General design procedure for high-efficiency helix-type traveling-wave amplifiers

Heretofore traveling-wave tubes have been designed using Pierce´s small signal theory, and the design then modified according to previously obtained experimental results in order to achieve high saturation output and a reasonable efficiency. A procedure has been developed that makes use of the large-signal calculations on traveling-wave amplifiers to design tubes to operate at high saturution efficiency. The design procedure is particularly useful in the design of tubes for high power output and may be applied to the design of either cw or pulsed tubes. A procedure has been developed which enables the design of a traveling-wave tube to be completed with the use of a minimum number of curves and requires a minimum of calculation on the part of the designer. The design curves for helix-type tubes were calculated using the sheath helix impedance modified by the appropriate impedance reduction factors.