Design of dual-mode SIW cavity filters

For designing the dual-mode substrate-integrated waveguide (SIW) cavity filters, new methods of generating intra-cavity couplings and transmission zeros are presented. Two adjustment techniques for refining the frequency responses are also presented. Compared with a conventional four-pole quadruplet filter, a proposed four-pole dual-mode coupled-cavity filter can provide two additional transmission zeros, which enhance the side-band rejection. A 24-GHz SIW cavity filter with a symmetrical frequency response was designed using the new methods and fabricated using LTCC multilayer process.