Electromagnetic Radiation Inverse Scattering
Abstract
The report is divided into four parts. Part one is about nonlinear microwave amplification and the further use of nonlinear Schroedinger equations to model amplifiers. Part two is about speeds of frequency components of electromagnetic pulses, and a related inversion method. Our numerical computation of precursors shows that damping increases the speed of frequency components to a degree that is consistent with energy velocity. The speed up here is slight, and a medium that has been called 'highly absorptive' exhibits no speed up. These small effects lead us to question the extent to which energy velocity would be more useful than group velocity in the laboratory. We also introduce an especially simple method for measuring permittivity. Part three is about an inversion method for depth-dependent dispersive objects that are flat, and whose properties vary only with depth. Tissue and soil are discretely layered examples of such media. But this paper's algorithm also applies to dispersive media that are continuously layered. A time domain layer stripping method that uses wave splitting and Krueger-Ochs Green functions is presented. Part four is about general rules of pulse propagation in dispersive media, with applications to inversion. We develop some new methods for describing pulse propagation for general dispersive media, using a Debye model for water as an example. Short pulse, long pulse, short time, and long time approximations are presented. We explain a factor of nine effect in the speed of waves in water, which seems to have been previously unnoticed. We provide sharp tipper bounds for the propagated amplitude and reduce the computation of those bounds to a calculator exercise. These bounds may be useful in controlling the electromagnetic interference on damage produced in dispersive media.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1997
- Accession Number
- ADA340974
Entities
People
- Thomas Roberts