Multi-track data readers with iterative inter-track interference cancellation

1. An apparatus for two-dimensional magnetic recording, comprising:

an array reader comprising a plurality of read sensors configured to read data from at least one track on a storage medium;

a first two-dimensional equalizer circuit comprising a first input for receiving signals derived from each of the plurality of read sensors, wherein the first two-dimensional equalizer circuit generates a first equalized output;

a first iterative inter-track interference cancellation circuit, the first iterative inter-track interference cancellation circuit operable to cancel inter-track interference in the first equalized output;

a second two-dimensional equalizer circuit comprising a second input for receiving signals derived from each of the plurality of read sensors, wherein the second two-dimensional equalizer circuit generates a second equalized output; and

a second iterative inter-track interference cancellation circuit, the second iterative inter-track interference cancellation circuit operable to cancel inter-track interference in the second equalized output.

2. The apparatus of claim 1 , wherein the plurality of read sensors in the array reader are spaced to read data from two tracks simultaneously on the storage medium.

3. The apparatus of claim 1 , further comprising a first data detector with one-dimensional trellises configured to detect data values in the first equalized output after the inter-track interference cancellation and a second data detector with one-dimensional trellises configured to detect data values in the second equalized output after the inter-track interference cancellation.

4. The apparatus of claim 3 , further comprising a plurality of data decoder circuits, each configured to decode detected data from one of the first and second data detectors to yield decoder outputs.

5. The apparatus of claim 4 , wherein the decoder outputs comprise soft decisions.

6. The apparatus of claim 4 , wherein the decoder outputs comprise hard decisions.

7. The apparatus of claim 4 , wherein the first and second iterative inter-track interference cancellation circuits each comprise a decoder input configured to receive the decoder outputs, wherein the first and second iterative inter-track interference cancellation circuits, the first and second data detectors and the plurality of data decoder circuits are configured to process data iteratively.

8. The apparatus of claim 7 , wherein the equalized output from each of the two-dimensional equalizer circuits is processed in a different data path by a different one of the iterative inter-track interference cancellation circuits, data detectors and data decoder circuits, and wherein the decoder inputs on the iterative inter-track interference cancellation circuits are each connected to one of the data decoder circuits from a different one of the data paths.

9. The apparatus of claim 8 , wherein the first and second iterative inter-track interference cancellation circuits each comprise a detector input configured to receive an output from one of the data detectors in a different one of the data paths.

10. The apparatus of claim 7 , wherein the first and second iterative inter-track interference cancellation circuits are configured to cancel inter-track interference based at least in part on the decoder inputs after a first global iteration in the iterative inter-track interference cancellation circuits, the data detectors and the data decoder circuits.

11. The apparatus of claim 3 , wherein the first and second iterative inter-track interference cancellation circuits each comprise a detector input configured to receive an output from a different one of the data detectors.

12. The apparatus of claim 4 , wherein the first and second iterative inter-track interference cancellation circuits comprise filters with tap coefficients adapted based at least in part on cross-track strength information derived from the detected data and the decoder outputs.

13. The apparatus of claim 1 , wherein the first and second iterative inter-track interference cancellation circuits are configured to remove a frequency offset in signals read simultaneously from different tracks on the storage medium.

14. The apparatus of claim 1 , further comprising a plurality of loop detectors, wherein the first and second iterative inter-track interference cancellation circuits operate a first time for each track based on detected outputs from the loop detectors.

15. A magnetic recording storage system for two-dimensional magnetic recording, the magnetic recording storage system comprising:

an array reader comprising a plurality of read sensors configured to read data from at least one track on a storage medium;

a first two-dimensional equalizer circuit comprising a first input for receiving signals derived from each of the plurality of read sensors, wherein the first two-dimensional equalizer circuit generates a first equalized output;

a first iterative inter-track interference cancellation circuit, the first iterative inter-track interference cancellation circuit operable to cancel inter-track interference in the first equalized output;

a second two-dimensional equalizer circuit comprising a second input for receiving signals derived from each of the plurality of read sensors, wherein the second two-dimensional equalizer circuit generates a second equalized output; and

a second iterative inter-track interference cancellation circuit, the second iterative inter-track interference cancellation circuit operable to cancel inter-track interference in the second equalized output.

16. The magnetic recording storage system of claim 15 , wherein the plurality of read sensors in the array reader are spaced to read data from two tracks simultaneously on the storage medium.

17. The magnetic recording storage system of claim 15 , further comprising a first data detector with one-dimensional trellises configured to detect data values in the first equalized output after the inter-track interference cancellation and a second data detector with one-dimensional trellises configured to detect data values in the second equalized output after the inter-track interference cancellation.

18. A method for two-dimensional magnetic recording, the method comprising:

providing an array reader comprising a plurality of read sensors configured to read data from at least one track on a storage medium;

providing a first two-dimensional equalizer circuit comprising a first input for receiving signals derived from each of the plurality of read sensors, wherein the first two-dimensional equalizer circuit generates a first equalized output;

providing a first iterative inter-track interference cancellation circuit, the first iterative inter-track interference cancellation circuit operable to cancel inter-track interference in the first equalized output;

providing a second two-dimensional equalizer circuit comprising a second input for receiving signals derived from each of the plurality of read sensors, wherein the second two-dimensional equalizer circuit generates a second equalized output; and

providing a second iterative inter-track interference cancellation circuit, the second iterative inter-track interference cancellation circuit operable to cancel inter-track interference in the second equalized output.

19. The method of claim 18 , wherein the plurality of read sensors in the array reader are spaced to read data from two tracks simultaneously on the storage medium.

20. The method of claim 18 , the method further comprising providing a first data detector with one-dimensional trellises configured to detect data values in the first equalized output after the inter-track interference cancellation and a second data detector with one-dimensional trellises configured to detect data values in the second equalized output after the inter-track interference cancellation.