Miniaturized and high-selectivity substrate integrated waveguide (SIW) bandpass filter loaded by complementary split-ring resonators (CSRRs)

This paper presents an effective technique to obtain miniaturized and high-selectivity substrate integrated waveguide (SIW) bandpass filters by loading complementary split-ring resonators (CSRRs) at the SIW cavities. The existence of the CSRR enables a considerable reduction of the resonance frequency of a conventional SIW cavity thanks to the coupling effect between CSRR and SIW cavity. Besides, a sharp roll-off is generated in a higher stopband due to the characteristics of CSRRs. To demonstrate the operation principal, the second- and third-order SIW bandpass filters are fabricated using standard printed circuit board technology, showing advantages of compact size, good selectivity, easy fabrication, and integration with other circuits. The measured -parameters agree well with the simulated ones.