Stepped Circular Waveguide Dual-Mode Filters for Broadband Contiguous Multiplexers

• Published in: IEEE transactions on microwave theory and techniques Vol. 61; no. 1; pp. 139 - 145
• Main Authors: Hai Hu, Ke-Li Wu, Cameron, R. J.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.01.2013; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Cavity resonators; Circuit properties; contiguous multiplexers; Couplings; Design; Dual-mode waveguide filters; Electric, optical and optoelectronic circuits; Electronic circuits; Electronic equipment and fabrication. Passive components, printed wiring boards, connectics; Electronics; Exact sciences and technology; Fasteners; Frequency filters; Integrated circuit modeling; Inverters; Iris; Microwave circuits, microwave integrated circuits, microwave transmission lines, submillimeter wave circuits; Resonant frequency; Ku band; Performance evaluation; Waveguide filters; Inverter; Dual-mode waveguide filters; Modal analysis; Useful information; Microwave; Wavelength division multiplexing; Centimetric wave; Waveguide; Microwave multiplexer; Multichannel filter; Mode filter; contiguous multiplexers; Two mode waveguide; Spurious signal; Frequency band; Cavity; Wide band; C band; Optical fiber communication; Impedance; Circular waveguide
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/TMTT.2012.2227787

A stepped circular waveguide dual-mode (SCWDM) filter is fully investigated in this paper, from its basic characteristic to design formula. As compared to a conventional circular waveguide dual-mode (CWDM) filter, it provides more freedoms for shifting and suppressing the spurious modes in a wide frequency band. This useful attribute can be used for a broadband waveguide contiguous output multiplexer (OMUX) in satellite payloads. The scaling factor for relating coupling value M to its corresponding impedance inverter K in a stepped cavity is derived for full-wave EM design. To validate the design technique, four design examples are presented. One challenging example is a wideband 17-channel Ku-band contiguous multiplexer with two SCWDM channel filters. A triplexer hardware covering the same included bandwidth is also designed and measured. The measurement results show excellent agreement with those of the theoretical EM designs, justifying the effectiveness of full-wave EM modal analysis. Comparing to the best possible design of conventional CWDM filters, at least 30% more spurious-free range in both Ku-band and C-band can be achieved by using SCWDM filters.