Design And Implementation Of Signal Processor Of Multi-beam Imaging Sonar On FPGA

The demand for marine resource development and sea-condition monitoring makes underwateracoustic imaging technology more and more important, especially in the muddy waters, highresolution imaging sonar is need more. As most existing imaging sonar is inadequate in terms ofresolution, size and real-time signal processing, a high-speed digital signal processor of multi-beamimaging sonar with up to180-channel receiving signals is designed and implemented in this paper.The main work of this paper is as follows:Firstly, the system architecture of the signal processor in imaging sonar is determined accordingto the design specifications.Secondly, simulation and analysis of multi-beam forming algorithm are done. Based on circulararray, a new method named rotating multi-beam forming is proposed. It can produce high numbers ofintense beams with smaller amount of calculation and less memory. This method uses the same weightvector to generate90beams by rotating the equivalent chord of each beam. Compared with theconventional phased multi-beam forming, it reduces the storage costs almost two orders of magnitude,so it’s especially suitable for near-field focusing occasions with more focal planes.Thirdly, the signal processor is achieved on FPGA. It is used to control the system according tothe received commands，acquire180transducers’ echo signal synchronously, and do real-time digitalmulti-beam forming to generate beams for image displaying.234multipliers (180times multiplexing)and24multipliers (8190times multiplexing) are used to complete180channel’s FIR filtering and538beams forming respectively through multi-channel, multi-coefficients multiplexing multiplier andmodule reuse. It reduces the hardware cost while ensuring real-time processing. Ping-Pong operation,pipeline combined with parallel processing technology are used to improve the processing speed, so itcan produce up to538narrow beams in time, ensuring high resolution of the imaging sonar.Finally, the imaging sonar processor system is validated through a lot of pool test. According tothe testing results，the processor forms538narrow beams that observe the entire field of view angle of90°at one time, and the image reaches resolution of1.1°2.5cm (azimuth resolution rangeresolution). So, it has a good performance in real-time processing, high resolution imaging and stableworking, etc.