Direction-finding arrays of directional sensors for randomly located sources

The problem of directional sensor placement and orientation is considered when statistical information about the source direction of arrival is available. We focus on two-sensor arrays and form a cost function based on the Cramer-Rao bound that depends on the probability distribution of the coplanar source direction. Proper positioning and orientation of the sensors enable the two-sensor array to have an accuracy comparable to that of a three-or four-sensor uniform circular array

Closed-form estimation of normal modes from a partially sampled water column

The output of a vertical linear array is used to infer about the parameters of the normal mode model that describes acoustic propagation in a shallow water. Existing subspace algorithms perform singular vector decomposition of the array data matrix to estimate the sampled model functions. Estimates are exact only if the sensing array is totally covering the water column. We design a new subspace algorithm free from this very restrictive requirement. We use two short hydrophone arrays and activate a monochromatic source at different depths. Estimates of both the modal functions and the wave numbers are obtained in a fully automatic and search-free manner. The algorithm can be qualified as truly high resolution in the sense that, while using short sensing arrays, estimation error becomes arbitrarily low if observation noise is arbitrarily low. This method compares advantageously to existing subspace techniques, as well as transform-domain techniques that require impulsive sources, among other constraints. With two (eigen and singular) vector decompositions, the proposed technique has the complexity of a regular subspace algorithm.info:eu-repo/semantics/publishedVersio

IDENTIFICATION AVEUGLE AU SECOND ORDRE, ORDRE ET DIVERSITE DES CANAUX

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A quadratic complexity eigenspace technique for blind SIMO channel identification

International audienceEigenspace techniques are very popular techniques for blind channel identification, but are ones with a large complexity, cubic in the channel order. The newly introduced channel compaction is a signal processing technique that consists in using small-sized linear transformations to progressively force to zero some of the channel coefficients. As such, channel compaction was used to develop the first (and, up to now, the only) blind channel equalization technique with a quadratic complexity. In this paper, we apply blind compaction to develop a new blind identification technique, the first to have a quadratic complexity. Simulation tests show that the low-complexity compaction-based blind identification performs quite similarly to the most referenced existing eigenspace blind identification technique

On isotropic circular arrays of anisotropic sensors

International audienceUniform circular arrays are popular in direction finding applications because they show to be isotropic, i.e. they exhibit the same accuracy (in terms of the Cramer-Rao bound) at all possible planar look directions. We prove that this is not absolutely true if the constituent sensors are not isotropic. For instance, we specify how the anisotropic sensors should be directed and how many are needed in order to ensure an isotropic behavior of the array. We study, in more details, the performance of arrays of cardioid sensors, including anisotropic arrays of cardioid sensor

Spectral efficiency of beamforming-based parameter estimation in the single source case

International audienceIt is well known that beamforming and Capon spectral or direction estimators are biased and inefficient with respect to the Cramer-Rao bound (CRB). On the other hand, the MUSIC algorithm is known to be asymptotically unbiased and efficient, in the single zero-mean circular Gaussian source case only. In this latter case, we prove in this paper that for constant steering vector modulus, the beamforming and Capon spectral or direction estimators of possible several parameters per source are asymptotically (with respect to the number of snapshots) unbiased and efficient as well, a property previously overlooked. Finally, the theoretical numerical and empirical values of the mean square errors (MSE) of the spectral MUSIC, beamforming and Capon estimators of the direction of arrival (DOA) for a single source impinging on a planar array are compare