DIGITIZED NONLINEAR BEAM AND WAVE INTERAC- TION THEORY OF TRAVELING WAVE TUBE AMPLI- FIERS

Abstract—To simulate the beam and wave interaction (BWI) of various types of traveling wave tube amplifiers (TWTAs), a digitized nonlinear theory has been developed with two features. First, the digitized RF field profiles obtained from electromagnetic simulation software are applied to replace the analytical RF field profiles in TWTAs. Second, the relationship of energy conservation between the beam and RF fields is used to derive the RF field equations. Based on this nonlinear theory, one-dimensional (1-D) code has been constructed to predict the performances of TWTAs. Comparisons between the simulations and the experimental results for three types of TWTAs, i.e., a K-band helix TWTA, a V-band coupled cavity (CC) TWTA and a W-band folded waveguide (FWG) TWTA, are discussed to prove this nonlinear theory. 1