R&S ESCI Receiver – MEAS Key
1166.6004.12 4.21 E-2
Average measurement: With average detection selected, the video voltage (envelope of
IF signal) is averaged during the measurement time. Averaging is
digital, i.e. the digitized values of the video voltage are summed
up and divided by the number of samples at the end of the
measurement time. This corresponds to a filtering with a
rectangular window in the time domain and a filtering with sin x/x
characteristic in the frequency domain. With unmodulated signals
the shortest possible measurement time can be selected. With
modulated signals the measurement time is determined by the
lowest modulation frequency to be averaged. With pulse signals,
the selected measurement time should be long enough for
sufficient number of pulses (>10) to occur in the measurement
window for averaging.
CISPR average measurement: With a CISPR average measurement, the maximum value of the
weighted signal during the measurement time is displayed. The
relatively long time constants used with CISPR average detectors
result in long measurement times in order to obtain a correct
measurement result. If unknown signals are measured, the
measurement time should be at least one second so that pulses
down to a frequency of 5 Hz are correctly weighted.
After a frequency change or a modification of the attenuation, the
receiver waits until the lowpass has settled before the
measurement time starts. The measurement time is selected
depending on the IF bandwidth and the characteristics of the
signal to be measured. Unmodulated sinusoidal signals as well as
signals with high modulation frequency can be measured within a
short time. Slowly fluctuating signals or pulse signals require
longer measurement times.
RMS measurement: With RMS weighting the same applies to the measurement time
as with the average measurement.
Quasi-peak measurement: With quasi-peak measurements, the maximum value of the
weighted signal during the measurement time is displayed. The
relatively long time constants used with quasi-peak detectors
entail long measurement times to obtain correct results. With
unknown signals the measurement time should be at least 1 s.
This ensures correct weighting of pulses down to a pulse
frequency of 5 Hz.
After internal switching, R&S ESCI waits until the measurement
result has stabilized before it starts the actual measurement.
Since the level does not change during a frequency scan, known
signals (e.g. broadband RFI) can be correctly measured with a
much shorter measurement time.
Measurement with several
detectors:
If several detectors are used simultaneously, a measurement time
suiting the slowest detector should be selected to obtain correct
results for all detectors. It is therefore recommended to set a
measurement time that matches the average detector when the
peak and average detectors are used.
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