The Choice of the Initial Condition of CMA Adaptive Arrays

Kazuaki TAKAO  Hiromichi MATSUDA  

IEICE TRANSACTIONS on Communications   Vol.E78-B   No.11   pp.1474-1479
Publication Date: 1995/11/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Adaptive Signal Processing Technology in Antennas)
adaptive array,  CMA,  steepest decent method,  initial condition,  radiation pattern,  

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In this paper, we analyze the convergence behavior of the CMA (Constant Modulus Algorithm) adaptive array working under the steepest decent method, and investigate how to achieve the highest possible output SINR (Signal to Interference plus Noise Ratio). In multipath radio environments, CMA sometimes suppresses the desired signal (stronger one) and selects to receive the interference (the weaker one) resulting in the low output SINR. This is one of the problems met in an optimization system under a nonlinear control equation where there are two or more local minima of the cost function and the final state depends on the initial condition. The study can be done only numerically by starting from various initial values. In our analysis of the CMA adaptive array in multipath radio environments, we will assume that there are two waves which are radiated from the same source and try to find out what conditions may affect the convergence behavior. In this process, we discover the effect of the neglected factor by the previous papers and revise the initial condition to guarantee the reception of the desirable wave. In conclusion, we propose the prescription of the initial weights of the array elements as well as the choice of preferable arrays.