Corner truncated rectangular slot loaded monopole microstrip antennas for

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

165

CORNER TRUNCATED RECTANGULAR SLOT LOADED

MONOPOLE MICROSTRIP ANTENNAS FOR QUAD-BAND

OPERATION

M. Veereshappa1, and S. N. Mulgi

2

1Department

0f Electronics, L.V.D.College, Raichur -584 103, Karnataka, India

2Department of PG Studies and Research in Applied Electronics, Gulbarga University,

Gulbarga – 585 106, Karnataka, India.

ABSTRACT

This paper presents the design and development of corner truncated slot loaded

rectangular monopole microstrip antennas for quad-band operation. The antenna operates in

the frequency range of 4 to 16 GHz and gives maximum gain of 9.90 dB in its operating

band. If the vertical rectangular slots on the patch are placed with a gap of 0.2 cm from non

radiating edges of the patch the antenna operates for three bands of frequencies with a notch

band from 2.45 to 10.13 GHz and gives the maximum virtual size reduction of 57.66 % and

gain of 16 dB. In both the cases the antenna shows ominidirectional radiation characteristics.

Experimental results are in close agreement with the simulated results. The proposed antenna

may find application for microwave communication systems.

Key words: monopole, virtual size, ominidirectional, notch-band

1. INTRODUCTION

The rapid developments in microwave communication systems often demand novel

design of microstrip antennas with compact size, simple in design, low cost and capable of

operating more than one band of frequencies. Owing to its thin profile, light weight, low cost,

planar configuration and easy fabrication, the microstrip antenna is the better choice for these

requirements. Number of investigations have been reported in the literature for dual, triple,

and multiband operation [3-8]. Designs of single feed equilateral triangular microstrip

antennas are obtained with a virtual size reduction up to about 22 % by embedding cross slots

on radiating patch [9], a square-ring microstrip antenna with truncated corners shows 19 %

virtual size reduction [10], double C-slot microstrip antenna is designed and simulated to

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have a gain of 6.46 dBi and gives a virtual size reduction of 37 % [11], slotted rectangular

microstrip antenna has been designed to achieve maximum virtual size reduction around 50 %

[12], monopole antennas are designed to improve the notch band operation [13-14], etc. Further

most of the antennas presented in the literature are either complex structure or bigger in size and

also require careful manufacturing procedure than that of the regular microstrip antenna for

practical applications. In this paper a simple method has been demonstrated for the design and

development of corner truncated monopole antenna for quad-band and triple band operation with

virtual size reduction and notch band operation all together is found to be rare in the literature.

2. DESIGN OF ANTENNA GEOMETRY

The art work of the proposed antennas is sketched by using computer software Auto-

CAD to achieve better accuracy and are fabricated on low cost FR4-epoxy substrate material of

thickness of h = 0.16 cm and permittivity εr = 4.4.

Figure 1 shows the top view geometry of corner truncated slots loaded rectangular

monopole microstrip antenna (CTSLRMA-I). The selected area of the substrate is A = 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 antenna 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 four corners of the patch is truncated with the vertical and horizontal lengths of X and Y

respectively. Further rectangular slots are loaded on the patch at a distance d = 0.6 cm from the

vertical sides of the patch. The length and width of rectangular slots are Ls and Ws respectively

Figure 1 Top view geometry of CTSLRMA-I



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Figure 2 shows the geometry CTSLRMA-II. In this figure only positions of rectangular slots

are changed. The slots are placed at a distance of 0.2 cm from vertical sides of the patch. The

feed arrangement of Fig. 2 remains same as that of Fig.1. The design parameters of the

proposed antennas is as shown in Table 1

Figure 2 Top view geometry of CTSLRMA-II

TABLE 1 Design parameters of proposed antennas

Antenna

Parameters

Dimension in cm

Antenna

Parameters

Dimension in cm

L 8.0 Lt 1.24

W 5.0 Wt 0.05

Lp 2.34 Ls 1.54

Wp 3.04 Ws 0.41

Lf 2.48 X 0.4

Wf 0.30 Y 0.2

3. EXPERIMENTAL RESULTS

The antenna bandwidth over return loss less than -10 dB is simulated using HFSS

simulating software and then tested experimentally on Vector Network Analyzer (Rohde &

