About Math Operations - Keysight N9923A FieldFox User Manual

About Math Operations

Data / Memory and Data - Memory math operations are performed on complex
linear data before it is formatted. Because data is often viewed in log format, it is not
always clear which of the two math operations should be used. Remember: dividing
linear data is the same as subtracting logarithmic data. The following illustrates, in
general, when to use each operation.
Use Data / Memory for normalization purposes, such as when comparing traces
"before" and "after" a change is made or when measuring trace noise. In the
following table, the Data/Mem values intuitively show the differences between
traces. It is not obvious what Data-Mem is displaying.
Use Data - Memory to show the relative differences between two signals. Use for
comparison of very small signals, such as the S11 match of two connectors.
In the following table, Data/Mem shows both pairs of connectors to have the same 2
dB difference. However, the second pair of connectors have much better S11
performance (–50 and –52) and the relative significance is shown in the Data-Mem
values.
Data Analysis Features
Values to compare
0.5 dB and 0.6 dB
0.5 dB and 0.7 dB
Values to compare
–10 dB and –12 dB
–50 dB and –52 dB
Data/Mem Data-Mem
0.1 dB –39 dB
0.2 dB –33 dB
Data/Mem Data-Mem
2 dB –24 dB
2 dB –64 dB
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