Synthesis of Novel Wideband Filter Using Stub-Loaded Parallel-Coupled-Lines

A wideband bandpass filter (BPF) composed of two cascaded single-short-circuited-stub-loaded parallel-coupled-lines (SSCSL-PCLs) and two short-circuited shunt stubs at ports are theoretical investigated for the first time. The synthesis formulae of the BPF are derived based on the equi-ripple filtering function. As an example, a wideband BPF with a fractional bandwidth (FBW) of 33% is synthesized. The designed filter is then simulated, fabricated and measured. The good agreement validates the effectiveness of the newly proposed filter structure and the corresponding synthesis technique.