The document describes the design and development of two pentagon and circular ring slot loaded rectangular microstrip monopole antennas (PCRSLRMA and PCCSLRMA) for quad-band and triple-band operation, respectively. The PCRSLRMA operates in four bands between 4-16 GHz while the PCCSLRMA operates in three bands. Both antennas exhibit omnidirectional radiation patterns. The PCRSLRMA achieves a maximum gain of 11.37 dB while the PCCSLRMA achieves 9.98 dB. The addition of the complementary circular ring slot in the PCCSLRMA enhances the bandwidth at each operating band compared to the PCRSLRMA. The proposed antennas have a simple

1. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
INTERNATIONAL JOURNAL OF ELECTRONICS AND
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME
COMMUNICATION ENGINEERING & TECHNOLOGY (IJECET)
ISSN 0976 – 6464(Print)
ISSN 0976 – 6472(Online)
Volume 4, Issue 2, March – April, 2013, pp. 151-157
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PENTAGON AND CIRCULAR RING SLOT LOADED RECTANGULAR
MICROSTRIP MONOPOLE ANTENNAS FOR QUAD-BAND
OPERATION
M. Veereshappa1 and Dr.S.N Mulgi2
1
Department of Electronics, L.V.D.College, Raichur: 584 101, Karnataka, India
2
Department of PG Studies and Research in Applied Electronics, Gulbarga University,
Gulbarga 585 106, Karnataka, India
ABSTRACT
This paper presents the design and development of pentagon and circular ring slot
loaded rectangular microstip monopole antenna for quad band operation. The antenna
operates for four bands of frequencies in the range of 4 to 16 GHz. If complimentary circular
slot is loaded inside pentagon the antenna operates for triple bands of frequencies resulting
the primary resonating mode unaffected with enhanced operating bands. This antenna also
gives the maximum gain of 9.98 dB. In both cases the antenna shows ominidirectional
radiation characteristics. The proposed antennas may find application in microwave
communication systems.
Keywords: microstrip antenna, monopole, pentagon slot, ominidirectional
1. INTRODUCTION
Monopole microstrip antennas are finding increasing application because of their
significant merits like wide band, low interference to other systems, low manufacturing cost,
low profile, light weight, ominidirectional radiation pattern and easy to fabricate. Monopole
microstrip antenna have been designed by using regular shaped configurations, such as
circular, elliptical and triangular etc [3-6]. The design and analysis of octagon shaped hybrid
coupled microstrip antenna for multiband operation [7], octagonal microstrip antenna for
RADAR and spacecraft applications [8], CPW- feed octagon shaped slot antenna for
UWB application [9], bandwidth enhancement of wide slot antenna fed by CPW
and microstripline [10], ultra wideband pentagon shape microstrip slot antenna for wireless
communications[11], wideband pentagon-slot microstrip antenna with semicircle probe feed
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2. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME
[12] etc are found in the literature. But the design and development of pentagon and circular
ring slot loaded antennas for quad band and high gain operation feed by microstripline is
found to be rare in the literature. Further most of the antennas presented in the literature are
either complex in their structure or bigger in size and hence extra care has to be taken to
manufacture than that of the regular microstrip antenna.
2. DESIGN OF ANTENNA GEOMETRY
The art work of the proposed antenna is sketched by using computer software Auto-
CAD to achieve better accuracy and is fabricated on low cost FR4-epoxy substrate material
of thickness of h = 0.16 cm and permittivity εr = 4.4.
Fig: 1 Top view geometry of PCRSLRMA
Figure 1 shows the top view geometry of pentagon and circular ring slot loaded
rectangular microstrip monopole antenna (PCRSLRMA). In this figure the area of the
substrate is L × W cm. On the top surface of the substrate a ground plane of height which is
equal to the length of microstripline feed Lf is used on either sides of the microstripline with a
gap of 0.1 cm. On the bottom of the substrate a continuous ground copper layer of height Lf is
used below the microstripline. The PCRSLRMA is designed for 3 GHz of frequency using
the equations available for the design of conventional rectangular microstrip antenna in the
literature [2]. The length and width of the rectangular patch are Lp and Wp respectively. The
feed arrangement consists of quarter wave transformer of length Lt and width Wt which is
connected as a matching network between the patch and the microstripline feed of length Lf
and width Wf. A semi miniature-A (SMA) connector is used at the tip of the microstripline
feed for feeding the microwave power. In Fig.1 pentagon slot is loaded on the patch with
vertices of X. The tip of the pentagon is touching the midpoint along the width of the patch.
Further a circular ring slot is loaded inside the pentagon slot with a radius R and width W.
