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Measurements and Results

R&S

FSW

338User 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

R&S FSW Series User Manual

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