Modulation apparatus/method, demodulation apparatus/method and program presenting medium

26 Pages·2013·2.7 MB·English

US006496541B1
(12) United States Patent (10) Patent N0.: US 6,496,541 B1
Kahlman et al. (45) Date of Patent: Dec. 17, 2002
(54) MODULATION APPARATUS/METHOD, 5,659,577 A * 8/1997 Ohishi ...................... .. 375/242
DEMODULATION APPARATUS/METHOD 5,881,037 A * 3/1999 Tanaka et al. ........... .. 369/48
AND PROGRAM PRESENTING MEDIUM 5,917,857 A * 6/1999 Tanaka e161. ......... .. 375/253
6,072,756 A * 6/2000 Shigenobu .............. .. 369/47
(75) Inventors: Josephus A. H. M. Kahlman, 6,079,041 A * 6/2000 Kunisa e161. .. 714/752
Eindhoven (NL); Kornelis A. 6,198,710 B1 * 3/2001 Hori et a1. .................. .. 369/59
Schouhamer Immink, Eindhoven
(NL); Gijsbert J. Van Den Enden, FOREIGN PATENT DOCUMENTS
Veldhoven (NL); Toshiyuki Nakagawa,
EP 0902544 A2 3/1999 .......... .. H03M/5/14
Tokyo (JP); Yoshihide Shinpuku,
EP 0903864 A2 3/1999 .......... .. H03M/5/14
Tokyo (JP); Tatsuya Narahara, Tokyo
(JP); Kosuke Nakamura, Tokyo (JP) * cited by examiner
(73) Assignee: Koninklijke Philips Electronics N.V.,
Eindhoven (NL) Primary Examiner—Don N. Vo
Assistant Examiner—Dung X. Nguyen
( * ) Notice: Subject to any disclaimer, the term of this (74) Attorney, Agent, or Firm—Michael E. Belk
patent is extended or adjusted under 35
USC 154(b) by 0 days. (57) ABSTRACT
A DSV control bit determining/inserting unit inserts DSV
(21) Appl. No.: 09/320,812 control bits into an input data string and outputs the string
(22) Filed. May 27 1999 including the DSV control bits to a modulation unit Which
’ converts the string With basic data length of 2 bits into
(30) Foreign Application Priority Data variable length code With basic code length of 3 bits in
accordance With a conversion table and outputs the code
May 29, 1998 (JP) ......................................... .. 10-150280 resulting from the Conversion to a NRZI encoding unit‘ The
(51) Int. Cl.7 ............................................... .. H03M 7/02 conversion table includes substitution codes for limiting the
(52) U.S. c1. .............. .. .. 375/253; 341/59; 360/41 number of Consecutive appearances of a minimum mm and
(58) Field Of Search ............................... .. 375/130, 140, Substitution Codes for keeping a run length limit The
375/146, 253, 288; 369/47, 48, 59, 124; conversion table enforces a conversion rule: the remainder
360/41, 49; 341/59 of division of the “1” count of an element in a data string by
2 having a value of 0 or 1 equals the remainder of division
(56) References Cited of the “1” count of an element in the code resulting from
conversion of the data string by 2.
US. PATENT DOCUMENTS
5,333,126 A * 7/1994 Fukuda et a1. .............. .. 369/59 30 Claims, 7 Drawing Sheets
HUN LENGTH UMIT
ASSURANCE CODE 7 "34
DETECTING UNIT
cowsnwm LENGTH ~ ’32
JUDGING UNIT 35 1 l
)
DATASTRING AFT ER T ‘ 2-3 /36
INSEIITION OF DSV MINIMUM HUN 4 #33 -> CONVEHSI —'
CONTROL Brrs CONSECUTIVE APPEARANCE UNIT
LIMITING CODE 35 - 2 M
DETECTING UNIT ) 4_ 6 [L] 37
V CONVERSION "’ T B}
UNIT 1 U
(mxr) P F
35-3 IE —> F —>¢
)
‘ 641 x E
CONVERSION ——> E
UNIT H
31 35-4
SHIFT REGISTER I) B 12
MODULATION UNIT 12 ——->‘ CONVERSION —>
UNTI'
U.S. Patent Dec. 17, 2002 Sheet 1 0f 7 US 6,496,541 B1
1/1 12 Is
I 2 / RECORDING CODE
DATA STRING DSV CONTROLS" MODULATION‘ NRZI ENCODING STRING
INSEFITING UNIT
TIMING
CONTROL /14
UNIT
MODULATION APPARATUS 1
DATA WORDS I DATA1 I DATA2 |\ DATA3 I\
I II \\ \\
| I \ \\ \\
I I \ \ \ \\
| I \ \ \ \ \
I I I \ \ \
DATA WORDS DATA1 [XII DATA2 |X2| DATA3 lxsl
I \ \ \ \
I \ \
\ \ \
I \ \
I \ \ \
CODE WOFIDS I MODULATE DATA 1 INTO CHANNEL BITS I MODULATE XI AND DATA2 INTO CHANNEL BITS |
FIG. 2

U.S. Patent
Dec- 17, 2002 Sheet 4 0f 7 US 6,496,541 B1
“4 - TIMING
CONTROL
UNIT
PLAYBACK ORIGINAL DATA
DATA SWING DEMODULATION DSV CONTROL BIT BUFFER STRING
‘6"’ UNIT _’ REMOVING UNIT ' _”Z
1 1‘
111 112 11a
OENOOOLARON APPARATUS 100
RON LENGTH uNrr
ASSURANCE CODE "124
DETECTING UNIT
CONSTRAINT LENGTH ~f122
JUDGING UNIT -——
125-1
123 1 l
- / INVERSE’ 3-2 #126
MINIMUM RuN —>CONvERs|oN —
CONSECUTIVEAPPEAHANCE UNIT
m uNrNNCCOOE 125-2 M
, DETECTING UNIT 2 u
1 INVERSE M L
25-» COMPARATOR CONVERSION T
UNIT 1,
125-3 L —>?
