Broadband Polarization Switchable Circularly Polarized Antenna with Stepped Radiating Loop

In this paper, a broadband polarized switchable circularly polarized (PSCP) antenna is proposed. The antenna is comprised of a radiator, a switchable feeding network, and four metal feed posts. A stepped radiating loop and a circular patch are applied to form the radiator to improve the bandwidth of the PSCP antenna. Two switches, a short-circuit coupled-line, an open-circuit coupled-line and two coupled-line couplers form a broadband switchable feeding network. The feeding network outputs four signals of sequential ±90° phase, which are transmitted to the radiator through four copper posts. The SRL-based PSCP antenna can achieve the conversion of LHCP or RHCP radiation characteristics by changing the operating modes of the coupled-line-based feeding network. To validate the feasibility of the PSCP antenna, the manufactured object is tested. Measurement results demonstrate that the LHCP (RHCP) mode exhibits a -10 dB impedance bandwidth of 96.6% (98.7%), a 3 dB axial ratio bandwidth of 76.8% (69.4%), and a peak gain of 9.1 dBi (9.2 dBi) with a stable radiation pattern.