WO2004090892A1 - Cross-talk cancellation scheme for rll-based storage systems - Google Patents
Cross-talk cancellation scheme for rll-based storage systems Download PDFInfo
- Publication number
- WO2004090892A1 WO2004090892A1 PCT/IB2004/000938 IB2004000938W WO2004090892A1 WO 2004090892 A1 WO2004090892 A1 WO 2004090892A1 IB 2004000938 W IB2004000938 W IB 2004000938W WO 2004090892 A1 WO2004090892 A1 WO 2004090892A1
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- WIPO (PCT)
- Prior art keywords
- signal
- cross
- main signal
- satellite signals
- transitions
- Prior art date
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Classifications
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
- G11B20/10—Digital recording or reproducing
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
- G11B7/005—Reproducing
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B19/00—Driving, starting, stopping record carriers not specifically of filamentary or web form, or of supports therefor; Control thereof; Control of operating function ; Driving both disc and head
- G11B19/02—Control of operating function, e.g. switching from recording to reproducing
- G11B19/04—Arrangements for preventing, inhibiting, or warning against double recording on the same blank or against other recording or reproducing malfunctions
- G11B19/041—Detection or prevention of read or write errors
- G11B19/045—Detection or prevention of read or write errors by detecting mistracking
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
- G11B20/10—Digital recording or reproducing
- G11B20/14—Digital recording or reproducing using self-clocking codes
- G11B20/1403—Digital recording or reproducing using self-clocking codes characterised by the use of two levels
- G11B20/1423—Code representation depending on subsequent bits, e.g. delay modulation, double density code, Miller code
- G11B20/1426—Code representation depending on subsequent bits, e.g. delay modulation, double density code, Miller code conversion to or from block codes or representations thereof
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
- G11B20/22—Signal processing not specific to the method of recording or reproducing; Circuits therefor for reducing distortions
Definitions
- the present invention relates to a cross-talk cancellation method, a computer program for implementing a cross-talk cancellation method, a signal processor comprising cross-talk cancellation means, and an apparatus for reading a signal stored along a track on a storage medium, said apparatus comprising cross-talk cancellation means.
- the present invention relates to storage systems in which data are stored along tracks on a storage medium.
- the inter-track spacing is chosen relatively small to allow for high storage densities.
- This inter-track interference is called cross-talk.
- the invention is advantageously used in such storage systems to improve the recovered signal by removing the cross-talk.
- the invention applies to optical storage systems (DVD, Blu-ray Disc, Small Form Factor Optical Disc%), magnetic storage systems (hard disks notably), magneto-optical storage systems.
- optical storage systems With optical storage systems, the cross-talk is even more severe when radial tilt is present in the system because then the optical spot extends more onto the side tracks.
- a cross-talk removing device is described in US patent 6,134,211. This device has three reading elements simultaneously reading a main track and two adjacent tracks. The three signals that are read by the three reading elements are sampled so as to provide three sequences of samples.
- a cross-talk removing circuit applies adaptive signal processing (for example an LMS adaptive algorithm) to the three sequences of samples to produce a crosstalk-removed sequence of samples associated with the main track that is free of cross-talk components from the adjacent tracks.
- adaptive signal processing for example an LMS adaptive algorithm
- the adaptive processing comprises an adaptive filtering, the filter coefficients being updated so as to converge to zero an error value present in the cross-talk-removed sequence of samples.
- This convergence is achieved by using a reference sample extracting circuit.
- the reference sample extracting circuit extracts the central sample value of three successive sample values.
- the extracted sample value is supplied to a subtractor that calculates the difference between the extracted sample value and a reference value. This difference is used as the error (e) that has to be converged to zero to update the filter coefficients.
- the analog-to-digital converters and the filters are run on a fixed clock.
- a transition from the fixed clock domain to the bit-synchronous domain is done at the output of the cross-talk cancellation circuit by means of a sample rate converter controlled by a time recovery circuit.
- An additional sample rate controller, locked to the time recovery circuit, would be needed for each adjacent track to produce the bit-synchronous samples that are needed to derive the above-described error (e).
- One of the objects of the invention is to propose a solution for cross-talk cancellation that solves the above-mentioned problems.
- the cross-talk cancellation means according to the invention are intended for receiving a main signal associated with a target track and satellite signals associated with side tracks, said main signal showing transitions and runs of various lengths between two transitions. They comprise:
- - filtering means for filtering the satellite signals with adaptive filters, thereby generating filtered versions of the satellite signals
- - updating means for updating the coefficients of the adaptive filters by minimizing the mismatch between the actual and the expected run length between two transitions of the main signal
- the error that is to be minimized when updating the filter coefficients is the mismatch between the actual and the expected run length between two transitions of the main signal.
- the minimization scheme of the invention does not use the notion of ideal transition time. Therefore it does not require the use of bit-synchronous samples.
