Tuning-Range Extension Strategies for Varactor-Based Frequency-Reconfigurable Antennas

Tuning range extension strategies for varactor-based frequency-reconfigurable planar patch antennas are presented. The three tuning range optimization methods described in the paper include co-optimization of antenna dimensions and varactor properties, exploitation of multiple radiation modes, and reduction of parasitic capacitance. The first two strategies are emphasized by briefly reviewing two previously reported wide tuning range frequency-agile planar antennas. Importantly, the influence of parasitic capacitance on reducing the tuning range of the varactor-based frequency-reconfigurable antennas is then demonstrated by examining two antennas. The three tuning range extension methods are then combined to further expand the frequency tuning range of a reported frequency-reconfigurable antenna. The antenna has been re-designed, fabricated and experimentally characterized to demonstrate enhanced performance, which validates the proposed techniques, and their simultaneous application to reconfigurable antenna designs.