Intermodulation Study.

Methods for reducing capture effects and intermodulation distortion in broadband traveling-wave tubes have been investigated theorteically and experimentally. Considered were primarily techniques that involve interaction of electron beam and slow wave circuit both at the fundamental and at the harmonic frequency range. It was found that significant improvements in tube linearity can be achieved when such a tube is simultaneously driven by the fundamental frequency signals as well as by their first harmonics. hen amplitude and phase of the injected harmonic signals is optimized at saturation, suprious harmonic output power is reduced by more than 10 dB, while fundamental output power and efficiency is about doubled. In multi-tone operation third order intermodulation is then improved by about 6 dB to 8 dB. For broadband applications, the required harmonic signals can conveniently be generated by a wideband driver TWT that is operated in its non-linear range. The design of a driver and output tube chain is described that utilizes harmonic injection over a large frequency range. The tube chain is designed to produce gain and power over a nearly two-octave bandwidth with harmonic injection improvements available over the lower half of the total frequency range. Author