Gain Enhancement Using Phase Velocity Taper in Folded Waveguide Slow Wave Structure for W Band Traveling Wave Tube Amplifier

In this paper, gain is enhanced by the introduction of step taper towards the end of a folded wave-guide slow wave structure for W band traveling wave tube amplifier. The effect of mean-path on the dispersion characteristics and interaction impedance are presented. A complete SWS with uniform mean path length in each cell is initially designed and optimized to obtain maximum possible gain by employing an electron beam with speed of 0.178 times the speed of light. The gain of up-to 22.3 dB was achieved in the operational bandwidth of 80 to 87 GHz. Gain was improved up-to 23.5 dB by introducing two steps of altered phase velocities towards the end of the SWS.