1 E
INVERSE' 9-6 x
CONvERs1ON ' E
UNIT R
125-4
‘ 1
DEMODULATION UNIT 111 INVERSE ‘12-111
L- CONVERSION
FIG. 6 UNIT
U.S. Patent Dec. 17, 2002 Sheet 5 0f 7 US 6,496,541 B1
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U.S. Patent
Dec. 17, 2002 Sheet 6 0f 7 US 6,496,541 B1
QsTART 0F HEMOVEL OF osv CONTROL BITS)
coum ~’s1
s2
YES
NO
S3
OUTPUT
TFIANSMIT DATA I
55
YES
NO
FIG. 8
11 12 212 13
I I I I
DATA
nsv CONTHOLBITT
STRING MODULATION SYNCHRONI- F NRZI ENCODING
DETERMINING) ZATION SIGNAL
UNIT UNIT
INSERTING UNIT INSEHTING UNIT
SYNCHRONIZATION
SIGNAL DEI'EH
MINING UNIT r211
MODULATION APPARATUS 1
FIG. 9
U.S. Patent Dec. 17, 2002 Sheet 7 0f 7 US 6,496,541 B1
PLAYBACKDATA 111 222 112 N3
gTHINGAHER o ) SYNCHRONIT) ) )
YNCHRONIZATI N . . \
REMOVING UNIT
SYNCHRONIZATION
SIGNAL mann
F
FYINGUNIT N221 D-MODULAHONAPPARATUS100
FIG. 10
do I DSV CONTROL BIT
sy 2 SYNCHRONIZATION SIGNAL
do do do do do do "do dc do do
sy data data data data data sy data data - "-
FIG. 11
US 6,496,541 B1
1 2
MODULATION APPARATUS/ METHOD, minimum run d is preferred. In addition, from the clock
DEMODULATION APPARATUS/METHOD generation point of vieW, it is desirable to have a short
AND PROGRAM PRESENTING MEDIUM maximum inversion period T max or a small maximum run
k. In order to satisfy these requirements, a variety of
modulation techniques have been proposed.
DETAILED DESCRIPTION OF THE To put it concretely, for an optical disc, a magnetic disc or
INVENTION a magneto-optic disc, there are proposed or actually used
modulation techniques for generating a variable length code
Technical Field of the Invention
RLL (1-7) Which is also expressed as (1, 7; m, n; r) and a
10 variable length code RLL (2-7) also expressed as (2, 7 m, n
BACKGROUND OF THE INVENTION
; r) as Well as a ?xed length code RLL (1-7) also expressed
In general, the present invention relates to a modulation as (1, 7; m, n; 1) used in an ISO speci?cation for magneto
apparatus and a modulation method, a demodulation appa optical disc. As for a disc apparatus currently under research
ratus and a demodulation method as Well as a program and development such as an optical disc and a magneto
presenting medium. More particularly, the present invention 15 optic disc having a high recording density, an RLL code
relates to a preferable modulation apparatus and a preferable (Run length Limited Code) With a minimum run d of 1 is
modulation method, a preferable demodulation apparatus commonly used.
and a preferable demodulation method as Well as a prefer The folloWing is an example of a conversion table of the
able program presenting medium used in operations to variable length RLL (1 7) code.
record data onto a recording medium at a high recording 20
density and playback data recorded in a recording medium
TABLE 1
at a high recording density.
