Ultra-wideband bandpass filter on aperture-backed microstrip line

A novel ultra-wideband (UWB) bandpass filter is proposed on an aperture-backed microstrip line. With an aperture on the ground, a non-uniform resonator is constructed with the first three resonant modes occurring within the UWB band while the parallel coupling between resonator and feeders is largely enhanced. The designed filter exhibits good UWB passband behaviour with insertion loss <1.0 dB and group delay variation <0.25 ns.