Design of a linear C-band helix TWT for digital communications experiments using the CHRISTINE suite of large-signal codes

A set of optimization goal functions designed to improve the efficiency and linearity performance of helix traveling-wave tubes (TWT) is described. These goal functions were implemented in the CHRISTINE suite of large-signal helix TWT codes along with a steepest-descent optimization algorithm to automate the process of circuit parameter variation and to facilitate the rapid exploration of alternative TWT designs. We compare the predicted power, efficiency, and linearity of four different helix TWT circuits, each developed according to a different set of optimization criteria. Out of these designs, a single design was selected to be further developed for use in C-band high-data-rate communications experiments. The detailed design of this linearized TWT with a predicted 1-dB small-signal bandwidth of 1.2 GHz, small-signal centerband gain of 35.7 dB (f_c=5.5 GHz), and centerband saturated output power of 52 dBm (158.5 W) is presented.