Design and calculation procedures for low-noise traveling-wave tubes

A step-by-step procedure for designing low-noise traveling-wave tubes is presented in this paper. The procedure permits the rapid calculation of the significant design parameters corresponding to the conditions for minimum noise figure. The procedure includes the use of a special transmission-line type chart which facilitates the calculations and aids in understanding the principles involved in achieving low-noise behavior. By using the chart in connection with a second procedure, noise figure variation with frequency and with the tube parameters can be predicted for arbitrary electron gun design. Measured noise figures for two X-band low-noise tubes designed essentially by these procedures agree with the theoretically predicted noise figures to within 1.5 db.