R&S FSL Noise Measurements
1300.2519.12 2.19 E-11
Example
The measured internal noise power of the R&S FSL at an attenuation of 0 dB is found to be –143
dBm/1 Hz. The noise figure of the R&S FSL is obtained as follows
NF = –143 + 174 = 31 dB
Note: If noise power is measured at the output of an amplifier, for example, the sum of the internal
noise power and the noise power at the output of the DUT is measured. The noise power of the
DUT can be obtained by subtracting the internal noise power from the total power (subtraction
of linear noise powers). By means of the following diagram, the noise level of the DUT can be
estimated from the level difference between the total and the internal noise level.
-10
-9
-8
-7
-6
-5
-4
-3
-
2
-
1
0
012345678910111213141516
Total power/intrinsic noise power in dB
factor in dB
Fig. 2-14 Correction factor for measured noise power as a function of the ratio of total power to the
intrinsic noise power of the spectrum analyzer
Measurement of Noise Power within a Transmission
Channel
Noise in any bandwidth can be measured with the channel power measurement functions. Thus the
noise power in a communication channel can be determined, for example. If the noise spectrum within
the channel bandwidth is flat, the noise marker from the previous example can be used to determine the
noise power in the channel by considering the channel bandwidth. 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 measurement results.
To Next Page
Loading...
