Study Of Moving Target Detection With Weak Radar Signals

The detection of moving target using weak radar signal is important in the field of target detection using radar technology.The detection is quite challenge when the signalto-noise ratio is low.With the coherent accumulation of multiple pulses over a period of time,the signal-to-noise ratio can be greatly improved,and the target with weak signal can be eventually detected.However,for a moving target of weak radar signal,the length of the time to accumulate multiple pulses coherently is constrained by moving distance of the target.If the distance is more than one-half of the distant unit,the method based on fast Fourier Transformation(FFT)is not be applicable because the range cell migration can occur.In addition,the motion parameters of the target is typically unknown or difficult to estimate,which makes the coherent accumulation difficult.In this study,the motion information of a target is displayed in the form of a 2-D image using the back projection(BP)algorithm flexibly.With the BP algorithm,an appropriate model of the scene is established.Thus,the motion parameters of the target can be searched and determined.The motion parameters are then use to correct the envelop of each echo.Thus,multiple echoes can be synchronized,and the coherent accumulation of pulses over a long period of time becomes possible.In addition,the target is traced after being detected.Considering that the moving target's states change constantly and maybe randomly,the coherently accumulated echoes may be unsatisfactory because the missingness of an existing echo or multiple echoes can happen at the moment when the status of the target changes.To overcome this problem,an interactive multi-model algorithm is further carried out to depict the moving track of the target.In this study,the radar imaging system consists of multi-channel,multi-pulses,and ultra wideband.The system is divided into imaging and tracing components.The main research tasks and accomplishments are:(1)For the radar imaging system of multi-channel and multi-pulses,an echo model for a moving target of weak radar signal was theoretically developed.Different echo models were established to address different motion characteristics.The principle in 2-D imaging is also studied for each echo model.(2)The detections of moving target using coherent and non-coherent accumulation of multiple pulses are analyzed and compared.The relationship between each accumulation approach and number of pulses accumulated is established,respectively.Each relationship is validated through simulations as shown in Chapter 4.(3)Because the BP algorithm is of high level of accuracy in imaging,parameters to describe a moving target is searched using the segmental integral.If the motion parameters can be estimated accurately,the coherent accumulation becomes feasible within a long period of time.Then,a new method based on the segmental integral is theoretically developed.With the consideration of the complexity in searching and tracking,and the robust detection,the estimation of motion parameters of a target and the coherent accumulation of pulses are done in each segment.The effectiveness of the method is verified through simulation.(4)In addition to using the signal processing to detect a moving target of weak radar echo,the radar system as a factor is considered.The number of channels and pulses accumulated are quantitatively studied to understand the influence of variable noise background and number of pulses accumulated on the performance of the moving target detection.(5)For the tracing of a moving target in different segments(space and time),a tracing algorithm that is adapted to maneuver characteristics of a moving target and that is interactive and multiple model is studied.The results are compared with those derived from the classical Kalman filter algorithm.experimental results show their trace performance during target motion states change dramatically.Experiment results show that the tracing algorithm has greater advantage.