Method and apparatus for using dual-viterbi algorithms to estimate data stored in a storage medium

• US 8,873,614 B1
• Filed: 11/25/2013
• Issued: 10/28/2014
• Est. Priority Date: 05/01/2006
• Status: Active Grant

• Current Assignee: Marvell Asia Pte Limited (Marvell Technology Group Limited)
• Original Assignee: Marvell International Limited (Marvell Technology Group Limited)
• Inventors: Song, Hongwei, Wu, Zining, Yang, Shaohua
• Primary Examiner(s): Ghulamali, Qutbuddin
• Application Number:
  US14/088,777
• Time in Patent Office: 337 Days
• Field of Search: 375/232, 375/265, 375/229, 375/341, 375/256, 375/234
• US Class Current: 375/232
• CPC Class Codes: G11B 20/1803 by redundancy in data representation
• CPC Class Codes: H03M 13/3746 with iterative decoding
• CPC Class Codes: H03M 13/41 using the Viterbi algorithm or Viterbi processors
• CPC Class Codes: H03M 13/6343 Error control coding in combination with techniques for partial response channels, e.g. recording
• CPC Class Codes: H04L 1/0054 Maximum-likelihood or sequential decoding, e.g. Viterbi, Fano, ZJ algorithms

Abstract

A system including a storage medium, a demodulator, and a decoder. The demodulator is configured to receive an input signal from the storage medium and demodulate the input signal. The decoder is configured to estimate data stored in the storage medium by decoding the demodulated input signal to provide an output signal. The decoder includes a filter and first and second processors. The filter is configured to generate a first equalized signal based on the output signal. The first processor is configured to, based on the first equalized signal and a first Viterbi algorithm, generate a first estimate of the data and an estimate of noise. The second processor is configured to generate a second estimate of the data based on the first estimate of the data, the estimate of the noise, and a second Viterbi algorithm. The output signal includes the second estimate of the data.

Claims

1. A system comprising:

a storage medium;

a demodulator configured to (i) receive an input signal from the storage medium, and (ii) demodulate the input signal; and

a channel decoder configured to estimate data stored in the storage medium by decoding the demodulated input signal to provide an output signal, wherein the channel decoder comprises

a first filter configured to generate a first equalized signal based on the output signal provided by the channel decoder,

a first processor configured to, based on the first equalized signal and a first Viterbi algorithm, generate (i) a first estimate of the data, and (ii) an estimate of noise, and

a second processor configured to generate a second estimate of the data based on (i) the first estimate of the data, (ii) the estimate of the noise, and (iii) a second Viterbi algorithm, and

wherein the output signal comprises the second estimate of the data.

2. The system of claim 1, wherein the first estimate of the data and the second estimate of the data are non-return-to-zero estimates such that neither of the first estimate of the data and the second estimate of the data correspond to a zero voltage state.

3. The system of claim 1, wherein:

the channel decoder further comprises a second filter configured to generate a filtered signal based on the first estimate of the data; and

the second processor is further configured to generate the output signal based on a sum of (i) a delayed version of the first equalized signal, and (ii) the filtered signal.

4. The system of claim 3, wherein the channel decoder further comprises:

a plurality of filters configured to generate respective filtered signals based on the filtered signal generated by the second filter; and

a summer configured to sum the filtered signals generated by the plurality of filters,

wherein the second processor is further configured to generate the second estimate of the data based on an output of the summer.

5. The system of claim 1, wherein the first processor is further configured to:

generate a third estimate of the data based on the first equalized signal;

generate a first estimate signal, wherein the first estimate signal includes the first estimate of the data; and

generate a second estimate signal, wherein the second estimate signal includes the third estimate of the data and has a shorter associated depth than the first estimate signal.

6. The system of claim 5, further comprising a first summer configured to generate an error signal based on the second estimate signal.

7. The system of claim 6, wherein the channel decoder comprises:

a first delay device configured to delay the first equalized signal, wherein the first summer is configured to generate the error signal based on the delayed first equalized signal;

a second delay device configured to delay an output of the first delay device;

a second summer configured to generate an output based on the (i) first estimate of the data, and (ii) an output of the second delay device; and

a third delay device configured to delay the output of the second delay device,

wherein the second processor is configured to generate the second estimate of the data based on (i) the output of the second summer, and (ii) an output of the third delay device.

