Substrate integrated waveguide (SIW) based on novel double-sided-complementary spiral resonators (DS-CSRs)

In this paper, a novel substrate integrated waveguide (SIW) loaded with double-sided complementary spiral resonators (DS-CSRs) is investigated and its applications to the miniaturized bandpass filters will be presented. The proposed structures allow implementation of a forward-wave passband propagating below the characteristic cutoff frequency of the waveguide. Due to extra coupling effect between CSRs of the top and bottom layer, a much lower resonance frequency has been achieved compared to conventional single CSR, which is etched on the surface layer of SIW. Then the method of designing bandpass filters is illustrated. As a practical case, the application of this novel waveguide and DS-CSR combination technique to design the miniaturized bandpass filer with two-order is designed and investigated soon afterwards. All of these resonators and filters are simulated by CST MWS software, which is based on finite different time domain. Good agreement is obtained between the analysis and the simulation results.