R&S FSW Series, Руководство пользователя

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Measurements and Results
R&S
®
FSW
338 User Manual 1173.9411.02 ─ 43
7.13.3.3 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.
The resolution bandwidth should cover at least one sweep point (more is better). If this
condition is not met, signals or interferences could be missed during refined measure-
ment of narrowband interferers. If the distance between two sweep points is larger than
RBW/3, a warning is displayed in the status bar ("Increase Sweep Points").
Example:
Linear axis:
With a linear axis, the distance between the sweep points is equal, e.g. 200 kHz.
Logarithmic axis:
With a logarithmic axis, the distance between sweep points is variable. In the spectrum
from 10
Hz to 100 Hz, the distance is a few Hz. Between 100 MHz and 1 GHz, the dis-
tance is several MHz.
The R&S FSW EMI measurement supports a maximum of 200001 sweep points.
This number is based on typical bands measured with a single resolution bandwidth.
There are sufficient sweep points to make sure that a signal is found during the refined
measurement, even when covering 30
MHz to 1 GHz with logarithmic scaling and
120 kHz RBW.
Electromagnetic Interference (EMI) Measurement