Instrument Function
R&S
®
SMB100A
131Operating Manual 1407.0806.32 ─ 13
Example: How to set up a closed loop power control
Fig. 5-1: Example of a test setup with NRP-Z Level Control
As shown in the example, the sensor measures a proportional power in defined time
intervals, derivated from a coupler. It considers optionally given S-parameters and returns
the results to the generator. The signal generator compares the measured level with the
set value and adjusts its output level accordingly.
This allows you to control the external signal level continuously and reliably reach a con-
stant input level at the DUT in real time.
Impact of the NRP-Z Level Control and the Operating Modes
Since the frequency and level of the RF output signal are continuously adjusted during
"NRP-Z Level Control", this operating mode interferes those with varying frequency and
level values.
The reason is, that the generator regularly transmits the output frequency to the connec-
ted R&S NRP-Zxx power sensor, which in turn requests the signal generator to adjust
the output level according to its measurement. In contrast to this real time control loop,
for example the list operating mode already generates the RF output signal on previously
optimized frequency and level value pairs. In this case, the "NRP-Z Level Control" as a
second control loop would impact the already determined RF signal values and also
considerably slow down the measurement. Similar impacts occur in sweep mode, and
also the "NRP-Z Power Viewer" and "NRP-Z Level Control" affect each other's function-
ality.
Hence, the operating modes exclude each other as follows:
● "NRP-Z Level Control" automatically disables NRP-Z Power Viewer, and vice versa.
●
Activating the RF frequency sweep, RF level sweep or the list mode instantly deac-
tivates a running "NRP-Z Level Control".
●
A running list or RF sweep mode blocks "NRP-Z Level Control". It can not be activa-
ted.
Also keep in mind that modulated signals may differ from CW signals regarding mean
power and peak power. This affects the operation of "NRP-Z Level Control".
RF Block
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