Skew-tolerant reader set selection in array-reader based magnetic recording
A method for enhancing read performance in an ARMR system includes: obtaining CTS information for a plurality of readers in a multi-reader head of the ARMR system, the CTS information defining a relationship between skew angle and CTS between respective combinations of subsets of the readers; determining, as a function of the CTS information, a given one of the combinations of subsets of the readers which provides enhanced read performance among a total number of combinations of subsets of the readers for each of a plurality of skew angles; and selecting, for subsequent processing by a read channel in the ARMR system, the given one of the combinations of subsets of the readers determined to provide enhanced read performance for a given one of the skew angles corresponding to a zone in which the multi-reader head is operating.
1. A method for enhancing read performance in an array-reader based magnetic recording (ARMR) system, the method comprising:
obtaining cross-track separation (CTS) information for a plurality of readers in a multi-reader head of the ARMR system, the CTS information defining a relationship between skew angle and CTS between respective combinations of subsets of the plurality of readers;
determining, as a function of the CTS information, a given one of the combinations of subsets of the plurality of readers which provides enhanced read performance among a total number of combinations of subsets of the plurality of readers for each of a plurality of skew angles; and
selecting, for subsequent processing by a read channel in the ARMR system, the given one of the combinations of subsets of the plurality of readers determined to provide enhanced read performance for a given one of the plurality of skew angles corresponding to a zone in which the multi-reader head is operating.
2. The method of claim 1 , wherein the CTS information defines a relationship between skew angle and CTS between respective pairs of readers in a plurality of combinations of pairs of readers.
3. The method of claim 1 , further comprising configuring the plurality of readers in the multi-reader head such that at least a subset of the readers are within a CTS range configured to provide prescribed read performance as a function of whether the ARMR system is operating in a multiple-input single-output mode or a multiple-input multiple-output mode.
4. The method of claim 3 , wherein the multi-reader head is configured such that at least a subset of the plurality of readers are within a CTS of 0.3 track pitch (TP) of one another for multiple-input single-output operation, and at least the subset of the readers are within a range of about 0.7 to 0.9 TP of one another for multiple-input multiple-output operation.
5. The method of claim 1 , further comprising locating the multi-reader head over at least one target track of a magnetic storage medium being read based on the CTS information corresponding to the given one of the combinations of subsets of available readers determined to provide enhanced read performance.
6. The method of claim 1 , further comprising configuring at least a subset of the plurality of readers in the multi-reader head such that adjacent readers are located on opposite sides, in a cross-track direction, of a centerline of the multi-reader head, the centerline being oriented in a down-track direction.
7. The method of claim 1 , further comprising storing, for each of at least a subset of the plurality of skew angles, a corresponding one of the combinations of subsets of the plurality of readers determined to provide enhanced read performance among the total number of combinations of subsets of the plurality of readers.
8. The method of claim 7 , wherein selecting the given one of the combinations of subsets of the plurality of readers determined to provide enhanced read performance comprises retrieving one of the stored combinations of subsets of the plurality of readers which provides enhanced read performance as a function of the zone in which the multi-reader head is operating.
9. The method of claim 1 , wherein selecting the given one of the combinations of subsets of the plurality of readers determined to provide enhanced read performance comprises:
detecting a zone in which the multi-reader head is operating; and
changing the given one of the combinations of subsets of the plurality of readers determined to provide enhanced read performance as a function of the detected zone in which the multi-reader head is operating.
10. The method of claim 1 , wherein determining the given one of the combinations of subsets of the plurality of readers which provides enhanced read performance comprises:
determining cross-track separation (CTS) variation as a function of skew angle for each combination of subsets of the plurality of readers in the multi-reader head over a prescribed range of skew angles; and
determining which combinations of subsets of the plurality of readers have a CTS that is within a prescribed range of CTS variation for each of at least a subset of skew angles in the prescribed range of skew angles.
11. The method of claim 10 , wherein determining CTS variation for each combination of subsets of the plurality of readers comprises estimating CTS information for the readers from read-back signal processing.
12. The method of claim 1 , further comprising supplying read signals generated by respective readers in the given one of the combinations of subsets of the plurality of readers determined to provide enhanced read performance to corresponding analog front ends in the read channel.
13. The method of claim 1 , wherein selecting the given one of the combinations of subsets of the plurality of readers determined to provide enhanced read performance comprises:
determining whether the multi-reader head is to be used in one of a multiple-input single-output mode of operation and a multiple-input multiple-output mode of operation; and
selecting a given one of the combinations of subsets of the plurality of readers determined to provide enhanced read performance as a function of the mode of operation of the multi-reader head.
14. The method of claim 1 , further comprising generating a data output signal indicative of a logical state of information read from at least one target track of a magnetic storage medium being read, the data output signal being a function of read signals corresponding to the given one of the combinations of subsets of the plurality of readers determined to provide enhanced read performance for the zone in which the multi-reader head is operating.
