1. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print),
ISSN 0976 – 6553(Online) Volume 5, Issue 3, March (2014), pp. 01-04 © IAEME
1
EFFECT OF FEEDLINE ON RESONANT MODE OF SQUARE MICROSTRIP
ANTENNA
Dr. Nagraj Kulkarni
Department of Electronics,
Government College, Gulbarga-585105,Karkataka, India
ABSTRACT
In this paper the effect of microstripline feed on resonant mode of the square microstrip
antenna is studied. The antenna is constructed with its structure of dimension 8 X 5 X 0.16 cm3
. The
microstripline feed arrangement along with quarter wave transformer is used to excite the proposed
antenna. The antennas exhibits a broadside and linear radiation characteristics. The results are
presented and discussed. This antenna may find its applications in S-band communication system.
Key words: Square Microstrip Antenna, Feedline, Resonance.
1. INTRODUCTION
In the recent years the microstrip antennas (MSAs) have gained popular position in
communication system because of their inherent attractive features like light weight, planar in
structure, ruggedness, different geometries and shapes, easy installation, low fabrication cost [1] etc.
In this paper the effect of microstrip feedline on the resonant modes of the antenna is presented. This
study may be useful for switching of bands applications. This kind of study is found to be rare in the
literature.
2. DESIGNING
The low cost glass epoxy substrate material of area A × B, thickness h = 0.16 cm and
dielectric constant εr = 4.2 is used to fabricate the proposed antenna. The artwork of the antenna is
sketched using computer software Auto CAD to achieve better accuracy. Photolithography process is
used to fabricate the antenna.
INTERNATIONAL JOURNAL OF ELECTRICAL ENGINEERING &
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ISSN 0976 – 6545(Print)
ISSN 0976 – 6553(Online)
Volume 5, Issue 3, March (2014), pp. 01-04
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2. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print),
ISSN 0976 – 6553(Online) Volume 5, Issue 3, March (2014), pp. 01-04 © IAEME
2
Figure 1: Top view geometry SMSA-1
Figure 1 shows the top view geometry of square microstrip antenna (SMSA-1), which is
designed for the resonant frequency of 3.5 GHz using the equations available in the literature for the
design of square microstrip antenna [2]. The SMSA-1 consists of a square radiating patch of equal
length (L) and width (W). The Lf and Wf are the length and width of the microstripline used to
excite the patch. The SMSA-1 has Lf equal to λ0/4. A semi miniature-A (SMA) connector of 50
impedance is used at the tip of the microstripline to feed the microwave power. A quarter wave
transformer of length Lt and width Wt is used to match the impedances between lower radiating edge
of the patch and microstripline feed.
Figure 2: The top view geometry SMSA-2
Figure 2 shows the geometry of modified square microstrip antenna (SMSA-2). The SMSA-2
has the entire dimension same as that of SMSA-1, the modification is made in microstrip feedline
length of SMSA-2, which is reduced to λ0/6. Table 1 gives the design parameters of SMSA and
SMSA-2.
Table 1: Design parameters of SMSA and DOSMSA ( cm )
Antenna L W Lf L’
f Wf Lt Wt A B
SMSA-1 2.04 2.04 2.18 - 0.32 1.09 0.06 5 8
SMSA-2 2.04 2.04 - 1.416 0.32 1.09 0.06 5 8

3. International Journal of Electrical Engineering and Technology (I
ISSN 0976 – 6553(Online) Volume 5, Issue
3. EXPERIMENTAL RESULTS
The Agilent Technologies make
is used to measure the experimental return loss of
Figure 3: Variation of retur
Figure 3 shows the variation of return lo
this figure it is seen that, the SMSA
designed frequency of 3.5 GHz, while SMSA
toward lower frequency side is due to the reduction in length of the
resonant mode helps in switching action of band applications. The bandwidth
SMSA-1 and SMSA-2 are 3.61% and 2.94% respectively.
Figure 4: Radiation pattern of SMSA measured at 3.43 GHz
Figure 5: Radiation pattern of
Fig 4 and 5 show the radiation patterns of
from these figures that, the patterns are broadside and linearly polarized. The cross
is much lower when compared to the co
The gain of SMSA-1 and SMSA-2 is calculated using the absolute gain method given by the relation,
International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976
6553(Online) Volume 5, Issue 3, March (2014), pp. 01-04 © IAEME
3
make (Agilent N5230A: A.06.04.32), Vector Network Analyzer
is used to measure the experimental return loss of SMSA and SMSA-2.
Variation of return loss versus frequency of SMSA-1 and SMSA
shows the variation of return loss versus frequency of SMSA-1 and
SMSA-1 resonates at 3.43 GHz of frequency which is nearer to the
while SMSA-2 resonates at 2.64 GHz. This shift of resonant mode
toward lower frequency side is due to the reduction in length of the microstrip feedline. This shift of
helps in switching action of band applications. The bandwidth BW
and 2.94% respectively.
Radiation pattern of SMSA measured at 3.43 GHz
Radiation pattern of SMSA-2 measured at 2.20 GHz
show the radiation patterns of SMSA-1 and SMSA-2 respectively.
from these figures that, the patterns are broadside and linearly polarized. The cross-polar power level
is much lower when compared to the co-polar power level indicates the broad nature of radiation.
is calculated using the absolute gain method given by the relation,
JEET), ISSN 0976 – 6545(Print),
), Vector Network Analyzer
SMSA-2
nd SMSA-2. From
which is nearer to the
This shift of resonant mode
feedline. This shift of
BW1 and BW2 of
respectively. It can be noted
polar power level
polar power level indicates the broad nature of radiation.
is calculated using the absolute gain method given by the relation,

