Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Reexamination Certificate
1998-08-13
2001-04-03
Edun, Muhammad (Department: 2753)
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
C369S059160, C369S047360
Reexamination Certificate
active
06212144
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method of reading data on a recording medium, and more specifically to a method of reading data using a self-optimizing waveform equalizer.
As shown in
FIG. 1
, a head unit
12
reads data stored on a recording medium
11
, such as an optical disk, magneto-optical disk, or magnetic disk, and outputs a read signal RD having a voltage corresponding to the state of the data (“1” or “0”) to a data reader
13
.
The data reader
13
includes a prefilter
14
, an automatic gain control amplifier (AGC)
15
, an A/D converter (ADC)
16
, a waveform equalizer
17
, and a PLL circuit
18
. The prefilter
14
filters the read signal RD to output a signal having a desired frequency to the AGC
15
. The AGC
15
amplifies the output signal from the prefilter
14
to output a signal having a predetermined amplitude. The ADC
16
converts the output signal from the AGC
15
into a digital signal and outputs the digital signal to the waveform equalizer
17
.
The waveform equalizer
17
executes waveform shaping of the digital signal by means of an intensity (sensitivity) parameter set in advance, and outputs the waveform-shaped digital signal to a CPU
19
and PLL circuit
18
as a reproduced signal Dout. The CPU
19
generates read-out data consisting of a predetermined number of bits on the basis of the reproduced signal Dout from the waveform equalizer
17
. The waveform equalizer
17
includes coefficients used during the waveform shaping.
The PLL
18
generates a clock signal CLK synchronized with the reproduced signal Dout and delivers the clock signal CLK to the ADC
16
and the waveform equalizer
17
. The clock signal CLK is used in setting the timing for taking in the data “1” or “0”. That is, the ADC
16
samples the signal from the AGC
15
synchronously with the input clock signal CLK, converts the sampled signal into a digital signal, and outputs the digital signal. The waveform equalizer
17
executes an operation synchronously with the input clock signal CLK. The PLL
18
possesses coefficients for synchronizing the clock signal CLK with the read signal RD.
As shown in
FIG. 2
, a sector of the recording medium
11
includes a preamble (PR) region
21
, a training (TR) region
22
, a sink byte (SB) region
23
, and a data region
24
.
The PR region
21
contains a preamble (PR) code used to synchronize the clock signal CLK from the PLL circuit
18
with the read signal RD. The bits of the PR code may all be “1”, for example, and the read signal RD of the PR code may be a sine wave.
The TR region
22
contains a training (TR) code used to optimize the performance of the waveform equalizer
17
. The TR code is bit data, for example, “001100111”, and contains high frequency components and low frequency components as an analog signal.
The SB region
23
contains a sink byte (SB) code used to detect the start of the data region
24
. The CPU
19
treats bit data following the SB code as record data and performs a process to the record data.
The PLL circuit
18
synchronizes the clock signal CLK with the read signal RD using the output signal from the waveform equalizer
17
. The waveform equalizer
17
optimizes its coefficients, even when the PLL circuit
18
is in operation. When the output signal Dout input to the PLL circuit
18
varies, the PLL circuit
18
alters the frequency of the clock signal CLK. At this time, there is a possibility that the PLL circuit
18
cannot converge the coefficients while the PR code is being read. That is, the PLL circuit
18
may not be able to synchronize the clock signal CLK with the read signal RD. Also, the waveform equalizer
17
may not be able to optimize its coefficients by some chance, while the TR code is being read out. This makes it difficult to read data from the recording medium
11
or increase the read-out time. Such problem have been an obstacle preventing increasing the speed of data processing, the recording density of the recording medium
11
, and the rotation speed (high speed read-out) of the recording medium.
It is therefore an object of the present invention to provide an improved method of reading data stored on a recording medium.
SUMMARY OF THE INVENTION
To achieve the above objective, the present invention provides a data reading apparatus for reading data recorded on a recording medium, the data reading apparatus comprising: an A/D converter that receives a read signal and a clock signal, the read signal including the recorded data and a control data for controlling a read out operation of the recorded data, and converts the read signal into a digital signal synchronously with the clock signal; and a waveform equalizer having a coefficient relate to a waveform of the digital signal and an intensity parameter, wherein the waveform equalizer receives the digital signal and the clock signal, optimizes the coefficient synchronously with the clock signal by an operation employing the intensity parameter and the digital signal, and shapes the waveform of the digital signal in accordance with the optimized coefficient to generate a reproduced signal, wherein: the intensity parameter has a predetermined initial value, the waveform equalizer includes a control unit for adjusting a value of the intensity parameter, and the control unit sets the value of the intensity parameter to a value larger than the initial value when the waveform equalizer optimizes the coefficient.
The present invention further provides a data reading apparatus for reading data recorded on a recording medium, the data reading apparatus comprising: an A/D converter that receives a read signal and a clock signal, the read signal including the recorded data and control data for controlling a read out operation of the recorded data, and converts the read signal synchronously with the clock signal into a digital signal; a waveform equalizer for shaping a waveform of the digital signal and generating a reproduced signal; and a PLL circuit for generating the clock signal synchronized with the reproduced signal using an intensity parameter, wherein: the intensity parameter has an initial value, the PLL circuit includes a control unit for adjusting a value of the intensity parameter, and the control unit adjusts the value of the intensity parameter to a value larger than a predetermined value when the PLL circuit generates the clock signal synchronized with the reproduced signal.
The present invention provides a data reading apparatus for reading data recorded on a recording medium, the data reading apparatus comprising: an A/D converter that receives a read signal and a clock signal, the read signal including the recorded data and control data for controlling a read out operation of the recorded data, and converts the read signal to a digital signal synchronously with the clock signal; a waveform equalizer having a coefficient in relation to a waveform shaping of the digital signal and a first intensity parameter, receives the digital signal and the clock signal, optimizes the coefficient synchronously with the clock signal using the first intensity parameter and the digital signal, and performs waveform shaping of the digital signal in accordance with the optimized coefficient and the first intensity parameter to generate a reproduced signal, wherein the intensity parameter has an initial value; a first control unit for adjusting the first intensity parameter; a PLL circuit having a second intensity parameter relating to a synchronization of the clock signal for receiving the reproduced signal and for generating the clock signal synchronized with the reproduced signal based on the second intensity parameter, wherein the second intensity parameter has an initial value; and a second control unit for adjusting a value of the second intensity parameter; wherein the second control unit sets the second intensity parameter to a value larger than its value at the moment the clock signal is generated, and the first control unit sets the first intensity parameter to a value that is smaller than a predeterm
Edun Muhammad
Fujitsu Limited
Greer Burns & Crain Ltd.
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