An Efficient Four Elements CMA Adaptive Array

Abstract

Adaptive arrays in mobile communications based on any arbitrary performance criteria have many problems in tracking the desired signal at different interference angles relative to the desired one. To use the adaptive arrays efficiently in mobile communications, we need a system which is independent on interference angles. In this paper a system based on the well known constant modulus algorithm (CMA) is proposed. It is four elements adaptive array, each two elements are controlled by the CMA, and they are crossed by 45° angle. The proposed system is examined by computer simulation and compared with the conventional system. It is found that the conventional two elements array is suffering from the capture problem and its performance is degraded at certain interference angles e.g. 25°, 50°, 55° When the interference power is equal to the desired signal power, the proposed system out-performs the conventional one. Therefore the suggested system is more suitable in mobile communications which employs CM modulation techniques such as FM, QPSK and GMSK. The system under consideration can be used also for all other adaptive arrays employing IMS, PI, Applebaum etc. In this article the analysis of the CMA and the proposed system are considered in details.