Measurements and Results
R&S
®
FSW
209
User Manual 1173.9411.02 ─ 43
To determine the noise power, a channel with a defined bandwidth at the defined cen-
ter frequency is analyzed. The power within this channel is integrated to obtain the
noise power level. (If the carrier is within this channel, an extra step is required to
determine the correct noise power level, see below.)
The noise power of the channel is subtracted from the maximum carrier signal level,
and in the case of a C/N
0
measurement, it is referred to a 1
Hz bandwidth.
For this measurement, the RMS detector is activated.
The carrier-to-noise measurements are only available in the frequency domain (span
>0).
Measurement process
Depending on whether the carrier is inside or outside the analyzed channel, the mea-
surement process for the carrier-to-noise ratio varies:
●
The carrier is outside the analyzed channel: In this case, it is sufficient to switch on
the desired measurement function and to set the channel bandwidth. The carrier/
noise ratio is displayed on the screen.
●
The carrier is inside the analyzed channel: In this case, the measurement must be
performed in two steps:
–
First, perform the reference measurement by switching on either the C/N or the
C/N
0
measurement and waiting for the end of the next measurement run. The
fixed reference marker is set to the maximum of the measured carrier signal.
–
Then, switch off the carrier so that only the noise of the test setup is active in
the channel. The carrier-to-noise ratio is displayed after the subsequent mea-
surement has been completed.
Frequency Span
The frequency span should be set to approximately twice the channel bandwidth in
order to measure the carrier-to-noise ratio correctly. This setting is defined automati-
cally by the "Adjust Settings" function.
7.3.2
Carrier-to-Noise Results
As a result of the carrier-to-noise measurement the evaluated bandwidth and the cal-
culated C/N ratio are displayed in the result window. The fixed reference marker is indi-
cated in the diagram.
Carrier-to-Noise Measurements
