A Tunable Filter with Extended Tuning Range Based on Switched Dual Resonance Cavities

This paper presents a novel tunable filter with a wide tuning range. The compact design realizes two independent resonant modes in a cavity and uses each mode to realize a tunable filter in a sub-band. The two adjacent bands make it possible to realize a wide tuning range, without facing the constraints present in tunable filters using a single resonant mode. Controlling the dispersion effects is essential to maintain filter performance while the center frequency is varied. The two modes are fully independent, their field patterns are orthogonal. In addition since the input/output ports are coupled to the two modes, the filter is used such that, while operating in a sub-band, the other mode of operation is detuned away. A proof of concept design of a three pole filter with tuning range covering the L-band is presented. A tuning range of 2:1 is demonstrated experimentally thus verifying the design approach.