R&S FSW Series, Руководство пользователя

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Common Measurement Settings
R&S
®
FSW
449 User Manual 1173.9411.02 ─ 43
● Impact of the Vertical Axis Settings .......................................................................449
● Amplitude Settings ................................................................................................ 451
● Scaling the Y-Axis ................................................................................................. 456
● How to Optimize the Amplitude Display ................................................................458
8.4.1 Impact of the Vertical Axis Settings
Some background knowledge on the impact of the described settings is provided here
for a better understanding of the required configuration.
● Reference Level ....................................................................................................449
● RF Attenuation ...................................................................................................... 450
● Scaling .................................................................................................................. 451
8.4.1.1 Reference Level
The reference level value is the maximum value the AD converter can handle without
distortion of the measured value. Signal levels above this value will not be measured
correctly, which is indicated by the "IF Overload" status display.
Internally, the reference level is also used to determine the optimum hardware settings
for the R&S
FSW. The defined reference level should correspond with the maximum
expected RF input level.
When determining the expected input level, consider that the power from all input sig-
nals contribute to the total power. The reference level must be higher than the total
power from all signals.
The optimum reference level for the current measurement settings can be set automat-
ically by the R&S
FSW (see "Reference Level" on page 452).
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
"Attenuation Mode / Value" on page 454), the measure-
ment is restarted.
In general, the R&S FSW 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 "Impedance" on page 368.
Reference level offset
If the signal is attenuated or amplified before it is fed into the R&S FSW, 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 scaling of the
y-axis is changed accordingly.
Amplitude and Vertical Axis Configuration