Recent advances with high-power PPM-focused dual mode TWT's

The objectives of this development were to improve the average power capability, gain and efficiency of a predecessor PPM-focused dual mode TWT described in 1975(1). The circuit for the new tube is also of the coupled-cavity type with a center frequency of 9.5 GHz. The new circuit is liquid cooled and provides 500 watts average output power in the high mode with 11 kW peak power and 54 dB gain. In the low mode the average output power is 700 watts with 1.4 kW peak power stud 29 dB gain. The basic efficiency without collector depression is 15 percent in the high mode and 8 percent in the low mode. Overall efficiencies increase to 36 percent and 24 percent in high and low modes with a two-stage collector depressed to 60 and 80 percent of cathode voltage. The collector designed for this tube employs a novel arrangement of collinear hyperbolic elements, displaced to one side of the tube axis. Allowing for beam interception stud rf circuit losses, the implied collector efficiencies range from 75 to 83 percent.