Synthesis Design of Ultra-Wideband Bandpass Filters With Designable Transmission Poles

A class of ultra-wideband (UWB) bandpass filters (BPFs) with designable transmission poles is presented. Transmission poles are controlled in number by introducing m-section non-uniform transmission line in the center of a transmission-line multiple mode resonator. With the help of increased transmission poles, the constituted filter achieves deeper rejection skirts and wider bandwidths. In the design, a synthesis approach is developed to synthesize this filter with the target of Chebyshev equal-ripple frequency responses. As an example, a six-pole UWB BPF is implemented on hybrid microstrip line and slotline structures. The measured results validate and confirm the theoretical prediction.