Simulation of noise-power ratio with the large-signal code CHRISTINE

Noise-power ratio (NPR) is a criterion for evaluating the performance of amplifiers and other nonlinear circuits with regard to intermodulation distortion. Traveling-wave tubes (TWTs) are used as amplifiers in telecommunications, and NPR is one of the specifications to be met when building a particular device. Because NPR is measured after a device is built, the meeting of a particular NPR specification may require several build-test cycles. Large-signal, multi-frequency numerical codes to simulate TWT amplifiers, such as CHRISTINE, have the potential to simulate NPR measurements, and thus shorten the design phase of a TWT by reducing, or eliminating altogether, the several build-test cycles required to meet a particular NPR specification. Here we present simulations of the NPR for a helix traveling-wave tube (TWT), performed with the large-signal, l-D, multi-frequency code CHRISTINE, and a comparison with experiment. The results indicate that NPR simulations with large-signal codes have the potential to shorten the design phase of TWTs by eliminating the need for repeated build-test cycles to meet a required NPR.