Hybrid modulus blind equalization for quadrature amplitude modulation (QAM) receivers

Abstract

The present invention provides methods and apparatuses for blind equalizers with a hybrid adaptation error. In one embodiment, a Quadrature Amplitude Modulation (QAM) signal receiver, includes: a filter to reduce error in equalization, the filter to output a QAM signal; a decision engine coupled to the filter to determine a symbol based on the QAM signal; a first error generator coupled to the filter to compute a first error signal based on the QAM signal and a constant; a second error generator coupled to the filter and the decision engine to compute a second error signal based on the QAM signal and the determined symbol; an error combinator coupled to the first and second error generators to generate a combined error signal from the first and second error signals; and an adaptation engine coupled with the error combinator and the filter to reduce a equalization error according to the combined error signal.

Description

technical field [0001] In general, at least some embodiments of the invention relate to blind equalizers, and in particular, but not exclusively, to blind equalizers for quadrature amplitude modulation (QAM) receivers. Background technique [0002] Quadrature Amplitude Modulation (QAM) can be used to represent data by varying or modulating the amplitude of two carrier waves that are 90 degrees out of phase with each other and are therefore called quadrature carriers. The amplitudes of the quadrature carriers can be modulated to represent the digital symbols being transmitted. A symbol may be represented as a point in the complex plane when the modulation amplitudes in its two orthogonal carriers are represented along the real and imaginary axes in the complex plane. A group of symbols used in a QAM scheme may be collectively referred to as a group. The group graph shows the set of symbols in the complex plane. [0003] A rectangular QAM group consists of a set of symbols ...

AI Technical Summary

Problems solved by technology

However, since the CMA equalizer uses only one modulus, there may be a large residual mean square error (MSE) after convergence due to adaptation noise

Residual errors can lead to decision errors for higher order QAM signals

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