International Journal of Scientific and Research Publications, Volume 2, Issue 2, February 2012 1 ISSN 2250-3153

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Comparative Analysis of Microstrip Coaxial Fed, Inset

Fed and Edge Fed Antenna Operating at Fixed

Frequency

B. Jyothi, B.T.P.Madhav, V.V.S. Murthy, P. Syam Sundar, VGKM Pisipati

Department of ECE, K L University, Guntur DT, AP, India

Abstract- There are so many techniques are available for

feeding the microstrip patch antennas and each are having their

own significance and impact on these antennas. The functional

characteristics and output parameters of these microstrip

antennas will be affected by choosing different feeding

techniques. This paper deals with the comparative analysis of

coaxial, inset and edge fed MSPA’s with their simulated

performance characteristics. All the three models are designed

and simulated using Finite Element Method based antenna

designing software Ansoft HFSS.

Index Terms- coaxial feeding, inset feeding, edge feeding,

FEM.

I. INTRODUCTION

icrostrip patch Antennas has various advantages such as

low profile, light weight, easy fabrication. Feed line is

used for excite to radiate by direct or indirect contact. Microstrip

patch antennas can be fed in a variety of ways.1.Contacting

2.Non-Contacting.

In contacting method the RF power is fed directly to the

radiating patch using a connected element, they are microstrip

feed and coaxial feed [1].

In Non Contacting method, electromagnetic coupling is done

to transfer the power between the feed line and the radiating

patch, they are Aperture coupled feed and Proximity coupled

feed [2].

II. FEEDING TECHNIQUES

Microstrip line feed is one of the easier methods to fabricate as

it is a just conducting strip connecting to the patch and therefore

can be consider as extension of patch. It is simple to model and

easy to match by controlling the inset position. The disadvantage

of this method is that as substrate thickness increases, surface

wave and spurious feed radiation increases which limit the

bandwidth [3-4].

In Coaxial feeding, the inner conductor of the coaxial is

attached to the radiation patch of the antenna while the outer

conductor is connected to the ground plane. The main advantages

of this method are easy to fabricate, easy to match and low

spurious radiation [5-6].

Aperture coupling consist of two different substrate separated

by a ground plane. On the bottom side of lower substrate there is

a microstrip feed line whose energy is coupled to the patch

through a slot on the ground plane separating two substrates. Top

substrate uses a thick low dielectric constant substrate, and the

bottom substrate uses high dielectric substrate. The ground plane,

which is in the middle, isolates the feed from radiation element

and minimizes interference of spurious radiation for pattern

formation and polarization. The main advantage of this method is

allows independent of feed mechanism element [7-8].

Proximity coupling has the largest bandwidth, has low

spurious radiation. Length of feeding stub and width-to-length

ratio of patch is used to match

Fig. 1 Coaxial Fed Rectangular Patch Antenna

Fig. 2 Inset Fed Rectangular Patch Antenna

M

International Journal of Scientific and Research Publications, Volume 2, Issue 2, February 2012 2

ISSN 2250-3153

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Fig. 3 Edge Fed Rectangular Patch Antenna

Figure (1) shows the coaxial fed Microstrip rectangular patch

antenna designed to work at 5.2 GHz. Figure (2) shows the Inset

fed microstrip rectangular patch antenna designed to work at 5.2

GHz. Figure (3) shows the Edge fed microstrip rectangular patch

antenna designed to work at 5.2 GHz.

III. RESULTS AND ANALYSIS

Fig. 4 Return Loss Vs Frequency

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Fig. 5 2D Gain

Return loss is the difference, in dB, between the forward and

reflected power measured at a given point in an RF system. A

mismatched antenna reflects some of the incident power back

toward the transmitter and since this reflected wave is traveling

in the opposite direction as the incident wave, there will be some

points along the cable where the two waves are in phase and

other points where the waves are out of phase. The return loss

obtained for three models is shown in figure (4). The return loss

obtained for three models are -26.52, -12.02, -10.87 dB

respectively. The return loss is increasing when we select edge

feeding and inset feeding compared with coaxial feeding.

