JPS627619B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tape speed control device for controlling the phase of a capstan in a multi-track digital recorder or the like without providing a control track for the capstan servo.

When audio signals and measurement data are recorded on magnetic tape, in order to increase signal fidelity, the original signal is sampled and converted to binary code, etc. [hereinafter referred to simply as PCM (abbreviation for pulse code modulation)] There is a method of recording using a fixed head method.

In such devices, it may be necessary to apply phase control to the capstan during playback due to requests from PCM signal processing. In such cases, it is common to provide a control track on the tape and apply a capstan servo using the playback output from the control track and a reference signal within the device.

However, to improve the effectiveness of tape use,
It is preferable not to provide a control track.
For this purpose, after performing PCM on the original signal, a signal with a synchronization signal inserted for each sample or every integral multiple of the sample is recorded, and during playback, the synchronization signal is extracted from the reproduced PCM signal and used as a signal. If the capstan servo is applied using a reference signal within the device, the objective can be achieved, but a problem occurs at the start of tape running. In high density recording
PCM signal is PE (Phase Encode) or
FM (Freg uency Modulation) or MFM
Modulated FM (Modified FM) is used for recording, but in order to demodulate the PCM signal at the peak intervals of the reproduced analog pulses, the tape speed is adjusted at the beginning of the tape run. If it is low, the signal recorded on the tape will not be demodulated satisfactorily, the synchronization signal will not be extracted, and the capstan servo will not be applied, so the tape speed will not be able to reach its normal value, and the tape A paradox occurs in that the above signal is not demodulated.

Furthermore, in the conventional device shown in Japanese Patent Publication No. 43-56, for example, when a dropout occurs, the reference signal reproduced from the tape is switched to the reference signal obtained from the tachometer via a switching circuit, and When the reproduction signal is obtained again, the reference signal obtained from the tachometer is switched to the reference signal reproduced from the tape.Generally, in such a tape device that uses capstan feeding, the magnetic tape running speed and the capstan rotation speed are Since there are slips and the like in between, the reference signal frequency reproduced from the tape and the output signal frequency obtained from the tachometer do not completely match. Further, even if the magnetic tape speed and the capstan rotational speed ideally match, the phase of the reference signal reproduced from the magnetic tape and the phase of the output signal obtained from the tachometer do not match. Therefore, Article 3b of Special Publication No. 43-56
from state 152 to state 15 as shown in the diagram.
4 and from state 154 to state 156
Even if the tape speed before the transition is normal, the detection device detects a phase error, so the motor has a function to absorb the phase error even though the tape speed is normal. A control signal is provided to effect a variation in tape speed. Therefore, the phase relationship of the reference signal reproduced from the tape with respect to the reference phase formed from the signal output from the rectangular wave oscillator is disturbed. This has the fatal drawback of making data demodulation difficult because the synchronization relationship between the clock and the clock is disturbed.

In order to solve the drawbacks of the conventional device and the above-mentioned paradoxes, the present invention aims to solve the problems of the conventional device and the above-mentioned paradox.
By applying speed control to the capstan and bringing the tape speed close to the normal value, the signal on the tape (for example, MFM) is demodulated and the synchronization signal is
It is extracted and subjected to phase synchronization.

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram of the servo system of the device, and it is assumed that data is recorded on tape using MFM.
In the figure, in the recording mode, a digital signal 1 and a clock 2 are input to an MFM modulator 3, subjected to MFM, and then amplified by a recording amplifier 4 to a recording head 5.
The data is recorded onto the magnetic tape 6 by. In the reproduction mode, the signal reproduced by the reproduction head 7 is amplified by the reproduction amplifier 8, and the clock 10 and data 11 are reproduced by the MFM demodulator 9. Data 11
The synchronization signal 13 is extracted by the synchronization separation circuit 12, and the synchronization signal 13 and the rotation detector 18 are
TAC pulse 19 and reference signal 14 are servo circuit 1
5 and controls the motor 16 to apply servo to the tape speed. 17 is a pinch roller. FIG. 2 is an example of a detailed diagram of the servo circuit 15.
Rotation detector 18 generates TAC pulses 19 with a frequency proportional to the number of rotations of motor 16. Now, at the rising edge of the playback mode, while the speed of the tape 6 is slow, the synchronization signal 13 is not generated, and the TAC pulse 19 output from the rotation detector 18 is input to the speed detection section 20, and the speed The detection unit 20 performs frequency-voltage conversion. That is, a speed error signal 21 whose output voltage value changes according to the rotational speed is output, and is amplified by the motor drive circuit section 23 via the adding section 22 to control the motor 16. When the tape reaches a certain speed, the synchronization signal 13
is generated, and the phase comparator 24 compares the phase with the reference signal 14 to output a phase error signal 25, which is added to the speed error signal 21 and the adder 22 and output to the motor 16.
control.

