Wide-band Microwave Bandpass Filters With Hybrid Rings

A new type of sharp, high-rejection microwave planar bandpass Alter based on signal-interference techniques is reported. The proposed topology uses, for the first time, hybrid-ring couplers operating as transversal altering sections (TFSs). High-selectivity ultra-wideband (UWB) or flat in-band group-delay wide-band bandpass Altering responses are achievable with this TFS. Design equations and guidelines for the described hybrid-ring-based TFS are also provided. Furthermore, to demonstrate its practical viability, two UWB microstrip Alter prototypes at 5 GHz are synthesized, manufactured and characterized.