Ku band, 100 kW traveling wave tube based on large quasi-optical spatial power combining array

Abstract

We report here further development of the novel quasi-optical spatial power combining array for high power millimeter wave (MMW) traveling wave tubes (TWTs) by demonstrating a Ku-band high power TWT which covers 12-15 GHz and with 100 kilowatt (kW) output power. Specifically, a Ku-band high power TWT which consists of a quasi-optical spatial power combining array of fifteen beam-wave interaction circuit slow wave structures and, as a result, beam width/height aspect ratio of close to 85 was developed to achieve a combined output power of over 100 kW at Ku-band. The 15 individual beam-wave interaction structures in the quasi-optical spatial power combining array are arranged into a linear array. Instead of a single cathode, fifteen cathodes, each with its own focus electrode or, in other words, a total of 15 focus electrodes are also used to create a required large sheet of beam for the large quasi-optical spatial power combining array of 15 channels of individual beam-wave interaction structure. Although a single stage collector was initially designed, however, a multi-stage depressed collector will also be designed and implemented to improve the efficiency of this K-band high power TWT. The overall size of the Ku-band high power TWT is relatively small since the same vacuum envelope and electron beam focus optics are shared among the five beam-wave interaction structures. Design and fabrication of this Ku-band high power TWT will be presented to demonstrate the large quasi optical spatial power combining array for very high power MMW TWTs and with reasonable broad bandwidth.