Theory of the Beam-Type Traveling-Wave Tube

The small-signal theory of the beam traveling-wave tube has been worked out. The equations predict three forward waves, one increasing and two attenuated, and one backward wave which is little affected by the electron stream. The waves are partly electromagnetic and partly disturbance in the electron stream. The dependence of the wave propagation coefficients on voltage, current, circuit loss, and the other properties of the transmission mode which propagates energy and the cut-off transmission modes is given. Expressions for gain and noise figure and an estimate of power output are given. Appendix A gives an expression for the field in a uniform transmission system due to impressed current (as, of an electron stream) in terms of the parameters of the transmission modes. Appendix B calculates the propagation constant and the field for unit power flow for the gravest mode of a helical transmission system.