Target Localization In Shallow Water Based On Array Invariant

Target location problem is a significant part in underwater acoustic application.On the military hand,it can track the hostile targets to attack accurately.On the civilian hand,it is employed in a wide application in the ocean,such as oceanography,sensing of marine life,and for oil or nature gas exploration.There are many methods that provide the instantaneous estimates of targets or source,including three-sensor array,matched filed processing(MFP),target moving analysis(TMA),and waveguide invariant(WI).Array invariant(AI)is a new method is introduced in this paper,which has no prior knowledge of environmental parameters to locate the targets in the waveguide.In addition,it differs from MFP,avoids both the expensive computations of copy field and experimental data.The array invariant exploits the dispersive modal arrival structure of the acoustic field in an ocean waveguide and array gains fully.This paper analyzes and reviews the development and current situation of domestic and international underwater acoustic location techniques.In this context,the concrete contents are as follow:Firstly,it is derived from normal mode theory of the acoustic field in the ocean waveguide.By solving the equation of Helmholtz,the pressure can be expressed using normal mode.And the properties of the normal mode theory in a particular waveguide where the top surface is absolutely soft and the bottom is absolutely hard are introduced,such as cut-off frequency,phase velocity,group velocity and vertical angle.Based on the amendatory expression of the array invariant,we can redefine the concept of the array invariant.This part is the fundamental research and theory for the whole paper.Secondly,the simulation of target location with the vertical and horizontal arrays in the shallow water,which is based on the array invariant theory,is done.The main idea is:conventional plane-wave beamforming technique is given,get the array invariant on the basis of image processing technology and realize the distance estimate.Also,ocean parameters are changed to study how the ocean parameters affect the estimate results.Then the factors that introduced errors to the location are analyzed.Finally,array invariant method is applied to localize and track a source deployed in the far-field using measurements conducted by a horizontal receiver array and a vertical receiver array respectively during the SongHua lake in October 2013.The experiment results have nearly the same range as the GPS does,it could confirm that AI is effective,simple andaccurate method to estimate the source range.