Fig. 6 Contour Plot for radiation pattern in Phi direction

The gain of the antenna in given direction is the amount of

energy radiated in that direction compared to the energy an

isotropic antenna would radiate in the same direction when

driven with the same input power. The direction in which the

antenna is radiating its most of its power is called its gain. The

gain obtained for three models are 7.93, 7.95 and 7.45 dB

respectively. The gain is marginally high for the inset feed

antenna and slightly less for edge feed antenna.

The radiation pattern of the antenna can be defined as the spatial

distribution of a quantity that characterizes the electromagnetic

field generated by an antenna. Figure (6) and (7) shows the

radiation pattern contour plots of the antenna in phi and theta

directions. The contour plots represent the radiation pattern in

elevation and azimuthal angles. The radiation pattern represents

the energy radiated from the antenna in each direction, often

pictorially.

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Mesh generation is the practice of generating a polygonal or

polyhedral mesh that approximates a geometric domain to the

highest possible degree of accuracy. The term "grid generation"

is often used interchangeably. Typical uses are for rendering to a

computer screen or for physical simulation such as finite element

analysis or computational fluid dynamics. Figure (8) shows the

current distribution on the patch of the antenna for three models

of feeding.

Fig. 7 Contour Plot for radiation pattern in Theta direction

Fig. 8 Current Distribution over the patch in three types of feeding

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Table (1) and (2) shows the antenna additional parameters and the maximum field data.

Antenna Parameters

Table 1: Antenna Parameters

Quantity Probe-fed(Value/Units) Edge-fed(Value/Units) Inset-fed(Value/Units)

Max U 0.0031973W/Sr 0.0032096W/Sr 0.004259W/Sr

Peak Directivity 6.3038 5.7038 6.3612

Peak Gain 6.2126 5.5625 6.2422

Peak Realized Gain 4.0711 4.0334 5.3522

Radiated Power 0.0063739W 0.0070715W 0.0084138W

Accepted Power 0.0064675W 0.0072511W 0.0085742W

Incident Power 0.0098694W 0.01W 0.01W

Radiation Efficiency 0.98553 0.97522 0.98129

Front to Back Ratio 144.83 83.426 386.19

Maximum Field Data

Table 2: Maximum Field Data

rE field Probe -fed

(value/units)

Probe-

fed

(at phi)

Probe-

fed (at

theta)

Edge-fed

(value/units)

Edge-

fed (at

phi)

Edge-

fed

(at

theta)

Insert-fed

(value/units)

Insert-

fed

(at phi)

Insert-fed

(at theta)

TOTAL 1.5527v 90deg -4deg 1.5557v 90deg 6deg 1.729v 90deg 6deg

X 0.34194v 135deg 52deg 0.29898v 130deg 60deg 0.31079v 45deg 56deg

Y 1.5506v 85deg -2deg 1.5518v 95deg 2deg 1.7863v 85deg 4deg

Z 0.74523v 90deg -44deg 0.82391v 90deg 46deg 0.85778v 90deg 44deg

PHI 1.5473v 180deg 0deg 1.5472v 180deg 0deg 1.7761v 180deg 0deg

THETA 1.5527v 90deg -4deg 1.5556v 90deg 6deg 1.792v 90deg 6deg

LHCP 1.1365v 10deg -10deg 1.1116v 125deg 16deg 1.2736v 125deg 8deg

RHCP 1.131v 170deg -10deg 1.112v 55deg 16deg 1.277v 55deg 8deg

IV. CONCLUSION

Different types of feeding techniques are applied to

rectangular patch antenna and its performance characteristics

are observed at fixed frequency. Coaxial feeding is giving

better return loss and inset feeding is giving superior gain

compared to the other feeding techniques. Radiation efficiency

is showing better result for coaxial feeding and radiated power

is high for the case of edge feeding. The inset and edge

feeding are easier in construction. Overall the coaxial feeding

is giving better input impedance and other parameters

compared to other different feeding techniques. The only

problem is with the coaxial feeding is its design complexity.

ACKNOWLEDGEMENT

The authors like to express their thanks to the department

of ECE and management of K L University for their

continuous support and encouragement during this work.

