JPH0544908Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to a drum motor control device used in a rotary head type reproducing device that reproduces digital signals recorded on a magnetic tape.

[Prior Art and its Problems] A drum motor control device used in a rotary head type reproducing device for reproducing a magnetic tape on which digital signals are recorded has conventionally been configured as shown in FIG. 4.

That is, in FIG. 4, reference numeral 1 denotes a magnetic tape on which digital signals are recorded and is driven to run by a capstan motor (not shown). This magnetic tape 1
Meanwhile, rotating magnetic heads 2 and 3 attached to the peripheral surface of a drum (not shown) at an angle of 180 degrees to each other are rotated and operated by a drum motor 4 to reproduce signals digitally recorded on the magnetic tape 1. do. After this reproduction signal is amplified by a reproduction amplifier 5, it is input to a PLL circuit 9 consisting of a phase comparator 6, a filter 7, and a voltage controlled oscillator (hereinafter abbreviated as VCO) 8. This PLL circuit 9 creates and outputs a data bit clock from the reproduced digital signal.The phase comparator 6 compares the phases of the reproduced digital signal and the oscillation output of the VCO 8, and the output is passed through a filter to the control terminal of the VCO 8. is applied to control the oscillation output of VCO8. The oscillation output of the VCO 8 is sent as a bit clock together with the reproduced digital signal output from the reproduction amplifier 5 to a subsequent signal processing circuit (not shown). On the other hand, the drum motor 4 is equipped with a frequency generator (not shown) that generates a frequency signal according to the rotational speed, and the output signal FG is provided to the waveform circuit 10. A speed error detection circuit 11 obtains a speed error signal SE from the signal FG whose waveform has been shaped by the waveform shaping circuit 10, and sends this to the addition circuit 12.
Further, a rotation synchronization pulse detector 13 for detecting the rotational phase is attached to the drum,
The rotation synchronization pulse PG detected here is sent to the waveform shaping circuit 14. The signal PG whose waveform has been shaped by the waveform shaping circuit 14 is compared with a reference phase, and the phase error detection circuit 15 obtains a phase error signal PE, which is sent to the addition circuit 12. Addition circuit 12
is the driver 16 by adding these signals SE and PE.
The drum motor 4 is servo-controlled with a regular speed and phase relationship.

Normally, the rotation synchronization pulse PG is generated once per rotation of the drum, so the phase error signal PE is similarly updated only every rotation of the drum motor 4. Therefore, this phase error signal
The PE accuracy was low, and the wow and flutter of the drum motor 4 directly affected the playback signal as a jitter component (time axis fluctuation component).

[Purpose of the invention] This invention was made in view of the above-mentioned circumstances, and it is an object of the invention to provide a drum motor control device that can sufficiently reduce the jitter component of a reproduced digital signal.

[Key points of the invention] This invention adds the phase error signal generated by the PLL circuit for creating a bit clock from the reproduced digital signal to the phase error signal of the drum motor, thereby controlling the fluctuation of the reproduced signal in the control system of the drum motor. The jitter component of the reproduced signal is reduced by feeding back the component.

[Embodiment of the invention] An embodiment of the invention will be described below with reference to the drawings.

FIG. 1 shows the circuit configuration thereof, and since the basic configuration is the same as that in FIG. 4, the same parts are given the same reference numerals and the explanation thereof will be omitted.

In the figure, 21 is a filter for matching the phase error signal outputted from the phase comparator 6 in the PLL circuit 9 with the signal of the motor control system, and is usually composed of a low-pass filter. And 22
is a phase error signal of the motor control system, that is, a phase error signal PE outputted by the phase error detection circuit 15, and a phase error signal of the PLL circuit 9 system, that is, a signal DE outputted from the filter 21, by the circuit configuration described later. This is an adder circuit that adds the numbers at a specific ratio and sends the addition result to the adder circuit 12 as a signal TE.

Next, the detailed circuit configuration of this adder circuit 22 will be explained using FIG. 2.

In the figure, the phase error signal DE sent from the filter 21 is sent to the level detector 22 within the adder circuit 22.
a, is input to amplifiers 22b and 22c. The amplifier 22b and the amplifier 22c are set to have different gains, and the amplifier 22b has a larger gain than the amplifier 22c. This amplifier 22b,
The amplified outputs of switch 22c are both sent to the movable terminal side of switch 22d. By the way, the level detector 22a switches and sets the switch 22d according to the level of the signal DE sent thereto. The fixed terminal side of the switch 22d is connected to the input side of the adder 22e. Accordingly, the signal output from either the amplifier 22b or 22c connected to the movable terminal side of the switch 22d by the switching setting of the level detector 22a is input to the adder 22e. On the other hand, the phase error signal PE of the drum motor 4 sent from the phase error detection circuit 15 is also amplified by the amplifier 22f in the adding circuit 22, and then
It is input to the adder 22e. In the adder 22e,
These input signals are added, and the addition result is output as a new phase error signal TE to the adder circuit 12 at the subsequent stage.

