### ASA 127th Meeting M.I.T. 1994 June 6-10

## 4aUW14. Eigenstructure-based algorithms for time varying array.

**Benjamin Friedlander
**

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Ariela Zeira
**

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*Signal Processing Technol. Ltd., 703 Coastland Dr., Palo Alto, CA 94303
*

*
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This study considers the problem of finding the directions of narrow-band
signals using a time-varying array whose elements move during the observation
interval in an arbitrary but known way. The emphasis is on the case where the
shape of the array changes significantly during the observation interval. The
motivation for this study are problems involving direction finding systems
employing more than one platform such as a spatially referenced synthetic
aperture sonar. Assuming that the signal is uncorrelated from snapshot to
snap-shot, two eignestructure based algorithms for this problem were derived.
These algorithms are modifications of techniques developed originally for time
invariant arrays. The first uses array interpolation, and the second uses the
ideal of focusing matrices. Like other eigenstructure methods, these algorithms
require a modest amount of computations in comparison with the maximum
likelihood estimator. The performance of the algorithms is evaluated by
Monte-Carlo simulations and compared to the performance of the time-varying
beamformer and to the Cramer--Rao bound. Although both techniques were
successful for wideband array processing with time invariant arrays, it was
found that only the interpolated array algorithm is useful for direction
finding with time varying arrays.