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PDA Probability Distribution of Amplitude
Example
OUTPUT
718;"IP;SNGLS;"
OUTPUT
718;"VB
1OKHZ;HD;TS;"
OUTPUT
718;"MOV
TRB,O;"
OUTPUT
718;"PDA
TRB,TRA,l;"
OUTPUT
718;"MPY
TRB,TRB,S;"
OUTPUT
718;"VIEW
TRB;"
Description
Initializes spectrum analyzer and activates the
single-
sweep
m4de.
Changes
video
bandwidth,
updates
trace.
&places trace B data with all zeros.
Determines
the distribution
of
trace A and sums results
into
trace
B
Multiplies values in trace B by 5 to
make
the results more
visible.
Displays the result.
The PDA
command takes the data in the source trace on a point-by-point basis. Each amplitude
value is divided by 100 times resolution value, and the result of the division is rounded to an
integer. If the result falls within the range of the buckets of the destination trace, the content
of the corresponding destination trace element is increased by one. For example, to show the
distribution of amplitudes on a trace with values ranging from 0 to 8000, a resolution value of
1
dB
would result in 81 buckets
((SOOO/(l
x
lOO))+
1). Amplitude values ranging from 0 to 99
would go to bucket 1, values from 100 to 199 would go into bucket 2, and so forth. Finally,
values from 7900 to 7999 would go to bucket 400. An amplitude value of 8000 would fall into
bucket 81.
Due to the summing nature of the PDA command, the destination trace should always be
initialized to all zeros.
The PDA function is similar to the probability density function in statistics. The probability
density function has the y-axis as the probability of an occurrence, where the PDA function of
the HP 8590 Series spectrum analyzer has the number of occurrences as its y-axis. The PDA
could be converted to a probability density function by dividing, in an external controller, the
value of each bucket by the total number of source elements. Note that performing the divide
inside the spectrum analyzer would not be appropriate because the result is less than 1, which
would be truncated to 0.
Programming Commands 5-421