Pulse or digital communications – Receivers – Particular pulse demodulator or detector
Reexamination Certificate
2001-01-11
2003-06-17
Ghayour, Mohammad H. (Department: 2631)
Pulse or digital communications
Receivers
Particular pulse demodulator or detector
C375S355000, C375S326000
Reexamination Certificate
active
06580770
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an information regenerating apparatus and an information regenerating method in which a regenerated clock is produced from input data, for example, read out from an optical disk such as digital video disk (DVD) to regenerate input data in synchronization with the regenerated clock.
2. Description of Related Art
FIG. 11
is a constitutional diagram showing a conventional information regenerating apparatus. In
FIG. 11
,
1
indicates an auto-gain controller (AGC) for adjusting an amplitude of input data (RF) read out from an optical disk.
2
indicates a waveform equalizer (EQ) for reshaping a waveform of the input data. The waveform equalizer
2
is composed of a filter for heightening a gain of an attenuated high-frequency signal component of the input data and a low pass filter for removing an unnecessary high-frequency noise of the input data.
3
indicates a slicer for expressing the input data in binary data to produce regenerated data (DATA). The slicer
3
has a comparator for determining the regenerated data to binary data of “0” and “1” according to a comparison between the input data and a reference electric potential.
4
indicates a phase comparator for comparing an edge of the regenerated data and a phase of a regenerated clock (CLK) and generating a pulse P or a pulse N according to a degree of a phase advance or a degree of a phase lag.
5
indicates a charge pump (C.P.) for charging a condenser
6
with electric current in response to the inputting of the pulse P to heighten an electric potential of the condenser
6
or discharging electric current from the condenser
6
in response to the inputting of the pulse N to lower an electric potential of the condenser
6
.
7
indicates a voltage control oscillator (VCO) which oscillates at a frequency corresponding to the electric potential of the condenser
6
to produce the regenerated clock.
Next, an operation is described.
In an information regenerating apparatus in which data is regenerated from input data read out from an optical disk, it is required to produce a clock which synchronizes with the regenerated data. Therefore, a method, in which a clock is regenerated by controlling a voltage control oscillator according to a phase difference between an edge of the regenerated data and the clock, is generally used.
In
FIG. 11
, in the auto-gain controller
1
, an amplitude of the input data read out from an optical disk is adjusted to a constant value. In the wave form equalizer
2
, a wave form of the input data, of which the amplitude is adjusted, is reshaped by heightening a gain of an attenuated high-frequency signal component of the input data and removing an unnecessary high-frequency noise of the input data. In the slicer
3
, the input data, of which the waveform is reshaped, is expressed in binary data of “0” and “1” according to a comparison between the input data and a reference electric potential, and regenerated data is produced.
Also, as to the regeneration of a clock, in the phase comparator
4
, an edge of the regenerated data is compared with a phase of a regenerated clock produced in the voltage control oscillator
7
, and a pulse P or a pulse N is generated according to a degree of a phase advance or a degree of a phase lag. In the charge pump
5
, the condenser
6
is charged with electric current in response to the inputting of the pulse P to heighten an electric potential of the condenser
6
, or electric current is discharged from the condenser
6
in response to the inputting of the pulse N to lower an electric potential of the condenser
6
. The voltage control oscillator
7
oscillates at a frequency corresponding to the electric potential of the condenser
6
and produces the regenerated clock which is synchronized with the regenerated data.
FIG. 12
is a timing chart showing an operation of the conventional information regenerating apparatus.
As shown in
FIG. 12
, in cases where a leading edge of the regenerated data (DATA) is earlier than a leading edge of the regenerated clock (CLK), that is, in cases where a phase of the regenerated clock is late, a pulse P is generated to heighten an electric potential (C) of the condenser
6
, and a frequency of the regenerated clock is heightened. In contrast, in cases where a leading edge of the regenerated data (DATA) is later than a leading edge of the regenerated clock (CLK), that is, in cases where a phase of the regenerated clock is advanced, a pulse N is generated to lower an electric potential (C) of the condenser
6
, and a frequency of the regenerated clock is lowered.
Because the conventional information regenerating apparatus has the above-described configuration, all constituent elements of the conventional information regenerating apparatus are made of analog circuits. However, in cases where a plurality of conventional information regenerating apparatuses are, for example, made of complementary metal oxide semiconductor large scale integrated circuits (CMOS-LSI), because characteristics of p-channel transistors and characteristics of n-channel transistors lack uniformity, the electric currents in the charge pumps
5
of the conventional information regenerating apparatuses lack uniformity and are set to various values. Therefore, a phase lock point of a phase synchronization loop is shifted from a value corresponding to an ideal state, and a clock regeneration characteristic becomes worse. That is, because characteristics of circuit elements of analog circuits lack uniformity, there is a problem that characteristics of the conventional information regenerating apparatuses lack uniformity.
SUMMARY OF THE INVENTION
An object of the present invention is to provide, with due consideration to the drawbacks of the conventional information regenerating apparatus, an information regenerating apparatus which is made of digital circuits, is operated at a uniform characteristic and has a high performance. Also, the object of the present invention is to provide an information regenerating method applied for the information regenerating apparatus.
The object is achieved by the provision of an information regenerating apparatus comprising an analog-to-digital converter for converting input data into digital data by performing a data-extraction for the input data in synchronization with a regenerated clock, a zero-cross detector for detecting a zero-cross of the digital data converted in the analog-to-digital converter according to the two pieces of digital data one after another converted in the analog-to-digital converter, a phase detector for detecting a phase shift quantity between a mid point of two data extracting points of two pieces of digital data, which are data-extracted in the analog-to-digital converter before and after the detection of the zero-cross of the digital data performed in the zero-cross detector, and a zero-cross point of the two pieces of digital data in cases where the zero-cross of the digital data is detected in the zero-cross detector, a frequency calculating unit for calculating target oscillation frequency data by adding up the plurality of phase shift quantities detected in the phase detector, a digital-to-analog converter for converting the target oscillation frequency data calculated in the frequency calculating unit into analog data, and a voltage control oscillator for generating the regenerated clock according to the analog data converted in the digital-to-analog converter and providing the regenerated clock for the analog-to-digital converter.
Because the zero-cross detector, the phase detector and the frequency calculating unit arranged between the analog-to-digital converter and the digital-to-analog converter can be made of digital circuits, the information regenerating apparatus does not receive an adverse influence in which characteristics of analog circuits lack uniformity, and the information regenerating apparatus, which is operated at a uniform characteristic and has a high performance, can be obtained.
Also, th
Imanaka Yoshifumi
Katoh Hisao
Al-Beshrawi Tony
Burns Doane , Swecker, Mathis LLP
Ghayour Mohammad H.
Mitsubishi Denki & Kabushiki Kaisha
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