The vector ratio of the current, I, delivered to a load of impedance Z_B by a source of impedance Z_A when the impedances are not matched, to the current, I₀, delivered to the load when the impedances are matched by an impedance matching network of image transfer constant, θ, equal to zero (see diagram). The reflection factor is thus the ratio of the current delivered to an unmatched load to the current that would be delivered to a perfectly matched load. It is given by

The ratio of the electrical powers in Z_B for these matched and unmatched cases is also given by I/I₀. The reflection loss between Z_A and Z_B is the ratio of the powers in Z_B expressed in decibels, i.e. it is given by

If the reflection loss is negative it represents a reflection gain in the system. Compare reflection coefficient.

Reflection factor