Gradient Flow Source Localization and Separation

C01745: Gradient Flow Source Localization and Separation

The invention, termed gradient flow, is a method of separating and localizing sources of traveling waves that impinge on an array of sensors, without the need of resolving time delays of arrivals as customarily performed in beamforming. Gradient flow converts the problem of separating unknown delayed mixtures of sources into a simpler problem of separating unknown instantaneous mixtures of the time-differentiated sources, obtained by acquiring or computing spatial and temporal derivatives on the array. The linear coefficients in the instantaneous mixture directly represent the delays, which in turn determine the direction angles of the sources. This formulation is attractive, since it allows to separate and localize waves of broadband signals using standard tools of independent component analysis (ICA). Direct application of ICA on the spatial and temporal derivatives of the field yield the sources along with their direction angles. The technique is suited for arrays of small aperture, with dimensions shorter than the coherence length of the waves. Applications of gradient flow include miniature microphone arrays for intelligent hearing aids with adaptive suppression of interfering signals and nonstationary noise, and integrated RF arrays for separating or localizing multiple users or channels from a base station or mobile unit.

Technical Details:

A method of separating and localizing sources of traveling waves, by obtaining linearly independent time-differentiated instantaneous observations of the sources, from spatial derivatives of the traveling wave acquired using a distributed sensor or a sensor array. The sources are blindly separated by direct application of (static) independent component analysis on the time-differentiated observations, yielding both the sources and their direction cosines relative to the sensor geometry. The method is suited for arrays of small aperture, with dimensions shorter than the coherence length of the waves. In one preferred embodiment, three sources are separated and localized from differential observations on four coplanar sensors positioned on the corners of a square. Applications include miniature microphone arrays for intelligent hearing aids with adaptive suppression of interfering signals and nonstationary noise, and integrated RF arrays for resolving or localizing multiple users or channels from a base station or mobile unit.

Looking for Partners:

The invention is directed toward separating and localizing a mixture of broadband signals from observation on a compact array of spatially distributed sensors, each signal being generated by a traveling wave source impinging on the array, arriving from different directions. The sensors measure the field resulting from the traveling wave sources, which could be acoustic, sonar, electromagnetic, or possibly other forms of radiation.