JPS62154208A - Rotary head type digital tape recorder - Google Patents

Abstract

PURPOSE:To extract exactly a bit synchronizing signal corresponding to a reproducing speed from a reproducing signal by providing a relative speed detecting means for detecting a relative speed at the time of reproducing a signal from a rotation control means and a tape running means, and a bit synchronizing signal extracting means for obtaining a phase synchronization against the reproducing signal and extracting the bit synchronizing signal. CONSTITUTION:A variation of a bit rate can be estimated by detecting a relative speed of a cylinder at the time of reproduction and a magnetic tape. Therefore, a relative speed detecting circuit 21 is connected to a cylinder rotation control circuit 8 and a tape running control circuit 9, a cylinder FG signal and a capstan FG signal are extracted from the respective control circuits, a cylinder rotating speed and a tape running speed are detected, and from both of then, a relative speed at the time of reproduction is detected. Subsequently, by an output of the relative speed detecting circuit 21, a voltage control circuit 22 is controlled and a voltage required for varying a center frequency of a voltage control oscillator 19 is supplied to a voltage adding circuit 23 so as to follow a variation of the bit rate.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a rotating cylinder configured to rotate a cylinder equipped with a set of magnetic heads at high speed to record data such as audio signals on a magnetic tape. This invention relates to a head type digital tape recorder.

[Technical Background of the Invention] Generally, in a rotary head type digital tape recorder, signal reproduction is performed by a circuit system shown in FIG.

The horizontal portion 11 in the figure is composed of a cylinder 3 on which a set of magnetic heads 1.2 is mounted, a capstan 5 for stably running the magnetic tape 4, a pinch roller 6, and a tape guide 7.

In this circuit system, the cylinder 3 is controlled by a cylinder rotation control circuit 8, and the capstan 5 is controlled by a tape running it'
It is controlled by a control circuit 9.

The data recorded on the magnetic tape 4 is then read out by the magnetic head 1.2, and the reproduction amplifier (A) 10,
Equalizer circuit (EQ) 11 and comparator (CO
MP) 12, the waveform is shaped, and the demodulation circuit (DMOD)
13, and roughly error correction circuit (ECC) 1
After error correction is performed by 4, the D/A converter <D
/A) 15 converts it into an analog signal and outputs it.

In such a circuit system, in order to obtain a signal synchronized with the bit rate of the reproduced signal, a bit synchronization signal is extracted from the reproduced signal using, for example, a phase synchronization circuit (X) 16 shown in FIG. If this bit synchronization signal is not extracted, that is, if phase synchronization cannot be obtained in the phase synchronization circuit 16, it becomes impossible to reproduce the signal.

The phase synchronization circuit 16 outputs an error voltage due to the phase difference between the reproduced signal and the bit synchronization signal by a phase comparator (F).
D) 17, a loop filter (LPF) 18 that controls the synchronization pull-in range, noise and out-of-band signal rejection characteristics, and a voltage controlled oscillator (VCQ) 19 that has a free-running frequency and is controlled by an error voltage. The phase error is detected so that the phase of the bit synchronization signal always matches the phase of the reproduced signal, and the voltage controlled oscillator 19 is controlled by feedback to achieve phase synchronization.

By the way, when the rotational speed of the cylinder 3 is controlled to be constant and reproduction is performed by changing only the running speed of the magnetic tape 4, the bit rate of the reproduced signal depends only on the running speed of the magnetic chip 74. If the rate of change in the bit rate due to the rate of change in the running speed of the magnetic tape 4 with respect to the reference value is known in advance through experimentation, the center frequency can be adjusted by adding voltage to the voltage controlled oscillator 19 by the weight of this change. By changing this, the running speed of the magnetic tape can be controlled.

The running speed of the magnetic tape 4 is determined by the capstan FG, for example.
When controlling according to a signal, it is determined by the formula shown below. Note that the capstan FG signal here is a signal that oscillates at X + 12 when the capstan 5 is rotating at a constant speed when playing at the standard speed, and if the rotation speed of the capstan is doubled, , 2X) (oscillates at z.

In the following equation, R represents the diameter of the capstan 5, and fT represents the oscillation frequency of the capstan FG signal.

Tape running speed V = (Rπ)/(1/fv) = Rπ
- fT Also, the rate of change N in the running speed of the magnetic tape 4 is determined by the following equation. In the following equation, VO indicates the standard tape running speed, and ■ indicates the actual tape running speed.

Rate of change N = V / V.

[Problems with Background Art] However, as described above, by arbitrarily changing the playback speed, the rate at the time of playback changes, which is inconvenient for the signal playback system.

That is, if the reproduction speed changes and the bit rate of the reproduced signal changes and deviates from the synchronization pull-in range of the phase synchronization circuit 16, phase synchronization will no longer be obtained and the bit-identical signal essential for signal reproduction will no longer be obtained.

In this case, it would be sufficient to widen the synchronization pull-in range of the phase-locked circuit 16, but if the synchronization pull-in range is expanded, the flywheel effect in the loop may be reduced, and the removal effect for noise and out-of-band signals may be reduced. Phenomena such as deterioration occur, and there is a problem that phase synchronization is lost due to noise from outside the loop, causing problems in signal reproduction.

[Object of the invention] The present invention was made in view of the above-mentioned circumstances, and
When playback is performed at any speed, the flywheel effect in the loop of the phase-locked circuit does not deteriorate, nor does the removal effect for noise and out-of-band signals. The object of the present invention is to provide a rotary head type digital tape recorder that can reliably extract signals from reproduced signals.

