Estimating the parameters of multiple wideband chirp signals in sensor arrays

The problem of estimating the parameters of multiple wideband polynomial-phase signal sources in sensor arrays is addressed. A new deterministic maximum likelihood (ML) direction of arrival (DOA) estimator and the respective Cramer-Rao bound (CRB) are presented for the general case of multiple constant-amplitude polynomial-phase sources. Since the proposed ML estimator is computationally intensive, an approximate solution is proposed, originating from the analysis of the ML function in the single chirp case. As a result, the so-called chirp beamformer is derived, which is applicable to "well-separated" sources that have distinct time-frequency or/and spatial signatures. Our beamforming approach requires the solving of a 3D optimization problem and, therefore, enjoys essentially simpler implementation to that dictated by the exact ML.