Examination of the use of exact versus approximate phase weights on the performance of a synthetic aperture sonar system

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Authors
Boland, Matthew R.
Subjects
Synthetic Aperture Sonar
SAS
Bistatic Scattering
UUV
Mine Warfare
Advisors
Ziomek, Lawrence J.
Date of Issue
2003-03
Date
Publisher
Monterey, California. Naval Postgraduate School
Language
Abstract
Synthetic aperture sonar beamforming and signal processing relies on properly steering and focusing the aperture beam pattern in order to co-phase all the received signals. Due to the effects of motion in the synthetic aperture sonar problem, the propagation path between the transmitter, discrete point scatterer, and the receiver is time varying. Traditionally, simple approximations are used to determine these propagation ranges and angles of incidence and scatter. Methods to determine these ranges and angles exactly may significantly improve array gain and, therefore, target detection. This thesis investigates improvements to SAS signal processing algorithms using exact methods for the calculation of the time-varying ranges between transmitter and discrete point scatter, and between discrete point scatter and receiver, and the phase angle of the scattered acoustic signal incident upon the receiver. Using computer simulations, exact range and angle calculations were performed for different scenarios and compared to ranges and angles determined using standard approximations. The exact ranges were then used to determine incident phase, and were again compared to the approximate methods. Comparison of the exact and approximate methods was based on range estimation error and percentage error. Improvements in synthetic aperture array gain using exact phase weights based on exact, time-varying range solutions are proposed.
Type
Thesis
Description
URI
Series/Report No
Department
Electrical and Computer Engineering
Organization
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NPS Report Number
Sponsors
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Format
xvi, 65 p. : ill. (some col.) ;
Citation
Distribution Statement
Approved for public release; distribution is unlimited.
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.
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