Quasi-elliptic Filter with Inline Ports Using a Dual-mode SIW Resonator Loaded by Two GCPWs and One CSRR

A fifth-order bandpass filter (BPF) with in-line input/output ports, implemented by a new hybrid structure of a single dual-mode substrate integrated waveguide (SIW) cavity loaded by two ground coplanar waveguides (GCPWs) and a complementary split ring resonators (CSRR), is proposed. Multiple finite transmission zeros (FTZs) are produced by the multipath energy flow and MEMC. The designed filter has advantages of small volume and sharp cutoff skirts. For the demonstration, a SIW bandpass filter was designed, fabricated and measured.