1009
Marker Function
When Marker Noise is on, the marker’s Y Axis Result is the average noise level, normalized to a 1 Hz
noise power bandwidth, in the band specified under the Band Adjust key.
See “More Information” on page 1009.
See “Off-trace Markers” on page 1009.
More Information
To guarantee accurate data for noise-like signals, a correction for equivalent noise bandwidth is made by
the test set. The Marker Noise function accuracy is best when the detector is set to Average or Sample,
because neither of these detectors will peak-bias the noise. The trade off between sweep time and
variance of the result is best when Average Type is set to Power Averaging. Therefore, Auto coupling
chooses the Average detector and Power Averaging when Marker Noise is on. Though the Marker Noise
function works with all settings of detector and Average Type, using the positive or negative peak
detector gives less accurate measurement results.
Off-trace Markers
If a Normal or Delta noise marker is so near to the left or right edge of the trace that some of the band is
off the trace, then it uses only that subset of the Band Width that is on-trace. If the marker itself is
off-trace, its value becomes undefined.
Neither band/interval power nor band/interval density markers are defined if any part of the band is
off-trace (unless they are Fixed with a stored function value in them), except that when the edges of the
bandwidth are trivially off-screen, due to mathematical limitations in the test set or in the controlling
computer, the result will still be considered valid.
Key Path Marker Function
Example CALC:MARK:FUNC NOIS turns on marker 1 as a noise marker.
CALC:MARK:FUNC? returns the current marker function for the marker
specified. In this case it returns the string: NOIS.
CALC:MARK:Y? returns the y-axis value of the Marker Noise function for
marker 1 (if Marker Noise is ON for marker 1). Note that the delta value when
the Y axis unit is Watt is the square of the delta value when the Y axis unit is
Volt. For example, when the percent ratio with Y axis unit in Volt is 0.2, the
percent ratio with Y axis unit in Watt will be 0.22 = 0.04. When you read the
value out remotely you have to know whether your Y Axis Unit is log (dB),
linear (V or A), or power (W).
Notes See the description under the ““Marker Function” on page 1007” key.
Dependencies Fixed markers: It is not possible to change the Band Function for a Fixed
marker; so all of the Band Function keys are grayed out for a Fixed marker.
Couplings Average detector and Power Averaging auto selected when Marker Noise on
If the selected (specified) marker is off, selecting Marker Noise via front panel
or SCPI will turn the marker on.
Initial S/W Revision Prior to A.02.00