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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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XI.TRANSLATION FROM FREQUENCY DOMAIN STABILITYMEASUREMENT TO TIME DOMAIN STABILITY MEASURE­MENT ANO VICE-VERSA.ll.l ProcedureKnowing how t.o measure SolI(f) or Sy{f) for apair <strong>of</strong> asci 11 at01's, 1et us see how to trans latethe ~ower-law noise process to a plot <strong>of</strong> a 2 (t).yFirst, convert the spectrum data to Sy(f) , thespectral density Df frequency fluctuations (seesections III <strong>and</strong> VIII).There are two quantities..midl t:DlllPlrtely Sl)ecify S y(f) for a particularpower-law noise precess: (1) the s)ope on alog-log plot for a given range <strong>of</strong> f <strong>and</strong> (2) theFIGURE 10.10 amplitUde. Tile sl~ we shall denote by "or";Figure 10.10 shows the transfoTlll from a Si!lll"" therefore ~ is the straight line (on log-logpled t i me- domainsi gna1 to the f1'til1M!ocy domain. scale) which relat.es S (f) to f. The amplitudey<strong>Note</strong> that in the frequency domain, t1le result is will be denoted "h "; it is simply the coefficientarepetitive in frequency. This effect, CtmIIIonly <strong>of</strong> f fDr a range at f. When we examine a plot <strong>of</strong>called aliasing, is discussed ..arlil~T in sect.iDn spectral density <strong>of</strong> frequency fluctuations, we are10.3. Figure 10.9 <strong>and</strong> figure 10.10 show the sym­ looking at .a representation <strong>of</strong> the addition <strong>of</strong> allmetry between the time- <strong>and</strong> frequency-dmIIain trans­ t.ile power-law pT'l)a5ses (see sec. IX). We haveforms <strong>of</strong> discrete lines.CItC. Discrete fourier transform S (f) =YI:(U.l)Fi na11 y , we have the saJlll'l ed, period; c a=­(assumed) time-domain signal which ;s t.ransformeddomain representation.10.nThis;s shown in figureIn section IX, five power-law noise processesto a discrete <strong>and</strong> repetitive (aliased) frequencyweTeoutlined with respect to SolI(f).ar!! the cDllllllonoscillators.Thes!! fiv!!ones encountered wi th preci s i onEquation (8.1) relates these noiseprocesses to Sy(f). One obtainsFIGURE 10. Uwith respect toSif)1. R<strong>and</strong>om walk FM (f-2. ) II =-2(f_l )2. Flicker fM a =-I3. White fH (1) a = 04. Flicker ~ (f) a = 1S. White~ (fZ) a = 2slop!! onlog-logpaperTable ll.l is a list <strong>of</strong> coefficients fortranslation from a 2(t) to S (f) <strong>and</strong> from S~(f) toy y '"3STN-48

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