Sectored-beam multi-signal TWT analysis

Harmonic-signal interference is known to degrade the performance of wideband TWTs (traveling wave tubes). When harmonic frequencies occur in the neighborhood of intersection points among spatial harmonics of forward and backward waves of the slow-wave circuit, the deterioration in fundamental power and efficiency can be strongly accentuated. To model this multisignal problem, a recast large-signal analysis of traveling-wave interaction involving simultaneous forward and backward waves at frequency harmonics of the fundamental signal has been developed from an existing one-dimensional disk model. Coupling to the beam among the spatial harmonics differing in their azimuthal index values is accomplished by partitioning the solid (or annular) beam into constrained sectors (azimuthally and radially), equally spaced initially over the fundamental RF period. A computer code based on this upgraded formulation has confirmed the importance of the backward wave in the stop-band-related power absorption phenomenon in TWTs.<>