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.