Measured and theoretical nonlinear phase distortion in traveling-wave tubes

The nonlinear phase distortion in traveling-wave tubes is calculated in order to obtain its dependence on design and working parameters by using a large-signal theory. The relation between the nonlinear phase distortion and the output power due to the reduction of the average electron velocity is also studied. AM-PM conversion coefficients are directly measured along a tube with no local attenuator and found to be in fairly good agreement with the theoretical values. A vector diagram representation and equations of simple form are developed, and their adaptability for the physical description of the nonlinear phase distortion are demonstrated.