Blinder equalizer for QAM receivers

1. A circuit, comprising:

a filter to produce an output based on an input that represents a symbol being received, the symbol being one of a Quadrature Amplitude Modulation (QAM) constellation;

a decision engine coupled to the filter to generate a result indicating one region of a plurality of regions in a QAM constellation diagram, the output of the filter being in the indicated region which includes a plurality of symbols of different radii in the constellation diagram; and

an error reduction engine coupled to the decision engine and the filter to reduce a difference between a selected one of a plurality of constants and a modulus of the output;

wherein each of the plurality of constants correspond to one of the plurality of regions;

wherein the selected one of the plurality of constants is selected according to the result of the decision engine; and

wherein the plurality of regions are separate by one or more radii, at least one of the one or more radii is different from any of radii of the QAM constellation.

2. The circuit of claim 1 , wherein the symbol being received has a radius smaller than one of the plurality of symbols in the region.

3. The circuit of claim 1 , wherein the error reduction engine comprises a blind adaptation engine coupled with an error generation circuit, the error generation circuit to generate an indication of error based on the difference between the selected on of the plurality of constants and a modulus of the output, and the blind adaptation engine to adjust the filter according to the indication of error.

4. The circuit of claim 1 , further comprising:

a further decision engine coupled to the filter to determine a symbol based on the output of the filter.

5. The circuit of claim 1 , wherein the error reduction engine comprises a multiplexer to select one constant from a plurality of constants according to the result of the decision engine.

6. The circuit of claim 1 , wherein the plurality of regions in the constellation diagram are specified using a number of radii less than a number of radii of symbols in the constellation diagram.

7. The circuit of claim 1 , wherein at least one of the one or more radii is midway between two closest radii of the QAM constellation.

8. A Quadrature Amplitude Modulation (QAM) receiver, comprising:

a filter to produce an output;

a first decision engine coupled to the filter to identify a symbol in the output of the filter;

a second decision engine coupled to the filter to identify one region of a plurality of regions in a constellation diagram, the output of the filter being in the identified region which includes a plurality of symbols of different radii in the constellation diagram; and

a circuit coupled to the filter and the second decision engine to adjust the filter to reduce a difference between a modulus of the output of the filter and a constant selected according to a result of the second decision engines;

wherein the plurality of regions are separate by one or more radii, each of which is different from any of radii of the QAM constellation.

9. The receiver of claim 8 , wherein the symbol identified in the output of the filter has a radius smaller than one of the plurality of symbols in the region.

10. The receiver of claim 8 , wherein the circuit comprises a blind adaptation engine coupled with the filter to adjust the filter according to a difference between the modulus of the output of the filter and the constant selected according to a result of the second decision engine.

11. The receiver of claim 8 , wherein the constant is selected from a plurality of constants corresponding to the plurality of regions.

12. The receiver of claim 8 , wherein the circuit comprises a multiplexer to select one constant from a plurality of constants according to the result of the second decision engine.

13. The receiver of claim 8 , wherein the plurality of regions in the constellation diagram are specified using a number of radii less than a number of radii of symbols in the constellation diagram for the receiver; and the constellation diagram has more than sixteen symbols.

14. The receiver of claim 8 , wherein each of the one or more radii is midway between two closest radii of the QAM constellation.

15. A method, comprising:

dividing a Quadrature Amplitude Modulation (QAM) constellation of a QAM receiver into a plurality of subgroups, at least one of the plurality of subgroups including symbols of different radii;

determining for a blind equalizer a plurality of constants for the plurality of subgroups respectively, the blind equalizer to reduce a difference between a modulus of an output of the blind equalizer and a selected one of the constants selected based on determining to which one of the subgroups the output belongs; and

determining one or more radii to be used by the blind equalizer to determine to which one of the subgroups the output belongs;

wherein at least one of the one or more radii is different from any radius of the constellation.

16. The method of claim 15 , wherein each of the one or more radii is different from any radius of the constellation.

17. The method of claim 15 , wherein each of the one or more radii is midway between two closest radii of two different ones of the subgroups.

18. The method of claim 15 , further comprising:

designing the blind equalizer using the plurality of constants and the one or more radii.