Research On Space Time Adaptive Process Technology For Active Homing System In Shallow Sea Reverberation Environment

For active homing system in shallow water, reverberation is mainly comes form bottom andsea surface. Reverberation is the main interference and has great influence for acoustic signaldetection under the active homing systemsonar in shallow water environment. Reverberationsuppression is a hotspots and complicated problem in acoustic signal process. Using spacetime adaptive processing method to suppress radar clutter can achieve great effect.The main feature of active homing system is the Doppler extend caused by homing systemmoving and this kind of extend is similar with radar clutter spectrum extend. We can use thismature technology for reference to suppress reverberation. Aiming at active homing systemreverberation suppression problem in shallow water environment, Space time adaptiveprocessing method has been researched to suppressing bottom and sea surface reverberation.By research the space time adaptive dimension reduction algorithm, arbitrary bottom and seasurface reverberation suppressing method based on arbitrary bottom and sea surfacereverberation model is proposed. The main contributions and creative results of dissertationcan be summarized as follows:1. Arbitrary bottom reverberation spectrum model has been built by study the reverberationstatistic model and spectrum model. The practical sea bottom is irregularity, using surfaceequation to describe the bottom shape and Newton iteration method to work out the arbitrarypoint coordinates, according to the relative position relations and azimuth informationbetween bottom cell and moving active homing system to calculate the reverberation ofdifferent Doppler cell by convolution with transmit signal energy spectrum to get thearbitrary bottom reverberation spectrum. This method has solved the insufficient of flatbottom modeling. The spectrum model simplify method has also been provide. ReverberationCharacteristics has been analysis in many respect, such as reverberation attenuation curve,reverberation level, probability distribution, frequency and space domain correlation.thesimulation and error analysis has proved the model correctness.2. The sea surface reverberation model has been built and the Features of sea surfacereverberation had been studied. In consider of the spectral distribution of sea surface,optimize dynamic sea surface fractal model has been and proposed. Sea surface scatteringstrength expression had been deduced and specific Sea surface scattering strength calculatemethod has been given. The influence and variation of various factors for Sea surfacescattering strength had been verified through the simulation analysis.3. The moving active homing system space time reverberation features and space timeoptimal processing algorithm has deeply studied and arbitrary bottom and sea surfacereverberation space distribution has been deduced. Two dimension space time distribution ofreverberation under different install angle for active homing system has been verified throughthe simulation analysis. For the amout compution of the covariance matrix estimate problem,the reverberation degree of freedom has been ananlyzed. After research, low-level space to approximate full-dimensional data space or projected to low dimensional subspace can beused to achieve dimensionality reduction.Meanwhile, Calculation Method of reverberationsubspace dimension has slso been given in this part.4. In view of the complicated calculations in space time optimal process algorithm, thegeneral form of space time adaptive dimension reduction algorithm has been studied andemphatically studied the TSA and M-CAP space time process algorithm. Compared theAdvantages and disadvantages with optimal process algorithm form many aspects, such asimprovement factor, the amount of calculation and so on. The space time process result andimprovement factor curve of different dimension reduction algorithm was provide throughcomputer simulation. This research has to lay a foundation for arbitrary bottom and seasurface reverberation suppression.5. The STAP reverberation suppression method based on information entropy has beenproposed.By research the Space-time dimension reduction algorithms, the concept ofinformation entropy has introduces to compression feature data. Utilize the differentcharacteristics between target and rerverberation after eigenvalue decomposition to seclecttwo-dimensional space-time data. The entire process of the algorithm has been analyzedthrough the simulation data.6. The dimensionality reduction STAP reverberation suppression method based oninformation entropy has been proposed. Eigenvalue decomposition can increase the amountof algorithm computation, for this problem, STAP reverberation suppression method based oninformation entropy had been inproved as follows. Division the received data to sub-arraythen Space-time smoothing to estimate the covariance matrix,the original dimensions ofspace-time processor reduced form NK to PQ,(P <N, Q<K), using the same size of thesmoothing window space time smoothing target detection data, caculate space-time adaptiveweight vector according to linear constraints and weighted output.7. Experimental verification for dimensionality reduction STAP reverberation suppressionmethod based on information entropy has operated. A detailed analysis from raw dataacquisition to the final output of the processing has been done, experimental results showthat the algorithm can reduce the amount of calculation while greartly detected target.8.Using the dimensionality reduction STAP reverberation suppression method based oninformation entropy for arbitrary bottom reverberation supperession.By dividing sea bottominto grids, curved face equations are used to describe the shape of sea bottom and Newtoniteration method is used to work out the arbitrary point coordinates.The variation betweenazimuth and elevation angle with Doppler under different curved face equations of Thedimensionality reduction STAP reverberation suppression method were analysis throughcomputer simulation. According the simulation reverbearion space time results, calculate thecovariance matrix then get the space time output. 9. Using the dimensionality reduction STAP reverberation suppression method based oninformation entropy for sea reverberation supperession.Based on the dynamic sea surfacefractal model, the impact of different factors for the sea reverberation and space timereverbeation spectrum of active homing system has been analyzed. According to thesimulation results of the space time reverbearion, using the dimensionality reduction STAPreverberation suppression method based on information entropy, space time process resultwas given under the rough surface and rough surface add bubble action method. Simulationresult verified the algorithm has great effect to suppress reverberation and show that thealgorithm performance well.