Two-dimensional magnetic recording reader offset estimation
A method for enhancing read performance in a multi-reader two-dimensional magnetic recording system comprising first and second readers includes: receiving first and second analog read signals from the first and second readers, respectively; sampling the first and second analog read signals to generate first and second sampled signals, respectively, each of the first and second sampled signals comprising an integer component, indicative of a value of a corresponding one of the first and second analog read signals, respectively, at an integer multiple of a corresponding sampling period associated therewith, and/or a fractional component, indicative of a value of the corresponding one of the first and second analog read signals, respectively, at an arbitrary point in time between integer multiples of the corresponding sampling period; and combining the integer and/or fractional components of the respective first and second sampled signals to thereby generate a reader offset estimation signal.
1. A method for enhancing read performance in a multi-reader two-dimensional magnetic recording system including at least first and second readers, the method comprising:
receiving a first analog read signal from the first reader and a second analog read signal from the second reader;
sampling the first and second analog read signals to generate first and second sampled signals, respectively, each of the first and second sampled signals comprising at least one of an integer component, indicative of a value of a corresponding one of the first and second analog read signals, respectively, at an integer multiple of a corresponding sampling period associated therewith, and a fractional component, indicative of a value of a corresponding one of the first and second analog read signals, respectively, at an arbitrary point in time between integer multiples of the corresponding sampling period;
wherein sampling each of the first and second input signals includes:
converting at least the first analog read signal to a first digital signal having a first sampling period associated therewith;
interpolating the first digital signal using an interpolation filter, the interpolation filter receiving, at a first input, sequential phase inputs, and receiving, at a second input, a readback signal from the first reader, the interpolation filter being operative to generate a plurality of interpolation signals, each of the interpolation signals being generated during a given interpolation period as a function of a corresponding one of the phase inputs used during the given interpolation period; and
combining at least one of the integer and fractional components of the respective first and second sampled signals to thereby generate a reader offset estimation signal for enhancing read performance in the multi-reader two-dimensional magnetic recording system.
2. The method of claim 1 , wherein each of the first and second sampled signals comprises the integer component and the fractional component, and wherein the step of combining comprises combining the integer and fractional components of the respective first and second sampled signals to thereby increase an accuracy of the reader offset estimation signal.
3. The method of claim 1 , wherein interpolating the first digital signal is performed in parallel for a plurality of phase values to which the first analog read signal is to be interpolated.
4. The method of claim 1 , wherein the steps of sampling and combining comprise:
correlating a first readback signal from the first reader and a second readback signal from the second reader and generating a correlated signal as a function of the first and second readback signals; and
iteratively performing fractional delay filtering on the correlated signal, a number of iterations of the fractional delaying filtering corresponding to a number of phase values used in the fractional delay filtering.
5. The method of claim 1 , further comprising delaying the second sampled signal, an amount of delay being controlled as a function of the reader offset estimation signal.
6. The method of claim 1 , wherein the step of combining comprises selecting a signal path having a largest correlation peak value among a plurality of phase values to which the first analog read signal is to be interpolated.
7. A reader offset estimation apparatus for enhancing read performance in a multi-reader two-dimensional magnetic recording system including at least first and second readers, the reader offset estimation apparatus comprising:
at least one interpolation filter, the at least one interpolation filter receiving a first digital signal indicative of a first analog read signal from the first reader and a second digital signal indicative of a second analog read signal from the second reader, each of the first and second digital signals being indicative of a value of the first and second analog read signals, respectively, at an integer multiple of a corresponding sampling period associated therewith, the at least one interpolation filter being operative to generate first and second interpolated signals, each of the first and second interpolated signals being indicative of a value of the first and second digital signals, respectively, at an arbitrary point in time between integer multiples of the corresponding sampling period; and
at least one correlator coupled with the at least one interpolation filter, the at least one correlator being operative to combine at least one of the first and second interpolated signals and the first and second digital signals to thereby generate a reader offset estimation signal for enhancing read performance in the multi-reader two-dimensional magnetic recording system.
