Proceedings Article | 5 July 1995
KEYWORDS: Scattering, Backscatter, Polarization, Electromagnetic scattering, Radar, Antennas, Electromagnetic radiation, Geometrical optics, Diffraction, Rayleigh scattering
We review techniques to analyze the backscattering cross-sections of plane electromagnetic waves of wavelength (lambda) returned from cylinders of finite length. The various appropriate techniques yield considerably different results depending on the values of two physical ratios, 2b/(lambda) and a/(lambda) , where 2b is the cylinder's length and 'a' is its radius. The relevant regions are those for which 2b/(lambda) is either much larger than, near to, or much smaller than unity, while at the same time the a/(lambda) ratio is either much smaller than, near to, or much larger than unity. There are thus, nine such regions. Closed- form analytical solutions are not possible in some of those regions, and in many instances the expressions for the cross-section contain unexpectedly cumbersome complexities. These cases are summarized and diplayed in a 2b/(lambda) vs. a/(lambda) plane, in which we indicate the regions where polarization effects are, or are not, significant. The basic technique in the Mie (or resonance) region, a/(lambda) approximately 1, is the exact solution of the governing integral equations. In the Rayleigh (i.e., ka << 1), or in the geometrical optics (i.e., ka $GT$GT 1) regions, we show appropriate low or high-frequency asymptotic approximations. A particular goal of this work is to determine the scattering features or characteristics of thin long rods, normal to perfectly conducting planes, that could model periscopes protruding out of an ideally flat ocean, with a view toward the remote and unambiguous characterization of such objects. The resulting formulas are plotted in various pertinent situations.
