JPS61151880A - Digital magnetic reproducer - Google Patents

Abstract

PURPOSE:To prevent the reduction of level of the peak detection waveform signal as well as the S/N deterioration and to avoid a code error of the reproduction digital signal, by providing the 1st and 2nd rectifier circuits to extract the positive and negative pole parts of the waveform equivalence reproduction isolation waveform signal separately from each other. CONSTITUTION:The negative pole isolation waveform part of the waveform equivalence reproduction isolation waveform signal B sent from a waveform equivalence circuit is inverted and rectified by the 1st rectifier circuit 10 for output of the positive pole isolation waveform signal B'. While the positive pole isolation waveform part is inverted and rectified by the 2nd rectifier circuit 17 for output of the negative pole isolation waveform signal B''. A polarity discriminating circuit 18 inverts and amplifies the signal B and supplies the polarity discriminating signal K to analog switch circuits 22 and 26 as the control signal. The both-terminal voltage output of a capacitor 30 which is charged and discharged by the output signals of both circuits 22 and 26 is delivered via a buffer amplifier 31 as the peak detection waveform signal C obtained by integrating the signal B. The circuits 22 and 26 prevent the reverse currents to avoid the level reduction of the signal C. The signal C is supplied to a waveform shaping circuit 33. Thus the reproduction digital signal D is obtained with no effect of deflection received.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a digital magnetic reproducing device for reproducing digital signals recorded on a magnetic recording medium, and in particular, for reproducing digital signals from analog signals read by a reproducing head. This invention relates to a digital magnetic reproducing device that can reliably take out.

In recent years, with the rapid development of digital technology, the sound quality has been improved by recording and reproducing audio signals digitally. For example, in audio tape recorders, By recording PCM-modulated audio signals on magnetic tape, and reproducing and demodulating this digitally recorded magnetic tape, the sound quality is dramatically improved. Here, a digital magnetic reproducing apparatus reproduces a magnetic recording medium on which digital signals are recorded, and has a configuration shown in FIG. That is, the magnetic tape 1 is recorded with the recording current waveform shown in FIG. 6(a), for example.

A PCM modulated audio signal is digitally recorded, and when this magnetic tape 1 is read using the RAD 2 for reproduction, the output signal is a reproduced isolated waveform with band limitations as shown in Figure 6(b). This becomes signal A. Then, this reproduced isolated waveform signal A is ternary (+
. The reproduced isolated waveform signal A outputted from the reproduction head 2 in this manner is amplified in the preamplifier 3 and then supplied to the waveform equivalent circuit 4. The waveform equivalent circuit 4 performs waveform equivalent processing (including amplitude) on the reproduced isolated waveform signal A supplied from the preamplifier circuit 3 so that it has a frequency characteristic with an optimal passband (Nyquist bandwidth). As shown in FIG. 6(C), the isolated waveforms are supplied to the digital signal reproducing circuit 5 as a waveform-equivalent reproduced isolated waveform signal B, which is separated so that the amplitudes of the isolated waveforms are the same and mutual interference is reduced. Here, the digital signal reproducing circuit 5 is constituted by a peak detection circuit 6 and a waveform shaping circuit 7, which are constituted by an integrating circuit or a first-order differentiating circuit. Then, the peak detection circuit 6 integrates the waveform-equivalent reproduced isolated waveform signal B to alternately set positive and negative peaks between adjacent isolated waveforms (see FIG. 6).
A peak detection waveform signal C shown in d) is generated and supplied to the waveform shaping circuit 7. The waveform shaping circuit 7 sets the peak detection waveform signal C to a binary value of 0" or "1", with the center of the eye pattern relative to the aperture amplitude in the peak detection waveform signal C as the discrimination level VB shown in FIG. 6(d). By performing the discrimination, the modulated digital signal corresponding to the recording radio waveform shown in FIG. 6(a), that is, the audio signal is
The reproduced digital signal shown in FIG. 6(e) is extracted. Then, this reproduced digital signal is demodulated in the demodulation circuit 8, so that
For example, an analog audio signal is reproduced as a modulated signal.

