Wideband Polarization Reconfigurable Differential Circularly Polarized Antenna

This paper presents a polarization reconfigurable differential circularly polarized (PRDCP) antenna with wide impedance and axial ratio (AR) bandwidth for right-hand circular polarization (RHCP) or left-hand circular polarization (LHCP). The antenna is composed of a bandwidth-improved radiator and a reconfigurable differential-to-single-ended sequential feeding network. The radiator consists of three patches, and four feeding lines to achieve the wide AR bandwidth and stable radiation patterns. The feeding network consists of two stepped coupled line couplers (SCLCs), and two switches that provide switchable quadrature excitations. By digitally controlling the inputs of the switches, the LHCP or RHCP mode can be selected. To verify the feasibility of the PRDCP antenna, a prototype is designed, fabricated, and measured. The measured results show that the bandwidths in the LHCP (RHCP) are 75.6% (81.8%) of a 10-dB matching, 66.7% (71.2%) of a 3-dB AR with stable radiation patterns of 7.4 dBi (7.4 dBi) peak gain.