Realization Of Multi-beam Interferometric Imaging Algorithm Based On DSP And FPGA System

Multibeam bathymetric sonar has become the mainstream of the sea bottom topographydetection with its advantages of high measurement accuracy and wide measurement range. Atthe same time of multibeam bathymetric sonar detecting the seafloor topography, it alsoreceives backscatter strength information of the seabed that can reflect geomorphologicalfeatures of seabed. At present time, echo intensity information extraction method ofmultibeam system should combine the multibeam bathymetric data. Because single-pointimaging algorithm can get only one depth information and reflection intensity information ofsea bottom in one beam area, so it severely limits the improvement of the resolution;nowadays, although the application of “snippet” method solve the resolution problem, itsseabed depth information number is corresponding to the beam number, the depth informationexpect the beam axis is calculated approximately, makes the geomorphological features andtopography information cannot combine accurately and cannot achieve the joint detection ofthe topography and geomorphology.To solve these problems this paper introduces the idea of interferometric into imaging ofmultibeam echo sonar, use the large number of DOA and TOA value estimated by multibeambathymetric system in every beam to sample the seabed echo intensity information receivedby multibeam bathymetric system, get the backscatter intensity information that can reflectthe physical properties of seabed and correspond to the seabed bathymetry detection valueone by one through a series of processing. First, this paper theoretically analyzes the basicprinciples of multibeam interferometric bathymetric algorithm and traditional imagingmethod "snippet", derivates the basic principle of multibeam imaging algorithm based oninterferometric principle on the basis of the two methods; then analyzes the some majorfactors that affect the sound intensity in the sea water, gives the method of getting backscatterintensity level from echo intensity level by compensation; verifies the feasibility andeffectiveness of the algorithm by the processing of experimental data measured on the lakeusing Matlab algorithm program; Finally, gives a hardware implementation method of thenew algorithm on multi-processor DSP and FPGA signal processing platform.The research indicates that comparing to the traditional imaging algorithm of multibeamsystem, multibeam interferometric imaging algorithm can effectively improve the resolutionof the multi-beam imaging system, can get a lot of imaging data in the range of a beam. At thesame time, these imaging data and bathymetric data are one-to-one correspondences with each other; this method can get the imaging data and bathymetric data at the same time, makes themultibeam system can get imaging and bathymetric detection at the same time, achieving thejoint detection of topography and geomorphological features of multibeam system.