Vertical Slot Loaded Rectangular Monopole Microstrip Antenna for Triple Band Operation

Abstract

This paper presents the design and development of simple vertical slot loaded rectangular monopole microstrip antenna for triple band operation. The proposed antenna is excited through microstripline feed arrangement. The low cost glass epoxy substrate material is used to fabricate the antenna. The antenna operates between 2.77 to 8.29 GHz. giving linearly polarized broadside radiation characteristics with a peak gain of 3.8dB. The proposed antenna may find applications in WLAN.

Introduction

I. INTRODUCTION

In recent years the microstrip antennas are becoming increasingly popular because of their small size, lightweight, low cost, easy to fabricate and compatible to microwave integrated circuits [1-2]. However, the modern communication systems such as wireless local area networks (WLAN) often require antennas possessing two or more discrete frequency bands, which can avoid the use of multiple antennas. The single, dual and triple band microstrip antennas are designed by cutting slots of different geometries like bow-tie, rectangular, square ring, annular ring etc. on the radiating patch [3-12].In this paper a vertical slot loaded rectangular monopole microstrip antenna is presented for triple band operation giving better radiation characteristics. This kind of study is found to be rare in the literature.

II.  DESIGNING OF ANTENNA

The conventional rectangular microstrip antenna (CRMSA) is fabricated on low cost glass epoxy substrate material of thickness h = 1.6 mm, loss tangent 0.02 and dielectric constant er = 4.2. The artwork of is developed using computer software AUTO CAD to achieve better accuracy. The antennas are etched by photolithography process. The bottom surface of the substrate consists of a tight ground plane copper shielding.

Figure 1 shows the geometry of CRMSA This antenna is designed for the resonant frequency of 3.0 GHz using the equations available in the literature for the design of rectangular microstrip antenna on the substrate area A-SUBSTRATE x B-SUBSTRATE [13]. This antenna consists of a radiating patch of length L and width W. A quarter wave transformer of length Lt and width Wt is incorporated to match the impedances between Patch and microstripline feed of length Lf and width Wf. A 50 Ω semi miniature-A (SMA) connector is used at the tip of the microstripline to feed the microwave power.

Figure 2 shows the geometry of vertical slot loaded rectangular monopole microstrip antenna (VSRMMSA) which has all the dimensions same as present in CRMSA.

 A vertical slot of width 2 mm and length SV= 1.8 cm is placed on the patch to achieve triple band operation. The designed parameters are tabulated in Table No 1.

Table No 1

Figure 3 shows the variation of return loss versus frequency of CRMSA.  It is clear from this figure that, the antenna resonates at 2.8 GHz which is very close to the designed frequency of 3 GHz. The CRMSA exhibits the band width of 2.15% which is determined by the relation

Where FH  and FL are the higher and lower cut off frequencies of return loss curve when it is below -10dB value.  The proposed antennas are simulated by HFSS 15.0 version software

Figure 4 shows the variation of return loss versus frequency of VSRMMSA when the slot is on left side of the central line of the patch. It is seen from this figure that the antenna resonates for triple bands f1, f2 and f3 with respective bandwidths BW1=2.52% (2.81-2.74GHz), BW2=4.72%(7.37-7.03 GHz) and BW3=1.46% (7.56-7.45 GHz). The BW1 is due to fundamental resonance of the patch while BW2 and BW3 are due to the insertion of the slot on the radiating patch.

Figure 5 shows the variation of return loss versus frequency of VSRMMSA when the slot position on the right side about the central line. It is seen from this figure that, the antenna operates for three bands f4, f5 and f6  with respective band widths BW4 = 1.08 % (2.77-2.74 GHz), BW5= 2.53(7.20-7.02 GHz) and BW6 = 1.58(8.29-8.16 GHz).

Figure 6 shows the variation of return loss against the frequency of the VSRMMSA when two slots are places symmetrical about the central line on the patch, It is observed that the antenna resonates for a single band f7 with the bandwidth BW7=14.23(5.95-5.16GHz). The bands BW4 to BW6 all merge in to a single band giving a bandwidth of 14.23%.

Figure 7 and 8 show the radiation pattern of CRMSA and VSRMMSA. It is seen from these figures that the patterns are linear and broad sided. 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 equation,

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 CRMSA and VSRMMSA measured in their operating bands are found to be 1.01 dB and 3.8 dB respectively.

Conclusion

From the detailed study, it is concluded that, the CRMSA can be made to operate at three frequency bands between 2.77 to 8.29 GHz by loading vertical slot on the radiating patch. The maximum bandwidth of 14.23 % is achieved with linear broad side radiation pattern. The peak gain of 3.8 dB is achieved by the VSRMMSA. The proposed antennas are simple in their geometry and are fabricated using low cost glass epoxy substrate material. These antennas may find applications in wireless local area network(WLAN).

References

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Copyright

Copyright © 2022 Srinivas Ramacharya, Nagraj Kulkarni, P.V. Hunagund. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.