Rectangular slot loaded monopole microstrip antennas for triple band operation

International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN

0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 1, January- February (2013), © IAEME

176

RECTANGULAR SLOT LOADED MONOPOLE MICROSTRIP

ANTENNAS FOR TRIPLE-BAND OPERATION AND VIRTUAL SIZE

REDUCTION

M. Veereshappa

1, 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.

[email protected], [email protected]

ABSTRACT

This paper presents the design and development of rectangular slot loaded monopole

microstrip antennas for triple-band operation and virtual size reduction. The antenna operates

for three band of frequencies in the frequency range of 1 to 16 GHz and gives maximum

virtual size reduction of 62 %. If vertical rectangular slot on the patch is rotated by an angle

of 300 the antenna retains three bands of frequencies and gives the maximum band width at

each operating band keeping same virtual size reduction .The three bands may be converted

to six bands by further rotating 300 slot on the patch to 60

0. In all the cases antenna gives

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.

1. INTRODUCTION

Microstrip antennas are useful in microwave communication systems because of their

diversified applications such as compact in size, simple in design, planar configurations,

compatibility with integrated circuits, low cost, low profile, light weight, and easy to

fabricate[1-2]. Number of investigations have been reported in the literature for the

realization of dual, triple and multi-band operation [3-6] and enhancement of impedance

bandwidth [7-8]. Designs of single feed equilateral triangular microstrip antennas are

obtained with an virtual size reduction is up to 22 % by embedding cross slots on radiating

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ISSN 0976 – 6464(Print)

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177

patch [9]. Most of the antennas presented in the literature are complex in their design and

large in antenna size. In this paper a simple technique has been demonstrated to construct the

monopole antenna for triple band operation, virtual size reduction and enhancement of

impedance bandwidth at each operating band by varying the angle of vertical slot on the

patch without affecting the nature of radiation characteristics.

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 rectangular slot monopole microstrip antenna

(RSMA). 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 RSMA 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 the

rectangular slot is placed along the center axis of the patch at a distance of 1.42 cm from the

vertical sides of the patch. The length and width of rectangular slot is Ls and Ws respectively,

and are to be in terms of operating wave length.

Figure 1 Top view geometry of RSMA



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Figure 2 shows the geometry of inclined thirty degree rectangular slot monopole microstrip

antenna (ITRSMA). In this figure a rectangular slot is rotated by an angle of 300 on the patch

when compared to Fig.1 The feed arrangement of Fig. 2 remains same as that of Fig.1.

Figure 2 Top view geometry of ITRSMA

Figure 3 Top view geometry of IRSSMA

Fig.3 shows the geometry of inclined sixty degree rectangular slot monopole microstrip

antenna (IRSSMA). In this figure rectangular slot is rotated on the patch by an angle of 600

with respect to Fig.1. The feed arrangement of this antenna is also remain same as that of

Fig.1. The design parameters of the proposed antennas is as shown in Table 1



179

TABLE 1 Design Parameters of Proposed Antennas Antenna Dimension

Parameters (cm)

Antenna Dimension

Parameters (cm)

Lp 2.34

Wp 3.04

Lf 2.48

Wf 0.30

Lt 1.24

Wt 0.05

L 8.0

W 5.0

Ls 1.666

Ws 0.2

h 0.16

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 RSMA is as shown in Fig. 4. From this graph the experimental bandwidth (BW)

is calculated by using the equations,

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 three resonant modes at

f1 to f3, i.e. at 1.14, 4.70, and 14.01 GHz. The magnitude of experimental -10 dB bandwidth

measured for BW1 to BW3 by using the equation (1) is found to be 130 MHz (9.6 %), 80

MHz (1.68 %), and 8.81 GHz (76.24 %) respectively.

Figure 4 Variations of return loss versus frequency of RSMA



180

The resonant mode at 1.14 GHz is due to the fundamental resonant frequency of the patch and

others modes are due to the novel geometry of RSMA. The triple band response obtained is due

to different surface currents on the patch. The fundamental resonant frequency mode shifts from 3

GHz designed frequency to 1.14 GHz due to the coupling effect of microstripline feed and top

ground plane of RSMA. This shift of frequency gives a virtual size reduction of 62 %.