8. The apparatus of claim 7 , wherein the at least one interpolation filter comprises a fractional delay filter.
9. The apparatus of claim 8 , wherein the fractional delay filter is operative to sequentially interpolate the first analog read signal for a plurality of phase values to which the first analog signal is to be interpolated to thereby generate a plurality of corresponding fractional components, each of the fractional components being generated during a given interpolation period as a function of a corresponding one of the phase values used during the given interpolation period.
10. The apparatus of claim 9 , further comprising a buffer operative to store at least a subset of the plurality of fractional components generated by the fractional delay filter.
11. The apparatus of claim 7 , wherein the at least one interpolation filter comprises a plurality of interpolation filters, each of the interpolation filters receiving, at a first input, a corresponding value of a phase to which the first analog read signal is to be interpolated, and receiving, at a second input, a readback signal from the first reader.
12. The apparatus of claim 11 , wherein the at least one correlator comprises a plurality of correlators, each of the plurality of correlators being coupled with a corresponding one of the plurality of interpolation filters, each of the plurality of correlators receiving, at a first input, an interpolation signal generated by the corresponding one of the interpolation filters, and receiving, at a second input, a readback signal from the second reader.
13. The apparatus of claim 7 , wherein the at least one correlation filter is operative to correlate a first readback signal from the first reader and a second readback signal from the second reader and to generate a correlated signal as a function of the first and second readback signals, and wherein the at least one correlator is operative to iteratively perform fractional delay filtering on the correlated signal, a number of iterations of the fractional delaying filtering corresponding to a number of phase values used in the fractional delay filtering.
14. The apparatus of claim 7 , further comprising first and second analog-to-digital converters, the first analog-to-digital converter being operative to receive the first analog read signal and to generate the first digital signal, the second analog-to-digital converter being operative to receive the second analog read signal and to generate the second digital signal.
15. The apparatus of claim 7 , further comprising a delay compensation module coupled in a signal path of the second reader, the delay compensation module being operative to receive the second digital signal and to generate a delayed version of the second digital signal, an amount of delay added to the second digital signal by the delay compensation module being controlled as a function of the reader offset estimation signal.
16. A method for enhancing read performance in a multi-reader two-dimensional magnetic recording system including at least first and second readers, the method comprising:
receiving a first analog read signal from the first reader and a second analog read signal from the second reader;
sampling the first and second analog read signals to generate first and second sampled signals, respectively, each of the first and second sampled signals comprising at least one of an integer component, indicative of a value of a corresponding one of the first and second analog read signals, respectively, at an integer multiple of a corresponding sampling period associated therewith, and a fractional component, indicative of a value of a corresponding one of the first and second analog read signals, respectively, at an arbitrary point in time between integer multiples of the corresponding sampling period;
wherein interpolating the first digital signal is performed sequentially for a plurality of phase values to which the first analog read signal is to be interpolated to thereby generate a plurality of corresponding fractional components, each of the fractional components being generated during a given interpolation period as a function of a corresponding one of the phase values used during the given interpolation period; and
combining at least one of the integer and fractional components of the respective first and second sampled signals to thereby generate a reader offset estimation signal for enhancing read performance in the multi-reader two-dimensional magnetic recording system.
17. The method of claim 16 , further comprising storing at least a subset of the plurality of fractional components generated by the interpolating step.
18. A method for enhancing read performance in a multi-reader two-dimensional magnetic recording system including at least first and second readers, the method comprising:
receiving a first analog read signal from the first reader and a second analog read signal from the second reader;
sampling the first and second analog read signals to generate first and second sampled signals, respectively, wherein sampling each of the first and second input signals includes:
converting at least the first analog read signal to a first digital signal having a first sampling period associated therewith;
interpolating the first digital signal using a plurality of interpolation filters, wherein each of the interpolation filters receiving, at a first input, a corresponding value of a phase to which the first analog read signal is to be interpolated, and receiving, at a second input, a readback signal from the first reader, and wherein interpolating the first digital signal yields the fractional component indicative of the value of the first analog read signal at an arbitrary point in time between integer multiples of the first sampling period;
wherein each of the first and second sampled signals comprising at least one of an integer component, indicative of a value of a corresponding one of the first and second analog read signals, respectively, at an integer multiple of a corresponding sampling period associated therewith, and a fractional component, indicative of a value of a corresponding one of the first and second analog read signals, respectively, at an arbitrary point in time between integer multiples of the corresponding sampling period; and
combining at least one of the integer and fractional components of the respective first and second sampled signals to thereby generate a reader offset estimation signal for enhancing read performance in the multi-reader two-dimensional magnetic recording system.
