Continuously-Tunable Substrate Integrated Waveguide Bandpass Filter Actuated by Liquid Metal
An elegant continuously-tunable bandpass filter with a wide tuning range based on liquid metal is presented. The filter is realized using square substrate integrated waveguide cavity resonators, capacitively loaded with liquid metal posts at the center of the resonators. By changing the height of the liquid metal posts, and hence altering the loading capacitances, the resonant frequencies of the resonators are continuously tuned. To prove the concept, a second order bandpass filter is realized and measured. Measurements confirm the wide range tunability of the filter. This demonstrates that liquid-metal, continuous tuning is a promising mechanism for future frequency-agile filter applications.