Design of a novel coupled-cavity circuit for a 35 GHz wideband Traveling-Wave Tube

The design and analysis of a wideband coupled-cavity Traveling-Wave Tube (TWT) operating at 35 GHz is presented. The interaction circuit employs a novel coupled-cavity circuit, which is based on the combination of a three-slot ladder coupled-cavity slow-wave structure and round electron beam. In this paper, the high frequency properties such as dispersion characteristics, beam-wave interaction impedance are studied and optimized, and combined with design of the well-matched couplers, a 3-D particle-in-cell model of the coupled-cavity TWT is constructed. The electromagnetic characteristics and the beam-wave interaction of the tube are investigated. From our calculations, it can produce saturated output power over 900 Watts in 4 GHz bandwidth ranging from 33 to 37 GHz when the cathode voltage and beam current are set to 16 kV and 500 mA, respectively. The corresponding saturated gain and electron efficiency can reach over 43.3 dB and 11.4%. Compared with the Hughes-type and double staggered ladder coupled-cavity TWT, our designed TWT has absolute advantage in bandwidth, and also it is more competitive in power capability and electron efficiency.