Using Limit Lines
R&S FSH
1145.5973.12 4.118
E-11
Using Limit Lines
Limit lines are used to set limits for level characteristics versus time or versus frequency on the screen;
they must not be exceeded. For instance, the upper limits of permissible spurious or harmonics of a
DUT are marked by limit lines. In the R&S FSH, the upper and lower limit value can be preset by way of
limit lines. Thus, a spectrum or level characteristic in the time domain (span = 0 Hz) can be checked
either visually on the screen or automatically by verifying limit violations.
A limit line consists of at least two and at most 25 value pairs (points) on the x axis (frequency, time or
length) and the y axis (level). The R&S FSH links the individual points by straight lines. The values on
the x axis may be specified in absolute units (e.g. frequency in MHz) or relative units referenced to the
center of the measured trace (e.g. center frequency). Relative units are of advantage, for instance,
when modulated output signals are measured. If the center frequency is varied, the mask on the screen
remains unchanged. The points on the y axis are always dB values. If the scale on the y axis is linear
(unit V or W), the R&S FSH automatically switches to the respective dB unit after a limit line has been
switched on.
Limit lines are defined with the aid of control software FSH View. They are loaded into the memory of
the R&S FSH via the RS-232-C interface. Up to 100 limit lines can be stored simultaneously in the
R&S FSH memory. The maximum number of limit lines may be reduced if transducer factors, channel
tables, cable models, or data sets are stored simultaneously (see "Saving and Loading Instrument
Settings and Measurement Results" in this chapter )
Operating sequence:
Press the MEAS key.
Press the LIMIT LINES softkey.
The softkey menu for the control of limit lines is
displayed on the screen.
N.B
:
Limit lines cannot be used for
measurements with the Power Sensor
R&S
FSH-Z1. In this case the LIMIT
LINES softkey is blanked.
The R&S FSH makes a distinction between upper limit lines (UPPER LIMIT) and lower limit lines
(LOWER LIMIT). It checks whether a measured value is above the upper limit line or below the lower
limit line. The limit lines stored in the R&S FSH can be used to mark both upper and lower limit values.
