R&S 1129.7246.03, Operating Manual

Page: 184 / 855

Operating Manual 1302.6163.12 - 03 4.153
R&S ESU Instrument Functions
Analyzer Mode
4.8.11.1 Activating the Markers
SELECT
MARKER The SELECT MARKER softkey activates the numerical selection of the marker in
the data entry field. Delta marker 1 is selected by input of ' 0 '.
If the marker is switched off, then it is switched on and can be moved later on.
Remote command:
CALC:MARK1 ON;
CALC:MARK1:X <value>;
CALC:MARK1:Y?
PEAK The PEAK softkey sets the active marker/delta marker to the peak of the trace.
Remote command:
CALC:MARK1:MAX
CALC:DELT1:MAX
4.8.11.2 Measurement of Noise Density
NOISE MEAS
The NOISE MEAS softkey switches the noise measurement for the active marker on
or off. The corresponding marker becomes the NORMAL marker.
During noise measurement, the noise power density is measured at the position of
the marker. In the time domain mode, all points of the trace are used to determine
the noise power density. When measurements are performed in the frequency
domain, two points to the right and left of the marker are used for the measurement
to obtain a stable result.
The noise power density is indicated in the marker field. With a logarithmic ampli-
tude units (dBm, dBmV, dBmµV, dBµA) the noise power density is output in dBm/Hz
i.e. as level in 1 Hz bandwidth with reference to 1 mW. With linear amplitude units (V,
A,
Ω
) the noise voltage density is evaluated in µV/
√
Hz, the noise current density in
µA/
√
Hz or the noise power density in µW/Hz.
The following settings have to be made to ensure that the power density measure-
ment yields correct values:
In the default setting, the R&S ESU uses the sample detector for the noise function.
With the sample detector, the trace can additionally be set to AVERAGE to stabilize
the measured values. With RMS detector used, trace averaging must not be used
since in this case it produces too low noise levels which cannot be corrected.
Instead, the sweep time can be increased to obtain stable measurement results.
The R&S ESU uses the following correction factors to evaluate the noise density from
the marker level:
• Since the noise power is indicated with reference to 1 Hz bandwidth, the
bandwidth correction value is deducted from the marker level. It is 10 × lg (1 Hz/
BW
Noise
), where BW
Noise
is the noise or power bandwidth of the set resolution
filter (RBW).
Detector: Sample or RMS
Video bandwidth:
≤
0.1 × resolution bandwidth with sample detector
(corresponds to RBW / VBW NOISE)
≥
3 × resolution bandwidth with RMS detector (corresponds to
RBW / VBW SINE)