Switchable Dual-Band Dual-Sense Circularly Polarized Patch Antenna Implemented by Dual-Band Phase Shifter of ±90°

A switchable dual-band dual-sense (DBDS) circularly polarized (CP) patch antenna is reported in this communication, which is implemented by dual-band phase shifter of ±90°. The proposed antenna is comprised by two annular-ring radiators, four H-shape slots, and two phase-controlled feeding networks. Four H-shape slots offer desired isolation between two paths of each feeding network, and also improve the impedance matching performance in two bands. Each dual-feed network is shared by two operating radiators, supporting simultaneous dual-band functionality. Meanwhile, the dual-band phase shifter is enabled by the folded shorted stubs that provide broadband dual-CP radiation performance. Thus, for each feeding network, −90° and 90° phase differences between two orthogonal signals can be achieved in each band, respectively, so as to meet the requirements of opposite polarizations. Two pairs of single pole single throws (SPSTs) are added in the feeding networks to acquire switchable CP characteristic, meanwhile improving the isolation between two feeding networks. As a proof-of-concept, a switchable DBDS CP antenna prototype operating at 2.45 GHz/5.8 GHz industrial scientific medical (ISM) bands is prototyped and tested with a low profile of $0.036~\lambda _{0}$ . By controlling two pairs of SPSTs, the proposed patch antenna can switch from the right-handed circular polarization (RHCP)/left-handed circular polarization (LHCP) state to the LHCP/RHCP state.