13.07.2015 Views

NIST Technical Note 1337: Characterization of Clocks and Oscillators

NIST Technical Note 1337: Characterization of Clocks and Oscillators

NIST Technical Note 1337: Characterization of Clocks and Oscillators

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242 A. L. LANCE, W. D. SEAL, AND F. LABAARThe instantaneous phase 4>(e) <strong>of</strong> V(e) for the noisy signal is4>(t) = 2nvot + 4>(t), (6)where 1>(e) is the instantaneous phase fluctuation (lbout the ideal phase2nv o r <strong>of</strong> Eq. (4).The simplified illustration in Fig. 1 shows the sine-wave signal perturbedfor a short instant by noise. In the perturbed area, the .1v <strong>and</strong> .1e relationshipscorrespond to other frequencies, as shown by the dashed-line waveforms.In this sense, frequency variations (phase noise) occur for a giveninstant within the cycle.The instantaneous output voltage V(t) <strong>of</strong> a signal generator or oscillatoris nowV(e) = [Vo + t:(e)] sin[2n1'oe + 4>(t)], (7)where V o <strong>and</strong> 1'0 are the nominal amplitude <strong>and</strong> frequency, respectively, <strong>and</strong>e(t) <strong>and</strong> 4>(t) are the instantaneous amplitude <strong>and</strong> phase fluctuations <strong>of</strong> thesignal.It is assumed in Eq. (7) thatEquation (7) can also be expressed as¢(e)<strong>and</strong> ~ ~ 1 for all (e), ¢(t) = d4>ldt. (8)1'0V(T) = [Vo +

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