The effect of circuit tapering on the efficiency bandwidth characteristics of dispersive traveling-wave tubes

The dispersive characteristics of the loaded-waveguide type interaction structures commonly employed in high-power traveling-wave tubes cause a large variation of efficiency with frequency. This efficiency variation can be reduced by period tapering of the output section of the tube. The physical reasons underlying the improvement in tube performance, calculated results using large-signal traveling-wave tube equations and experimental confirmation of the calculations are described.