Backward-Wave Oscillators

TLDR

The Pierce traveling‑wave tube theory was adapted to model backward‑wave oscillators, yielding theoretical relationships for starting current, frequency, and efficiency as functions of space charge and circuit loss. Experiments on two tubes, one adjustable in length, confirmed the theory and revealed phenomena such as pushing/pulling, stability limits, frequency gaps, spurious oscillations, and a low‑voltage oscillation deficit attributed to velocity‑distribution effects.

Abstract

The Pierce traveling-wave tube theory is modified to apply to the backward-wave oscillator. Theoretical dependence of both starting current and frequency upon space charge and circuit loss is calculated, as is the dependence of efficiency upon these parameters. Good experimental confirmation is obtained with two tubes, one of which was of adjustable length. Pushing, pulling, stability, frequency gaps, and spurious oscillations are described and explained. Lack of oscillation at low-voltage end of tuning range of some tubes is tentatively assigned to a velocity-distribution effect.