Novel UWB BPF design using modified trisection MMR

A novel ultrawideband (UWB) bandpass filter (BPF) is proposed and designed using a multimode resonator (MMR) that is modified from a conventional trisection stepped-impedance resonator (TSSIR). With the first five resonant modes of the TSSlR and the coupling peaks of the input/output interdigital parallel-coupled lines properly located in the UWB passband, a seven-transmission-pole UWB BPF was realized. Open stubs were embedded in the MMR to produce a transmission zero for improving the upper-stopband rejection. A prototype of the proposed UWB BPF has been fabricated and measured for performance verification. Besides a measured return loss of higher than 11 dB between the lowest and highest transmission poles, the measured results show a minimum insertion loss of 0.3 dB and a group delay variation of less than 0.07 ns in the UWB passband.