Electrically Small Half-Mode Substrate Integrated Waveguide Circular Cavity Antenna with Improved Gain

Abstract

A novel electrically small half-mode substrate integrated waveguide (HMSIW) circular cavity antenna with improved gain is proposed in this letter. Its low profile, compact size and high gain characteristics are applicable to RF-linked implantable medical devices. A semi-circular patch is extended out of HMSIW cavity antenna to meander the surface current in cavity and decrease the operating frequency of the antenna. Moreover, the extra patch also helps to enlarge the radiating aperture and the gain of the antenna can be improved. To conclude, a slight size increasement of the antenna (extra semicircular patch) can make the antenna electrically smaller with improved gain. The designed antenna possesses a maximum gain of 5.8 dB over the bandwidth of 70 MHz (1%) with 15 dB front-to-back ratio and the cross-polarization level is below −18 dB.