In complex water environment, the portable 3D imaging sonar is one of the main techniques for flexible underwater tasks, especially in the near field. In the literature, an efficient digital beamforming called paralle...
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ISBN:
(纸本)9781538645093
In complex water environment, the portable 3D imaging sonar is one of the main techniques for flexible underwater tasks, especially in the near field. In the literature, an efficient digital beamforming called parallelsubarray (PS) has been introduced for portable 3D sonar working in the far field. This paper proposes an extension of the PS beamforming algorithm that enables to process the multi-frequency signals acquired by the cross array from a scene in the near field. The proposed algorithm achieves two stage parallelbeamforming and applies an optimized approximation delay for the near-field beam pattern in the two stage beamforming. Then, the architecture of the algorithm performed on the field programmable gate array (FPGA) is illustrated. The near-field beam pattern of the algorithm is similar to that of the direct method while computational requirement is the lowest compared to other existing methods. To test the validity of the algorithm, a real system was devised and employed in the lake. The results showed that the proposed algorithm could generate satisfactory 3D underwater images.
The computational load is prohibitive in 3D sonar systems for real-time image generation. In the literature, an efficient frequency beamforming method based on the distributed and parallelsubarray (DPS) has been intr...
详细信息
ISBN:
(纸本)9781479905607
The computational load is prohibitive in 3D sonar systems for real-time image generation. In the literature, an efficient frequency beamforming method based on the distributed and parallelsubarray (DPS) has been introduced for planar arrays working in the far field. This paper extends the DPS beamforming algorithm to process the signals acquired from a scene in the near field. The alogrithm divides the full populated transducer array into two stage distributed subarrays. It performs parallelbeamforming on the first-stage subarrays and applies the approximation for time delays in the near-field beam patterns of the second-stage subarray. The computational efficiency is significantly improved as compared with the traditional methods, while achieving the similar resolutions. In addition, a multi-FPGA signal processor is proposed for implementing the underwater 3-D imaging.
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