4. International Journal of Electrical Engineering and Technology (I
ISSN 0976 – 6553(Online) Volume 5, Issue
( ) 10 log - ( ) - 20logG dB G dB dB=
 
 
 
where, Gt is the gain of the pyramidal horn antenna and R is the distance between the
transmitting antenna and the antenna under test (AUT). The power received by AUT, ‘P
power transmitted by standard pyramidal horn antenna ‘P
measured for SMSA-1 is found to be 0.8
0.92 dB.
4. CONCLUSION
From this detailed study, it is concluded that
lower frequency side when length of the
same as that of SMSA-1. The radiation characteristics of
linearly polarized. This antenna may find its a
REFERENCES
1. G. Kumar and K. P. Ray, Broadband Microstrip Antennas, MA
(2003).
2. Antennas: John D Kraus: MacGraw Hill Pub Co.Ltd.
3. Kishan Singh and Shivasharanappa N Mulgi
Compact Square Microstrip Antenna
Electronics and Communication Engineering & Technology (IJECET), Volume
2010, pp. 99 - 106, ISSN Print: 0976
BIO-DATA
Dr. Nagraj K. Kulkarni
Electronics from Gulbarga Universi
respectively. He is working as an Assistant professor
Electronics Government Degree C
field of Microwave Electronics.
International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976
6553(Online) Volume 5, Issue 3, March (2014), pp. 01-04 © IAEME
4
0
( ) 10 log - ( ) - 20log
4
r
t
t
P
G dB G dB dB
P R
λ
π
   
  
  
(2)
is the gain of the pyramidal horn antenna and R is the distance between the
transmitting antenna and the antenna under test (AUT). The power received by AUT, ‘P
power transmitted by standard pyramidal horn antenna ‘Pt’ is measured independently.
is found to be 0.8 dB maximum and the peak gain of SMSA
From this detailed study, it is concluded that the resonant mode of SMSA
lower frequency side when length of the microstrip feedline is reduced keeping all other dimensions
The radiation characteristics of SMSA-1 and SMSA-2 are broadside and
This antenna may find its applications in S-band communication system.
P. Ray, Broadband Microstrip Antennas, MA: Artech House, Norwood,
: MacGraw Hill Pub Co.Ltd.
Shivasharanappa N Mulgi, “Complementary-Symmetric Corner Truncated
Compact Square Microstrip Antenna for Wide Band Operation”, International Journal of
Electronics and Communication Engineering & Technology (IJECET), Volume
, ISSN Print: 0976- 6464, ISSN Online: 0976 –6472.
Kulkarni received his M.Sc, M.Phil and Ph. D degree in Applied
Electronics from Gulbarga University Gulbarga in the year 1995,
respectively. He is working as an Assistant professor and Head, in the Department of
Electronics Government Degree College Gulbarga. He is an active researcher
field of Microwave Electronics.
JEET), ISSN 0976 – 6545(Print),
(2)
is the gain of the pyramidal horn antenna and R is the distance between the
transmitting antenna and the antenna under test (AUT). The power received by AUT, ‘Pr’ and the
’ is measured independently. The gain
SMSA-2 is found to be
of SMSA-2 shifts towards
feedline is reduced keeping all other dimensions
are broadside and
communication system.
: Artech House, Norwood,
Symmetric Corner Truncated
”, International Journal of
Electronics and Communication Engineering & Technology (IJECET), Volume 1, Issue 1,
degree in Applied
ty Gulbarga in the year 1995, 1996 and 2014
in the Department of
active researcher in the