JPH0460905A - Digital magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To reduce cost as a whole while narrowing the band of a transmission line by outputting the outputs of respective first, second and zero-cross comparators through a gate circuit and inputting those outputs to a PLL circuit for generating a clock synchronized with a regenerative signal. CONSTITUTION:When reproducing a digital ternary signal and converting it to an original digital signal, the output of a first comparator 6 having a threshold level lower than a prescribed value, the output of a second comparator 7 having a threshold level higher than the prescribed value, and the output ofa zero-cross comparator 4 to execute zero-cross comparison after integrating the regenerative signal are outputted through a gate circuit 8 to the regenerative signal after equalizing the waveform. Therefore, the zero-cross detecting signal of the regenerative signal can be obtained corresponding to only the converting point of a recorded signal, and the regenerative clock with high reliability can be generated with high accuracy. Thus, even in a system lowering the rate and narrowing the band with multi-level recording, the clock can be stably generated at low cost.

Description

[Detailed Description of the Invention] [Industrial Application Field 1] The present invention relates to a digital magnetic recording/reproducing device such as a digital VTR, and in particular, to generate a clock synchronized with the reproduced signal when reproducing a digital signal. [Prior Art] Fig. 3 is a block diagram showing the configuration of a reproducing system of a conventional digital magnetic recording/reproducing apparatus, in which (1) is a reproducing amplifier. , (2) is a waveform equalization circuit that removes intersymbol interference during reproduction. (3) is an integrating circuit which converts the peak position between the reproduced signals into a zero cross point.

(4) is a zero cross comparator, and the above integration circuit (3)
The output signal is reproduced into a reproduced signal of °゛l''°゛O'' which is the same as the recorded signal. (5) is a PLL circuit that generates a clock synchronized with the reproduced signal, and a phase comparator (1
0), low-pass filter (hereinafter referred to as F, LPF) (1
1) and voltage controlled oscillator (hereinafter referred to as vCO)
(12).

Next, the operation of the above configuration will be explained with reference to FIG.

Recording on a magnetic recording medium (not shown) is performed by applying a digital level 'i' to the magnetic head as shown in FIG. 4(aX).
A constant current with a constant amplitude is supplied regardless of the frequency, with a binary level current corresponding to "" and "O°". Therefore, during reproduction, the reproduction signal input to the reproduction amplifier (1) has a differential response waveform corresponding to the magnetization transition width of 1"→"o" and "o"'→゛l.

Next, the above signal is processed by a waveform equalization circuit (2) centered on a transversal filter using a delay line, which emphasizes high frequency components with a constant group delay, resulting in pulse slimming and peak shift due to intersymbol interference. has been improved,
The peak position of the reproduced signal becomes a signal as shown in FIG. Being done,
As shown in FIG. 4(b), the signal is obtained by converting the peak position of 2 to a zero cross point.

Subsequently, the above signal is input to the zero cross comparator (4), and as shown in FIG. 4(c), a reproduced signal of °°1", "O", which is the same as the recorded signal, is reproduced.

Note that in a digital magnetic recording/reproducing apparatus, a plurality of digital signals are classified as information words and signal processing is performed, so that it is necessary to generate a clock synchronized with reproduced data during reproduction. In this way, the PLL circuit (5) is used for lock generation, and the output signal (C) of the zero cross comparator (4) and the V of the PLL circuit (5)
A phase comparator (10) detects the phase difference between the clocks shown in FIG. After removing by P F (11),
A clock synchronized with the reproduced data is generated by inputting the clock into the above C0 (12) and outputting it from the VCO (12), which follows the time axis variation of the reproduced signal.

[Problem to be solved by the invention] Since the conventional digital magnetic recording/reproducing device is configured as described above, the information is binarized into "l" and "o", so the transmission path is A wide band is required, and as a result, a wide band circuit and a high-speed comparator are required in each circuit, which poses a problem that increases the cost of the entire device.

This invention was made to solve the above-mentioned problems, and its purpose is to provide a digital magnetic recording and reproducing device that can reduce the overall cost by narrowing the transmission line. It is said that

[Means for Solving the Problems] The digital magnetic recording and reproducing apparatus according to the present invention, when reproducing a digital ternary signal and converting it into the original digital signal, performs the following on the reproduced signal after waveform equalization: After integrating the output of the first comparator having a threshold level below a predetermined value, the output of the second comparator having a threshold level below a predetermined value, and the reproduced signal, a zero cross comparison is performed. The present invention is characterized in that it is configured to output three outputs including the output of the cross comparator via a gate circuit.

