Research On The Methods To Enhance Air Weak Target Based On GPS External Radiation Source

The passive radar is a radar detection system that used the scattered signal of the target from the environmental signal to illuminate target.It has attracted widespread attention and research due to its strong concealment,anti-implicit ability,and low-cost.The radiation source of the passive radar is rich,including antenna base stations,airborne equipment,various satellites,etc.Such signals will be received by the receiving station after being scattered by the target.GPS is used as an external radiation source for target detection due to its advantages of global coverage and all-weather work.However,the GPS signal is weak,and the satellite's orbit is high,so its echo signal is extremely weak.It is difficult to achieve target detection through a short-term received signal.Long-term coherent integration is an effective solution,but for high-speed and high-maneuvering targets,the long-term integration is often accompanied by phenomena such as beam unit migration,distance unit migration,and Doppler unit migration.The signals received by the radar are distributed in different beams units,range units,and Doppler units.Therefore,how to effectively use the energy of each unit to achieve the enhancement of the received signal is one of the key technologies to achieve target detection of GPS external radiation source radar.Aiming at this problem,this thesis studies the target enhancement methods based on passive radar.The main works are as follows:1.The geometric configurations of space-based radiation sources have been studied and the received signal models under different geometric configurations have been established.For space-based radiation sources,mathematical models of space-to-earth configuration and space-to-air configuration are built.On this basis,the receiving signal models under the radiation of a single radiation source and multiple radiation sources are established respectively,and the possible beam unit migration,distance unit migration,and Doppler unit migration that may exist in the long-term integration process are analyzed.2.The three-dimensional coherent integration algorithm under the radiation of a single radiation source is studied.Aiming at the uniform speed across the beam in the space and the uniform acceleration or deceleration across the beam in the space,the axis rotation and Keystone transform and matched filtering process(AR-KT-MFP)and the phase filtering and second-order Keystone transform and fractional fourier transform(PF-So KT-FRFT)threedimensional coherent integration algorithms are respectively proposed.The algorithm simulations and performance analyses verify that these two algorithms can solve the beam unit migration,distance unit migration,and Doppler unit migration,etc.,to achieve effective enhancement of received signal energy.In the case of a small beam unit migration in the spatial domain during the integration,a coherent integration algorithm based on the splicing of adjacent beams is studied,and the effectiveness of the algorithm is verified through simulation and measured data processing.3.The three-dimensional integration algorithm under the radiation of multiple radiation sources is studied.In order to simultaneously use the radiation source signals of multiple navigation satellites from the target,this thesis uses the signal model in chapter 2 to analyze the characteristics of each scattered signal after the received signal is separated,and studies the incoherent integration algorithms and coherent integration algorithms of multiple radiation sources based on AR-KT-MFP and PF-So KT-FRFT,and through algorithm simulations and performance analyses verify that multi-radiator signals fusion can effectively improve the target detection performance,and the coherent integration algorithm is better than the incoherent integration algorithm.