Research On The Method Of Space Time Adaptive Processing(STAP) In The Doppler Domain

Active sonar space-time processing technology (STAP) research has made important progress. It possesses good doppler detection performance and the performance of clutter suppression. But more Doppler channels needs to be scanned, With the increase of the number of Doppler channels, the calculation also grow geometrically. Therefore it will limit the application of STAP in sonar equipment. In this papcr.the research is beased on the existing technology of STAP in active sonar, to detect the characteristics of the doppler domain to carry out research work,in order to better play to the potential of STAP. and lay a foundation for the further practical application.The main work is as follows:1. In the case of constant signal bandwidth and pulse width, consider of the different performance combinations of chirp signal in STAP.The simulation results show that:at the condition of given signal bandwidth and pulse width.the more numbers of the combined chirp signal.the better detection performance of doppler.but the computational complexity of STAP also increased rapidly. In practical application. we need to accord the calculation of the ability to choose the signal, two chirp signal at least.2. The doppler effect is one of the most important factors of active sonar target detection.The accurate doppler frequency shift estimation can impove the target doppler resolution and the detection ability of active sonar. In this’paper, time domain processing method is used to estimate the Doppler frequency shift.Through the simulation of different interpolation algorithm, the results show that the method of linear interpolation resampling frequency shift compensation accuracy is better.3. In STAP. the increase in the number of Doppler channel can improve the detection performance of Doppler, the computational complexity of STAP algorithm increases exponentially, limit its application in sonar equipment. This paper presents the detection method of composited Doppler channels. All of the Doppler channels are divided into multiple composited channels to detect. It pays a little performance cost to achieve the dimension reduction on the doppler filed and reduce the computational complexity of the system. The results of the study show that:the selection of the adjacent channels need to satisfy the approximate orthogonal condition.And futher.In order to restrain reverberation caused by additional compound channels, this paper gives a method of building composited Doppler channels based on beam width. The distance between the adjacent channels is the frequency shift in beam width. Simulated experiments show the method is effective.4. In the detection of active sonar, the conventional method is difficult to obtain the better ambiguous function and hard to inhibition the scattered echo from the sea surface and submarine, etc. So there is the high false alarm rate in active sonar system.STAP can obtain the ambiguity function and better detection of Doppler performance in the same frequency and bandwidth condition. At one point, we can calculate the doppler value than suppression processing this channels.It can reduce the false alarm rate and improve the target resolution. The simulation and experimental data processing results show the feasibility of the method to suppress the stationary target.5. Through the processing and analysis of experimental data on the sea. the Method of Space Time Adaptive Processing in the doppler domain have farther target detection ability. Compared with the active sonar on active duty. the maximum operating range is increased by around 30% than the 4 nautical miles.At the same time, the detection ability of the weak signal and the SNR process gain are also greatly improved. The result shows that the method is feasible.