233 GHz high Power amplifier development at Northrop Grumman

Northrop Grumman has developed a folded-waveguide vacuum electronic high power amplifier at 233 GHz. The amplifier demonstrates output power over 79 W (49 dBm) from 232.6-234.6 GHz, and greater than 50 W (47 dBm) over a 2.4 GHz instantaneous bandwidth. Saturated gain is approximately 23-24 dBm over this bandwidth, with an input drive of 26-27 dBm required for saturated output power. The device operating point is 20.95kV, 114mA for a frequency range centered at 233.6 GHz, but is capable of producing 50W at frequencies up to 237.8 GHz by varying the operating voltage. Typical instantaneous (3 dB) operating bandwidth ranges from 2.4-3.0 GHz for a beam voltage range of 20.5-21 kV. The amplifier uses a compact permanent magnet solenoid for beam focusing and confinement, and typically achieves 95-98% beam transmission through the folded-waveguide circuit and into the single-section depressed collector. This device has demonstrated operational duty cycles up to 50% with liquid cooling and using Northrop Grumman's Microwave Power Module compact integrated power conditioner technology. A more compact version of this power amplifier is being developed with emphasis on reducing the size of the permanent magnet solenoid.