Coalesced single-input single-output dual-band filter

An experimental proof-of-concept two-terminal single-input and single-output (SISO) 1.7GHz/4.1GHz dual-band filter is presented. It incorporates the so-call frequency-selective resonators that are composite in structure, cascading a microstrip and microstrip on a two-dimensional periodical surface or the so-called PBG (photonic bandgap) ground plane. The composite resonators add additional degrees of freedom for controlling the relative positions of the passband center frequencies. Thus making the dual-band filters, which essential share one common layout. Measured and theoretical filter characteristics for such coalesced dual-band filter agree excellently, validating the proposed concepts.