- the proposed minimization scheme requires frequency lock but not phase lock.
- a first advantage of the proposed minimization scheme is that it resolves the above- mentioned ramp-up problem.
- a second advantage of the proposed minimization scheme is that it can be implemented in an asynchronous architecture without any additional hardware complexity.
- the cross-talk cancellation means of the invention are operated at a fixed clock that is asynchronous with respect to this bit-clock.
- bit clock frequency is different from the fixed clock frequency
- additional time recovery means are provided to derive the ratio between the bit clock frequency and the fixed clock frequency, said ratio being used by said updating means for updating said coefficients.
- FIGS. 1 and 2 are functional block diagrams of examples of an apparatus according to the invention for reading a storage medium
- Figs 3 and 4 are schematic representations of a first and a second configuration of tracks and light spots used in a 3-spot cross-talk cancellation scheme
- FIG. 5 is a functional block diagram of the cross-talk cancellation means according to the invention.
- - Fig.6 is a schematic representation of a received signal showing two transitions and a run between the two transitions.
- the invention applies to storage media having tracks each forming a 360° turn of a spiral line.
- Encoded data are recorded along the tracks.
- the encoding scheme that is used in optical recording system is a Run Length Limited encoding scheme (RLL).
- RLL Run Length Limited encoding scheme
- the tracks exhibit marks corresponding to runs of a same value, and the edges of a mark correspond to a transition between two runs.
- the size of the mark corresponds to the length of the run. It is an integer multiple of a reference unit size mark.
- Figs 1 and 2 show block diagrams of a first and a second example of an apparatus for reading such a disc.
- the apparatus shown in Fig.l carries reference number 6-1.
- the apparatus of Fig.2 carries reference number 6-2.
- the apparatuses 6-1 and 6-2 comprise an optical unit 8 having three reading elements: a main reading element 12 for reading a main signal associated with a main track, and two satellite reading elements 11 and 13 for reading two satellite signals associated with the two tracks that are adjacent to the main track.
- one of these satellite signal is called upper satellite signal, and the other satellite signal is called lower satellite signal.
- the three reading elements transmit three light spots 21, 22 and 23.
- Figs 3 and 4 show the locations of the three light spots 21, 22 and 23 with respect to the three tracks to be read 31, 32 and 33.
- the main light spot 22 is centered on the main track 32.
- the satellite light spots 21 and 23 may be centered either on the satellite tracks 31 and 33 as represented in Fig.3, or between the main track 32 and the adjacent tracks 31 and 33 as represented in Fig;4.
- the satellite signals read by the satellite light spots 21 and 23 in Figs 3 and 4 are said to be "associated with" the adjacent tracks because the light spots 21 and 23 overlap with at least part of the adjacent tracks.
- Fig.4 is advantageous for rewritable optical disc systems because it allows reusing the 3-spot push-pull radial tracking means which are currently available in all such systems (the signal read by the reading elements 11, 12 and 13 and the main light spots 21, 22 and 23 can be used both for tracking and for cross-talk cancellation).
- the three signals that are read by the three reading elements 11, 12 and 13 are input to a signal processor 40 comprising cross-talk cancellation means 42 and decoding means 44.
- the signal produced by the decoding means 44 is input to a reproduction circuit 46 that generates an output signal (for example an audio or a video signal).
- Fig.5 is a functional representation of the cross-talk cancellation means 42.
- the crosstalk cancellation means 42 comprise three analog-to-digital converters 51, 52 and 53 for sampling the main signal, the upper satellite signal and the lower satellite signal.
- the three analog-to-digital converters 51, 52 and 53 operate at a fixed clock 55 and generate a sequence of main samples 62, a sequence of lower satellite samples 61, and a sequence of upper satellite samples 63.
- the sequences of lower and upper satellite samples 61 and 63 are processed by a lower adaptive filter 71 and an upper adaptive filter 73, respectively, which generate a filtered version 81 of the sequence of lower satellite samples and a filtered version 83 of the sequence of upper satellite samples.
- the sequence 62 of main samples is processed by an optional equalizer 90, which generates an equalized sequence of main samples 92. Then a subtractor 93 subtracts the filtered version 81 of the sequence of lower satellite samples and a filtered version 83 of the sequence of upper satellite samples from the equalized sequence 92 of main samples, thereby generating an improved sequence of main samples 102.
- the improved sequence of main samples 102 is generated by subtraction of the filtered version 81 of the sequence of lower satellite samples and a filtered version 83 of the sequence of upper satellite samples from the sequence 62 of main samples.
- the improved sequence of main samples 102 is input to a sample rate converter 120 driven by a time recovery circuit 130 (for example a Phase Lock Loop circuit).
- the output of the sample rate converter 120 is the input of the decoding means 44.
