Characterization of Frequency Fluctuations by Crosscorrelations and by Using Three or More Oscillators

Abstract

Summary The individual stability of an oscillator can be reached by using two auxiliary oscillators and comparing the three oscillators twotwo. The direct application of this principle gives erroneous results if the three comparisons are not made simultaneously. However the results are affected by the measurement system noises. New methods are proposed for comparing three oscillators. They use the concepts of crossvariance and crosscorrelation. They enable to characterize individually the oscillators and they reduce the influence of spurious noise sources, when uncorrelated. Therefore better resolution can be achieved in the frequency or phase fluctuation measurements.