Figure 5 Variations of return loss versus frequency of ITRSMA

Figure 5 shows the variation of return loss verses frequency of ITRSMA. It is seen that, the

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

measured at BW4 to BW6 is found to be 340 MHz (27 %), 190 MHz (4.02 %), and 8.88 GHz

(76.81 %) respectively. Hence by comparing Fig.4 and 5 it is clear that the each operating band of

Fig.5 is enhanced by changing vertical slot on the patch by 300 when compared to Fig.1.

The variation of return loss verses frequency of IRSSMA is as shown in Fig. 6. From this figure it

is clear that, the antenna operates for six bands BW7 and BW12. The magnitude of each operating

band is found to be 220 MHz (18.33 %), 90 MHz (1.9 %), 2.76 GHz (32.74 %), 2.26 GHz (19.96

%), 790 MHz (6.04 %) and 2.42 GHz (16.36%) respectively. This shows that, the rotation of slot

on the patch is effective in increasing the number of operating bands. The simulated results of

RSMA, ITRSMA and IRSSMA are also shown in Fig. 4 to 6. The experimental and simulated

results are in good agreement with each other.

Figure 6 Variations of return loss versus frequency of IRSSMA



181

The co-polar and cross-polar radiation pattern of RSMA, ITRSMA and IRSSMA is

measured in their operating bands. The typical radiation patterns for the proposed antennas

are shown in Fig 7 to 9 respectively. The obtained patterns are ominidirectional in nature.

The gain of RSMA, ITRSMA and IRSSMA is measured by absolute gain method. The

maximum gain found to be 8.18, 9.93 and 8.38 dB respectively.

Figure7 Typical radiation pattern of RSMA Figure 8 Typical radiation pattern of TRSMA

.

Figure 9 Typical radiation pattern of IRSSMA



182

4. CONCLUSION

From the detailed experimental study, it is concluded that the RSMA operates for

three band of frequencies in the frequency range of 1 to 16 GHz and gives maximum virtual

size reduction of 62 %. If rectangular slot is rotated with an angle of 300 the enhancement of

each operating band in triple band operation is possible .The three band of frequencies may

be converted into six bands by further rotating rectangular slot on the patch by an angle of

600. In all cases the antenna gives virtual size reduction of 62 % with ominidirectional

radiation characteristics. Experimental results are in close agreement with the simulated

results. The proposed antenna may find application for 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.

REFERENCES

1 Constantine A. Balanis, Antenna theory: analysis and design, John Wiley, New

York, 1997.

2 I. J. Bahl and P. Bharatia, Microstrip antennas, Dedham, MA: Artech House, New

Delhi, 1981.

3 Waterhouse, R.B, and Shuley, N.V: “Dual frequency microstip rectangular patches”,

Electron lett, 28(7), 1992, pp. 606-607.

4 W. –C. Liu and H.-J. Liu, “Compact triple-band slotted monopole antenna with

asymmetrical CPW grounds” Electron lett, 42(15), 2006, pp.840-842.

5 K. G. Thomas and M. Sreenivasan, ”Compact triple band antenna for WLAN,

WiMAX applications,” Electron lett. Vol. 45(16), 2009, pp.811-813.

6 C. W. Jung, I. Kim, Y. Kim and Y. E. Kim. “Multiband and multifeed antenna for

concurrent operation mode”. Electron lett, 43(11), 2007, pp.600-602.

7 K. Song, Y. Z. Yin, S. T Fan, Y. Z Wang and L. Zhang, Open L-slot antenna with

rotated rectangular patch for bandwidth enhancement, Electron Lett 45 (2009),

1286 – 1288.

8 Jia- Yi Size, Kin-lu Wong, Slotted rectangular microstip antenna for bandwidth

enhancement, IEEE Trans Antennas Propagat 48 (2000), 1149-1152.

9 Gui-Han Lu; Kin-Lu Wong, “Single-feed circularly polarized equilateral- triangular

microstip antenna with a tuning stub” IEEE Trans on Antennas and Propagat

48(12), 2000, pp.1869-1872.

10 M. Veereshappa and Dr.S.N Mulgi, “Design And Development Of Triple Band

Ominidirectional Slotted Rectangular Microstrip Antenna” International journal of

Electronics and Communication Engineering &Technology (IJECET), Volume 3,

Issue 1, 2012, pp. 17 - 22, Published by IAEME

Rectangular slot loaded monopole microstrip antennas for triple band operation

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