The effect of turbulent atmosphere on backscattered waves

In radar detection of targets the backscattered waves are traveling through the same region as the incident wave. When the region is occupied by a turbulent atmosphere, the backscattered wave is therefore expected to be correlated with the incident wave. As a matter of fact, these two oppositely traveling waves are related through a reciprocity theorem. This reciprocity theorem is shown to be valid by using the Feynman path integral solution of the parabolic equation. For the problem at hand the path integral is just the propagator which enters naturally in calculations of the mutual coherence function. This mutual coherence function is evaluated for several cases: when the incident wave is a narrow or broad beam wave, and when the target is a single point or a random reflecting screen with finite correlation size. The aperature averaged mutual intensities are also evaluated. The results show that under certain conditions the backscattered power can be intensified to above the free space value. The turbulent atmosphere can also broaden the apparent target size under some other conditions. These and other results will be presented and discussed in the paper.