Measuring and correcting asymmetry in magnetic recording devices
View Patent ↗An asymmetry compensator for measuring and correcting of asymmetry in magnetic recording devices. The magnetic recording device includes a read head, an asymmetry compensator, a data decoder, and an analog-to-digital converter. The read head produces a read data signal that contains potential errors due to asymmetry. The read data signal is processed into a compensated data signal by the asymmetry compensator. The asymmetry compensator includes a power of two squaring device, a gamma amplifier, and a summing junction connected in a feed forward manner. The gamma amplifier uses an approach involving, for a positive isolated pulse, the amplitude of the positive pulse and the undershoot and, for a negative isolated pulse, the amplitude of the negative pulse and the overshoot. The approach further involves probabilities and weights in a weighted average to account for any variations with frequency. The approach may be performed in either the analog or digital domain.
1. A magnetic recording device comprising:
a read head for reading magnetic fluxes on a magnetic media, the read head having an output from which is transmitted a read data signal;
an asymmetry compensator for at least reducing an affect of non-linear asymmetry in the read data signal, the asymmetry compensator having an input coupled to the output of the read head, the asymmetry compensator comprising a gamma amplifier whose compensation of the read data signal depends at least in part on an amplitude of a positive pulse in the read data signal and an amplitude of an undershoot relative to the positive pulse in the read data signal, and the asymmetry compensator having an output from which is transmitted a compensated data signal;
a data decoder for reading encoded data from the compensated data signal, the data decoder having an input coupled to the output of the asymmetry compensator; and
an analog-to-digital (A/D) converter for converting analog data to digital data;
wherein the compensation of the read data signal by the gamma amplifier further depends at least in part on an amplitude of a negative pulse in the read data signal and an amplitude of an overshoot relative to the negative pulse in the read data signal; and
wherein the compensation of the read data signal by the gamma amplifier further depends at least in part on the width of a wave form in a pulse in the read data signal.
2. A magnetic recording device comprising:
a read head for reading magnetic fluxes on a magnetic media, the read head having an output from which is transmitted a read data signal;
an asymmetry compensator for at least reducing an affect of non-linear asymmetry in the read data signal, the asymmetry compensator having an input coupled to the output of the read head, the asymmetry compensator comprising a gamma amplifier whose compensation of the read data signal depends at least in part on an amplitude of a positive pulse in the read data signal and an amplitude of an undershoot relative to the positive pulse in the read data signal, and the asymmetry compensator having an output from which is transmitted a compensated data signal;
a data decoder for reading encoded data from the compensated data signal, the data decoder having an input coupled to the output of the asymmetry compensator;
an analog-to-digital (A/D) converter for converting analog data to digital data;
wherein the compensation of the read data signal by the gamma amplifier further depends at least in part on an amplitude of a negative pulse in the read data signal and an amplitude of an overshoot relative to the negative pulse in the read data signal; and
wherein the asymmetry compensator further comprises:
a power of two squaring device having an input and an output; and
a summing junction having a first input, a second input, and an output, wherein the input of the power of two squaring device is coupled to the input of the asymmetry compensator and the second input of the summing junction, the output of the power of two squaring device is coupled to an input of the gamma amplifier, an output of the gamma amplifier is coupled to the first input of the summing junction, and the output of the summing junction is coupled to the output of the asymmetry compensator.
3. A method for at least reducing an affect of non-linear asymmetry in a read data signal of a magnetic recording device, the method comprising:
receiving a read data signal;
processing the read data signal into a compensated data signal in a non-linear asymmetry compensator of the magnetic recording device, the asymmetry compensator comprising a gamma amplifier whose compensation of the read data signal depends at least in part on an amplitude of a positive pulse in the read data signal and an amplitude of an undershoot relative to the positive pulse in the read data signal;
transmitting the compensated data signal;
wherein the compensation of the read data signal by the gamma amplifier further depends at least in part on an amplitude of a negative pulse in the read data signal and an amplitude of an overshoot relative to the negative pulse in the read data signal; and
wherein the compensation of the read data signal by the gamma amplifier further depends at least in part on the width of a wave form in a pulse in the read data signal.
4. An apparatus for at least reducing an affect of non-linear asymmetry in a read data signal of a magnetic recording device, the apparatus comprising;
means for receiving a read data signal;
means for processing the read data signal into a compensated data signal in an non-linear asymmetry compensator of the magnetic recording device, the asymmetry compensator comprising a gamma amplifier whose compensation of the read data signal depends at least in part on an amplitude of a positive pulse in the read data signal and an amplitude of an undershoot relative to the positive pulse in the read data signal;
means for transmitting the compensated data signal;
wherein the compensation of the read data signal by the gamma amplifier further depends at least in part on an amplitude of a negative pulse in the read data signal and an amplitude of an overshoot relative to the negative pulse in the read data signal; and
wherein the compensation of the read data signal by the gamma amplifier further depends at least in part on the width of a wave form in a pulse in the read data signal.
