190 Keysig ht N9923-90001 User’s GuideData Analysis FeaturesAll about Trace Math—Data / Memory [D/M] Current measurement data is d ivided by thedata in memory.—Math Off [Data] Displays trace data with NO math applied.About Math OperationsData / Memory and Data - Memory math operations are performed oncomplex linear data before it is formatted. Because data is often viewed in logformat, 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 comparingtraces “before” and “after” a change is made or when measuring trace noise. Inthe following table, the Data/Mem values intuitively show the differencesbetween traces. It is not obvious what Data-Mem is displaying.Use Data - Memory to show the relative differences between two signals. Usefor 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 thesame 2 dB difference. However, the second pair of connectors have muchbetter S11 performance (–50 and –52). The relative significance is shown inData-Mem.Values to compare Data/Mem Data-Mem0.5 dB and 0.6 dB 0.1 dB –39 dB0.5 dB and 0.7 dB 0.2 dB –33 dBValues to compare Data/Mem Data-Mem–10 dB and –12 dB 2 dB –24 dB–50 dB and –52 dB 2 dB –64 dB
