Frequency reconfigurable quasi-Yagi dipole antenna

A frequency reconfigurable quasi-Yagi dipole antenna is presented in this paper. Simulation results show that a 35% continuously tuning impedance bandwidth, from 1.85 to 2.5GHz, is obtained. Loaded with varactor diodes, the effective electrical lengths of the driver and director dipoles are varied by changing the biasing voltages. The length adjustable director allows the endfire pattern with relatively high gain being maintained over each tuning sub-band. Across the tuning bandwidth, the predicted gain variation is from 5.8dBi to 7.9dBi. The H-plane cross-polarization level is below -17dB while this value is below -32dB in the E-plane. The front-to-back ratio is better than 12dB.