Backscatter from gated fluctuating regions: A Bremmer series approach

In many monostatic configurations, the effective scattering volume is defined longitudinally by the radar gating and transversely by either the antenna beamwidth or the extent of the scattering region. Often the radar signal must traverse fluctuating transmission regions on its way to and from the range cell. Consequently, the return signal is perturbed not only by events within the range cell but contains statistical characteristics ascribable to the fluctuating transmission path as well. The limit of large-scale fluctuations (which is of interest in the current context) is dominated by strong incoherent small angle scattering. A systematic analytic sequence resembling that pursued by Bremmer [1] (though significantly complicated by the three dimensionality and temporal dependence of the fluctuations) constitutes the main subject matter of this study. The proposed iterative scheme, while properly accounting for multiple small angle scatter, orders successive iterates by the number of large angle scattering events they represent. While the discussion is carried within the physical framework of an electromagnetic (radar) application, an extension to the acoustical (sonar) analog is simple. Furthermore, the extension of the presently investigated monostatic configuration to bistatic ones is possible but is by no means trivial. The reported work has initially been motivated by an attempt to interpret on board radar cross section and spectre measurements associated with an ionized wake.