Research On Target Detection Algorithm Based On External Illuminator

With the continuous development of navigation satellites,the application of navigation reflection signal has attracted more and more attention.Because of its low cost,wide coverage,all day and so on,the navigation signal as a passive radar transmitter has great advantages in the field of target detection.The target detection system based on navigation satellite signal is essentially a bistatic passive radar.Compared with the monostatic radar,the system does not need a specific transmitter.Its transmitter can be any navigation satellite.The receiver can be carried on aircraft,ground vehicles or fixed on the ground to detect the target in the detection area.Therefore,the system can avoid the radar silence and other problems.The main research content of this project is the target detection algorithm based on GNSS-R(global navigation satellite system reflection),which is deeply analyzed from the perspectives of geometry,scene design,link calculation,algorithm simulation and measured data.The research contents of this paper are as followsFirstly,the system model is analyzed theoretically,and the feasibility of GNSS-R target detection system is analyzed combined with signal system,link calculation,STK scene simulation and hardware performance.The signal-to-noise ratio of the direct signal and the reflected signal is calculated by the radar equation to judge whether it meets the sensitivity of the hardware system and whether it meets the prerequisite of target detection,which lays the foundation for the subsequent detection system.Secondly,aiming at the problem of time and frequency error caused by bistatic radar transceiver separation,the direct signal synchronization algorithm is mainly studied,and the Kalman filter is introduced into the carrier loop to improve the tracking performance.At the same time,considering that the traditional tracking algorithm needs the combination of software and hardware,a software based data block movement tracking algorithm is proposed to reduce the hardware requirements,and the synchronization performance and stability of the three algorithms are compared.Then,aiming at the problem of low signal-to-noise of navigation satellite,the signal-to-noise ratio of reflected signal is improved by combining coherent integration with non coherent integration,and the feasibility of the algorithm is verified by combining the measured data.Aiming at the problem that dual channel processing algorithm requires high synchronization of hardware dual channel,a target detection algorithm based on single channel signal acquisition is proposed.Keystone algorithm and PGA algorithm are used to correct the time delay and frequency error,so as to improve the signal-to-noise ratio of reflected target echo.Finally,aiming at the problem that the moving target can not accumulate for a long time,the corresponding frequency and time delay offset are estimated,and the moving target is detected by compensation.In order to solve the problem of multi moving target detection caused by ground clutter reducing target detection performance,and weak target may be submerged in the sidelobe of strong target,a multi-order eca-b algorithm is proposed,which uses iterative update reference function to cancel the echo signals in different stages,so as to realize the detection and differentiation of multi moving targets and improve the detection performance of GNSS-R target detection system.