Performance of CMA adaptive array optimized by the marquardt method for suppressing multipath waves

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Abstract
Constant modulus algorithm (CMA) adaptive array has been proposed as a countermeasure to frequency selective fading; but since the evaluation function is nonlinear with respect to weight, the conventional steepest gradient method is being used for optimization. However, if there is a large variation in the eigenvalue of the correlation matrix of the input, then the convergence becomes very slow.In this paper, Marquardt's method of optimizing the CMA adaptive array is proposed. This method is based on a nonlinear least‐square algorithm, and its dynamic characteristics are clarified by computer simulations.First, the fundamental characteristics of the algorithm are investigated. It is shown that this algorithm gives satisfactory convergence even for those cases where the convergence performance of the conventional steepest gradient method has degraded and where waves approach by multiple paths.Next, the performance of the algorithm is studied under the influence of Doppler shift or in the case where the wave conditions vary and satisfactory performance is obtained under frequency selective fading environment.

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