A more detailed explanation will be given below based on FIGS. 3 to 5. FIG. 3 is a block diagram showing one embodiment of the speed detection section 20, which is known as a frequency-voltage conversion circuit. In the figure, TAC pulse 1
9 triggers the monostable multivibrator 26 having a predetermined delay time. The output from this monostable multivibrator 26 is passed through a low pass filter 2
7 to obtain a speed error signal 21.
FIG. 4 is a diagram showing the relationship between the frequency of the TAC pulse 19 and the output voltage. In the figure, TAC
The output voltage uniquely increases as the frequency of the pulse 19 increases, and saturates when the period of the TAC pulse 19 becomes smaller than the delay time set by the single multivibrator 26. FIG. 5 is a block diagram showing one embodiment of the phase comparator 24 commonly used in phase locked loop circuits (PLL circuits) and the like. In the figure, a synchronization signal 13 is converted into a signal with a predetermined pulse width by a monostable multivibrator 28. The output signal of the monostable multivibrator 28 and the reference signal 14 are input to an exclusive OR circuit 29, and a signal having a pulse width corresponding to the phase difference between the two signals is output from the exclusive OR circuit 29. When this signal is smoothed by a low-pass filter 30, a phase error signal 25 is obtained.A synchronization signal 13 is obtained from the tape 6.
If this cannot be obtained, the output of the monostable multivibrator 28 becomes a constant level signal of "H" level or "L" level, so that the reference signal 14 is output as is as the output of the exclusive OR circuit 29. Therefore, the phase error signal 25 becomes a constant voltage according to the pulse width of the reference signal 14.
Note that the speed detection section 20 and the phase comparison section 24 are not limited to those in the above embodiment.

As described above, the present invention provides a rotation detector for detecting the number of rotations of the capstan shaft or a shaft interlocked with the capstan shaft, and outputs the output from this detector from the frequency
The configuration is such that the rotation of the capstan shaft or a shaft interlocked with the capstan shaft is controlled by the addition result of the voltage-converted speed error signal and the phase error signal obtained by comparing the phases of the reference signal and the synchronization signal reproduced from the tape. , the speed control characteristic and the phase control characteristic can be set independently, stable tape speed control is possible, and the capstan servo can always be operated satisfactorily.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the mutual relationship between a servo circuit and a data demodulation section according to an embodiment of the present invention, and FIG.
FIG. 3 is a block diagram showing an embodiment of the servo circuit, FIG. 3 is a block diagram showing an embodiment of the speed detection section in the present invention, FIG. 4 is an operation diagram showing the operation of the speed detection section in the invention, and FIG. FIG. 5 is a block diagram showing an embodiment of the phase comparator in the present invention.
In the figure, 7 is a reproduction head, 8 is a reproduction amplifier,
9 is an MFM demodulator, 12 is a synchronization separation circuit, 13 is a synchronization signal, 14 is a reference signal, 15 is a servo circuit,
18 is a rotation speed detector, 20 is a speed detection section, 21 is a speed error signal, 22 is an addition section, 23 is a drive circuit section, 24 is a phase detection section, and 25 is a phase error signal.

Claims (1)

[Claims] 1 A fixed head that extracts synchronization signals from data without providing a control track.
In a PCM tape recorder device, a playback means detects data recorded on a tape with a playback head during playback mode and plays back a clock and a digital signal, and a rotation speed that detects the rotation speed of a capstan shaft or a shaft linked thereto. a detector, a speed detection unit that performs frequency-voltage conversion on the output of the rotation speed detector and outputs a first error signal, and a synchronization separation circuit that extracts a synchronization signal from the digital signal reproduced by the reproduction means. , a phase comparison unit that compares the phases of the synchronization signal and the reference signal and outputs a second error signal; and means for controlling the rotation of interlocking shafts.