Adaptive correction of symmetrical and asymmetrical saturation in magnetic recording devices

A read channel comprising:

• a preprocessor for receiving a first signal and producing a second signal from the first signal using current values of a positive coefficient, a zero coefficient, and a negative coefficient;
• an interpolator for producing a third signal based on the second signal;
• and
• a slicer for producing a fourth signal from a third signal by estimating a level for the third signal,
• wherein:
• the fourth signal is at one of three levels consisting of a positive level, a zero level, and a negative level;
• for every n first signals received by the preprocessor, the current value of one of the positive coefficient, the zero coefficient, and the negative coefficient is adjusted depending on which of the three levels the fourth signal is at, and
• wherein for every n first signals received by the preprocessor, the current value of one of the positive coefficient, the zero coefficient, and the negative coefficient is adjusted according to:
• Kpos=Kpos−μa•(χk−{circumflex over (χ)}k) if {circumflex over (χ)}k=+1,
• Kzer=Kzer−μb•(χk) if {circumflex over (χ)}k=0, and
• Kneg=Kneg−μa•(χk−{circumflex over (χ)}k) if {circumflex over (χ)}k=−1;
• where:
• Kpos denotes the positive coefficient;
• Kzer denotes the zero coefficient;
• Kneg denotes the negative coefficient;
• χk denotes the third signal;
• {circumflex over (χ)}k denotes the fourth signal;
• and
• μa and μb are positive constants.

A magnetic recording device comprising a read channel comprising:

• a preprocessor for receiving a first signal and producing a second signal from the first signal using current values of a positive coefficient, a zero coefficient, and a negative coefficient;
• an interpolator for producing a third signal based on the second signal;
• and
• a slicer for producing a fourth signal from the third signal by estimating a level for the third signal,
• wherein:
• the fourth signal is at one of three levels consisting of a positive level, a zero level, and a negative level;
• for every n first signals received by the preprocessor, the current value of one of the positive coefficient, the zero coefficient, and the negative coefficient is adjusted depending on which of the three levels the fourth signal is at, and
• wherein the preprocessor produces the second signal from the first signal according to:
• γo=γi+Kpos(γi)2+Kzer if γi>0, and
• γo=γi+Kneg(γi)2+Kzer otherwise;
• where:
• γi denotes the first signal;
• γo denotes the second signal;
• Kpos denotes the positive coefficient;
• Kzer denotes the zero coefficient;
• and
• Kneg denotes the negative coefficient.

A method comprising:

• for each of a plurality of first signals,
• producing, by a preprocessor, a second signal from the first signal current values of a positive coefficient, a zero coefficient, and a negative coefficient;
• producing, by an interpolator, a third signal based on the second signal;
• and
• producing, by a slicer, a fourth signal from a third signal by estimating a level for the third signal,
• wherein:
• the fourth signal is at one of three levels consisting of a positive level, a zero level, and a negative level;
• for every n first signals, the current value of one of the positive coefficient, the zero coefficient, and the negative coefficient is adjusted depending on which of the three levels the fourth signal is at, and
• wherein the preprocessor produces the second signal from the first signal according to:
• γo=γi+Kpos(γi)2+Kzer if γi>0, and
• γo=γi+Kneg(γi)2+Kzer otherwise;
• where:
• γi denotes the first signal;
• γo denotes the second signal;
• Kpos denotes the positive coefficient;
• Kzer denotes the zero coefficient;
• and
• Kneg denotes the negative coefficient.

A method comprising:

• for each of a plurality of first signals,
• producing, by a preprocessor, a second signal from the first signal current values of a positive coefficient, a zero coefficient, and a negative coefficient;
• producing, by an interpolator, a third signal based on the second signal;
• and
• producing, by a slicer, a fourth signal from a third signal by estimating a level for the third signal,
• wherein:
• the fourth signal is at one of three levels consisting of a positive level, a zero level, and a negative level;
• for every n first signals, the current value of one of the positive coefficient, the zero coefficient, and the negative coefficient is adjusted depending on which of the three levels the fourth signal is at, and
• wherein for every n first signals, the current value of one of the positive coefficient, the zero coefficient, and the negative coefficient is adjusted according to:
• Kpos=Kpos−μa•(χk−{circumflex over (χ)}k) if {circumflex over (χ)}k=+1,
• Kzer=Kzer−μb•(χk) if {circumflex over (χ)}k=0, and
• Kneg=Kneg−μa•(χk−{circumflex over (χ)}k) if {circumflex over (χ)}k=−1;
• where:
• Kpos denotes the positive coefficient;
• Kzer denotes the zero coefficient;
• Kneg denotes the negative coefficient;
• χk denotes the third signal;
• {circumflex over (χ)}k denotes the fourth signal;
• and
• μa and μb are positive constants.