JP2781059B2 - Signal processing circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a signal processing circuit in a storage device, a transmission line, and the like.

(Prior Art) Conventionally, in a storage device using light or magnetism, an input signal at the time of storing data or the like and a reproduced signal at the time of reproduction are always different. Also, in the transmission path, an input signal to the transmission path is different from an output signal from the transmission path. That is, the rise and fall times of the waveform of the reproduced signal or the output signal are usually larger than those of the input signal.

In such a case, a signal processing circuit that reproduces the reproduction signal or the output signal into a signal equivalent to a signal at the time of input is generally known.

FIG. 2a shows an example of the aforementioned signal processing circuit,
IMPROVEMENT OF RECORDING DENSITY BY MEANS OF COSIN
E EQUALIZER (IEEE Transactions on Magnetics, Vol.Ma
g-12, No. 6, p746 1976). FIG. 2b is a signal waveform diagram in FIG. 2a. In the figure, reference numeral 21 denotes an input signal, for example, the reproduction signal f described above.
(T) is input. The reproduction signal f (t) input to the input terminal 21 is input to a delay line 23 and a gain adjuster 24 having an attenuation coefficient K via a matching resistor 22.
The delay line 23 has a delay time τ, the input terminal 23a is in a matching state, and the output terminal 23b is in a mismatching state.

The signal f (t−τ) output from the delay line 23 is input to the non-inverting input terminal of the differential amplifier 25, and the signal output from the gain adjuster 24 is input to the inverting input terminal of the differential amplifier 25. . The output signal γ (t) of the differential amplifier 25 is output from the output terminal 26.

Here, since the output terminal 23b of the delay line 23 is in a mismatched state, the input signal to the inverting input terminal of the differential amplifier 25 is the signal Kf input through the matching resistor 22 and the gain adjuster 24.
This is the sum of (t) and the signal K (t−2τ) input through the gain adjuster 24 after being reflected at the output end 23 b of the delay line 23. Thus, the output signal τ (t) of the differential amplifier 25
Is represented by equation (1).

γ (t) = f (t−τ) −Kf (t) −Kf (t−2τ) (1) Therefore, the delay time τ of the delay line 23 and the attenuation coefficient K of the gain adjuster 24 are set to predetermined values. , The output signal γ
The waveform of (t) can be made sharper than the waveform of the input signal f (t), and a signal having the same waveform as the input signal at the time of storage described above can be obtained.

(Problem to be Solved by the Invention) In a recording apparatus using light, when information is recorded by the length of a recording mark, the shape of the leading edge and the trailing edge of the recording mark are caused by heat during recording described later. Is different from the shape. Therefore, the waveform of the reproduced signal becomes non-linear because the waveform at the time of input cannot be approximated by the simple superposition of the waveforms described above. For this reason, in the conventional signal processing circuit described above, the waveform at the time of input cannot be obtained from the waveform of the reproduction signal.

That is, in an optical disc device, a recording mark is formed by irradiating a medium with a high-intensity laser beam, increasing the temperature of the irradiated portion, and changing the light reflectance due to a change in the magnetization direction, a phase change, or the like. Therefore, the temperature of the medium does not rise sufficiently at the beginning (front edge) of the formation of the recording mark, and the intensity of the laser beam instantaneously decreases at the end (rear edge) of the formation of the recording mark. A tear-shaped recording mark that is thin at the leading edge of the mark and thick at the trailing edge is formed. Therefore, when such a recording mark is reproduced, the waveform of the reproduced signal becomes a waveform that changes gradually at the leading edge of the recording mark and changes sharply at the trailing edge. When the above-mentioned conventional signal processing circuit is used for such a reproduced signal, the rising and falling edges of the waveform can only be sharpened, and a waveform equivalent to the signal waveform at the time of input cannot be obtained. . That is, if the characteristics of the signal processing circuit are matched to either the rising or falling of the signal, the characteristics will not match on the other, and both the rising waveform and the falling waveform will be equivalent to the original signal waveform. Could not be shaped.

An object of the present invention is to provide a signal processing circuit that converts a reproduced signal having a non-linear waveform into a signal having a waveform equivalent to the original signal waveform in view of the above problems.

