Research On Target Depth Attribute Determination Method Based On Line-Spectrum Interference Structures Characteristics In Shallow Water

During the cruising process of the underwater platform,it may encounter the security threats caused by various targets.How to achieve target depth attribute determination(aerial targets,surface targets or underwater targets)without the target prior information is very important,particularly when it is difficult to obtain accurate localization results of the target.Effective determination of target depth attribute has a profound impact on the security and concealment of underwater platforms.In shallow water,the interference structure characteristics and Doppler characteristics of target line-spectrum signal can be used for target depth attribute determination.The interference structure characteristics of line-spectrum signal can be used for the depth attribute determination of underwater targets.The Doppler characteristics of line-spectrum signal can be used for further depth attribute determination of surface targets and aerial targets.For the problem of submerged target depth attribute determination in shallow water,the target depth attribute determination algorithm based on the interference structure characteristics of line-spectrum signal has been studied firstly.Then,on the foundation of the effective depth model,the feasibility and robustness of the algorithm are deeply studied.We carried out theoretical research and formula derivation,the effects of different receiving depth,source frequency and received signal-to-noise ratio on depth attribute determination performance have been analyzed through simulation.Therefore,the receiving depth selection method and the critical depth prediction method have been proposed based on actual sea conditions.The simulation results indicate that when the receiving sensors are in the ideal states,the depth attribute determination performance is significantly better than that in the other states,proper adjustment of the receiving states can ensure the depth attribute determination performance to satisfy the actual requirements.The sea experiment data processing results show that the depth attribute determination performance is better in ideal receiving states,also show that factors such as receiving depth,received signal-to-noise ratio have a large impact on depth attribute determination performance.The effectiveness of the receive depth selection method and the critical depth prediction method has also been verified by sea experiment data processing results.Aiming to the problem of aerial target depth attribute determination,the formula derivation and simulation results verify that there is only amplitude difference between the aerial target field and the surface target field under the same environmental parameters,and an aerial target can be treated as a surface target during depth attribute determination.Hence,based on the interference structure characteristics of line-spectrum signal,the submerged target depth attribute determination algorithm can also be used in the aerial target depth attribute determination.On the basis of the interference structure characteristics of line-spectrum signal,the effective determination of underwater target depth attribute can be achieved,but the depth attributes of aerial target and surface target are both determined as non-underwater targets.For this algorithm it is difficult to distinguish between surface targets and aerial targets.Therefore,the next step is to make a differentiation between aerial targets and surface targets based on the Doppler characteristics of line-spectrum signal.On the basis of the aerial targets azimuth,elevation and frequency estimation results,the parameter estimation of the aerial target have been performed to distinguish between aerial and surface targets using the Doppler characteristics of line-spectrum signal.The sea experiment data processing results validate the feasibility of the proposed algorithms.Moreover,there are many researches on target depth attribute determination based on interference structure characteristics of line-spectrum signal,and these researches generally have the premise that the line spectrum frequency of the research objects can excite the first two modes.Although the target whose depth attribute need to be determined is same,only when it locates at shallow water whose depth should be relatively shallower,the algorithm is effective.The depth attribute of targets,locating at shallow water whose depth is relatively deeper,cannot be correctly determined.Aiming to this problem,after combining interference structure characteristics of line-spectrum signal and matched field processing theory,the target depth attribute determination algorithm based on matched field processing has been proposed by using the signals collected by vector sensor.Based on this method,we can realize depth attribute determination of the targets whose frequency can excite first three modes,so as to expand the sea depth range in which the algorithm is feasible.The feasibility and robustness of the algorithm have been verified by simulation results.The influence of the mismatched sea environmental parameters on the algorithm performance has also been analyzed in this paper.The performance of target depth attribute determination algorithm whose matching variable is the summation of vertical complex acoustic intensity active components at different receiving depths,is more accurate and robust than that of algorithm whose matching variable is the reactive component of the vertical complex acoustic intensity.