We hear the words transmission line all the time and we probably use them everyday, yet what really is a transmission line? A coax cable is a transmission line. A PCB trace in a multilayer board is a transmission line.
Fundamentally, a transmission line is composed of any two conductors that have length. This is all it takes to make a transmission line.
As we shall see, a transmission line is used to transport a signal from one point to another. Figure 7-1 illustrates the general features of all transmission lines. To distinguish the two conductors, we refer to one as the signal path and the other as the return path.
Figure 7-1. A transmission line is any two conductors with length. We label ...