Abstract: The statistical characteristics of the instantaneous polarization projections (IPP) of partially polarized waves are studied on the basis of the theory of instantaneous polarization.A novel concept of the distance between an IPP and an expected polarization track is presented.It is essentially a measure of the distance between two polarization signals' IPPs in the metric space.Under the normal hypothesis, the probability density function (PDF) of this distance is derived.It's also proved that this distance obeys the normal distribution approximately when the number of the samples of a partially polarized wave is large enough. These results are of great importance to polarization signal detection, estimation and filtering.

Key words: partially polarized wave, instantaneous polarization projection, probability density function, instantaneous polarization