The magnitude of the locking signal for backward-wave oscillators

A knowledge of the magnitude of the smallest signal which will lock the phase of a backward-wave oscillator is of importance in the design of multiple slow-wave structures. The paper obtains an estimate of this magnitude using linear theory. The results are shown to be in satisfactory accord with experiments carried out on a helix-type backward-wave oscillator. The method permits the estimation of the minimum locking signal with an accuracy better than ±2dB.