Algorithm of Direction of Arrival Estimation for an AUV Based on Sparse T-Array with Four Hydrophones

The number of hydrophone on a small autonomous undersea vehicle(AUV) is extremely limited by its volume and structure, however, higher accuracy of direction of arrival(DOA) is expected for such limited hydrophones. Joint es- timation of azimuth and pitch angle can be realized by traditional isometric T-array with four hydrophones, but the estimation accuracy is limited because the array aperture depends on the half-wavelength. This study proposes a sparse T-array with four hydrophones based on the isometric T-array with four hydrophones, and it enlarges the spacing between center element and No.1 element in the horizontal direction to an integer multiple of the wavelength while keeps the spacing between center element and others half- wavelength. Adopting the cross-spectrum direction-finding method based on conventional beam-forming for DOA estimation, the estimation errors of azimuth and pitch angle are simulated and compared between these two array-patterns. The results show that the azimuth estimation error of the sparse T-array is less than that of the isometric T-array under the same signal-to-noise ratio(SNR). Simulation analysis confirms that the DOA result of the sparse T-array with four hydrophones has higher accuracy, which satisfies the requirement for an AUV that using fewer elements to achieve higher DOA estimation accuracy.