The Spectrum Application
R&S
®
FPC
130
User Manual 1178.4130.02 ─ 07
Figure 14-21: Display line at -38 dBm
14.12
Limit Lines
Access
(limit lines menu): "Lines"
Limit lines are an analysis tool that allows you to compare the measured signal levels
to signal specifications, and determine if the signal levels comply to the specifications.
Remote commands to configure limit lines:
●
Chapter 19.12.11, "Limit Lines"
A limit line is made up out of two or more points that are connected to a line. Each of
the points that define the shape of the limit line consists of two coordinates. One coor-
dinate defines the horizontal position (for example the frequency), the other one the
vertical position (usually a level value). You can make limit lines that consist of up to
1000 points.
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
FPC automatically
switches to a logarithmic scaling after you turn on the limit line.
When you turn on a limit line, the R&S
FPC 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
FPC 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.
Limit Lines
