INVESTIGATION OF THE GAIN OF TWT CLOSE TO THE PASSBAND LIMIT USING THE THEORY OF EXCITATION OF PERIODIC STRUCTURES.

Using the excitation theory the gain of a TWT with a slow-wave structure having positive and negative dispersion is analyzed. It is shown that in the first case interference of the electron waves strongly affects gain so that in the immediate vicinity of the passband there is no gain of the direct wave. In structures with negative dispersion, gain increases when the limit is approached. It is shown that the use of the approximation of one increasing electron wave close to the limit of the passband of a structure with negative dispersion involves a considerable quantitative error, and for structures with positive dispersion such approximation involves essential qualitative error.