Wi-Fi Passive Radar Multi-frequency Signal Synthesis Method Research

In recent years,due to the potential development advantages of passive radars,the advantages of multi-static radars in target detection,and the rapid development of wireless local area networks,passive radars based on Wi-Fi signals for wall penetration detection have become a hot topic.The direction of research is that the target of wall-penetration is the personnel of the indoor activities,which puts forward higher requirements for the radar system's distance resolution.This dissertation discusses the method of multi-signal synthesis using multiple frequency channel Wi-Fi signals to increase the signal bandwidth,and analyzes the influence of the inconsistency of phase between signals and the effect on the detection performance of synthetic signals.,and put forward specific compensation methods.This dissertation focuses on the synthesis method of multi-frequency signal of Wi-Fi passive radar.The thesis first analyzes the working principle of the passive source radar system,introduces the basic flow of the basic and passive radar signal processing of the bistatic radar,and explains the principles of the wireless LAN standard and the OFDM technology.Then,the signal frame structure and signal ambiguity function specific to the Wi-Fi signal are analyzed,and the secondary peak of the ambiguity function is suppressed.In this dissertation,a multi-frequency Wi-Fi radar signal model is established and a method of signal synthesis using the orthogonality of OFDM subcarriers is proposed.The expression of the ambiguity function after multi-frequency synthesis is deduced and verified by simulation analysis.Multi-frequency synthesis can not only improve the distance resolution,but also improve the output signal-to-noise ratio after matched filtering.A comparison of conventional multi-frequency coherent processing methods with the one provided in this paper highlights the advantages of the proposed method.The dissertation analyzes the phase difference term that influences the reference signal and the target echo signal,and estimates and compensates the initial phase of the signal transmission that affects the most serious coherent signal synthesis.The analysis of the carrier frequency offset to signal phase synthesis The effect of this method is described,and a carrier frequency offset estimation method based on training sequences,and a residual frequency offset estimation method based on pilot sequences are introduced.