Electronic Reconnaissance Signal Preprocessing With Low SNR

In modern warfare,the electronic reconnaissance system is an indispensable reconnaissance means.With the continuous development of military information technology and electromagnetic wave technology,various countries are paying more and more attention to the research of radar detection and interference equipment,and the electromagnetic environment of electronic reconnaissance systems has gradually become complicated which cause some of the signals collected by the electronic reconnaissance system to be submerged in the noise.Therefore,how to realize effective electronic reconnaissance signal preprocessing under low SNR conditions has important practical significance.Based on the channelization in electronic reconnaissance signal processing,this thesis firstly theoretically deduces and simulates the existing digital channelization technology and channelization merging technology.Combined with channelization merging technology and noise detection technology,the channelization technology is improved,and MATLAB simulation and FPGA verification are carried out.Then theoretical derivation and simulation analysis are performed on the new signal decomposition algorithms,Variational Mode Decomposition(VMD)algorithm and Variational Nonlinear Chirp Mode Decomposition(NVCMD)algorithm,that have emerged in recent years.And improvement attempt and detailed experimental analysis are performed on the VMD algorithm in the electronic reconnaissance environment under low SNR conditions.Based on the channelization technology in the electronic reconnaissance system,this paper mainly focuses on the following work:Research on channelization technology and channelization merging technology,through theoretical derivation and experimental simulation,the traditional channelization technology is analyzed in the aspects of noise reduction and channel cutting in electronic reconnaissance signal processing under low SNR conditions.Simultaneously,the characteristics of the noise signal after channelization are theoretically analyzed and simulated,to improvement noise detection.Combined with channelization merging technology,this paper attempts to improve the channelization technology,and carries out simulation analysis and FPGA verification.It is found that the obtained adjacent channel merging method can achieve good reconstruction for wideband signals cut across channels.However,this method requires a certain a priori conditions and the pulse splicing portion has a small attenuation.In view of the application limitations of digital channelization technology in low SNR,theoretical derivation and simulation analysis of VMD algorithm and NVCMD algorithm are carried out.The feasibility of replacing the traditional channelization techniques with these two algorithms in the electronic reconnaissance system under low SNR conditions is analyzed separately.Then theoretical analysis and simulation verification of the characteristics of the wideband signal,realizing wideband signal detection.Finally,based on the VMD algorithm framework,combined with broad Band signal detection technology,the bandwidth control and center frequency update modules in the VMD algorithm are optimized and modified,completing the improvement of the VMD algorithm.Next,the simulation analysis of the improved VMD algorithm's signal decomposition ability,noise reduction performance,and decomposition result error is carried out,and the feasibility of its application in electronic reconnaissance system is analyzed.It is verified that the improved VMD algorithm processes the characteristics of center frequency adaptation,signal bandwidth adaptation,and large improvement of signal-to-noise ratio when implementing signal decomposition.It solves the cross-channel cutting problem of the wideband signal in the traditional channelization technology,which greatly reduces the pulse overlap phenomenon occurs in traditional channelization results.By comparing the performance of traditional channelization techniques,it is verified that the improved VMD algorithm outperforms traditional channelization techniques under low SNR conditions.