A comparison of two-tone intermodulation experiments with CHRISTINE 1D helix TWT code simulations

CHRISTINE is a 1D nonlinear parametric helix TWT code that can accept multiple-carrier inputs and can accurately simulate the performance of the TWT including the effects of harmonic interaction and intermodulation distortion. To test the multi-frequency capabilities of the code and the accuracy of an improved tape helix model, a series of two-tone experiments was carried out with a Hughes 8537B TWT, a periodic permanent magnet (PPM) focused helix TWT designed to produce a nominal 80-W of saturated output power over a frequency range of 1.530 to 1.548 GHz. The CHRISTINE simulations were also compared with an empirical multi-frequency model based power series fit to a single-carrier gain transfer curve.