ESPRIT-based extended-aperture source localization using velocity-hydrophones

A novel ESPRIT-based 2D angle estimation scheme is proposed using a rectangular array of triads of spatially co-located but orthogonally oriented velocity-hydrophones spaced much farther apart than a half-wavelength. Each velocity-hydrophone measures one Cartesian component of the sonar velocity-field. The use of such velocity-hydrophone triads enable the measurement of the velocity-field vector of the sonar wavefield. Each source´s normalized velocity-field vector is equal to the source´s Cartesian direction-cosines. The source´s arrival angle can thus be extracted from the velocity-field measurements. On the other hand, when uniformly spaced array elements are spaced beyond a half wavelength, ESPRIT´s eigenvalues offer a cyclic ambiguity. The direction-cosine estimates obtained from the velocity-field may serve as reference to clarify the low-variance but cyclically ambiguous direction-cosine estimation obtained from ESPRIT´s eigenvalues. Simulations are presented showing the sample variance of direction-cosine estimates decreasing linearly as inter-triad spacing is increased from a half-wavelength to 12 half-wavelengths, with a 33-fold reduction in estimation standard deviation relative to the half-wavelength case. This proposed scheme also outperforms a uniform half-wavelength-spaced array of pressure-hydrophones with comparable hardware and software costs by an order of magnitude in estimation standard deviation