Research On Digital Beam Forming Based On Wideband Array Parameter Estimation

With the development of signal processing technology,the high resolution algorithm based on narrowband array signals has been relatively mature.Compared with narrowband signals,wideband signals have the characteristics of large amount of target information and weak correlation of reverberation background,which is beneficial to parameter estimation of targets.Although narrowband signals are similar to wideband signals,their processing methods can not be applied to wideband signal processing directly.Therefore,wideband signal processing has become an important direction and hotspot of array signal processing.Therefore,two core technologies of wideband signal processing,wideband DOA estimation and wideband beamforming,are studied in this thesis.The classical wideband DOA estimation algorithms are divided into two classes,one is the noncoherent signal subspace algorithm,that is,the ISM class algorithm,and the other is the coherent signal subspace algorithm,namely the CSM algorithm.The main idea of the ISM algorithm is to divide the whole wideband signal into several narrowband ones,which can lead to the loss of information and can not process the coherent source.While CSM algorithm,although the focus matrix of each subband is focused to processing a frequency point and can deal with the problem of coherent sources effectively,but focus on general methods of a need to estimate the direction of arrival,and CSM algorithm is affected by the accuracy of the prediction of the large angle.In view of the above problems,this thesis proposes a CSM direction finding method which is not sensitive to the estimated direction error.The method is based on obtaining the initial estimate of the source and estimates the angle for the center to draw a fine search roughly,will search each search range for the estimated angle according to the CSM algorithm.By comparing the power spectral function obtained by CSM algorithm at different estimation angles,then get the accurate angle finally.The simulation results based on the 56 element equidistant linear array show that the proposed method still has good super-resolution DOA estimation when the SNR is low to-10 d B.In order to solve the problem of signal sorting in complex electromagnetic environment,wideband beamforming is used to enhance the target signal and suppress the interference in complex environment,thus solving the above problems.The simulation results show that the space frequency broadband beamforming and space-time domain broadband beamforming structure can separate multiple wideband signal beamforming effectively,the ideal point in the target direction,so as to realize the signal sorting.Based on the deep research on broadband signal processing technology,the hardware implementation of broadband signal processing system is completed.Firstly,for the needs of broadband signal processing,the hardware architecture of signal processing based on FPGA and DSP processor is designed.And then gives the function of each module in the system.Finally,the realization principle and implementation method of two important modules in the FPGA part of the broadband signal cognitive processing system are introduced in detail.