There are a variety of terminations for RF lines. Each termination has an

effect on the standing waves on the line.

A transmission line can be terminated in its characteristic impedance as an

open- or short-circuit, or in capacitance or inductance.

Whenever the termination on a transmission line is not equal to Z0, there are

reflections on the line. The amount of voltage reflected may be found by using

the equation:

(

)

RL -ZO

ER = Ei

RL +ZO

When the termination on a transmission line equals Z0, there is no reflected

voltage.

The measurement of standing waves on a transmission line yields

information about operating conditions. If there are no standing waves, the

termination for that line is correct and maximum power transfer takes place.

The standing-wave ratio is the measurement of maximum voltage (current)

to minimum voltage (current) on a transmission line and measures the

perfection of the termination of the line. A ratio of 1:1 describes a line

terminated in its characteristic impedance.

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