A Near-Zone to Far-Zone Transformation Process Utilizing a Formulated Eigenfunction Expansion of Spheroidal Wave-Harmonics

In the field of antenna design and analysis, often the need arises to numerically extrapolate the far-zone performance of a radiating structure from its known (or assumed known) near-zone electromagnetic field. Mathematical processes developed to accomplish such a task are known in the literature as near-zone to far-zone transformations (NZ-FZTs) as well as near-field far-field (NF-FF) transformations. These processes make use of sampled near-zone field quantities along some virtual surface, viz., the transformation surface, that surrounds the radiating structure of interest. Depending upon the application, samples of the required near-zone field quantities are supplied via analytical, empirical, or computational means. Over the years, a number of NZ-FZT processes have been developed to meet the demands of many applications. In short, their differences include, but are not limited to, the following: (1) the size and shape of the transformation surface, (2) the required near-zone field quantities and how they are sampled, (3) the computational methodology used, and (4) the imbedding of various application-driven features. Each process has its pros and cons depending upon its specific application as well as the type of radiation structure under consideration. In this dissertation we put forth a new and original NZ-FZT process that allows the transformation surface along which the near-zone is sampled to be spheroidal in shape: namely a prolate or oblate spheroid. Naturally, there are benefits gained in doing so. Our approach uses a formulated eigenfunction expansion of spheroidal wave-harmonics to develop two distinct, yet closely related, NZ-FZT algorithms for each type of spheroidal transformation surface. The process only requires knowledge of the E-field along the transformation surface and does not need the corresponding H-field. Given is a systematic exposition of the formulation, implementation, and verification of the newly developed NZ-FZT process. Accordingly, computer software is developed to implement both NZ-FZT algorithms. In the validation process, analytical and empirical radiation structures serve as computational benchmarks. Numerical models of both benchmark structures are created by integrating the software with a field solver, viz., a finite-difference time-domain (FDTD) code. Results of these computer models are compared with theoretical and empirical data to provide additional validation.

Name thesis:degree_name

Ph. D.

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Electrical and Computer Engineering

Department dc:contributor.department

Electrical and Computer Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2000

Author dc:creator

• Ricciardi, Gerald F.

Chair dc:contributor.committeechair

• Stutzman, Warren L.

Committee members dc:contributor.committeemember

• Safaai-Jazi, Ahmad
• Rossi, John F.
• Riad, Sedki Mohamed
• Davis, William A.

• FDTD
• antennas
• eigenfunctions
• computational electromagnetics

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

etd-11102000-14250056

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/29518