8. The system of claim 1, further comprising:

an amplifier configured to amplify the input signal received from the storage medium;

a first summer configured to sum the amplified input signal and a first analog signal to generate a second analog signal;

an analog-to-digital converter configured to convert the second analog signal to a digital signal,

wherein the first filter is configured to generate the first equalized signal based on the digital signal; and

a second summer configured to generate a second equalized signal based on the first equalized signal.

9. The system of claim 8, further comprising:

a third summer configured to generate an error signal based on a third estimate of the data;

wherein the first processor is configured to generate the third estimate of the data based on the second equalized signal, and

wherein the amplifier is configured to, based on the error signal, amplify the input signal received from the storage medium; and

a baseline loop configured to (i) track a direct current of the channel decoder, (ii) generate a first baseline signal based on the error signal, and (iii) generate the first analog signal based on the first baseline signal.

10. The system of claim 9, further comprising:

a baseline device configured to generate a second baseline signal based on the error signal; and

a fourth summer configured to generate an output based on (i) the error signal, and (ii) the second baseline signal.

11. A method comprising:

receiving an input signal from a storage medium;

demodulating the input signal; and

estimating data stored in the storage medium by decoding the demodulated input signal to provide an output signal,

wherein the decoding of the demodulated input signal comprises

generating, via a first filter, a first equalized signal based on the output signal,

based on the first equalized signal and a first Viterbi algorithm, generating (i) a first estimate of the data, and (ii) an estimate of noise, and

generating a second estimate of the data based on (i) the first estimate of the data, (ii) the estimate of the noise, and (iii) a second Viterbi algorithm, and

wherein the output signal comprises the second estimate of the data.

12. The method of claim 11, wherein the first estimate of the data and the second estimate of the data are non-return-to-zero estimates such that neither of the first estimate of the data and the second estimate of the data correspond to a zero voltage state.

13. The method of claim 11, wherein the decoding of the demodulated input signal further comprises:

generating, via a second filter, a filtered signal based on the first estimate of the data; and

generating the output signal based on a sum of (i) a delayed version of the first equalized signal, and (ii) the filtered signal.

14. The method of claim 13, wherein the decoding of the demodulated input signal further comprises:

generating respective filtered signals, via a plurality of filters, based on the filtered signal generated by the second filter; and

via a summer, summing the filtered signals generated by the plurality of filters,

wherein the second estimate of the data is generated based on an output of the summer.

15. The method of claim 11, wherein the decoding of the demodulated input signal further comprises:

generating a third estimate of the data based on the first equalized signal;

generating a first estimate signal, wherein the first estimate signal includes the first estimate of the data; and

generating a second estimate signal, wherein the second estimate signal includes the third estimate of the data and has a shorter associated depth than the first estimate signal.

16. The method of claim 15, further comprising generating, via a first summer, an error signal based on the second estimate signal.

17. The method of claim 16, wherein the decoding of the demodulated input signal further comprises:

delaying the first equalized signal via a first delay device,

wherein the error signal is generated based on the delayed first equalized signal;

delaying an output of the first delay device via a second delay device;

generating, via a second summer, an output based on the (i) first estimate of the data, and (ii) an output of the second delay device; and

delaying the output of the second delay device via a third delay device,

wherein generating the second estimate of the data is generated based on (i) the output of the second summer, and (ii) an output of the third delay device.

18. The method of claim 11, further comprising:

amplifying the input signal received from the storage medium;

summing the amplified input signal and a first analog signal to generate a second analog signal;

converting the second analog signal to a digital signal;

generating the first equalized signal based on the digital signal; and

generating a second equalized signal based on the first equalized signal.

19. The method of claim 18, further comprising:

generating an error signal based on a third estimate of the data;

generating the third estimate of the data based on the second equalized signal;

based on the error signal, amplifying the input signal received from the storage medium; and

via a baseline loop,

tracking a direct current of a channel decoder,

generating a first baseline signal based on the error signal, and

generating the first analog signal based on the first baseline signal.

20. The method of claim 19, further comprising:

generating a second baseline signal based on the error signal; and

generating an output based on (i) the error signal, and (ii) the second baseline signal.