Simulation of Terahertz Antennas in Free Space and on Dielectric Substrates using the Green's Function Surface Integral Equation Method
Authors
Christensen, Josefine Marianne ; Simonsen, Daniel Runason ; Schøler, Frederik Tind
Term
4. term (FYS10)
Education
Publication year
2021
Submitted on
2021-06-03
Abstract
This thesis investigates numerical modeling of terahertz antennas by formulating scattering from perfect electric conductors (PECs) using the Green’s Function Surface Integral Equation Method (GFSIEM), a method‑of‑moments approach. Antenna surfaces are discretized with triangular finite‑element patches and represented by piecewise polynomial currents, and dyadic Green’s functions for homogeneous and layered media are derived to treat both free space and substrates. The implementation is validated against the analytical solution for a PEC sphere by comparing surface currents and far‑field quantities. The method is then applied to box‑shaped PEC scatterers with rounded edges, first in free space and then placed on an infinitely extended silicon layer, to compute surface currents and the differential scattering cross section (DSCS). Configurations with single and multiple scatterers are analyzed, including resonance behavior and far‑field patterns. Across these cases, the simulations reproduce surface currents and DSCS with good accuracy, while showing limitations at short wavelengths. The results indicate that GFSIEM is a useful approach for analyzing terahertz antenna geometries in free space and on dielectric substrates.
Denne afhandling undersøger numerisk modellering af terahertz‑antenner ved at beskrive spredning fra perfekte elektriske ledere (PEC) med Green’s funktion overfladeintegralligningsmetoden (GFSIEM), også kendt som en metode‑af‑momenter tilgang. Antennernes overflader diskretiseres med trekantede finit‑elementer og stykvise polynomielle strømme, og dyadiske Green’s funktioner for homogene og lagdelte medier udledes for at behandle både frit rum og substrater. Implementeringen valideres mod den analytiske løsning for en PEC‑kugle ved at sammenligne overfladestrømme og fjernfelter. Metoden anvendes derefter på boksformede PEC‑spredere med afrundede kanter, først i frit rum og siden på et uendeligt udstrakt siliciumlag, for at beregne overfladestrømme og det differentielle spredningstværsnit (DSCS). Konfigurationer med enkelte og flere spredere analyseres, herunder resonansadfærd og fjernfeltmønstre. På tværs af disse tilfælde genskaber simuleringerne overfladestrømme og DSCS med god nøjagtighed, men med begrænsninger ved korte bølgelængder. Resultaterne peger på, at GFSIEM er en brugbar tilgang til analyse af terahertz‑antennegeometrier i frit rum og på dielektriske substrater.
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