A Tunable X-Band Substrate Integrated Waveguide Cavity Filter Using Reconfigurable Liquid-Metal Perturbing Posts

A tunable bandpass filter based on reconfigurable liquid-metal perturbing posts in a substrate integrated waveguide (SIW) cavity is demonstrated. The design consists of four reconfigurable posts in a single cavity which provide five center frequencies from 10.13 GHz to 11.31 GHz. To enable frequency tuning, nontoxic liquid-metal Galinstan is hydraulically actuated to activate and deactivate posts. The five states have an average peak insertion loss of 1.35 dB with fractional bandwidths of 0.6% to 1 % and unloaded quality factors of 96 to 154.