新型表面擇頻元件之設計：分析與計算
Date Issued
2005-07-31
Date
2005-07-31
Author(s)
DOI
932212E002080
Abstract
Because of the filtering property suggested, two-dimensional periodic screens which were
named the frequency selective surfaces (FSS) have attracted a great deal of attention for many
years and have been found various applications, such as band-pass radomes, reflectors of antenna
system, polarizers and so on. The frequency response of FSS highly depends on the
configurations and spacing of the elements as well as on the thickness and permittivity of
dielectric layers that may be part of the screens.
When an incident field propagates through FSS, surface currents will be induced on the
conducting screens and then, in turn, radiate a scattered field. In this thesis, we employ the
spectral Galerkin method to analyze the scattering phenomena of the FSS. In the spectral domain,
Floquet’s theorem allows the induced surface currents to be expressed in terms of a Fourier series
and reduces the computation domain from an infinite array into a single cell. For the FSS with
multilayered structures, we also employ the spectral immitance approach to derive the spectral
dyadic Green’s functions which relate the induced surface currents to the scattered field.
Moreover, to be more feasible for analyzing FSS with complex configurations, the subdomain
basis functions are adopted to expand the induced currents. Although that will increase the
number of unknowns, the computation speed can be improved by using a fast Fourier transform
based iterative approach (the conjugate gradient method, FFTCG). After the distribution of the
induced surface currents is determined, the spectral scattered fields can be found. Finally, we can
express the reflection and transmission coefficients at different Floquet modes in terms of the
spectral scattered fields at the top and bottom surfaces of the FSS.
Results for the free-standing and the single-layered-dielectric FSS with various geometries
are presented, and are compared with existing results to check the correctness of our
programming. In addition, some parameters, such as the configurations of the conducting screens,
the thickness and the permittivity of the dielectric layers, which describe the structure of the FSS
are varied to investigate the resultant effects on the frequency response.
Publisher
臺北市：國立臺灣大學應用力學研究所
Type
report
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