In this paper, impedance bandwidth of a Substrate Integrated Waveguide (SIW) cavity backed slot antenna is improved using two symmetric circular perturbations at the two corners of an square cavity. By separating the resonant frequencies of the two degenerate modes including TE120 and TE210, impedance bandwidth is significantly improved. The proposed antenna is numerically investigated using High Frequency Simulator Structure (HFSS). A prototype of the antenna is also made using single layer of substrate. A part from a shift between simulation and measurement results of S11 due to fabrication imperfection, there is a good agreement between other radiation characteristics of the antenna. The measured impedance bandwidth of the proposed antenna is 5.7% at the center frequency of 14 GHz. According to the simulated and measured results, the proposed antenna provides desirable radiation performance such as high gain and high radiation efficiency compared to that of the conventional cavity backed slot antenna without perturbation. Moreover, the proposed antenna possesses the advantages of low profile, lightweight and easy integration with planar circuits.

Keywords