Comparative Study and Designing of Different Radiating Patch in Microstrip Patch Antenna

IJSRD - International Journal for Scientific Research & Development| Vol. 2, Issue 07, 2014 | ISSN (online): 2321-0613

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Comparative Study and Designing of Different Radiating Patch in

Microstrip Patch Antenna Shivani Chourasia

1 Dr. Soni Changlani

2 Miss. Pooja Gupta

3

1Research Scholar

2Professor

3Assistant Professor

1,2,3Department of Electronics and Communication Engineering

1,2,3Lakshmi Narain College of Technology & Science, Bhopal

Abstract— Microstrip patch antennas are low profile ,

conformable, easy, inexpensive, and versatile in terms of

realization and are thus been widely used in a various useful

applications. This paper discusses different microstrip patch

antennas designed over an operating frequency range 1.5

GHz using the substrate material Flame Retardant 4 (FR-4)

lossy which has a dielectric constant of 4.3. These circuits

were designed using Computer Simulation Technology

(CST) Microwave Studio. The parameters such as return

loss, efficiency and directivity are simulated, analyzed and

compared.

Keywords: Microstrip Patch Antenna, Microstrip line feed,

FR-4 (lossy) material, CST, Patch length, Return loss and

Efficiency

I. INTRODUCTION

A microstrip antenna consists of a very thin metallic patch

placed on conducting ground plane, separated by a dielectric

substrate [2]. A microstrip patch consists of a radiating patch

that may be square, circle, triangle, ring and rectangle etc. on

one side of a dielectric material substrate and a ground plane

on the other side. Microstrip antennas are preferred due to

their numerous advantages such as lightweight, low profile,

easy, inexpensive fabrication and simple modeling. They are

very versatile when chosen for a particular patch shape in

terms of polarization, pattern and resonant frequency [1].

They easily combine to form linear or planar arrays. There

are different feeding techniques in microstrip antenna like

microstrip line feed, coaxial probe feed, aperture coupling

feed, and proximity coupling feed [3-5].

The proposed work includes five microstrip patch

antenna designs that are designed for 1.5 GHz frequency

made by using microstrip line feed and simulated by

CST’10. A basic microstrip patch antenna is shown in Fig.1.

The operating frequency range of the proposed designs fall

under UHF frequency range. The antenna is designed for L-

band application.

Fig. 1: Basic Microstrip Patch Antenna

II. BASIC CHARACTERISTIC

Microstrip patch antennas, as shown in Fig.1, consist of a

very thin metallic strip (patch) placed over a substrate above

the ground plane. There are numerous substrates that can be

used for the design of microstrip antennas, and their

dielectric constant ‘ϵr’ are usually in the range of 2.2 ≤ ϵr ≤

12 [1]. The substrate dielectric constant used for microstrip

antenna is kept generally low (in the lower end of the range)

to reduce fringing field but for less critical applications [7].

Also, variation in dielectric constant is used for impedance

matching [8]. They provide better efficiency, larger

bandwidth, loosely bound fields for radiation into space. The

patch is generally made of conducting material such as

copper and gold.

A. Feed Selection

In this work, microstrip line feed is used as its main

advantage is that it is easy to fabricate, simple to match by

controlling the inset position and rather simple to model. It is

a patch added to the radiating patch using Boolean addition

option in CST software. On simulating the designs for

various feed lengths, it is observed that the feed can be

placed at any place within the patch length to match with its

input impedance (usually 50 ohm) as the difference in the

values of the parameters is negligible [9]. A microstrip line

feed is shown in Fig.2.

Fig. 2: Microstrip Line Feed

An equivalent circuit is shown below in Fig.3 .

Fig. 3: Equivalent Circuit for Microstrip Line Feed

Comparative Study and Designing of Different Radiating Patch in Microstrip Patch Antenna

(IJSRD/Vol. 2/Issue 07/2014/149)


III. MODELING AND DESIGNING OF DIFFERENT MICROSTRIP

PATCH ANTENNA

The conducting patch can take any shape. It may be square,

rectangular, thin strip (dipole), circular, elliptical, triangular,

or any other configuration. The most popular are rectangular,

circular because of the ease of analysis and fabrication, and

their attractive radiation characteristics, especially low cross-

polarization radiation [1]. In this paper, we have taken five

radiating patches which are circle, rectangle, pentagon, I-

shaped and triangle [6-9], [11]. These designs were

simulated and analyzed on CST’10. The comparison was

made on the basis of maximum return loss (in dB) and

efficiency (in percent).

The substrate thickness was kept h = 1.6 mm while

the width and length of the ground plane and substrate is

50mm [10-11]. The substrate material used is FR-4 (lossy)

with dielectric constant ϵr = 4.3 which is less expensive for

fabrication [11-12]. These values were kept constant

throughout the work.

Every time when a patch was designed over the finite

substrate a slot was cut and a microstrip line feed was added

to the patch using tools available in CST’10. A feed was

given at the edge of the patch length. The designs were

simulated for frequency range 0 – 3 GHz.

A brief description is given for each of the five

patches designed.

A. Circular Patch

A circular patch antenna is designed on a finite grounded

dielectric substrate and feed length is varied to obtain the

desired frequency. Also, in this case, by varying radius of the

circular patch the resonant frequency can be varied.

In our work, for different radii, patch length is varied.

When patch length l of the antenna is adjusted at 25.5mm, we

obtained the maximum return loss = -41.606 dB at desired

operating frequency 1.503 GHz. Then efficiency is

calculated for the same frequency using farfield source. A

perspective view of circular microstrip patch antenna is

shown in Fig.4.

