Beam steering patch antennas using reconfigurable parasitic elements of tunable electrical size

A method of designing beam steering microstrip antennas using reconfigurable parasitic patches is proposed in this article. The first beam steering antenna is composed of a driven patch and two parasitic patches placed on the H-plane of the antenna. The effect of the length and width of parasitic patches, and the spacing between the driven and parasitic elements on the radiation pattern of the antenna is analyzed in detail. The parasitic patch is loaded with a varactor in the center with its dc biasing network. By adjusting the capacitance value of the varactor, the electrical sized of the parasitic patch is changed to achieve beam steering. Maintained impedance matching can be obtained without compensation structure. An experimental antenna is designed and fabricated to verify the method. The measured return loss is better than 12 dB at the center frequency 2.4 GHz for all cases and the measured gain is from 6.5 to 7.6 dBi. The beam steering angles of the simulation and measured results are +/- 45 degrees and +/- 35 degrees, respectively.