Extended-Doublet Half-Mode Substrate Integrated Waveguide Bandpass Filter With Wide Stopband

A half-mode substrate integrated waveguide (HSIW) filter incorporated with co-planar waveguide (CPW) and co-planar strip (CPS) is proposed. Quarter-wavelength CPW and half-wavelength CPS resonators etched on the top metal layer are used to realized extended-doublet topology. Meanwhile, wide stopband characteristic is obtained, which is due to different higher order resonant frequencies of HSIW, CPS, and CPW. Finally, an HSIW filter is designed and measured, good agreements are achieved between measured and simulated S-parameters.