Compact Triple-mode HMSIW Filter Using Quarter-Wavelength Co-planar Waveguide

A Compact triple-mode half-mode SIW (HMSIW) filter incorporated with quarter-wavelength co-planar waveguide is proposed in this paper. TE202 mode is towards to the higher frequency by introducing the second via-hole in the cavity. A pair of quarter-wavelength co-planar waveguides (CPWs) resonators is introduced on the open-side of the HMSIW, which can reduce the resonant frequency of the second mode. After working principle and design method of this proposed filter are well-illustrated, a prototype with 15 dB fractional bandwidth of 10.4% at 4.8 GHz is finally designed. And the upper stopband is up to 1.44f₀ with the rejection level larger than 20 dB.