Theory of the Large Signal Behavior of Traveling-Wave Amplifiers

We present results of calculations on the amplification, phase distortion, and harmonic content in an idealized traveling-wave amplifier when excited to levels beyond those for which the device behaves linearly. The idealization consists mainly of neglecting the action on the electron beam of radio-frequency fields due to the space charge in the beam. The limiting efficiency and the phase distortion are given for various values of the beam-to-circuit coupling parameter and of the electron injection velocity. The relative harmonic content of the beam is given to the fifth harmonic frequency, inclusive. The calculations were performed by numerically integrating the equations of motion of typical electrons entering the tube at equal intervals of initial phase. Most of the numerical work was done with IBM equipment, some with desk calculators, and in one case, on the Bell Laboratories relay computer. The results are presented almost entirely graphically, and the reader is referred to figures in main body of the paper for quantitative information.