 The voltage (formula_30) across the terminating impedance (formula_31), may be calculated by replacing the output of the line with an equivalent generator (figure 4) and is given by

The reflection, formula_33 must be the exact amount required to make formula_34,

The reflection coefficient, formula_36, is defined as

and substituting in the expression for formula_33,

In general formula_36 is a complex function but the above expression shows that the magnitude is limited to

The physical interpretation of this is that the reflection cannot be greater than the incident wave when only passive elements are involved (but see negative resistance amplifier for an example where this condition does not hold).For the special cases described above,

When both formula_10 and formula_44 are purely resistive then formula_36 must be purely real.In the general case when formula_36 is complex, this is to be interpreted as a shift in phase of the reflected wave relative to the incident wave.