Further, VGKM Pisipati acknowledges the financial support

of Department of Science and Technology through the grant

No.SR/S2/CMP-0071/2008.

REFERENCES

[1] P.J.Soh, M.K.A.Rahim, A.Asrokin & M.Z.A.Abdul Aziz, Design, Modeling, and performance comparison of feeding techniques for a

microstrip patch antenna. Journal Teknologi, 47 (D) Dis.2007: 103-120

universiti technologi Malaysia. [2] Kazuhiro Kitatani, Sadahiko Yamamoto. Coaxial feed-type microstrip

patch antenna with variable antenna height. Electronics and

Communications in Japan (Part I: Communications), Volume 87, Issue 2, pages 10–16, February 2004.

[3] B.T.P.Madhav, K.Praveen Kumar, N.Srinivas Sri Chaitanya, P.Rakesh

Kumar, N.V.K.Ramesh, B.Nagaraju Nayak, Comparative Analysis of Shorting Pin and Shorting Plate Models for Size Reduction in the

Microstrip Patch Antennas, International Journal of Communication Engineering Applications-IJCEA,ISSN: 2230-8504; e-ISSN-2230-

8512Vol 02, Issue 04; July 2011

[4] K. F. Lee, K. M. Luk, K. F. Tong, S. M. Shum, T. Huynh, and R. Q. Lee, “Experimental and simulation studies of the coaxially fed U-slot

rectangular patch antenna,” Inst. Elect. Eng. Microwave Antennas

Propagation, vol. 144, no. 5, pp. 354–358, Oct. 1997. [5] Y. X. Guo, C. L. Mak, K. M. Luk, and K. F. Lee, “Analysis and design

of L-probe proximity fed-patch antennas,” IEEE Trans. Antennas

Propagat., vol. 49, pp. 145–149, Feb. 2001. [6] K. M. Luk, C. L. Mak, Y. L. Chow, and K. F. Lee, “Broadband

microstrip patch antenna,” Electron. Lett., vol. 34, no. 15, pp. 1442–

1443, 1998.

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[7] Zhang, Y.P. and J.J. Wang, 2006. Theory and analysis of differentially-

driven microstrip antennas. IEEE Transactions on Antennas and Propagation, 54(4): 1092-1099.

[8] Mak, C.L. and K.M. Luk, 2000. Experimental study of a microstrip

patch antenna with an L-shaped probe. IEEE Transactions on Antennas and Propagation, 48(5): 77-78.

AUTHORS

First Author – B.T.P.Madhav was born in India, A.P, in 1981. He

received the B.Sc, M.Sc, MBA, M.Tech degrees from Nagarjuna

University, A.P, India in 2001, 2003, 2007, and 2009 respectively.

From 2003-2007 he worked as lecturer and from 2007 to till date he

is working as Assistant Professor in Electronics Engineering. He has

published more than 70 papers in International and National journals.

His research interests include antennas, liquid crystals applications

and wireless communications.

Second Author – B.Jyothi, was born in A.P, India in 1981. She

completed her B.Tech in 2003 from CR Reddy College of

Engineering affiliated to Andhra University. Presently she is pursuing

her M.Tech, in Communications and Radar Systems from K L

University.

Third Author – Prof. VGKM Pisipati was born in India, A.P, in

1944. He received his B.Sc, M.Sc and Ph.D degrees from Andhra

University. Since 1975 he has been with physics department at

Acharya Nagarjuna University as Professor, Head, R&D Director. He

guided 22 PhDs and more than 20 M.Phils. His area of research

includes liquid crystals, nanotechnology and liquid crystals

applications. He visited so many countries and he is having more than

260 International research publications. He served different positions

as academician and successfully completed different projects

sponsored by different government and non-government bodies. He

is having 5 patents to his credit.

Fourth Author – V.V.S.Murthy was born on 02 January, 1981. He

received his B.E. and M.Tech degrees in 2002 and 2006 respectively.

He is a life member of IETE and ISTE. His research areas include

Antennas and Radio wave propagation and optical image processing.

Currently he is working as Associate Professor in ECE department of

K.L.University, Guntur.