A new class of selectivity-improved mm-waves dual-mode substrate integrated waveguide filters

A novel method for implementing high selectivity millimeter-wave (mm-wave) bandpass filters is presented in this paper. A substrate integrated waveguide (SIW) dual-mode circular cavity with a small perturbation is proposed to adjust a transmission zero (TZ) for improving the selectivity by properly changing the location of an additional via-hole placed inside the cavity. Q-band bandpass filters have been designed, fabricated and measured. The experiment results show a good agreement with simulation results. The proposed planar filter has merits of simple design process, high selectivity, expanded bandwidth, and compact size.