AUTHOR=Wang Nan , Wei Haokun , Gao Kun , Ruan Xiting , Chen Xiaojian , Xu Qian , Yang Qian , Zhang Anxue , Liu Shuangyang TITLE=Dual-Band Bandpass Filter With Controllable Stopband Bandwidth JOURNAL=Frontiers in Physics VOLUME=9 YEAR=2022 URL=https://www.frontiersin.org/journals/physics/articles/10.3389/fphy.2021.809752 DOI=10.3389/fphy.2021.809752 ISSN=2296-424X ABSTRACT=

A novel dual-band bandpass filter (BPF) is proposed with independently controllable transmission zeros (TZs) which can realize widely tunable stopband bandwidth (BW). The planar microstrip filter consists of a three-degree L-C ladder lowpass filter loaded with two unsymmetrical shorted stubs which are used to produce different TZs. By tuning the parameters of the two unsymmetrical shorted stubs, the TZs can be independently controlled. Therefore, the BPF has independent controllable center frequencies (CFs), passband bandwidths, and stopband bandwidths between adjacent passbands. All the L-C values in the equivalent circuit of the proposed filter are optimized to fulfill the design specifications. For demonstration, a dual-band BPF is designed. The measured results show good agreement with the simulated ones.