Comparative Investigation of Half-mode SIW Cavity and Microstrip Hybrid Antenna Using Different Patch Shapes

A set of hybrid microstrip patch and semi-circular cavity antennas is introduced. The semi-circular cavity is implemented using Half-mode Substrate Integrated Waveguide (HMSIW) technique. Different shapes of patch include rectangular, semi-circular and equilateral triangular are excited using proximity effect by the circular SIW cavity at its TM010 mode of operation. The whole structures have been excited using an inset microstrip line that leads to facility of planar circuit integration. The inherent limited bandwidth of the conventional microstrip patch antenna and SIW cavity-backed slot antenna is improved about 6% to 9.5% depending on the type of the patch using the proposed structure. Additionally, the proposed hybrid antenna enhances the antenna gain by about 1.5 dB. Meanwhile, the proposed hybrid antennas are made on a single-layer substrate has a low fabrication cost using printed circuit board (PCB) process. Three hybrid antennas are numerically and experimentally investigated. A comparative study between the three different structures contains gain, bandwidth, cross polarization level (CPL) and Front to Back Ratio (FTBR) is presented.