R&S ESU Series, Operating Manual

Page: 65 / 855

R&S ESU Instrument Functions
Receiver Mode
4.34 Operating Manual 1302.6163.12 - 03
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:
Fig. 4.17 Dividing the spectrum into eight subranges
Data reduction is of crucial importance. It is initiated by pressing a key after the pres-
can and then automatically. 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).
For generation of subrange maxima, the whole frequency range is divided into equi-
distant subranges. A subrange maximum is determined for each subrange (search
method SUBRANGES).
Determining the level maxima irrespective of their distribution in the frequency spec-
trum (search mode PEAKS) is suitable for measurement regulations that demand
determination of the relatively highest level irrespective of the distribution in the
measured frequency range, e.g. FCC.
If the prescan is performed in parallel with several detectors, typically with peak
value and average value, the maxima are determined separately for the two detec-
tors so that the distribution of narrowband and wideband sources of interference can
be taken into account. For example, the frequency of the maximum determined with
the average detector can be used for the final measurement performed with this
detector and the frequency found in the prescan carried out with the peak detector is
taken for the final measurement using the quasipeak detector.
dB
80
0
10
20
30
40
50
60
70
GHz
1,0 0,03 0,1
Subrange
Limit line
Acceptance line
Subrange maximum