Bandwidth enhancement of substrate integrated waveguide cavity-backed slot antenna

This paper proposes a technique for bandwidth enhancement of substrate integrated waveguide (SIW) cavity-backed slot antenna. The enhancement of bandwidth is carried out by putting a square metallic plate in the middle of substrate. Since a thin layer of dielectric substrate increases quality factor (Q factor) of the antenna which affects of narrowing bandwidth response, hence the proposed antenna implements multiple layers of FR4 epoxy dielectric substrate in overcoming the problem. The SIW cavity-backed slot antenna is simply excited by a coaxial type of probe extended into square metallic plate which is located at center of the cavity. Some parametric studies are offered for better understanding of the proposed antenna characteristics such as number of slot, angle of tilted slot, separation between slots, and position of square metallic plate. It is found that the use of square metallic plate could produce the second resonant frequency affecting to the bandwidth enhancement. The characterization result shows that the -10dB working bandwidth is about 175MHz in the frequency range of 1.9GHz to 2.075GHz with the fractional bandwidth of 9.2%.

I. Introduction

Recently, In high frequency applications, waveguide-based antenna devices are preferred as they have good direction of radiation, low cross-polarization level, and low side-lobe level [1]–[2]. However, manufacturing process of waveguide-based antenna devices are difficult and rather expensive compared to others [2]–[3]. Furthermore the geometrical size also becomes bulky and non-planar in nature [4]–[5]. Therefore, substrate integrated waveguide (SIW) emerges as an alternative option to conventional metallic waveguide [6]. Basically, SIW is a transition between microstrip line and dielectric filled waveguide [7]–[8]. Here, the dielectric-filled waveguide is converted into SIW by the help of via arrays which act as the side walls of waveguide.