Research On Beamforming Algorithm Of Wideband Digital Radar Array Antenna

With the rapid development of radar technology and digital signal processing technology,digital array radar has been greatly developed and widely used.The wideband digital radar,which uses wideband signal,has advantages in target resolution,recognition and imaging ability,and has attracted more and more attention.As one of the key technologies of wideband digital radar,wideband array antenna beamforming has important research significance and practical value.Therefore,based on the application background of wideband digital radar,the algorithm of wideband beamforming in radar array antenna is studied in this paper.Aiming at the problem of aperture crossing in current wideband digital radar array antennas,which results in beam pointing offset and inaccurate scanning,a time-domain broadband array antenna beamforming algorithm based on fractional delay is studied.The algorithm designed the FIR fractional delay filter and all-pass fractional delay filter to compensate for the time difference between the received signal reaching different array elements,thereby aligning the main lobe to the desired direction.Simulation experiments show that a wideband array using a fractional delay filter Antenna beamforming can solve the problems caused by the aperture crossing phenomenon and obtain performance close to ideal beamforming.In the practical radar array antenna system,adding fractional delayer after each element will increase the complexity and computation of the system,which can not guarantee the realtime performance.The sub array level fractional delay broadband array antenna beamforming algorithm is studied.The algorithm combines the element level phase-shifting with the sub array level fractional delay,so as to reduce the use of fractional delay,reduce the amount of calculation,and improve the operation speed of the system.The influence of this method on the beamforming performance of wideband array antenna is analyzed by simulation,and the feasibility of this method is verified.Aiming at the problem of poor interference suppression ability of array antenna beamforming in wideband digital radar system and less research on wideband interference signal suppression at present,the adaptive beamforming algorithm of wideband array antenna in frequency domain is studied,mainly including incoherent signal subspace(ISM)algorithm and coherent signal subspace(CSM)algorithm.The adaptive beamforming algorithm transforms the wideband signal to the frequency domain through DFT,and then divides the signal into several sub bands in the frequency domain.Then the narrowband array antenna beamforming algorithm is used to process the sub-band,and then the output is obtained through IDFT.The beamforming performance of ISM algorithm and CSM algorithm under different working bandwidth and interference modes is simulated and analyzed.The simulation results show that these algorithms can effectively suppress narrowband interference and wideband interference and form effective pattern.