[Operation] According to the present invention, the output of the first comparator and the second
The output of the comparator and the output of the zero cross comparator are outputted through a gate circuit, and inputted into a PLL circuit for generating a clock synchronized with the playback signal, which corresponds to the level change point during recording. By extracting only the signal, it is possible to generate a clock that is accurately synchronized with the reproduced signal.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing the configuration of a reproducing system of a digital magnetic recording and reproducing apparatus according to an embodiment of the present invention. In the figure, (1) to (5) are the same as the conventional example shown in FIG. Therefore, the same reference numerals are given and detailed explanation thereof will be omitted.

In 111ffl, (6) is the first comparator and has a threshold level at the negative level. (7) is the second comparator, which sets the threshold to the positive level.
Has a level. These first and second comparators (6), (7) are connected to the output of the waveform equalization circuit (2).

(8) is a gate circuit, zero cross comparator (4),
It is connected to the outputs of the first and second comparators (8) and (7), respectively. (8) is a flip-flop (hereinafter referred to as F/F), which is connected to the gate circuit (8) and the PLL circuit (5).

Next, before explaining the operation of the above configuration, a recording method by this digital magnetic recording/reproducing apparatus will be explained.

As mentioned above, recording on the magnetic recording medium is performed using “1”
This is done at a binary level corresponding to "O". and,
During reproduction, it is necessary to generate a clock that is synchronized with the reproduced data, and a phase error signal is obtained only when the digital signal is converted from '1' to 'Q II' or from 'o' to 1°. As explained above, it is generated based on this phase error signal. Therefore, if a signal with a long series of 0" or 1" is recorded as a recording signal, clock generation will not be possible. It becomes stable.

Therefore, as a recording signal, the digital signal is divided into m bits and converted into a code word of n bits larger than m, so that digital modulation is performed so that "0" or "1" has a limited length. It is common that An example is the 8-10 modulation used in R-DAT. This divides data into 8-bit units and converts them into 10-bit code words. This makes clock generation stable, but on the other hand, it
Conversion to θ bits increases the processing rate and requires a wide recording band.

In the digital magnetic recording/reproducing apparatus according to the embodiment of the present invention, the recorded signal is divided into m bits, and n
This converts the 3-value level signal of the slot into a 3-value level code word of the slot. -2T code, etc. Comparing this code and 8-10 modulation in recording rate, 3B2T
The code is (2/3) times the original data rate,
Compared to (10/8) times the 8-10 modulation, the processing rate is 8/15, which is about 1/2. As a result, the transmission band is also reduced to about 1/2, making it possible to realize a narrow band.

Next, the operation of the configuration of the above embodiment will be explained with reference to FIG.

As a recording signal, the three values (+1
．． When a digital signal recorded on a magnetic recording medium is reproduced at the level O, -1), the reproduction signal input to the reproduction amplifier (1) is +l゛→゛O゛°゛+1"→ -1"O
The differential response waveform corresponds to the magnetization strength and magnetization transition width of "→-1" or vice versa.

Next, the above signal is passed through a waveform equalization circuit (2) to equalize missing parts of the high-frequency signal such as spacing loss in the electromagnetic conversion process using high-frequency emphasis characteristics, and the Nyquist signal is applied to the output of the integration circuit (3). Compensation is made so that the transmission conditions are such that there is no distortion and the roll-off of the first standard is approximately 0.5 to 1.0.

As a result, the waveform equalization circuit (2) outputs a reproduced signal waveform having a peak at the signal conversion point, as shown in FIG. 2(e). Furthermore, the peak value is +1”→
At the conversion point of ゛-1" or ""-t"→"+1", other "+l゛→"o""o"→-
It is possible to reproduce at a sufficiently higher level than the conversion point of 1"-1"→"°O"0"→"+1".

Then, the first comparator (6) and the second comparator (7) detect only the signal conversion points of "+1"→-1" and "-1"→"+1".

