Keysight N9915-90020 User’s Guide 217
SA (Spectrum Analyzer) Mode (Option 233–Mixed Analyzers)FUTURE
SA Mode Settings
Logarithmic X-axis Interpolation (EMI and SA modes Only)
Normally, limit lines are interpolated linearly between the defined limit points
(i.e., as a delta dB per Hz). Sometimes the user may want to change the limit
line interpolation so that it is logarithmic vs. X (i.e., as a delta dB per
log10(Hz)). The “AUTO” state for this control will automatically switch to
logarithmic interpolation, if the Trace is being drawn on a logarithmic
frequency axis (Log Freq Axis X, available by Freq/Dist > More for SA and EMI
modes). The “OFF” state keeps limit line interpolation happening linearly,
regardless of the current choice of logarithmic frequency axisX.
Learn more, see
“How to change from Linear to Log Axis View” on page 153.
How to set Logarithmic X-axis Interpolation (Log Freq AxisX)
1. Press Limit 8
> Options > LogX Interp Auto Off – Enables/disables
logarithmic interpolation of the X–axis (Default == Auto).
2. Then choose from the following:
— Auto – (default) reacts to the trace data. If the you chooses LogX
axis for your trace data, then Auto will cause the interpolation of the
Limit Lines to also act “logarithmically vs. X”. But, for normal Linear
X axis trace data, the interpolation of the limit line remains as
before, straight line interpolation vs. the x axis data.
—
On – forces the limit lines to interpolate logarithmically vs. X.
—
Off – forces the limit lines to interpolate linearly vs. X.
Band/Interval Power Marker
A Band/Interval Power marker—available in IQA and SA Modes—accumulates
the power that is measured over several adjacent data points (or ‘buckets’).
The range of buckets being measured is displayed with vertical posts around
the marker. This Band Span value is selectable.
This feature is very similar to a channel power measurement (
“Channel Power
(CHP)” on page 222
).
When the frequency span is set to Zero span, the marker is referred to as an
Interval Band Marker because it averages power over a specific time interval.
In this case the range is specified as the Interval Span. Learn more about Zero
span measurements in
“Zero Span Measurements” on page 195.
If the Detection method and Averaging type are set to Auto when you enable a
Band/Interval Power marker, the Detection method will change to Average
(RMS) and Averaging type will change to Power average. Other Detection
methods or Averaging type settings will usually cause measurement
inaccuracy. Learn more about Detection method in “Detection Method” on
page 213
, and Averaging Type in “Average Type” on page 204.
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