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Spectrum Measurements

R&S

ESR

298User Manual 1175.7068.02 ─ 12

Setting the Number of Sweep Points

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. Like 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 final evaluation of

narrowband interferers.

Example:

Linear axis:

In case of a linear axis, the distance between the sweep points is equal, e.g. 200 kHz.

Logarithmic axis:

In case of 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 distance is several MHz.

The R&S ESR supports a maximum of 200000 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 when doing the final evaluation. Even when

covering 30 MHz to 1 GHz with logarithmic scaling and 120 kHz RBW.

Controlling V-Networks

For more information on Line Impedance Stability Networks see Chapter 5.2.5, "V-Net-

works Control (LISN)", on page 173.

Measurements

R&S ESR Series User Manual

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