Compact UWB BPF with notch band based on SW-HMSIW

A compact ultra-wideband (UWB) bandpass filter (BPF) with a notch band based on a slow-wave half-mode substrate-integrated waveguide (SW-HMSIW) is proposed. The proposed SW-HMSIW is believed to be the first ever reported. Similar to the slow-wave substrate-integrated waveguide (SW-SIW), SW-HMSIWs can achieve highpass characteristics, while the lateral width is reduced by about 50%. To obtain the UWB response, three spiral compact microstrip resonant cells are etched on the SW-HMSIW as a lowpass filter. Moreover, a short-circuited quarter wavelength L-type resonator is used to achieve a notch band. To validate the design theory, a compact UWB BPF is designed and fabricated. The simulated results are compared with the measured results, and good agreement is reported.