Improving Level Performance
R&S
®
SMA100B
161
User Manual 1178.3834.02 ─ 03
If a sensor is connected via LAN or uses the USBTMC protocol, its protocol is indica-
ted as "Visa".
Remote command:
Scan
Scans the network and the USB connections for sensors connected via the VISA com-
munication protocol, i.e. sensors that are addressed via LAN or USBTMC.
Sensors communicating via the USB legacy protocol are detected automatically.
Remote command:
6.4.3 NRP Power Viewer
The R&S
SMA100B features the power viewer function for measuring or monitoring
signals with R&S NRP power sensors.
6.4.3.1
About
The R&S
SMA100B can perform up to four power measurements simultaneously. The
measured signals can be the RF output power or other selected signal sources.
About the measuring principle, averaging filter, filter length, and achieving sta-
ble results
A sensor measures the average signal power of the selected source continuously. The
measurement results are displayed the "NRP Power Viewer" dialog.
The power viewer function uses
averaging filters
to reduce the fluctuations of the
measurement result to the desired extent. Common sources of fluctuations are inher-
ent noise of the measuring instrument, modulation of the measurement signal or influ-
ences from the superposition of adjacent carriers. Common method for achieving more
stable display is the use of longer measurements. The term longer measurements do
not mean that it takes longer to display a new result. The term refers to the time it
takes for the result to settle when the power varies.
Measurements are continuously repeated in a predefined time window. The measure-
ment result is obtained by averaging the measured values for the last 2N time win-
dows. This approach is referred as a
two-step averaging process
.
The factor of 2 in the formula arises because the output signals from the microwave
detector are chopped at the same rate as the time windows to suppress low-frequency
noise. An independent measured value can only be obtained from two consecutive val-
ues.
The variable N in the formula indicates the
filter length
. The filter length then directly
influences the measurement time. The filter length can be selected automatically or it
can be manually set to a fixed value.
Using Power Sensors