Broadband beamspace DOA estimation algorithms for low frequency conformal array

Beam-space MUSIC for direction of arrival estimation of underwater broadband targets with low frequency is presented for conformal array. Firstly, broadband constant beamwidth beamforming (BCBB) weights are designed via array pattern synthesis based on second-order cone programming (SOCP) at each frequency bin in bands of interest. Then, the output data at the array elements from broadband sources in different directions pass through the BCBB that direct multiple directions at adjacent region of the DOA (direction of arrival). Finally, high resolution algorithms are used for fine DOA estimation. Because designed beampattern have same beamwidth in the mainlobe region and low sidelobe level at each frequency bin, therefore, the wideband source can be received without distortion, at the same time, interfering signals from sidelobe region can be suppressed more effectively. Accordingly, the performance of high resolution DOA estimation algorithms in beamspace processing is guaranteed. Results of computer simulation and lake-experiment show that beampattern with constant beamwidth and desired sidelobe level can be effectively formed by BCBB, moreover, DOA estimation of underwater broadband targets can be attained accurately for low frequency conformal array.