Multi-Section Inhomogeneous Coupled-Line Filters with Large Mode-Velocity Ratios

Design data for single-section inhomogeneous coupled-line filters based on large even/odd mode-velocity ratios has recently been published [1], The purpose of this paper is to extend those results to multi-section inhomogeneous coupled-line filters with large mode-velocity ratios. Both experimental and theoretical data are presented. The rather complex pole-zero structure of single-section inhomogeneous coupled-line filters permits great flexibility in designing multi-section filters. Very sharp transitions between pass- and stop bands are possible as well as large stopband to passband width ratios.