A Wideband Circularly Polarized Antenna with Characteristic Mode Analysis

Abstract

A wideband circularly polarized (CP) antenna is presented to achieve enhanced impedance, axial ratio (AR), and gain bandwidths. The antenna consists of two circular patches, a split-ring microstrip line with six probes, and a circular ground plane. By using these six probes which are placed in sequence on the split-ring microstrip line, the operating bandwidth of the proposed antenna is increased. The characteristic mode method is used to analyze different modes of the antenna and reveal the mechanism of extending the 3-dB AR bandwidth. Measured results show that the proposed antenna obtains an impedance bandwidth of 1.486–2.236 GHz (40.3%) for S11 ≤ −18 dB, a 3-dB AR bandwidth of 1.6–2.2 GHz (31.6%), and a boresight gain of 8.89 ± 0.87 dBic.