3-6 PN: 10580-00321 Rev. M S331L UG
3-3 Overview Cable and Antenna Measurements
Line Sweeping
System performance issues are seen in two ways: excessive reflections
(more common) caused by impedance mismatches or excessive insertion
losses (less common) caused by energy dissipated in the connectors or
cables.
The two measurements used to determine communication system
performance are:
• Return Loss or Standing Wave Ratio (SWR) for reflections and
• Cable Loss (Insertion Loss) for insertion losses.
It is important to remember that Return Loss and VSWR are typically
Pass/Fail tests. They both measure reflection but display the results in
different ways. For either measurement, set a limit line to the
specification determined by the carrier and make the measurement.
If the ENTIRE frequency range swept is below the line the test passes.
If ANY part of the sweep is at or above the limit line the test fails.
With a failed test, one or more components is at fault. Distance to Fault
mode is used to find the problem Figure 3-4 shows a failed Return Loss
measurement with the pass/fail limit line and Figure 3-5 on page 3-7 is
a Distance to Fault measurement of the same system.
Figure 3-4. Failed Return Loss Measurement
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