Full Bandpass Filter Reconfigurability Through Liquid Metal Tuning and a Novel External Coupling Technique

An innovative filter design with full independent control of the center frequency, bandwidth, and response ripple is demonstrated utilizing only liquid-metal actuation. This is realized on substrate-integrated waveguide (SIW) technology with tunable evanescent cavity resonators coupled by an adaptable inductive iris design. A novel external coupling mechanism utilizing liquid-metal tuning posts on the filter input/output is presented. The fully reconfigurable filter design has a center frequency tuning range of 4.5–5.6 GHz with bandwidths ranging from 198 to 599 MHz. The response shape is reconfigurable between Butterworth and equi-ripple responses at all frequency and bandwidth states. Agreement between experimental results and simulation validate the effectiveness of this highly reconfigurable filter design and the capabilities of liquid metal for adaptive coupling mechanisms.