A high-Q octave-tunable all-silicon cavity filter using magnetostatic actuation

Abstract

This paper presents, for the first time, a magnetostatically tuned capacitive-post loaded evanescent-mode cavity filter for C..X band reconfigurable RF front-ends. Unlike electrostatically-actuated MEMS tuners that exhibit unidirectional actuation, the presented technique allows for bidirectional tuner deflections to be achieved. The measured device is a two-pole Butterworth bandpass filter that demonstrates an analog tuning from 6.8-13.2 GHz (1:1.94 tuning ratio) while maintaining a near-constant 1% fractional bandwidth. The filter insertion loss varies from 4.2-1.8 dB (including connector losses) from the lowest to highest frequency, which corresponds to an unloaded quality factor of 300-700. The filter has an overall size of ≤ 1 in ³ including fixture, and consumes ≤ 0.5 W DC-power per-pole in the bi-directional magnetostatic actuation to achieve maximum tuning. Such tuning methods are potentially useful in applications where power consumption is not a major constraint (e.g. base stations) and/or where bidirectional tuner actuation is desired.