Direction-of-arrival estimation in partly calibrated subarray-based sensor arrays

The problem of direction-of-arrival (DOA) estimation in partly calibrated arrays is addressed. We assume that an array is composed of multiple well-calibrated subarrays of arbitrary known geometry, but there are imperfections between subarrays. We address the cases of unknown (or known with a certain error) intersubarray displacements, imperfect synchronization of subarrays in time, unknown propagation channel mismatches between subarrays, as well as combinations of these effects. A new subspace-based approach to DOA estimation is proposed, which is applicable to this general class of partly calibrated arrays. DOA identifiability issues for such arrays are discussed, and a relevant Cramer-Rao bound (CRB) is derived. Numerical examples illustrate the performance of the proposed estimators.