The Spectrum Application (RF Measurements)
R&S
®
FPL1000
428
User Manual 1178.3370.02 ─ 11
Figure 6-60: Example for an upper limit line
Limits and Margins
Limit lines define strict values that must not be exceeded by the measured signal. A
margin
is similar to a limit, but less strict and it still belongs to the valid data range. It
can be used as a warning that the limit is almost reached. The margin is not indicated
by a separate line in the display, but if it is violated, a warning is displayed. Margins are
defined as lines with a fixed distance to the limit line.
To check the signal for maximum levels you must define an
upper limit
, whereas to
check the signal for minimum levels you must define a
lower limit
.
Limits can be defined relative to the reference level, the beginning of the time scale, or
the center frequency, or as absolute values.
Relative scaling is suitable, for example, if masks for bursts are to be defined in zero
span, or if masks for modulated signals are required in the frequency domain.
Thresholds
If the y-axis for the limit line data points uses relative scaling, an additional absolute
threshold
can be defined for the limit check. In this case, both the threshold value and
the relative limit line must be exceeded before a violation occurs.
Display and Limit Lines