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3. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME
Figure 2 shows the geometry of pentagon slot and complimentary circular loaded
rectangular microstrip monopole antenna (PCCSLRMA). The circular slot shown in Fig 1
and 2 are having same radius R but compliment with each other. The other geometry of Fig. 2
remains same as that of Fig.1. The design parameters of the proposed antennas are given in
Table 1
Fig: 2 Top view geometry of PCCSLRMA
Table 1
Designe parameters of proposed antenna
Antenna L W Lp Wp Lf Wf Lt Wt X R W
parameter
Dimensions 8.0 5.0 2.34 3.04 2.48 0.3 1.24 0.05 1.2 0.6 0.2
in cm
3. EXPERIMENTAL RESULTS
The antenna bandwidth over return loss less than -10 dB is tested experimentally on
Vector Network Analyzer (Rohde & Schwarz, Germany make ZVK model 1127.8651). The
variation of return loss verses frequency of PCSRLRMA is as shown in Fig. 4. From this
graph the experimental bandwidth (BW) is calculated using the equations,
f −f 
BW =  2 1  ×100 % (1)
 fc 
were, f1 and f2 are the lower and upper cut of frequencies of the band respectively when its
return loss reaches – 10 dB and fc is the center frequency of the operating band. From this
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4. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME
figure, it is found that, the antenna operates between 2 to 16 GHz and gives four resonant
modes at f1 to f4, i.e. at 4.8, 7.3, 8.69, and 15.53 GHz. The magnitude of experimental -10 dB
bandwidth measured for BW1 to BW4 by using the equation (1) is found to be 50 MHz (1.04
%), 430 MHz (5.91 %), 2.11 GHz (23.58 %), and 5.46 GHz (41.14 %) respectively.
Fig: 3 Variation of return loss versus frequency of PCRSLRMA
The resonant mode at 4.78 GHz is due to the fundamental resonant frequency of the
patch and others modes are due to the novel geometry of PCRSLRMA. The multi mode
response obtained is due to different surface currents on the patch. The fundamental resonant
frequency mode shifts from 3 GHz designed frequency to 4.8 GHz due to the coupling effect
of microstripline feed and top ground plane of PCRSLRMA.
Figure 4 shows the variation of return loss verses frequency of PCCSLRMA. It is
seen that, the antenna operates for three bands of frequencies BW5 to BW7. The magnitude of
these operating bands measured at BW5 to BW7 is found to be 90 MHz (1.88 %), 2.82 GHz
(32.83 %), and 5.54 GHz (41.87 %) respectively. The operating bands BW2 and BW3 are
shown in Fig.3 are merged into single band BW7 in this case as shown in Fig.4. Further from
Fig.4 it is clear that, the each operating bands of PCCSLRMA is enhanced when compared to
the operating bands of PCRSLRMA. However in both the cases the fundamental resonant
modes i.e. f1 in Fig.3 and f5 in Fig.4 are unaffected.
Fig. 4 Variation of return loss versus frequency of PCCSLRMA
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5. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME
The gain of the proposed antennas is measured by absolute gain method. The power
transmitted ‘Pt’ by pyramidal horn antenna and power received ‘Pr’ by antenna under test
(AUT) are measured independently. With the help of these experimental data, the gain (G)
dB of AUT is calculated by using the formula,
P   λ 
(G) dB=10 log  r  - (G t ) dB - 20log  0  dB (2)
 Pt   4πR 
where, Gt is the gain of the pyramidal horn antenna and R is the distance between the
transmitting antenna and the AUT. Using equation (2), the maximum gain of the
PCRSLRMA and PCCSLRMA measured in their operating bands is found to be 11.37 dB
and 9.98 dB respectively.
The co-polar and cross-polar radiation pattern of PCRSLRMA and PCCSLRMA is
measured in their operating bands. The typical radiation patterns measured at 4.78 GHz in
both cases are shown in Fig 5 to 6 respectively. The obtained patterns are ominidirectional in
nature. Further by comparing Fig.5 and 6 it is clear that the PCCSLRMA gives even better
ominidirectional radiation characteristics than that of PCRSLRMA.
Fig. 5 Typical radiation pattern of PCRSLRMA measured at 4.78 GHz
Fig. 6 Typical radiation pattern PCCSLRMA measured at 4.78 GHz
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6. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME
4. CONCLUSION
From the detailed experimental study, it is concluded that, the novel geometry of
PCRSLRMA is capable in producing quad band operation and ominidirectional radiation
characteristics. The antenna operates for four bands of frequencies in the frequency range of
4 to 16 GHz. If complimentary circular slot is loaded inside the pentagon i.e. PCCSLRMA
the antenna operates for triple bands and enhances the bandwidth at each operating band
compared to the operating bands of PCRSLRMA and gives improved radiation
characteristics. The proposed antennas are simple in their design and fabrication and they use
low cost substrate material. These antennas may find application in microwave
communication systems.
ACKNOWLEDGEMENTS
The authors would like to thank Dept. of Sc. & Tech. (DST), Govt. of India. New
Delhi, for sanctioning Vector Network Analyzer to this Department under FIST project. The
authors also would like to thank the authorities of Aeronautical Development Establishment
(ADE), DRDO Bangalore for providing their laboratory facility to make antenna
measurements on Vector Network Analyzer.
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