Signal Processing Technology And Realization Of Synthetic Aperture Sonar

Synthetic Aperture Sonar(SAS)is a high-resolution imaging sonar.Through uniform linear motion of small-aperture array,synthesized into large-size virtual aperture by Coherent accumulation of the received original echo signal,which realizes high resolution in azimuth direction.And the azimuth direction's resolution is only affected by the size of the actual array aperture,not by the target distance and the frequency of the transmitted signal.The essence of synthetic aperture technology is to use time accumulation to obtain spatial gain.The SAS carrier has strict motion requirements.The Unmanned Underwater Vehicle(UUV)is an underwater platform for intelligent operation.It has the characteristics of autonomous navigation,and it runs smoothly.It is an ideal carrier for SAS systems.In recent years,the UUV-based SAS system is a research hotspot in the field of synthetic aperture sonar,and has been widely used in many aspects such as underwater detection and deep sea mapping.This paper focuses on the SAS signal processing technology based on UUV platform,including original data acquisition,imaging algorithm,UUV platform motion model research and error analysis,motion compensation processing,and image quality improvement.First of all,this paper studies the basic principles of SAS technology and fully studies the constraints of the required parameters in the system.The modularization idea is used to design the hardware architecture of the UUV-based SAS electronic cabin subsystem,which mainly includes the FPGA-based signal processor core control module,signal transmission and receiving module implementation.The system control schemes such as transmitting period and signal pulse width are formulated.Several classical imaging algorithms are studied,including time domain delay summation algorithm,distance-Doppler algorithm,wave number domain algorithm.Comparing and analyzing the applicable conditions and performance of each algorithm,the basic algorithm is improved,and the design scheme of algorithm processor for this system is formulated.Synthetic Aperture Technology Signal processing has a large amount of computation and complex system implementation.How to improve the computational efficiency of imaging is the key to improving the performance of the system.In this system,the original echo signals collected are constructed as an image matrix,and the image matrix of different echo data is subjected to coherent accumulation operation to complete the synthesis of the aperture.The simulation analysis shows that the matrix operation is more efficient than the traditional vector operation,and the imaging speed is fast,which effectively improves the performance of the SAS imaging system.During the navigation process,the sonar carrier will inevitably deviate from the ideal track,and these motion errors will bring about a decline in image quality.In this system,a motion compensation algorithm based on shift imaging is used to overcome the influence of spatial variability of phase error azimuth,which achieves more accurate error compensation and improves imaging quality.And the imaging algorithm is improved to make it suitable for multi-subarray SAS systems.Finally,through the experimental data,the simulation results show that the UUV-based SAS system indicators meet the imaging requirements and can achieve high-resolution imaging of distant objects.And the research content of this system is summarized,and the problems that need further improvement and research are put forward.