R&S ESCI Receiver – MEAS Key
1166.6004.12 4.23 E-2
Data Reduction and Peak List
EMI measurements may involve much time because the time constants prescribed by the standard for
the quasi-peak weighting require transients which lead to long measurement times per each value. In
addition, the 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 quasi-peak weighting
at each frequency and for each setting of the test configuration would lead to unacceptably long
measurement times. For this reason, R&S has developed a method which reduces the time-consuming
measurements to a minimum with an optimum reliability of detection.
Data Reduction using the Subrange Maximum
The interference spectrum is first pre-analyzed in a fast prescan to optimize the duration of the
measurement. Data reduction follows so that the time-consuming final measurement is performed at
only some important frequencies:
dB
80
0
10
20
30
40
50
60
70
GHz
1,00,03 0,1
Subrange
Limit line
Acceptance line
Subrange maximum
Fig. 4-1 Dividing the spectrum into eight subranges
Data reduction is of crucial importance. It is initiated by the user pressing a key after the prescan and
then automatically performed by the receiver. Data reduction is used to select frequencies with a very
high interference level. Several data reduction methods are used:
• Acceptance analysis, i.e. the interference spectrum is further analyzed at frequencies with levels
above a line parallel to a limit line.
• Generating subrange maxima, i.e. the interference spectrum is further analyzed at frequencies with
the highest interference level of a frequency subrange (search method SUBRANGES).
• Determination of a specific number of peak values relative to the limit lines with the level values
being independent of their frequency spectral distribution (search method PEAKS).
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