Pulse or digital communications – Equalizers – Automatic
Reexamination Certificate
1999-04-06
2002-01-01
Vo, Don N. (Department: 2631)
Pulse or digital communications
Equalizers
Automatic
C375S350000, C375S354000
Reexamination Certificate
active
06335949
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a non-linear signal receiver, and more particularly, to a non-linear signal receiver for stably restoring the sampling time of a signal reproduced from a data storage device, taking in consideration non-linear distortion of the signal.
2. Description of the Related Art
In general, non-linearity becomes a serious problem as recording density increases in digital magnetic recording media such as a hard disk drive (HDD). Non-linearity is generated due to interactions between adjacent transitions. A demagnetization field of a previously recorded transition shifts the position of a subsequently recorded transition and increases the width between transitions. The adjacent transitions operate to erase each other. As a result, the amplitude of a reproduced signal is reduced. Such phenomenons are known as a non-linear transition shift (NLTS), a transition broadening, and a partial erasure. Such non-linear distortion adversely affects a series of processes for detecting data from the reproduced signal, and makes it difficult to search an accurate phase of the signal. In case that such non-linear distortion characteristic is not considered, timing jitter and bias become serious.
To solve the problems, U.S. Pat. No. 4,890,299 discloses a method for correcting the sampling phase of a partial-response (PR) signal without causing hangups in which the sampling phase correction is interrupted for a predetermined period of time. However, the method is effective on only linear signals. That is, it is difficult to apply this method to a signal having non-linear distortion. Also, other conventional methods for phase compensation have been based on the assumption that a signal is linear. Thus, these methods cannot be used for a signal having serious non-linear distortion.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a non-linear signal receiver for modeling signals sampled in consideration of past, current and future bit data, and correcting sampling-timing phase from the phase gradient among the sampled signals.
To achieve the object of the present invention, there is provided a non-linear signal receiver for detecting an original data a
k
from an input signal r(t) which is a binary data stream input through a channel or reproduced from data recorded on a storing device, the receiver comprising: an analog-to-digital converter (ADC) for sampling the input value according to sampling timing phases, and converting the sampled data into a digital signal r
k
; a modeling portion including 2N+1 taps P
n
(n=−N, . . . , 0, . . . , N) each for selecting one of 2
&tgr;+&ngr;
tap values according to each pattern p
n
(b
k−n+&ngr;:k−n+l
, b
k−n−1:k−n−&tgr;
) of absolute values of the data transitions future &ngr; bits and past &tgr; bits, for estimating the channel characteristics of the sampled signal from the selected tap value and the data transition value; a timing recovery portion for controlling the sampling timing phase of the analog-to-digital converter using a phase gradient which is the difference between values of respective taps positioned symmetrically around the tap P
0
of the modeling portion; an equalizer for compensating for the deteriorated characteristics of the output value of the analog-to-digital converter; and a detector for converting the output of the equalizer to a digital value, to detect the original signal.
REFERENCES:
patent: 3651316 (1972-03-01), Gibson
patent: 3697689 (1972-10-01), Gibson
patent: 5230012 (1993-07-01), Schenk
patent: 5606464 (1997-02-01), Agazzi et al.
patent: 6252733 (2001-06-01), Staszewski
patent: 6266350 (2001-07-01), Ojard et al.
patent: 0618574 (1994-10-01), None
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