Behavioural digital modelling of lossy frequency‐periodic microwave passive filters

Abstract

The theoretically synthesised power transmission response of several classes of RF/microwave passive filters is frequency periodic. Examples of these filters include those exploiting signal‐interference techniques as well as those consisting of stub‐loaded circuit networks. A behavioural z‐plane digital modelling of these ideally synthesised frequency‐periodic high‐frequency filters has been recently proposed. It led to innovative explanations for commonly observed spurious resonant peaks and circuit redundancies in suboptimal designs. This work reports on a novel behavioural discrete‐time modelling methodology for frequency‐periodic microwave lossy filters. It considers for the first time the effect of high‐frequency losses by introducing a σ parameter on the originally lossless transfer function. For practical‐validation purposes, the manufacturing and characterisation of a new type of generalised stub‐loaded‐based extended‐upper‐stopband bandpass filter along with its lossy digital modelling are shown.