Oscillator performance from the time evolution of relative phase

Abstract

An improved method is described for simultaneously evaluating the fractional frequency stability and phase noise spectrum of ultrastable microwave oscillators from a digitised recording of a zero Hertz beat waveform between two such oscillators. To illustrate the new technique results are presented from a study of two ultrastable cryogenic sapphire oscillators which have a fractional frequency stability near 10-15 at 1s integration time.