R&S 1129.7246.03, Operating Manual

Page: 66 / 855

Operating Manual 1302.6163.12 - 03 4.35
R&S ESU Instrument Functions
Receiver Mode
Consideration of the limit lines ensures that the final measurement is not performed
at frequencies at which the inference level is far below the limit value. The margin
between the acceptance line and the limit line can be selected by the user in dB as
the
MARGIN . Each limit line is allocated to a trace, i.e. different limit lines are taken
for the different detectors.
Two values should therefore be defined for this purpose:
• the number of subranges or highest level values ( NO OF PEAKS in the range from
1 to 500; default value: 25)
• the acceptance margin ( MARGIN ; default value: 6 dB). It is valid for all limit lines.
As an alternative method, it is possible to preset a list of frequencies at which the
final measurements are performed. A typical application is, for example, the statisti-
cal analysis of several units.
The peak list can be either edited manually or can be filled with desired values by
adopting the marker values.
If no limit lines are activated, the measurement procedure is as if all measured val-
ues would exceed the limit line.
4.5.4.5 Automatic Final Measurement with Threshold Scan
The interference spectrum is first pre-analyzed in a fast prescan to optimize the
duration of the measurement. If the measured level exceeds a limit line, or violates a
margin defined for this line, the time-consuming final measurement is performed.
The final measurement is, therefore, carried out only for a reduced number of fre-
quencies of interest. For this measurement, each scan trace to be taken into
account has to be assigned a limit line, and the limit line and the limit check function
have to be activated in the
LIMIT LINE menu.
The prescan is interrupted immediately for each final measurement to be performed,
i.e. the final measurement immediately follows the prescan measurement. In the
case of drifting or fluctuating interferers, this increases the probability that the signal
of interest will be reliably detected in the final measurement.
If the narrowband/broadband discrimination function is activated ( NB/BB DISCR
softkey), the R&S ESU automatically selects the detector to use in the final mea-
surement. To this end, the R&S ESU compares the positive and the negative peak
value obtained in the prescan. If the difference between the two values exceeds a
user-selected threshold, a broadband interferer is assumed, and the quasipeak
detector is used in the final measurement. If the difference falls below this threshold,
a narrowband interferer is assumed, and the average detector is used in the final
measurement. (The R&S ESU automatically determines the positive and the nega-
tive peak value during the prescan.)
The value obtained in the final measurement is added to the peak list, where it
replaces the result of the prescan. With
NO OF PEAKS , the maximum number of
peak values to be included in the list can be defined. If this number is attained, the
prescan will be continued, but no further final measurements will be performed.
THRESHOLD
SCAN
The THRESHOLD SCAN submenu is called from the RECEIVER main menu:
THRESHOLD ON | OFF
EDIT PEAK LIST
!
EDIT FREQUENCY
INSERT
DELETE