Research On Adaptive Beamforming Methods And Realization

The signal often encounters interference from different directions during the propagation process,thus requiring the radar to have adaptive interference zeroing capability.In order to improve the radar's distance resolution,complete the target detection,target recognition and imaging tasks more efficiently,more and more radar systems use broadband signals.With the broadband trend of modern radars,the traditional narrowband adaptive beamforming technology is no longer applicable,we must use broadband beamforming technology.Based on the basic theory of phased array beamforming and adaptive signal processing,this thesis studies the broadband beamforming methods and designs a broadband adaptive beamforming algorithm on multi-core digital signal processing platform.The specific researches are as follows:1.The narrowband signal model and the broadband signal model are investigated,and the workflow of digital beamforming and adaptive basic principles are introduced.The basic criterions and algorithms of adaptive beamforming are analyzed and compared.2.This thesis studies the broadband adaptive beamforming methods,introduces the structure characteristics of time domain and frequency domain wideband beamformer,and focuses on the broadband adaptive beamforming algorithm in frequency domain.The output signal of the classical time-domain wideband beam has a distortion phenomenon,this thesis designs a FIR filter bank that fits the desired frequency response to realize constant beamwidth.For wideband beamforming in frequency domain,this thesis introduces the Incoherent Signal-subspace Method(ISM)and the Coherent Signal-subspace Method(CSM).Based on the ISM algorithm,the modified ISM algorithm is obtained by applying the spatial smoothing technique.The comprehensive performance comparison of the above frequency domain broadband beamforming algorithms is carried out under different simulation conditions.3.The realization of ISM algorithm on multi-core C6678 DSP platform is accomplished.Using the software environment provided by CCS5.4,the ISM algorithm is simulated on the basis of C programming language combined with OpenMP multithreaded technology.The programming flow diagram of ISM algorithm is presented,and the concrete solutions and detailed introduction of key steps and important parts in the realization process are given.The simulation results show that the result of DSP program is correct and has high precision.4.For the realization of the algorithm on the multi-core DSP platform,this thesis summarizes the optimizations of DSP program and the precautions while writing parallel programs.This thesis mainly analyzes and studies the broadband adaptive beamforming technology,and obtains some practical conclusions through simulation comparisons,which can provide reference for the realization of broadband digital radar.