An air cooled 200 watt CW TWT at 30.5 GHz with high interaction efficiency

This paper describes a 200 watt CW Ka-band coupled-cavity traveling-wave tube developed for a communication ground terminal application. This tube, designated the 914H, was developed by Hughes Aircraft EDD under a program funded by the United States Army Satellite Command. Art Wachtenheim is the sponsor of the program. The 914H operates over a band of from 30 to 31 GHz with less than 1 dB of gain variation over the entire 1 GHz hot band. A very high basic efficiency of 18% at center band has been achieved. Tube features include air cooling, PPM focusing, mod anode electron gun, depressed collector, and poker chip windows. A unique mechanical configuration in which the magnetic focusing structure is added externally to the vacuum envelope was used to fabricate the RF circuit. Cavity design and circuit configuration were developed by exploiting a number of computer design programs. The circuit configuration is a two-section design.