
Table 4-3 shows the relationship of L(f) to Allan Variance for a power
low-noise process. Using this table, an estimate of <7
y
(r) can be made
directly from a phase noise plot.
Table 4-3. Relation of Z(j) to Allan Variance
White Phase
Flicker Phase
White
Freq.
Flicker
Freq.
Random Walk
Freq.
Slope of £(f)
(dB/decade)
0
-10
-20
-30
-40
<Ty{T) =
y/L{f)U „-l
2.565i/„
r
dttf)f (2.184+ en(J
h
r)) _
i
2.565^
r
1.665v/£(/)/^
o
v
0
<S
0
r =measurement time, y = Az//V
0
, v
0
= carrier frequency, / = modulation rate
or offset frequency, f
h
= measurement system bandwidth, y = ~-i/„
NOTE
Frequency fh is specified as the measurement system
bandwidth to minimize computation time. You may wish
to determine the smallest f^ for a given r that will provide
accurate results.
reu.05SEP89
Sigma vs. Tau 4-13
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