure above, the aceived gain was 12.02 dBi for peak gain at 2.4GHz.

B)3D Radiation pattern for patch array antenna

From figure shown below,the beamwidth for patch array

antenna obtained was 40 degrees in E-plane and 26 degrees in H-plane
Fig (8):3D radiation pattern for patch array antenna
C)The return loss for patch array antenna is shown in below figure.The return loss is found to be varying between
2.24GHz to 2.5 GHz.Its value at 2.24 GHz is -18.75 dB and
12.2 dB at 2.4GHz.

ACKNOWLEDGEMENT

Authors are thankful for SRM university for providing
facility in this research work.

REFERENCES

[1] Kin-Lu Wong, Compact and Broadband

Microstrip Antennas, Jon Wiley

& Sons, Inc.,2002

[2]C.A.Balanis.’’Antenna Theory’’,John Wiley &

Sons Inc,1999

[3] D.M.Pozar and B.Kaufman,”Increasing theBandwidth of a MicrostripAntenna by Proximity Coupling”, Electronic Letters, Vol- 23, pp [12-14] April-1987.

[4] www.AnsoftHFSS.com

[5] ’’Comparative Study of Microstrip Patch Antenna for Wireless Communication Application’’Jagdish. M. Rathod,International journal of innovation,Management and Technology,Vol 1,No.2,2010.

[6]”Comparision of performance characterization

in 2x2,3x3 and 4x4 Array Antennas’’IJERA,Vol

1,Issue4,pp2091-2095

0.00

-2.50

Return Loss

moin _patch_arrayantenna ANSOFT

Curve Inf o dB(St(1,1))

Setup1 : Sw eep1

-5.00

-7.50

-10.00

-12.50

-15.00

-17.50

-20.00

1.00 1.50 2.00 2.50 3.00 3.50 4.00

Freq [GHz]

Fig (9): Return loss of patch array antenna
Table 2: Comparision of measured gain,return loss and bandwidth at two frequencies for single patch antenna[5][6].

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