Mutual coherence functions and intensities of backscattered signals in a turbulent medium

The effect of a turbulent medium on the backscattered signal is investigated. Since the backscattered signal is traveling in the same medium as the forward incident signal, coherence between these oppositely propagating waves is expected. This coherence can be treated by using a reciprocity theorem applied to the propagator. In this paper the mutual coherence functions and the aperture-averaged intensities are calculated under the saturated regime. Because of the presence of turbulence, changes from the respective free space value in both intensity and beam size can occur. For example, enhancement in the backscattered intensity is most likely to occur for narrow beams, while a large reduction in intensity is expected in the limit of small irregularities. In general, the backscattered intensity and beam size depend on the interplay of four scales: the irregularity size, the size of the scattering body, the size of the electromagnetic beam, and the Fresnel size. Formulas have been derived to show this dependence.