Rohde&Schwarz R&S®NRQ6 Power Servoing - Application Sheet Application Sheet
R&S®NRQ6 / R&S®SGT100A
Power Servoing (R&S®NRQ6-K2)
Application Sheet
(;Ý5W2)
1179053902
Version 01
Application Sheet
R&S®NRQ6 / R&S®SGT100A
1 Your Task
For component tests, it can be required to set the DUT output power to a specific value
before starting the test of a test sequence.
This application sheet describes how to use the power servoing function of an
R&S NRQ6 together with an R&S SGT100A signal generator to achieve this goal. As
an example of a practical test, the measurement of the 3rd harmonic is shown, using
both an R&S NRQ6 and a spectrum analyzer.
2 Possible Solution
Component tests are complicated by the fact that they can be defined as a function of
the DUT output power, e.g. a power amplifier. To the test engineer, this dependency
poses a problem because the DUT gain is not necessarily:
●
Known beforehand
●
Constant over the input power
●
Constant over time or temperature
Your Task
Figure 2-1: Output power vs. input power of an amplifier
This situation calls for a closed loop control that allows to measure the output power at
the DUT iteratively and correct the signal generator power. Thus, in several steps, the
required power at the DUT output is finally reached.
A traditional implementation of such a control loop would run on a computer, use SCPI
commands to query a power sensor, compute the next value for the signal generator
2Application Sheet 1179.0539.02 ─ 01
R&S®NRQ6 / R&S®SGT100A
power, and send it to the signal generator. These steps are repeated until the measured power is close enough to the desired value.
Depending on the start value, the allowed tolerance and the nonlinearity of the DUT,
this procedure can take several 10 ms, which can be too long for automated test applications.
The power servoing functions of the R&S NRQ6 and R&S SGT100A offer a faster solution for this problem:
●
The power sensor measures continuously and sends results using a dedicated
serial connection to the signal generator - direct FPGA to FPGA communication,
no SCPI overhead.
●
The control algorithm runs on the signal generator - again, no SCPI overhead. The
application only needs to set the desired level in one command.
By using the R&S NRQ6 / R&S SGT100A power servoing and the high-speed remote
control of the R&S SGT100A, setting the desired power typically takes 1 ms to 1.5 ms.
Cabling and Configuration
3 Cabling and Configuration
Required equipment
●
R&S NRQ6 power sensor with power servoing option (R&S NRQ6-K2)
●
R&S SGT100A vector signal generator
●
Computer
●
SGMA GUI software for Windows and Red Hat / CentOS Linux operating systems.
Available for download at:
https://www.rohde-schwarz.com/software/sgt100a/
●
Optional: spectrum analyzer, for example an R&S FSV3000 or R&S FPL1000
●
Optional, if a spectrum analyzer is used: power splitter
3Application Sheet 1179.0539.02 ─ 01
R&S®NRQ6 / R&S®SGT100A
Setup
Cabling and Configuration
2 4
1
5
6
3
7
NRQ6
Frequency Selective Power Sensor
8
Sample Clock I/O (Default: 120
MHz)
9
LAN PoE+
Host
Interface
10
LO I/0
13
11
12
Figure 3-1: Cabling
1 = R&S SGT100A
2 = LAN interface
3 = USER 2 connector
4 = RF 50 Ω connector
5 = DUT
6 = Power splitter
7 = RF connector
8 = R&S NRQ6
9 = LAN PoE+ interface
10 = TRIG2 connector
11 = Ethernet switch supporting PoE+ power delivery, for example. Alternatively, you can use the other set-
ups described in the user manual of the R&S NRQ6.
12 = Spectrum analyzer
13 = Computer
1. Connect the instruments as shown in Figure 3-1.
2. Make sure to connect the TRIG2 connector of the R&S NRQ6 to the USER 2 con-
nector of the R&S SGT100A.
3. Connect all instruments and the computer to the local network.
Preparing the measurement
1. Switch on all instruments.
2. If the SGMA GUI software is not already available on the computer, install it.
3. Start the SGMA GUI software.
4. In the toolbar, click the blue icon to open the "Configure Instruments" dialog.
4Application Sheet 1179.0539.02 ─ 01
Loading...