Parametric Analysis and Design Optimization Investigation of a Single Layer Proximity Fed Array Antenna with Slotted Ground Plane

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 09 Issue: 05 | May 2022 www.irjet.net p-ISSN: 2395-0072
© 2022, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 493
Parametric Analysis and Design Optimization Investigation of a Single
Layer Proximity Fed Array Antenna with Slotted Ground Plane
Jacob Abraham
Associate Professor, Department of Electronics
B P C College, Piravom P.O, Eranakulam, Kerala, India, tjacobabra@gmail.com
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Abstract - A In this paper, a microstrippatcharrayantenna
configuration with a new coupling method is presented. Basic
microstrip patch array antenna configuration consisting of a
pair of radiating patches coupled in close proximity to a
microstrip feed line in the same plane along with a slotted
ground plane. By employing directly coupled microstrippatch
to the non-radiating edges of the each microstrip patch of the
basic configuration, enhancement in bandwidth and gain is
achieved with dual band operation. Parametric analyseswere
performed using CST Microwave Studio simulator to
understand effect of various antenna dimension parameters.
This microstrip patch array provides resonances at two
frequencies of 2.468GHz and 3.616GHz. The proposed single
layer proximity fed array antenna withslotted groundplaneis
suitable for WLAN and WiMAX. This array antenna
configuration has a measured gain of 9.4 dBi and 6.03dBi
respectively with impedance bandwidth of 4.41% and 5.66%
respectively across first and second band. The simulated
results are in good agreement with the experimental results.
Key Words: microstrip patch array, proximity feed, coupled
parasitic patch, parametric analysis, slotted ground plane .
1. INTRODUCTION
Due to rapid development in the field of wireless
communication technology the demand for compact and
small size antennas are becomes higher. Microstrip patch
antennas are well suited for the demand. The microstrip
antenna consists of a radiating patch on one side of a
dielectric substrate and a ground plane on the other side.
Microstrip patch antennas are extensively used in satellite,
wireless and mobile communication applications due to
advantages like light weight, conformabletoplanarandnon-
planar surfaces, inexpensive to manufacture and
mechanically robust when mounted on rigidsurfaces.One of
the major requirements for modern communicationdevices
is to operate at wider band so that the antenna can support
high speed internet, multimedia communication and many
other broadband services. However, microstrip patch
antennas have inherent limitations on narrow impedance
bandwidth and low gain.
To overcome the inherent limitation of narrow impedance
bandwidth and low gain of microstrip antenna many
techniques have been suggested and investigated. Some of
the reported techniques used to enhance impedance
bandwidth of microstrippatchantennasarebyusingstacked
parasitic technique [1], microstrip line electromagnetically
coupled to antenna [2], and modified shaped patch antenna
[3]. Traditionally each antenna operates in a single band,
where different antennas are required for various
applications. It will cause a limited space and place problem.
In order to overcome this problem, multiband antenna can
be used, in which a single antenna can operate at many
frequency bands. Some of the techniques used to develop
dual band microstrip patch antenna are slot loaded patch
antenna [4], using fractal geometries in designing patch
structure [5] and by using a pair of L slits in the ground [6].
Another important limitation with microstrippatchantenna
is its low gain. Several methods are reported to increase the
gain of antenna. Array configuration was effectivelyusedfor
the enhancement of gain in microstrip patch antenna [7].
Some of the other methods used to enhance gain includeuse
of air substrate [8] and resonance method which involves
use of a superstrate [9].
One of the commonly used methods to enhance bandwidth
and gain of microstrip patch antenna simultaneously is by
using the concept of gap coupled parasitic elements [10]. A
novel microstrip patch antenna configuration consists of a
pair of square radiating patches coupled in close proximity
to a microstrip line in the same side and a coupling arrow
shaped slot on the other side is reported in [11]. Generally
defected ground structure is implemented in microstrip
antenna for various applications like mutual coupling
reduction inantenna array,miniaturizedantennas,harmonic
suppression and cross polar reduction [12]. In the proposed
work the microstrip feed line is used to excite the radiating
patches through a tapered arrow dumb-bell shaped slot on
the ground plane. The defected geometry etched in the
ground plane disturbs its current distribution. This
distribution affects transmission line characteristics, which
causes an increase in effective capacitance and inductance
results in coupling more energy to the radiating patches.
Recently a number of papers on dual band antennas were
reported for WLAN/WiMAX applications which are popular
networks to access the internet [13-15]. Although this
antenna demonstrates their own merits, they have either
limited bandwidth or limited gain. The antenna proposed
here can be used for WLAN/ WiMAX application with
enhanced bandwidth and better gain.