<Problems to be Solved by the Invention> However, in the digital magnetic reproducing device having the above configuration, if an integrating circuit is used as the peak detection circuit 6, the signal level decreases, and the opening width of the eye pattern becomes narrower. This eliminates the problem that the S/N ratio deteriorates and code errors occur frequently in the reproduced digital signal. Furthermore, when a differentiating circuit that performs first differentiation of the waveform equivalent reproduced isolated waveform signal B is used as the peak detection circuit 6, there is a problem that the S/N ratio deteriorates significantly because the frequency band becomes wider. . To this end, the present invention prevents the signal level from decreasing and the S/N from deteriorating when extracting the peak detection waveform signal from the waveform-equivalent reproduced isolated waveform signal C, thereby preventing the occurrence of code errors in the reproduced digital signal. It is an object of the present invention to provide a digital magnetic reproducing device that prevents the above problems.

Means for Solving the Problems> Accordingly, the digital magnetic reproducing apparatus according to the present invention includes a peak detection circuit that extracts a peak detection waveform signal that alternately sets positive and negative peaks between adjacent isolated waveforms of a waveform equivalent reproduction isolated waveform signal. and the first . a second rectifier circuit; a polarity discrimination circuit that discriminates the polarity of the waveform equivalent reproduced isolated waveform signal by dividing it into positive, negative, and zero; The first and second rectifiers are respectively connected to the output ends of the second rectifier circuit and operate in opposite directions depending on the output signal of the polarity determining circuit. a second analog switch circuit; The capacitor is charged and discharged by the output signal of the second analog switch circuit, and is configured to integrate only the positive or negative output signal portion of the waveform equivalent reproduced isolated waveform signal.

Function> In the digital magnetic reproducing apparatus having the peak detection circuit configured in this way, the first. The second rotation circuit separates and extracts the positive and negative portions of the waveform-equivalent reproduced isolated waveform signal. And this first one. The output signal of the second rectifier circuit is controlled by the output signal of the polarity discrimination circuit. By the second analog switch circuit,
Since only the output signal is taken out and commonly charged and discharged to the capacitor, this voltage signal at both ends is a peak detection waveform signal in which positive and negative peaks alternate between adjacent isolated waveforms in the waveform equivalent reproduced isolated waveform signal. This is the result. In this case, the first. The signal is supplied to the capacitor only during the output signal generation period of the second rectifier circuit, and the first and second rectifier circuits supply the signal to the capacitor only during the output signal generation period (ff level) of the first and second rectifier circuits. Since the second analog switch circuit is opened and unnecessary discharge of the capacitor is prevented during this period, a drop in the level of the output signal is prevented and the aperture amplitude of the eye pattern is expanded.

<Embodiment> FIG. 1 is a circuit diagram of a main part showing an embodiment of a digital magnetic reproducing apparatus according to the present invention, and particularly shows a digital signal reproducing circuit portion. In the figure, reference numeral 9 denotes a peak detection circuit, which uses the waveform-equivalent reproduced isolated waveform signal B supplied from a waveform equivalent circuit (not shown) as a scarf, and outputs a peak detection signal that alternately sets positive and negative peaks between adjacent isolated waveforms. 10 is a first wave rectifying circuit which takes out the negative polarity portion of the waveform equivalent reproduced isolated waveform signal B, which takes the waveform equivalent reproduced isolated waveform signal supplied via the resistor 11 as the negative polarity input, and has a positive polarity input. Operational amplifier 1 with its end grounded
2, and a diode 13 connected between the negative input terminal and the output terminal of the operational amplifier 12 so that the output terminal side becomes the cathode.
, a diode 14 with seven nodes connected to the output terminal of the operational amplifier 12, and a resistor 15 connected between the negative input terminal of the operational amplifier 12 and the cathode side of the diode 14;
The buffer amplifier 16 amplifies the output signal of the operational amplifier 12 supplied via the diode 14. A second rectifier circuit 17 extracts the positive polarity of the waveform equivalent reproduced isolated waveform signal, and has a configuration in which the polarities of the diodes 13 and 14 in the first rectifier circuit 10 are reversed.

Reference numeral 18 denotes a polarity discrimination circuit that divides and discriminates the waveform-equivalent reproduced isolated waveform signal supplied from a waveform equivalent circuit (not shown) into three types: +l OI-; It is constituted by an inverting amplifier circuit including a transverse amplifier 20 whose negative input terminal is connected to the ground and whose positive input terminal is grounded, and a feedback resistor 21.

