Keysight N9923A, User Manual, Page: 190 / 276

190 Keysight N9923-90001 User’s Guide
Data Analysis Features
All about Trace Math
—
Data / Memory
[
D/M
] Current measurement data is
divided
by the
data in memory.
—
Math Off [ Data ] Displays trace data with NO math applied.
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). The relative significance is shown in
Data-Mem
.
Values to compare Data/Mem Data-Mem
0.5 dB and 0.6 dB 0.1 dB –39 dB
0.5 dB and 0.7 dB 0.2 dB –33 dB
Values to compare Data/Mem Data-Mem
–10 dB and –12 dB 2 dB –24 dB
–50 dB and –52 dB 2 dB –64 dB