Research And Implementation Of Broadband Adaptive Beamforming Technology

Adaptive beamforming has extensive applications in various fields such as radar and communications,and the main goal is to enhance the signal of interest and suppress the interference at the same time.As wideband signals are widely used in many areas,a huge amount of work has been undertaken in last few years in the field of wideband beamforming.Since wideband signal consists many different frequency components,there are two major problems in wideband beamforming:the output beam pattern vary with frequency and the high computational complexity.The interest of this dissertation mainly lies in the frequency invariant adaptive wideband beamforming and the reduced complexity algorithms.The main work in this thesis can be summarized as follows:1.A detailed analysis of three main structures for wideband beamforming is given:the frequency domain structure,the tapped delay-line(TDL)structure and the sensor delay-line(SDL)structure.The spatial response variation(SRV)factor is employed in the linearly constraint minimum variance(LCMV)criterion to improve the frequency invariant property.2.The beamspace adaptive beamforming techniques are investigated.Motivated by recent progress in frequency invariant beamformer(FIB),a new approach to the transfer matrix design is proposed to achieve a better frequency invariance.The FIB based beamspace processing structure is introduced,and the eigendecomposition technique is employed to mitigate the anti-jamming ability deterioration caused by non-orthogonal beams.3.Two reduced-rank algorithms are analyzed:the multistage wiener filter(MSWF)and the joint iterative optimization(JIO)of filters.The method using the recursive least square(RLS)algorithm to solve the JIO problem is introduced,and a derivation of the least mean square(LMS)algorithm based approach is presented.After that,the SRV constraint is applied to the JIO-LMS algorithm to obtain a better frequency invariant property.4.DSP implementation of wideband adaptive beamforming algorithm is presented based on Beidou satellite navigation anti-jamming system,and the algorithm performance is verified through system experiment.