Research And Implementation Of SAS Real-time Imaging Technology Based On FPGA

Synthetic Aperture Sonar(SAS)is a high-resolution imaging sonar.The basic principle is to use the movement of a small aperture array to coherently process the received signals at different positions to obtain a large aperture with azimuth upward.Thereby achieving high resolution in the azimuth direction.Compared with the ordinary sonar system,SAS needs to perform complex signal processing on the raw echo data of large data volume,and at the same time puts high requirements on real-time performance,which brings great challenges to engineering implementation.Therefore,selecting and designing a SAS real-time imaging system is an important research topic.In recent years,with the rapid development of programmable devices,FPGAs have high-speed computing power,rich memory cells and pipeline operations,making it possible to process real-time SAS signals with large computational complexity.Therefore,FPGAs are used as real-time signal processing fields.The core processor has broad application prospects.This dissertation focuses on the efficient and robust imaging algorithms that can be applied to SAS real-time systems.The FPGA is used as the hardware platform to complete the design of SAS real-time signal processing system for the first time.The design architecture and optimization scheme suitable for real-time processing are proposed and implemented.Finally,combined with simulation.And the measured data successfully verified its feasibility.Firstly,this dissertation studies the basic principle of SAS imaging.By establishing an echo model and combining multi-subarray technology to analyze the performance parameters of SAS system,a fast point-by-point based on delay table is proposed based on the traditional time domain delay addition algorithm.The imaging algorithm analyzes the performance of the two imaging algorithms from the aspects of imaging accuracy,computational complexity,memory consumption,etc.,and provides data support for constructing SAS real-time signal processing system.The hardware implementation of the imaging algorithm is the key to the entire SAS real-time system.Therefore,this dissertation studies the design and optimization of each module based on FPGA-based SAS algorithm,which mainly includes the real-time processing architecture of distance-to-pulse compression optimization design and time domain imaging algorithm.It analyzes and expounds the design ideas of each module in FPGA in detail.The specific steps are to propose the hardware resource reuse scheme and the real-time superimposed delay solution structure.The SAS beamforming is completed by the multi-channel parallel “array” addressing mode of block segmentation,which effectively reduces the consumption of FPGA resources and improves the processing.Speed,so that real-time processing is satisfied.At the same time,the parametric design of the module can meet the requirements of different detection distances,increasing the flexibility and adaptability of the system.Through the measured data obtained from the pool experiment,the optimization algorithm and design structure proposed in this dissertation are verified.The results show that the system designed and implemented in this dissertation meets the requirements of various indicators required for imaging.