Compact broadband circularly polarized microstrip antenna over artificial ground structure

Abstract

A compact broadband circularly polarized (CP) antenna over the artificial ground structure (AGS) is investigated. The CP radiation patch is comprised of a truncated corner square patch loaded by an extended strip. The AGS which is comprised of a 4 × 4 slot-loaded square metal patches changes the reflection phase in accordance with the polarization state of the incident wave. Broad bandwidth including impedance bandwidth, 3-dB axial ratio (AR) bandwidth, and gain bandwidth is achieved by properly combining the transmitted wave from the patch antenna and the reflected wave from the AGS. The measured results show that the AR bandwidth of the antenna is 14.0% (2.84–3.26 GHz), while the impedance bandwidth is 41.3% (2.48–3.72 GHz). The antenna gain at boresight is 5.35 dBic at 2.9 GHz. The gain fluctuation is less than 1 dB in the whole operating bandwidth. The overall antenna volume is 0.40 × 0.40 × 0.048λ0 at 3 GHz.