Travelling-Wave Tubes for Space Application: Present and Future

Traveling wave tube amplifiers (TWTAs) and solid-state power amplifiers (SSPAs) are the two main RF amplifiers for onboard communications satellites. In fact, TWTAs are the first successful RF power amplifier technology for communication systems since the birth of space age and covers ~ 60% global market among vacuum tubes for various applications. Both uplinked and downlink signals experience substantial losses and hence must be suitably amplified. However, demand for high power, high frequency, wideband, high efficiency and with the advancements technology such as linearization, miniaturization, weight reduction, etc, makes TWTAs superior compare to SSPAs and also in the family of vacuum microwave devices and resulting TWTAs as the best choice and no other amplifiers can give similar performance. With advancement of state-of-the-art TWTs for space communication, for instance, wideband, high power, gain efficiency, reliability, light weight etc make realization of space TWT more and more complex and challenging. However, many of the older version of TWTs have been replaced by its counterpart, SSPA, in L, S, C and X bands where both power and bandwidth requirements were limited. In present generation of TWTs, C, X, Ku and Ka band TWTs are being used with wideband width and much higher performances where SSPAs cannot rival. In addition to that, with the agility of wideband, high frequency, much higher performance in a single device for next generation realization of space TWTs in above band including W band and so on becoming a challenge to designers. This paper, presents the state-of-the-art space TWTs for present and future communication satellites.