Generalised parallel‐coupled line and interdigital filters with unusually broad upper stop bandwidth:synthesis and design in homogeneous media

The synthesis and design of generalised parallel‐coupled line and interdigital filters suitable for realisation in a homogeneous media are proposed in this study. The filters comprise novel coupled line sections whose synthesis is discussed in detail leading to the derivation of formulae to evaluate their modal‐impedances. It will be shown that the proposed filters comprise asymmetrically coupled stepped‐impedance resonators and are capable of realising broad upper stopbands. Filter examples are synthesised and subsequently realised in suspended‐substrate stripline technology were simulated utilising High Frequency System Simulator (HFSS) show close correspondence to theoretical predictions.