The Algorithms Of The Direction Of Arrival Of Weak Signals And Strong Signals Based On Pseudo Frame Theory

When strong and weak signals coexist in complex electromagnetic environment,in the fields of electronic reconnaissance,it is difficult to retain weak target signals as the algorithm of strong signals suppression and the estimation of direction of arrival(DOA)of weak signals are seriously affected by strong signals.Therefore,the study of the algorithm of strong signals suppression and the estimation method of DOA are introduced based on pseudo frame theory.When the dual frame defined is not in the space of the frame,it is called a pseudo frame.For suppression the strong signals based on the pseudo frame theory,this thesis discusses how to reduce the number of antenna elements needed,improve the freedom of strong signals suppression,improve the retention of useful weak signals in strong signals suppression,and more effectively suppress strong signals.The strong signals suppression is the premise of DOA detection for weak signals.When the DOA of strong signals and weak signals are far away or the signal-to-noise ratio(SNR)of weak signals is not too low,some general adaptive beam forming technology have good suppression effect,but when the DOA of strong signals and weak signals are relatively close and the SNR of weak signal is too low,the conventional algorithms of strong signal suppression could suppress the weak signals not only strong signals.In addition,when strong and weak signals coexisting,the DOA estimation parameter of weak signals has large estimation mistake,which seriously affects the estimation of the DOA of the weak signals.For uniform linear antenna array,this thesis focuses on the algorithms of strong signals suppression and the DOA of weak signals and strong signals based on pseudo-frame.Specific research contents are as follows:1.The pseudo-frame theory is analyzed.Firstly,the definition of frame is discussed according to the characteristics of basis function in Hilbert space.Then the redundancy feature of frame is analyzed,and the concept of dual frame is discussed.When the dual frame is not in the space of frame,the concept of pseudo frame is introduced.2.In this thesis,the model construction of pseudo-frame of strong signals suppression set up,and the pseudo-frame of strong signals suppression model is constructed by the guidance vector of signals,the guidance vector of strong signals and the noise subspace vector matrix of eigenvector.3.The suppression algorithm of the strong signals via pseudo-frame is studied.The strong signals are suppressed and the weak target signals are retained.In this thesis,the pseudo-frame model is combined with the uniform linear antenna array model.These are discussed,such as the output signal-to-interference-noise ratio(SINR),the main lobe offset and the angle interval of strong signal and weak signal is within or near the main lobe.In this thesis,a large number of experiments prove that the algorithm proposed in this thesis has improvements in above situation.4.The DOA estimation of the weak signals algorithm with pseudo-frame is studied.According to the strong signals suppression algorithm based on pseudo-frame,the DOA algorithm of weak signals on the basis of pseudo-frame is studied in this thesis.Firstly,for multi-target,DOA parameters of strong signals are estimated by conventional DOA algorithm.Then strong signals are suppressed by pseudo-frame the algorithm of strong signals suppression,and the weak signals are retained.While strong signals are suppressed,DOA information of weak signals are tested by spatial search method,and DOA parameters of weak signals are obtained according to beam forming correlation principle.The simulation and experimental data prove that the pseudo-frame DOA algorithm for weak signals have lower mistake for measured data and is still effective for the DOA of weak signals with low SNR.The algorithm does not need iteration and has low computational complexity.Experiments show that the pseudo-frame proposed in this chapter is effective and superior in the DOA of weak signals.