154 Keysight N9938-90003 User’s Guide
SA (Spectrum Analyzer) Mode (Option 233–Mixed Analyzers)
SA Mode Settings
Noise Marker
For comparison purposes, electronic noise measurements are often displayed
as though the measurement was made in a 1 Hz Res BW. However, making an
actual measurement at a 1 Hz Res BW is extremely slow.
A Noise Marker, unique to SA Mode, mathematically calculates the noise
measurement as though it were made using a 1 Hz bandwidth.
Several data points (or ‘buckets’) are averaged together to calculate the Noise
Marker readout. To accurately measure noise, the Noise Marker should NOT be
placed on, or too close to, a signal. The distance from a signal depends on
several factors. To know if an accurate reading is being made, move the Noise
Marker until consistent measurements are displayed in adjacent data points.
In addition, when a Noise Marker is displayed, the Detection method is
automatically switched to Average and PAvg is shown on the FieldFox screen.
This occurs only when Detector is set to Auto. Learn more in “Detection
Method” on page 151.
With a Noise Marker present, the Res BW can be changed and the displayed
noise floor will also change, but the Noise Marker readout will remain about
the same.
Noise Markers can be used like regular markers. A Noise Marker is
distinguished from a regular marker by (1Hz) after the marker readout value.
Learn more about regular markers in “All about Markers” on page 190.
How to measure Noise with a marker
—Press Marker to create or select a Normal or Delta marker to use to
measure Noise.
—Then More
.
—Then Marker Function
—Then Noise ON OFF
.
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 159).
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 134.
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