Varactor controlled frequency and polarization reconfigurable microstrip antenna

A single feed compact microstrip antenna achieving frequency and polarization diversity using a varactor is presented. A simple patch antenna with an X-slot constitutes the fundamental structure. The frequency and polarization agility is realized by varying the reactance of an embedded varactor at the center of the X-slot with respect to the biasing from 0 to 25 V. The prototype fabricated on a substrate of dielectric constant (er) 4.4 and height (h) 1.6 mm is fed by a proximity feed fabricated using the same substrate. By controlling the bias voltage of the varactor, the polarization of the antenna can be switched between linear and circular polarization. Furthermore, the proposed antenna offers stable broadside radiation characteristics without any extra impedance matching circuit. The frequency and polarization diversities of this design could potentially improve the reliability of wireless communication systems. The details of the antenna are presented and discussed. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE , 2011.