Linear TWT development

Summary form only given. The digital communication industry requires RF amplifiers that provide constant gain at steadily increasing rated output power levels. One method to obtain linear operation in a traveling wave tube (TWT) is to operate the device well below its saturated power and to use a multi-stage depressed collector for energy recovery. This method, while effective, still has the disadvantage of operating at lower device efficiency than possible near saturation. It is of continuing interest to investigate and develop high power TWT designs with ultra-linear phase and amplitude transfer characteristics. The design of a linear TWT was approached on several fronts. First, simple Pierce theory was used to obtain a baseline design and to investigate many of the tradeoffs between design parameters and the device transfer characteristics. Next, Christine 1D, a 1D large-signal, helix TWT code developed by the Naval Research Laboratory was used to optimize and verify the design. Finally, Christine 3D, a 2 1/2 -dimensional, large-signal, TWT code is to be used to model RF beam expansion and to calculate the spent beam distribution for collector optimization, before the optimized design is built and tested.