R&S NRP18S Series User Manual page 7

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R&S NRP18S-xx
Figure 1-1: R&S NRP18S-10, R&S NRP18S-20 and R&S NRP18S-25 (from left)
To provide physically correct results, the sensor itself numerically compensates the
influence of the attenuator. Hence, the measurement output is not the power level that
is measured at the input port of the sensor. It represents the power level at the input of
the attenuator.
This numerical compensation of a two-port ("S-parameter device") connected
upstream is also implemented in R&S NRP power sensors that are delivered without
an attenuator. You can select any third-party attenuator, measure its S-parameters and
connect it upstream of the sensor in place of the supplied attenuator.
However, a precise measurement of the S-parameters is not trivial, and not all attenua-
tors are sufficiently stable. To enable high-precision power measurements with R&S
NRP18S‑xx power sensors, each included attenuator is highly stable and accurately
calibrated on site. The factory-provided calibration data is stored in the factory calibra-
tion data set of the sensor and includes the precisely determined S-parameter values.
At start-up of the power sensor, it automatically activates S-parameter correction based
on the stored S-parameters. You can change this default behavior using the S-parame-
ters tool included in the R&S NRP Toolkit, see
tion",
●
If you use the power sensor without an attenuator to increase sensitivity, disable S-
parameter correction.
●
If you use the power sensor with a third-party attenuator, load its S-parameters and
define it as the active device.
For a detailed specification, refer to the data sheet.
User Manual 1178.3686.02 ─ 05
on page 87.
Chapter 8.8.4.3, "S-Parameter Correc-
Preface
Key Features
7