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.