Adaptive arrays for wideband interference suppression in wireless communications

Adaptive antenna array systems have played a central role in removing narrowband multiple-access interference (MAI) in wireless communications. However, due to the actual need for increasing channel capacity, the required bandwidth is becoming wider and can bring significant deteriorations of the narrowband adaptive systems. These performance degradations are mainly caused by the fact that the inter-element phase shift becomes a function of the frequency while the adaptation weights are kept independent of frequency. To compensate the effect of the inter-element phase variations, a new approach called the interpolated constant modulus algorithm (ICMA) is introduced. The system is based on an interpolation technique used in conjunction with the constant modulus algorithm (CMA). Results, both analytical and experimental, showing the performance of the system with and without compensation are given and discussed on the basis of the gain-array patterns.