22 is a first analog switch circuit for selecting the output signal of the first rectifier circuit 10, and is composed of an N-channel MO5 type transistor 24 whose gate electrode is negatively biased via a resistor 23, and has a polarity determination function. circuit 18
It is turned on only during the period when the positive output signal is supplied through the resistor 25. 26 is a second analog switch circuit for selecting the output signal of the second rectifier circuit 17,
It is constituted by a P-channel MO3 type transistor 28 whose gate electrode is positively biased through a resistor 27, and the negative polarity output signal of the polarity discrimination circuit 18 is connected to the resistor 29.
It is turned on only during the period when it is supplied via . 30
is the first. A capacitor that is charged and discharged by the output signal of the second switching circuit 22 and 26, and this capacitor 3
The voltage at both ends of 0 is outputted as a peak detection waveform signal C via the buffer amplifier 31. Note that 32 is a resistor for setting bias radio waves for the buffer amplifier 31. Next, 33 is a waveform shaping circuit that shapes the peak detection waveform signal C supplied from the peak detection circuit 9, and the central part of the aperture amplitude in the eye pattern of the peak detection waveform signal C is set as the discrimination level "O". The reproduced digital signal is extracted by performing binary discrimination of "or 1", and this waveform shaping circuit 33 determines the eye pattern of the peak detection waveform signal C supplied from the peak detection circuit 9. A discrimination reference signal generation circuit 34 that generates a discrimination reference signal VB that corresponds to the center portion of the aperture amplitude, and a discrimination reference signal V generated from the discrimination reference signal generation circuit 34.
A comparator 35 compares the peak detection waveform signal C supplied from the peak detection circuit 9 with the peak detection waveform signal C supplied from the peak detection circuit 9. Here, the identification reference signal generation circuit 34 separates and extracts the positive and negative polarity portions of the peak detection waveform signal C using, for example, diodes 36 and 37, and outputs the separated outputs from a smoothing circuit consisting of a capacitor 38 and a resistor 39, a capacitor 40, and a resistor. The identification reference signal VB is obtained by adding the averaged signal in the smoothing circuit 41 in the adder 42.

In the circuit configured in this manner, when the waveform equivalent reproduced isolated waveform signal B shown in FIG. The positive isolated waveform portion is inverted and rectified in the second rectifier circuit 17 and output as a positive isolated waveform signal B', and the positive isolated waveform portion is inverted and rectified in the second rectifier circuit 17 and output as a negative isolated waveform signal B''.

On the other hand, the polarity discrimination circuit 18 inverts and amplifies the waveform equivalent reproduced isolated waveform signal B, so that the negative polarity isolated waveform portion is “
H'' signal, a polarity determination signal K that is a zero level signal for the zero level portion of the isolated waveform, and an "L" signal for the positive isolated waveform portion is generated, and the polarity determination signal K is generated, respectively. Therefore, since the first analog switch circuit 22 turns on the transistor 24 only during the negative period of the waveform equivalent reproduction isolated waveform signal B, the first rectifier circuit 10
Only the positive polarity isolated waveform signal B' generated from the positive isolated waveform signal B' is selected and supplied to the capacitor 30. Furthermore, since the transistor 28 is turned on only during the positive period of the waveform equivalent reproduced isolated waveform signal B, the second analog switch circuit 26 selects only the negative isolated waveform signal B generated from the second rectifier circuit 17. It is then supplied to the capacitor 30. Then, this waveform equivalent reproduced isolated waveform signal B and the first .
Table 1 shows the relationship between the second analog switch circuit 25 and 26. On the other hand, the capacitor 30 is connected to the first. While being charged and discharged by the output signals of the second analog switch circuits 22 and 26,
In periods other than when the output signal is positive or negative, the first. Second
Since the analog switch circuits 22 and 26 are each turned off to prevent backflow, the capacitor 30 is connected to the first. Charging and discharging are repeated only when the output signals of the second analog switch and child circuits 22 and 26 are generated. The voltage output across the capacitor 30 is the voltage output from the buffer amplifier 31.
The waveform-equivalent reproduced isolated waveform signal B is integrated and output as the peak detection waveform signal C shown in FIG. 2(b). Here, since the first and second analog switch circuits 22 and 26 prevent backflow during the period when no output is generated, a drop in the level of the peak detection waveform signal C generated from the peak detection circuit 9 is prevented. The peak detection waveform signal C generated from the peak detection circuit 9 is transmitted to the waveform shaping circuit 33.
The positive terminal portion thereof is supplied to a capacitor 38 via a diode 36, and the negative terminal portion thereof is charged to a capacitor 40 via a diode 37. The charging outputs of the capacitors 38 and 40 having different polarities are added together in the adder 42, thereby providing a discrimination standard corresponding to the center portion of the aperture width in the eye pattern for the peak detection waveform signal C. A reference signal VE is determined. The identification reference signal VE obtained in this way is compared with the beep detection waveform signal C in the comparator 35, and the identification reference signal VE is compared with the beep detection waveform signal C at the time when the peak detection waveform signal C crosses the identification reference signal vB. Since the polarity of the output signal is inverted during the process, an accurate reproduced digital signal unaffected by fluctuations can be obtained as shown in FIG. 2(C). In the above embodiment, a case was explained in which an inverting rectifier circuit using an operational amplifier 12 was used as the second rectifier circuit, but when the signal level of the waveform equivalent reproduction isolated waveform signal B is high, As shown in FIG. Second
Rectifier circuit to',! ? ' may be constituted by diodes 43 and 44. In this case, the waveform equivalent reproduced isolated waveform signal B is directly used as the polarity discrimination signal as the polarity determination signal.
Transistor 2 of the second analog switch circuit 22.26
It is sufficient to supply it to the gate electrode of 4.28.

