Compact ultra-wideband bandpass filter using uniplanar compact photonic bandgap structure

A novel ultra-wideband (UWB) bandpass filter in the whole UWB passband of 3.1-10.6 GHz is proposed and implemented using a uniplanar compact photonic bandgap (UC-PBG) resonator for size reduction. Since the UC-PBG structure has more distributed L-C components than the conventional microstip multiple-mode resonator (MMR), the size reduction is achieved, which is about 34% more than the UWB bandpass filter based on a conventional microstrip MMR. The proposed one-stage UC-PBG filter has four transmission poles, insertion loss < 1.2 dB and group delay variation < 0.14 ns, while the threestage one shows an insertion loss of < 2.2 dB and a group delay variation of < 0.4 ns in the whole UWB band.