Investigations of non-linear spectral behavior in multi-toned helix traveling wave tubes

Summary form only given. This research examines the harmonics and intermodulation products inherent in simultaneous amplification of multiple frequency signals in a traveling wave tube (TWT). Laboratory measurements of these processes in a custom-modified TWT (2-6 GHz) are compared to predictions from computer simulation codes. This experimental TWT, jointly designed by UW and Northrop-Grumman researchers, includes multiple output taps along the helix, providing a unique means to observe the evolution of the RF spectrum at various axial positions, as well as the cold versus beam-loaded dispersion characteristics. Output spectra are recorded from the linear gain region to saturation, and these spectra are compared with model predictions. The device gain versus frequency and input power level will be examined for single- and multi-toned signals. The experimental data will be analyzed by comparison with computer simulations. The insight gained through this research will be applied to suppressing the non-linear signal products generated when amplifying multiple tones in TWTs. Ultimate objectives include realizing improved linearity over a broad instantaneous spectral bandwidth, while maximizing beam-to-RF energy conversion efficiency.