- the improved sequence of main samples 102 and the sequences of lower and upper satellite samples 61 and 63 are processed by lower and upper coefficient updating means 111 and 113.
- the lower and upper coefficient updating means 111 and 113 update the respectively coefficients used by the lower filter 71 and by the upper filter 73.
- S ⁇ . is the sample m of the lower satellite signal
- C m is the sample m of the main signal
- f are the coefficients of the upper filter and fj ⁇ are the coefficients of the lower filter;
- C m is the improved main sample m obtained at the output the subtractor 93.
- the algorithm used to update the filter coefficients is the LMS algorithm (Least Mean Square).
- the driving term Z m of the algorithm (that is the term to be minimized) is the mismatch between the actual and the expected run length between two transitions of the main signal. This means that:
- Fig.6 The cross-talk minimization scheme of the invention will be described below with reference to Fig.6.
- the ratio ⁇ between the PLL-driven bit clock and the fixed clock that runs the analog-to-digital converters 51, 52 and 53 must be available.
- two arrows 141 and 143 indicate that the frequency ratio is supplied to the first and second coefficient updating means 111 and 113.
- the arrows 141 and 143 are represented in dashed lines because they may be omitted if the frequency ratio ⁇ is equal to 1.
- the ratio ⁇ is advantageously supplied by a time recovery circuit external to the cross-talk cancellation means 42 and specifically designed for fast approximate recovery of the bit frequency.
- a time recovery circuit external to the cross-talk cancellation means 42 and specifically designed for fast approximate recovery of the bit frequency.
- Such an external time recovery circuit is already present in most reading apparatuses.
- the wobble clock can be conveniently used for estimating the ratio ⁇ .
- Fig.l gives an example of an implementation that will be advantageously used in such systems: in Fig.l, the external time recovery circuit carries reference number 50-1 and is connected In the path between the main reading element 12 and the cross-talk cancellation means 42. In other systems (mostly in ROM systems), average run length measurements can be used for the same purpose.
- Fig.2 gives an example of an implementation that will be advantageously used in such systems: in Fig.2, the external time recovery circuit carries reference number 50-2 and is connected In the path between the cross-talk cancellation means 42 and the decoding means 44.
- Fig.5 is a schematic representation of the received main signal. Two successive transitions X m and X m+ ⁇ are represented.
- ⁇ m is the time interval between the ideal time of the transition X m and the actual time of the transition X m (in Fig.5, ⁇ m ⁇ 0 );
- ⁇ m+ ⁇ is the time interval between the ideal time of the transition X m+ ⁇ and the actual time of the transition X m+l (in Fig.5, ⁇ m+1 ⁇ 0);
- This first implementation is applicable when the fixed system clock is (nearly) equal to the PLL driven bit clock (that is when the ratio ⁇ is close to 1), but there is no phase lock between the two clocks.
- Z m ⁇ [d m+ ⁇ tm ) « ⁇ m+ ⁇ - ⁇ m + E where £ is an integer independent of the filter coefficients.
- the time interval ⁇ m can be computed approximately as a function g m of the improved main samples:
- the LMS driving parameter to be minimized Z m is also chosen to be equal to the difference between the actual run length d m+ >m and the
- the main signal is equalized.
- the main signal may be processed by an adaptive filter in a similar fashion as the lower and upper satellite signal.
- Figs 1, 2 and 5 are functional representations of an apparatus and a signal processor according to the invention. A hardware implementation thereof may differ from this functional block representation.
