Research On Adaptive Digital Beamforming Techniques

Adaptive beamforming technology is one of the important branches in array signalprocessing. It is widely used in both military and economic fields, such as radar, sonar,communication, navigation, earthquake detection, speech signal processing, and so on.Though the adaptive beamforming methods have excellent performance theoretically,many facts influence the effect of the performance in real projects. This dissertation isfocused on the research of the influence of the array errors, reduced-rank adaptivefiltering and wideband beamforming.The basic theory of array signal is discussed. It includes the model of the receivedsignals from array, basic algorithms and methods about adaptive beamforming and thefactors which affect the performance. Through computer simulations, several classicalrobust beamforming algorithms are analyzed and their performances are compared.Then, the framework of Generalized Side Canceller (GSC) is introduced and severaldifferent ways of getting Block Matrix are proposed. Based on the framework of GSC,three reduced-rank adaptive algorithms are discussed, consisting of PrincipleComponents, Cross Spectral and Reduced Rank Multistage Wiener Filter. Computersimulations are given to prove that these methods can reduce the computationalcomplexity and ensure the performance of the system. The wideband beamformingmethods in frequency-domain are studied deeply. The idea is to transform receivedsignals to frequency-domain by FFT, and then do DBF in the frequency domain usingincoherent signal-subspace method(ISM) and coherent signal-subspace method(CSM).For linear and2-D planar array, we prove the validity of the wideband signal processingapproaches.