(Means for Solving the Problems) To achieve the above object, according to the present invention, in a first aspect, a first variation detection circuit for outputting a signal representing a variation of an input signal at predetermined time intervals; An amplifier circuit for receiving an output signal of the first change amount detection circuit, amplifying the amplitude of the signal in a non-linear manner, and amplifying the amplitude of the signal with a predetermined amplification factor different from each other, and outputting the amplification signal; And outputs a signal representing the amount of change of the signal every predetermined time.
And a synthesizing circuit for synthesizing and outputting the input signal and the output signal of the second change amount detecting circuit.

According to a second aspect of the present invention, there is provided the signal processing circuit according to the first aspect, wherein the second change amount detection circuit has a unit for changing an equalization constant for an input signal.

In a third aspect, a first variation detection circuit for outputting a signal representing a variation of the input signal at predetermined time intervals,
Receiving an output signal of the first variation detection circuit, separating the signal according to amplitude polarity, and outputting a separation side signal and a negative side amplitude signal, and the positive side amplitude signal; A second signal for outputting a signal representing a change amount of the signal at predetermined time intervals;
A third change amount detection circuit which receives the negative amplitude signal and outputs a signal representing a change amount of the signal at predetermined time intervals; and a third change amount detection circuit which receives the input signal and the second and third signals. And a synthesizing circuit for synthesizing and outputting the respective output signals of the change amount detecting circuit.

According to a fourth aspect of the present invention, in the signal processing circuit according to the third aspect, the second and third change amount detection circuits include a signal processing circuit having means for changing an equalization constant with respect to an input signal. suggest.

(Operation) According to claim (1) of the present invention, the first change amount detection circuit outputs a signal representing the change amount of the input signal every predetermined time. The output signal of the first change amount detection circuit is output after the amplitude of the signal is nonlinearly amplified by the amplification circuit. That is, the output signal of the first change amount detection circuit is amplified at different amplification degrees, with the positive side amplitude and the negative side amplitude being different from each other. A signal representing the amount of change in the output signal of the amplifier circuit every predetermined time is output by the second change amount detection circuit. Further, the input signal and the output signal of the second change amount detection circuit are combined and output by the combining circuit. Therefore, it is possible to shape the waveform by weighting the rising and falling edges of the input signal.

Further, according to claim (2), the output signal is changed by the second change amount detection circuit.

According to claim (3), the first change amount detection circuit outputs a signal representing the change amount of the input signal every predetermined time. Further, the output signal of the first change amount detection circuit is separated by the separation circuit by the amplification polarity of the signal, and the positive amplitude signal and the negative amplitude signal are separately output. Further, the second change amount detection circuit outputs a signal representing the change amount of the positive side amplitude signal every predetermined time, and the third change amount detection circuit outputs the change amount of the negative side amplitude signal every predetermined time. A signal representing the quantity is output. The combining circuit combines the input signal with the output signals of the second and third change amount detection circuits and outputs the combined signal. Therefore, it is possible to shape the waveform by weighting the rising and falling edges of the input signal.

Furthermore, according to claim (4), each output signal is changed by the second and third change amount detection circuits.

(Embodiment) FIG. 1a is a block diagram showing a first embodiment of the present invention.
FIG. 1b is a diagram showing a signal waveform of each part in the first embodiment. In the figure, reference numeral 11 denotes an input terminal, and 12 denotes a first change amount detecting circuit, which is constituted by, for example, a well-known differentiating circuit, and outputs a signal b obtained by differentiating an input signal a to the input terminal 11.
13 is a nonlinear amplifier circuit having different amplitude characteristics on the positive and negative sides,
The signal b is input and the signal c is output. Reference numeral 14 denotes a second change amount detection circuit including, for example, a differentiation circuit, which inputs the signal c and outputs the signal d. Reference numeral 15 denotes a synthesizing circuit, which outputs a signal e obtained by subtracting the output signal d of the second change amount detection circuit 14 from the input signal a to the input terminal 11 to the output terminal 16.

The first and second change amount detection circuits 12 and 14 described above
As shown in the figure, a differential amplifier 31, a delay line 32 whose input and output ends are matched to eliminate reflection, and a gain adjuster 33 may be used. In FIG. 3, 34 is an input terminal,
The signal input to the terminal 34 is input to the non-inverting input terminal of the differential amplifier 31 via the delay line 32 and is input to the inverting input terminal of the differential amplifier 31 via the gain adjuster 33. . Therefore, by selecting the delay time of the delay line 32 and the gain of the gain adjuster 33, a signal representing the amount of change of the input signal every predetermined time can be output from the differential amplifier 31 to the output terminal 35.

