SPECTRUM AND PHASE CHARACTERISTICS OF AN (APPARENTLY) BROAD-BAND CONTINUOUS-WAVE MODE-LOCKED OSCILLATOR

We analyze and describe the signal and spectrum of a somewhat idealized regenerative phase swept wide-band oscillator. The signal is consistent with observations reported in several references but has character not previously reported. We find a pulse train with a changing precession (crawl) of phase within the pulses and a sweeping of the spectrum components at a rate determined by the sweeping phase (fixed frequency offset) and loop delay. Precise analysis of the spectrum gives a stationary structure with lines spaced a fraction of the usual longitudinal mode (frequency) spacing if the change in phase shift per pass is a rational fraction of 2-pi. If the change in phase shift is not a rational fraction of 2-pi, the pulsing oscillation does not produce a stationary spectrum. In either case the signal character is not very different from that of a mode-locked oscillator. At least seven parameters are necessary to define the signal, and they all are significant to multiple pulse interferometry. Continuous waves, even continuous spectrum components, are not supported in a phase shifting oscillator. Quantitative relations are derived.