TWTA Dominance C-Band Traveling Wave TWTs Versus Sold State Amplifiers
Ernst Bosch, Albert Jaeger, Erwin Seppelfeld, Thomas Monsees, R.A. Nunn · 21st International Communications Satellite Systems Conference and Exhibit · 2003
Recent developments have provided significant advantages for C-Band TWTs over competitive solid state amplifiers for new or replacement satellite communication systems. This advanced TWT design technology optimized over the last several years, and now in production, has served to reestablish the dominance of TWTs over solid state amplifiers. TWTs qualified up to 95°C are commercially available covering the RF output power spectrum in C-Band with efficiency ranging from 65% to 68% in the 20 to 40 watt RF output power class. Higher efficiency 67-69%, and in narrow band 70 % is available for TWTs in the 55 to 120 watt power range using this advanced technology. This demonstrated capability as described in this paper, combined with appropriate linearization techniques provides the preferred means for an overall cost effective and reliable C-Band downlink payload. The enhanced TWT efficiency and reduced mass contribute to minimize satellite launch constraints by enabling the use of reduced battery requirements and related fuel savings. These aforementioned improvements leading to lower overall satellite lift-off weight and lower overall launch costs. This paper will provide a review of the progress made in the progressive enhancement of TWT efficiency while maintaining those functional aspects – phase shift, AM/PM, IMD and NPR – required for overall optimization in conjunction with an associated linearizer to challenge the capability of the solid state amplifier. A comparison will be made in this overall discussion describing the salient details and differences between commercially available TWTAs and competitive SSPAs including electrical performances, mass and environmental requirements. This comparison will serve to enable an unambiguous selection of the dominant C-Band downlink satellite transmitter.