Open-loop temperature-compensated tuning of a 2-pole absorptive bandstop filter

For the first time, an open-loop temperature-compensated control scheme is presented for a tunable 2-pole absorptive bandstop filter. The scheme includes a post-fabrication calibration that extracts the filter poles and zeros and generates a model of the zeros with respect to bias condition across −35 to 100° C. The bias voltages needed to achieve a target notch at a sensed temperature are determined based on this model. Measured filter tuning shows 20–48 dB improvement in isolation from 1.7–2.1 GHz compared to tuning without temperature compensation and frequency variation of less than ±0.03% from −35 to 100° C.