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

在用于下一代移动的通信系统的DS/CDMA中，有必要减小衰落和干扰的影响。另一方面，在具有与移动的通信相同的无线电环境的ITS（智能运输系统）中出现类似的问题。因此，本研究课题主要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，我们开始研究适用于移动的通信的CMA（Constant Modulus Algorithm）自适应阵列，并试图提高其性能。当CMA系统通过使用最速下降法进行优化时，发生的是，收敛速度非常低，并且输出信号与干扰加噪声比根据初始权重而降低。为了改善这种特性，我们提出了一种输入信号相位控制的恒模自适应阵列。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，我们研究了基于ESPRIT（一种高分辨谱分析技术）的波达方向（DOA）估计，这是智能天线的一项基础技术。首先，我们考虑了2D-ESPRIT在几种平面阵列中的应用，提出了计算量小且无需可靠性检验的估计方法。对三角阵二维DOA估计的计算机仿真结果表明了该算法的有效性。其次，提出了一种快速递归的二维酉ESPRIT算法，以实现高计算效率。对相干波的二维DOA估计进行了计算机仿真，并对估计值进行了复数化配对。仿真结果表明，该算法在估计精度、计算时间和DOA跟踪能力等方面均具有较好的实用性，可应用于移动的通信和智能交通系统中。

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.