Abstract: A high-speed equalizer based on a new algorithm:stop-and-go-DD-LMS CMA (SGLMS-CMA) for quadrature amplitude modulation (QAM) signals is presented.It integrates conventional constant modulus algorithm (CMA) and decision-direct least-mean-square (DD-LMS) under stop-and-go principle.Matlab simulations indicate that,compared with conventional CMA,the new algorithm performs five times faster in convergence speed, 3~5dB improved in rudimental mean square error (MSE), 82% decreased in operation complexity and can correct a final phase ambiguity.As to the equalizer block in the system,synthesis results show that the SGLMS-CMA+DD-LMS equalizer's hardware consumption is only 5% greater than the CMA+DD-LMS equalizer's.Finally by using SMIC 0.18μm library to synthesis,the new equalizer is embedded into QAM demodulation chip,and test results show that the new equalizer acts better.

Key words: CMA, DD-LMS, equalizer,  convergence speed,  phase ambiguity