Direct determination equalizer system

• US 20060215745A1
• Filed: 03/25/2005
• Published: 09/28/2006
• Est. Priority Date: 03/25/2005
• Status: Active Grant

• Current Assignee: Keysight Technologies, Inc.
• Original Assignee: Agilent Technologies, Inc.
• Inventors: Viss, Marlin E., Woodward, Mark J.
• Granted Patent: US 7,852,912 B2
• Time in Patent Office: Days
• US Class Current: 375/229
• CPC Class Codes: H04L 25/0305 using blind adaptation

Abstract

A direct determination equalizer system (“DDES”) for compensating for the deterministic effects of a transmission channel and a data source is disclosed. The DDES may include an equalizer having equalizer-tap coefficients, a cross-correlator configured to receive the first sampled signal and an ideal signal and in response produce a cross-correlated signal, and a processor in signal communication with the equalizer and the cross-correlator. The equalizer is configured to receive a first sampled signal and in response produce an equalized output data signal sequence and the processor is configured to determine the equalizer-tap coefficients from the cross-correlated signal.

Claims

1. A method for compensating for the deterministic effects of a transmission channel on a data source utilizing a direct determination equalizer system (“

DDES”

) having an equalizer, the method comprising;

acquiring a channel output data signal sequence spanning multiple bits;

determining an ideal data signal;

cross-correlating the channel output data signal and the input data signal to produce a cross-correlated signal;

determining the largest value of the cross-correlated signal; and

determining equalizer-tap coefficients for the equalizer.

2. The method of claim 1, wherein determining the equalizer-tap coefficients for the equalizer includes:

producing a set of linear equations based on the cross-correlation sequence; and

solving the set of linear equations.

3. The method of claim 2, wherein cross-correlating the channel output data signal and the input data signal utilizes the relationship

4. The method of claim 3, wherein determining the equalizer-tap coefficients for the equalizer includes:

producing a set of linear equations based on the cross-correlation sequence;

solving the set of linear equations; and

wherein the set of linear equations are produced utilizing the relationship

$\mathrm{ideal\_data}<br><br>\mathrm{\_signal}<br><br>\left(k\right)=\underset{i=0}{\overset{\mathrm{numTaps}-1}{\sum <br><br>}}<br><br>\mathrm{tap}<br><br>\left(i\right)·<br><br>\mathrm{channel\_output}<br><br>\mathrm{\_data}<br><br>\mathrm{\_signal}<br><br>\left(k-\mathrm{round}<br><br>\left(i·<br><br>\left(\mathrm{\tau <br><br>}·<br><br>f_s\right)\right)\right)$

wherein the ideal data signal is “

ideal_data_signal(k),”

the equalizer-tap coefficients are “

tap(i)” and

the channel output data signal is “

channel_output_data_signal,”

wherein “

τ

”

is the desired tap spacing, “

f_s”

is the sampling rate, “

k”

is a sequence index number, “

i”

is an index number, and numTaps−

1 is the total number of equalizer taps in the equalizer.

5. The method of claim 1, wherein determining the ideal data signal includes determining the ideal data signal by sampling the input data signal sequence.

6. The method of claim 1, wherein determining the ideal data signal includes approximating the ideal data signal with an approximating sequence.

7. The method of claim 6,

wherein acquiring a channel output data signal sequence includes sampling the acquired channel output data signal sequence at a sampling rate, and

wherein approximating the ideal data signal includes:

determining a priori information for the ideal data signal;

generating the approximating sequence utilizing the a priori information; and

sampling a logical sequence of bits corresponding to the approximating sequence at the sampling rate to produce the ideal data signal.

8. The method of claim 7, wherein cross-correlating the channel output data signal and the input data signal utilizes the relationship

9. The method of claim 8, wherein determining the equalizer-tap coefficients for the equalizer includes:

producing a set of linear equations based on the cross-correlation sequence;

solving the set of linear equations; and

wherein the set of linear equations are produced utilizing the relationship

$\mathrm{ideal\_data}<br><br>\mathrm{\_signal}<br><br>\left(k\right)=\underset{i=0}{\overset{\mathrm{numTaps}-1}{\sum <br><br>}}<br><br>\mathrm{tap}<br><br>\left(i\right)·<br><br>\mathrm{channel\_output}<br><br>\mathrm{\_data}<br><br>\mathrm{\_signal}<br><br>\left(k-\mathrm{round}<br><br>\left(i·<br><br>\left(\mathrm{\tau <br><br>}·<br><br>f_s\right)\right)\right)$

wherein the ideal data signal is “

ideal_data_signal(k),”

the equalizer-tap coefficients are “

tap(i),” and

the channel output data signal is “

channel_output_data_signal,”

wherein “

τ

”

is the desired tap spacing, “

f_s”

is the sampling rate, “

k”

is a sequence index number, “

i”

is an index number, and numTaps−

1 is the total number of equalizer taps in the equalizer.

10. The method of claim 9, wherein approximating the ideal data signal further includes filtering the produced ideal data signal.

