Compact Quadruple-Mode Wideband Bandpass Filter Using L-Shaped Feed-Line in a Single Cavity

• Published in: IEEE microwave and wireless components letters 2021-10, Vol.31 (10), p.1111-1114
• Main Authors: Zhang, Zhi-Chong, Wong, Sai-Wai, Yu, Xuzhou, Zhao, Bingxiong, Wang, Diji, Chen, Ruisen
• Format: Article
• Language: English
• Subjects: Band-pass filters; Bandpass filter (BPF); Bandpass filters; Broadband; cavity; Cavity resonators; Filtering theory; L-shaped feed-line; Microwave filters; Microwave theory and techniques; quadruple-mode; Resonant frequency; Resonator filters; Wideband
• ISSN: 1531-1309; 2771-957X; 1558-1764; 2771-9588
• DOI: 10.1109/LMWC.2021.3107952

This letter presents a novel quadruple-mode cavity wideband bandpass filter (BPF). Unlike the conventional coaxial cavity resonator, the proposed cavity resonator is made up of two symmetrical conductive posts in a cylindrical cavity, while four resonant modes of the cavity resonator are classified as TM 01 mode, TM 11 mode, and a pair of TE degenerate modes (TE+ mode and TE− mode). All of the four modes are excited by a pair of L-shaped feed-lines. In addition, the four resonant modes are employed to constitute the passband of wideband BPF with a fractional bandwidth (FBW) of 45% at the central frequency of 2.2 GHz. Finally, the proposed filter is designed and fabricated. Good in-band filtering performance, wide upper stopband, and compact size are realized.