Substrate Integrated Waveguide Wideband and Ultra-Wideband Bandpass Filters Using Multimode Resonator

In this paper, a novel design technique using substrate integrated waveguide (SIW) based on multimode resonator is presented for the implementation of the dual-band bandpass, wideband bandpass and ultra-wideband bandpass filters. Filter design is started by etching fourW-shaped slots on the upper conductor layer of SIW cavity in order to produce few resonant peaks in passband. W-shaped slots forming up quintuple mode resonator create wide passband while maintaining overall size of the filter to bemuch less. Implemented wide bandpass filter achieves an insertion loss lower than 0.8 dB, return loss better than 12 dB in the passband and 3 dB fractional bandwidth of 44%. The structure is further modified into two H-shaped slots operating as sextuple mode resonator. This design produces an ultra-wideband bandpass filter with an insertion loss smaller than 1.1 dB, return loss better than 11 dB in the passband and 3 dB fractional bandwidth of 55%.