Novel compact dual-band bandpass filter adopting SIW cavity

A novel transverse electromagnetic-substrate integrated waveguide (TEM-SIW) cavity is presented in this paper.The TEM-SIW cavity is developed from traditional SIW cavity.Through inserting a short metal pin into the centre of the SIW cavity and opening the top metal plane of the SIW cavity to its metal sidewall, the TEM-SIW cavity can be achieved.The size of the TEM-SIW cavity can be reduced to 9.5% of the traditional SIW cavity in the same resonant frequency.Then this paper analyzes the structure and magnetic field distribution of TEM-SIW cavity and traditional SIW cavity in the dominant mode.The magnetic field distribution of TEM-SIW cavity is found to be similar with those of the capacitor loaded coaxialcavity in the TEM mode.Therefore, the coupling structure and designed techniques for the classical capacitor loaded coaxial-cavity filters can be easily used in the filters with the TEM-SIW cavities.Finally, a dual-band bandpass filter (BPF) adopting TEM-SIW cavity is designed and presented in this paper, and the performance of the designed dual-band bandpass filter is validated numerically and experimentally.