A constant-beamwidth beamforming method for acoustic imaging

Wideband array signal processing is applied in many fields such as underwater acoustics, acoustic imaging, and comunication. So the design of the wideband constant-beamwidth beamformer is more and more important. Focused beamformer based on wideband focusing approach is an efficient method. It transforms the signal spaces at different frequencies to the common one using a focusing matrix. It has some advantages such as requiring only one array, computational efficiency and the ability to operate in multipath environments. However, the approaches have a higher requirement of the knowledge of signal arrival angles for the focusing matrix, or else the performance of this method will degrade badly. To overcome this shortcoming, a broadband constant-beamwidth beamforming based on focusing approach for acoustic imaging is proposed in this paper. It improves the robustness of focused beamformer by combining the idea of RCB. Here RCB not only plays the part of a good beamformer but also modifies the arrival angle information of the signal of interest (SOI) and yields the more accurate focused data from the corrected focusing matrix for the focusing preprocessor. Simulation results show the feasibility of the proposed method.