Miscellaneous active electrical nonlinear devices – circuits – and – Specific input to output function – By integrating
Reexamination Certificate
2002-02-20
2004-09-21
Wells, Kenneth B. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific input to output function
By integrating
C327S337000
Reexamination Certificate
active
06794922
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a signal processing circuit and a signal processing method, and more particularly, to a signal processing circuit and a signal processing method for converting a pulse signal into digital data corresponding to a pulse width of the pulse signal.
2. Description of the Related Art
FIG. 1
is a block diagram of an optical disk device.
FIG. 2
is an illustration used for explaining a structure of an optical disk.
An optical disk device
100
shown in
FIG. 1
is a CD-R drive, for example. A CD-R disk
40
is mounted on the optical disk device
100
. The optical disk device
100
records/reproduces information on/from the CD-R disk
40
.
On the CD-R disk
40
, wobbles
40
b
are formed along tracks
40
a
on/from which information is recorded/reproduced, as shown in FIG.
2
. Each of the wobbles
40
b
has a modulated frequency. Reproducing the wobble
40
b
and demodulating the frequency of the reproduction signal generates a frequency-demodulated signal. Accordingly, various control information recorded as the frequency-demodulated signal can be obtained.
The optical disk device
100
comprises an optical system
41
, a spindle motor
42
, a sled motor
43
, a laser driver
44
, a front monitor
45
, an ALPC (Auto Laser Power Control) circuit
46
, a recording compensation circuit
47
, a wobble signal processing unit
48
, an RF amplifier
49
, a focus/tracking servo circuit
50
, a feed servo circuit
51
, a spindle servo circuit
52
, a CD encode/decode circuit
53
, a D/A converter
54
, an audio amplifier
55
, RAMs
56
and
58
, a CD-ROM encode/decode circuit
57
, an interface/buffer controller
59
, and a CPU
60
. The optical disk device
100
records/reproduces information according to commands transmitted from a host computer
61
.
The spindle motor
42
is driven by the spindle servo circuit
52
so as to revolve the disk
40
at a predetermined revolving speed. The optical system
41
is arranged opposite the disk
40
. The optical system
41
projects a laser light on the disk
40
so as to record information on the disk
40
. The optical system
41
also receives a light reflected from the disk
40
so as to output a reproduction signal corresponding to information recorded on the disk
40
. The optical system
41
is controlled by the sled motor
43
and the focus/tracking servo circuit
50
so as to project a light beam at a predetermined position B on the disk
40
.
In this course, the sled motor
43
is driven and controlled by the feed servo circuit
51
so as to move a carriage composing the optical system
41
in a radial direction of the disk
40
. The focus/tracking servo circuit
50
drives and controls a focus/tracking actuator (not shown in the figure) of the optical system
41
so as to perform a focus/tracking control.
The reproduction signal reproduced by the optical system
41
is supplied to the RF amplifier
49
The RF amplifier
49
amplifies the reproduction signal. A main signal of the reproduction signal is supplied to the CD encode/decode circuit
53
, and is decoded by the CD encode/decode circuit
53
.
The CD-ROM encode/decode circuit
57
performs processes, such as processes of encoding/decoding ECC (Error Correction Coding) typical of a CD-ROM, and a process of detecting a header. The RAM
56
is used as a working storage for the processes performed by the CD-ROM encode/decode circuit
57
. The interface/buffer controller
59
transmits and receives data to/from the host computer
61
, and controls a data buffer. The RAM
58
is used as a working storage for the interface/buffer controller
59
.
Besides, when the disk
40
is an audio disk, the signal demodulated by the CD encode/decode circuit
53
is supplied to the D/A converter
54
, and is converted from digital to analog. Then, the analog signal is amplified and output by the audio amplifier
55
.
The CPU
60
controls the optical disk device
100
as a whole according to commands transmitted from the host computer
61
.
As mentioned above, on an optical disk such as a CD-R, wobbles are formed beforehand along tracks on which information is to be recorded. The wobbles are detected so as to reproduce a wobble signal. The wobble signal has a modulated frequency. This frequency-modulated (FM) signal is converted into digital data so as to obtain information such as an address indicating a position on the disk. In this course, to obtain accurate information such as an address, the frequency-modulated signal needs to be converted accurately into digital data.
FIG. 3
is a block diagram of an example of a conventional signal processing circuit. FIG.
4
and
FIG. 5
are timing charts of the conventional signal processing circuit.
In
FIG. 3
, a signal processing circuit
100
comprises a both-edge detection circuit
111
, a counter circuit
112
, a latch circuit
113
, and a digital LPF circuit
114
.
The both-edge detection circuit
111
is supplied with a frequency-modulated signal indicated by FIG.
4
-(A) from a terminal
115
. The both-edge detection circuit
111
first compares the supplied frequency-modulated (FM) signal with a zero level so as to generate a pulse signal indicated by FIG.
4
-(B). The pulse signal becomes high-level when the supplied frequency-modulated signal is higher than the zero level, and becomes low-level when the supplied frequency-modulated signal is lower than the zero level. Then, the both-edge detection circuit
111
detects a rising edge and a falling edge of the generated pulse signal so as to generate a both-edge signal (numbered
118
in
FIG. 3
) indicated by FIG.
4
-(C). This both-edge signal is supplied to the counter circuit
112
, the latch circuit
113
and the digital LPF circuit
114
.
The counter circuit
112
is cleared by the both-edge signal supplied from the both-edge detection circuit
111
. The counter circuit
112
counts clocks supplied from a clock terminal
116
. The counter circuit
112
supplies the counted values varying as indicated by FIG.
4
-(D) to the latch circuit
113
.
The latch circuit
113
is supplied with the counted values from the counter circuit
112
and the both-edge signal from the both-edge detection circuit
111
so as to latch the counted values N
1
to Nn. The latch circuit
113
supplies the latched counted values N
1
to Nn to the digital LPF circuit
114
.
The digital LPF circuit
114
is supplied with the counted values from the latch circuit
113
and the both-edge signal from the both-edge detection circuit
111
. The digital LPF circuit
114
digitally performs a low pass filtering process based on the counted values supplied from the latch circuit
113
so as to cut off noise components. The frequency-modulated (FM) signal subjected to the digital filtering process is output from a terminal
117
, and then is subjected to a demodulating process so as to extract information superimposed on the wobble signal.
However, noises are superimposed on the frequency-modulated signal supplied to the both-edge detection circuit
111
.
The frequency-modulated signal supplied to the both-edge detection circuit
111
crosses the zero level a plurality of times due to the noises, as shown in a magnified view in the vicinity of the zero level in FIG.
5
. Therefore, when the frequency-modulated signal in this state is converted into the pulse signal, unnecessary pulses occur before and after the pulse signal, as indicated by FIG.
6
-(A). Due to these unnecessary pulses, a rising edge and a falling edge are detected a plurality of times, as indicated by FIG.
6
-(B). Accordingly, when clocks indicated by FIG.
6
-(C) are counted between the edges indicated by FIG.
6
-(B), a multitude of small counted values are output in the vicinity of the zero level, as indicated by FIG.
6
-(D).
Thereupon, there has been proposed a method for detecting the edges of the pulse signal while excluding periods influenced by the noises. A description will be given, with reference to
FIG. 7
, of the method for detecting the edges of t
Anderson Kill & Olick P.C.
Lieberstein Eugene
Meller Michael N.
Teac Corporation
Wells Kenneth B.
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