JPH0520618A - Equalizer for digital magnetic recording regeneration - Google Patents

Abstract

PURPOSE: To simplify the circuit constitution and prevent misdetection by making use of a push-pull amplifier and then automatically increasing or decreasing control signal data according to an error rate. CONSTITUTION: An error correcting decoder 40 while correcting errors indicates the rate of the occurring errors by making use of error correction additional bits which are added at the time of recording. According to this error rate, a judgement part 50 sends the control signal data to an amplifier 10 through a D/A converter 60. Its amplification output is supplied to a class 'B' push-pull amplifier 20 and the error occurrence also varies. The judgement part 50 varies an operator for increasing or decreasing the control signal data CD to '-'when the operator is '+' or to '+' when '-' when the latest input error rate inputted from the decoder 40 is larger than a limit error rate, so that the control data CD decreases or increases.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital magnetic recording / reproducing apparatus for recovering an original digital signal without error when the digital signal is recorded on a magnetic medium and reproduced. The present invention relates to a digital magnetic recording / reproducing equalizer that shapes a signal according to the characteristics of a transmission channel.

[0002]

2. Description of the Related Art In order to record and reproduce a digital signal on a magnetic medium, the reproduced signal waveform must be shaped and detected so as to match the characteristics of the transmission channel and then restored to a digital signal. Therefore, the reproducing unit of the digital magnetic recording / reproducing apparatus detects the magnetic medium 1, the head 2 for detecting the signal, the reproducing amplifier 3 for amplifying the detected minute signal, and the waveform as shown in FIG. An equalizer 4 that shapes the signal so that there is no error, a detector 5 that restores the reproduced signal to a digital signal, a demodulator 6 that demodulates the data modulated during recording, and an error correction decoder 7 that corrects the error.
And a data compression / decoding device 8 for restoring the compressed data during recording and a D / A converter 9 for converting into an analog image.

However, because of the characteristics of the head and the medium used for magnetic recording / reproduction, if the same signal as in FIG. 6A is recorded, "1" and "0" change as shown in FIG. 6B. The part extends left and right.

The horizontal expansion of such a signal waveform affects adjacent data. Therefore, it causes a data restoration malfunction from the detector 5 (FIG. 1) that restores the reproduced signal into a digital signal. Also, such extension affects adjacent waveforms, causing signal shifts and amplitude reductions, and causing detection malfunctions.

Therefore, in the conventional digital magnetic recording / reproducing apparatus, a cosine equalizer (cosin EQ) and an automatic equalizer are used as an equalizer for correcting the expansion of the waveform.

[0006]

However, since the cosine equalizer has a complicated circuit configuration and the adjustment state of the circuit is fixed, there is a drawback that adaptive measures cannot be taken when the state of components or the surrounding environment changes, and The equalizer can automatically adjust to the adjustment state of the circuit, but the A / D converter, memory, arithmetic unit,
There is a problem that the configuration of the entire circuit becomes very complicated due to the components such as the D / A converter.

Therefore, an object of the present invention is to simplify the circuit configuration, and to adjust the degree to which the width of the reproduced signal waveform is shortened by automatically adjusting the amplitude of the reproduced signal according to the error detection, thereby causing a detection malfunction. It is to provide an equalizer to prevent.

[0008]

In order to achieve the above-mentioned object, in the present invention, a class B push-pull amplifier is used, and the structure is as follows. That is, the present invention is, in a digital magnetic recording / reproducing apparatus for recording and reproducing a digital signal on a magnetic medium, a variable gain amplifying means for amplifying a reproduced signal read from a magnetic medium through a head, and an output signal of the amplifying means. The digital magnetic recording / reproducing equalizer is characterized by including an equalizing means for adjusting the amplitude and an amplification gain controlling means for adjusting the gain of the amplifying means by an additional bit for error correction during recording.

Further, the present invention is characterized in that the equalizing means comprises a class B push-pull amplifier.

Further, according to the present invention, an error correction decoding unit 40 for generating an error rate by an error correction additional bit added at the time of recording, and an error correction determination for amplifying an amplification gain according to the error rate of the error correction decoding unit 40. Part 5
0, and a D / A converter 60 that provides the output of the error correction judging section 50 by a variable gain amplifying means.

[0011]

According to the present invention, the present invention relates to a digital magnetic recording / reproducing equalizer for shaping a reproduced waveform according to the characteristics of a transmission channel. The push-pull amplifier is used to automatically increase or decrease the control signal data CD according to the error rate, and by adjusting the width of the reproduction signal, detection malfunction is prevented and the reproduced signal is easily shaped.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is used in a digital magnetic recording / reproducing apparatus, and its overall schematic structure is the same as that shown in FIG. 5, so that FIG.

The equalizer 4a of the present invention shown in FIG.
Is a first amplifier 1 for amplifying the signal read by the head.
0, a push-pull amplifier 20 that reduces the width of the waveform via the capacitor C1, and a second amplifier 30 that amplifies the magnitude of the waveform so that the detector 5 (FIG. 1) can operate properly.
Error correction decoding unit 40 for generating error occurrence rate data
An error correction judgment unit 50 for generating appropriate control signal data according to the error rate data of the error correction decoding unit 40; and digital control signal data of the error correction judgment unit 50 converted into analog control signal data. , D / A converter 6 provided to the gain adjustment terminal of the amplifier 10
Composed of and.

