多波束宽带探鱼仪发射波束形成的现场可编程门阵列(FPGA)实现

FPGA implementation of Multi-beam Fish-finder transmission beamforming

多波束宽带探鱼仪是一种利用相控阵技术进行远距离、高分辨率海洋生物探测的声学装备。依据全方位多波束宽带探鱼仪在海洋拖网和围网捕捞中的实际需求,通过时延加权在一定的扇区内形成多个发射波束,设计了包含发射控制模块、直接数字频率合成(DDS)宽带波形生成模块、时延波束形成模块和deltasigma调制模块的现场可编程门阵列(FPGA)数字发射系统,以达到集中发射能量实现更深更远距离的鱼群探测的目的。综合现有测试条件,通过实验室水池测试了水平相邻4通道发射机的波束指向性,并使用Matlab软件系统进行波束指向性仿真和调制信号性能分析。仿真及试验结果显示:本研究设计的数字发射系统性能良好,可完成阵子正前方30°内波束形成且实测信号强度与仿真误差小于1%。

The multi-beam fish-finder is an acoustic equipment that uses phased array technology for long-distance,high-resolution marine biological detection.According to actual needs of the omni-directional multi-beam fish-finder in marine trawl and purse fishing,by method of forming multiple transmitting beams in a certain sector by time-delay weighting,the field programmable gate array(FPGA)digital emission system is designed,to concentrate the emission energy for deeper and farther fish detection.The system includes a transmission control module,a DDS broadband waveform generation module,a time-shift beamforming module and a delta-sigma modulation module.Based on the existing test conditions,the beam directivity of horizontal adjacent 4-channel transmitters is tested through the laboratory pool,and the MATLAB software system is used to simulate the beam directivity and analyze the performance of modulation signal.The simulation and test results show that the digital transmitting system designed in this study has good performance,can be used to accomplish the beamforming within 30°in front of the array,and the error between the measured signal strength and the simulation is less than 1%.