1. International Journal of Electronics and Communication Technology (IJECET),
International Journal of Electronics and Communication Engineering &
Engineering6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEME
ISSN 0976 –
& Technology (IJECET) IJECET
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online)
Volume 1, Number 1, Sep - Oct (2010), pp. 107-116 ©IAEME
© IAEME, http://www.iaeme.com/ijecet.html
DESIGN AND DEVELOPMENT OF MICROSTRIP ARRAY
ANTENNA FOR WIDE DUAL BAND OPERATION
Gangadhar P Maddani
Department of PG Studies and Research in Applied Electronics
Gulbarga University, Gulbarga
E-Mail: gangadharmaddani@rediffmail.com
Sameena N Mahagavin
Department of PG Studies and Research in Applied Electronics
Gulbarga University, Gulbarga
E-Mail: sameena.nm@rediffmail.com
Shivasharanappa N Mulgi
Department of PG Studies and Research in Applied Electronics
Gulbarga University, Gulbarga
E-Mail: s.mulgi@rediffmail.com
ABSTRACT
This paper presents a novel design of slot loaded two elements rectangular
microstrip array antenna (SRMAA) for triple band operation. If the ground plane of
SRMAA is minimized to 48.8% by removing the copper layer on either side of vertical
axis of the substrate from the centre, converts triple-band in to dual-bands. Further, by
reducing the ground plane to 76.8%, the antenna enhances impedance bandwidth of each
operating band in the dual band operation and gives maximum 40.1% and 50% of
impedance bandwidth and enhances the gain from 2.07 to 3.73dB without changing much
the nature of omni directional radiation characteristics. The proposed antennas are simple
in their geometry and are fabricated using low cost glass epoxy substrate material. These
antennas may find applications for the microwave communication systems operating at
IEEE 802.11a (5.15 – 5.35GHz), HIPERLAN/2 (5.725 – 5.825GHz) and X (8 –
12.5GHz) band of frequencies. Details of antenna design are described and experimental
results are discussed.
Keywords: microstrip antenna, array antenna, dual-band, omni directional.
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2. International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEME
1. INTRODUCTION
In recent years, the use and considerable interest in microstrip antennas (MSAs)
has become wide spread because of its significant merits of small size, light weight, low-
profile, low cost and direct integrability with microwave circuits. However, one of the
serious limitations of MSAs is their narrow impedance bandwidth and lower gain.
Several promising techniques are available in the literature for the enhancement of
impedance bandwidth and gain such as use of stacked configuration [1], additional
resonator [2], aperture coupling [3], parasitic patch [4], etc. But these methods require
thick substrate and also increase the area of the antenna.
Further, dual or triple band antennas have gained wide attention in many
microwave communication systems because they avoid the use of separate antennas for
transmit/receive applications for each operating band, particularly in synthetic aperture
radar (SAR) [5]. Various techniques are available in the literature to achieve dual band
operation [6-7]. In this study, a simple slot loaded array technique has been used to
achieve triple band operation. To convert triple band into dual band, the ground plane is
minimized. The enhancement of impedance bandwidth at each operating band and gain is
achieved by using optimum ground plane of the array configuration without changing the
nature of radiation characteristics. This kind of study is rarely found in the literature.
2. DESCRIPTION OF ANTENNA GEOMETRY
Figure 1 Geometry of SRMAA
The proposed antennas are designed using low cost glass epoxy substrate material
of thickness h = 0.16 cm, permittivity εr = 4.2 and area = A×B. The artwork of the
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3. International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEME
proposed antennas is sketched using computer software Auto-CAD 2006 to achieve
better accuracy. The antennas are fabricated using photolithography process.
