From history to future of satellite TWT amplifiers

Since the invention of the travelling wave tube principle by Kompfner [1] i n 1943 the TWT technology has changed dramatically, altering almost each de vice component except their basic principles as the synchronous electron be am / RF wave interaction, or thermionic cathode emission itself. The past a lmost six decades of helix TWT development resulted in an increase in the o verall DC to RF conversion efficiency from about 1 % (including solenoid po wer) to today's 73 %, with the future potential to approach 75 % or even 80 % for commercial satellite communication applications. These achievements were driven by the never ending demand of commercial geo-stationary satelli te systems to save DC power for the possibility to install more channels wi th higher RF power. This capability of helix TWT's in combination with thei r large bandwidth, high reliability and long life made the helix TWT an ide al microwave power amplifier on board of all types of inherently power limi ted satellites. The paper describes the major lines of this development pro cess, indicates future trends and tries to identify their potentials.