Scattering and radiation properties of varactor-tuned microstrip antennas

Experimental and theoretical results are reported for a circular microstrip patch antenna whose scattering and radiation responses are tuned by controlling the bias voltage across a varactor diode that is mounted between the conducting patch and the ground plane. This tunable microstrip patch antenna enjoys a substantially wider impedance bandwidth than the same microstrip antenna without the varactor. In addition, the scattering response of the antenna can be tuned to minimize the return at threat frequencies. By varying the diode bias from 0 to 20 V, it was possible to tune the resonant frequency of the antenna over a 50% bandwidth.<>