Document Type thesis Author Name Kiley, Erin M URN etd-050411-142913 Title A Computational Approach to Determining the Intrinsic Impedance of Perforated Metal Sheets Degree MS Department Mathematical Sciences Advisors Prof. Vadim Yakovlev, Advisor Prof. Bogdan Vernescu, Department Head Keywords perforation FDTD impedance Date of Presentation/Defense 2011-05-04 Availability unrestricted
Perforated metal sheets are frequently used in electric and electronic devices, and in most cases, these metal structures should comply with some electromagnetic compatibility constraints which impose certain conditions on penetrating electromagnetic radiation, quality of shielding, and other characteristics. Currently, many issues in electronic system design could be handled with advanced mathematical and computer models; however, direct reproduction of perforation in these models may result in a significantly increased computational cost.
This work is concerned with modeling perforated metal sheets whose apertures have diameters significantly smaller than the wavelength of radiation. We suggest an original approach for computation of intrinsic impedance from the reflection and transmission coefficients obtained by FDTD simulation of the perforated sheet placed in a rectangular waveguide. The calculated impedance can be used to characterize the perforated segment as a solid metal plate which has the same effective material parameters, including electric conductivity.
Functionality of the proposed technique is illustrated with a model of a microwave oven that has two perforated wall segments necessary for ventilation and lighting. After computing the impedance of these segments, they are replaced in the model by solid metal with equivalent effective conductivity, which allows for practical simulation of electromagnetic processes in the oven without any increase in the computational resources required. Computations show that the presence of perforated segments on the walls of this microwave oven makes a negligible impact on the frequency characteristics of the systemâ€”so in corresponding full-wave models, the segments can be replaced by solid metal walls without compromising accuracy of simulation.
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