Development of a low voltage power booster TWT for a Q-band MMPM

Compact millimeter wave amplifiers with output powers ranging from around 20 to 100 W are required for a number of important military and commercial applications. This paper describes the design of a miniature, low voltage, vacuum power booster TWT for a Q-band (40-45 GHz) millimeter wave power module (MMPM). At a design voltage of 7.7 kV and a maximum current of 120 mA, an output power goal of greater than 40 W of CW rf output power has been established for the Q-band TWT. Beam confinement is provided using an optimized samarium cobalt PPM stack. Circuit losses at millimeter wavelengths are minimized using a novel wire-wrapped, T-shaped BeO rod support structure. Output power is transmitted through a 0.051 cm, thick alumina ceramic output window. High overall device efficiency is achieved through the use of a 3 stage depressed collector. A recently completed engineering prototype produced 51 W of CW power at 41 GHz. Experimental overall device efficiency was 34.5%. These results will be described, as well as ongoing work to further improve overall device performance.