Abstract
The composite electromagnetic (EM) scattering characteristics of low-altitude target above valley composite rough surface are studied. The composite rough surface modeling theory is adopted to simulate the natural cavity structure of valley environment. Aiming at efficiently and accurately calculate the composite EM scattering from low-altitude target above valley environment, a hybrid method combining shooting and bouncing ray (SBR) technique and equivalent edge currents (EEC) method is proposed, in which SBR method based on the ray-density normalization (RDN) is applied to consider the multiple interactions between target and environment, and EEC method meliorates target's edge diffraction. Numerical examples illustrate the efficiency and validation of proposed hybrid method. Finally, based on the hybrid SBR-EEC method, the EM scattering characteristics of low-altitude target above valley environment are further investigated to show scattering mechanisms of this composite model and provide some useful conclusions through physical phenomena.
Highlights
In recent years, study on electromagnetic (EM) scattering characteristic of target with cavity structure has been a concerned focus in computational electromagnetism
We review the weighted inverse tangent function for valley environment [29], whose expression is shown as follow: fvalley(x, y) = w1 · [fgro(x, y) + Hgro] + w2 · fsea(x, y) w1 = [π/2-arctan(ax + bLx − y2)]/π w2 = [π/2+arctan(ax + bLx − y2)]/π where fgro(x, y), fsea(x, y) and fvalley(x, y) present the surface profile distribution of ground rough surface, sea surface and valley composite rough surface, respectively; w1 and w2 present the weighted factors; Hgro denotes the depth factor which controls the depth of valley; Lx denotes the length of total surface along x-axis direction; a and b present the width factor and length factor which are used for changing the opening width and valley length of the valley composite rough surface
The formulations and basic theory of the hybrid shooting and bouncing ray (SBR)-edge currents (EEC) method is presented and some numerical examples are provided to verify the validation of this hybrid algorithm
Summary
Study on electromagnetic (EM) scattering characteristic of target with cavity structure has been a concerned focus in computational electromagnetism. The SBR has evolved into a standard method to calculate the scattering problems of object with cavity structure. These research achievements show the efficiency and diverse applications of SBR Most of these achievements focus on the study of scattering from target with carved surface or cavity structure. When target is located above valley environment, multiple interactions between target and natural cavity structure will have tremendous impact on target’s scattering characteristic For this kind of environment, our research group has done several tentative works, e.g., the modeling for water zone embedded in land surface [19] and the adjacent region between ground and near sea [20]. THE SHOOTING AND BOUNCING RAY BASED ON RAY-DENSITY NORMALIZATION We adopt the triangular facets to simulate the surface of lowaltitude target and valley environment.
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