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PDA
Item
REAL
TRACE LABEL
The PDA command loads the destination trace according to the pattern of amplitude values in the source trace.
Thus, the destination trace represents the amplitude probability function of the source trace.
The assumption is that the source trace is taken from the display. Hence, the values of the source trace are in dBm
(or dBmV or dBpV) when the display is in the log mode, or in display units when the display is in the linear mode.
The resolution parameter determines how the screen is divided vertically to create the probability function.
If the display is in the 10 dB/div log mode and the resolution parameter is specified as 5, then the screen is divided
into twenty 5-dB increments. Each value of the source trace is tested in turn and the appropriate element of the
destination trace is incremented by one. For example, if the first point of the source trace is 12 dB below the
reference level (and thus falls in the eighteenth 5-dB increment from the bottom of the screen), then the 18th
element of the destination trace is incremented. Note that the destination trace must have an appropriate number
of points (in this case, 20).
If the display mode is linear, then the resolution parameter divides the screen into increments that are a percentage
of the total number of display units within the graticule (1000). For example, if the resolution parameter is 5, the
screen is divided into twenty 50-display-unit increments (5% of 1000 is 50). Otherwise, the procedure is the same
as above.
The data need not be taken from the screen. PDA can be used on an array of calculated data. However, the
resolution parameter must be chosen as if the data were in display units. For example, if the array values vary from
0 to 200, and you want to divide it into twenty increments (1 - 10,
parameter must be 1.0 (1.0% of 1000 is 10).
Description/Default
Default is dBm.
Alpha character. User-defined label declared in
TRDEF statement.
Probability Distribution in Amplitude
RESOLUTION
- S O U R C E --\
Range Restriction
11
PDA
I
Programming 287
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