A Frequency-Reconfigurable Cavity-Backed Slot Antenna ESPAR in H Plane

A novel frequency-reconfigurable cavity-backed slot antenna ESPAR in the H plane is presented in this paper. Similar to other ESPAR antennas, the two parasitic cavities lying in the H plane are fed by the center driven cavity through coupling irises and terminated with varactors to provide variable loading impedances. By properly designing the loading impedance, continuous beamscanning in the H plane can be realized. Additionally, a pair of varactors are placed in the center of the slot to achieve a 47.7% frequency tuning range, while preserving the beamscanning performance at each operating frequency. Therefore, the proposed ESPAR is able to provide frequency diversity in addition to spatial diversity inherent in a fixed-frequency ESPAR. It is shown that the proposed ESPAR can steer its beam from -26 to 26 degrees in the H plane. By properly adjusting the frequency tuning varactors, the ESPAR can operate from 4.22 to 6.82 GHz and the impedance matching is maintained for all beamscanning angles.