Asymptotically decoupled angle-frequency estimation with sensor arrays

This paper investigates the problem of jointly estimating the directions of arrival (DOA) and Doppler frequencies of multiple targets with a pulsed Doppler radar employing an array antenna. This is an application of 2-D frequency estimation. It is shown how the original 2-D estimation problem can be reduced into two 1-D problems. The asymptotic 2-D Cramer-Rao bound (CRB) is derived and compared to the 1-D CRB. It is shown that the DOA bounds are equal for large number of antenna elements. A 1-D/1-D estimator is then presented that achieves the 2-D CRB when the number of temporal snapshots is large. This decoupling of the 2-D problem into sequential 1-D problems leads to a substantial reduction in computational cost without loss of estimation accuracy.