Active microstrip antenna for circular polarization

A new technique for designing the active microstrip antenna for circular polarization is presented. The circular polarization is achieved by four slits and a pair of truncated corner and the operating frequency is electronically controlled by the bias voltage of varactor diodes. Theoretical modal for an antenna is developed using modal expansion cavity model and circuit theory concept. The results are validated with MoM-based simulator and experimental results. A good agreement between the simulated, calculated, and experimental results is obtained. The tuning range is found to be 40.24% and shows about 71% reduction in antenna size as compare to the conventional circular polarized antenna.