Development of high power Ka-band and Q-band helix-TWTs

Boeing EDD continues to make advances in its millimeter-wave helix-TWTs by pushing the CW output power capability and increasing the overall efficiency of Ka-band and Q-band devices for communications. The 8921HP, EDD´s latest high power Ka-band TWT model, demonstrates 250 W to 300 W CW output power and 47 % minimum overall efficiency with a two-stage collector over 27.5 GHz-31 GHz. In Q-band, the 8925HP, derived from the current production 120 W Q-Band helix-TWT (8905HP), significantly extends the CW output power capability demonstrating 230 W minimum over 43.5 GHz-45.5 GHz. The beam focusing is improved in both the Ka-band and the Q-band TWT models, with RF beam interception well below 1% of the nominal beam current of 95 mA. The above devices are primarily designed for CW operation but can also be operated in pulsed mode by using the focus electrode to cut-off the beam. The electron gun typically requires a focus electrode voltage of -800 V with respect to the cathode for beam cut-off.