R&S FSMR, Operating Manual

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R&S FSMR Limit Lines
1166.3363.12 4.17-1 E-2
Setup of Limit Lines and Display Lines – LINES Key
Limit lines are used to define amplitude curves or spectral distribution boundaries on the display screen
which are not to be exceeded. They indicate, for example, the upper limits for interference radiation or
spurious waves which are allowed from a unit under test (UUT). For transmission of information in
TDMA (e.g. GSM), the amplitude of the bursts in a timeslot must adhere to a curve which must fall
within a specified tolerance band. The lower and upper limits may each be specified by a limit line. Then,
the amplitude curve can be controlled either visually or automatically for any violations of the upper or
lower limits (GO/NOGO test).
The instrument supports limit lines with a maximum of 50 data points. 8 of the limit lines stored in the
instrument can be used simultaneously and activated in the split-screen mode either in Screen A,
Screen B or in the two windows. The number of limit lines stored in the instrument is only limited by the
capacity of the flashdisk used.
For each limit line, the following characteristics must be defined:
•
The name of the limit line. The limit line data are stored under this name and can be examined in the
table
LIMIT LINES.
•
The domain in which the limit line is to be used. Here, a distinction is made between the time domain
(span = 0 Hz) and the frequency domain (span > 0 Hz).
•
The reference of the interpolation points to the X axis. The limit line may be specified either for
absolute frequencies or times or for frequencies which are related to the set center frequency and
times related to the time on the left edge of the diagram.
•
The reference of the interpolation points to the Y axis. The limit line can be selected either for
absolute levels or voltages or referred to the set maximum level (Ref Lvl). The position on the display
depends on the
REF LEVEL POSITION .
•
With relative reference values for the Y axis, it is possible to enter an absolute threshold
(THRESHOLD) which lowers the relative limit values (see below).
•
The type of limit line (upper or lower limit). With this information and the active limit checking function
(Table
LIMIT LINES , LIMIT CHECK ON , the R&S FSMR checks for compliance with each limit.
•
The limit line units to be used. The units of the limit line must be compatible with the level axis in the
active measurement window.
•
The measurement curve (trace) to which the limit line is assigned. For the R&S FSMR, this defines
the curve to which the limit is to be applied when several traces are simultaneously displayed.
•
For each limit line, a margin can be defined which serves as a threshold for automatic evaluation.
•
In addition, commentary can be written for each limit line, e.g. a description of the application.
Display lines are exclusively used to optically mark relevant frequencies or points in time (span = 0) as
well as constant level values. It is not possible to check automatically whether the marked level values
have been underranged or exceeded.