Compact and High-Isolation Diplexer Using Dual-Mode Stub-Loaded Resonators

• Published in: IEEE microwave and wireless components letters 2014-06, Vol.24 (6), p.385-387
• Main Authors: Guan, Xuehui, Yang, Fangqi, Liu, Haiwen, Zhu, Lei
• Format: Article
• Language: English
• Subjects: Applied sciences; Circuit properties; Couplings; Diplexer; dual-mode resonator; Electric, optical and optoelectronic circuits; Electronic circuits; Electronics; Equipments and installations; Exact sciences and technology; Filtering theory; high isolation and size compactness; Microstrip resonators; Microwave circuits, microwave integrated circuits, microwave transmission lines, submillimeter wave circuits; Mobile radiocommunication systems; Oscillators, resonators, synthetizers; Passband; Radiocommunications; Resonant frequency; stub-loaded resonator; Telecommunications; Telecommunications and information theory; Wireless communication
• ISSN: 1531-1309; 2771-957X; 1558-1764; 2771-9588
• DOI: 10.1109/LMWC.2014.2313591

A novel compact microstrip diplexer for UMTS and WCDMA system is proposed in this letter. The diplexer is mainly composed of three dual-mode stub-loaded microstrip resonators. Two resonant modes of a stub-loaded resonator work together with one mode produced by the common stub-loaded resonator to form a passband or operating band of the proposed diplexer. Extensive study is then conducted on coupling scheme involved in various parts of the diplexer. In particular, the resonance of a resonator is employed to create a desired transmission zero in the stopband, thus improving the isolation between two passbands. The proposed diplexer is in final fabricated and measured. A good agreement between EM simulated and measured results evidently validates the proposed methodology.