| Smart antenna technology is very important to the third generation mobile communication system of TD-SCDMA. The smart antenna of TD-SCDMA forms spatial beams and controls its direction, to alignment the target signal and forms spatial zeros aiming to suppress interference signals. It can also adapt to radio wave environment changes automatically, optimize the antenna array pattern, enhance the quality of effective signal, and finally get the higher ratio of signal to interference and improve the capacity of the mobile communication system. However, there unavoidably exists phase and amplitude errors in the course of the design and use of the smart antenna, leading the direction and gain of the smart antenna change, that may cause the users can not communicate in severe cases. Therefore, the calibration of antennas is imperative. This paper first introduces the model of smart antennas in the TD-SCDMA system, then the approach for forming the antenna beams is analyzed and how does the errors of amplitude and phase affect the TD-SCDMA smart antennas is illustrated. After that, the target of antenna calibration in TD-SCDMA system is proposed. Finally, the achievements of the three solutions is verified and compared. This paper consists of three parts:In the first part, the model and the principle of smart antennas in TD-SCDMA system is analyzed, and the pattern of smart antenna beam espectively under the fixed beam-forming algorithm and three adaptive beam-forming algorithms are introduced.In the second part, the article analyzes the influences of errors of amplitude and phase for smart antenna gain, side lobe level, beam pointing and the beam pattern under the adaptive criterion. Finally, the target of antenna calibration is proposed.In the third part, the article analyzes the mathematical model of the Least Square, FFT, and Improved FFT calibration algorithm. Simulation according to the calibration target is made and compared with three calibration algorithms. |
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