Improved DOA Estimation of Underwater Target with Acoustic Cross Array

In underwater acoustic echo detection, time delays between sensor pairs are usually estimated to determine the direction of arrival (DOA) of a underwater target. We present an adaptive phase difference estimator instead of time delay estimator to get better resolution in case of small size array. The phase difference is obtained by computing the adaptive weights of two parallel adaptive notch filters. We also analyze theoretically the DOA estimation errors, which turned out to be determined by the signal to noise ratio (SNR) and the pitch angle. In computer simulations, the root mean square (rms) error was less than 0.5 degrees with the SNR of 20dB. Both theoretical analysis and numerical results show that our method is effective.