In the first comparator (8), “” + 1 ”→“
The threshold level SLI is set at the center between the reproduction peak level value at the signal conversion point of 0'' or 0゛→-1'' and the reproduction peak level value at the signal conversion point of °'+1''→1''.
is set, and in the second comparator 2 (8),
The threshold level is set at the center between the playback peak level value at the signal conversion point of 1゛→“0゛ or O゛→”+1” and the playback peak level value at the signal conversion point of -1”→”+t”. is set.

As a result, the outputs of the first comparator (6) and the second comparator (7) are as shown in FIG.
A window as shown in g) is obtained, and “+1゛→
-1" and the conversion points from "-t" to "+1" become signals with open windows.

Further, the output of the integrating circuit connected to the waveform equalization circuit (2) is provided with a roll-off condition of 0.5 to 1.0 as defined by the above-mentioned Nyquist's first condition as a transmission path. As a result, a reproduced signal waveform as shown in FIG. 2(h) is obtained. In addition, in this signal waveform, the zero cross is guaranteed at the conversion point of the recording signal when "+1" → -
1'' and -1''→°''+1'', and other zero crosses vary in time axis depending on the recording pattern.

In order to reproduce the zero cross point at the recording signal conversion point, a zero cross comparator (
4) Output as shown in Figure 2 (i) and the above “+
The outputs (f) of the first comparator (8) and the second comparator (7) are windowed only for 1"→-1" and °"-1"→"+1".

(g) is input to the gate circuit (8) and gated to obtain an output signal as shown in FIG. 2N).

Subsequently, by processing the output signal (D) in an F/F (!3) that inverts it by a rising edge, the zero cross of the reproduced signal corresponding only to the recording signal conversion point is obtained, as shown in the 21st ffl (k). The detected signal is regenerated.

By inputting such a zero cross detection signal (k) to the PLL circuit (5) for generating a clock synchronized with the reproduced signal, the reproduced signal of multilevel recording can be reproduced in the same manner as in conventional binary recording. The processing results in a good phase error signal.

In addition, in the above embodiment, +1"→-1" and -1'
The recording signal conversion point of °→“”+1” is detected by the output of the amplitude discrimination and integration circuit (3) having two comparators (8) and (7) with different threshold levels using a zero cross comparator signal. However, even if a differentiating circuit is used in place of the integrating circuit (3), the same effect as in the above embodiment can be obtained.

[Effects of the Invention] As described above, according to the present invention, as a signal for reproducing a signal recorded at a ternary level and generating a clock synchronized with the reproduced signal, only the conversion point of the recorded signal is used. Since the corresponding zero-cross detection signal of the reproduced signal can be obtained, a highly accurate and reliable reproduced clock can be generated. Therefore, it is possible to generate a reproduced clock with high accuracy and reliability. , low cost,
This has the effect of being able to generate a clock in a stable manner.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a reproducing system of a digital magnetic recording and reproducing apparatus according to an embodiment of the present invention, and FIG. 2 is a signal waveform diagram showing signal waveforms of each part of FIG. 1 for explaining the operation. FIG. 3 is a block diagram showing the configuration of a reproducing system of a conventional digital magnetic recording/reproducing apparatus, and FIG. 4 is a signal waveform diagram showing signal waveforms of various parts to explain the operation of FIG. 3. (2)...Waveform equalization circuit, (3)...Integrator circuit, (
4)...Zero cross comparator, (8)...First comparator, (7)...Second comparator, (8
)...Gate circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] (1) A digital magnetic recording and reproducing device for recording and reproducing digital ternary signals, which includes a waveform equalization circuit for eliminating at least intersymbol interference during reproduction, and a waveform equalization circuit connected to the waveform equalization circuit to set a predetermined reproduction signal level. a first comparator having a threshold level below a predetermined value of the reproduced signal level, a second comparator having a threshold level above a predetermined value of the reproduced signal level, an integrating circuit connected to the waveform equalizing circuit, and the integrating circuit. It is equipped with a zero cross comparator that compares the output of the above at the zero cross point, and a gate circuit to which the outputs of the first, second and zero cross comparators are connected, and the gate circuit is connected to the level conversion point when recording the digital ternary signal. A digital magnetic recording and reproducing device characterized in that it is configured to extract only corresponding signals.