Design and Measurement of a Nonlinear-Curve Directional Coupler for Sheet Beam Traveling Wave Tube

• Published in: IEEE transactions on electron devices Vol. 63; no. 9; pp. 3733 - 3739
• Main Authors: Liya Yang, Jianxun Wang, Guoxiang Shu, Guo Liu, Balfour, E. Agurgo, Yelei Yao, Kun Dong, Hao Fu, Yong Luo
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.09.2016; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Apertures; Bandwidth; Beams (radiation); Chebyshev approximation; Computer simulation; Couplers; Coupling; Couplings; Design analysis; Design engineering; Directional coupler; H-plane; nonlinear-curve coupling aperture; Rectangular waveguides; sheet beam traveling wave tube; Traveling wave tubes
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2016.2593663

A new type of input/output coupler for sheet beam traveling wave tube is designed, analyzed, and measured in this paper. In the design, a special sloped coupling aperture distributed between two paralleled rectangular waveguides in H-plane is employed for compact dimensions, ease of fabrication, attainment of high power capacity, and more convenience for periodic cusped magnet focusing system. A nonlinear-curve profile with Chebyshev-curve distribution is applied to extend the operating frequency bandwidth while suppressing reflections to avoid generating oscillation in the slow-wave structure. Based on the analytical investigation and numerical simulation, an optimized sloping angle of the coupling aperture is obtained to improved performance. Simulations imply that the coupler achieves a broadband bandwidth (S 11 <; -20 dB) of 23 and 10 GHz in W- and Q-band, respectively, with coupling coefficient above -0.2 dB. Cold test results satisfactorily agree with simulations.