R&S FSH
How a Spectrum Analyzer Works
Deleting Datasets
Operating Manual 1309.6275.12 - 14
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The figure above shows 30 measured values which are represented by a single pixel.
The peak detector determines and displays the maximum measured value. The Auto
Peak detector takes the maximum and minimum and displays them together. The two
values are joined by a vertical line segment. This gives a good indication of the level
variation over the measured values represented by a single pixel. The RMS detector is
used by the spectrum analyzer to determine the RMS value of the measured values. It
is therefore a measure of the spectral power represented by a pixel. The sample
detector takes an arbitrary measurement value and displays it (in the Fig. above, the
first). The other measured values are ignored.
On the basis of the operating principles of detectors, a few recommendations can be
made as to their use.
C
It is best to use the Auto Peak detector or the peak detector for spectrum analysis
over large frequency ranges. This ensures that all signals are displayed.
C
The RMS detector is recommended for power measurements on modulated
signals. However, the display range should be chosen so as not to exceed 100
times the bandwidth of the signal or the resolution bandwidth, whichever is larger.
C
The sample detector or the RMS detector (preferred) should be used for noise
measurements. Only these two detectors are capable of measuring noise power
correctly.
C
When measurements are made on sine signals, the level display does not depend
on the detector. However, if you use the RMS detector or the sample detector,
ensure that the span is not too great. Otherwise, the displayed levels of sine
signals may be lower than their true value.
