TWTA are an enabling technology that supports future generations of bandwidth efficient military satellite communications. Advanced twtas will allow new communication satellite mission capabilities for bandwidth efficient modulation waveforms. The objective of this topic is to support the development of advanced compact linearity efficient twtas. Goals include high direct current to radio frequency (dc-rf) efficiency, size and weight reductions, enhanced reliability, improved linearization/modulation latitude, and broad bandwidth. TWTA includes TWT, high voltage power supply (hvps) and linearizer. TWTA goals include output average power > 50 watts, output frequency 43.5 to 45.5 ghz, efficiency > 30%, weight < 15 lbs, size < .5 cu. ft. in air cooled, weather resistant package suitable for antenna mounting. Linearity consistent with capability to support quadrature amplitude modulation (qam) with a goal of amplitude modulation/phase modulation (am/pm) less than 4.5 degrees/db from small signal up to saturated input power, across the band. Innovative approaches are needed to achieve linear efficient power for bandwidth efficient modulation schemes such as qam. The use of innovative interaction circuits, dynamic voltage control, external linearizers, or other innovative techniques are needed to increase linearity when using qam modulation which requires operation over a high peak to average power ratio (3 to 6 db). The initial phase of the program calls for concept design of a linear efficient twta and the demonstration of concepts to be used to miniaturize critical twta components.