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP04722605A EP1614113A1 (en) | 2003-04-07 | 2004-03-23 | Cross-talk cancellation scheme for rll-based storage systems |
JP2006506404A JP2006522424A (en) | 2003-04-07 | 2004-03-23 | Crosstalk cancellation method for RLL-based storage media |
US10/552,059 US20060181975A1 (en) | 2003-04-07 | 2004-03-23 | Cross-talk cancellation scheme for rll-based storage systems |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP03290864.2 | 2003-04-07 | ||
EP03290864 | 2003-04-07 |
Publications (1)
Publication Number | Publication Date |
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WO2004090892A1 true WO2004090892A1 (en) | 2004-10-21 |
Family
ID=33155267
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/IB2004/000938 WO2004090892A1 (en) | 2003-04-07 | 2004-03-23 | Cross-talk cancellation scheme for rll-based storage systems |
Country Status (6)
Country | Link |
---|---|
EP (1) | EP1614113A1 (en) |
JP (1) | JP2006522424A (en) |
KR (1) | KR20050122236A (en) |
CN (1) | CN1771557A (en) |
TW (1) | TW200506830A (en) |
WO (1) | WO2004090892A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2007034369A2 (en) * | 2005-09-22 | 2007-03-29 | Koninklijke Philips Electronics N.V. | Cross-talk cancellation in three-spots push-pull tracking error signal in optical disc systems |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7965789B2 (en) * | 2005-08-22 | 2011-06-21 | Qualcomm Incorporated | Reverse link power control for an OFDMA system |
US8953426B2 (en) * | 2012-10-05 | 2015-02-10 | Panasonic Intellectual Property Management Co., Ltd. | Information reproducing apparatus and information reproducing method |
JP6036798B2 (en) * | 2014-12-19 | 2016-11-30 | ソニー株式会社 | Data detection device, playback device, and data detection method |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0375342A2 (en) * | 1988-12-21 | 1990-06-27 | Matsushita Electric Industrial Co., Ltd. | Data recording/reproducing apparatus using a recording disk |
EP0393719A2 (en) * | 1989-04-21 | 1990-10-24 | Nec Corporation | Signal reproducing apparatus for optical recording and reproducing equipment and method for the same |
EP0604048A2 (en) * | 1992-12-23 | 1994-06-29 | International Business Machines Corporation | Asynchronous digital threshold detector for a digital data storage channel |
US6111710A (en) * | 1997-06-25 | 2000-08-29 | Cirrus Logic, Inc. | Asynchronous/synchronous gain control for interpolated timing recovery in a sampled amplitude read channel |
US6134211A (en) * | 1997-10-07 | 2000-10-17 | Pioneer Electronic Corporation | Crosstalk removing device for use in recorded information reproducing apparatus |
EP1241669A2 (en) * | 2001-03-13 | 2002-09-18 | Pioneer Corporation | Information playback apparatus, signal processing apparatus, information playback method, and optical recording medium |
-
2004
- 2004-03-23 JP JP2006506404A patent/JP2006522424A/en not_active Ceased
- 2004-03-23 KR KR1020057018947A patent/KR20050122236A/en not_active Application Discontinuation
- 2004-03-23 EP EP04722605A patent/EP1614113A1/en not_active Withdrawn
- 2004-03-23 WO PCT/IB2004/000938 patent/WO2004090892A1/en active Application Filing
- 2004-03-23 CN CNA2004800093528A patent/CN1771557A/en active Pending
- 2004-04-02 TW TW093109256A patent/TW200506830A/en unknown
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0375342A2 (en) * | 1988-12-21 | 1990-06-27 | Matsushita Electric Industrial Co., Ltd. | Data recording/reproducing apparatus using a recording disk |
EP0393719A2 (en) * | 1989-04-21 | 1990-10-24 | Nec Corporation | Signal reproducing apparatus for optical recording and reproducing equipment and method for the same |
EP0604048A2 (en) * | 1992-12-23 | 1994-06-29 | International Business Machines Corporation | Asynchronous digital threshold detector for a digital data storage channel |
US6111710A (en) * | 1997-06-25 | 2000-08-29 | Cirrus Logic, Inc. | Asynchronous/synchronous gain control for interpolated timing recovery in a sampled amplitude read channel |
US6134211A (en) * | 1997-10-07 | 2000-10-17 | Pioneer Electronic Corporation | Crosstalk removing device for use in recorded information reproducing apparatus |
EP1241669A2 (en) * | 2001-03-13 | 2002-09-18 | Pioneer Corporation | Information playback apparatus, signal processing apparatus, information playback method, and optical recording medium |
Non-Patent Citations (2)
Title |
---|
RYUICHI KATAYAMA ET AL: "MULTI-BEAM OPTICAL DISK DRIVE FOR HIGH DATA TRANSFER RATE SYSTEMS", JAPANESE JOURNAL OF APPLIED PHYSICS, PUBLICATION OFFICE JAPANESE JOURNAL OF APPLIED PHYSICS. TOKYO, JP, vol. 31, no. 2B, 1 February 1992 (1992-02-01), pages 630 - 634, XP000323491, ISSN: 0021-4922 * |
TOMITA Y ET AL: "25 GB read-only disk system using the two-dimensional equalizer", ISOM. INTERNATIONAL SYMPOSIUM ON OPTICAL MEMORY, XX, XX, vol. 40, no. 3B, 5 September 2000 (2000-09-05), pages 1716 - 1722, XP002251624 * |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2007034369A2 (en) * | 2005-09-22 | 2007-03-29 | Koninklijke Philips Electronics N.V. | Cross-talk cancellation in three-spots push-pull tracking error signal in optical disc systems |
WO2007034369A3 (en) * | 2005-09-22 | 2008-11-27 | Koninkl Philips Electronics Nv | Cross-talk cancellation in three-spots push-pull tracking error signal in optical disc systems |
Also Published As
Publication number | Publication date |
---|---|
TW200506830A (en) | 2005-02-16 |
EP1614113A1 (en) | 2006-01-11 |
JP2006522424A (en) | 2006-09-28 |
KR20050122236A (en) | 2005-12-28 |
CN1771557A (en) | 2006-05-10 |
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