Date of Award

3-1999

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Electrical and Computer Engineering

First Advisor

Peter J. Collins, PhD

Abstract

Infinite periodic structures have been studied heavily because of their efficient filtering capabilities. They generally exhibit sharp frequency roll-offs at the frequency band of interest. In the RF region of the electromagnetic spectrum, periodic structures find applications such as radomes and photonic bandgap materials. Most studies have been done with infinitely periodic arrays because it is convenient to collapse an infinite array into one representative period using Floquet Analysis. Truncating an infinite array introduces an edge and invalidates Floquet analysis over the entire array. This thesis formulates a Finite Element Method (FEM) solution of a semi-infinite periodic array consisting of infinite cylinders. The array elements sufficiently far from the edge are implemented using the concept of a Physical Basis Function (PBF). The PBF concept is based on an a priori knowledge that the amplitudes of the currents in the periodic elements that are sufficiently far from an edge are constant. Implementation of the PBF concept allows the solution domain of the FEM to be bounded by introducing a periodic boundary that represents the truncated portion of the periodic array. The periodic boundary is implemented by relating the fields there with a Floquet phase factor based on one periodic element external to the FEM domain. Performance of the periodic boundary at normal incidence is promising. At off-normal incidence, the implemented boundary performs poorly. Implementation of a periodic boundary by relating the fields there with a Floquet phase factor with one interior periodic element is the next stage in improving off-normal incidence performance.

AFIT Designator

AFIT-GE-ENG-99M-31

DTIC Accession Number

ADA361785

Comments

The author's Vita page is omitted.

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