Quarter-Wave Transformer

Application ID: 12663

Transmission lines are used when the frequency of the electromagnetic signals is so high that the wave nature of the signals must be taken into account. A consequence of the wave nature is that the signals are reflected if there are abrupt changes of the characteristic impedance along the transmission line. Similarly, the load impedance, Z(L), at the end of the transmission line must match its characteristic impedance, Z(0). Otherwise there will be reflections from the transmission line’s end.

A quarter-wave transformer is a component that can be inserted between the transmission line and the load to match the load impedance to the transmission line’s characteristic impedance. This model exemplifies some of the characteristics of a quarter-wave transformer. In particular, the model simulation shows that the transformer only provides matching for one particular frequency, namely that for which the transformer is a quarter of a wavelength long.

This model example illustrates applications of this type that would nominally be built using the following products: