An Inductor-based Real-time Monitoring and Control System for Tunable Cavity MEMS Filters

A monitoring and control system for tunable, silicon-based, evanescent-mode cavity filter is presented in this paper for the first time. The feedback system relies on inductive sensing to detect the deflection of the tuning MEMS membrane of the filter. The sensing inductor also functions as the electrostatic actuator of the membrane. Based on the reading from the sensing circuit, the electrostatic bias voltage is adjusted until the desired RF response is achieved. The system is demonstrated on a bandstop filter (BSF) tunable from 30–42 GHz, providing 24–52 dB rejection. The sensing circuit consumes 0.88 W per resonator from a single +5 V supply voltage. The circuits used are fully electronic and suitable for compact and low power embedding.