Apparatus for and method of controlling a feedforward filter of an equalizer
View Patent ↗A method of synchronizing 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 includes the step of developing a plurality of samples from the received symbols, wherein a sequence of samples corresponds to the predetermined sequence of symbols. The method may further include the steps of estimating a channel impulse response from the plurality of samples, wherein the channel impulse response estimate is represented by a plurality of correlation values, identifying a maximum correlation value from the plurality of correlation values, defining a window relative to the maximum correlation value, calculating a characteristic of the correlation values within the window, and synchronizing the feedforward filter in accordance with the characteristic.
1. A method of controlling a feedforward filter that receives a signal resulting from 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 sample corresponds to the predetermined sequence of symbols;
estimating a channel impulse response of the channel from the sequence of samples, wherein the channel impulse response estimate is represented by a plurality of correlation values;
identifying a maximum correlation value from the plurality of correlation values;
defining a window relative to the maximum correlation value;
calculating a characteristic of the correlation values within the window; and
synchronizing the feedforward filter in accordance with the characteristic.
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 frame synchronization sequence.
5. The method of claim 3 , wherein the synchronization sequence is an ADTB-T frame synchronization sequence.
6. The method of claim 1 , wherein the estimating step includes the step of integrating a plurality of channel impulse response estimates.
7. The method of claim 1 , wherein the window defined during the defining step spans a predetermined number of correlation values.
8. The method of claim 1 , wherein the characteristic of the correlation values is a centroid of the correlation values.
9. The method of claim 1 , wherein the step of identifying comprises the step of determining whether the maximum correlation value exceeds a predetermined threshold.
10. The method of claim 1 , wherein the calculating step includes the step of selecting at least a portion of the correlation values within the window and the characteristic is calculated in accordance with the selected correlation values.
11. The method of claim 10 , wherein the selecting step selects a portion of the correlation values within the window having magnitudes that are greater than a particular value.
12. The method of claim 10 , wherein the selecting step includes a step of defining a region of the window spanning correlation values corresponding to samples received prior to a sample corresponding to the maximum correlation value.
13. The method of claim 10 , wherein the selecting step further includes the step of defining a region of the window spanning correlation values corresponding to samples received after a sample corresponding to the maximum correlation value.
14. The method of claim 1 , wherein the characteristic of the window is calculated in accordance with correlation values within the window that are greater than a further predetermined threshold.
15. The method of claim 10 , further including the step of storing the correlation values in a buffer.
16. 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.
17. The method of claim 16 , 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.
18. The method of claim 17 , wherein the estimating step includes the further step of storing the derived correlation values in a third buffer.
19. An apparatus for controlling a feedforward filter that receives a signal resulting from 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 signal wherein a sequence of samples corresponds to the predetermined sequence of symbols;
means for estimating a channel impulse response of the channel from the sequence of samples, wherein the channel impulse response estimate is represented by a plurality of correlation values;
means for identifying a maximum correlation value from the plurality of correlation values;
means for defining a window relative to the maximum correlation value;
means for calculating a characteristic of the correlation values within the window; and
means for synchronizing the feedforward filter in accordance with the characteristic.
20. The apparatus of claim 19 , wherein the synchronizing means include means for determining a temporal location of the sequence of samples corresponding to the predetermined sequence of symbols at an output of the feedforward filter.
21. The apparatus of claim 19 , wherein the predetermined sequence of symbols comprises a synchronization sequence.
22. The apparatus of claim 21 , wherein the synchronization sequence is an ATSC frame synchronization sequence.
23. The apparatus of claim 21 , wherein the synchronization sequence is an ADTB-T frame synchronization sequence.
24. A computer-readable medium for controlling a feedforward filter that receives a signal resulting from transmission of a series of symbols through a channel, wherein the series of symbols includes a predetermined sequence of symbols, including having a stored executable instructions for implementing:
a first routine for developing a plurality of samples from the received signal wherein a sequence of sample corresponds to the predetermined sequence of symbols;
a second routine for estimating a channel impulse response of the channel from the sequence of samples, wherein the channel impulse response estimate is represented by a plurality of correlation values;
a third routine for identifying a maximum correlation value from the plurality of correlation values;
a fourth routine for defining a window relative to the maximum correlation value;
a fifth routine for calculating a characteristic of the correlation values within the window; and
a sixth routine for synchronizing the feedforward filter in accordance with the characteristic.
25. The computer-readable medium of claim 24 , wherein the sixth routine includes a routine for determining a temporal location of the sequence of samples corresponding to the predetermined sequence of symbols at an output of the feedforward filter.
26. The computer-readable medium of claim 24 , wherein the predetermined sequence of symbols comprises a synchronization sequence.
27. The computer-readable medium of claim 26 , wherein the synchronization sequence is an ATSC frame synchronization sequence.
28. The computer-readable medium of claim 26 , wherein the synchronization sequence is an ADTB-T frame synchronization sequence.