RLL 1, 7', 2, 3', 2
PRIOR ART
25 Data Code
When data is transmitted through a transmission line or
recorded onto a recording medium such as a magnetic disc, 1 = 1 11 00x
10 010
an optical disc or a magneto-optic disc, the data is modulated
01 10x
into code matching the transmission line or the recording
1 = 2 0011 000 00x
medium prior to the transmission or recording. As a tech 0010 000 010
nique of modulation, block encoding is knoWn. In the block 30 0001 100 00x
0000 100 010
encoding, a data string is blocked into units each comprising
m><i bits. Each of the units Which is referred to hereafter as
a data Word is then converted into a code Word comprising The symbol x used in the conversion table has the value
n><i bits in conformity With a proper coding rule. For i=1, this “1” for a next folloWing channel bit of “0” or has the value
35
code Word is a ?xed length code. In the case of i having a “00” for a next folloWing channel bit of “1”. The maximum
plurality of values each selected from the range 1 to i max, constraint length r is 2.
a maximum of i, the resulting code Word is a variable length Parameters of the variable length code RLL (1-7) are (1,
code. In general, a code resulting from the block encoding 7; 2, 3; 2). The minimum inversion period T min Which can
is expressed as a variable length code (d, k; m, n; r). be expressed by (d+1)T is thus equal to 2 (=1+1) T Where T
40
Here, i is called a constraint length and r is i max, a is a bit gap in the recording Wave train. The minimum
maximum constraint length. d is the minimum number of 0s inversion period T min Which can be expressed also by
appearing betWeen tWo consecutive 1s. d is referred to as a (m/n)><2Tdata is thus equal to 1.33 (=2/3><2)Tdata Where
minimum run of Us. On the other hand, k is the maximum Tdata is a bit gap in the data string. The maximum inversion
number of 0s appearing betWeen tWo consecutive 1s. k is period T max Which can be expressed by (k+1)T is thus
45
referred to as a maximum run of Us. equal to (7+1)T=8T=8><(m/n)Tdata=8><5.33Tdata. The
By the Way, in an operation to record variable length code detection WindoW Width TW Which can be expressed also by
obtained from the block encoding described above onto a (m/n)Tdata is thus equal to 0.67(=2/3)Tdata.
recording medium such as an optical disc or a magneto-optic By the Way, in a train of channel bits completing the RLL
disc, for example, on to a compact disc (CD) or a minidisc 50 (1-7), modulation shoWn in Table 1, a generation frequency
(MD), the variable length code undergoes an NRZI (Non corresponding to a period of 2T Which is equal to the
Return to Zero Inverted) modulation Wherein each “1” of the minimum inversion period T min is most observed to be
variable length code is interpreted as inversion While a “0” folloWed by generation frequencies corresponding to peri
is interpreted as non-inversion The variable length code ods of 3T and 4T. The fact that a lot of edge information is
completing the NRZI modulation is then recorded. The 55 generated at short intervals such as 2T and 3T is advanta
variable length code completing the NRZI modulation is geous to the generation of a clock signal in many cases.
referred to as a recording Wave train. In the case of a As the recording line density is further increased,
magneto-optic disc conforming to the early International hoWever, the minimum run this time adversely becomes a
OrganiZation for Standardization (ISO) speci?cations pre problem. That is, if minimum runs 2T are generated
scribing a not so large recording density, a train of bits 60 consecutively, the recording Wave train is prone to distortion
completing recording modulation are recorded as they are generated therein. This is because a 2T Wave output is
Without undergoing the NRZI modulation. smaller than other Wave outputs and, hence, easily affected
Let notations T min and T max denote the minimum and by factors such as a defocus and a tangential tilt. In addition,
maximum inversion periods of a recording Wave train at a high line density, recording of consecutive minimum
respectively. In this case, in order to record the recording 65 marks (2T) is also easily affected by disturbances such as
Wave train at a high recording density in the linear speed noise. Thus, an operation to play back the data Will also be
direction, a long minimum inversion period T min or a large prone to errors. In this case, a pattern of errors in reproduc
US 6,496,541 B1
3 4
tion of the data is observed as shifts of the front and rear It is another object of the present invention to prevent
edges of a minimum mark in many cases. As a result, the propagation of a demodulation error from escalating by
length of the generated bit error increases. using a conversion table having a simplest possible con?gu
ration.