In this paper a microstrip patch array antenna
configurations is presented wereadditions radiatingpatches
are directly coupled to the non-radiating edges of another
radiating element. The basic array antenna configuration
that consists of two rectangular radiating patches,whichare
electromagnetically coupled to the microstrip line in the
same plane and a defected ground plane. The feeding
technique used in this work is similar to the one reported in
[11]. Additional patches are directly coupled to the non-
radiating edges to enhance bandwidth and gain, which
results in the formation of novel array antenna
configuration. The coupling patch elementshavingthesame
dimension as that of driven patch are coupled to the non-
radiating edges of the driven patch through a narrow strip.
With the introduction of two coupling patch elements the
proposed novel microstrip array antenna shows dual band
characteristics, improved gain and impedance bandwidth is
enhanced by a significant level.
2. ANTENNA CONFIGURATION
The microstrip patch array antennashavebeendesignedand
fabricated on FR-4 substrate with Ɛr of 4.3, loss tangent of
0.001 with height h of 1.6 mm. In this array configuration a
microstrip feed line is centrally placed on the upper side of
the substrate. On either sides of the centrallyplacedfeedline,
two radiating elements are etched. All four radiating
elements have dimensions. To enhance electromagnetic
coupling from the feed line to the radiating elements a slot is
etched in the ground plane. The spacing between the nearest
edges of the patches is kept at λ/12 and the separation
between the center points of the patches is 3λ/8. The
proximity coupled feed method is used to excite the two
radiating patches.
The length and width of each radiating patches are designed
for 2.45 GHz operation. The back side of the substrate has a
metallic ground plane with a tapered arrow head dumb-bell
shaped slot. Second Patch oneithersidesaredirectlycoupled
to the non-radiating edges ofthe firstarrayelementsthrough
a narrow strip. The dimensionsofthecoupledpatcharesame
as that of the radiating patch. The top view and bottom view
of the proposed array antenna is shown in Figure 1. The
optimized dimensions of the proposed capacitive coupled
microstriparray antenna with pairofradiatingpatchesalong
with directly coupled patch are given in Table 1. Thewidthof
the narrow strip line used to couple radiating and coupled
patch is 5mm and the length of the fed line is 45mm. The
proposed antenna performance has been studied using CST
microwave simulation software. To verify the proposed
antenna an experimental prototype was designed fabricated
and measured.
(a) top view
(b) bottom view
Fig -1: Geometry of the proposed single layer proximity
fed array antenna with slotted ground plane
Table -1: Optimized dimensions of the proposed antenna
with coupled parasitic patches.(Units: mm)
SW 180 PW 34 G 3.5
SL 60 PL 27.6 CG 1
Fw 3.02 Dw 4 WS 5
DL1 40 DL2 18 Dh 32
3. PARAMETRIC ANALYSIS
The parametric analysis of the proposed single layer
proximity fed array antenna with slotted ground plane is
conducted and effects of various antenna parameters on the
antenna characteristics are studied. The results and
discussion on various parametric studiesareprovidedinthis
section. The parametric analysis is carried out using CST
microwave studio.
3.1 Effect of feed length
Figure 2, plots the antenna return losses characteristics as
length of microstrip feed line fL, is varied from 44 mm to 47
mm. It is observed that both the resonances remain almost
unaltered. It is also observed that when the fed length
increases the return loss of the lower resonant frequency
degrades while that of the upper band improves. The
bandwidth is found to be stable for the upper band while it
decreases in the case of lower band as fed length increases.

From the simulation studies the microstrip feed line length
FL, is chosen as 45 mm.
Fig – 2: Simulated return loss characteristics of the
proposed single layer proximity fed array antenna with
slotted ground plane for various feed length FL with rest of
the parameters as in Table 1.
3.2 Effect of Coupling Gap G
Figure 3, plots the antenna return losses characteristics
as G, gap between the microstrip feed line and patch edge is
varied from 2 mm to 5 mm. It is observed that in the case of
lower resonance a shift towards higher range can be noted
with an increase in lower resonant frequency from 2.43GHz
to 2.47GHz. It is also observed that when the fed gap
becomes 5mm, the return loss of the lower resonant
frequency degrades to below -10dB.
slotted ground plane for various coupling gap G with rest
of the parameters as in Table 1.
The bandwidth is found to be decreasing for the lower band
from 95MHz to 42 MHz as the gap increases. But the second
resonant frequency is observed to be slightly reduce from
3.62 GHz to 3,54 GHz as G is Increased .It is also noted that
when the fed gap becomes 4 mm the return loss across the
upper resonant frequency degrades to below -10dB level.
Bandwidth is almost stable for variations in G. From the
simulation studies the value of fed gap G is chosen as 3.5
mm.
3.3 Effect of Patch Length PL
The effect of patch length PL over the resonantfrequenciesis
illustrated in the Figure 4. The length of all four radiating
patches are varied simultaneously from 26.6mm to 30.6mm
and found that the second resonant frequency remains
unaltered while the first resonant band is shifted from 2.55
GHz to 2.34 GHz. It is also observed that when the length of
the radiating patches becomes 30.6 mm the return loss of
the lower resonance degrades to below -10dB. The
variations in PL do not make any changes to upper
bandwidth. From the simulation studies the length of
parasitic patches PL, is chosen as 27.6 mm.
slotted ground plane for various patch length PL with rest
3.4 Effect of Patch Width Pw
The effect of patch width Pw over the resonant frequencies
is illustrated in the Figure 5. The width of the all four
radiating patches are varied simultaneously from 33 mm to
37mm and found that the both the resonant frequencies
remains unaltered. It is also observed thatwhenthewidthof
the radiating patches increases the return loss of the lower
resonance reduces towards -10dBlevel.Thevariationsin Pw
do not make any changes to both lower and upper
bandwidths. From the simulation studies the width of all
four radiating patches Pw, is chosen as 34 mm.

