Improved numerical technique for oscillator frequency stability analysis

Introduces a statistical quantity, termed the extended Hadamard variance, for the spectral analysis of the frequency fluctuations nu (t) of an oscillator. The samples of the time series nu (t) are the gated averages nu _tau or counts of a digital frequency counter spaced by the dead time tau _d. The analysis technique and the numerical algorithm combine the flexibility of the extended two-sample variance with a much higher resolution spectral analysis capability, as shown by experimental results. The limitations are also indicated.