An Extended Doublet Substrate Integrated Waveguide (SIW) Bandpass Filter With a Complementary Split Ring Resonator (CSRR)

An ldquoextended doubletrdquo bandpass filter (BPF) is proposed using a substrate integrated waveguide (SIW) cavity with a complementary split ring resonator (CSRR) etched on its top metal plane. Thus, a single-layer BPF with two transmission zeros is realized successfully, with no additional area or layers occupied. The measured and simulated S-parameters of the filter are presented to show its predicted performance, with good agreements obtained between them.