Further, the nonlinear amplification circuit 13 may have any input / output characteristics A as shown in FIG. That is, the amplification degree of the input signal waveform Ei for the positive side amplitude and the negative side amplitude is different, and the signal Eo in which one amplitude is suppressed and the other amplitude is amplified
Should just be output. Specifically, one using the saturation characteristics of a transistor, one using a unidirectional diode, one using a varicap, one using an offset circuit and a square circuit, or an A / D converter, R
It can also be configured using an OM or D / A converter.

FIG. 5 is a circuit diagram showing an example of the nonlinear amplifier circuit 13 using a diode. In the figure, 51 is a differential amplifier,
Its output terminal 54 is connected to an inverting input terminal via a feedback resistor Rf. A diode 52 is connected to the inverting input terminal.
Anodes are connected. The non-inverting input terminal of the differential amplifier 51 is grounded.

The cathode of the diode 52 is connected to the input terminal 53 via the resistor R1. Further, a bias is applied to the cathode of the diode 52 via a variable resistor VR and a resistor R2. The non-linear characteristic of the amplitude of the input / output signal, that is, the input / output characteristic is controlled by this bias. Also,
The amplification of the differential amplifier 51 is set by the resistor R1 and the feedback resistor Rf. Therefore, after the signal input from the input terminal 53 is shaped by the diode 52,
Amplified by 51 and output. The input / output characteristics are as shown in FIG.

The combining circuit 15 can be configured by a differential amplifier. Since the output signal d of the second variable detection circuit 14 is often delayed as compared with the input signal a, the input signal a input to the terminal 65 is connected to the delay line 63 as shown in FIG. By inputting to the inverting input terminal of the differential amplifier 61 through the, the time lag can be corrected. Further, the signal d input to the terminal 64 is supplied to the differential amplifier 61 via the gain adjuster 62.
May be input to the non-inverting input terminal.

Next, the operation of the first embodiment having the above-described configuration will be described with reference to FIG.
This will be described with reference to FIG. 1 and FIG. 1b.

Here, as an example, a case will be described in which the reproduction signal of the optical disk device is the input signal a.

In the optical disk device, when recording information, an optical head (not shown) is driven by a recording circuit (not shown), and a recording power corresponding to the information to be recorded is applied to the recording medium 17 of the optical disk. Record mark on top
18 are formed. As described above, the recording mark 18 has a thin shape at the leading edge and a thick tear shape at the trailing edge.

When reproducing information from the recording mark 18, the recording mark
A laser beam is emitted from an optical head to 18, a signal is extracted as a change in the amount of reflected light (or the polarization angle of the reflected light), and this signal is amplified by an amplifier (not shown) to obtain a reproduced signal a.

The waveform of the reproduced signal a has a leading edge a1 as shown in FIG. 1b.
Has a gentle fall, and the trailing edge a2 rises earlier than the leading edge. The reproduced signal a is input to the first variation detection circuit 12, where it is differentiated to output a signal b. The waveform of the signal b corresponding to the leading edge a1 of the signal a becomes a gentle negative-side amplitude waveform b1, and the waveform of the signal b corresponding to the trailing edge a2 becomes a sharp positive-side amplitude waveform b2. This signal b is a non-linear amplifier
13, where only the positive-side amplitude waveform b2 is suppressed and output as a signal c. That is, the waveform c1 of the signal c corresponding to the waveform b1 of the signal b is equal to the waveform b1, and the amplitude of the waveform c2 of the signal c corresponding to the waveform b2 of the signal b is smaller than the amplitude of the waveform b2. The signal c is further input to the second change amount detection circuit 14, where it is differentiated to output a signal d. At this time, the waveform width and the amplitude value of the waveform d1 of the signal d corresponding to the waveform c1 of the signal c are larger than the waveform width and the amplitude value of the waveform d2 of the signal d corresponding to the waveform c2 of the signal c. The synthesizing circuit 15 outputs a signal e by subtracting the adjusted signal of the signal d from the reproduced signal a. As a result, it is possible to obtain a waveform having sharp falling and rising edges and a symmetrical leading edge and trailing edge. The waveform of the signal e is equivalent to the original signal waveform, that is, the waveform of the signal when information is recorded on the recording medium 17.

