Apparatus for and method of controlling a feedforward filter of an equalizer
A method of controlling a feedforward filter of an equalizer includes the steps of generating a complex representation of an output of the feedforward filter and generating a representation of a decision from an output of the equalizer. The complex representation and the decision representation are correlated to obtain a phase error estimate. A phase correction value is generated based on the phase error estimate and used to adjust the phase of the output of the feedforward filter.
1. A method of controlling a feedforward filter of an equalizer, the method comprising the steps of:
generating a complex representation of an output of the feedforward filter; generating a representation of a decision from an output of the equalizer; correlating the decision representation with the complex representation to obtain a phase error estimate;
generating a phase correction value based on the phase error estimate; and adjusting a phase of the output of the feedforward filter using the phase correction value.
2. The method of claim 1 , wherein the equalizer is adapted to receive ATSC compliant signals.
3. The method of claim 1 , wherein the equalizer is adapted to receive ADTB-T compliant signals.
4. The method of claim 1 , wherein the feedforward filter is a finite impulse response (FIR) filter.
5. The method of claim 1 , wherein the complex representation comprises a quadrature signal.
6. The method of claim 5 , wherein the complex representation further comprises an in-phase signal.
7. The method of claim 5 , wherein the quadrature signal is an equalized quadrature signal.
8. The method of claim 1 , wherein the step of generating a representation of a decision is undertaken by a decision device.
9. The method of claim 8 , further including the step of taking the difference between an output of the decision device and a corresponding equalized data signal.
10. The method of claim 9 , wherein the decision representation comprises an error estimate.
11. The method of claim 8 , wherein the decision representation comprises a further complex representation.
12. The method of claim 8 , wherein the decision device comprises a decision slicer.
13. The method of claim 8 , wherein the decision device comprises a trellis decoder.
14. The method of claim 13 , wherein the trellis decoder utilizes a Viterbi algorithm.
15. The method of claim 1 , wherein the correlating step includes the step of temporally aligning the decision representation and the complex representation.
16. The method of claim 15 , wherein the correlating step further includes the step of multiplying the complex representation by the sine and cosine of the phase error estimate.
17. The method of claim 1 , wherein the step of generating a complex representation is undertaken by a phase-shift filter and a delay line.
18. The method of claim 17 , wherein the phase-shift filter is a quadrature filter.
19. The method of claim 17 , wherein the phase-shift filter is a Hilbert filter.
20. The method of claim 1 , wherein the correlating step is undertaken by a multiplier.
21. The method of claim 1 , wherein the step of generating a phase correction value is undertaken by an integrator.
22. The method of claim 1 , wherein the adjusting step is undertaken by a rotator.
23. The method of claim 22 , wherein the rotator comprises a complex multiplier and means for determining a sine and a cosine.
24. A phase tracker for controlling a feedforward Filter of an equalizer. comprising:
means for generating a complex representation of an output of the feedforward Filter; means for generating a representation of a decision from an output of the equalizer; means for correlating the decision representation with the complex representation to obtain a phase error estimate;
means for generating a phase correction value based on the phase error estimate; and
means for adjusting the phase of the output of the feed forward filter using the phase correction value.
25. The phase tracker of claim 24 , wherein the feedforward filter is a finite impulse response (FIR) filter.
26. The phase tracker of claim 24 , wherein the complex representation comprises a quadrature signal.
27. The phase tracker of claim 26 , wherein the complex representation further comprises an in-phase signal.
28. The phase tracker of claim 26 , wherein the quadrature signal is an equalized quadrature signal.