V-band bandpass filter with continuously variable centre frequency

A second-order bandpass filter (BPF) with continuously variable centre frequency tuning is presented in this article. Evanescent-mode cavity resonators with variable capacitive loadings are used as tuning elements. Tuning is achieved by means of micro-electromechanical-systems (MEMS)-actuated highly conductive rigid fingers that feature an out-of-plane deflection. For an applied DC bias voltage between 0 and 27.3 V the centre frequency of the BPF is tuned from 67.4 to 63.2 GHz (4.2 GHz). For this frequency band, the fractional bandwidth (FBW) varies between 8.3 and 3.4% and the in-band insertion loss between 1.45 and 5 dB.