Figure 1 shows the top view geometry of slot loaded two element rectangular
microstrip array antenna (SRMAA). The length L and width W of the patch is designed
for resonant frequency of 5GHz, using the equations available in the literature for design
of rectangular patch [8]. The rectangular slots are placed at the centre along the length L
of upper non radiating edge of the patch. The half U shaped slots are placed inside the
patch from bottom non radiating edge L at a distance of 1mm. The dimensions of slots
are taken in terms of λo, where λo is free space wavelength in cm. The length LR and
width WR of rectangular slot is taken as λo/8.57 and λo/60 respectively. The dimensions
of half U shaped slot having horizontal length LH and vertical length LV are taken as
λo/30 and λo/8 respectively. The distance D between the two radiating elements from
their centre should be λo/2 for minimum side lobes [9]. But in Fig. 1, D is taken as
λo/2.33 in order to keep the feed line as compact as possible for minimum feed line loss.
Further, when D is less than λo/2.33; it becomes difficult to accommodate the feed
arrangement between the array elements. Hence D = λo/2.33 is treated as optimum in this
case. The parallel feed arrangement has wideband performance over series feed and
hence selected in this case to excite the array elements of Figure 1. The feed arrangement
shown in Figure 1 is a contact feed and has advantage that it can be etched
simultaneously along with antenna elements. The parallel feed arrangement of Figure 1
consists of a 50 microstripline feed of length L50 and width W50 is connected to 100
microstripline feed of length L100 and width W100 to form a two way power divider. A
100 quarter wave matching transformer of length Lt and width Wt is connected between
100 microstripline feed and mid point of the radiating elements in order to ensure
perfect impedance matching. The bottom plane of SRMAA is tight ground plane copper
shielding. The ground plane shielding of SRMAA is minimized to 48.8% with respect to
ground plane area A×B as shown in Figure 2 retaining its top geometry. This antenna is
named as modified ground plane slot loaded two elements rectangular microstrip array
antenna (MRMAA). The size of copper area on the ground plane is taken as A1×B.
Figure 3 shows the bottom view geometry of large modified ground plane slot loaded two
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4. International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEME
elements rectangular microstrip array antenna (LRMAA). The size of copper area on the
ground plane is taken as A2×B which is 76.8% smaller than the area A×B retaining its top
geometry same as that of Figure 1. The various parameters of proposed antennas are
given in Table 1.
Figure 2 Ground plane geometry of MRMAA
Figure 3 Ground plane geometry of LRMAA
Table 1 Design Parameters of Proposed Antennas
Antenna Dimensions Antenna Dimensions
Parameters (cm) Parameters (cm)
A 5.00 L100 0.38
B 3.50 W100 0.07
L 1.41 D 2.56
W 1.86 A1 2.56
Lt 0.38 A2 1.16
Wt 0.015 LR 0.70
L50 1.54 WR 0.10
W50 0.32 LH 0.20
λ0 6.00 LV 0.75
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5. International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEME
3. EXPERIMENTAL RESULTS
The impedance bandwidth over return loss less than −10dB of the proposed
antennas is measured on Vector Network Analyzer (Rohde & Schwarz, Germany make
ZVK model 1127.8651). The variation of return loss versus frequency of SRMAA is as
shown in Figure 4. From this figure, it can be seen that, the antenna resonates for three
bands of frequencies BW1, BW2 and BW3.The impedance bandwidth (BW) at each
operating band is determined by using the equation,
 (f − f ) 
BW =  2 1  ×100 %
 fc 
Where, f1 and f2 are the lower and upper cut-off frequencies of the band
respectively, when its return loss becomes −10dB and fc is the center frequency between
f1 and f2. The magnitude of each operating band BW1, BW2 and BW3 in Figure 4 is found
to be 10.2, 11.7 and 20.64% respectively. The triple bands are due to the independent
resonance of radiating elements and slots on SRMAA.
Figure 4 Variation of return loss verses frequency of SRMAA
The variation of return loss versus frequency of MRMAA is as shown in Figure 5.
From this graph, it can be observed that, the antenna resonates for dual band of
frequencies BW4 and BW5 with corresponding magnitudes of impedance bandwidth is
12.1 and 47% respectively. Further, from this figure, it is clear that the two bands BW1
and BW2 of Figure 4 merges into a single band BW4 as shown in Figure 5. This is due to
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6. International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEME
the effect of reduction of ground plane in MRMAA. However, the bandwidth BW3 shown
in Figure 4 enhances from 20.64% to 47% i.e. BW5 which is evident from Figure 5.
