High-Function Smart Antenna Technology for Mobile Communications and Intelligent Transport Systems

在下一代移动通信系统中，有必要减少衰落和干扰对DS/CDMA的影响。另一方面，在与移动通信具有相同无线电环境的智能交通系统中也出现了类似的问题。因此，本课题研究基于数字波束形成器的高性能智能天线，以抑制衰落和干扰的影响。1999年，我们重点研究了适合移动通信的CMA（恒模算法）自适应阵列，并尝试提高其性能。当采用最陡下降法对CMA系统进行优化时，会出现收敛速度极低且输出信噪比随初始权值的增大而下降的情况。为了改善其特性，提出了对输入信号进行纯相位控制的CMA自适应阵列。计算机仿真结果表明了该算法在DS/CDMA系统中的有效性。2000年，我们利用ESPRIT（一种高分辨率频谱分析技术）研究了DOA（到达方向）估计，这将是智能天线的基础技术。首先，我们考虑了2D-ESPRIT在几种平面阵列上的应用，提出了计算量较小且不需要可靠性检验的估计方法。利用三角阵进行二维方位估计的计算机仿真结果表明了该算法的有效性。其次，为了提高计算效率，提出了快速递归二维统一ESPRIT算法。对相干波的二维doa估计进行了计算机模拟，并对估计进行了复化配对。从估计精度、计算时间和DOA跟踪能力等方面证明了该算法在移动通信和ITS中的实际有效性。

It is necessary to reduce the effects of fading and interference in the DS/CDMA used for the next generation mobile communication systems. On the other hand, there arises the similar problem in the ITS (Intelligent Transport Systems) which has the same radio environments as the mobile communications. Therefore, this research project deals with high-function smart antennas based on the digital beamformer to suppress the effects of the fading and interference.1. In 1999, we focused on the CMA (Constant Modulus Algorithm) adaptive array suitable for the mobile communications, and tried to improve the performance. When the CMA system is optimized by using the steepest descent method, it happens that the convergence rate is extremely low and also the output signal-to-interference-plus-noise ratio degrades depending on the initial weights. To improve the characteristics, we proposed the CMA adaptive array with phase-only control of the input signals. Some computer simulation results showed the effectiveness of the proposed algorithm in the DS/CDMA systems.2. In 2000, we studied the DOA (direction of arrival) estimation using ESPRIT (one of the high-resolution spectrum analysis techniques), which would be an elementary technology of smart antennas. First, we considered application of 2D-ESPRIT to several planar arrays, and proposed the estimation method with less computational load and no reliability test. Computer simulation results in 2D-DOA estimation using the triangular array showed the effectiveness of the proposed algorithm. Next, the fast recursive 2D Unitary ESPRIT was proposed to realize the high computation efficiency. Computer simulation of 2D-DOA estimation of coherent waves was carried out together with complexization pairing of the estimates. As a result, the practical effectiveness of the proposed algorithm was shown in terms of estimation accuracy, computation time and DOA tracking ability in mobile communications and ITS.