Scattering from Arbitrary Metal Particles: Using Green's Function Surface Integral Equation Method
Translated title
Spredning fra en Vilkårligt Udformet Metal Partikel: Greens Funktion Overfladeintegralligningsmetode
Author
Risborg, Rasmus Kokholm
Term
4. term (FYS10)
Education
Publication year
2020
Submitted on
2020-06-03
Pages
46
Abstract
Afhandlingen modellerer, hvordan planbølger spredes fra metalpartikler i vilkårlige former uden antagelser om symmetri. Metallet behandles som en perfekt elektrisk leder (PEC), dvs. et idealiseret metal, der reflekterer felter perfekt. Modelleringen bygger på Green’s funktion overflade-integralligningsmetode (GFSIEM), specifikt magnetfeltets integralligning (MFIE). Der udvikles to overfladerepræsentationer: en enkel facetmetode (FM), som tilnærmer overfladen med mange små plane paneler, og en kurvilineær model (CM), som følger den egentlige buede overflade. Begge testes mod den analytiske løsning for en kugle. Resultaterne stemmer godt overens—særligt for CM—men ved korte bølgelængder (høje frekvenser) skal overfladen diskretiseres meget fint for at bevare nøjagtigheden. CM sammenlignes også med en GFSIEM-model, der udnytter cylindrisk symmetri for en stav; begge giver lignende resultater. Endelig diskuteres de ændringer af Green’s funktion, der kræves, når sprederen ligger nær en grænseflade mellem dielektrika frem for i frit rum.
This thesis models how plane waves scatter from metal particles of any shape, without assuming symmetry. The metal particles are treated as perfect electric conductors (PEC), an idealized metal that reflects fields perfectly. The modeling uses the Green’s function surface integral equation method (GFSIEM), in particular the magnetic field integral equation (MFIE). Two surface representations are developed: a simple Facet Method (FM), which approximates the surface with many small flat panels, and a Curvilinear Model (CM), which follows the true curved surface. Both are tested against the analytical solution for a sphere. The results agree well—especially for the CM—but at short wavelengths (high frequencies) the surface must be discretized very finely to remain accurate. The CM is also compared with a GFSIEM model that exploits cylindrical symmetry for a rod, and both give similar results. Finally, the report discusses how Green’s function must be modified when the scatterer is close to an interface between dielectrics, rather than in free space.
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