In the previous chapter we reviewed static electric fields due to stationary charge distributions, and static magnetic fields, due to the charges moving at constant speed, i.e. dc currents.

A transmission line can be modeled as a distributed parameter circuit consisting a series of small segments of length Δz, as shown in Figure 17.1

The distributed parameters describing the transmission line are:

r – resistance per‐unit‐length (Ω/m)

l – inductance per‐unit‐length (H/m)

g – conductance per‐unit‐length (S/m)

c – capacitance per‐unit‐length (F/m)

The transmission line model in Figure 17.1 describes a lossy transmission line. To gain an insight into transmission line theory it is very helpful to consider a lossless transmission line first. Such a transmission line is shown in Figure 17.2.

To obtain the transmission line equations let’s consider a single segment of a lossless transmission line shown in Figure 17.3.

Writing Kirchhoff’s voltage law around the outside loop results in

(17.1)

or

(17.2) ...

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