3-28REFLECTIONS ON A TRANSMISSION LINETransmission line characteristics are based on an infinite line. A line cannot always be terminated inits characteristic impedance since it is sometimes operated as an OPEN-ENDED line and other times as aSHORT-CIRCUIT at the receiving end. If the line is open-ended, it has a terminating impedance that isinfinitely large. If a line is not terminated in characteristic impedance, it is said to be finite.When a line is not terminated in Z_{0}, the incident energy is not absorbed but is returned along the onlypath available—the transmission line. Thus, the behavior of a finite line may be quite different from thatof the infinite line.REFLECTION OF DC VOLTAGE FROM AN OPEN CIRCUITThe equivalent circuit of an open-ended transmission line is shown in figure 3-24, view A. Again,losses are to be considered as negligible, and L is lumped in one branch. Assume that (1) the battery inthis circuit has an internal impedance equal to the characteristic impedance of the transmission line(Z_{i }= Z_{0}); (2) the capacitors in the line are not charged before the battery is connected; and (3) since theline is open-ended, the terminating impedance is infinitely large.

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