Band-Reconfigurable Filter With Liquid Metal Actuation

A substrate integrated waveguide band-reconfigurable filter with four configurations: 1) dual band; 2) low band; 3) high band; and 4) no-band, is presented. Liquid metal is chosen to enable switching between the different configurations by filling or emptying certain via holes and channels. By altering the liquid metal placement in the filter, cavity boundaries and transmission lines are adjusted to obtain the desired response. In order to demonstrate the concept, a prototype filter in C-band is designed and fabricated. The frequency responses of the liquid-metal-actuated filter (in all operating configurations) are compared with simulated and fabricated copper-plated filters. Good agreement is observed between the simulation results and the measurements. For the single- and dual-band filter configurations, insertion loss less than 1.9 dB and return loss greater than 16 dB are achieved at the center frequencies of 4.6 and 7 GHz. For the no-band (or all-stop) configuration, isolation is better than 36 dB over the entire band between 4 and 8 GHz. Additionally, to quantify the impact of using liquid metal, unloaded quality factors of a fabricated liquid-metal-actuated and copper-plated resonator are compared. The presented filter clearly demonstrates the potential of using liquid metal actuation in future reconfigurable RF hardware.