The effect of reflection on the operation of an O-type TWT under two-signal amplification

With multifrequency excitation of an O-type TWT, the presence of external or internal feedback at one of the frequencies being amplified can lead to amplitude and phase changes in all the components of the output spectrum. Reference is made to studies that have examined external feedback in O-type TWTs as a possible method of decreasing nonlinear distortions in multifrequency modes. It is noted that in conventional 'nontransparent' designs of O-type tubes, where reflected waves occur at the ends of the slow-wave structure and at the point where the absorber or slow-wave structure gap is introduced, the feedback circuit encompasses only part of the interaction space. For this reason, the effect of internal feedback on processes of multisignal amplification is seen as meriting further study. Results are presented of an analysis of the interaction of two signals in a wideband O-type TWT in the presence of reflections for one of the signals. Two possibilities of a feedback circuit are considered; one comprises the input of the tube and the beginning of the absorber, the other the end of the absorber and the output of the tube.