Single-layer wideband probe-fed circularly polarized microstrip antenna

This paper presents a very wideband circular polarization (CP) design of a single-layer probe-fed circular microstrip antenna. Two gap-coupled probe feeds having a concentric annular slot in the radiating patch to tune out the probe inductance are used. The two feeds are placed in orthogonal directions, and are connected to a Wilkinson power divider having a 90° phase shift between its two outputs. The present CP design with a thick air substrate has been implemented, and results show that a 65% impedance bandwidth (VSWR≤2) and a 46% 3 dB axial-ratio CP bandwidth can be achieved. Within the CP bandwidth, the gain bandwidth, defined to be within 3 dB of the peak antenna gain obtained (about 6 dBi), is as large as 44.6%.