Rohde & Schwarz FPC Series, User Manual

Page: 102 / 419

The Spectrum Application
R&S
®
FPC
99 User Manual 1178.4130.02 ─ 07
If you need an input impedance of 75 Ω, you have to connect one of the supported
matching pads to the RF input. When one of the supported matching pads is connec-
ted, you can change the input impedance. The R&S
FPC in that case automatically
considers the conversion factor.
The matching pads are available as accessories. Refer to the datasheet for ordering
information.
1. Press the "Ampt" key to open the amplitude menu.
2. Select the "Impedance" menu item to open the impedance menu.
3. Select the input impedance you need.
In addition to the "50
Ω
" impedance, you can select a 75
Ω
when one of the sup-
ported matching pads is connected. The R&S FPC supports the following matching
pads: "75
Ω
RAM", "75
Ω
RAZ" or "75
Ω
FSH-Z38".
● Reference Level ......................................................................................................99
● Measurement Sensitivity .......................................................................................101
● Scale of the Y-Axis ................................................................................................ 103
● Transducers .......................................................................................................... 104
14.4.1 Reference Level
The reference level is the signal level that the analyzer expects at the RF input. In fact,
it should be slightly higher than the expected level of the signal you are measuring. If
necessary, the analyzer also attenuates or amplifies the signal to yield the best possi-
ble dynamic range.
When you define a low reference level (meaning that a weak signal is expected), the
analyzer amplifies the signal internally to display even weak signals clearly. On the
other hand, when you apply a strong signal (or an unknown signal), you have to make
sure to define a reference level high enough for that signal to prevent an overload sit-
uation in the signal path. A high reference level also keeps the displayed signal within
the display range.
If you are measuring the spectrum of a composite signal, make sure that the reference
level is high enough to cover all signals and that all signals are within the
display
range .
In the measurement diagram, the reference level is represented by the topmost grid
line.
Defining a reference level
1. Press the "Ampt" key to open the amplitude menu.
2. Select the "Reference Level" menu item.
The R&S FPC opens an input field to define the reference level.
Tip: When you press the "Ampt" key, the R&S FPC automatically opens an input
field to define the reference level. If the input field is inactive, you can open it with
the "Reference Level" menu item.
Amplitude Configuration