slotted ground plane for various patch width PW with rest
3.5 Effect of Slot Height Dh
The effect of slot height Dh over the resonant frequencies is
illustrated in the Figure 6. The height of theslotetchedinthe
ground plane is varied from 28 mm to 34 mm and foundthat
the lower resonant frequency remains unaltered up to
33mm. It is observed that when Dh, becomes 34 mm the
lower resonance band splits in to two closely spaced bands.
The bandwidth of the lower resonance increases with Dh.
The upper resonance frequencyslightlyshiftstowardslower
side as the height of the slot increases. It is also noted that
the when the height of the slot becomes 30mm or less the
return loss of the upper resonance band degrades and
become less than -10dB level.
slotted ground plane for various slot height Dh with rest of
the parameters as in Table 1.
The variations in Dh do not make any changes to upper
bandwidth. From the simulationstudiestheheightoftheslot
etched in the ground plane Dh, is chosen as 32 mm.
3.6 Effect of Slot Length DL1
The effect of slot length DL1 over the resonant frequencies is
illustrated in the Figure 7. The length of theslotetchedinthe
ground plane is varied from 36 mm to 42 mm and foundthat
the second resonant frequency remains unaltered while the
first resonant frequency slightly shifts towards right side. It
is also observed that when the length of the slot becomes 42
mm the return loss of the lower resonant frequency
degrades to nearly -10dB along with reduced bandwidth.
The variations in DL1 do not make any changes to upper
bandwidth. From the simulationstudiesthelengthoftheslot
etched in the ground plane DL1, is chosen as 40 mm.
slotted ground plane for various slot length DL1 with rest
4. RESULTS AND DISCUSSION
To verify the simulated results prototype of the simulated
antenna with optimized dimensions as shown in Table 1 is
fabricated and tested. Figure 8,showsthephotographsof the
fabricated single layer proximity fed array antenna with
slotted ground plane. The antenna is etched on a FR 4
substrate having thickness of 1.6mm, loss tangent of 0.001
and with a dielectric constant of 4.3. FR 4 is used because it
is very cheap and has excellent mechanical properties. The
fabricated microstrip patch array is energized
electromagnetically using the commercially available 50Ω
SMA coaxial connector. Return losscharacteristics,radiation
patterns and gain are measured. Experimental verification
was carried out using Agilent network analyzer E5071C.

(a) top view
(b) bottom view
Fig -8: Photograph of the fabricated single layer proximity
fed array antenna with slotted ground plane. (a) top view
and (b) bottom view
4.1 Return Loss Characteristics
Figure 9, shows the measured S11variations with frequency
of the proposed single layer proximity fed array antenna
with slotted ground plane.
Fig- 9: Measured and simulated return loss characteristics
of the proposed single layer proximity fed array antenna
with slotted ground plane for dual band applications with
dimensions as shown in table 1
The measured -10dB impedance bandwidth of theproposed
single layer proximity fed array antenna withslottedground
plane for the lower band is 109MHz (2.408-2517GHz) or
4.41% with peak resonance at 2.468GHz and for the upper
band is 208MHz (3.586-3.794GHz) or5.66%withresonance
at 3.676GHz. The simulated band widths are 59.8MHz and
173 MHz respectively across lower and upper operating
bands. The operating band of the proposed antenna make it
suitable of 2.45 GHz (WLAN) and upper bandcanbeusedfor
3.5 GHz (WiMAX) applications.
4.2 3 D Radiation Pattern
The simulated three dimensional radiation patters of the
slotted ground plane are depicted in the Figure 10.
(a) (b)
Fig – 10: Simulated 3D radiation pattern of the proposed
single layer proximity fed array antenna with slotted
ground plane (with parameters as in Table 1) (a) at
2.459GHz and (b) at 3.593GHz
4.3 Measured Radiation Pattern Characteristics
Standard measurement techniques are used to plot the
radiation characteristics of the proposed single layer
proximity fed array antenna with slotted ground plane. The
far field radiation patterns of the dual band microstrip array
antenna in the E plane (y-z plane) and H plane (x-z plane)
are plotted at the frequencies of 2.468 GHz and 3.676 GHz is
shown in Figure 11 and Figure12respectively.Theradiation
pattern data are normalized in order to plottheco-polarand
cross polar patterns in one graph. At the lower resonant
frequency (2.468 GHz) the maximumpowerwasreceived by
the antenna at the bore sight direction while at the upper
resonant frequency (3.676 GHz) the maximum power was
received at angle 360 with respect to bore sight. The half
power beam width [HPBW] of the antenna in the lower
resonant frequency is of the order of 1130 in E plane and 920
in H plane respectively. The HPBW of the antenna at the
lower resonating frequency is of the order of 910 in E plane
and 790 in H plane respectively. It is also noted that
reasonably higher cross polarization level was seen across
the second operating frequency. The upper band
characteristics will be found useful in non-line of sight
applications.

