Analysis and design of broadband acoustic beamformers

Whitt, Christopher J. (2010) Analysis and design of broadband acoustic beamformers. Masters thesis, Memorial University of Newfoundland.

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Abstract

This thesis is concerned with the methods for designing broadband acoustic beamformers. A beamformer is a signal processing system consisting of an array of transducers combined with appropriate signal processing to produce desired directional characteristics. Beamformers have applications in many areas including radar, sonar, astrophysics, medical imaging, multimedia, and electroacoustics. -- Narrowband beamformers are designed to operate at a single frequency or narrow range of frequencies. The techniques for design of narrowband beamformers have been well studied. With advances in signal processing it is now practical to consider a wider range of applications for beamformers, including beamformers which operate over wider frequency ranges, called broadband beamformers. -- There has been an increasing amount of research over the last few decades in broadband beamformers, yet there is a lack of comprehensive summaries and tutorials of the state of the art in broadband beamformer design. -- This thesis proceeds by reviewing analysis of beamformer performance, and the creation of a MATLAB tool to allow the visualization of broadband beamformer response and the rapid comparison of different beamformers. Then classical narrowband design techniques are reviewed as well as several recent broadband methods. It is demonstrated how the visualization tool facilitates deeper insight into the fundamental principles that underlie beamformer design. -- With a firm understanding of the underlying principles of beamformers, it is possible to perform useful comparisons and contrasts between sophisticated modern design methods and see their relationship to the widely known narrowband techniques. Much of the beamforming literature makes simplifying assumptions about the physical array geometry to be used. With an understanding of the underlying principles, a basis is given for choosing array geometries and understanding the performance that can be achieved for a given geometry. -- The contributions of this thesis include a visualization tool for beamformer analysis, a guide for selecting and evaluating array geometries, and direct comparison of several broadband design techniques. These contributions provide a foundation for the successful design of broadband acoustic beamformers.

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