Back-to-Back Microstrip Antenna Fed With Tunable Power Divider

A design for microstrip antennas with reconfigurable radiation pattern is described. Dual stacked patch antennas and one tunable power divider are involved in the reconfigurable design. The two antennas are arranged by a back-to-back configuration, and they are, respectively, excited by the outputs of the power divider composed of a quasi-lumped coupler and two varactor diodes. By controlling the dc voltage of the varactors, the ratio of two outputs of the power divider can be varied between 0 and 13 dB so that the radiation patterns generated by the two antennas are changed. A prototype operating at 2.45 GHz frequency band is implemented and tested. Experimental results demonstrate that the radiation of the prototype in the H-plane can be switched between an omnidirectional pattern and broadside patterns with various front-to-back ratios.