Design of Compact Four-Band Bandpass Filter Based on Multimode Substrate Integrated Waveguide

In this paper, a compact four-band bandpass filter based on multimode substrate integrated waveguide (SIW) is proposed. Tuning of the resonant modes is achieved by introducing metallized vias inside the square SIW resonant cavity. A dual-band filter with four transmission poles is first realized by selecting four modes with weaker electric field strength on the diagonal. Then two triangular cavities are used as dual-mode band-stop resonant cavities to realize a four-band bandpass filter. In this case, a double-layer vertical structure is used, which achieves circuit miniaturization. Finally, a four-band filter is obtained through simulation, which verifies the design feasibility of the compact four-band filter.