Electromagnetic scatter from small dielectric gradients in a continuous medium

A new approach is presented to the formulation and understanding of the problem of electromagnetic scatter from a slightly perturbed continuous medium. The problem is expressed in terms of periodic functions instead of conventional power series. From this formulation, specular properties are observed that are not obtainable from older considerations. The approach was verified with a laboratory experiment using microwave transmission lines with length-dependent, slowly varying dielectric cross sections. Further experiments were carried out using backscatter from a radar designed to detect clear air turbulence. The primary result shows that a turbulent medium can be replaced for the purposes of scatter calculation by a structure of finite periodicities because the medium acts as a lumped insertion loss, the stopping characteristics being determined by a spectral scale in the turbulence. The formulation defines the limits of knowledge about the medium and shows that, although it is not unique, some knowledge of the structure is obtainable. Insight is gained into the work needed to understand and interpret remote probe experiments.