Circular Array Sonar Adaptive Beamforming Principle And FPGA Implementation

Beamforming is the core of the sonar signal processing system. In sonar signal processing system, beamforming module strengthens airspace useful signal reception, inhibits interference, and detects the targets position. Therefore, the beamforming module on underwater detectors, and other systems appear to be particularly important. Based on the principle of array beamforming, adaptive beamforming of circular array is launched a more in-depth study.Firstly, in this paper, the background and research status quo of sonar beamforming is summarized; based on the sonar model being studied in this paper, the active sonar signal is analyzed; the beamforming scheme which aplly plural base-band is proposed; and the beamforming reception method and principle is derived and discussed in detail.Secondly, beamforming of the uniform circular array is studied detailedly, beam pattern function is derived, and simulation experiment is made and analysed with MATLAB. Then LMS adaptive algorithm was introduced, DLMS algorithm is derived by the analysis of the LMS algorithm. Through compare with LMS algorithm and DLMS algorithm, the results show that, based on the structure of the DLMS FIR filtering algorithm, some convergence speed is sacrificed but high-speed parallel processing capabilities is obtained. In this paper, DLMS algorithm is applied uniform circular array beamforming, the result of simulation shows that DLMS adaptive beamforming method can strengthen the target signal, at the same time the null steering of interference signal is formed.Finally, two parallelism processing design idea and method of DLMS adaptive beamforming with 8 elements based on FPGA is introduced. The overall structure of system is parallel processing architecture, and pipeline technology is used in single branch. Hardware description (VHDL) language in the Quartusâ…¡4.0 is used to design the software modules and functional simulation.