Incidentally, in the first embodiment described above, the first and second
Although the change amount detection circuits 12 and 14 are constituted by differentiating circuits, according to experiments, it is preferable that the second change amount detection circuit 14 be as shown in FIG. That is, when the circuit shown in FIG. 3 is used, by changing the gain of the gain adjuster 33, the shape of the upper part e1 and the lower part e2 of the waveform of the signal e shown in FIG. The lower part e3 and the upper part e4 can be shaped identically. Further, experiments have confirmed that the time required for the rise and fall of the signal e can be reduced by about 2.5 times as compared with the related art, and that the half-value recording density can be increased to 1.4 times or more.

 Next, a second embodiment of the present invention will be described.

FIG. 7 is a block diagram showing a second embodiment. In the figure, 71 is an input terminal, 72 is a first change amount detection circuit,
The input signal to the input terminal 71 is input, differentiated and output.
Reference numeral 73 denotes a separation circuit which receives the output signal of the first change amount detection circuit 72, and separates and outputs a positive amplitude signal and a negative amplitude signal. Reference numerals 74 and 75 denote second and third change amount detection circuits, respectively, which are, for example, differentiating circuits. The second variation detection circuit 74 differentiates the positive amplitude signal output from the separation circuit 73 and outputs the differentiated signal. Further, the third change amount detection circuit 75 differentiates and outputs the negative amplitude signal output from the separation circuit 73. Reference numeral 76 denotes a synthesizing circuit that outputs a signal obtained by subtracting the output signals of the second and third change amount detection circuits 74 and 75 from the input signal to the input terminal 71 to the output terminal 77.

The first to third change amount detection circuits 72, 74, and 75 may be those shown in FIG. Further, as in the first embodiment, it is preferable that the second and third change amount detection circuits 74 and 75 are as shown in FIG.

The separating circuit 73 only needs to be capable of separating the positive amplitude and the negative amplitude of the input signal and outputting them separately. As a simple example, two nonlinear amplifier circuits 13 in the first embodiment are used. Can be configured.

Also in the second embodiment having the above-described configuration, the first embodiment
In the same manner as in the embodiment, the weighted correction can be performed separately for each of the leading edge and the trailing edge of the signal input to the input terminal 71, so that the falling edge and the rising edge are sharp, and the leading edge and the trailing edge are corrected. A waveform with symmetrical edges can be obtained. For example, in the case of an optical disk device, the waveform of the signal obtained thereby is equivalent to the waveform of the signal when information is recorded on the recording medium.

The gains of the gain adjusters 33 and 62 and the delay times of the delay lines 32 and 63 provided in the circuits of the first and second embodiments can be fixed. It is also possible to perform dynamic control using learning control or the like.

Further, when the signal processing circuit of the present invention is used in an optical disk device, the gain of the gain adjuster and the nonlinear amplifier circuit can be adjusted for the difference in the reproduced waveform between the inner and outer circumferences of the optical disk and the difference in the reproduced waveform due to the length of the recording mark. The optimum waveform shaping can be always performed by changing the equalization constant such as the bias point in 13. Specifically, a track position detecting circuit is provided, and a signal from the track position detecting circuit is input to the nonlinear amplifier circuit 13 in the first embodiment described above, and the second and third signals are input in the second embodiment. The signal is input to each of the change amount detection circuits 74 and 75, and the suppression ratio of the negative amplitude to the positive amplitude is changed based on the signal. As a result, it is possible to absorb a change in the asymmetrical characteristic of the reproduced waveform caused by an increase in the length of the recording mark due to the track position coming outside the recording surface of the disk. The above-mentioned change of the equalization constant is performed by changing the bias point and the gain, and also by changing the nonlinear amplification circuit 13.
Can be realized by providing a circuit for selecting the passage / non-passage of the signal.

Further, even when the asymmetric characteristic of the reproduced waveform greatly changes depending on the length of the recording mark, a circuit for detecting the waveform width of the reproduced waveform is provided, and the equalization constant is changed based on the output signal of the circuit as described above. If so, it can be dealt with similarly.

