Agilent Technologies Signal Analyzer N9030a - Manual (Page 1151)

6 RLC Swept SA Measurement Front-Panel & SCPI Reference
SPAN X Scale
If the signal is lost, an attempt will be made to find it again and continue tracking. If there are
other signals on screen that are near the same amplitude, one of them may be found instead since
the algorithm is seeking a signal with amplitude similar to the amplitude of the original signal.
Signals near 0 Hz cannot be tracked effectively as they cannot be distinguished from the LO feed-
through, which is excluded by intent from the search algorithm.
As a speed optimization, the center frequency is only changed if it differs from the marker
position by 1% or more of the span.
If the analyzer is in Single Sweep and Signal Track is turned on, then nothing happens until a
sweep is actually initiated (i.e. by an INIT:IMM or Single key press, and a trigger). Once the sweep
is initiated, the entire set of sweeps necessary to complete a pass through the signal track
algorithm ensues before the analyzer returns *OPC true, returns results to a READ or MEASure, or
returns to the idle state.
If the span is changed while in Signal Track, either by you or because moving the instrument to
the signal’s frequency results in Span Limiting (as described under the Frequency key), an “auto-
zoom” algorithm is executed to get to the new span without losing the signal. In “auto zoom”, the
span is reduced in stages, with a sweep between each stage. You will see this zooming occur as
each sweep is performed, and the new span is set.
When auto-zooming, the set of steps necessary to achieve the target span is to be considered a
“measurement,” thus the entire process executes even if the analyzer is in single sweep. *OPC will
not return true until the process is complete nor will results be returned to a READ or MEASure
command. Note further that if the analyzer is in a measurement such as averaging when this
happens, the act of changing the span restarts averaging but the first average trace is the last
trace of the auto zoom.
When you increase the span, we go directly to the new span. No zooming is required.
This function is intended to track signals with a frequency that is changing (drifting), and an
amplitude that is not changing. It keeps tracking if you are in continuous-sweep mode. If in
single-sweep mode, as described above, the analyzer only does one center frequency adjustment as
necessary.
Remote Language Compatibility Measurement Application Reference 1151