Planar single-/dual-band beidpass filters based on new per turbed multi-mode SAW circular cavity

In this paper, new single- and dual-band bandpass filters are implemented based on the perturbed multi-mode substrate integrated waveguide (SIW) circular cavity. For the single-band filter, the TM010 mode, TM110A mode, and TM210A mode are simultaneously utilized to realize the triple-mode resonance response, of which both the bandwidth and central frequency can be flexibly adjusted by allocating the perturbation position properly. Meanwhile, for the dual-band operation, the TMoio mode, TM110A mode, and TM210A mode are arranged to realize the lower passband, whereas the TM210B and TM020 modes are excited to generate the upper passband. The working principle of the filters' coupling topology is explained in detail. For concept verification, both the triple-mode single-band and multimode dual-band filters are designed, manufactured and measured, with the measurement results are separately in good agreement with the corresponding simulations.