Dynamic information storage or retrieval – Binary pulse train information signal – Binary signal gain processing
Reexamination Certificate
1998-11-06
2001-02-20
Huber, Paul W. (Department: 2753)
Dynamic information storage or retrieval
Binary pulse train information signal
Binary signal gain processing
C369S047360
Reexamination Certificate
active
06192016
ABSTRACT:
BACKGROUND OF THE INVENTION
In a contemporary compact disk (CD) system, a photodiode senses light transmitted to a disk by an optical pickup and converts the sensed, reflected optical signal into an analog RF signal. The analog RF signal output of the photodiode is provided to a data slice unit, where asymmetry in the signal is corrected. The asymmetry-corrected signal is provided to a peak detector, where it is converted into a rectangular signal on the basis of a predetermined bias level. An edge detector detects edges in the rectangular signal, and outputs pulses generated at the detected edges to an eight-to-fourteen demodulator (EFDM). The EFDM receives, in units of 14 bits, the pulse train generated at the detected edges, converts each 14-bit signal into an 8-bit signal, and outputs the converted 8-bit signal to an error corrector.
With ever-increasing optical disk recording density, digital video disk (DVD) systems have recently appeared. A DVD system recovers data from an analog RF signal for the EFDM, in a manner similar to the aforementioned CD system. However, data recorded at such high density must be recovered digitally, to minimize data loss, since analog recovery is unsuitable for adaptive recovery of data for the EFDM, due to variances in the type of optical disk and differences in manufacturing processes. Additionally, with an increase in demand for high-speed transmission and high density recording, when data is recovered according to the analog technique, data quality is adversely affected due to interference between signals.
SUMMARY OF THE INVENTION
To address the aforementioned problems, the present invention is directed to a data recovery apparatus in an optical disk reproduction system, for digital recovery of data for an EFDM from an analog radio-frequency (RF) signal. The present invention further relates to a data recovery method for such a system.
It is therefore an object of the present invention to provide a data recovery apparatus and method for an optical disk reproduction system, adapted to digitally recover data from an analog RF signal to be provided to an EFDM.
The apparatus of the present invention is directed to a data recovery system in an optical disk reproduction system including a photodiode and an eight to fourteen demodulator (EFDM) for converting the pattern of a bit train, the data recovery system comprising: an analog-to-digital converter for converting an analog radio frequency (RF) signal input from the photodiode into a digital signal in response to a reference clock signal, and outputting the converted signal as a digital RF signal; a first adder for adding an asymmetry error amount of the digital RF signal to the digital RF signal; an adaptive digital equalizer for digitally controlling the level of the result added by the first adder, in response to a control signal; a digital level detector for calculating the asymmetry error amount using the result added by the first adder, and outputting the control signal according to the output of the adaptive digital equalizer and predetermined coefficients; a viterbi decoder for viterbi-decoding the output of the adaptive digital equalizer into the bit train and outputting the decoded bit train to the EFDM; a digital edge detector for calculating accuracy of sampling by the analog-to-digital converter, using the result added by the first adder, and outputting phase and frequency control signals according to the calculated accuracy; and a reference signal generator for outputting the reference clock signal having a frequency which varies in response to the phase and frequency control signals.
The method of the present invention is directed to a data recovery method operable in an optical disk reproduction system including a photodiode for outputting an analog RF signal and an eight to fourteen demodulator (EFDM) for converting the pattern of a bit train, the method comprising the steps of: (a) obtaining a digital RF signal by converting the analog RF signal into a digital signal by sampling corresponding to a reference clock signal; (b) determining whether an asymmetry error exists, using the digital RF signal; (c) correcting the asymmetry error with including the asymmetry error amount in the digital RF signal, if the asymmetry error exists, and returning to the step (b); (d) determining whether sampling was performed accurately, if no asymmetry error exists; (e) obtaining frequency and phase errors using the digital RF signal in which the asymmetry error was corrected, if the sampling was not accurately performed; (f) oscillating a frequency according to the frequency and phase errors, obtaining the reference clock signal having an oscillated frequency, and proceeding to the step (d); (g) digitally adjusting a quantized level of the digital RF signal whose asymmetry error was corrected and which was converted by accurate sampling, using the reference clock signal, if the sampling was performed accurately; (h) determining whether a quantized level arbitrarily extracted within a positive or negative 3T section is an estimated quantized level corresponding to the 3T, where T is the period of the reference clock signal, and proceeding to the step (g); and (i) obtaining the bit train by viterbi-decoding the digital RF signal having the adjust quantized level, if the quantized level is not the same as the estimated quantized level.
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Nakajima et al., “Astudy of PRML systems for a phase change optical disk,” Technical Report of IEICE, pp. 45-50, Dec. 1995.
Uehara, “Paralleism in Analog and Digital PRML Magnetic Disk Read Channel Equalizers,” IEEE Transactions on Magnetics, vol. 31; No. 2, pp. 1174-1179, Mar. 1995.
Woods, “Comparison and Optimization of Digital Read Channels Using Actual Data,” IEEE, pp. 1474-1478 (1993).
Wood et al., “Viterbi Detection of Class IV Partial Response on a Magnetic Recording Channel,” IEEE Transactions on Communications, vol. Com-34; No. 5, pp. 454-461, May 1986.
Huber Paul W.
Samsung Electronics Co,. Ltd
Samuels , Gauthier & Stevens, LLP
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