Measurements
R&S
®
FSW
181
User Manual 1173.9411.02 ─ 19
5.3.7.3
Measurement Example 3 – Measuring the Intrinsic Noise of the R&S
FSW with
the Channel Power Function
Noise in any bandwidth can be measured with the channel power measurement func-
tions. Thus the noise power in a communication channel can be determined, for exam-
ple. If the noise spectrum within the channel bandwidth is flat, the noise marker can be
used to determine the noise power in the channel by considering the channel band-
width. If, however, phase noise and noise that normally increases towards the carrier is
dominant in the channel to be measured, or if there are discrete spurious signals in the
channel, the channel power measurement method must be used to obtain correct mea-
surement results.
Test setup:
► Leave the RF input of the R&S
FSW open-circuited or terminate it with 50 Ω.
Procedure:
1. Preset the R&S
FSW.
2. Set the center frequency to
1
GHz
and the span to
1 MHz
.
3. To obtain maximum sensitivity, set RF attenuation to
0 dB
and the reference level
to
-40
dBm
.
4. Select the "Channel Power ACLR" measurement function from the "Select Mea-
surement" dialog box.
5. In the "ACLR Setup" dialog box, set up a single Tx channel with the channel band-
width
1.23
MHz
.
6. Select the "Adjust Settings" softkey.
The settings for the frequency span, the bandwidth (RBW and VBW) and the
detector are automatically set to the optimum values required for the measure-
ment.
7. Stabilize the measurement result by increasing the sweep time.
Set the sweep time to
1
s
.
The trace becomes much smoother because of the RMS detector and the channel
power measurement display is much more stable.
Channel Power and Adjacent-Channel Power (ACLR) Measurement
