Differential substrate integrated waveguide bandpass filter with improved common‐mode suppression utilising complementary split‐ring resonators

A novel differential substrate integrated waveguide bandpass filter is proposed. The TE 102 ‐mode cavities arranged on the symmetrical plane could efficiently reduce the common‐mode (CM) signal, meanwhile, transmitting the differential‐mode signal. Additional transmission zeros have been obtained by using cross coupling in the dual‐mode cavities. Moreover, by symmetrically etching complementary split‐ring resonators on the bottom layer of the substrate, the CM could be suppressed whereas differential signals are not affected. To verify the above design concept, a prototype operating at 8.07 GHz has been realised and shows the desired filtering performance.