Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Reexamination Certificate
1998-04-28
2001-09-18
Psitos, Aristotelis M. (Department: 2651)
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
C369S059230, C360S125330
Reexamination Certificate
active
06292450
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a digital video (or versatile) disk reproducing apparatus, and in particular, to a method of automatically controlling a bandwidth of a waveform equalizer to minimize a data error rate during pulse detection.
2. Description of the Related Art
A digital video (or versatile) disc (hereinafter referred to as a DVD), which is a recording medium for a digital moving picture, can record a digital MEPG2 (Moving Picture Experts Group 2) signal indicative of the digital moving picture which is over 2 hours in duration. A general DVD reproducing apparatus for reproducing the audio and video signals recorded on the DVD has a construction as shown in FIG.
1
.
Referring to
FIG. 1
, a DVD
10
mounted on a driving axle of a spindle motor
12
rotates at a constant speed. A pickup device
14
contained in a deck (not shown) irradiates a laser beam onto the DVD
10
and receives a reflected beam from the DVD
10
to read data recorded on the DVD
10
. Further, the pickup device
14
controls rotation and loading of the DVD
10
and transfer of a pickup head (not shown). An RF (Radio Frequency) amplifier
16
amplifies the signal picked up by the pickup device
14
and shapes the amplified signal. A digital signal processor (DSP)
18
demodulates (16-8 demodulation) the signal output from the RF amplifier
16
, and performs data PLL (base Locked Loop) by means of synchronous detection, descrambling, error detection, error correction, and track buffer control function.
Specifically, the DSP
18
includes a 16-8 demodulator (not shown) and an error correction circuit (not shown). The 16-8 demodulator detects synchronization for the input data and 16-8 demodulates the input data to store it into a memory (i.e., track buffer)
20
. The error correction circuit reads the data stored in the track buffer
20
to correct errors of the read data, and then stores the error-corrected data back into the track buffer
20
. Further, the DSP
18
searches the data stored in the track buffer
20
for ID (identification) data representative of a disc position, to provide the ID data to a system controller
22
, and descrambles the remaining data to store it into the track buffer
20
. At the request of an MPEG2 video decoder
30
, the DSP
18
reads and transfers the descrambled data stored in the track buffer
20
to the MPEG2 video decoder
30
. The system controller
22
controls an overall operation of the DVD reproducing apparatus. A pickup servo controller
24
performs focusing servo, tracking servo and pickup transfer servo, under the control of the system controller
22
. A spindle servo controller
26
controls a rotation number of the spindle motor
12
, such that a period of the longest or shortest pit of an EFM (Eight-to-Fourteen Modulated) signal read from the DVD
10
should become a prescribed value. A demultiplexer
28
demultiplexes the signal output from the DSP
18
, to transfer a video signal to the MPEG2 video decoder
30
and an audio signal to an AC3/MPEG audio decoder
34
, respectively. The video and audio output signals from the video decoder
30
and the audio decoder
34
are transferred to a monitor and a speaker via an NTSC encoder
32
and a digital-to-analog converter (DAC)
36
, respectively. A keypad
38
(user interface means) includes a plurality of keys with which the user inputs data or commands. A display
40
displays thereon various state information concerning reproduction of the DVD
10
.
The RF amplifier
16
of the DVD reproducing apparatus generally includes an adder (not shown) and a waveform equalizer (not shown). In operation, since the signal picked up by the pickup device
14
is divided into four signals for the focusing servo and grouped into two groups, these signals undergo an I-V (current-to-voltage) conversion and are then converted into a signal of a single group. The EFM signal amplified and shaped at the adder is a 3-14T pulse train, so that the reproduced signal is susceptible to having an error due to interference between adjacent waveforms. Accordingly, there has long been a demand for a device which can reduce bandwidth of the waveform equalizer as narrow as possible in order to minimize the interference and as a result, reduce the error rate during pulse detection. Conventionally, a jitter meter was used to reduce the bandwidth of the waveform equalizer. That is, the conventional apparatus measured the EFM signal equalized at the waveform equalizer by using the jitter meter, to determine the bandwidth of the waveform equalizer. Accordingly, the bandwidth of the waveform equalizer is determined passively, so that the bandwidth is inaccurately determined, thereby increasing the data error rate undesirably.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method for automatically controlling bandwidth of a waveform equalizer to minimize a data error rate in a DVD reproducing apparatus.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
To achieve the above and other objects, there is provided a method for automatically controlling a bandwidth of a waveform equalizer in a DVD reproducing apparatus. The DVD reproducing apparatus includes an RF amplifier having the waveform equalizer of which the bandwidth is determined by a bandwidth control signal, and a digital signal processor for demodulating an EFM signal equalized by the RF amplifier. The DVD apparatus checks an error cycle of an error signal received from the digital signal processor for a predetermined count cycle, while varying the bandwidth control signal step by step, so as to calculate an error rate according to the bandwidth control signal. Thereafter, the DVD apparatus outputs the bandwidth control signal having a minimum error rate out of the calculated error rates to the RF amplifier, thereby minimizing an error rate during data reproduction.
REFERENCES:
patent: 5533031 (1996-07-01), Dounn et al.
patent: 5610776 (1997-03-01), Oh
patent: 5625509 (1997-04-01), Dovek et al.
patent: 5719843 (1998-02-01), Nakajima et al.
patent: 5721756 (1998-02-01), Liebetreu et al.
patent: 5883866 (1999-03-01), Shimizume et al.
patent: 5954837 (1999-09-01), Kim
Psitos Aristotelis M.
Samsung Electronics Co,. Ltd.
Staas & Halsey , LLP
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