By using orthogonal polarizations, two independent information channels using the same carrier frequency can be transmitted over a single link. While the orthogonally polarized channels are completely isolated in theory, some degree of interference between them is unavoidable owing to the non-perfect polarization characteristics of the antennas and depolarizing effects on the propagation path. The main sources of this cross-polarization at centimetre and millimetre wavelengths are hydrometeor absorption and scattering.