(a) (b)
Fig – 11: Normalized radiation patterns of the antenna at
resonant frequency 2.468 GHz (a) E plane (b) H plane
(co-polarized, solid line and cross polarized, dashed line).
(a) (b)
Fig – 12: Normalized radiation patterns of the antenna at
resonant frequency 3,676 GHz (a) E plane (b) H plane
(co-polarized, solid line and cross polarized, dashed line).
4.4 Gain Variations Across the Bands
The measured gain of the proposed single layer proximity
fed array antenna with slotted ground plane at first
resonance frequency is 9.16 dBi and it is comparable with
the simulated gain, which is 9.31 dBi. While the simulated
and measured gains at the second resonant frequencies are
6.03dbi and 6.16dbi respectively.
(a) (b)
Fig -13: Measured gain with frequency of the proposed
single layer proximity fed array antenna with slotted
ground plane at (a) first band and (b) second band
Figure 13, depicts measured gain variations across the
operating frequency bands. Table 2 shows extracted
parameters of the proposed dual band antenna at
corresponding resonant frequencies.
Table 2: Extracted parameters of the proposed dual band
array antenna with slotted ground plane
Parameters Frequency at
2.459GHz
Frequency at
3.593GHz
Values Values
Electric energy density 0.00133J/m3 0.00134J/m3
Magnetic energy density 0.00319J/m3 0.00256J/m3
H field peak in x direction 43.3357 A/m 41.8739 A/m
H field peak in y direction 25.4782 A/m 23.8752 A/m
H field peak in z direction 77.1463 A/m 72.4792 A/m
E field peak in x direction 5438.42 V/m 5397.49 V/m
E field peak in y direction 9864.27 V/m 9811.34 V/m
E field peak in z direction 9167.28 V/m 9263.67 V/m
5. CONCLUSIONS
A new dual band single layer proximity fed array antenna
with slotted ground plane is developed and its operating
performances were analyzed. Bothsimulatedandmeasured
results on the array antenna structure demonstrate good
results with good impedance matching. Furthermore, the
gains at both resonating frequenciesareconsiderablyhigher
with 9.16dBi and 6.03dBi respectively. The results from this
research work will contribute a new array configuration
towards the use of wireless communication system,
especially for WLAN and WiMAX applications
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BIOGRAPHIES
Dr. Jacob Abraham is working as
an Associate Professor in the
Department of Electronics,
Baselios Poulose II Catholicos
College [NAAC “A” grade] an aided
institution affiliated to Mahatma
Gandhi University, Kerala, India.
He has more than twentyfive years
of teaching experience. He
obtained his B. Tech in Electronics
and Communication Engineering
from Mahatma Gandhi University,
M. Tech in Optoelectronics from
Kerala University and PhD in
Microstrip Antennas and Arrays
from Mahatma Gandhi University,
Kerala, India. He has published
around 16 papers in the reputed
indexed international journalsand
more than 25 papers presented in
national and international
conferences. Besides he has
contributed three book chapters
also. He also served as editor ofthe
book titled “Recent Developments
in Electronics and Communication
Engineering” published by IOT
Academy. He has also authored a
text book on Digital Electronics
from Sara Book Publications. He
also served as a member board of
studies of UG Electronics and as

chairman expert committee for PG
[Electronics] Syllabus revision of
Mahatma Gandhi University.
Currently he is a member of
Academic Council of Mahatma
Gandhi University, Kottayam
Kerala. He has successfully
completed one minor projects
funded by University Grants
Commission (UGC). He also served
as convener of the UGC sponsored
national seminar titled “Modern
Trends in Electronic
Communication and Signal
Processing”. His research area
includes Microwave Engineering,
Printed Antennas, Fractal
Antennas, IoT and electric vehicle
control and charging. He is life
member of ILA and ISCA.

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