Date of Award

4-2013

Document Type

Thesis - Open Access

Degree Name

Master of Science in Electrical & Computer Engineering

Department

Electrical, Computer, Software, and Systems Engineering

Committee Chair

Dr. William Barott

First Committee Member

Dr. Richard Stansbury

Second Committee Member

Dr. Timothy Wilson

Abstract

Acoustic phased arrays with inter-element spacings of greater than one half-wavelength will produce grating lobes that decrease the usefulness of the array. With many array configurations, the near-field and far-field character of these lobes is significantly different -- an optimization of the array configuration to reduce grating lobes in the far-field can have little bearing on the performance of the array in the near-field.

The focus of this thesis is the reduction of grating lobes in the near-field by iterative optimization. Genetic algorithms are employed to choose inter-element spacings which are able to reduce the magnitude of grating lobes at select distances in the near-field. The genetic algorithm produced configurations that are theoretically able to suppress grating lobes in the near-field.

In order to verify the efficacy of these configurations, a hardware test platform was constructed. The platform permits largely automated evaluation of the near-field character of arbitrary array configurations. Using the test platform, several of the arrangements were constructed and evaluated. The results of these evaluations confirm that it is possible to reduce the grating lobes of sparse phased arrays in the near-field.

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