Compact ultra-wideband bandpass filter using broadside coupled hairpin structures on multilayer liquid crystal polymer substrate

A novel ultra-wideband (UWB) bandpass filter (BPF) using a broadside-coupled hairpin structure and multilayer organic liquid Crystal polymer (LCP) technology is presented. To suppress stopband harmonic response. folded stepped impedance structures were adopted as hairpin resonators ill the design. The proposed filter has been investigated numerically and experimentally. Multilayer LCP technology was used to implement designed UWB BPF. Good agreement between simulated and measured results of the proposed filter was observed. They show that the fabricated UWB BPF has a good performance. including a small insertion loss, a flat group delay with a variation within 0.1 ns in most of its passband, a wide stopband Front 11.0-20.0 GHz with a high rejection level tip to 20.0 dB. and a very compact size of 9.8 x 7.5 mm (0.36 lambda g x 0.27 lambda g, where lambda g is the guided wavelength of 50 12 microstrip line at 6.85 GHz).