Transient Electromagnetic Scattering of a Metallic Object Buried in Underwater Sediments
| Autor: | Douglas W. Oldenburg, Lin-Ping Song, Leonard R. Pasion, Stephen Billings |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
Physics
business.industry Scattering 0211 other engineering and technologies 02 engineering and technology 010502 geochemistry & geophysics 01 natural sciences Integral equation Gradiometer Computational physics Optics General Earth and Planetary Sciences Waveform Transient (oscillation) Electrical and Electronic Engineering Antenna (radio) Underwater business Magnetic dipole 021101 geological & geomatics engineering 0105 earth and related environmental sciences |
| Zdroj: | IEEE Transactions on Geoscience and Remote Sensing. 54:1091-1102 |
| ISSN: | 1558-0644 0196-2892 |
| DOI: | 10.1109/tgrs.2015.2473851 |
| Popis: | In this paper, we study the electromagnetic scattering of a conducting and permeable sphere buried in sea sediments. Instead of taking a uniform conducting medium in the previous work, we model marine environments as a layered medium that consists of the air, the sea, and the sediment. We adopt an integral equation technique to compute time-harmonic solutions for background and scattered fields under fundamental source excitations, i.e., vertical and horizontal magnetic dipoles. The corresponding transient scattering responses to causal step waveform are computed through the digital sine transform. The derived fundamental solutions provide convenient formulas tailored for three-layer medium modeling. The numerical experiments demonstrate that the scattered responses computed in the different backgrounds are approaching almost to the same decays at late times. However, the background fields can significantly mask the scattered responses. Subtracting assumed uniform background responses from “measured” total fields in the three-layered medium cannot provide a correct scattering response in the interested time range, i.e., 0.1–25 ms. To remove the background fields, we propose a conceptual gradiometer system that has receiver cubes installed radially symmetric with respect to a transmitting antenna. The results demonstrate that the suitable differential combinations are able to yield the scattering responses that well agree with those of a free space as the layered background fields in these combined receivers are equal and their influence are automatically canceled out. |
| Databáze: | OpenAIRE |
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