Measurements
R&S
®
FSW
294
User Manual 1173.9411.02 ─ 19
When you change the frequency or the attenuation, the R&S
FSW waits until the low-
pass filter has settled before starting the measurement. In this case, the measurement
time depends on the resolution bandwidth and the characteristics of the signal.
RMS Average detector (CISPR filter only)
The RMS Average detector is a combination of the RMS detector (for pulse repetition
frequencies above a corner frequency) and the Average detector (for pulse repetition
frequencies below the corner frequency). It thus achieves a pulse response curve with
the following characteristics:
●
10
dB/decade above the corner frequency
●
20
dB/decade below the corner frequency
The average value is determined by lowpass filters of the 2nd order (simulation of a
mechanical pointer instrument).
The RMS Average detector is only available for the CISPR filter.
The detector is used, for example, to measure broadband emissions and may replace
the quasipeak detector in the future.
The detector parameters depend on the measured frequency. The time lag of the
simulated pointer instrument reflects the weighting factor of the signal depending on its
form, modulation, etc.
Table 5-18: Required parameters depending on frequency for RMS Average detector
Band A
Band B
Band C/D
Band E
Frequency range
<150
kHz
150
kHz to 30
MHz
30
MHz to 1
GHz
>1
GHz
IF bandwidth
200
Hz
9
kHz
120
kHz
1
MHz
Time lag of simula-
ted pointer instru-
ment
160
ms
160
ms
100
ms
100
ms
Corner frequency
10
Hz
100
Hz
100
Hz
1
kHz
The same considerations apply to the dwell time as for the CISPR average detector.
5.13.3.3
Frequency Resolution - Sweep Points and Scaling
The number of sweep points defines the number of measurement values collected dur-
ing one sweep. Thus, increasing the sweep points also increases the accuracy of the
results regarding the frequency resolution.
Because EMI measurements often cover a large frequency range you should define an
adequate number of sweep points, especially when performing the measurement on a
logarithmic axis. As on a linear axis, the distance from one sweep point to the next is
calculated graphically on a logarithmic axis, and is not based on the frequency itself.
Thus, the frequency resolution between two sweep points deteriorates with higher fre-
quencies.
Electromagnetic Interference (EMI) Measurement (R&S
FSW-K54)
