This chapter introduces the concept of the transmission line (TL) theory, impedance matching, and how the Smith Chart can be used for impedance matching.
7.1 Transmission Line
The sinusoidal steady‐state voltage and current of a TL (as depicted in Figure 7.1) at point of distance d from the load end can be written in cosine‐based phasor form as[P-1]
where and are called the forward(incident)/reflected voltages and currents (each propagating from the source/load to the load/source), respectively. The characteristic impedance Z0 and the propagation constant γ = α + jβ (α: attenuation constant, β: phase constant) are defined as
Figure 7.1 A transmission line (TL) terminated in a load impedance ...
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and 
are called the forward(incident)/reflected voltages and currents (each propagating from the source/load to the load/source), respectively. The characteristic impedance Z0 and the propagation constant γ = α + jβ (α: attenuation constant, β: phase constant) are defined as