A Triple-Power-Mode Advanced 11-GHz TWT

Described is an advanced-performance 11-GHz TWT, developed by THOMSON-CSF for INTELSAT. Intended for future communication-satellite programs, this TWT is based on an existing space-qualified tube (a 20-watt/11-GHz model), but has been designed for operation at three different power levels: 20, 8 and 4 watts. Among the numerous performance improvements made are 25% lower phase shift, a reduction in the AM/PM transfer coefficient, and a 40% reduction in the tube weight. Extensive use of CAD has been made in designing this new tube. Detailed experimental results are presented, both for the tube and for an engineering model TWT amplifier, including a high-efficiency power supply also developed by THOMSON-CSF.