Tunable bandpass and bandstop filter cascade for dynamic pole allocation

In this paper, a highly dynamic filter cascade is presented with the capability of creating very high isolation regions in close spectral proximity to the received signal of interest. The cascade consists of 10 widely tunable resonators that can be combined to form advanced filtering functions. Two of the resonators are tasked to create a second-order Butterworth bandpass filter, while the other eight are used in a bandstop configuration to manipulate the stopband and form either very deep isolation, wide band isolation, or multiple isolation regions. This device consists of substrate-integrated, evanescent-mode cavities that are created using traditional circuit board technology as an example. 120 dB of isolation over a bandwidth of 21 MHz is achieved 16% away from the passband of the bandpass filter.