19. The method of claim 18 , wherein combining the at least one of the integer and fractional components of the respective first and second sampled signals includes providing a plurality of correlators, each of the plurality of correlators being coupled with a corresponding one of the plurality of interpolation filters, each of the plurality of correlators receiving, at a first input, an interpolation signal generated by the corresponding one of the interpolation filters, and receiving, at a second input, a readback signal from the second reader.
20. A method for enhancing read performance in a multi-reader two-dimensional magnetic recording system including at least first and second readers, the method comprising:
receiving a first analog read signal from the first reader and a second analog read signal from the second reader;
sampling the first and second analog read signals to generate first and second sampled signals, respectively, each of the first and second sampled signals comprising at least one of an integer component, indicative of a value of a corresponding one of the first and second analog read signals, respectively, at an integer multiple of a corresponding sampling period associated therewith, and a fractional component, indicative of a value of a corresponding one of the first and second analog read signals, respectively, at an arbitrary point in time between integer multiples of the corresponding sampling period;
combining at least one of the integer and fractional components of the respective first and second sampled signals to thereby generate a reader offset estimation signal for enhancing read performance in the multi-reader two-dimensional magnetic recording system; and
wherein the steps of sampling and combining comprise: correlating a first readback signal from the first reader and a second readback signal from the second reader and generating a correlated signal as a function of the first and second readback signals; and iteratively performing fractional delay filtering on the correlated signal, a number of iterations of the fractional delaying filtering corresponding to a number of phase values used in the fractional delay filtering.
21. A method for enhancing read performance in a multi-reader two-dimensional magnetic recording system including at least first and second readers, the method comprising:
receiving a first analog read signal from the first reader and a second analog read signal from the second reader;
sampling the first and second analog read signals to generate first and second sampled signals, respectively, each of the first and second sampled signals comprising at least one of an integer component, indicative of a value of a corresponding one of the first and second analog read signals, respectively, at an integer multiple of a corresponding sampling period associated therewith, and a fractional component, indicative of a value of a corresponding one of the first and second analog read signals, respectively, at an arbitrary point in time between integer multiples of the corresponding sampling period;
combining at least one of the integer and fractional components of the respective first and second sampled signals to thereby generate a reader offset estimation signal for enhancing read performance in the multi-reader two-dimensional magnetic recording system; and
delaying the second sampled signal, an amount of delay being controlled as a function of the reader offset estimation signal.
22. A method for enhancing read performance in a multi-reader two-dimensional magnetic recording system including at least first and second readers, the method comprising:
receiving a first analog read signal from the first reader and a second analog read signal from the second reader;
sampling the first and second analog read signals to generate first and second sampled signals, respectively, each of the first and second sampled signals comprising at least one of an integer component, indicative of a value of a corresponding one of the first and second analog read signals, respectively, at an integer multiple of a corresponding sampling period associated therewith, and a fractional component, indicative of a value of a corresponding one of the first and second analog read signals, respectively, at an arbitrary point in time between integer multiples of the corresponding sampling period;
combining at least one of the integer and fractional components of the respective first and second sampled signals to thereby generate a reader offset estimation signal for enhancing read performance in the multi-reader two-dimensional magnetic recording system, wherein combining the at least one of the integer and fractional components of the respective first and second sampled signals includes selecting a signal path having a largest correlation peak value among a plurality of phase values to which the first analog read signal is to be interpolated.