| Summary: | 碩士 === 國立臺灣大學 === 電機工程學系 === 85 === The Compact Disc (CD), introduced more than a decade ago,
has become a successful medium for the distribution and
storage of digital information. The CD-ROM has the advan-tage
of large storage capacity and portability etc.; Therefore
it is popular with computer users, publishers and game
makers etc.
On CD, data is pre-stored and must be read by the optical pickup
head. The lens has to focus the laser beam on CD surface,
then following the data track reading. Prestored data read
from CD is analog signal and is called RF signal. In order
to decide 0 or 1, system has to transfer analog data
signal to digital EFM signal, then use Data Phase Locked Loop
(Data PLL) to get corrected data. If the transfer path has
some trouble or becomes unstable, there may be some
reading error. Reading reliability is important in CD-ROM
systems. We will analyze the problem and find the solution to
improve it.
Here, let me simply describe the CD driver data read error
reason: (1) Focusing offset
(2) Tracking offset
(3) Data slicer bandwidth setup
(4) Data PLL''s loop filter design
(5) Focusing compensator design
The chapter of focusing offset is discuss when the laser beam do
not focus on the focus-ing center, what will cause the
data error rate. We will also describe the relationship
between focusing offset and jitter. The chapter of
tracking offset explain when the laser beam do not lock on the
center of data track, it will make how many data error in this
case, and the rela-tionship between tracking offset and
jitter is in our research also. The details will be
described in chapter 5.
In chapter 6, we will use the data slicer bandwidth set value
with data error rate curve in different speed to find a right
setting value. The effect of Data PLL on the data error rate
will be shown in chapter 6, too. Finally, in chapter 7, we
will use the experimental result to check our focusing
compensator to see if it can reduce the focusing error and makes
(C1,C2) error minimal.
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