Comments: download file (pdf)
Ref.: SiPLAB Report 03/13, SiPLAB, University of Algarve,2011.
Abstract
Underwater acoustic vector sensor has received much more attentions in recent a few
decades. One type of high precise high-frequency vector sensor TV-001, succeeded for
several applications in Makai Ex05 sea trial, such as direction-of-arrival (DOA) estimation,
geoacoustic inversion, tomography, MIMO communications. In this report, the vector sensor
array (VSA) direction finding performance, including the array directivity index (DI), array
gain (AG), and Cramér-Rao bound (CRB) are studied. Besides, the main research was
focused on the geoacoustic inversion by using various propagation models. One simple
inversion method by comparing the downward and upward beams was studied, i.e. bottom
reflection coefficient (BRC) matching method, the results showed that the (p+v) processor is
the best. The seabed parameter sensitivities were studied, and the compressional velocity
was found could be inverted by matched-field inversion (MFI) methods. The CRB's of
geoacoustic parameter estimates are derived, which also demonstrated that the (p+v)
processing outperforms others. A two-step inversion method was proposed. First, the
compressional velocity, along with the receiver range and depth were optimized using
genetic algorithm (GA). Secondly, the optimized range and depth information was fed back
to improve the accuracy of the replica fields, then the compressional velocity dependent
replicas were matched with the real data, giving high resolution and precise results during
the period of nearly two hours.