Analysis of a broadband Q band folded waveguide traveling-wave tube

A highly reproducible, low-cost folded waveguide traveling-wave-tube amplifier is designed using the Pierce theory and a three-dimensional (3-D) particle-in-cell (PIC) code. The amplifier is designed to operate at 40-48 GHz with peak output radiation power of 200 W. Initial circuit parameters are obtained from the Pierce theory and circuit dispersion relations. A nonlinear large-signal performance of the amplifier is predicted from 3-D PIC simulations. Simulations show that the amplifier produces a saturated radiation power of 200 W at 44 GHz, corresponding to 5.6% electronic efficiency where the beam voltage and current are 21 kV and 0.17 A, respectively. A saturated 3-dB bandwidth is found to be 16% (40.5-47.5 GHz).