70940

Cocordinates and notation again

Wc considcr thc bchaviour of a transmission linc terminated as shown in Figurę 2.6 in a

resistance Zl.

It might appear incongruous that we have chosen to represent what is a resistance by the symbol Zl which is normally an indication of an impedance. The reason for this choice of notation is that we will encounter in a later section dealing with the analysis of transmission lines in the sinusoidal steady State, concepts and equations very similar to those being uncovered here. It is common to borrow from that different context the notation used thercin although there is a certain inappropriateness in doing so.

Thus, if Vrat thc load is known. we can calculate Vr. Notę that whcn Zl= Zo

there is no reflection. This occurs when the linę is terminated in a resistance equal to

its

characteristic impedance.

Notę that although we have not explicitly shown the arguments of Vtand Vr, Vtis a function of z -ctand Vris a function of z + ct. The equation just quoted has been obtained by cxamining conditions at thc load, and thus applies for the particular position

z = L, but for any time.