Hence, by modifying the ground plane geometry of SRMAA triple band operation can be
converted into dual band operation with enhanced upper band BW5. Figure 6 shows the
variation of return loss versus frequency of LRMAA. The antenna resonates again for
dual bands BW6 and BW7 and gives maximum impedance bandwidth at each operating
band i.e. BW6 and BW7. The magnitudes of impedance bandwidths of BW6 and BW7 are
found to be 40.1% and 50% respectively. These bandwidths are 94.28% and 6.38% more
when compared to the impedance bandwidths BW4 and BW5 respectively. The
enhancement of impedance bandwidth of LRMAA is due to the effect of reduced ground
plane. This reduced or optimum ground plane acting as secondary slot. The surface
current around the secondary slot perimeter increases the electrical length which account
for decrease in resonant frequency. Hence the patch and slot on the patch resonates close
to each other resulting in enhancement of impedance bandwidth [10].
Figure 5 Variation of return loss verses frequency of MRMAA
The radiation patterns of proposed antennas i.e. antennas under test (AUT) are
measured by connecting a standard pyramidal horn antenna in far field region. The AUT
is connected in receiving mode and is kept in phase with respect to transmitting
pyramidal horn antenna. The power received by AUT is measured from 00 to 3600 with
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7. International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEME
steps of 100. The typical radiation patterns of SRMAA, MRMAA and LRMAA are
measured at 8.5, 7.56 and 4.48GHz respectively. These are shown respectively in Figure
7, 8 and 9. From these figures, it is observed that the patterns are omni directional in
nature. Hence the reduction of ground plane does not affect much on the nature of
radiation characteristics but enhances the impedance bandwidth at each operating band in
the dual band operation.
Figure 6 Variation of return loss verses frequency of LRMAA
Figure 7 Radiation pattern of SRMAA measured at 8.5GHz
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8. International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEME
Figure 8 Radiation pattern of MRMAA measured at 7.56GHz
Figure 9 Radiation pattern of LRMAA measured at 4.48GHz
For the calculation of gain of proposed antennas, the power transmitted Pt by
pyramidal horn antenna and power received Pr by AUT is measured independently. With
the help of these experimental data, the gain G (dB) of AUT is calculated using the
absolute gain method [9],
 Pr   λ0 
( G ) dB=10 log   − ( Gt ) dB − 20 log   dB
 Pt   4πR 
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9. International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEME
Where, Gt is the gain of the pyramidal horn antenna and R is the distance between
the transmitting antenna and the AUT. The maximum gain of SRMAA, MRMAA and
LRMAA are found to be 2.07, 3.65, and 3.73dB respectively. Hence LRMAA gives
highest gain among the proposed antennas.
4. CONCLUSION
From the detailed experimental study, it is concluded that triple band operation
with omni directional radiation pattern of antenna is achieved by designing SRMAA. By
reducing area of the ground plane by 48.8% with respect to the ground plane area of
SRMAA, triple band operation can be converted into dual band operation. Further, if the
ground plane area of SRMAA is reduced to 76.8% the maximum enhancement of
impedance bandwidth at each operating band in the dual band operation is possible
without much changing the nature of omni directional radiation characteristics. This
technique also enhances the gain from 2.07 to 3.73dB. The proposed antennas are simple
in their design, fabrication and they use low cost substrate material. These antennas may
find applications for microwave communication systems operating at IEEE802.11a (5.15
– 5.35GHz), HIPERLAN/2 (5.725 – 5.825GHz) and X (8 – 12.5GHz) band of
frequencies.
ACKNOWLEDGEMENTS
The authors would like to thank the authorities of Dept. of Sc. & Tech. (DST),
Govt. of India, New Delhi, for sanctioning Network Analyzer to this Department under
FIST project.
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10. International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEME
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