Study On LSS-target Detection Method Using Passive Radar Based On 5G Signal

The development of unmanned aerial vehicles(UAV)brings convenience to people's daily life and national defense military,but it also poses a huge threat to the low-altitude security of the city.Certain measures are needed to monitor the low-altitude airspace of the city.UAV target has significant characteristics of low flying height,slow flying speed and small size,is called Low Altitude,Slow Speed and Small target(LSS-target).The 5G communication signal will become the most abundant electromagnetic resource in the urban environment.At the beginning of the 5G civil communication network planning,it is of great significance to study the use of the transmitting base station as the source of passive radar.Therefore,this thesis studies the LSS-target detection method using passive radar based on 5G civil communication signal.The main research content includes the following aspects: 1)This thesis analyzes the LSS-target detection performance based on 5G signal passive radar system.According to the existing 4G signal,the structural characteristics and key technologies of 5G signal are analyzed,and the resolution performance of the system is analyzed by combining its parameters.The LSS-target detection ability of the system limited by noise,clutter and interference is studied,deriving that clutter and interference from the base station affects the radar system's ability to detect.2)Three methods for suppressing base station-related clutter and interference in radar antenna received signals are presented,and the three methods are compared in this thesis.(a)The interference and clutter suppression method based on time domain processing uses multiple signal classification method to estimate direction of arrival of the base station signal,acquires signal samples of the base station by beam-forming technology,and uses the time domain cancellation Extensive Cancellation Algorithm(ECA)method to suppress interference and clutter.(b)Based on the spatial domain processing interference and clutter suppression method,uses the ideas the feature decomposition and orthogonal projection,which can obtain better interference suppression effect and shorter running time.(c)The above two methods do not utilize a priori information of the signal source.Therefore,an interference and clutter suppression method based on 5G signal characteristics and prior information is presented.The Physical Cell Identifier(PCI)offset search and the a priori information of the base station PCI can be used to obtain the position of the current strongest base station,and correlated clutter and interference for each base station are eliminated in sequence from the received signals.3)Track before detect(TBD)algorithm and several common TBD algorithm foundations are studied in this thesis.The traditional TBD algorithm has the disadvantages of energy diffusion when it is applied to the LSS-targets detection using passive radar based on 5G signal.Therefore,this thesis uses an improved dynamic programming based TBD algorithm,and simulates this algorithm to verify its effectiveness.