Study Of The Clutter Cancellation And Signal Accumulate Compensation Of Mimo Radar

Technologies and arithmetics of clutter cancellation and long time accumulation are study focuses of the radar and gain highly regard by many research institutions and experters from all over the world. As a new system radar, the MIMO(multiple input multiple output, MIMO) radar has the advantage over tranditional radars at detecting the target and etc. Theoretics and arithmetics about the space-time adaptive processing(STAP) and the long time accumulation of the airborn MIMO radar are discussed in this dissertation, and the main work and contribution are as blow:(1) A new reduced-dimension STAP method is proposed.The target and the ground clutter in the echo can be separated by one dimension Doppler filtering in groundsill radar, but for the airborne radar, the gound clutter has the space and time character, the STAP technogy must be used to cancel the clutter and reserve the target signal. It is found out by analysis and simulations that the outputs SCNR(signal clutter noise ratio) of some classic reduced-dimension STAP methods descend when the detection velocity is high, which means the performance becomes worse. In order to increase the performance in this situation, a new reduced-dimension STAP method is proposed, which chooses the auxiliary channels according to the relationships of the amplitude and the phase betewwn the detecting channel and the data channels, the simulation results shows that the new method could increase the output SCNR in the high velocity region.(2) Cancelation performance of the clutter and the interference signals in the interference circumstance of three kinds of methods are studied.In the actual engineering application, not only the clutter and noise exist in the circumstance, but also some interference signals present. Two familiar suppressing interference signals are introduced and simulated firstly, and then, the ASLC(adaptive sidelobe cancellation) technology and the two stage-STAP method are proposed, the advantage and disadvantage of these two methods are compared. The comparison shows the two stage-STAP method can avoid many factors which would affect the interference cancellation performance of the ASLC technology, and the calculation complexity of the two stage-STAP method is smaller than the ASLC technology. The simulation results in the last show that the performance of the two stage-STAP is better than that of the ASLC technology when the cancellation of the ASLC technology is under the nonideal condition.(3) The effect of the ampulitued-phase error to the performance of the STAP is analyzed in theory.In the engineering application, because of the facture technics and heat noise, the strict emendation of the array cannot be achieved, nonideal factors, such as the sensors’ position error, amplitude-phase error, frequency error and sensors coupling of the radar array cannot be avoided. The covariance matrix of the echo contain the amplitude-phase error is educed firstly, and the eigenvalue spectrum of the matrix under different amplitude-phase error is drawn, which shows the changing rule of the eigenvalue of the covariance matrix with the errors. Then combining with the generalized sidelobe canceling(GSC), the output expression of the STAP method of the MIMO radar array with amplitude-phase error is educed and proved then by simulations. At the same time, the sensitivities of the MIMO radar and phased array(PA) radar to the amplitude-phase error are compared under the same condition, the simulation results prove that the amplitude-phase error affects the PA radar heavier than the MIMO radar, the PA radar is more sensitive to the errors.(4) An envelope motion compensation method based on the pre-process of the transmitting signal is proposed.Because of the narrow transmitting beam, the tracking and compensating of the high speed moving target cannot be achieved by tranditional radars, the existing methods can only compensate the crossing range-cell and the crossing Doppler-cell, called ‘two crossings’. The ‘two crossings’ model of the moving target is established firstly, and then, some existing compensating methods are introduced, their advantages and disadvantages are analyzed, at last, a method to compensate the envelope motion based on the pre-process of the transmitting signal is proposed. This method could be used by the high speed moving target in the upper space to detect target moving much slower and in the lower space, the basic flow of the method is: switch the scale of the transmitting signal before launching it, which could compensate the crossing range-cell of the moving target, the analysis and simulation show that the method has a nice tolerance of the velocity.(5) The compensation of the ‘three crossings’ of the moving target is studied.In the study of the long time accumulation, the crossing range-cell, crossing Doppler-cell and crossing-beam, called ‘three crossings’, should be compensated, but the crossing-beam of the high speed moving target cannot be tracked and compensated by the tranditional radars for its working system. The transmitting wide beam by the MIMO radar can cover with all of the interested space, which provides the propobility to track the high speed moving target and compensate the crossing-beam. The ‘three crossings’ model of the moving target is educed for the MIMO radar, the characteristics of the ‘three crossings’ are analyzed, and then combining the pre-process method and some classic compensation methods to compensate the ‘three crossings’, simulation results prove the validity of the selected methods for compensating the ‘three crossings’.