Broadband circularly polarized square microstrip antenna

The design of a broadband square microstrip antenna with circular polarization radiation is presented in this paper. The antenna comprises a thick air substrate and single square microstrip radiating patch, which is excited by dual capacitive-coupled feed disks connected to a Wilkinson power divider having equal amplitude and a 90deg phase shift between its two outputs. The experimental results show that the proposed antenna is able to achieve an impedance bandwidth of 69% for VSWR less than 2 and a 3 dB axial-ratio bandwidth about 23%.