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Step Action
Description
7.
Note: Job ID field
identifies Job ID and
creates a folder to
save the result by
the same name.
Default location is
JOB folder under
disk.
8.
Tap
to save
the trace in .sor
format. Tap
to save the trace in
.sor and .pdf format.
5.6
Cable and Antenna Testing
5.6.1 Return Loss, VSWR and Distance to Fault Overview
Return loss is a measure of VSWR (Voltage Standing Wave Ratio), expressed in decibels (db). The return-loss
is caused due to impedance mismatch between two or more circuits. For a simple cable assembly, there will
be a mismatch where the connector is mated with the cable. There may be an impedance mismatch caused
by nick or cuts in a cable. Also, the material properties as well as the dimensions of the cable or connector
plays important role in determining the impedance match or mismatch. A high value of return-loss denotes
better quality of the system under test (or device under test). For example, a cable with a return loss of 21
db is better than another similar cable with a return loss of 14 db, and so on.
Voltage Standing Wave Ratio simply put is the ratio of the maximum to the minimum voltage of a standing
wave (which is the instantaneous sum of incident and reflected waves). Ideally, 100% of the incoming signal
should pass through the component without any reflection, in which case, there would be no standing
wave (1:0). A 1:5 VSWR (or mismatch) equals a return loss of 13.98dB for example.