3-d simulations for radar cross-section reduction using plasma absorbers

Summary form only given. Radar cross section (RCS) is the measure of a target's ability to reflect radar signals in the direction of the radar receiver. A collisional unmagnetized plasma, surrounding the target, acts as a good absorber of electromagnetic waves over a wide frequency range, reducing its RCS. This has given rise to world wide interest in plasma stealth technology. We have performed 3-D finite difference time domain (FDTD) simulations for calculating electro-magnetic wave scattering and absorption due to plasma-shielded objects. We have earlier validated our 3-D calculations against experimental results for wave scattering from a plasma-shielded metallic plate. Those simulations yielded a reasonable match with experimental measurements. That study also showed that bending of waves inside plasma due to density gradients plays as important a role as absorption. Those results have major implications for plasma stealth applications, which have heretofore assumed that plasma absorption is the main mechanism. We have also compared two techniques for studying the bending/refraction of electromagnetic energy flow through a plasma with spatial density gradients. These are the accurate FDTD method and the much faster, albeit more approximate, ray-tracing method. Our earlier work focused on the near-field region. The RCS refers to far-field measurements. In this paper, we present actual far-field (RCS) results for objects with generic shapes, such as flat plates, cylinders and spheres, both with and without plasma shielding. In this paper, we also report on the dependence of bistatic RCS on plasma parameters, such as the peak electron density, the spatial profile of density and the collision frequency. Finally, we provide a physical interpretation for the results. Such an interpretation is only possible using the detailed spatio-temporal evolution of electromagnetic fields that is provided by the FDTD method. To our knowledge, this is the first detailed three dimensional calculation of plasma-based RCS reduction for real-life objects