Agilent Technologies Signal Analyzer N9030a - Manual (Page 1456)

6 RLC Swept SA Measurement Front-Panel & SCPI Reference
View/Display
put into Display Trace 1, and all the other traces “roll up.” Once the trace data has been written
into the spectrogram, it is immutable.
Although all 6 traces can be used in the trace window, it is the data from the “live” Trace 1 that
goes into Display Trace 0 and then into the spectrogram window. Thus, the spectrogram
represents the history of Trace 1; traces 2–6, although available, are not written into the
spectrogram. As you change the value of Display Trace, you see the historical data only in Trace
1; Traces 2–6 still represent live data.
The display can only hold 300 traces. The oldest trace is Display Trace 300, and it is always the
topmost trace in the bottom window. (If the Spectrogram window has not yet filled with 300
traces, the oldest trace is the highest numbered trace that has data in it). The value of Display
Trace is annunciated in the upper left hand corner of the bottom window, along with the start
time of that trace.
Any variable change that restarts a sweep will clear out the spectrogram and start it over, unless
you are in the idle state (single sweep or waiting for a trigger), in which case it will be cleared out
when you start sweeping again. The Restart key will clear out all spectrogram traces and start
over. The spectrogram display is also cleared on exit from the Spectrogram View, so every time
you enter the Spectrogram View, the spectrogram window is empty.
The colors in the Spectrogram represent signal amplitude. The key to these colors is displayed
next to the Y Axis in the upper window. By changing the Y Axis parameters you can change the
scaling; that is, by changing the Ref Level or Scale/Div, the colors will get remapped to new
Amplitude values. Note that this will not restart the Spectrogram unless the Attenuation changes.
As this is swept spectrum analysis, each horizontal line in the spectrogram represents a single
trace, and the vertical axis represents time. The user might thus expect each line to slope
upwards from left to right to more correctly represent the point in time at which each point in the
trace was taken. However, the lines are horizontal, so the display represents each trace as
representing a single time, which is in fact its start time. If this distinction is important to you,
you should use FFT sweeps (with an FFT Width greater than your span, of course) to ensure that
each trace point in a line better represents the same moment in time.
If Display Trace=0, the data for Trace 1 is written into the trace as the data is acquired, just as in
Normal View. So you will see the data as it is acquired; for a slow sweep, for example, you will
see the trace fill as the points are taken. For any other value of Display Trace, Trace 1 will
appear static, as it represents an historical trace. As the traces roll up, the value of Display
Trace does not change, so you will see a different trace in Trace 1 every time the live trace
finishes. To freeze the spectrogram, put Trace 1 into View, or put the analyzer into Single sweep
(note that unless the Average/Hold Number=1, putting the analyzer into Single will not freeze the
Spectrogram until the number of traces specified by the Average/Hold Number have been taken).
When returning to the Normal View from the Spectrogram View, Trace 1 will hold whatever data
was in Display Trace 0 on exit.
1456 Remote Language Compatibility Measurement Application Reference