| This paper is derived from a underwater target positioning system,in which the detection distance of location buoy with single hydrophone is about 8 kilometers.When large area coverage is needed,the number of buoy rise.Undoubtedly,the cost of distribution and recovery will increase too.Therefore,it is significative to research and improve the detection distance of the buoy.In this paper,the feasibility of improving the detection distance of the buoy based on the beamforming with cylindrical array is studied and demonstrated.The performance of several typical beamforming algorithms are analyzed and discussed.Then the algorithm is implemented on FPGA,and the resource and power is evaluated.In view of the CW and LFM signal received by the buoy,the study of beamforming algorithm is divided into two aspects,narrow band and wide band.Firstly,the characteristics of conventional beamforming,minimum sidelobe beamforming Capon beamforming and time domain constant beamforming beamforming are analyzed.The performance of beamforming can be mainly reflected in three aspects,which are beam pattern,array gain and robustness.By comparing several beamforming algorithms,the performance of them under different conditions is got.Then the influence of beamforming on the basis of CW and LFM detector,notch filter and correlation detector,is researched.After completing the theoretical analysis,in view of the characteristics of the above beamforming algorithm,the software implementation is completed on the FPGA.The software has three editions,which correspond to constant coefficient beamforming,adaptive beamforming and time-domain wideband beamforming.The software is modular design,including data acquisition,Hilbert transform,weight scheduling,beamforming,weight calculation,data transmission,log recording and FIR filter bank in time domain.Finally,the three editions of software is tested on the FPGA.Then the accuracy of the operation is verified,the possible sources of the error is analyzed,and the resources and power consumption of different algorithms is calculated. |