As described above, When data is transmitted through a
Means for Solving the Problems
transmission line or recorded onto a recording medium, the
A modulation apparatus according to claim 1 is charac
data is modulated into code matching the transmission line
teriZed by having conversion means for converting input
or the recording medium prior to the transmission or record
data into code in accordance With a conversion table Wherein
ing. If the code resulting from the modulation contains a
said conversion table enforces a conversion rule, according
direct current component, a variety of error signals such as
to Which the remainder of division of a ‘1’ count of an
tracking errors generated in control of a servo of the disc 1O element in a data string by 2 having a value of 0 or 1 shall
drive become prone to variations or jitters are generated alWays be equal to the remainder of division of a ‘1’ count
easily. For this reason, it is thus desirable to make as many of an element in the string of code Words resulting from
efforts to prevent the modulated code from containing a conversion of said data string by 2 and conversion codes of
direct current component as possible. said conversion table comprise:
In order to prevent the modulated code from containing a 15 basic codes for d=1, k=7, m=2 and n=3 Where d is a
direct current component, control of a DSV (Digital Sum minimum run and k is a run length limit;
Value) to prevent the modulated code from containing a ?rst substitution codes for limiting the number of con
direct current component has been proposed. The DSV is a secutive appearances of said minimum run d; and
total found by adding up the values of a train of bits second substitution codes for keeping said run length limit
(symbols of data), Wherein the values +1 and —1 are assigned k.
to “1” and “0” in the train respectively, Which results from A modulation method according to claim 23 is character
NRZI modulation (that is, level encoding) of a train of iZed by including a conversion step of converting input data
channel bits. The DSV is an indicator of a direct current into code in accordance With a conversion table Wherein said
component contained in a train of codes. Decreasing the conversion table enforces a conversion rule, according to
absolute value of the DSV through DSV control is equiva 25 Which the remainder of division of a ‘1’ count of an element
lent to suppressing the magnitude of a direct current com in a data string by 2 having a value of 0 or 1 shall alWays be
ponent contained in a train of codes. equal to the remainder of division of a ‘1 1 count of an
DSV control is not applied to a modulation code gener element in the string of code Words resulting from conver
ated in accordance With the variable length RLL (1-7) table sion of said data string by 2 and conversion codes of said
conversion table comprise:
shoWn as Table 1 given above. DSV control for such a case
is accomplished by calculating a DSV of a train of encoded basic codes for d=1, k=7, m=2 and n=3 Where d is a
bits (a train of channel bits) after the modulation for a minimum run and k is a run length limit;
predetermined period of time and inserting a predetermined ?rst substitution codes for limiting the number of con
number of DSV control bits into the train of encoded bits secutive appearances of said minimum run d; and
35
(the train of channel bits). second substitution codes for keeping said run length limit
At any rate, the DSV control bits are basically redundant k.
bits. If the ef?ciency of the code conversion is to be taken A program presenting medium according to claim 24 for
into consideration, it is thus desirable to reduce the number presenting a program implementing processing including a
of DSV control bits to a smallest possible value. conversion step of converting input data into code in accor
dance With a conversion table data in a modulation apparatus
In addition, if DSV control bits are inserted, it is also
for converting data With a basic data length of m bits into
desirable to make the minimum run d and the maXimum run
variable length code (d, k; m, n; r) With a basic code length
k unchanged. This is because a change in (d, k) Will have an
effect on recording I playback characteristics. of n bits is characteriZed in that said conversion table
Problems To Be Solved by the Invention 45 enforces a conversion rule, according to Which the remain
As described above, in an operation to record RLL code der of division of a ‘1’ count of an element in a data string
by 2 having a value of 0 or 1 shall alWays be equal to the
at a high line density or an operation to play back RLL code
recorded at a high line density, there is raised a problem that remainder of division of a ‘1’ count of an element in the
string of code Words resulting from conversion of said data
a pattern of consecutive minimum runs d Will cause a long
string by 2 and conversion codes of said conversion table
error to be generated easily.
comprise:
In addition, in the case of RLL code such as the RLL (1-7)
code, DSV control necessitates insertion of DSV control bits basic codes for d=1, k=7, m=2 and n=3 Where d is a
into an arbitrary part of a string of code Words (a train of minimum run and k is a run length limit;
channel bits). Since the DSV control bits are basically ?rst substitution codes for limiting the number of con
redundant bits, hoWever, it is desirable to reduce the number 55 secutive appearances of said minimum run d; and
of inserted DSV control bits to a smallest possible value. In second substitution codes for keeping said run length limit
order to keep the minimum run and the maXimum run at k.
constant values, hoWever, the number of DSV control bits is A demodulation apparatus according to claim 25 is char
at least 2. It is thus desirable to reduce the number of DSV acteriZed by having conversion means for converting input
control bits to an even smaller value. code into data in accordance With a conversion table Wherein
The present invention addresses the problems described said conversion table enforces a conversion rule, according
above. It is an object of the present invention to alloW DSV to Which the remainder of division of a ‘1’ count of an
control to be eXecuted for producing high ef?ciency control element in a data string by 2 having a value of 0 or 1 shall
bits on RLL code of (d, k; m, n) Where the minimum run d alWays be equal to the remainder of division of a ‘1’ count
=1, that is RLL code of (1, 7; 2, 3) so that the number of 65 of an element in the string of code Words resulting from
consecutive minimum runs is reduced While the minimum conversion of said data string by 2 and conversion codes of
run and the maXimum run are being kept. said conversion table comprise: