Viavi CAA06M, User Manual

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2-Port Transmission Testing
Introduction
This chapter provides instructions on how to perform the 2-Port Transmission measurement. It is used to
quantify signal gain or loss in a cable or other devices with connecting both ends of the cable or device to
the instrument. Topics discussed in this chapter are as follows:
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Introducing 2-port transmission measurements
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Preparing for a measurement
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Making a measurement
Introducing 2-port transmission measurement
The 2 Port Transmission measures the level of the signal attenuation of passive RF elements such as
cables and filters, or the level of gains of active RF elements such as amplifiers. The frequency band to
measure the characteristics of a cable must be calibrated before performing the insertion loss/gain
measurement.
Gain
The gain is the gain resulting from the insertion of a device in a transmission line, expressed as the ratio
of the signal power delivered to that part of the line following the device to the signal power delivered to
that same part before insertion.
Insertion loss
The insertion loss is the loss of the transmitted signal power resulting from the insertion of a device in a
transmission line. It is usually expressed relative to the signal power delivered to that same part before
insertion. In most systems, insertion loss is introduced by things such as connectors, splitters, or
couplers.
The insertion loss of a device (which may be a whole line) may also be referred to as attenuation. Line
terminations play an important part in the insertion loss because they reflect some of the power. Apart
from this, it is clear that not all of the power that is sent in to the line at one end appears at the other. This
is because of radiation losses, resistive losses in the conductor as well as losses in the surrounding
dielectric. The loss resulted from inserting a transmission line between a source and a load is called the
insertion loss of the line.