Design of a Ka/V-band rectangular folded traveling wave tube with a hollow-sheet-beam

In this paper a rectangular-folded-waveguide (RFW), using a hollow-sheet-beam, is proposed. The structure is designed to work with a cathodic voltage of 16 kV and a beam current of 0.3 A with a gain of at least 30 dB from 44 to 54 GHz. The simulation, carried out with CST Studio 2023, for a structure composed of two sections of 20 periods each, shows that the introduction of a hollow-sheet-beam allows an improvement of the performance equal to 31 % with respect to a classical circular beam and to 17 % with respect to a sheet-beam. In terms of performance, the structure reaches a saturated output power equal to 721 W, a maximum gain of 38 dB and an electronic efficiency of 15.7% at 49 GHz. With these performances and a -3 dB bandwidth ranging from 40.3 to 51.8 GHz, the proposed structure is fit for all the applications where it is necessary to maximize bandwidth and minimize power consumption.