Schwarz, Germany make ZVK model 1127.8651). The variation of return loss verses

frequency of CTSLRMA-I is as shown in Fig. 3. From this graph the experimental bandwidth

(BW) is calculated by using the equations,



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BW 2 1

c

= ×100 % (1)f f

f

−

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 between f1 and f2. From this figure,

it is found that, the antenna operates between 1 to 16 GHz and gives four resonant modes at f1

to f4, i.e. at 4.74, 7.71, 8.89, and 15.41 GHz respectively. The magnitude of experimental -10

dB bandwidth measured for BW1 to BW4 by using the equation (1) is found to be 50 MHz

(1.05 %), 650 MHz (8.53 %), 1.44 GHz (15.78 %) and 5.45 GHz (41.14 %) respectively.

Figure 3 Variations of return loss versus frequency of CTSLRMA-I

The resonant mode at 4.74 GHz is due to the fundamental resonant frequency of the

patch which is shifted from designed frequency 3 GHz to 4.7 GHz. The shift in the mode f1 of

fundamental frequency and other multimode’s are due to the novel geometry of CTSLRMA-

I. The quad band response of antenna is due to existence of different surface currents on the

patch. The proposed antenna gives maximum gain of 9.90 dB measured at 4.74 GHz.

Figure 4 Variations of return loss versus frequency of CTSLRMA-II



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Figure 4 shows the variation of return loss verses frequency of CTSLRMA-II. It is seen

that, the antenna operates for three bands of frequencies. The magnitude of these operating bands

measured at BW5 to BW7 is found to be 100 MHz (8.77 %), 200 MHz (8.51 %), and 5.82 GHz

(38.65 %) respectively. Hence by comparing Fig.4 and 5 it is clear that, the each operating band

of Fig.5 is enhanced by shifting the position of vertical slot on the patch with a gap of 0.2 cm

instead of 0.6 cm from its vertical sides of the patch. In this case the fundamental resonant

frequency of CTSLRMA-II shifts from 4.74 GHz to 1.27 GHz. This shift of frequency gives a

maximum virtual size reduction of 57.66 % and also gives maximum gain of 16 dB measured at

2.34 GHz. Further it is clear from Fig. 4 that, a notch band appears from 2.45 GHz to 10.13 GHz

between the bands BW6 and BW7.

Hence it is clear that, the change of position of rectangular slots in CTSLRMA-II is quite

efficient the widening the operating bands, enhances the virtual size reduction and exhibits the

notch-band operation.

The co-polar and cross-polar radiation pattern of CTSLRMA-I and CTSLRMA-II is

measured in their operating bands. The typical radiation patterns measured at 4.74 GHz and 2.34

GHz are shown in Fig 5 and 6 respectively. The obtained patterns are ominidirectional in nature.

Figure5 Typical radiation pattern of CTSLRMA-I measured at 4.74 GHz\

Figure 6 Typical radiation pattern of CTSLRMA-II measured at 2.34 GHz



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4. CONCLUSION

From the detailed experimental study, it is concluded that, the CTSLRMA-I feed by

microstripline is capable to producing quad-band operation. The antenna operates for four

bands of frequencies in the frequency range of 1 to 16 GHz and gives maximum gain of

9.90 dB. If the vertical rectangular slots on the patch are placed with a gap of 0.2 cm from the

non-radiating edges of the patch the antenna operates for three bands of frequencies and

gives notch band from 2.45 to 10.13 GHz and shows the maximum virtual size reduction of

57.66 % and enhances the gain to 16 dB. In both the cases antenna gives ominidirectional

radiation characteristics. The proposed antennas may find application in microwave

communication systems.

ACKNOWLEDGEMENT

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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Issue 1, 2013, pp. 176 - 182, ISSN Print: 0976- 6464, ISSN Online: 0976 –6472.

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