Signal-interference bandpass filters with dynamic in-band interference suppression

摘要

This paper focuses on the design of wide-band bandpass filters (BPFs) with dynamic in-band interference suppression. They are based on a new class of a signal-interference transversal filtering section (TFS) that consists of three signal paths that are effectively combined so that an absorptive notch (AN) ??? exhibiting theoretically infinite attenuation ??? is created within the BPF passband. In the devised implementation, the center frequency of the rejection band is reconfigured by altering the resonant frequency of two capacitively-loaded microstrip-line resonators that are incorporated into one of the propagation paths. The proposed design approach allows realizations of filter circuits with approximately 50% smaller size than that of conventional filter cascades shaped by the series connection of a BPF and an AN filter. For proof-of-concept validation purposes, an experimental prototype is built and measured. It demonstrates a tunable AN between 1.8 and 2.5 GHz located within a wide-band passband centered at 2 GHz.