Target Parameter Estimation Based On Interference Fringes Of Vector Acoustic Field

The signal sonar system received experienced a complicated process.The noise radiated by target,propagated through the ocean channel and arrived receivers,contain target information and environment information.In order to deal with such signals,the signal processing technology,the combination between underwater acoustic signal processing technology and ocean acoustic field modeling technology is getting inseparably associated.But the real ocean environment is complicated and changeable.At the stage,both our understanding of the ocean environment and the computer processing power are not enough to set up an ocean model database system to cover all situations.Therefore,the underwater acoustic signal processing technology which combines the general acoustic field characteristics with the conventional signal processing technology is the current development direction of underwater acoustic technology.In recent years,due to the fact that the acoustic interference structure of low frequency sound field in shallow water was stable and observable,the interference structure has been widely used in marine environment monitoring,passive ranging methods,and inversion of geoacoustic parameters.Firstly,this paper reviews the Normal-mode method,then deduces the formation mechanism of acoustic interference structure,and then analyze whether the interference structure change when the environment parameters such as waveguide environment,target source depth and sedimentary layer parameters had changed.The underwater acoustic field in the environments discussed above modeling by KrakenC model in this paper.In addition,this paper explores the interference fringe equation under waveguide invariant representation.When waveguide invariant approximating 1,the interference fringe equation is expressed as a hyperbolic family.Although the value of waveguide invariant in shallow sea environment is about 1,it will fluctuate under different circumstances,so it is necessary to extract accurate waveguide invariant values from the interference structure.If the interferogram in the time-frequency domain is taken as the image space,using the Hough transform or Radon transform can extract the slope of interference fringes in the local region.When the intercept range is small enough,the waveguide invariant in this region can be regarded as a fixed value,and the waveguide invariant can be calculated by the slope of the local region.If the entire image space is partitioned,and each block of them is processed by Hough transform or Radon transform,we can get the distribution of the waveguide invariant of whole domain.The article also puts forward using the Lines Segment Detector(LSD)algorithm which combined with the image sharpening and image fusion to detect the interference fringes in the interferogram.Simulation results showed that the method is effective.If the image space is the interferogram in range-frequency domain,first and the foremost,it is necessary to use the periodicity of sound pressure spectrum or vibration velocity spectrum at different times to estimate radial velocity.And on this basis,the motion parameters such as the ratio of the nearest passing distance to the speed and the heading angle can be estimated.Using the above estimation results,passive ranging can be realized.