Research On Wideband Array Signal Adaptive Beamforming

In the field of radar,the technology of wideband array signal adaptive beamforming has become more and more prominent in practical radar engineering applications and has been favored by researchers.Research on space-time interference suppresion has always been a hot spot.In scenarios of rapidly moving interference or array platform,the conventional wideband adaptive beamforming methods can only form narrow null in the interference direction and cannot effectively suppress interference,the output signal to interference and noise ratio of conventional wideband adaptive beamforming methods will be degraded severely.At this time,the receiving system needs to comprehensively consider and integrate various interference suppresion measures from multiple dimensions to improve the anti-interference ability of the radar system.This article starts research around this,the work contributions and research contents are as follows:1.The wideband array signal model and the basic conceptions of wideband beamforming are introduced,the structure of time-domain wideband beamformer and frequency-domain wideband beamformer are also introduced.2.In this work,in order to avoid the spectral distortion of the wideband beamforming output signal,two kinds of constant beamwidth beamforming algorithm with flexible and controllable sidelobe levels are proposed.The sub-band constant-beamwidth beamforming method and the method based on spatial response variation constrainted pattern synthesis are used to achieve wideband constant beamforming.The former can achieve frequency invariant beamforming pattern at mainlobe.The latter can achieve frequency invariant beamforming pattern at any frequency for any direction of interest.Both can form a constant beam with controllable side-lobe levels.3.A wideband muti-interference null widening technique that can achieve a constant beam width is presented.This work mainly includes: the adaptive adjustment of the depth and width of the nulling position when the DOAs of wideband interferences are known and unknown.The method of inserting nulling and sub-band constant beam-width beamforming method realizes wideband interference suppression.When the DOA of the interference is unknown,we inspired by Milloux methods,the taper matrix of space time structure is constructed,then the array Covariance Matrix is reconstructed based on this taper matrix.Combined with Sptial Response Variation(SRV)constraints,it can achieve null widening and constant mainlobe,which can effectively suppress the movement of interference sources.4.This work presents a wideband robust adaptive beamforming method with low prior information,which can against non-ideal situations such as large DOA mismatch and small traning data samples.Based on the SRV beamforming pattern synthesis method,the number of constraints on the frequency response in the frequency band was reduced.An extra constraint is imposed to control the power from the sidelobe region and avoid convering to the interference direction when estimated the space-time steering vector.As compared with several previously proposed robust Capon beamformers based on space-time structure,the proposed method has higher robustness and superior performance in the presence of large DOA mismatch and small traning data samples.