AN279 Silicon_Laboratories, AN279 Datasheet - Page 7

• Manufacturer Part Number: AN279
• Description: Estimating Period Jitter FROM Phase Noise
• Manufacturer: Silicon_Laboratories

A
Spurs that are small and few in number and do not contribute significantly to phase jitter may typically be omitted
from period jitter calculations. This is especially true for low offset frequency spurs. Each significant spur
contribution should be accounted for separately as for the weighted i
Each spur's contributions are then added in sum square fashion as follows:
or:
J
Δ
Δτ
Δt
Δt
PER_TOTAL
ϕ
2
RMS_TOTAL
P P E N D I X
2
RMS_i
2
RMS_i
2
RMS_TOTAL
=
=
(rms)
⎛
⎝
8L f
------
2π
T
0
=
( ) x
=
⎞
⎠
i
2
Δt
Δt
8L f
=
2
RMS_NOISE
2
RMS_NOISE
( )
sin
Δt
i
B —C
sin
2
2
RMS_TOTAL
(
π
2
f
(
i
τ
π
+
)
f
+
i
Δt
τ
i
)
∑
=
N
2
RMS_1
=
1
A L C U L A T I N G W I T H
Δt
2T
----------- - L f
2
RMS_i
π
2
0
+
2
…
( )
+
i
Δt
sin
2
RMS_i
2
(
π
f
i
τ
+
)
…
Rev. 0.1
+
Δt
2
RMS_N
th
spur below:
S
P U R S
I
N C L U D E D
AN279
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