Travelling-Wave Tubes

TRAVELLING-WAVE TUBES B. Higgins Although many electronics engineers are not familiar with their basic operation and applications, travelling-wave tubes (TWTs) are important components used in satellites and other microwave applications. Their use has increased rapidly in line with the widening of the available radio spectrum and the continuing development of satellite communications systems. Recently commissioned medium and high-power TV satellites such as Astra 1A, DFS Kopernikus, TV-SAT2, TDF-1 all use high-performance TWTs to provide television pictures around the clock to millions of viewers. A travelling-wave tube is an electronic amplifier for microwave radio signals. It is not, strictly speaking, a thermionic tube, but rather a complete wideband RF power amplifier in a vacuum envelope. Origin- ally developed in the mid 1940s, TWTs have been improved considerably since then. In particular, their power efficiency has gone up over the years from a modest 10 to 20% to nearly 5...