Single-transit, large radius E-type devices

A small-signal analysis of E-type traveling-wave devices is presented for systems in which a ribbon-shaped electron beam completes a single excursion through the interaction space of a coaxial-cylindrical structure. The incremental propagation constants and the associated forward-wave growing- and beating-wave gain, as well as the backward-wave start-oscillation conditions, are examined over a wide range of operating conditions. The results point to an interaction-principle that specifies the manner in which the rate of change of energy transfer between the electron beam and the RF wave is affected by the curvature of the path. The origins of slipping-stream motion are examined and an approximate method of computing gain under these circumstances is presented. In addition, predictions based on a small-signal study reveal that E- and O-type devices possess comparable efficiencies. Experimental data on a C-band E-type amplifier are presented a in support of the theoretical predictions.