ABSTRACT
Weak scattering occurs when the incident wave is only “scattered” once, and this incident wave basically undergoes very little perturbation as it travels through or interacts with the target . This is significant in that in most of these cases the wave inside the target can generally be approximated as the incident wave, which allows the problem to be linearized in order to find a solution . This approximation is what is exploited in the approach to the solution used in the Born and Rytov approximation methods (Avish and Slaney, 1988; Lin and Fiddy, 1990) . In these approaches, by linearizing the problem, one is able to establish a Fourier relationship between the measured scattered field data and the target or scattering function . In principle, these methods are only supposed to work well with weak scatterers due to the dependence on this approximation . More precisely, the Rytov approximation requires targets whose permittivity or index varies only very slowly on the scale of the wavelength . This concept of weak scattering will be examined, and in some sense challenged, in this research to understand the extent to which these methods actually work . In the case of strong scatterers, the field inside the target is scattered multiple times and can incur significant perturbation that introduces nonlinearities to the integral equation of scattering (Chew, 1995) . This negates the linear approach to this problem, making it quite difficult to solve if and when the above-mentioned methods do not perform well . A solution for the problem involving strong scattering is highly desired, as most targets of interest in real life would fall into this category .
