Relative Limit Lines; Build From Trace - Keysight N9923A FieldFox User Manual

 Press <Back to return to the Limit menu.

Relative Limit Lines

Relative limit lines are X/Y coordinates that are referenced to the center frequency
(X-axis) and Reference level (Y-axis).
Use relative limits to test devices or signals that are identical except for the center
frequency or amplitude. With relative limit lines in place, you change the center
frequency of the measurement and the limits look as though they are in the same
location.
The same is true for Reference Level. When you expect to measure a different power
level, instead of changing the Y-axis value of all of the fixed limits, simply change to
relative limits. The limits will then remain a constant Y-axis distance from the
Reference Level.
Each limit line can be changed at any time from Fixed to Relative, and Relative to
Fixed.
How to Create a Relative Limit Line
The easiest way to create a Relative limit line is to create a Fixed Limit at a specific
center frequency and reference level. Learn how on page 118. Then change the limit
line to Relative. The X/Y data points will be re-calculated relative to the center
frequency and reference level.

Build From Trace

A limit line can be built from an existing trace. One X/Y point is made from each
measured data point. Then, using an offset value, you can shift the limit line UP for
upper limits or DOWN for lower limits.
Once limit lines have been built from the trace, changes that you make to the trace,
such as frequency range, do NOT change the limits. However, the limit line
properties can be edited just like standard limit lines.
A lower limit line (red) built from the trace (yellow) shifted down 5 dB.
How to Build Limit Lines from a Trace
NOTE Build from Trace is NOT allowed for traces with more than 1001 data points.
 Select the trace from which limits will be built.
 Press Limit 8.
120 FieldFox User's Guide