Mixed-signal gradient flow bearing estimation

A mixed-signal architecture for estimating the 3-D direction cosines of a broadband traveling wave impinging on an array of four sensors is presented. The architecture implements gradient flow, which converts the problem of resolving time delays between sensor observations into the problem of estimating relative amplitudes of spatial and temporal derivatives over the array. Direction cosines of the source are obtained through least-squares adaptation on the derivative signals. Least-squares adaptive cancellation of common-mode leakthrough and correlated double sampling in finite-difference derivative estimation reduce common-mode offsets and 1/f noise for increased differential sensitivity. Experimental results from an integrated circuit for acoustic localization demonstrate decimation of time delays with 5 μs resolution at 2 kHz sampling rate.