11. The method of claim 6,

wherein acquiring a channel output data signal sequence includes sampling the acquired channel output data signal sequence at a sampling rate, and

wherein approximating the ideal data signal includes:

generating the approximating sequence corresponding to the acquired channel output data signal, the approximating sequence having a sequence of logical bits; and

sampling the logical sequence of bits at the sampling rate to produce the ideal data signal.

12. The method of claim 11, wherein cross-correlating the channel output data signal and the input data signal utilizes the relationship

13. The method of claim 12, wherein determining the equalizer-tap coefficients for the equalizer includes:

producing a set of linear equations based on the cross-correlation sequence;

solving the set of linear equations; and

wherein the set of linear equations are produced utilizing the relationship

$\mathrm{ideal\_data}<br><br>\mathrm{\_signal}<br><br>\left(k\right)=\underset{i=0}{\overset{\mathrm{numTaps}-1}{\sum <br><br>}}<br><br>\mathrm{tap}<br><br>\left(i\right)·<br><br>\mathrm{channel\_output}<br><br>\mathrm{\_data}<br><br>\mathrm{\_signal}<br><br>\left(k-\mathrm{round}<br><br>\left(i·<br><br>\left(\mathrm{\tau <br><br>}·<br><br>f_s\right)\right)\right)$

wherein the ideal data signal is “

ideal_data_signal(k),”

the equalizer-tap coefficients are “

tap(i)” and

the channel output data signal is “

channel_output_data_signal,” and

wherein “

τ

”

is the desired tap spacing, “

f_s”

is the sampling rate, “

k”

is a sequence index number, “

i”

is an index number, and numTaps−

1 is the total number of equalizer taps in the equalizer.

14. A direct determination equalizer system (“

DDES”

) for compensating for the deterministic effects of a transmission channel on a data source, the DDES comprising;

an equalizer having equalizer-tap coefficients, wherein the equalizer is configured to receive a first sampled signal and in response produce an equalized output data signal sequence;

a cross-correlator configured to receive the first sampled signal and an ideal signal and in response produce a cross-correlated signal; and

a processor in signal communication with the equalizer and the cross-correlator, wherein the processor is configured to determine the equalizer-tap coefficients from the cross-correlated signal.

15. The DDES of claim 14, further including a first sampler in signal communication with the transmission channel, the equalizer, and the cross-correlator, wherein the first sampler is configured to sample a channel output data signal sequence from the transmission channel to produce the first sampled signal.

16. The DDES of claim 15, further including:

a second sampler in signal communication with the data source and the cross-correlator, wherein the second sampler is configured to sample an input data signal sequence from the data source and produce the ideal signal; and

a clock in signal communication with both the first sampler and the second sampler,

wherein the clock is configured to produce a clock signal that is passed to the first sampler and the second sampler, and

wherein the clock signal produces the sampling rate for both the first sampler and the second sampler.

17. The DDES of claim 16, further including a detector in signal communication with both the cross-correlator and the processor, wherein the detector is configured to determine the largest value of the cross-correlated signal.

18. The DDES of claim 15, further including:

a sequence generator configured to produce an approximating sequence wherein the approximating sequence approximates the ideal data signal; and

a third sampler in signal communication with both the sequence generator and the cross-correlator, wherein the third sampler is configured to sample the approximating sequence to produce the ideal signal; and

a clock in signal communication with both the first sampler and the third sampler,

wherein the clock is configured to produce a clock signal that is passed to the first sampler and the third sampler, and

wherein the clock signal produces the sampling rate for both the first sampler and the third sampler.

19. The DDES of claim 18, wherein the sequence generator includes a threshold module.

20. The DDES of claim 19, further including a filter in signal communication with both the third sampler and the cross-correlator, wherein the filter is configured to filter the sampled approximating sequence to produce the ideal signal.

21. A signal-bearing medium having software for compensating for the deterministic effects of a transmission channel and a data source utilizing a direct determination equalizer system (“

DDES”

) having an equalizer, the signal-bearing medium comprising;

logic configured for acquiring a channel output data signal sequence spanning multiple bits;

logic configured for determining an ideal data signal;

logic configured for cross-correlating the channel output data signal and the input data signal to produce a cross-correlated signal;

logic configured for determining the largest value of the cross-correlation signal; and

logic configured for determining equalizer-tap coefficients for the equalizer.

22. The signal-bearing medium of claim 21, wherein the logic configured for determining the equalizer-tap coefficients for the equalizer includes:

logic configured for producing a set of linear equations based on the cross-correlation sequence; and

logic configured for solving the set of linear equations.

24. The signal-bearing medium of claim 22, wherein the logic configured for cross-correlating the channel output data signal and the input data signal utilizes the relationship

25. The signal-bearing medium of claim 24, wherein the logic configured for determining the equalizer-tap coefficients for the equalizer includes:

logic configured for producing a set of linear equations based on the cross-correlation sequence;

logic configured for solving the set of linear equations; and

wherein the set of linear equations are produced utilizing the relationship

$\mathrm{ideal\_data}<br><br>\mathrm{\_signal}<br><br>\left(k\right)=\underset{i=0}{\overset{\mathrm{numTaps}-1}{\sum <br><br>}}<br><br>\mathrm{tap}<br><br>\left(i\right)·<br><br>\mathrm{channel\_output}<br><br>\mathrm{\_data}<br><br>\mathrm{\_signal}<br><br>\left(k-\mathrm{round}<br><br>\left(i·<br><br>\left(\mathrm{\tau <br><br>}·<br><br>f_s\right)\right)\right),$

wherein the ideal data signal is “

ideal_data_signal(k),”

the equalizer-tap coefficients are “

tap(i)” and

the channel output data signal is “

channel_output_data_signal,” and

wherein “

τ

”

is the desired tap spacing, “

f_s”

is the sampling rate, “

k”

is a sequence index number, “

i”

is an index number, and numTaps−

1 is the total number of equalizer taps in the equalizer.

26. The signal-bearing medium of claim 22, wherein the logic configured for solving includes logic configured for solving the set of linear equations utilizing linear regression.

27. The signal-bearing medium of claim 21, wherein the logic configured for determining the ideal data signal includes logic configured for determining the ideal data signal by sampling the input data signal sequence.

28. The signal-bearing medium of claim 21, wherein the logic configured for determining the ideal data signal includes logic configured for approximating the ideal data signal with an approximating sequence.

29. The signal-bearing medium of claim 28,

wherein the logic configured for acquiring a channel output data signal sequence includes logic configured for sampling the acquired channel output data signal sequence at a sampling rate, and

wherein the logic configured for approximating the ideal data signal includes:

logic configured for determining a priori information for the ideal data signal;

logic configured for generating the approximating sequence utilizing the a priori information; and

logic configured for sampling a logical sequence of bits corresponding to the approximating sequence at the sampling rate to produce the ideal data signal.

30. The signal-bearing medium of claim 29, wherein the logic configured for cross-correlating the channel output data signal and the input data signal utilizes the relationship

31. The signal-bearing medium of claim 30, wherein the logic configured for determining the equalizer-tap coefficients for the equalizer includes:

logic configured for producing a set of linear equations based on the cross-correlation sequence;

logic configured for solving the set of linear equations; and

wherein the set of linear equations are produced utilizing the relationship

$\mathrm{ideal\_data}<br><br>\mathrm{\_signal}<br><br>\left(k\right)=\underset{i=0}{\overset{\mathrm{numTaps}-1}{\sum <br><br>}}<br><br>\mathrm{tap}<br><br>\left(i\right)·<br><br>\mathrm{channel\_output}<br><br>\mathrm{\_data}<br><br>\mathrm{\_signal}<br><br>\left(k-\mathrm{round}<br><br>\left(i·<br><br>\left(\mathrm{\tau <br><br>}·<br><br>f_s\right)\right)\right),$

wherein the ideal data signal is “

ideal_data_signal(k),”

the equalizer-tap coefficients are “

tap(i),” and

the channel output data signal is “

channel_output_data_signal,” and

wherein “

τ

”

is the desired tap spacing, “

f_s”

is the sampling rate, “

k”

is a sequence index number, “

i”

is an index number, and numTaps−

1 is the total number of equalizer taps in the equalizer.

32. The signal-bearing medium of claim 28,

wherein the logic configured for acquiring a channel output data signal sequence includes logic configured for sampling the acquired channel output data signal sequence at a sampling rate, and

wherein the logic configured for approximating the ideal data signal includes:

logic configured for generating the approximating sequence corresponding to the acquired channel output data signal, the approximating sequence having a sequence of logical bits; and

logic configured for sampling the logical sequence of bits at the sampling rate to produce the ideal data signal.

33. The signal-bearing medium of claim 32, wherein the logic configured for cross-correlating the channel output data signal and the input data signal utilizes the relationship

34. The signal-bearing medium of claim 33, wherein the logic configured for determining the equalizer-tap coefficients for the equalizer includes:

logic configured for producing a set of linear equations based on the cross-correlation sequence;

logic configured for solving the set of linear equations; and

wherein the set of linear equations are produced utilizing the relationship

$\mathrm{ideal\_data}<br><br>\mathrm{\_signal}<br><br>\left(k\right)=\underset{i=0}{\overset{\mathrm{numTaps}-1}{\sum <br><br>}}<br><br>\mathrm{tap}<br><br>\left(i\right)·<br><br>\mathrm{channel\_output}<br><br>\mathrm{\_data}<br><br>\mathrm{\_signal}<br><br>\left(k-\mathrm{round}<br><br>\left(i·<br><br>\left(\mathrm{\tau <br><br>}·<br><br>f_s\right)\right)\right),$

wherein the ideal data signal is “

ideal_data_signal(k),”

the equalizer-tap coefficients are “

tap(i)” and

the channel output data signal is “

channel_output_data_signal,” and

wherein “

τ

”

is the desired tap spacing, “

f_s”

is the sampling rate, “

k”

is a sequence index number, “

i”

is an index number, and numTaps−

1 is the total number of equalizer taps in the equalizer.