An Improved Dual-mode Blind Equalization Algorithm for QAM Signals

In order to improve the blind equalizer performance of QAM signals, the dual-mode algorithm combining Modified Constant Modulus Algorithm (MCMA) and Decision Directed (DD) rule is improved in three aspects-- improving the error function of MCMA, updating equalizer’s weight coefficients with variable step size, and setting reset rule of dual-mode algorithm with short-time mean error energy. A series of experiments are carried out under different QAM modulation signals, different channels and different SNR to verify the effectiveness of the improved algorithm. The simulation results show that the improved algorithm has less residual inter-symbol interference for high-order QAM signals, and its performance improvements will increase with the rise of QAM order.