Effect of LNA AM-AM conversion on the performance of constant modulus algorithm (CMA) in CDMA systems

One of the fundamental limitations in the conventional constant modulus algorithm (CMA) for code division multiple access (CDMA) mobile systems is fading of received signals by the elements of the base station antenna arrays. In this paper, a modified CMA with a generalized GWSSUN channel model is introduced. In order to treat the problem of fading, a new cost function is used that yields a time-varying step size. Also, we analyze the AM/AM effect of a LNA on CDMA signals to study the BER performance in the modified CMA. Simulation results of BER performance with DBPSK modulation for linear array shows more advantage in using the proposed CMA rather than the traditional one.