Research On Adaptive Digital Beamforming And Anti-jamming

As a key technology in array signal processing,Digital Beamforming(DBF)is widely used in radar,sonar,astronomical observation,communication,satellite,medical imaging and other fields.However,in the face of increasingly complex electromagnetic environment with many interferences,higher requirements are put forward for Digital Beamforming technology,which needs real-time,spatial resolution and anti-jamming characteristics.Therefore,as a common anti-jamming technology,Adaptive Digital Beamforming(ADBF)came into being.Considering that the sampling covariance matrix inversion(SMI)algorithm has poor performance on FPGA due to the number of snapshots and covariance matrix mismatch,this paper proposes a FPGA implementation scheme of SMI algorithm based on diagonal loading(DL-SMI),and carries out in-depth research,the main contents are as follows:Firstly,based on the theory of array signal processing,the narrow-band signal models of uniform linear array and uniform plane array are established,and the patterns of each model are simulated.At the same time,the paper explains the principle of the adaptive beamformer based on the uniform linear array model,and the typical beamforming criteria: the maximum signal to interference plus noise ratio(MSINR)criterion,the minimum mean square error(MMSE)criterion and the linearly constrained minimum variance(LCMV)criterion are analyzed and simulated.The results shows that the beamforming based on these criteria can adaptively resist interference and form nulling in the pattern.Secondly,the paper studies the typical non blind and blind algorithms of adaptive beamforming,the least mean square(LMS)algorithm,the recursive least squares(RLS)algorithm,the SMI algorithm and the DL-SMI algorithm are analyzed theoretically,formula derication and comparison of advantages and disadvantages are carried out.What’s more,the patterns of these four algorithms are simulated respectively.It is concluded that DL-SMI algorithm has better convergence,stability,anti-interference and higher output signal-to-noise ratio.In addition,the constant mudulus algorithm(CMA)and the blind algorithm based on the direction of arrival(DOA)estimation are analyzed,and the similar iterative formulas are obtained by comparing CMA and LMS algorithm,the only difference is that the error signals are different.Finally,the hardware and FPGA implementation of DL-SMI algorithm are proposed based on the L-band multi-beam antenna system.Then the FPGA design principle and algorithm flow of each mudule in array signal preprocessing and DL-SMI algorithm are analyzed,and the feasibility and correctness of each mudule design are verified by using Modelsim,Vivado Simulator and Matlab simulation software.In addition,in order to verify the DL-SMI algorithm,the wired and wireless test environment is built,and the adaptive beamforming pattern and beam power are obtained through the experimental test.It is verified that the DL-SMI algorithm based on FPGA can achieve the maximum gain in the desired direction and adaptive anti-interference.