The Study Of Beamforming And DOA Estimation For Smart Antenna

Smart antenna is an effective way to resolve the lack of spectrum resources, and it can increase the system capacity and improve the communication link. In recent years, with the accelerated place of commercial smart antenna, the research of smart antenna has been widespread concerned. Acorrding to the beamforming requirements of smart antenna and DOA estimation, an existing crossed microstrip antenna is improved, and a specific hardware implementation of the downlink beamforming is presented. This article also proposes a new algorithm combines with MODE algorithm and SUMWE algorithm which is called MODE-SUMWE algorithm.Firstly, this paper studies the hardware structure for downlink beamforming of smart antenna. An existing antenna has bean improved, the modified antenna has good impedance characteristics and radiation patterns at 3G band. The patterns of the uniform linear array, the uniform circular array and weighted linear array are studied detailed. Based on the classical algorithm, a hardware implementation for the downlink beamforming of the smart antenna is presented. The FPGA model XC5VSX5OT is selected as the digital signal processor, and a high performance chip AD9777 is selected as the D/A chip to generate the DDS signals. The signals passes through a complete RF channel into the antenna. This paper presents the schematic diagrams and the PCB board. Most of the chips we seleced can be programed to control. So the degugging of this circuit is very convenient and it has wide rang of application. The work of this paper provides a hardware platform for beamforming research and it also has great reference values for projects.Based on a detailed study of spatial smoothing algorithm and MODE algorithm, MODE-SUMWE algorithm is proposed. Firstly the algorithm uses the model space (MODE) algorithm to transform the uniform circular arrays into virtual uniform linear arrays. Then the SUMWE algorithm is adopted to get the the noise subspace, doesn’t need eigenvalue decomposition.Finally, ROOT-MUSIC algorithm is used to estimate the direction of signal’s arrival. MATLAB simulation shows that the new algorithm can estimate the DOA of the coherent signals for uniform circular array effectively. Compared with the MODE-SS and MODE-TOEPLITZ algorithm, the computation burden is smallest and the estimation accuracy is also improved.