Bandwidth enhancement of circularly polarized square slot antenna

Abstract

Bandwidth enhancement technique of circularly polarized square slot antenna is presented in this paper. A square slot antenna with the components of L-probe separated could achieve an axial ratio (AR) bandwidth of 33.84%. Placing Stubs in the slot by studying the electric field behaviour could enhance the AR bandwidth by around 10%. Creating an L-shaped slot on the ground plane, where the electric field rotates in the desired clockwise direction, can further enhance the bandwidth by 7%. A < -10 dB S11 bandwidth of 46.15% and < 3 dB AR bandwidth of 50.35% could be achieved with the present design. Unidirectional patters are obtained by having a cavity at the wide slot of the antenna and shows a measured bandwidth of 41.79% in S11 and 44.97% in AR. Both antennas show a cross polarization discrimination of more than 15 dB on a wide azimuth range. The measured results well comply with the simulated results.