| Digital signal processing technologies were used to produce spatial and directional beam in smart antennas, The main beam aims at the coming direction of reference user and the side lobe points to the coming direction of interference user. Smart antennas are classified to switching-beam and tracking-beam. Smart antenna technology has been confirmed as one of key technology of the TD-SCDMA system, and will play an important role in the future.Smart antenna technology for TD -SCDMA system is to reduce the total access interference, improve spectrum utilization, increase system capacity, reduce launching power and space electromagnetic interference, and divide dynamically the areas and so on. Compared with other technologys in the mobile communication it shows great potential. Direction of arrival (DOA) estimation is an important reseach direction in array signal processing system, communication system, and smart antenna and so on. The DOA estimation algorithm based array signal processing can resolve the DOAs of maltiple signal soures from various directions simultaneously with high resolution.First the paper introduces the technology of TD-SCDMA system and the background and developments of smart antenna research. And it elaborates the theory of smart antenna, the basic concepts related in detail. Finally, through the reach of the DOA algorithm in the smartantenna technology, propose the improved cyclic MUSIC algorithm.The main research poimt of this paper is to study the realization methods and insufficiencys of the existing DOA estimate algorithm (such as MUSIC algorithm, Cyclic Cross-Corelation MUSIC algorithm). Then proposes the improved Cyclic Cross-Corelation MUSIC algorithm, and through the simulation experiment proved this algorithm theimprovement is effective. The DOA processing of spatial signal is the main research point of spatial spectrum estimation. The MUSIC (Multiple Signal Classification) algorithm, presented by Schmidt in 1979, is the most classical super-resolution algorithm. Based on an exact model of antenna array, the MUSIC algorithm can estimate the DOA of uncorrelated signals accurately. However, as far as adjacent signals with small SNR (signal to Noise Ratio) are considered, MUSIC algorithm cannot estimate DOA. The main approach to solve this problem is full utilization of signal sources' information. The MUSIC algorithm based on the cyclostationarity property have a better perpormance in noise suppressing and signal selectivity by using the cyclosationarity property of signal into array signal processing. However as far as signal with cyclic correlation is improved cyclic MUSIC algorithm was presented in this paper. Both cyclic correlation matrices and conjugate cyclic correlation matrices are considered in this improved algorithm. Emulation result have indicated the improved algorithm can estimate the DOAs of cyclic correlation signals and adjacent signals and has a better resolution and noise suppressing ability. |
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