An adaptive array antenna for the suppression of high-power interference in direct-sequence code-division multiple access (DS-CDMA) systems is presented. Although DS-CDMA has sufficient flexibility to support a variety of services, from voice to moving-pictures, with high levels of quality, multiple access interference (MAI) is a problem. This is particularly so of the high-power interference which accompanies high-speed transmission in DS-CDMA. While the application of adaptive array antennas is an effective way of improving signal-to-interference-plus-noise ratio (SINR), problems with this approach include large levels of power consumption and the high costs of hardware and of implementing the antennas. Therefore, our main purpose is to realize a simple configuration for an adaptive array system. In order to reduce the required amounts of processing, a common beam provides suppression of high-power interference for the low-bit-rate users; this makes per-user preparation of weights unnecessary. This approach also reduces the consumption of power by the system. Interference is cancelled by minimization of the array output power (i.e., the application of a power inversion algorithm) before despreading. The approach also allows us to improve the implementation of the antenna elements by using small auxiliary antennas. The basic performance of the system is confirmed through numerical calculation and computer simulation. Furthermore, a real-time processing unit has been developed and the effectiveness of the approach is confirmed by an experiment in a radio-anechoic chamber.

Constant Modulus Algorithm (CMA) is a method that has been widely known as blind adaptive beamforming because it requires no knowledge about the signal except that the transmitted signal waveform has a constant envelope. Although CMA has the merit of this blind operation, it possesses problems in its convergence property. In this paper, problems that are inherent to this algorithm is resolved using a combination of CMA and another major adaptive algorithm SMI (Sample Matrix Inversion). The idea is to use SMI to determine the initial weights for CMA operation. Although the benefit of CMA being a blind algorithm is not fully taken advantage of, good aspects of both SMI and CMA can be introduced. By using this approach, two major problems in convergence properties of CMA can be solved. One of these problems is the reliability and this relates to the convergence performance in certain cases. When the interfering signal is stronger than the desired signal, the algorithm tends to come up with the wrong solution by capturing the interfering signal which has the stronger power. Also, the convergence time of this algorithm is slow, limiting its application in dynamic environment, although the slow convergence time of CMA has been studied previously and several methods have been proposed to overcome this defect. Using the proposed method, the deterioration due to both of these problems can be mitigated. Simulation results are shown to confirm the theory. Furthermore, evaluations are done concerning the fading characteristics. It is also confirmed from the simulation that the tracking performance of this method can be regarded as sufficient in personal mobile communication.