Development of Ka-band 250 W peak power helix TWT

Summary form only given. This paper describes the development of a Ka-band 250 W peak power helix traveling wave tube (TWT) for the gateway terminal of the next-generation Internet satellite communication system. NEC started the development of Ka-band microwave tubes for Japanese CS satellite programs in the early 1970´s. Since then, the Ka-band microwave tubes development efforts has been carried out in order to achieve high performance, high reliability and cost reduction, and NEC developed the 100 W helix TWT in 1985 and the 150 W helix TWT in 1996. This time, we developed a new type of highly linear Ka-band TWT based on the many past experiences. The feature of this TWT is high output power more than 250 W (RF pulse) to achieve low distortion at the actual operating continuous output power level and high efficiency of 48% over 27.5-30.0 GHz. Although the output power of the conventional TWT for the satellite communication has usually specified only the continuous output power, this TWT has realized high continuous output power more than 150 W (-2.2 dB output back off) and RF pulse saturated output power more than 250 W, and low distortion at the actual operating continuous output power level. Moreover, such a high output power as 250 W was obtained in the same package size as the conventional TWT by improving the efficiency and decreasing the DC power consumption.