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S T A B L E 3 2
Control
Type
U S E R
M A N U A L
Description
Sine Period
Edit
Enter period of sinusoidal term
OK
Pushbutton
Perform the Noise function & close dialog box.
Cancel
Pushbutton
Abort the Noise function & close dialog box.
Copy
Pushbutton
Copy the noise parameters to the clipboard.
Help
Pushbutton
Invoke this help topic.
Operation
•
Enter the Number of data points wanted and their Tau interval. Then enter the σ(1) Noise
Parameters for the desired power law clock noise. At least one noise parameter must be nonzero. Next enter any fractional frequency Offset and Drift, and/or the peak value and Period
of any Sine term, that may be wanted. Then press OK to generate the simulated clock noise,
or Cancel to abort.
•
F FM Noise Generation
The long-term phase excursions of the generated flicker FM noise are too small on average
(see Reference 2 below). This does not affect the Allan deviation results, and can be avoided
by generating twice as many points as needed and using only the second half of the output.
•
FW FM and RR FM Noise Generation
The more divergent flicker walk FM (a=-3) and random run FM (a=-4) power law noise types
may be generated by using the 1/f² spectral property of a frequency to phase conversion. For
example, to generate RR FM noise, first generate a set of RW FM noise and save the resulting
phase data. Then read this RW FM phase data as frequency data and convert it to a new set of
RR FM phase data.
•
Sine Generation
The Sine (peak) and Sine Period controls allow entry of the fractional frequency amplitude
and period (seconds) of a sinusoidal component to be added to the simulated noise. A finite
amount of noise must still be included (to avoid zero sigma). These parameters are useful for
simulating the effect of a periodic disturbance such as temperature or vibration. The phasing
is that of a positive sinusoid on the fractional frequency data. No sinusoidal component is
added unless both the peak value and period are non-zero.
•
Memory Usage
Noise generation is a memory-intensive process that requires about 48 bytes of peak memory
usage per data point. Large data sets can therefore involve relatively slow virtual (hard drive
swap) memory.
•
Caution
The results from the Noise function overwrite the current data in the phase and frequency
arrays.
•
Example
An example of the frequency stability of simulated data with a combination of white PM noise
and a sinusoidal term is shown below:
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