Study of Compact 2×1 Microstrip Antenna Array Loaded with EBG Structure

Author Name(s): K. Prahlada Rao *, P.V. Hunugund, Vani R.M
Author Email: pra_kaluri@rediffmail.com

Abstract

In this paper the design of two element microstrip antenna array (TEMAA) without and with Electromagnetic Band Gap (EBG) structure integrated in the ground plane and on the surface is demonstrated. The TEMAA designed at a frequency of 6 GHz is resonating at a frequency of 5.53 GHz with a return loss of -21.23 dB. With the introduction of EBG, the mutual coupling of TEMAA is reduced from -17.83 dB to -49.89 dB respectively. The front to back ratio of the modified antenna array is enhanced to 7.08 dB. The antenna arrays have been designed using Mentor Graphics IE3D simulation software and the measured results have been obtained using vector network analyzer.  The antenna arrays designed operate in the frequency range of 1-7 GHz.

Introduction

An antenna is defined as an electrical device that transmits and receives electromagnetic waves. An antenna is an integral part of every person’s life and can be used for a variety of applications. It is a key component of most of the communication systems. The radiation properties of an antenna can be varied by changing the dimensions of the geometry of the antenna or by incorporating new structures in the antenna or by making necessary changes in the antenna structure. Some of the radiation properties of an antenna are directivity, gain, half power beam width, beam width between first nulls, radiation resistance etc. Proper design of an antenna is very much desired in attaining the objectives of the researcher. [1-4]

In the year 1953, scientist Deschamps invented a new class of antennas called microstrip antennas. With the recent advancements in technology towards designing low profile antennas, these antennas have received huge appreciation from researchers in fulfilling their aims and objectives due to the numerous advantages. Over the past few decades these antennas have proved to be excellent radiators in various fields of applications. In its simplest form a microstrip antenna consists of a dielectric substrate embedded between the radiating patch and ground plane. The radiating patch is available in a variety of shapes like square, rectangular, circular etc.  [5-7]

Microstrip antenna arrays suffer from the serious drawback of very high mutual coupling between the individual antenna elements. The problem of mutual coupling arises due to the excitation of surface waves in the dielectric substrate of the antenna array. This demerit can be overcome by increasing the distance between the antenna elements. However, this increases the area occupied by the microstrip antenna array. Mutual coupling can also be decreased by decreasing the substrate thickness, employing EBG structures, metamaterials etc. Many researchers have obtained appreciable improvement in the performance of microstrip antenna arrays by employing EBG structures. These structures are periodic in nature which assist or stop the propagation of electromagnetic band gap structures in a particular band of frequencies for any incident angle or polarization state.EBG structures have attracted many researchers because of their unique properties. [8-14]

Conclusion

This paper demonstrates the effectiveness of employing Electromagnetic Band Gap structures in improving the performance of a two element microstrip antenna array. Thus these structures have proved to be very useful tools in reducing the mutual coupling as well as in the miniaturization of the antenna array. The antenna arrays have been successfully designed and fabricated. A virtual size reduction of 47.73 % has been achieved. The antenna array with EBG structures is exhibiting good radiation characteristics. This shows that the performance of two element antenna array is improved by loading the EBG’s in the ground plane and on the surface.

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