Material Surface Design to Counter Electromagnetic Interrogation of Targets

Abstract

Utilization of controllable ferroelectric and ferromagnetic layers coating a conducting object to provide an attenuation capability against electromagnetic interrogation is discussed. The problem is formulated as a differential game and/or a robust optimization. The scattered field due to interrogation can be attenuated with the assumption of an uncertainty in the interrogation wave numbers. The controllable layer composed of ferromagnetic and ferroelectric materials [9, 10] is incorporated in a mathematical formulation based on the time-harmonic Maxwell equation. Fresnel's law for the reflectance index is extended to the electromagnetic propagation in anisotropic composite layers of ferromagnetic and electronic devices and used to demonstrate feasibility of control of reflections. Our methodology is also tested for a non-planar geometry of the conducting object (an NACA airfoil) in which we report our findings in the form of reduced radar cross sections (RCS).

Static two-player evasion-interrogation games with uncertainty

“…GROVE, K. ITO and J.A. TOIVANEN 291 fields from an object such as an airfoil or missile and can be computed in one of several ways [8,9]. The simplest is the reflection coefficient based on a simple planar geometry (e.g., see Figure 1) using Fresnel's formula for a perfectly conducting half plane which has a coating layer of thickness d with dielectric permittivity and magnetic permeability μ.…”

“…In [8] the authors demonstrated that it is possible to design ferroelectric materials with appropriate dielectric permittivity and magnetic permeability to significantly attenuate reflections of electromagnetic interrogation signals from highly #688/06. Received: 01/IX/06.…”

“…From the combined results of [8,9] it is thus rather easily concluded that the evader and the interrogator must each try to confuse the other by introducing significant uncertainty in their design and interrogating strategies, respectively. This concept, which we refer to as mixed strategies in recognition of previous contributions to the literature on games (von Neumann's finite mixed strategies to be explained below), leads to two player non-cooperative games with probabilistic strategy formulations.…”

A fast iterative solver for scattering by elastic objects in layered media

“…The preconditioning of discretized scattering problems in layered media without an object has been considered in [8,9,24,25,28], for example, and with an object in [17]. The domain decomposition method introduced in [13] and employed in [3] for computing electromagnetic scattering by coated objects is based on a similar approach to the one considered in here. In [13] the electromagnetic scatterer is perfectly conducting with a dielectric coating layer which would corresponds to a sound-soft acoustic scatterer with a coating layer having different density and speed of sound.…”

“…We present numerical results on scattering by an aluminum disk with one feet diameter and the center at (0 m, −0.2524 m). The density of aluminum is 2700 kg/m3 and its compressional speed and shear speed are c c = 6568 m/s and c s = 3149 m/s, respectively. The surface of the sediment is defined by x 2 = f (x 1 ) = (0.0368 m) cos(360 • x 1 /(0.75 m)).…”