Lossy flat‐passband signal‐interference microstrip filter

Abstract

A type of lossy transversal-signal-interference planar bandpass filter (BPF) with a flattened passband is reported in this Letter. The authors exploit in-series-cascaded transversal filtering sections composed of two in-parallel transmission-line segments and series-type lossy hybrid resonators connected at their input / output accesses. The resistors of these lossy resonators by dissipating part of the RF-input-signal energy in the BPF passband region following a complementary frequency-variation profile with regard to the one associated with conventional substrate filter loss allow obtaining an overall flattened transmission band. To experimentally validate the proposed approach, a 2 GHz microstrip prototype of a sharp-rejection lossy signal-interference BPF with a flattened passband is developed and characterised.