In the embodiment with the above configuration, the operation is as follows.

Rotation control of drum motor 4 is performed using signal PG and signal FG.
This is performed using three signals: and the output of the phase comparator 6 in the PLL circuit 9. In this case, the processing for speed control is performed by the waveform shaping circuit 1 in the same manner as in FIG.
0, performed by the speed error detection circuit 11.
On the other hand, in the phase control system, the rotation synchronous pulse detector 1
The rotation synchronization pulse PG detected in step 3 and the internal reference phase signal (usually a 30Hz reference signal in VTRs) are compared in the phase error detection circuit 15, and a phase error signal PE is generated.
is output. Further, from the reproduced digital signal amplified by the reproduction amplifier 5, a bit lock is generated and outputted by the PLL circuit 9. At this time, the phase error signal output from the phase comparator 6 in the PLL circuit 9 passes through the filter 21 and is then input as the signal DE to the adder circuit 22 together with the phase error signal PE of the drum motor 4.

To explain the operation in this adder circuit 22 in detail, first, the phase error signal PE outputted from the phase error detection circuit 15 is amplified by the amplifier 22f and sent to the adder 22e. Further, the phase error signal DE output from the phase comparator 6 via the filter 21 is sent to the amplifiers 22b and 22c, and also to the level detector 22a. The level detector 22a detects the level of the input signal DE, and switches the switch 22d according to the detected level as shown in FIG. That is, when the level (absolute value) of the signal DE is greater than the specified value, the level detector 22a switches the switch 22d.
is connected to the amplifier 22c side (indicated by "L" in the figure). Conversely, if the level (absolute value) of the signal DE is smaller than the specified value, the level detector 22
A connects the switch 22d to the amplifier 22b side (indicated by "U" in the figure). Here amplifier 22b
The gain of the amplifier 22c is set to be larger than that of the amplifier 22c, and the amplified output of either the amplifier 22b or 22c is sent to the adder 22e via the switch 22d by switching the level detector 22a. That is, when the absolute value level of the phase error signal DE is large, it is amplified with a small gain, and when it is small, it is amplified with a large gain and sent to the adder 22e.
This is to improve the accuracy of servo control by emphasizing the phase error caused by the rotation synchronizing pulse PG when the phase difference in the PLL circuit 9 is large, and by emphasizing the phase error of the PLL circuit 9 when the phase difference is small. After these phase error signals DE and PE are amplified by an appropriate amplification factor, they are added by an adder 22e, and the added output is sent to the adding circuit 12 as a new phase error signal TE. performs servo control.

In this way, by feeding back the phase error of the reproduced signal and controlling the drive of the drum motor 4, it is possible to suppress the jitter component of the reproduced signal.

[Effects of the invention] As detailed above, according to this invention, by adding the phase error signal created by the PLL circuit for creating a bit clock from the reproduced digital signal to the phase error signal of the drum motor, Since the fluctuation component of the reproduced signal is fed back to the control system of the drum motor, it is possible to provide a drum motor control device that can sufficiently reduce the jitter component of the reproduced digital signal.

[Brief explanation of the drawing]

Figures 1 to 3 show an embodiment of this invention, with Figure 1 being a block diagram showing the overall circuit configuration, and Figure 2 being a block diagram showing the detailed circuit configuration of the adder circuit in Figure 1. 3 is a diagram showing the correspondence between the signal DE and the setting state of the switch, and FIG. 4 is a block diagram showing the configuration of a conventional drum motor control device. 1... Magnetic tape, 2, 3... Rotating magnetic head, 4... Drum motor, 5... Playback amplifier, 6
...Phase comparator, 7, 21...Filter, 8...
VCO, 9... PLL circuit, 10, 14... Waveform shaping circuit, 11... Speed error detection circuit, 12, 22
... Addition circuit, 13 ... Rotation synchronous pulse detector,
15... Phase error detection circuit, 16... Driver,
22a...Level detector, 22b, 22c, 22
f...Amplifier, 22d...Switch, 22e...
Adder.

Claims (1)

[Claim for Utility Model Registration] A drum motor control device used in a rotary head type playback device that plays back a magnetic tape on which digital signals are recorded, comprising a phase comparator, a filter, and a voltage controlled oscillator, A phase error detection circuit that compares the rotational phase of the drum motor with a reference phase and outputs a phase error signal, and a phase error detection circuit that outputs a phase error signal by comparing the rotational phase of the drum motor with a reference phase. a first addition circuit that adds the output of the phase comparator; a speed error detection circuit that detects the rotational speed of the drum motor and outputs a speed error signal; and a first addition circuit that adds the output of the addition circuit and the speed error detection circuit. A drum motor control device comprising: a second addition circuit that adds the speed error signal and outputs the sum to a drive circuit that drives the drum motor.