5-GHz bandpass filter demonstration using quarter-mode substrate integrated waveguide cavity for wireless systems

A planar integrated bandpass filter (BPF) structure that makes use of a quarter-mode substrate integrated waveguide (QMSIW) technique is presented in this work for the first time. The proposed bandpass filter is composed of cascaded QMSIW cavities, which are magnetically coupled with the neighbourhood sections. The quarter-mode structure of SIWs makes the overall size largely reduced so it is possible to use the waveguide technique for low-profile integrated filters within few GHz. To demonstrate the design concept, two C-band four-pole Chebyshev filters are designed for different bandwidth applications. Measured results are presented and compared with the full-wave simulated results. Good agreement has been observed.