Effects of Multiple Internal Reflections on the Small-Signal Gain and Phase of a TWT

We formulate and solve a set of equations that model the effects of reflections from an arbitrary number of circuit discontinuities in a traveling-wave tube (TWT) operating under small-signal conditions. Applying this model to a case in which the discontinuities represent a series of small random pitch variations due to fabrication errors in a helix TWT, we find that reflections may significantly increase the statistical effects on the gain and output phase first reported in the work of Pengvanich In another example, we report on a study of the effects of many small pitch errors on gain ripple in a 220-GHz folded waveguide TWT.