Chair: Martin Cohen, Raytheon (USA)
Alain Barthelemy, Naval Undersea Warfare Center
Peter K. Willett, University of Connecticut (USA)
A steepest descent gradient algorithm prewhitens the signal received by a uniform planar array. Previously developed methods work only on single line arrays. A novel model facilitates algorithm development by reducing problem dimensionality associated with exact multi-dimensional autoregressive (AR) modeling. The discrete source model, based on a Kronecker product of the received signals between the vertical and horizontal elements of the array, agrees exactly with the classical sinusoidal model. The colored noise source Kronecker product model agrees approximately with a physical geometric one constructed from spherical surface harmonics. The algorithm uses a stacked vector parameterization of the vertical and horizontal AR parameters and optimizes them over a low order whiteness functional. Application of the algorithm with MUSIC demonstrates enhanced performance in terms of angular resolution and detection of low SNR sources. The algorithm allows extensibility and solves the general problem of the three-dimensional volumetric array with arbitrary geometry.
Jonathan H. Gross, University of Texas (USA)
David E. Grant, University of Texas (USA)
Array shape estimation is an important problem in array signal processing. We present an iterative algorithm that estimates two dimensional array element positions via an algebraic solution to a least squares problem, under the assumption that the sources are in the far-field with unknown positions. Under some assumptions, we calculate the dependence of performance on the distribution of the localizing sources. We give examples of algorithm performance from both simulations and real data. We also illustrate algorithm performance for horizontal arrays as a function of time delay estimation variance and the variance of vertical arrival angle estimates.
Otello Gasparini, Dune Ingegneria dei Sistemi (ITALY)
Claudio Camporeale, Dune Ingegneria dei Sistemi (ITALY)
Wideband beamformers based on cross-spectral matrices between array elements are examined. Two methods to estimate such matrices are described, a standard one, the Transform-and-Correlate (TC) pre-processor, and a novel one, indicated as Correlate-and- Transform (CT) pre-processor, which should be considered on an equal base as the former. Applications of CT are outlined in the estimation of correlated multipath, in acoustic Doppler current profiling, in interferometric seabed profiling and in the synthetic aperture sonar.
Herve Chuberre, IRISA Universite de Rennes I (FRANCE)
Thierry Filleul, IRISA Universite de Rennes I (FRANCE)
Jean-Jacques Fuchs, IRISA Universite de Rennes I (FRANCE)
Beamforming algorithms handle sources that are located in the near field by simply adapting the steering vector and having it depend not only on bearing but also on range. The corresponding algorithm, known as the focused beamformer, has poor performances even though the computational burden is quite important since it involves a 2-dimensional beam evaluation in the bearing-range plane. In order to localize such sources using a linear equispaced array in a narrowband context, we propose to apply a model-fitting approach to the output of a beamformer performing a one-dimensional evaluation. For reasonably difficult scenarios, the performances we obtain are satisfactory (close to the Cramer-Rao bound) for a quite acceptable computational burden.
Y. Chocheyras, Thomson-Sintra ASM (FRANCE)
L. Kopp, Thomson-Sintra ASM (FRANCE)
The problem of instantaneous source location estimation with passive differential delay measurements is considered. A maneuvering source is assumed to move close to a few sensors and radiates both broadband and narrowband noise. Differential doppler compensation is required to estimate differential delays between sensors. As near field source motion induces high dynamics in range and signal level, threshold variation linked with inherent signal ambiguity is the prevailing effect in delay estimation. These effects are studied through the calculation of multiple passband Modified Ziv Zakai Lower Bound. Taking these effect into account, an instantaneous estimator of location , speed and course is presented. The new and conventional estimators performance are then compared on simulation and with an at sea experiment.