44 GHz Helix TWTs for satellite communication systems

Varian has developed a 25 W CW, PPM focused TWT which operates at 44 GHz for use in satellite communication systems. The design concept is based on refining fabrication procedures and technology used on lower frequency, high production TWTs. A conventional fabrication technique has been used consisting of a tungsten helix supported by APBN rods, which is interference fitted in an integral polepiece body. The bundle assembly, lapping and inspection fixtures have been refined to accurately size the bundle. The helix bundle is cold stuffed in the body using specially designed fixtures. The helix is matched on both the input and output to narrow-height WR22 waveguide. A thick, ceramic-disc beryllia window design is used. A special PPM design is required to compensate for the missing magnet in the match cells. Beam transmission is 97% or better.