Design and development of a 1,250 watt extended KU-band CW forced air-cooled Helix Traveling Wave Tube

Communication and Power Industries (CPI), USA has designed, and developed a 1,250 Watt forced air-cooled high power, high efficiency continuous wave Helix Traveling Wave tube, Model no. VTU6397J2 for Satcom applications. This paper presents the test results of the two initial prototypes produced and tested in an enhanced forced air-cooled cooling system. TWT design includes a coaxial SMA female input cable and WR-75 waveguide output connections. Both prototypes measured over 1,300 watts of average CW output power, over 51 dB of small signal gain across the extended Ku-band from 12.75 GHz through 14.80 GHz. Prototypes demonstrated excellent linearity and third-order intermodulation performances at 4 dB and 7 dB back-offs from rated output power (61.0 dBm). TWT design includes a standard electron Gun assembly with FE turn-on, an isolated anode, a two stage multi-stage depressed collector assembly, and a novel slow wave structure. Test results are in agreement with the design goals and customer specifications. The predicted and measured performance data are compared.