The matching of the impedances of the parts of a system to ensure optimum conditions for transfer of power from one part of the system to another.

The maximum power is transferred from an amplifier to a load if the load impedance is made the conjugate impedance of the amplifier output impedance at low frequencies where geometries are small.

A nonuniform filter will transmit a wave undisturbed provided that the iterative impedance of each filter section is made equal. If the iterative impedances of the sections are different, loss of power output occurs due to reflections of the wave occurring at the junctions. A small section terminated in its image impedances, where one impedance equals the iterative impedance of the filter sections and the other the load impedance, may be used to match the load to the filter.

Reflections of wave power in a transmission line are eliminated by making the load impedance equal to the generator output impedance, and the line impedance of the transmission line equal to both the above impedances.