Browse Prior Art Database

Digital Phase Encoded Part Detection for Optical Drives

IP.com Disclosure Number: IPCOM000116729D
Original Publication Date: 1995-Oct-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 6 page(s) / 129K

Publishing Venue

IBM

Related People

Clark, AR: AUTHOR [+4]

Abstract

All read/write optical disks have a Control Track Phase Encoded Part (PEP) Zone where different control information about that particular media is imprinted. The PEP zone is recorded in low frequency phase-encoded modulation, where a ZERO cell is represented by mark(1) followed by a no mark(0) i.e., 10, and a ONE cell is represented by 01. Furthermore, a mark is imprinted by a 3T tone. A bit cell is 656T long with each mark being 328T long. A PEP sector is 177 bit cells in length.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Digital Phase Encoded Part Detection for Optical Drives

      All read/write optical disks have a Control Track Phase Encoded
Part (PEP) Zone where different control information about that
particular
media is imprinted.  The PEP zone is recorded in low frequency
phase-encoded modulation, where a ZERO cell is represented by mark(1)
followed by a no mark(0) i.e., 10, and a ONE cell is represented by
01.  Furthermore, a mark is imprinted by a 3T tone.  A bit cell is
656T
long with each mark being 328T long.  A PEP sector is 177 bit cells
in
length.

      Since the PEP need only be read once for each piece of media,
it is desirable to read and decode it during drive spin-up to achieve
maximum performance.  Thus, the PEP detector must be tolerant to
velocity variation and robust against defects.  It is also desirable
to implement the PEP detection such that it is simple and low cost.

      An all-digital implementation of PEP detection channel where
all of the above requirements are met is introduced in this article.
The hardware that detects and decodes the PEP sector occupies around
3K cells and can easily be implemented in a range of technologies.

      The PEP read channel is divided to two functional blocks,
PEP Detector and PEP controller.  The detector determines whether the
recorded pattern is a mark (3T tone) or is not a mark (no signal),
thus, it is a half cell detector.  The controller does frame
synchronization, phase decoding, and CRC decoding.  A block diagram
is shown in Fig. 1.  An example of various waveforms in the PEP
detector are shown in Fig. 2.  First, a noisy signal is input to the
PEP channel and the peak qualifier output is shown.  The peak
qualifier output goes to the filter which removes the effects of any
noise.  The filtered output is then mapped into half-cell values that
are ready for decoding by the PEP controller.

      The block diagram of the peak detector is shown in Fig. 3.  The
peak-to-peak detector tries to find consecutive peaks that are large
enough (in amplitude) but not too far from each other (in distance)
to be valid peaks of the 3T tone.  The output of the peak-to-peak
detector is denoted by the signal peak-qualifier.  The distance
qualifier and the amplitude qualifiers can be programmable
coefficients.  Notice in waveform diagram that if the signal is too
attenuated then the amplitude qualifi...