The Spectrum Application
R&S
®
FPC
101
User Manual 1178.4130.02 ─ 07
You can change the position of the reference level to another grid line, if required for
any reason.
1. Press the "Ampt" key to open the amplitude menu.
2. Select the "Range / Ref Position" menu item to open the display range menu.
3. Select the "Reference Position 10 ..." menu item.
The R&S
FPC opens an input field to define the reference position.
4. Enter the number of the grid line (0 to 10) you want the reference level at.
"0" corresponds to the grid line at the bottom of the diagram. "10" corresponds to
the grid line at the top of the diagram.
The R&S
FPC adjusts the position of the trace accordingly.
14.4.2
Measurement Sensitivity
The R&S
FPC provides several ways to improve (control) the sensitivity of a measure-
ment.
RF attenuator
The internal RF attenuator is a hardware component to control measurement sensitiv-
ity.
It is coupled directly to the reference level and has the following effects.
●
High attenuation protects the input mixer. Protecting the input mixer is the main
purpose of the attenuator.
●
High attenuation makes sure that the measurement results are reliable. Signals
that are stronger than allowed might distort the results.
●
High attenuation increases inherent noise (i.e. the noise floor) and thus decreases
measurement sensitivity: if you increase attenuation by 10 dB, the sensitivity is
reduced by 10 dB (in other words: the displayed noise increases by 10 dB).
●
High attenuation helps to avoid intermodulation.
Depending on the required test setup, a compromise must be found between a high
sensitivity, low intermodulation and input mixer protection. This is best done by letting
the R&S
FPC determine the ideal attenuation automatically. Determining the attenua-
tion automatically might not necessarily utilize the maximum dynamic range, but still
yields valid and reliable results.
When you select the attenuation manually and are measuring unknown signals, espe-
cially DUTs with a high RFI voltage, always select the highest possible attenuation
level before you apply the signal.
If you need a better sensitivity or signal-to-noise ratio, make sure that the applied sig-
nal does not exceed the specified limits, before you lower the attenuation.
Defining RF attenuation
1. Press the "Ampt" key to open the amplitude menu.
Amplitude Configuration
