Properties of the forward-scattered incoherent radiation through intense precipitation

Incoherent radiation generally results from a first- or multiple-order scattering process; the first-order process is studied here with particular regard to its effects on large-capacity radio channels. It is shown, in fact, that the first-order scattering cannot be taken into account simply as noise because it generates fluctuations and nonlinearities of the channel transfer characteristic. In particular, the amplitude and phase fluctuations, the distortions, and the two-frequency correlation function are evaluated in the simple case of a slab of uniform precipitation parallel to the incoming wavefront with a receiving antenna pointed towards it. Practical formulas are given, evidencing the role of antenna directivity, distance and depth of the slab, and precipitation scattering properties.