A 2.2–4.2 GHz low-loss tunable bandpass filter based on low cost manufacturing of ABS polymer

A low loss, tunable, second order, bandpass filter covering the range 2.2-4.2 GHz is presented. The filter is based on evanescent-mode cavity resonators and manufactured by CNC machining of low cost acrylonitrile-butadiene-styrene (ABS) plastic. The filter has an insertion loss from 0.77-0.26 dB, with a 3-dB fractional bandwidth from 8.4% to 9.1%. The extracted unloaded quality factor (Q) of the resonators is 500-700 over the tuning range.