### ASA 126th Meeting Denver 1993 October 4-8

## 4aUW7. The tomographic inverse beamforming (TIBF) solution---A new
matched-field algorithm.

**James H. Wilson
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*Dept. of Oceanogr., Naval Post Graduate School, Monterey, CA 93943
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The recent at-sea, real-time signal detection and tracking performance of
the plane-wave solution to the inverse beam forming (IBF) integral equation
(Wilson, 1983; Nuttall and Wilson, 1990) has shown significant (5 to 12 dB)
gains compared to operational sonar systems and other adaptive processing
methods. The Fourier integral method (FIM) (Nuttall and Wilson, 1990) was
thought to be the ``spikiest'' solution to the IBF integral equation, that is
also linear in the covariance matrix. A standard inverse technique (Backus and
Gilbert, 1968) used in tomography has recently been applied to the IBF integral
equation, and two new theoretical results have been obtained. First, the
plane-wave solution, called the least-squares Wilson integral method (LSWIM),
agrees with FIM only at the array design frequency, and is spikier or more
``delta function like'' than FIM below array design frequency. Second, the
non-plane-wave or matched-field solution was obtained by allowing the measured
data vector (covariance matrix) in the Backus--Gilbert inverse method to have
two discrete indices instead of the usual one index. This work was performed
during the analysis of Outpost SUNRISE data for the purpose of enhancing sonar
detection and tracking performance, but has also a more general application in
acoustical oceanography. [Work supported by AEAS.] [sup a)]On temporary leave
from Neptune Sciences, Inc.