5. A magnetic recording device comprising:
a read head for reading magnetic fluxes on a magnetic media, the read head having an output from which is transmitted a read data signal;
an asymmetry compensator for at least reducing an affect of non-linear asymmetry in the read data signal, the asymmetry compensator having an input coupled to the output of the read head, the asymmetry compensator comprising a gamma amplifier whose compensation of the read data signal depends at least in part on an amplitude of a positive pulse in the read data signal and an amplitude of an undershoot relative to the positive pulse in the read data signal, and the asymmetry compensator having an output from which is transmitted a compensated data signal;
a data decoder for reading encoded data from the compensated data signal, the data decoder having an input coupled to the output of the asymmetry compensator; and
an analog-to-digital (A/D) converter for converting analog data to digital data;
wherein the compensation of the read data signal by the gamma amplifier further depends at least in part on an amplitude of a negative pulse in the read data signal and an amplitude of an overshoot relative to the negative pulse in the read data signal; and
wherein the compensation of the read data signal by the gamma amplifier depends at least in part on the following equations:
γ
=
-
X
p
′
-
X
n
′
(
X
p
′
)
2
+
(
X
n
′
)
2
,
where γ is a variable representing the amount of compensation,
X p ′=X p + K p ·S p
and
X n ′=X n + K n ·S n , X p
is the amplitude of a positive pulse in the read data signal, S p is the amplitude of an undershoot for the positive pulse, K p is a multiplier for the positive pulse, X n is the amplitude of a negative pulse in the read data signal, S n is the amplitude of an overshoot for the negative pulse, and K n is a multiplier for the negative pulse.
6. A method for at least reducing an affect of non-linear asymmetry in a read data signal of a magnetic recording device, the method comprising:
receiving a read data signal;
processing the read data signal into a compensated data signal in a non-linear asymmetry compensator of the magnetic recording device, the asymmetry compensator comprising a gamma amplifier whose compensation of the read data, signal depends at least in part on an amplitude of a positive pulse in the read data signal and an amplitude of an undershoot relative to the positive pulse in the read data signal;
transmitting the compensated data signal;
wherein the compensation of the read data signal by the gamma amplifier further depends at least in part on an amplitude of a negative pulse in the read data signal and an amplitude of an overshoot relative to the negative pulse in the read data signal; and
wherein the compensation of the read data signal by the gamma amplifier depends at least in part on the following equations:
γ
=
-
X
p
′
-
X
n
′
(
X
p
′
)
2
+
(
X
n
′
)
2
,
where γ is a variable representing the amount of compensation, X p ′=X p + K p ·S p and X n ′=X n + K p ·S n , X p is the amplitude of a positive pulse in the read data signal, S p is the amplitude of an undershoot for the positive pulse, K p is a multiplier for the positive pulse, X n is the amplitude of a negative pulse in the read data signal, S n is the amplitude of an overshoot for the negative pulse, and K n is a multiplier for the negative pulse.
7. The An apparatus for at least reducing an affect of non-linear asymmetry in a read data signal of a magnetic recording device, the apparatus comprising:
means for receiving a read data signal;
means for processing the read data signal into a compensated data signal in an non-linear asymmetry compensator of the magnetic recording device, the asymmetry compensator comprising a gamma amplifier whose compensation of the read data signal depends at least in part on an amplitude of a positive pulse in the read data signal and an amplitude of an undershoot relative to the positive pulse in the read data signal;
means for transmitting the compensated data signal;
wherein the compensation of the read data signal by the gamma amplifier further depends at least in part on an amplitude of a negative pulse in the read data signal and an amplitude of an overshoot relative to the negative pulse in the read data signal; and
wherein the compensation of the read data signal by the gamma amplifier depends at least in part on the following equations:
γ
=
-
X
p
′
-
X
n
′
(
X
p
′
)
2
+
(
X
n
′
)
2
,
where γ is a variable representing the amount of compensation, X p ′=X p + K p ·S p and X n ′=X n + K p ·S n , X p is the amplitude of a positive pulse in the read data signal, S p is the amplitude of an undershoot for the positive pulse, K p is a multiplier for the positive pulse, X n is the amplitude of a negative pulse in the read data signal, S n is the amplitude of an overshoot for the negative pulse, and K n is a multiplier for the negative pulse.