Broadband source direction estimation using a circular array

The problem of estimating directions of multiple broadband sources using the eigenstructure of the tempospatial data covariance matrix (TSCM) is dealt with. K.M. Buckley and L.J. Griffiths (1986) suggested that, similarly to the narrowband case, the eigenstructure of this covariance matrix can be used to estimate the signal-only (or noise-only) subspace and then use it for direction estimation. However, even for a single source and a given arbitrary array geometry, the eigenvalues of the signal-only tempospatial covariance matrix (TSCM), and therefore its effective rank, depend on the source direction as well as on its spectral level. This leads to serious difficulties in the implementation of Buckley and Griffiths´ algorithm. The authors show here that by using a special array geometry, namely a two dimensional circular array, the eigenvalues of the signal-only TSCM for one source are practically independent of the source direction. Based on this property, they suggest a more feasible algorithm for parameter estimation of multiple broadband sources using an array of circular geometry