JPH0487046A - Magnetic tape reproducing device - Google Patents

Abstract

PURPOSE:To indirectly detect the rotating speed of a cylinder and to reduce the thickness of the cylinder by extracting a clock signal synchronized with a regenerative signal from the regenerative signal reproduced by a magnetic head and generating a signal corresponding to a frequency deviation between this clock signal and a reference clock signal as a speed error signal. CONSTITUTION:The regenerative signal reproduced by reproducing heads 3a and 3b is amplified, while the clock signal synchronized with the regenerative signal is extracted from the regenerative signal, and the signal corresponding to a frequency change between this clock signal and the reference clock signal is generated as the speed error signal. By this method, the rotating speed of the cylinder 2 can indirectly be detected, and it is not necessary to fix a detector for detecting the rotating speed of the cylinder 2, and then the thickness of the cylinder can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic tape reproducing apparatus, and more particularly to a magnetic tape reproducing apparatus suitable for reproducing digital information recorded on a magnetic tape.

2. Description of the Related Art Digital audio tape recorders are known as magnetic tape playback devices. This tape recorder is capable of reproducing digital signals recorded on diagonal tracks on magnetic tape.

When reproducing digital signals on a magnetic tape, a cylinder is rotated at a predetermined rotational phase and a predetermined rotational speed according to the recording format on the magnetic tape, and the digital signal is reproduced by a magnetic head fixed to the cylinder. It has become. Conventionally, when controlling the rotation of a cylinder, in order to rotate the cylinder at a predetermined rotation phase and a predetermined rotation speed, a PG multiplied signal output from a PG signal generator attached to the cylinder is used to control the position of a reference rotation phase. The phase difference is used as a phase system error signal, and an FG signal generator that outputs multiple pulse signals for one rotation of the cylinder is attached to the cylinder, and the frequency difference between the FG multiplied signal output from the FG signal generator and the reference rotation speed is determined as the speed. A configuration is adopted in which a rotation control command signal is generated by adding a phase system error signal and a speed system error signal as a system error signal, and the rotation of the cylinder motor is controlled by this rotation control command signal.

Problems to be Solved by the Invention However, in conventional devices, in order to generate rotation control command signals, a PC signal generator and an FG signal generator are installed in the cylinder motor.
A signal generator had to be attached, making it difficult to make the cylinder thinner.

An object of the present invention is to provide a magnetic tape playback device that can indirectly detect the rotational speed of a cylinder.

Means for Solving the Problems In order to achieve the above objects, the present invention provides a tape supply means for supplying a magnetic tape at a specified tension, and a tape winder for winding the magnetic tape supplied by the tape supply means at a specified tension. a capstan motor for transporting the magnetic tape to the tape winding means; a capstan motor driving means for rotating the capstan motor at a constant speed; a cylinder that rotates along the axis, a phase detector that is fixed to the cylinder and detects the rotational phase of the cylinder, and a phase error signal generating means that outputs a signal corresponding to the deviation between the detection output of the phase detector and a reference phase signal. and,
A reproduction amplifier that amplifies the reproduction signal reproduced by the magnetic head, a clock extraction means for extracting a clock signal synchronized with the reproduction signal from the reproduction signal output from the reproduction amplifier, and a clock signal output from the clock extraction means and a reference clock signal. speed error signal generating means for outputting a signal according to the frequency deviation; rotation control command signal generating means for generating a rotation control command signal by adding the phase error signal and the speed error signal; This constitutes a magnetic tape reproducing apparatus having a cylinder driving means for rotationally driving the magnetic tape.

Therefore, according to the present invention, the reproduction signal reproduced by the reproduction head is amplified, a clock signal synchronized with the reproduction signal is extracted from the reproduction signal, and a clock signal synchronized with the reproduction signal is extracted according to the frequency change between this clock signal and the reference clock signal. Since the signal is generated as a speed error signal, the rotational speed of the cylinder can be detected indirectly, and there is no need to fix a detector to the cylinder to detect the rotational speed, making it possible to make the cylinder thinner. Become. In other words, the frequency of the clock signal detected from the playback signal is based on the format of the digital signal recorded on the magnetic tape.If the speed of the magnetic tape during playback is constant, the frequency of the playback clock signal is based on the format of the digital signal recorded on the magnetic tape. It is synchronized with the rotation speed. Therefore, the difference between the frequencies of the clock signal and the reference clock signal becomes a signal proportional to rotational fluctuations of the cylinder, that is, a speed signal.

EXAMPLE Hereinafter, an example of the present invention will be described based on the drawings. FIG. 1 is a block diagram of a magnetic tape reproducing apparatus showing an embodiment of the present invention. In FIG. 1, magnetic heads 3a and 3b are fixed to a rotating cylinder 2, and a PG signal generator 8 is fixed as a phase detector for detecting the rotational phase of the cylinder 2. A supply reel motor 16 as a tape supply means, a reel motor 15 as a tape winding means, and a capstan motor 14 are arranged around the cylinder 2. Then, the reel motor 16 moves the magnetic tape 1 to the cylinder 2 with a specified tension. It is supplied to the reel motor 15 side via the capstan motor 14. The capstan motor 14 is rotationally driven by a capstan motor drive means (not shown) that rotates the capstan motor at a constant speed, and the rotation of the capstan motor 14 causes the magnetic tape 1 to be moved toward the reel motor 15 side. It is designed to be sent to at a constant speed. The magnetic tape 1 is then wound around the reel motor 15 at a specified tension.

