Research On Key Technologies Of Transmit Beampattern Design In MIMO Radars Based On Prior Information

With the development of military technology,the battlefield environment becomes increasingly complicated.In order to adjust to the environment and improve the detecting operational effectiveness,Radar is expected not only to possess multiple operating modes,but also to have multi-target and multi-task real-time processing ability.Traditional radar adaptive signal processing technology is always applied in receiver.To meet with modern radar requirement of improving system flexibility and performance,the degree of freedom in transmitter need to be fully exploited.So far,the main problems in transmit design are the inflexibility of operating mode switching and transmit resource allocation,the ability to adaptive to target and environment,inefficiency of using prior information and low real-time waveform design.Researching these issues is vital meaningful for improving the adaptivity of radar system to target and environment.Based on prior information,this dissertation focuses on transmit design for MIMO radar,including real-time transmit beampattern design,robust transmit beampattern design and array architecture design.The main content of this dissertation is summarized as follows.1.Aiming at real-time transmit beampattern design problem,fast beampattern design for MIMO radar is studied in signal-dependent interference background.Firstly,quasi Side Lobe Cancellation(SLC)and quasi General Sidelobe Cancellation(GSC)based fast transmit beampattern design method are proposed,respectively.In these two methods,the ideas,which used in receiving sidelobe cancellation,are applied in transmit weight vector designing.Transmit weight is able to be generated in real time while transmit beampattern performance is guaranteed.Then,with the combination of base beam theory,we propose a fast transmit beampattern design method for interference mitigation in simultaneous multibeam MIMO radar scheme.In this method,it is restricted that only one beam per subpulse.Based on the power requirement for each beam,beam power allocation is realized in subpulse dimension.Fast waveform synthesis is achieved by using quasi SLC and quasi GSC method.Simulation results demonstrate the advantages of real-time transmit waveform synthesis and accurate regulation of beam energy.2.Robust transmit beampattern design in the presence of array amplitude and phase error is studied.Firstly,aiming to sidelobe interference mitigation in transmitter,the influence of array amplitude and phase error on mainlobe and null is analyzed.Then,a robust beampattern design method based on prior information is proposed.Assuming that interference and amplitude and phase error in transmitter are approximate in two adjacent observations.Interference information is acquired by transmitting orthogonal waveforms.After decoupling transmit and receive amplitude and phase error,a new interference plus noise matrix,which only contains transmit error can be constructed.Based on maximum SINR criterion,transmit waveform correlation matrix of a robust transmit beampattern is obtained.3.Transmit beampattern based on subarray partition for MIMO radar is studied in the interference existing background.Firstly,several subarray partition methods are introduced.Secondly,considering single target tracking situation,a single beam MIMO radar transmit beampattern design based on prior information for joint waveform and subarray optimization is presented.By maximizing Signal-to-Interference-plus-Noise Ratio(SINR),waveform and array structure can be designed alternatively in each iteration.With the guarantee of beampattern performance,the number of waveform to optimize can be reduced.Then,aiming at multi-target tracking,a MIMO radar multibeam pattern design method is introduced with given uniformly-overlapped subarray layout.On the basis of phased-MIMO theory,this method can realize fast multibeam pattern generation in subarray dimension.Finally,assuming that subarrays are nonoverlapped and nonadjacent,a joint beamforming and subarray formation optimized multibeam pattern design for MIMO radar is presented.Subarray layouts and transmit waveforms are optimized alternatively according to the beam priority sequence.4.Beampattern design method for the airborne MIMO radar based on the prior information is studied to suppress the sidelobe clutter in the non-homogeneous clutter environment.Firstly,a beampattern design method for the airborne MIMO radar is proposed.In this method,orthogonal waveform is transmitted to acquire target and clutter information in the last CPI(Coherent Processing Interval).Using the two-dimensional(2D)prior information of the target and clutter in the spatial and Doppler domain,the cost function for the correlation matrix of the transmission waveform is established by employing the maximum output Signal-to-Clutter-plus-Noise Ratio(SCNR)criterion after the space-time matched filter.As a result,sidelobe strong clutter can be suppressed.The SCNR of output signal can be improved.Then,considering acquiring and updating clutter information,a transmit design for joint subarray partition and beampattern optimization is proposed.Transmit array is divided into perception subarray and detection subarray.The perception subarray can acquire and update clutter information every CPI.The receiving data of perception subarray is used in optimal waveform design of detection subarray as prior information.Consequently,real-time perception and detection can be realized.