In the first and second embodiments described above, the optical disk device, that is, the case of optical modulation recording has been described. However, the same effect can be obtained in the case of magnetic field modulation recording. That is, in the magnetic field modulation recording, the recording mark has a chevron shape, but the leading edge and the trailing edge have different shapes under the influence of the recording state around the recording mark. Therefore,
The reproduced waveform also has a different shape between a portion corresponding to the leading edge and a portion corresponding to the trailing edge of the recording mark. Also in this case, by using the signal processing circuit of the present invention, a signal having a waveform equivalent to the signal waveform at the time of recording can be obtained at the time of reproduction.

Further, the same effect can be obtained even when the signal processing circuit of the present invention is used for a transmission line or the like.

(Effect of the Invention) As described above, according to claims (1) to (4) of the present invention, the leading edge and the trailing edge of the input signal waveform can be individually shaped, so that The rising and falling edges at the leading and trailing edges of the input signal can be sharply shaped, and the leading and trailing edges can be shaped into symmetrical waveforms. Thereby, even a reproduced signal having a non-linear waveform can be converted into a signal having a waveform equivalent to the original signal waveform.

Further, according to claims (2) and (4), in addition to the above-mentioned effects, even if the rate of fluctuation due to the waveform width of the input signal waveform changes, the equalization constant is always changed to change the equalization constant. This provides an excellent effect that appropriate waveform shaping can be performed.

Therefore, when the signal processing circuit of the present invention is used in an optical or magnetic recording device, even if tear-shaped or chevron-shaped recording marks are formed on the medium, the rising and falling edges are sharp and the leading edge is reduced. Since a signal waveform having a symmetrical trailing edge can be obtained, the phase margin can be expanded, for example, the aperture of the eye pattern can be increased. As a result, the signal detection accuracy can be improved, and the recording density can be increased.

[Brief description of the drawings]

FIG. 1a is a block diagram showing a first embodiment of the present invention, and FIG.
FIG. 3 is a diagram showing signal waveforms of various parts in the first embodiment, and FIG.
2a is a block diagram showing a conventional example, FIG. 2b is a signal waveform diagram in the conventional example, FIG. 3 is a block diagram showing an example of a variation detection circuit, and FIG. 4 is a diagram showing input / output characteristics of a nonlinear amplifier circuit. FIG. 5 is a circuit diagram showing an example of a non-linear amplifier circuit, and FIG.
FIG. 7 is a block diagram showing an example of a combining circuit, and FIG. 7 is a block diagram showing a second embodiment of the present invention. 12 first change amount detection circuit, 13 nonlinear amplifier circuit,
14 ... second change amount detection circuit, 15 ... combination circuit, 17 ...
Recording medium, 18 Recording mark, 31, 51, 61 Differential amplifier, 32, 63 Delay line, 33, 62 Gain adjuster 52 Diode, R1, R2, Rf Resistance , VR …… Variable resistor, 72
... A first change amount detection circuit, 73 a separation circuit, 74 a second change amount detection circuit, 75 a third change amount detection circuit, 76
…… Synthesis circuit.

Claims (4)

(57) [Claims] A first change amount detection circuit for outputting a signal representing a change amount of the input signal at predetermined time intervals; an output signal of the first change amount detection circuit; An amplifier circuit for non-linearly amplifying and outputting the side amplitude and the negative side amplitude at different predetermined amplification degrees, and inputting an output signal of the amplifier circuit and outputting a signal representing a change amount of the signal at predetermined time intervals A signal processing circuit comprising: a second change amount detection circuit; and a combining circuit that combines and outputs the input signal and an output signal of the second change amount detection circuit. 2. The signal processing circuit according to claim 1, wherein said second change amount detection circuit has means for changing an equalization constant for an input signal. 3. A first variation detection circuit for outputting a signal representing a variation of an input signal at predetermined time intervals, and an output signal of the first variation detection circuit is input, and the signal is converted by an amplitude polarity. A separating circuit that separates and outputs a positive amplitude signal and a negative amplitude signal; and a second change amount detection circuit that receives the positive amplitude signal and outputs a signal representing a change amount of the signal at predetermined time intervals. A third variation detection circuit that receives the negative amplitude signal and outputs a signal representing a variation of the signal at predetermined time intervals; and the input signal and the second and third variation detection circuits. And a synthesizing circuit for synthesizing and outputting the respective output signals. 4. The signal processing circuit according to claim 3, wherein said second and third change amount detection circuits have means for changing an equalization constant for an input signal.