User`s guide

Evaluating Your Measurement Results 14
Agilent E5505A User’s Guide 337
Problem Solving
Discontinuity in the graph
Because noise distribution is continuous, a break in the graph is evidence of a
measurement problem. Discontinuity in the graph will normally appear at the
sweep-segment connections.
Table 52 identifies the circumstances that can cause discontinuity in the
graph.
Table 51 List of topics that discuss problem solving in this chapter
If you need to know: Refer to:
What to do about breaks in the noise graph Discontinuity in the Graph
How to verify a noise level that is higher than expected High Noise Level
How to verify unexpected spurs on the graph Spurs on the Graph
How to interpret noise above the small angle line Small Angle Line
Table 52 Potential causes of discontinuity in the graph
Circumstance Description Recommended Action
Break between segments where
closely spaced spurs are resolved in
one segment but not in the next.
Closely spaced spurs that are
resolved in one sweep-segment but
not in the next can cause an
apparent jump in the noise where
they are not resolved.
Use the Real-time Monitor to evaluate the
noise spectrum at the break frequency on
the graph. To eliminate the break in the
graph, you may find it necessary to change
the Sweep-Segment Ranges so that the
measurement resolution remains constant
over the frequency range where the spurs
are located.
Erratic Noise: One or more
segments out of line with the rest of
the graph.
This occurs when the noise level of
the source being used is
inconsistent over time. The
time-varying noise level causes the
overall noise present when one
segment is being measured to differ
from the level present during the
period when the next segment is
measured.
Repeat the noise measurement several
times for the segment that does not match
the rest of the graph, and check for a
change in its overall noise level.