Traveling-wave Tube Harmonic Injection Technology Research

TWT is widely used in the secondary planet, electron war, spaceflight and radar systems because of high power and high frequency. It magnify the high frequency signals through electromagnetic wave and electron/wave interaction and get power from electron. The electron/wave interaction in TWT is nonlinear process in nature, it will lead nonlinear distrortion of input signal, so the output signals include the input signals and the harmonic signals and the intermodulation signals.In order to compress the second harmonic and the third-order intermodulation, and improve the linear, harmonic injection is come up in twenty century 70s, but get detailed investigation recently along with the widely used computer simulation. Harmonic injection is a very important method for improving the nonlinear nature of TWT, launching the fundamental signal with the injected signal which is second harmonic with proper power and phase, the method is an ideal solution for suppress the harmonic and cross-modulation signals inspired by nonlinear distoration.The main contents of this dissertation is as follows:1. TWT-1D and TWT-3D models have been analysed systemly based on the TWT interaction theory.2. The compression for second harmonic after injection is simulated use TWT-3D model. the result show that harmonic injection can suppress the harmonic signals at best 20dB, the best second harmonic input power and phase can improve the output power of basic tone, reduce the output power of second harmonic and extend the bandwidth of TWT at low frequency.3. The compression for third-order intermodulation after injection is simulated use TWT-3D model. the result show that harmonic injection can suppress the third-order intermodulation at best 40dB.4. The experimentation of harmonic injection contrast with simulation, they both proved the same viewpoint.