Measurements and Result Displays
R&S
®
ESW
108
User Manual 1177.6298.02 ─ 08
In time domain measurement systems, the spectrum at the receiver input is mea-
sured in parallel by using fast fourier transform (FFT) of frequency sections.
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Fixed frequency scan on a single frequency
This scan is carried out on a fixed frequency. It is used to examine the time charac-
teristics of interferences, e.g. click analysis.
Stepped Scans in the Frequency Domain
In stepped scan mode, the step width and the frequency spacing (step mode) can be
selected. Linear, logarithmic or automatic frequency spacing is available. In automatic
mode, the step width is selected so that it is always smaller than the bandwidth.
Receiver measurements may involve much time. Time saving procedures are
explained in
on page 108. They reduce the total measurement time by
reducing the number of measurements to a minimum.
Nevertheless, this time is still very long, often in the order of hours, especially for the
CISPR radiated emissions tests. A way out of this situation can be time-domain mea-
surements.
Peak Search
The Peak Search function of the R&S
ESW can be used to create a peak list contain-
ing only the measurement values of high interferers. In a fast prescan the signal is
measured against a limit line, and the level values above the set margin are written into
the peak list. The resulting peak list then is used for the final measurement where only
the frequencies in the peak list are measured with the required detector.
If the scan uses the detector stipulated by the specifications, the peak list already pro-
vides the final measurement data.
Data Reduction using the Peak List
EMI measurements may take some time because the time constants of up to 160
ms
prescribed by the standard for the quasipeak weighting lead to long measurement
times per each value. In addition, some standards stipulate procedures for finding local
EMI maxima such as shifting the absorbing clamp, variation of the test antenna height
and rotating the DUT. Measuring with quasipeak weighting at each frequency and for
each setting of the test configuration would lead to unacceptably long measurement
times. For this reason, a method is used which reduces the time-consuming measure-
ments to a minimum with an optimum reliability of detection.
Receiver measurements may take some time because of some specialties in the con-
text of those measurements like variations of the test antenna or high time constants
required by detectors or things like that. Because of this, the Receiver provides tools
that reduce the efforts to a minimum while still providing an optimum measurement reli-
ability.
The interference spectrum is first pre-analyzed in a fast prescan to optimize the dura-
tion of the measurement. Data reduction follows so that the time-consuming final mea-
surement is performed only at critical frequencies.
Several data reduction methods are used:
Test Automation
