Adaptive phase shifting in FIR filters with application to equalizers

A method for phase-adaptation in FIR filters is introduced and applied to fractionally-spaced equalizers. The technique removes the need of a high-precision rotator-derotator pair when training a blind equalizer with the constant modulus algorithm (CMA). The phase-correcting CMA (PCMA) provides an equalizer with the same convergence reliability as the CMA and the hardware cost comparable to the reduced constellation algorithm (RCA). The technique can also be used to avoid the most common cases of ill-convergence in the RCA.