Common Measurement Settings
R&S
®
FSVA3000/ R&S
®
FSV3000
367
User Manual 1178.8520.02 ─ 01
The reference level determines the amplitude represented by the topmost grid line in
the display. When you change the reference level, the measurement is not restarted;
the results are merely shifted in the display. Only if the reference level changes due to
a coupled RF attenuation (see
on page 371), the mea-
surement is restarted.
In general, the R&S
FSV/A measures the signal voltage at the RF input. The level dis-
play is calibrated in RMS values of an unmodulated sine wave signal. In the default
state, the level is displayed at a power of 1 mW (= dBm). Via the known input impe-
dance, conversion to other units is possible.
See
Reference level offset
If the signal is attenuated or amplified before it is fed into the R&S
FSV/A, you can
define an (arithmetic) offset to the reference level so the application shows correct
power results. All displayed power level results are shifted by this value, and the scal-
ing of the y-axis is changed accordingly.
To determine the required offset, consider the external attenuation or gain applied to
the input signal. For attenuation, define a positive offset so the R&S
FSV/A increases
the displayed power values.
If an external gain is applied, define a negative offset so the R&S
FSV/A decreases the
displayed power values.
Note, however, that the
internal
reference level (used to adjust the hardware settings to
the expected signal optimally) ignores any "Reference Level Offset" . Thus, it is impor-
tant to keep in mind the actual power level the R&S
FSV/A must handle, and not to rely
on the displayed reference level.
internal reference level = displayed reference level - offset
Example
1. The initial reference level is 2
dBm with no offset.
Both the displayed reference level and the internal reference level are 2
dBm.
2. An offset of 3
dB is defined.
The displayed reference level is adjusted to 5
dBm.
The internal reference level remains at 2
dBm.
(5
dBm (displayed ref level) - 3
dB (offset) = 2
dBm)
3. Now the user decreases the reference level to 1
dBm.
The displayed reference level is adjusted to 1
dBm.
The internal reference level is adjusted to:
1
dBm (displayed ref level) - 3
dB (offset) = -2
dBm.
Amplitude and Vertical Axis Configuration
