Behavioural digital modelling of lossy frequency-periodic microwave passive filters

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 highfrequency 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 s 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.