The base input of the push-pull amplifier 20 is connected to the output of the first amplifier 10, the emitter output is connected to the input of the second amplifier 30 via a resistor R and a capacitor C2, and the first output of the first amplifier 10 is also connected. The D / A converter 60, the error correction determination unit 50, and the error correction decoding unit 40 are sequentially connected to the gain adjustment terminal of the amplifier 10.

FIG. 2 shows the characteristics of the class B push-pull amplifier. Almost no base current flows from the emitter junction of the transistor until the forward bias exceeds the cutoff voltage Vr. Therefore, when the voltage applied to the bases of the transistors Q1 and Q2 is smaller than the operation cutoff voltage Vr as shown in FIG. 2A, no signal is transmitted to the output end.

If the above characteristics are used, FIG.
When the same signal is input, the width of the waveform is reduced as shown in FIG.

The circuit of FIG. 1 utilizing such characteristics is replaced with the equalizer 4 of FIG. At this time, the degree of width reduction differs according to the magnitude of the amplitude of the signal input to the class B push-pull amplifier.

Such an effect is shown in FIG. Figure 3
When recorded as shown in (a), a waveform as shown in FIG. 3 (b) appears at the output of the first amplifier 10 in FIG. 1 during reproduction. After passing through the equalizer 4a, the signal has a reduced waveform width, as in FIG. 2 (c). Here, if the magnitudes of the amplitudes input to the equalizer 4a are different as shown by the waveforms of α1 and α2 in FIG. 3B, the width is reduced to α1a and α2a in FIG. 5C. different. If such a characteristic is used, an automatic equalization action can be realized.

In the error correction decoding unit 40, the error correction additional bit added at the time of recording is utilized to represent the error rate that is occurring at the same time when the error is corrected. The error correction judgment unit 50 receives the error rate, supplies appropriate control data (control signal data CD described below) to the D / A converter 60,
The D / A converter 60 changes the voltage to a corresponding level and supplies the voltage to the gain adjustment terminal of the first amplifier 10 to adjust the amplitude of the output signal. Eventually, the magnitude of the input signal of the class B push-pull amplifier changes, and the width of the input signal is reduced to a different extent.

As shown in FIG. 4, when the error correction judgment unit 50 produces control data, when the predetermined marginal error occurrence rate is exceeded, the data is increased or decreased so that the degree of width reduction is increased or decreased. , Error correction decoding unit 40
Judgment is made for each processing unit and the adjustment is continued.

The process of generating the control signal data CD by the error correction judgment unit 50 will be described in detail with reference to FIG.

When the recent input error rate NEW input from the error correction decoding unit 40 is not larger than the limit error rate REF, the control signal data CD for adjusting the amplitude of the waveform does not change and the conventional state is maintained. To do. When the latest input error rate NEW is larger than the limit error rate REF,
When the conventional operator OP that increases or decreases the control signal data CD is "+" (increment), it is changed to "-" (decrement), and when the operator OP is "-", it is changed to "+". , The control signal data CD decreases or increases.

Therefore, the latest error rate NEW becomes the old input error rate OLD, and the error correction judgment section 50 accepts the new error rate from the error correction decoding section 40 and adopts it as the latest input error rate NEW. Latest input error rate NE
If W becomes larger than the old input error rate OLD, the operator OP
Nevertheless, the conventional condition is maintained. At this time, the initial value of the control data CD is fixed to the aptitude value obtained in the experiment.

[0024]

In the magnetic recording / reproducing apparatus for digital signals, the width of the reproduced signal must be reduced in order to prevent detection malfunction during reproduction. However, if the present invention is embodied, an equalizing circuit can be simply constructed. Not only is it possible, but it is automatically adjusted according to changes in the components and changes in the ambient conditions.

[Brief description of drawings]

FIG. 1 is a circuit diagram of the present invention.

FIG. 2 is a diagram showing characteristics of a class B push-pull amplifier.

FIG. 3 is a reproduction waveform diagram when the present invention is applied.

FIG. 4 is a flowchart of an error correction determination unit.

FIG. 5 is a block diagram of a digital magnetic recording / reproducing apparatus.

FIG. 6 is a digital recording / reproducing waveform diagram.

[Explanation of symbols]

10 First amplifier 20 push-pull amplifier 30 Second amplifier 40 Error correction decoding unit 50 Error correction judgment section 60 D / A converter Q1, Q2 transistor C1, C2 capacitors R resistance

Claims (3)

[Claims] 1. A digital magnetic recording / reproducing apparatus for recording and reproducing a digital signal on a magnetic medium, comprising: a variable gain amplifying means for amplifying a reproduced signal read from a magnetic medium through a head; and an amplitude of an output signal of the amplifying means. And an amplification gain control means for adjusting the gain of the amplification means by an additional bit for error correction during recording, and an equalizer for digital magnetic recording / reproduction. 2. The digital magnetic recording / reproducing equalizer according to claim 1, wherein the equalizing means is composed of a class B push-pull amplifier. 3. An error correction decoding unit 40 for generating an error rate by an error correction additional bit added at the time of recording.
And an error correction determination unit 50 that amplifies the amplification gain according to the error rate of the error correction decoding unit 40, and a D / A converter 60 that provides the output of the error correction determination unit 50 with a variable gain amplification means. An equalizer for digital magnetic recording and reproducing according to claim 1, wherein