Three-Dimensional Acoustic Imaging by Chirp Zeta Transform Digital Beamforming

To generate volumetric underwater acoustic images, a planar array of sensors is required to collect the signals coming from a 3-D scene. The method most frequently used to process the acquired signals is a beamforming algorithm. In general, owing to the high number of sensors and beam signals, the computational load is prohibitive for real-time image generation. An efficient frequency beamforming implementation based on the use of the chirp zeta transform (CZT) has been proposed in the literature for the case involving linear arrays. In this paper, we propose an algorithm to perform CZT beamforming on the wideband signals collected by a planar array generated by a scene placed in the far field. This extension becomes simpler and more intuitive thanks to a nonconventional method of defining the azimuth and elevation angles. In terms of computational complexity, the analysis compares the solution developed with traditional beamforming techniques carried out in both time and frequency domains, showing several advantages for the proposed method.