Title:
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High resolution bearing estimation by a distorted array using eigenvector rotation
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Current high-resolution wavenumber processors are either applicable only to linear equi-spaced
arrays or require a manifold search over the ideal array response. As a result of this they exhibit
a loss of resolution, bias and increased variance in bearing estimates when the receiving array is
subjected to spatial sampling errors. This thesis has addressed the nature of these problems and
proposed signal processing algorithms which are robust to the spatial sampling errors.
A review of current super-resolution methods is included, explaining why each exhibits a performance
degradation. An eigen decomposition of the array cross-spectral matrix is shown to
retain information about the spatial sampling process which can be then made available after
suitable processing. The required procedure involves rotating all the principal eigenvectors in the
signal subspace until they have elements of equal magnitude. Gradient search techniques are
derived which can be applied to solve the resulting non-linear equations.
A novel matrix notation is introduced which allows the non-linear equations to be written more
concisely, this in turn leads to their solution by constrained Lagrangian optimization and several
new algorithms are proposed. The minimization equations are then reformulated as a maximization
which enables all the eigenvectors to be rotated simultaneously, as opposed to' pairwisc or individually
in the minimization case. These formulae are generalized to allow rotating vectors without
pre-calculation of the signal subspace but using the cross-spectral and data matrices directly.
Extensive simulations have been performed comparing the new methods with similar previous
work, MUSIC and the Cramer-Rao lower bound. Air acoustic experiments on a 16 element array
have also been performed to verify the practical implementation and evaluate the algorithms
performance with a deformed line array using real data.
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