Research On The Beamforming Algorithm Based On Eigenvalue

Digitial signal processing technologies are used to produce spatial and directional beam insmart antenna(SA).The main beam aims at the direction of arrival(DOA) of reference user and theside lobe points to the coming direction of interference user.Therefore smart antenna have been oneof key technologies of the TD-SCDMA systems.As the kernel technology of SA, beamforming algorithm can be divided into two main kinds:Grid of Beam (GOB) and Eigenvalue Based Beamforming (EBB). As the precondition of GOB,DOA is used to form related weighting vector directly in beamforming. As for EBB, the maximumeigenvetor of the received signals covariance matrix can be drawn as the weighting vector withoutdetecting the DOA. It can be easily found that the SA beamforming research by manytelecommunications companies and academic organizations focus mostly on EBB, showing that theEBB is the primary beamforming algorithm.However, there are the following problems in the existing literatures on SA beamforming:(1)Although it has been mentioned in many research materials that the directional transmission ofSA can be achieved by the baseband weighting, the detailed realization scheme is still vacant. (2) Ithasn't been provided in any reference for the realization method of downlink beamforming onQPSK baseband signal after uplink DOA estimation. (3)There is no physical model of EBB tomatch the mathematical model, besides the performance of EBB under complex environment is stillneed to prove. Base on the points mentioned above, the beamforming algorithms (mainly for EBB)of SA are investigated in this paper. The research indicates that certain defects are existent in bothtwo kinds of EBB, which will affect the performance of SAIn allusion to the defects of EBB, a new method of extracting array manifold parameters fromthe communication system based on the the specific feature of orthogonal Midamble sequence isgiven, which will reduce the computation and equipment complexity. Moreover, an IQ-EBBalgorithm is mentioned to realize SDMA and reduce interference effectively, which can be seen asthe combination of EBB and IQ baseband amplitude weighting.