Symbol timing ambiguity correction
View Patent ↗A centroid calculator calculates the channel virtual center for an adaptive equalizer, based on some type of training signal (e.g., the segment sync of a ATSC-DTV signal), with internal limiting capability that improves its performance. In addition, a centroid calculator with internal limiting capability that improves performance.
1. A receiver, comprising:
a demodulator for providing a demodulated signal having N signal samples, where N>1; and
a centroid calculator responsive to the demodulated signal for selecting K of the N signal samples to determine a channel virtual center, where K<N;
wherein the centroid calculator includes a limiter for limiting correlation values therein as a function of a threshold value.
2. The receiver of claim 1 , wherein the N=2.
3. The receiver of claim 1 , wherein the centroid calculator comprises:
a detector responsive to the demodulated signal for selecting at least one of the N signal samples for use in providing at least one output signal; and
a centroid calculation loop responsive to the at least one output signal for determining the channel virtual center.
4. The receiver of claim 3 , wherein the at least one output signal comprises a symbol index value, a correlator value and a peak value associated with the selected signal sample.
5. The receiver of claim 3 , wherein the detector provides a time phase value representative of the at least one selected signal sample for application to the demodulator, whereby the demodulator can resolve any demodulator timing ambiguity.
6. The receiver of claim 3 , wherein the detector comprises:
a plurality of paths, one for each of the N signal samples, wherein each path comprises:
a correlator, a leak integrator and a peak search element for use in providing for that path a set of signals comprising an associated correlation value, peak value, correlation peak value and symbol index; and
a selection element responsive to the set of signals from each of the plurality of paths for selecting at least one of the N signal samples for use in determining the channel virtual center and for providing as the at least one output signal the associated correlation value, peak value and symbol index of the selected signal sample.
7. The receiver of claim 6 , wherein the correlator correlates to an ATSC-DTV (Advanced Television Systems Committee-Digital Television) segment sync signal.
8. The receiver of claim 6 , wherein the correlator correlates to an ATSC-DTV (Advanced Television Systems Committee-Digital Television) frame sync signal.
9. The receiver of claim 1 , wherein each of the N signal samples are complex.
10. The receiver of claim 1 , wherein the centroid calculator is a complex centroid calculator.
11. The receiver of claim 1 , wherein the threshold value is a function of a peak correlation value.
12. A method for use in a receiver, the method comprising the steps of:
demodulating a received signal for providing a demodulated signal having N signal samples, where N>1; and
selecting K of the N signal samples to determine a channel virtual center, where K<N;
wherein the selecting step comprises:
determining for each of the N signal samples a symbol index value, a correlator value, and a correlation peak value;
selecting at least one of the N signal samples for use in determining the channel virtual center by comparing the correlation peak values associated with each of the N signal samples; and
determining the channel virtual center as a function of the associated correlation value, peak value and symbol index of the selected signal sample.
13. The method of claim 12 , wherein the N=2.
14. The method of claim 12 , wherein the correlator value represents a correlation to an ATSC-DTV (Advanced Television Systems Committee-Digital Television) segment sync signal.
15. The method of claim 12 , wherein the correlator value represents a correlation to an ATSC-DTV (Advanced Television Systems Committee-Digital Television) frame sync signal.
16. The method of claim 12 , wherein each of the N signal samples are complex.
17. The method of claim 12 , wherein each of the N signal samples are complex.
18. The method of claim 12 , further comprising the step of providing a time phase value representative of the at least one selected signal sample for application to a demodulator, whereby the demodulator can resolve any demodulator timing ambiguity.
19. The method of claim 12 , wherein the determining step includes the step of:
limiting correlation values as a function of a threshold value.
20. The method of claim 19 , wherein the threshold value is a function of a peak correlation value.