15. The method of claim 14 , wherein the data output signal comprises one of a hard decision corresponding to a particular logical state of information read from the at least one target track, or a soft decision corresponding to a probability relating to the particular logical state of the information read from the target track.
16. An apparatus for enhancing read performance in an array-reader based magnetic recording (ARMR) system, the apparatus comprising:
a controller configured to receive, as inputs, a plurality of read signals from a corresponding plurality of readers in a multi-reader head of the ARMR system and to select, as outputs, a subset of the plurality of read signals corresponding to a given one of respective combinations of subsets of the plurality of readers which provides enhanced read performance among a total number of combinations of subsets of the plurality of readers for each of a plurality of skew angles;
a plurality of analog front ends, each of the analog front ends being configured to receive a corresponding read signal from the subset of the plurality of read signals output by the controller and to generate an analog signal as a function of the corresponding read signal;
a plurality of analog-to-digital converters coupled with the respective plurality of analog front ends, each of the analog-to-digital converters being configured to receive a given one of the analog signals generated by a corresponding one of the plurality of analog front ends and to generate, as a function of the given analog signal, a digital read signal; and
a joint equalizer coupled with the plurality of analog-to-digital converters, the joint equalizer being configured to receive the respective digital read signals generated by the plurality of analog-to-digital converters and to generate an equalized output signal.
17. The apparatus of claim 16 , further comprising a detector coupled with the joint equalizer, the detector being configured to generate a data output signal indicative of a logical state of information read from at least one target track of a magnetic storage medium being read, the data output signal being a function of read signals corresponding to the given one of the combinations of subsets of the plurality of readers determined to provide enhanced read performance for a zone in which the multi-reader head is operating.
18. The apparatus of claim 16 , further comprising a zone table coupled with the controller, the zone table being configured to store, for each of at least a subset of the plurality of skew angles, a corresponding one of the combinations of subsets of the plurality of readers determined to provide enhanced read performance among the total number of combinations of subsets of the plurality of readers.
19. The apparatus of claim 18 , wherein the controller is configured to retrieve one of the stored combinations of subsets of the plurality of readers which provides enhanced read performance as a function of a zone in which the multi-reader head is operating.
20. The apparatus of claim 16 , wherein the controller is configured to determine cross-track separation (CTS) variation as a function of skew angle for each combination of subsets of the plurality of readers in the multi-reader head over a prescribed range of skew angles, and to determine which combinations of subsets of the plurality of readers have a CTS that is within a prescribed range of CTS variation for each of at least a subset of skew angles in the prescribed range of skew angles.
21. The apparatus of claim 20 , wherein the controller is configured to determine CTS variation for each combination of subsets of the plurality of readers by estimating CTS information for the readers from read-back signal processing.
22. The apparatus of claim 16 , wherein the controller is configured to detect a zone in which the multi-reader head is operating, and to change the given one of the combinations of subsets of the plurality of readers determined to provide enhanced read performance as a function of the detected zone in which the multi-reader head is operating.
23. The apparatus of claim 16 , wherein the controller is configured to determine whether the multi-reader head is to be used in one of a multiple-input single-output mode of operation and a multiple-input multiple-output mode of operation, and to select the given one of the combinations of subsets of the plurality of readers determined to provide enhanced read performance as a function of the mode of operation of the multi-reader head.
24. The apparatus of claim 16 , wherein at least a portion of the apparatus is fabricated in an integrated circuit.
25. The apparatus of claim 16 , wherein at least a subset of the plurality of analog-to-digital converters are configured to exchange information with one another.
26. A data storage system, comprising:
a plurality of storage devices, wherein at least one of the plurality of storage devices comprises:
a multi-reader array head;
a controller configured to receive, as inputs, a plurality of read signals from a corresponding plurality of readers in the multi-reader head and to select, as outputs, a subset of the plurality of read signals corresponding to a given one of respective combinations of subsets of the plurality of readers which provides enhanced read performance among a total number of combinations of subsets of the plurality of readers for each of a plurality of skew angles;
a plurality of analog front ends, each of the analog front ends being configured to receive a corresponding read signal from the subset of the plurality of read signals output by the controller and to generate an analog signal as a function of the corresponding read signal;
a plurality of analog-to-digital converters coupled with the respective plurality of analog front ends, each of the analog-to-digital converters being configured to receive a given one of the analog signals generated by a corresponding one of the plurality of analog front ends and to generate, as a function of the given analog signal, a digital read signal; and
a joint equalizer coupled with the plurality of analog-to-digital converters, the joint equalizer being configured to receive the respective digital read signals generated by the plurality of analog-to-digital converters and to generate an equalized output signal.