Fig. 4: 3D view of circular patch antenna in CST 2010

B. Pentagon Patch

A pentagon patch is designed using segments in a circle

design on a finite grounded dielectric substrate. Each time

for different radii of the circle, patch length l is varied and

the desired results are obtained at l = 40mm. We obtained the

maximum return loss -31.248 dB at desired frequency 1.509

GHz. A perspective view of pentagon microstrip patch

antenna is shown in Fig.5.

C. Rectangular Patch

The rectangular patch is by far most widely used

configuration among all radiating patch due to its ease in

designing. A slot is cut and microstrip line feed is added. The

length is varied and desired results are obtained at l =

37.4mm. A perspective view of rectangular microstrip patch


Fig. 5: 3D view of pentagon microstrip patch antenna in CST

2010

Fig. 6: 3D view of rectangular patch antenna in CST 2010

D. I-shaped Patch

This design is influenced with the idea of miniaturization and

is designed on a finite dielectric substrate placed over a

ground plane. It is easily formed by cutting two slots on both

sides of the reference axis from a rectangular patch. In this

case, the feed is given at the lower end of the I-shape. Width

of the slot and length of the patch is varied.

The desired results are obtained at patch length l =

21.11mm. A perspective view of I-shaped microstrip patch





Fig. 7: 3D view of I-shaped patch antenna in CST 2010

E. Triangular Patch

The triangular patch antenna is also designed using segments

in the circle design placed over substrate. The same

procedure as in case of pentagon microstip patch antenna is

followed and patch length l is varied. The maximum return

loss = -46.259dB is obtained for 1.506 GHz with l = 30mm.

A perspective view of triangular microstrip patch antenna is

shown in Fig.8.

Fig. 7: 3D view of I-shaped patch antenna in CST 2010

A. Triangular Patch

The triangular patch antenna is also designed using segments

in the circle design placed over substrate. The same

procedure as in case of pentagon microstip patch antenna is

followed and patch length l is varied. The maximum return

loss = -46.259dB is obtained for 1.506 GHz with l = 30mm.

A perspective view of triangular microstrip patch antenna is

shown in Fig.8.

Fig. 8: 3D view of triangular patch antenna in CST 2010

IV. RESULT

All five radiating patches are simulated and analyzed. It is

found that the triangular patch antenna had the maximum

return loss = -46.259dB with appreciable efficiency 61.74%.

Fig.8 shows 3D view of triangular microstrip patch antenna.

Also, its return loss graph in Fig.10 depicts the same with the

radiation pattern displayed in Fig.11.

The highest efficiency resulted for rectangular

microstrip patch antenna = 71.34% with return loss = -

26.854 dB that was 20 dB less than that of triangular one.

Also, it was seen that the I-shaped patch antenna was with

minimum return loss = -20.595 dB and lowest efficiency =

41.04%.

The comparison between the five radiating patches in

terms of their various parameters is shown in Table I. The

data is plot in the graph which is shown in Fig.12.

Fig. 9: Polar plot for s-parameter of triangular patch antenna

S.N

o.

Parame

ters

Circl

e

Penta

gon

Rectan

gle

I-

shap

e

Trian

gle

1

Return

Loss

(in dB)

-

41.6

06

-

31.248

-

26.854

-

20.5

95

-

46.25

9

2

Efficien

cy

(in dB)

-

3.46

5

-3.736 -3.376

-

8.90

6

-4.821

3

Efficien

cy

(in

percenta

ge)

70.7

1%

68.82

%

71.34

%

41.0

4%

61.74

%

4

Frequen

cy

(in GHz)

1.50

3 1.509 1.506 1.5 1.506

5

Patch

Length

(in mm)

25.5 40 37.4 21.1

1 30

Table 1: Comparison between Different Micro strip Patch

Antenna Designs




Fig. 10: Simulated graph of triangular patch antenna in CST

2010

Fig. 11: Radiation pattern of Triangular Patch Antenna

Fig. 12: Comparison between Return loss of different

microstrip patch antenna

V. CONCLUSION

From the above results, we can say that for miniaturization at

1.5 GHz that has wide applications in military telemetry,

GPS, mobile phones GSM (Global System for Mobile

Communication) and amateur radio, triangular microstrip

patch antenna provides the best results with good trade-off

between return loss and efficiency. The simulated antenna

using FR-4 (lossy) material as substrate and microstrip line

feeding technique in CST 2010 software is shown in Fig.8.

VI. FUTURE DEVELOPMENT

Though new designs for radiating patch is shown in this

project , it can further be explored by introducing more new

shapes of patch antennas such as linear or array pattern for

the future research. This may also include different type of

substrates with diverse permittivity. Although the return loss

of the patches are increased, there are still rooms for

improvement such as the overall size of the antenna

including the substrate is not much reduced by using this

method, future investigation and research need to be done in

order to reduce overall size of the antenna while maintaining

another antenna performances.

ACKNOWLEDGMENT

I am highly grateful to Miss. Pooja Gupta, Assistant

Professor at LNCTS for giving me invaluable guidance in the

field of antenna and providing me the opportunity to carry

out this work further. I also present my gratitude to Dr. Soni

Changlani, Professor at LNCTS. It was their essential

encouragement that enabled me to pursue my work in this

field.

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Education

Comparative Study and Designing of Different Radiating Patch in Microstrip Patch Antenna