Novel substrate integrated waveguide bandpass filter with broadside-coupled complementary split ring resonators

A novel substrate integrated waveguide (SIW) bandpass filter employing integrated broadside-coupled complementary split-ring resonator (BC-CSRR) pairs is presented. The proposed filter is operated below the cutoff frequency of the SIW. The BC-CSRR structure is first introduced and the response of the resonator, which is formed from an SIW section combined with a pair of BC-CSRRs, is then investigated. The final filter is implemented based on two cascaded SIW BC-CSRR pairs coupled by an evanescent-mode section. Simulated results and experimental verification are provided. It is shown that the proposed resonator can be miniaturized by simply using a thin substrate, and the proposed filter has the advantages of compact size, high selectivity, easy fabrication and integration with other circuits.