The output signals of the magnetic spatulas I"3a and 3b are sent to the RF signal amplifier 4.
is supplied to. The RF signal amplifier 4 serves as a reproduction amplifier and amplifies the reproduction signal reproduced by the magnetic heads 3a and 3b at a predetermined amplification degree, and outputs the amplified signal to the PLL circuit 5. This PLL circuit 5 is configured as a clock extraction means for extracting a clock signal synchronized with the RF multiplied signal, and outputs the clock signal to the speed error generator 7. The speed error generator 7 is configured as speed error signal generating means for outputting a signal corresponding to the frequency deviation between the speed system reference clock signal and the clock signal from the PLL circuit 5 as a speed error signal. The speed error signal is then input to the adder 12.

On the other hand, the PC signal generator 8 is designed to output a PG double signal indicating the rotational phase of the cylinder 2 to a comparator 9, which converts the PC signal into a digital signal.
The converted signal is output to the phase error generator 11. The phase error generator 11 outputs a signal corresponding to the deviation between the signal from the comparator 9 and the reference phase signal 10 to the adder 12 as a phase error signal. The adder 12 is configured as a rotation control command signal generating means that adds the speed error signal and the phase error signal to generate a rotation control command signal. A rotation control command signal is then manually input to the driver circuit 13. The driver circuit 13 is configured as a cylinder drive means that controls the rotation of the cylinder 2 according to a rotation control command signal.

In the above configuration, when the capstan motor 14 is rotated at a predetermined speed, the magnetic tape 1 is sent from the reel motor 16 to the reel motor 15 side at a predetermined speed. At this time, since both the reel motor 16 and the reel motor 15 rotate with a predetermined torque, a predetermined tension is applied to the magnetic tape. Therefore, the magnetic tape 1 can be fed and wound while applying a specified tension to the magnetic tape 1.

On the other hand, when the cylinder 2 rotates, one pulse is output from the PG signal generator every time the cylinder 2 rotates once, and this pulse signal is multiplied by the PG signal and inputted to the comparator 9, and the phase system is controlled according to this pulse signal. The error generator 11 outputs a phase-based error signal.

At this time, the reproduction signal reproduced from the magnetic heads 3a and 3b of the cylinder 2 is amplified by the RF signal amplifier 4,
The amplified signal is input to the PLL circuit 5. When a reproduced signal is input to the PLL circuit 5, a clock signal synchronized with the reproduced signal is output. In this case, various digital signals are stored on the magnetic tape 1 using a modulation method known as 8-10 conversion, and non-modulated signals such as audio signals are stored in the recording process as shown in FIG. As shown in (a), lT.

It is modulated and recorded into four types of pulse waves: 2T, 3T, and 4T. Therefore, when a signal as shown in (a) of FIG. 2 is input to the PLL circuit 5, a signal as shown in (b) of FIG. 2 is input as a clock signal synchronized with this reproduced signal. Output.

The frequency of the reproduced clock signal is based on the predetermined format of the digital signal recorded on the magnetic tape 1, and if the tape feeding speed during reproduction is constant, the frequency of the reproduced clock signal is synchronized with the rotational speed of the cylinder 2. Become something. Therefore, if the speed error generator 7 outputs a signal corresponding to the frequency deviation between the reproduced clock signal and the speed-based reference clock signal 6, this signal becomes a signal proportional to the rotational fluctuation of the cylinder 2.

When the speed error signal and the phase error signal are added by the adder 12, a rotation control command signal is output from the adder 12, and the driver circuit 1 is controlled according to this rotation control command signal.
3 rotates the cylinder 2.

Effects of the Invention As is clear from the above embodiments, the present invention extracts a clock signal synchronized with the reproduced signal from the reproduced signal reproduced by a magnetic head, and generates a signal according to the frequency deviation between this clock signal and a reference clock signal. Since the rotation speed of the cylinder is generated as a speed error signal, the rotation speed of the cylinder can be detected indirectly, and the rotation speed of the cylinder can be detected without installing a rotation speed detector on the cylinder. can contribute to the development of

[Brief explanation of drawings]

FIG. 1 is a block diagram of a magnetic tape reproducing apparatus showing an embodiment of the present invention, and FIG. 2 is a waveform diagram for explaining the operation of the PLL circuit shown in FIG. 1. ■...Magnetic tape, 2...Rotating cylinder, 3a, 3
b...Magnetic head, 4...RF signal amplifier, 5...
・PLL circuit, 7...Speed system error generator, 8...
PG signal generator, 9... Comparator, 11... Phase system error generator, 12... Adder, 13... Driver circuit, 14... Capstan motor, 15...
- Reel motor on the winding side, 16... reel motor on the supply side. Name of agent: Patent attorney Takashi Awano 1 person $1 figure

Claims (1)

[Claims] A tape supply means for supplying the magnetic tape at a specified tension, a tape winding means for winding the magnetic tape supplied by the tape supply means at a specified tension, and a capstan motor for transporting the magnetic tape to the tape winding means. ,
A capstan motor drive means that rotates the capstan motor at a constant speed, a cylinder that supports a magnetic head and rotates the magnetic head along the track of the magnetic tape, and is fixed to the cylinder and detects the rotational phase of the cylinder. a phase detector that outputs a signal according to the deviation between the detection output of the phase detector and a reference phase signal, a reproducing amplifier that amplifies the reproduced signal reproduced by the magnetic head, and a reproducing amplifier. a clock extraction means for extracting a clock signal synchronized with the reproduction signal from the output reproduction signal; a speed error signal generation means for outputting a signal according to a frequency deviation between the clock signal output from the clock extraction means and the reference clock signal; A magnetic tape playback device comprising a rotation control command signal generating means for generating a rotation control command signal by adding a phase error signal and a speed error signal, and a cylinder driving means for rotationally driving a cylinder in accordance with the rotation control command signal.