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Phase Noise Floor and Region of Validity
Caution must be exercised when
of the phase fluctuations,
-10 dB/decade line is drawn on the plot for an instantaneous phase deviation
of 0.2 radians integrated over any one decade of offset frequency. At
approximately 0.2 radians, the power in the higher order sidebands of the
phase modulation is still insignificant compared to the power in the first
order sideband which ensures the calculation of
the graph above, below the line, the plot of
L(f)
is increasingly invalid and
S
(f)
noise of the signal. (
φ
L(f)
using the
graph to compute
S
(f) = 2 (L(f)) or S
φ
Agilent Technologies E5500 Phase Noise Measurement System 18-3
Reference Graphs and Tables
Phase Noise Floor and Region of Validity
L(f)
is calculated from the spectral density
S
(f)
because of the small angle criterion. The
φ
L(f)
L(f)
is correct; above the line,
S
(f)
must be used to represent the phase
φ
is valid both above and below the line.) When
S
(f)
, add 3 dB to the Level.
φ
(f)
= L(f)
+ 3 dB
φ
dB
dBc
is still valid. As show in
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