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Transition Loss

As has been mentioned elsewhere, electric transducers, such as the networks considered in this chapter, must pass electric signal energy from one network to the next, etc. As shown on pages 71 and 152, the ability to pass energy from one network to the next depends on the impedance relations at the network junctions. If the output impedance of one network is not related correctly to the input impedance of the next network, then conditions for maximum power transfer will not exist, and a transmission loss or loss, defined1 as "a term used to denote a decrease in power in transmission from one point to another," will be encountered.

Maximum possible power transfer between two circuits has been shown to occur when the impedances involved were conjugates. The transition loss in transferring power from one circuit to another is a comparison of the power that is transferred under actual circuit conditions to the power that would be transferred if the load impedance and the source were conjugates.

Transition loss is not widely used in studying circuit performance. One reason is that communication equipment is built in a particular way for reasons other than impedance considerations, and the inherent impedances of the equipment often cannot be altered at will. Also, as will be made clear in Chapters 6 and 7, lines and cables should be terminated in load impedances having the same magnitudes and angles as their characteristic impedances.

Figure 20. Circuit for studying reflection loss.

Last Update: 2011-05-30