Further, when the signal level of the waveform equivalent reproduced isolated waveform signal B is low, as shown in FIG. 4, for example, an operational amplifier 46, resistors 47 to 50, diodes 51, . A generally well-known level shift circuit 45 constituted by 52 may be added.

<Effects of the Invention> As explained above, the digital magnetic reproducing apparatus according to the present invention extracts adjacent isolated waveforms from a waveform-equivalent reproduced isolated waveform signal obtained by performing waveform equivalent processing on the reproduced isolated waveform signal read by the reproducing head. A peak detection circuit that extracts a peak detection waveform signal with positive and negative peaks alternately between the peaks and a first peak detection circuit that extracts the positive and negative portions of the waveform equivalent reproduction isolated waveform signal.
．． The first rectifier circuit turns on each output signal of the second rectifier circuit only during the output generation period. The output signals of the first and second analog switch circuits are selectively taken out using a second analog switch circuit, and the output signals of the first and second analog switch circuits are peak-held by inputting them to a common capacitor. For this purpose, 1. During the output non-generation period of the second rectifier circuit, the charge charged in the capacitor is the same as that of the first rectifier circuit. Since reverse flow through the second switch circuit is prevented, the level of the extracted peak detection waveform signal is prevented from decreasing, and the amplitude of the aperture in the eye pattern of the output signal is accordingly increased. Therefore, it has an excellent effect of significantly reducing code errors and S/N of the reproduced digital signal.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a digital signal reproducing circuit showing one embodiment of a digital magnetic reproducing device according to the present invention, and FIGS. 2(L) to (C) are operational waveform diagrams of each part in the circuit shown in FIG. 1. , FIGS. 3 and 4 are circuit diagrams showing other embodiments of the peak detection circuit shown in FIG. 1, FIG. 5 is a block diagram showing the basic configuration of a conventional digital magnetic reproducing device, and FIG. a
) to (e) are operation waveform diagrams of each part of the block diagram shown in FIG. 5. 9...Peak detection circuit, 10.10', 17°17'
...First. 2nd rectifier circuit, 18... polarity discrimination circuit,
22.22', 26.26'... 1st. 2nd analog switch circuit, 30... Capacitor, 33... Waveform rectifier circuit, 34... Identification reference signal generation circuit, 35...
・Comparator.

Claims (1)

[Claims] (1) A playback head that outputs a playback isolated waveform signal by reading a digital signal recorded on a magnetic recording medium, a waveform equivalent circuit that waveform-equalizes the playback isolated waveform signal output from this playback head, and this waveform In a digital magnetic reproducing apparatus having a digital signal reproducing circuit for extracting a reproduced digital signal from a waveform-equivalent reproduced isolated waveform signal output from an equivalent circuit, the digital signal reproducing circuit extracts a reproduced digital signal from an adjacent isolated waveform signal of the waveform-equivalent reproduced isolated waveform signal. A digital signal is generated by a peak detection circuit that generates a peak detection signal whose polarity is alternately inverted with peaks between waveforms, and by identifying this peak detection signal with an identification reference signal corresponding to the center of the aperture amplitude in the eye pattern. a waveform shaping circuit for converting the peak detection circuit into a waveform equivalent reproduction isolated waveform signal; The first and second rectifier circuits are connected to the output ends of the rectifier circuits and are controlled to be turned on only during the positive or negative output signal generation period of the first and second rectifier circuits respectively connected to the output terminals of the rectifier circuits.
A digital magnetic reproducing device comprising an analog switch circuit and a capacitor that commonly charges the output signals of the first and second analog switch circuits and outputs the charged output as a peak detection signal.