A novel ultra wideband bandpass filter using broadside coupled structures on multilayer organic liquid crystal polymer substrate

This paper proposes a novel ultra wideband (UWB) bandpass filter using multilayer quasi-lumped structure on organic liquid crystal polymer (LCP) substrate. In this study, broadside coupled square patches and high impedance microstrip lines are adopted as quasi-lumped elements for realizing proposed filter. A 7-pole ultra wideband bandpass prototype is designed based on lump-element bandpass filter and verified by full-wave simulation. The designed BPF is fabricated using multilayer organic liquid crystal polymer (LCP) process and measured using vector network analyzer. Good agreement between simulated and measured responses is observed. The measurement results show that the fabricated filter has a fractional bandwidth of 118.75% and low insertion loss of 0.25 dB at centre frequency 6.4 GHz. The measured filter has wide stopband and excellent rejection level higher than 31.7 dB from 11.5 GHz to 17.20 GHz.