Electrodynamic Similitude and Physical Scale Modeling. Part 1. Nondispersive Targets.
Abstract
This report presents a complete and rigorous treatment of the predictions of electro-dynamic similitude relating scattering from scaled targets to scattering from full-size targets. The assumption is made that the targets' conductivity, permittivity, and permeability do not change with frequency. Three general nonlinear modeling equations in six variables are derived, and a complete set of solutions is presented. Particular emphasis is given to the effects of differences between geometric and complete scaling on the electromagnetic fields and on the radar cross section, and effects of approximations to complete scaling are evaluated. Conditions are obtained on properties of materials required for models made from these materials to accurately simulate systems. Absorption and energy balance are also treated, and the influence of finite conductivity on surface currents is shown. The possibility of using scaled down models of real targets is usually based on the linearity of Maxwell's equations. The physics involved in linearity, its relation to the Maxwell equations in macroscopic media, and its impact on physical scale modeling is examined. The behavior of electromagnetic fields was examined as a function of frequency. Upper bounds on the electric conductivity and limitations on the electric and magnetic polarizability of realistic materials may have profound implications for model measurements. All the energy density in the reflected wave may be lost at higher frequencies by incomplete scaling of even apparently nonabsorptive targets. Thus, the ratio of measured radar cross sections of geometrically scaled targets to those predicted for a completely scaled model will eventually approach zero.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1986
- Accession Number
- ADA167467
Entities
People
- Clifford R. Schumacher