A Velocity-independent DOA Estimator of Underwater Acoustic Signals via an Arbitrary Cross-linear Nested Array

In this paper, an estimator for underwater DOA estimation is proposed by using a cross-linear nested array with an arbitrary cross-angle. The estimator removes the acoustic velocity factor by deriving the geometric relation of the cross-linear array. Compared with conventional DOA estimation algorithms via a linear array, this estimator eliminates systematic errors caused by the uncertainty factor of the acoustic velocity in the underwater environment. In comparison with the conventional acoustic velocity-independent algorithm, this estimator uses the nested array and does not have to estimate the value of the acoustic velocity, which improves the performance of DOA estimation. Moreover, the proposed method is only slightly inferior to some of the conventional algorithms if the acoustic velocity is estimated accurately. Numerical simulations are provided to validate the analytical derivations and corroborate the improved performance in underwater environments where the actual acoustic velocity is not accurate.