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IEEE Standard 1139 is the standard for
characterizing measurements of frequency, phase, and amplitude
instabilities. The standard measure
for characterizing phase and frequency instabilities in the frequency domain is
L(f), defined as one half of the double-sideband spectral density of
phase fluctuations. When expressed in
decibels, the units of L(f) are dBc/Hz (dB below the carrier in a 1 Hz
bandwidth). A device is to be
characterized by a plot of L(f) versus offset frequency f. In some applications, providing L(f)
versus discrete values of offset frequency is sufficient.
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The standard measure for characterizing
amplitude instability in the frequency domain is one half of the
double-sideband spectral density of the fractional amplitude fluctuations,
1/2 Sa(f). When expressed in decibels, the units of Sa(f)
are dBc/Hz.
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In the time domain, the standard measure of
frequency and phase instabilities is the fully overlapped Allan deviation y() - see the next
few pages. A device shall be
characterized by a plot of y() versus sampling time . In some
cases, providing discrete values of y() versus is sufficient. The measurement system bandwidth and the
total measurement time shall be indicated.
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IEEE Standard
1139-1999
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Characterization
of Clocks and Oscillators, edited by D. B. Sullivan, et al., NIST
Technical Note 1337, March 1990. Time
& Frequency Div., NIST, 325
Broadway, Boulder, CO 80303.
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S. R. Stein,
"Frequency and Time - Their Measurement and Characterization," in
E. A. Gerber and A. Ballato, Precision Frequency Control, Vol. 2, pp.
191-232, Academic Press, 1985
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