Signal amplification in an O-type TWT with noise in the electron beam

Approximate nonlinear theory is used to analyze the amplification of signals and narrow-band microwave noise due to stochastic modulation of electron velocity and current at the input of an O-type traveling wave tube. Formulas are derived for calculating the noise coefficients of the tube as a function of dimensionless parameters and degree of nonlinearity. It is shown that in the nonlinear regime the coefficient of amplitude noise is smaller than in the linear regime, while the coefficient of phase noise is larger than in the linear regime. Both in the linear and nonlinear regimes the maximum relative contribution to the noise coefficient is made by antenna noise as well as noise due to velocity fluctuations; the smallest contribution is made by current fluctuations of the electron beam.