A dielectric loaded bandpass filter based on half-mode substrate integrated waveguide

A type of bandpass filter (BPF) based on the half-mode substrate integrated waveguide (HMSIW) loaded with dielectric rods is designed and developed. The proposed filter can operate below the characteristic cutoff frequency of HMSIW, thus compact size can be achieved. Some slots etched on HMSIW are used in the filter development to reduce coupling effects between the dielectric rods. Furthermore, an ultra-wide out-of-band rejection contributed to the slots is obtained. The proposed filter has the advantages of compactness, wide out-of-band rejection characteristic, low insertion loss, and low cost.