Patent Grant
9224421
The present invention is directed to systems and methods for magnetoresistive asymmetry (MRA) estimation.
Systems and methods for magnetoresistive asymmetry estimation may include, but are not limited to, operations for: receiving a magnetic read head transducer output; computing a mean value of the magnetic read head transducer output; computing a median value of the magnetic read head transducer output; and applying a correction coefficient to a magnetic read head detector input according to at least the mean value of the magnetic read head transducer output and the median value of the magnetic read head transducer output.
The numerous advantages of the disclosure may be better understood by those skilled in the art by referencing the accompanying figures in which:
Referring to
The data storage device 101 may be a magnetic recording storage device, (e.g. a hard drive, a component drive of a redundant array of independent disks (RAID), or any other magnetic recording medium) including a magnetically recordable media 104 readable by a read head 105. The read head 105 may include one or more transducers 106 and a detector 107 configured to translate magnetically recorded data stored on the magnetically recordable media 104 into the signal path 103 for transmission to the host device 102.
In a specific embodiment, as shown in
Such transducers 106 in read heads used for magnetic recording may be non-linear in nature and, as such, may exhibit magnetoresistive asymmetry (MRA) distortion. MRA distortion may be modeled as a quadratic nonlinearity that adds a scaled and squared signal component back to a read signal path (e.g. signal path 103).
To compensate for this distortion, read channels may include an MRA correction block 108. This MRA correction block 108 may apply a correction coefficient to be programmed appropriately for proper functioning. The coefficient may be set using a decision-directed feedback loop 109 that employs decisions by the detector 107 to modify the input to the detector 107. Such a method relies on good detector 107 decision quality and may converge relatively slowly. With unstable transducers 106 that exhibit sudden changes in distortion, such a decision-directed approach may be problematic as the MRA correction block 108 may not be able to respond in a timely manner. As such a non-decision-directed approach may be employed.
For example, as shown in
The mean of the detector output signal 110 may be computed using direct averaging of the output signal 110. For example, as shown in
Further, in order to compute a median value of the detector output signal 110, samples of the output signal 110 may be sorted and the median value selected. In another embodiment, as shown in
With an appropriately chosen median value update factor (MVUF) (e.g. a 2% adjustment factor), the median value 114 may converge (e.g. by an end of a signal sector or fragment) to the median of all the samples in the sector or fragment.
Referring again to
It is believed that the present disclosures and many of their attendant advantages will be understood by the foregoing description. It is also believed that it will be apparent that various changes may be made in the form, construction and arrangement of the components thereof without departing from the scope and spirit of the invention or without sacrificing all of its material advantages. The form herein before described being merely an explanatory embodiment thereof. It is the intention of the following claims to encompass and include such changes.
The foregoing detailed description may include set forth various embodiments of the devices and/or processes via the use of block diagrams, flowcharts, and/or examples. Insofar as such block diagrams, flowcharts, and/or examples contain one or more functions and/or operations, it will be understood by those within the art that each function and/or operation within such block diagrams, flowcharts, or examples may be implemented, individually and/or collectively, by a wide range of hardware, software, firmware, or virtually any combination thereof. In one embodiment, several portions of the subject matter described herein may be implemented via Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), digital signal processors (DSPs), or other integrated formats. However, those skilled in the art will recognize that some aspects of the embodiments disclosed herein, in whole or in part, may be equivalently implemented in integrated circuits, as one or more computer programs running on one or more computers (e.g., as one or more programs running on one or more computer systems), as one or more programs running on one or more processors (e.g., as one or more programs running on one or more microprocessors), as firmware, or as virtually any combination thereof, and that designing the circuitry and/or writing the code for the software and or firmware would be well within the skill of one of skill in the art in light of this disclosure.
In addition, those skilled in the art will appreciate that the mechanisms of the subject matter described herein may be capable of being distributed as a program product in a variety of forms, and that an illustrative embodiment of the subject matter described herein applies regardless of the particular type of signal bearing medium used to actually carry out the distribution. Examples of a signal bearing medium include, but may be not limited to, the following: a recordable type medium such as a floppy disk, a hard disk drive, a Compact Disc (CD), a Digital Video Disk (DVD), a digital tape, a computer memory, etc.; and a transmission type medium such as a digital and/or an analog communication medium (e.g., a fiber optic cable, a waveguide, a wired communications link, a wireless communication link (e.g., transmitter, receiver, transmission logic, reception logic, etc.), etc.).
Those having skill in the art will recognize that the state of the art has progressed to the point where there may be little distinction left between hardware, software, and/or firmware implementations of aspects of systems; the use of hardware, software, and/or firmware may be generally (but not always, in that in certain contexts the choice between hardware and software may become significant) a design choice representing cost vs. efficiency tradeoffs. Those having skill in the art will appreciate that there may be various vehicles by which processes and/or systems and/or other technologies described herein may be effected (e.g., hardware, software, and/or firmware), and that the preferred vehicle will vary with the context in which the processes and/or systems and/or other technologies may be deployed. For example, if an implementer determines that speed and accuracy may be paramount, the implementer may opt for a mainly hardware and/or firmware vehicle; alternatively, if flexibility may be paramount, the implementer may opt for a mainly software implementation; or, yet again alternatively, the implementer may opt for some combination of hardware, software, and/or firmware. Hence, there may be several possible vehicles by which the processes and/or devices and/or other technologies described herein may be effected, none of which may be inherently superior to the other in that any vehicle to be utilized may be a choice dependent upon the context in which the vehicle will be deployed and the specific concerns (e.g., speed, flexibility, or predictability) of the implementer, any of which may vary. Those skilled in the art will recognize that optical aspects of implementations will typically employ optically oriented hardware, software, and or firmware.
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