Research On Target Detection For Near Space Hypersonic Vehicle-based Radar

With the developments of aerospace and electronic science,radar has been more and more applied to various fields.Especially in the aerospace field,radar is essential for the normal operation of the entire aerospace system.However,as the rapid development of aerospace techniques,the requirements for the radar are getting higher and higher,radars based on the traditional military combat radar are far from being able to meet the demand,therefore,to explore and develop all kinds of suitable radar for the aerospace development is rather urgent.In recent decades,the development and flight experiments of airborne vehicle have been paid much attention to in the field of aerospace,and the rapid development of all kinds of vehicle has brought new challenges to radar signal processing.In November 2006,a powerful country for the first time publicly said the implementation of the "global two-hour strike plan",the carrier of the plan is the near space hypersonic vehicle-a new weapon,which caused a great deal of global warming;a year later,the United States reduced to one hour on the basis of the original two-hour plan,put forward the "global one-hour strike plan",which is sufficient to explain the role of hypersonic vehicle as a new weapon.At the same time,other countries have conducted a variety of studies on near-space hypersonic vehicles,of which the control and navigation techniques for space hypersonic vehicles are the main components.In this dissertation,from the perspective of radar,"Hypersonic vehicle platform target detection based on the near space" as the theme of the study,"Near space platform" is the National Natural Science Fund project "Space target detection,imaging and identification methods based on space platform" of the important research content.Hypersonic near space vehicle as a radar platform is an innovation,in the world of this selection of the new platform for the control and navigation technology is also synchronized,so it is also needed to learn from the basic research of navigation and control.In order to get a solid foundation and a complete system of the system,we start from the vehicle movement characteristics.The main contents,methods,and results of this dissertation include the following aspects:First,the motion characteristics of the near space hypersonic vehicle are determined.It is found that the hypersonic platform has the characteristics of high-speed and maneuvers.Based on Newton's second law and aerodynamics theory,the cruise section and reentry section of near space hypersonic vehicle is analyzed and the 2D-FDM(Two-Dimension-Flight Dynamics Modeling)Model is proposed,the analytic expression of the motion state of the vehicle under the model is obtained.The aerodynamic lift and aerodynamic drag are added to the analysis of the cruise section.Based on the principle of minimum power consumption,the direction of the engine control force is re-assumed,and the expression of the motion state of the model is derived.The simulation results show that the trajectory obtained by the model conforms to the motion law of the near space hypersonic vehicle,and it is proved that the aerodynamic effect of the cruise has a great influence on the whole flight.And the polynomial fitting method is used to approximate the flight trajectory of the near space hypersonic vehicle.It is concluded that the trajectory section of the near space hypersonic vehicle can be approximated by the third order polynomial of time,that is,the acceleration must be considered in the flight process.2,Study the characteristics of high-speed of near space hypersonic platform and the problems brought by the near space hypersonic platform.It is found that the SAG echo model is not suitable for near space hypersonic radar.The "stop and go" echo model ignores the relative motion between the radar and the target in a pulse duration(referred to as the inner-pulse),and thus cannot truly reflect the target echo characteristics.In this dissertation,we propose an echo model that includes radar and target relative motion in pulse duration,i.e.,"Move in pulse duration(MPD)echo model".Comparing the MPD echo model with the SAG echo model,it is concluded that if the radar echo of the space hypersonic platform is still signaled as the "stop and go" model,the pulse compression output will not meet the demand of target detection.The MPD model is more likely to reflect the relative motion of the radar and the target than the SAG model.Therefore,the MPD model should be used in the radar signal processing near space hypersonic platform.The filter design for MPD model is given,for solving the problem of offset and widening of the main lobe of the radar echo signal of space hypersonic platform.Theoretical analysis and numerical simulation show the necessity of using the pulse motion model of the echo signal of the hypersonic target.Under the typical parameters,the pulse compression results have the difference of more than 3dB.3,A STAP method is presented for variable speed(accelerating)platform based on the data field.The biggest feature of this method is that it can be used on accelerated platform(acceleration is fixed and known).Space-Time Adaptive Processing(STAP)is an effective technique to suppress the clutter of landforms caused by platform motion.It has been widely concerned in the past 30 years,and platform motion is usually assumed to be uniform.Compared with the traditional uniform platform,the Doppler spectrum extension of clutter echo is more serious,and the degree of broadening is related to array orientation,scattering point position and pulse integration.Therefore,in the case of variable speed platform,the traditional STAP method is adopted,and its clutter suppression performance,especially the performance of the main clutter region,is degraded,and the slow target detection performance is seriously reduced.In this dissertation,a compensation method based on data domain is proposed.By suppressing the increment of the acceleration in the phase by constructing the compensation matrix,the Doppler spectrum of the clutter is suppressed.The simulation results show that the proposed method can narrow the clutter Doppler spectrum,improve the clutter suppression improvement factor of STAP,and improve the detection performance of slow target.4,According to the conclusion of 2,the long-term integration of the target under hypersonic platform is studied.Based on SAR imaging principles,we focus problem in the two dimensions of both range and azimuth.The simulation based on classical method shows that under the condition of MPD modeling,the target defocus result is worse,and then the target integration method based on MPD is proposed.Based on the ?-K algorithm,a set of filters for the near-space hypersonic platform radar is obtained and defined.Then,from the perspective of ambiguity function,it is proved that the radar performance of space hypersonic vehicle platform is lower than that of the uniform platform and the low-speed platform radar in the long-time integration.The results of two-dimensional integration are also quantitatively analyzed,and the widening of the impulse response width IRW of two-dimensional azimuths is given.The peak side-lobe ratio PSLR of two-dimensional integration of range and azimuth is analyzed under different radar parameters,integral side-lobe ratio ISLR and other system parameters change trend.Finally,the computational complexity of the proposed algorithm is analyzed.The results show that the proposed method is better in dealing with the proposed space hypersonic vehicle platform radar under the same computational complexity.