Apparatus for and method of controlling a feedforward filter of an equalizer
View Patent ↗A method of synchronizing a feedforward filter ( 46 ) that receives a signal resulting from the transmission of a series of symbols through a channel, wherein the series of symbols includes a predetermined sequence of symbols includes the step of developing a plurality of samples from the received symbols ( 60 ), wherein a sequence of samples corresponds to the predetermined sequence of symbols. The method further includes the steps of estimating a channel impulse response from the plurality of samples, calculating a characteristic of the channel impulse response, and synchronizing ( 54 ) the feedforward filter in accordance with the estimated channel impulse response.
1. A method of controlling a feedforward filter that receives a signal resulting from the transmission of a series of symbols through a channel wherein the series of symbols includes a predetermined sequence of symbols, the method comprising the steps of:
developing a plurality of samples from the received signal wherein a sequence of samples corresponds to the predetermined sequence of symbols;
estimating a channel impulse response of the channel from the plurality of samples, wherein the channel impulse response estimate is represented by a plurality of correlation values;
calculating a channel delay by detecting a correlation strength between correlation values of the plurality of correlation values; and
synchronizing the feed forward filter based upon the calculated channel delay.
2. The method of claim 1 , wherein the synchronizing step comprises the step of determining a temporal location of the sequence of samples corresponding to the predetermined sequence of symbols at an output of the feedforward Filter.
3. The method of claim 1 wherein, the predetermined sequence of symbols comprises a synchronization sequence.
4. The method of claim 3 wherein, the synchronization sequence is an ATSC segment synchronization sequence.
5. The method of claim 1 , wherein the estimating step includes the step of integrating a plurality of channel impulse response estimates.
6. The method of claim 1 , wherein the synchronization is further based on a centroid of the correlation values.
7. The method of claim 1 , wherein die calculating step includes the step of selecting a portion of the correlation values having magnitudes that are greater than a predetermined threshold.
8. The method of claim 7 , wherein the calculating step includes the further step of determining a centroid of the selected portion of the correlation values.
9. The method of claim 1 , wherein the estimating step includes the step of storing correlation values in a buffer representing the estimate of the channel impulse response.
10. The method of claim 1 , wherein the developed samples have real and imaginary components and wherein the estimating step includes the step of deriving the channel impulse response using a first correlation buffer and a second correlation buffer, wherein contents of the first correlation buffer are derived from the real components of the developed samples and contents of the second correlation buffer are derived from the imaginary components of the developed samples.
11. The method of claim 10 , wherein the estimating step includes the further step of combining the contents of the first correlation buffer and the contents of the second correlation buffer to derive correlation values representing the estimate of the channel impulse response.
12. The method of claim 11 , wherein the estimating step includes the further step of storing the derived correlation values in a third buffer.
13. An apparatus for controlling a feedforward filter of an equalizer that receives a signal resulting from the transmission of a series of symbols through a channel wherein the series of symbols includes a predetermined sequence of symbols, comprising:
means for developing a plurality of samples from the received symbols wherein a sequence of samples corresponds to the predetermined sequence of symbols, comprising;
means for estimating a channel impulse response from the plurality of samples wherein the channel impulse response estimate is represented by a plurality of correlation values;
means for calculating channel delay by detecting a correlation strength between correlation values of the plurality of correlation values; and
means for synchronizing the feedforward filter in accordance with the calculated channel delay.
14. The apparatus of claim 13 , wherein the synchronizing means includes means for determining the temporal location of the sequence of samples corresponding to the predetermined sequence of symbols at an output of the feedforward filter.
15. The apparatus of claim 13 , wherein the predetermined sequence of symbols comprises a synchronization sequence.
16. The apparatus of claim 15 , wherein the synchronization sequence is an ATSC compliant synchronization sequence.
17. The apparatus of claim 13 , wherein at least some of the samples have a non-zero imaginary component.
18. The apparatus of claim 13 , wherein the synchronization is further based on a centroid of the correlation values.
19. A computer-readable medium for controlling a feedforward filter that receives a signal resulting from the transmission of a series of symbols through a channel, wherein the series of symbols includes a predetermined sequence of symbols having stored executable instructions for implementing:
a first routine for developing a plurality of samples from received symbols, wherein a sequence of samples corresponds to the predetermined sequence of symbols;
a second routine for estimating a channel impulse response from the plurality of samples wherein the channel impulse response estimate is represented by a plurality of correlation values;
a third routine for calculating a channel delay by detecting a correlation strength between correlation values of the plurality of correlation values; and
a fourth routine for synchronizing the feedforward filter in accordance with the calculated channel delay.
20. The computer-readable medium of claim 19 , wherein the synchronizing routine includes a routine for determining the temporal location of the sequence of samples corresponding to the predetermined sequence of symbols at an output of the feedforward filter.
21. The computer-readable medium of claim 19 , wherein the predetermined sequence of symbols comprises a synchronization sequence.
22. The computer-readable medium of claim 21 , wherein the synchronization sequence is an ATSC compliant synchronization sequence.
23. The computer-readable medium of claim 19 , wherein at least some of die samples have a non-zero imaginary component.
24. The computer-readable medium of claim 19 , wherein the synchronization is further based on a centroid of the correlation values.