Wide-band signal-interference duplexer with contiguous single/dual-band channels and its application to quasi-absorptive bandpass filters

A type of wide-band signal-interference planar duplexer with single- and dual-band channels is presented. It exploits transversal-signal-interference-section-based channels with contiguous single- and dual-passband filtering transfer functions. Furthermore, by ending the dual-band channel in a reference-impedance resistor, a wide-band bandpass filter (BPF) with quasi-absorptive stopbands is realised. As experimental validation, microstrip prototypes of a duplexer and a two-stage quasi-absorptive BPF that operate in the 1.6–4.4 GHz range are built and tested.