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

Summary form only given. This research experimentally examines the harmonics and intermodulation products inherent when amplifying multiple frequency signals in traveling wave tubes (TWTs). Laboratory measurements of these phenomena in several TWTs are compared to predictions from computer simulation codes. To date, this research has primarily focused on the empirical characterization of commercially relevant broadband TWTs. Standard commercial tubes are used, as well as a custom-modified research device, jointly designed by UW and Northrop-Grumman investigators. This modified TWT 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. The steady-state and transient output spectra are recorded from the linear gain region well into saturation, and the spectral purity of the outputs are compared. The device gain versus frequency and input power level are presented for single-toned and multi-toned signals.