Measuring the Carrier-to-Noise Ratio
R&S FSH
1145.5973.12 4.56
E-11
Switch off the reference display.
Press the REF MEASURE softkey.
Using the rotary knob or the cursor keys, select
DISPLAY OFF and confirm your choice with the
ENTER key or the F4 softkey.
Switch the reference display on again.
Press the REF MEASURE softkey.
Using the rotary knob or the cursor keys, select
DISPLAY ON and confirm your choice with the ENTER
key or the F4 softkey.
Note:
Switching the measurement result on or off also affects the insertion of the measured value
of the noise measurement.
Units of the C/N reference
The R&S FSH displays the C/N reference as a level in dBm, dB
O
V or dBmV.
The C/N reference is manually entered in accordance with the selected unit.
Press the LEVEL softkey.
Using the rotary knob or the cursor keys, select the
desired unit and confirm your choice with the
ENTER key or the F2 softkey.
The C/N reference is displayed in the selected unit.
Measuring the noise channel power and calculating the carrier
power/noise power
The noise channel power is measured in an unoccupied transmission channel. The R&S FSH
measures the spectrum within the channel using a resolution bandwidth that is small in comparison with
the channel bandwidth. The measured values on the trace are then integrated to form the total power.
The R&S FSH takes into account the behavior of the selected display mode (linear or logarithmic) of the
selected detector and the resolution bandwidth. The small resolution bandwidth acts like a steep
channel filter, thus preventing out-of-channel emissions from affecting the result.
To determine the C/N power ratio, the measured noise channel power is set in relation to the reference.
carrier/noise = reference/noise channel power
The settings span, resolution bandwidth, video bandwidth and sweep time are coupled to the channel
bandwidth and are optimally set by the R&S FSH.
If you want to change the settings, note the following:
