Method and apparatus for artifact signal reduction in systems of mismatched interleaved digitizers
View Patent ↗An artifact signal correction system may include a mixing component to generate a waveform corresponding to an artifact such as an error tone, whereupon that waveform may be combined with the input waveform to substantially eliminate the artifact. In preferred embodiments, a method and apparatus for reducing spurious tones in systems of mismatched interleaved digitizers due to interleave error is provided. In various embodiments the method may include reversing the frequency content of an input signal, converting the reversed signal into interleave artifact content, delaying the input signal along a parallel path, and then subtracting the interleave content from the delayed input signal.
1. An artifact signal correction method comprising the steps of:
receiving an input signal;
digitizing the input signal with a plurality of interleaved digitizers;
reversing the frequency content of the digitized input signal to generate a reversed frequency waveform;
deriving an artifact content from the reversed frequency waveform, said artifact content corresponding to at least one artifact generated in accordance with the digitizing of the input signal by the plurality of interleaved digitizers;
delaying the input signal; and
subtracting the artifact content from the delayed input signal to substantially reduce the at least one artifact.
2. The method of claim 1 wherein the artifact is a tone.
3. The method of claim 2 , wherein the artifact is a spurious tone.
4. The method of claim 3 , wherein the frequency of the spurious tone (n) is in accordance with the equation:
n=N−n in
where n is a frequency of the spurious tone, N is one half an overall sample frequency, and n in is the input frequency.
5. The method of claim 1 , wherein the artifact is caused at least in part by the digitizing of the input signal by the plurality of interleaved digitizers having one or more mismatches therebetween.
6. The method of claim 1 , wherein the digitizers are analog-to-digital converters.
7. The method of claim 1 , wherein reversing the frequency content comprises mixing the input signal with a periodic digital waveform.
8. The method of claim 1 , wherein deriving the artifact content comprises transforming the reversed frequency waveform.
9. The method of claim 1 , wherein delaying the input signal substantially synchronizes the input waveform with the artifact content.
10. The method of claim 1 , wherein subtracting comprises combining the input signal with an artifact content that is the substantial inverse of the artifact.
11. The method of claim 1 , wherein the interleaved digitizers are disposed on separate dies.
12. The method of claim 1 , wherein the at least one artifact comprises an error signal caused at least in part by phase mismatch between two or more signals, each signal being generated from one of the plurality of interleaved digitizers when employed to digitize the input signal.
13. The artifact signal correction method of claim 1 , wherein the at least one artifact is caused by crossover region phase misalignment.
14. The method of claim 1 , wherein a frequency of the spurious tone is a function of the input signal.
15. An artifact signal correction method comprising the steps of:
providing an input signal having at least one artifact;
reversing the frequency content of the input signal to generate a reversed frequency waveform;
deriving an artifact content from the reversed frequency waveform, said artifact content corresponding to the at least one artifact;
delaying the input signal; and
subtracting the artifact content from the delayed input signal to substantially reduce the at least one artifact,
wherein reversing the frequency content of the input signal comprises flipping the input signal about a frequency at substantially one half an overall sample frequency.
16. A system for reducing interleave error, comprising:
means for reversing the frequency content of an input signal;
a converter for converting the reversed frequency content into interleave artifact content;
a delay element for delaying the input signal; and
a summing device for subtracting the interleave artifact from the delayed input signal, wherein the reversing means flips the frequency content of the input signal about a frequency at substantially one half an overall sample frequency.
17. A system for reducing interleave error, comprising:
a receiver for receiving an input signal;
a plurality of interleaved digitizers for digitizing the input signal;
means for reversing the frequency content of the digitized input signal;
a converter for converting the reversed frequency content into interleave artifact content, the artifact content corresponding at least one artifact generated in accordance with the digitizing of the input signal by the plurality of interleaved digitizers;
a delay element for delaying the input signal; and
a summing device for subtracting the interleave artifact from the delayed input signal.
18. The system of claim 17 , wherein the interleave error is a spurious tone.
19. The system of claim 18 , wherein the frequency of the spurious tone (n) is in accordance with the equation:
n=N−n in
where n is a frequency of the spurious tone, N is one half an overall sample frequency, and n in is the input frequency.