Study On Weak Target Detection Method For DTV-based Passive Bistatic Radar

With the increase of Low Altitude,Slow Speed and Small target(LSS-target)such as drones,it is requisite for us to pay attention to its safety.Due to its good range resolution,the digital TV signal has large bandwidth.Besides,its fuzzy function is like a pin.All of these advantages make it possible to be used as passive bistatic radar source.And it is feasible to use digital TV signals as passive bistatic radar to detect and monitor such targets.Therefore,this thesis will focus on the detection of LSS-target for passive bistatic radar source of digital TV.First,a radar system using digital TV signal as the source of illumination is established,and the distance and speed resolution of the system were analyzed.For the source of the system,the digital TV signal is introduced and analyzed,mainly from its own signal characteristics,and its modulation method is elaborated.Then the characteristics of digital TV signal in time domain,frequency domain and fuzzy function are analyzed.Aiming at the problem of secondary peaks in the blur function of digital TV signals,the reasons for the fuzzy secondary peaks caused by the structural characteristics of the digital signal are analyzed.They can be divided into intra-frame and inter-frame secondary peaks.The corresponding secondary peak suppression method was developed,and the simulation achieved good results.For passive bistatic radar system of digital TV,it is divided into a reference channel and an echo channel.The correlation between the components of the digital TV signal will produce side peaks during the matched filtering process.In addition,the reference channel also introduces multipath signals while receiving direct waves.While the echo channels receive echo signals,there are also clutter such as direct wave signals and multipath signals.Since the above three problems will affect the detection of LSS-target,this thesis will try to address them.First,the corresponding secondary peak suppression scheme is given to solve some problems of secondary peaks caused by digital TV signal.Second,equalization processing technology is adopted to solve wave purification problems which is related to the reference channel direct,by using the zero forcing algorithm and the minimum mean square error algorithm to carry out the direct wave purification.In doing so,the simulation verified the effect of the algorithm on the direct wave purification.Third,for the multipath and clutter suppression of the echo channel,the commonly used LMS algorithm,RLS algorithm and ECA algorithm were compared and analyzed,which help to analyze the suppression effect of the algorithm.Finally,for the shortcomings of the simulation results of the above three algorithms,an improved ECA algorithm is given,and the performance of the algorithm for clutter suppression is verified,and the simulation has achieved good results.After the signal processing,if the target echo energy is still weak.In order to effectively detect the target,a long-term coherent accumulation method is needed to increase the target echo energy.However,in the process of accumulation,the relative movement of the target causes the phenomenon of distance migration.To solve this problem,this article intends to form an equivalent fast and slow time dimension by segmenting the continuous signal,and apply the Keystone algorithm to the target distance migration Calibration,simulation analysis verified the effectiveness of the algorithm,and achieved good energy accumulation effect.