COMPARISON OF HIGH IMPEDANCE TEXTURED SUBSTRATES FOR SUPPRESSION OF SURFACE WAVES IN MICROSTRIP ANTENNAS WITH SOLID AND HOLLOW METALLIC PINS

High Impedance Textured Substrate is presented for suppression of Surface Waves in Microstrip Antennas. Surface wave propagation limits the radiation efficiency, bandwidth, gain, alters the main beam radiation pattern, and increases side lobe levels as well as the back lobes. A novel technique to suppress the surface waves with periodic arrangement of metallic cylindrical pins embedded in the substrate except the area underneath the radiating microstrip patch is presented here. Two structures with solid as well as hollow cylindrical pins are analysed with Spectral Domain Analysis. The textured pin bed structure creates negative permittivity and high capacitive impedance and thus suppresses the propagation of TM-surface waves. The gain of 11.83 dB with an enhancement of 6 dB over normal microstrip patch antenna is achieved. Further an increase of 1.61 dB gain with 12.27% improvement in radiation bandwidth is observed in the antenna structure with hollow cylindrical pins as compared to that of solid cylindrical pins. A uniform gain of more than 11 dB is achieved with a percentage bandwidth of 17.43%.