A Linearized L-Band 200 Watt TWT Amplifier for Multicarrier Operation

In communication satellite transponders for mobile users, very powerful transmitters with multicarrier (linear) operation capability and high RF to DC efficiency are demanded. The travelling wave tube amplifier (TWTA) is the best candidate for high efficiency, but the linearity has to be improved by using a predistortion linearizer. The diode-bridge type linearizer followed by a limiter is the optimum approach in terms of linearization effectiveness close to saturation, stable operation in satellite environment, simple construction and high reliability. Designing and using such a linearizer with a high efficiency TWT especially developed by AEG, the achieved linearization is close to the calculated for the "ideal" case. Just the limiter by itself improves the multicarrier behaviour of the TWTA close to saturation. Considering all the experience obtained by the work to be described, a proposal for a multicarrier transmitter is made finally which copes with most of the demands of present and future mobile satellite communication systems.