In a receiving system, the polarization of the antenna and the incoming wave
need to be matched for maximum response. If this is not the case, there will be
some signal loss, known as polarization loss. For example, if there is a vertically
polarized wave incident on a horizontally polarized antenna, the induced voltage
available across its terminals will be zero. In this case, the antenna is cross-polarized
with an incident wave. The square of the cosine of the angle between
wave polarization and antenna polarization is a measure of the polarization loss.
It can be determined by squaring the scalar product of unit vectors representing
the two polarization.