The Spectrum Application
FPC1000
108
User Manual 1178.4130.02 ─ 02
Values that define the horizontal characteristics of the limit line can be either absolute
values (for example the frequency in MHz) or relative values whose reference is the
center of the measurement trace (for example the center frequency). Relative values
are useful, for example, if you measure modulated output signals and change the cen-
ter frequency, but need the limit line to remain the same. Absolute limit lines have the
file extension
.abslim
while relative limit lines have the file extension
.rellim
.
Values that define the vertical characteristics are always level values in dB. If the scal-
ing of the vertical axis is a linear one (units V or W), the R&S
FPC1000 automatically
switches to a logarithmic scaling after you turn on the limit line.
When you turn on a limit line, the R&S
FPC1000 checks if the signal violates the shape
of the limit line at one or more positions. If one or more signal levels exceed the limit
value, the R&S
FPC1000 features several indicators that the limit check has failed.
●
A general message in the diagram header that indicates if the signal violates the
limit line, including the trace that violates the limit:
●
An audio signal that sounds every time a limit is violated.
You can create and edit limit lines with the R&S
InstrumentView software package and
then transfer them into the internal memory of the R&S
FPC1000. The number of limit
lines you can store in the memory depends on other datasets available on
theR&S
FPC1000 or, if you are using an external storage device (for example memory
stick), the size of it.
Selecting a limit line
Before selecting a limit line, you need to decide if you want to use it as an upper or
lower limit line.
Upper limit lines check if the signal is or remains below the limit line.
Lower limit lines check if the signal is or remains above the limit line.
You also have to make sure that the limit line is compatible to the scale of the x-axis.
1. Press the "Lines" key top open the lines menu.
2. Make sure that the "Show Limit Lines" menu item is active (highlighted).
3. Select the "Upper Limit" or the "Lower Limit" menu item.
4. Select the "Load From File" menu item to open the file manager.
The R&S
FPC1000 opens the directory that contains the limit lines by default
(
\LimitLines\
). If you have stored limit lines in another directory, you have to
navigate to that directory first.
By default, the R&S
FPC1000 shows all limit lines available in the selected direc-
tory (files with the
.abslim
or
.rellim
extension), even those that are not com-
patible to the current diagram scale.
5. Select the "Show Compatible" menu item to filter the available limit lines.
The R&S
FPC1000 shows only the limit lines that you can apply to the current dia-
gram scale.
Limit Lines
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