[Summary of the Invention] The rotary head type digital tape recorder of the present invention has the following features:
A cylinder rotation control means, a magnetic tape running control means, a signal processing means for reading and processing data recorded on the magnetic tape, and a relative speed during signal reproduction from the rotation control means and the tape running means. a relative speed detection means for detecting, a bit synchronization signal extraction means for obtaining phase synchronization with the reproduced signal and extracting a bit synchronization signal, and a synchronization extraction control means for controlling the bit synchronization extraction means according to the relative speed; Extracted bit synchronization 1. ζ to the signal processing means and data reproducing means for reproducing the data, the bit rate of the reproduced signal, which depends on the relationship between the rotational speed of the cylinder and the running speed of the magnetic tape, can be adjusted. The signal processing means is controlled accordingly.

[Embodiments of the Invention] Hereinafter, details of embodiments of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing the configuration of a circuit system of an apparatus according to an embodiment of the present invention, and parts common to those in FIG. 4 are designated by common reference numerals.

The mechanical part in the figure is composed of a cylinder 3 on which a set of magnetic heads 1.2 is attached, a capster 15 for stably running the magnetic data 14, a pinch roller 6, and a tape guide 7. ing.

In this circuit system, the cylinder 3 is controlled by a cylinder rotation control circuit 8, and the capstan 5 is controlled by a tape running control circuit 9.

The cylinder rotation control circuit 8 and tape running control circuit 9 of the apparatus of this embodiment are connected to a phase synchronization circuit 20.

This phase synchronization circuit 20 has a relative speed detection circuit 21 as shown in FIG. 2, and the output of this relative speed detection circuit 21 controls a voltage control circuit 22.
The output of the voltage adder circuit 23 is used as one input of the voltage adder circuit 23.

The output of a magnetic head 1.2 for reading information recorded on the magnetic tape 4 is connected to the input of a comparator 12 via a reproduction amplifier 10 and an equalizer circuit 11. The output of the comparator 12 is input to the demodulation circuit 13 and also to one input of the phase comparator 17 of the phase synchronization circuit 20, and the output of the phase comparator 17 is input to the loop filter 1.
8 to the other input of the voltage adder circuit 23.

Further, the output of the voltage adding circuit 23 is output from the voltage controlled oscillator 19.
The output of the voltage control detector S19 is connected to the other input of the phase comparator 17 and the bit synchronization input of the demodulation circuit 13.

The output of the demodulation circuit 13 is input to the error correction circuit 14, and the D/A converter 15 outputs an analog reproduction signal.

In the device of this embodiment, when performing playback at an arbitrary speed, the cylinder rotation control circuit 8 and the tape running control circuit 9 allow the mechanism to operate stably. , the information recorded on the magnetic tape 4 is read out by the magnetic head 3, and then read out by the reproduction amplifier 1.
Equalizer circuit 1 for waveform equalization
1, the waveform is shaped by a comparator 12. The signal is further input to the demodulation circuit 13, and the demodulated signal is input to the error correction circuit 14, where it is converted into a correct signal before recording, and then converted into an analog signal by the D/A converter 15.

In order to reproduce the signal at an arbitrary speed, it is necessary to extract a bit synchronization signal corresponding to the target rate from the reproduced signal and supply it to the bit synchronization input of the demodulation circuit 14. Therefore, in the circuit of this embodiment, the bit synchronization signal is extracted using the phase synchronization circuit 20 shown in FIG.

Note that the phase comparator 17 of the phase synchronization circuit 20 outputs an error voltage due to the phase difference between the reproduced signal and the in-loop signal, and this output is sent to the loop filter 18 that controls the synchronization pull-in range and the removal characteristics of noise and out-of-band signals. is input.

Further, the output of the loop filter 18 is input to a voltage adding circuit 23 provided for tracking the center frequency of the voltage controlled oscillator 19 by changing the bit rate.

Further, the output of the voltage control oscillator 19 is controlled by the output of the voltage adder circuit 23, and this output is fed back to the phase comparator 17, thereby performing phase synchronization.

Incidentally, the change in bit rate can be estimated by detecting the relative speed between the cylinder and the magnetic tape during reproduction.

Therefore, the relative speed detection circuit 21 is replaced by the cylinder rotation control circuit 8.
and the tape running control circuit 9, extracting the cylinder rotational speed and capstan FG signal from each control circuit, detecting the cylinder rotational speed and tape running speed, and detecting the relative speed during playback from both. do.

Next, the voltage control circuit 22 is controlled by the output of the relative speed detection circuit 21, and the voltage addition circuit adds the voltage necessary to change the center frequency of the voltage controlled oscillator 19 to follow the change in bit L/-. 23.

Thus, according to the device of this embodiment, phase synchronization that follows changes in the bit rate 1 is possible, and by inputting the extracted bit synchronization signal to the input terminal of the demodulation circuit 13, it is possible to reproduce the signal at any speed. Become.

In this embodiment, the above-mentioned running speed of the magnetic tape 4 is detected using the FG times signal of the take-up reel of the magnetic tape 4 and the winding amount of the magnetic tape 4 when the capstan FG signal cannot be used. It is also possible to determine this by detecting.

That is, as shown in FIG.
By detecting the distance X from the center to the winding amount, the running speed of the magnetic tape 4 can be detected using the following equation. In the following equation, f is the period of the reel FG signal (H7,), and X is the radius of the winding amount of the magnetic tape (m
) is shown.

Running speed of magnetic tape (V) = (2Xπ)/l = (2Xπ)/(1/f) [Effects of the Invention] As explained above, the rotary head type digital tape recorder of the present invention can control the rotation of the cylinder. a magnetic tape running control means, a signal processing means for reading and processing data recorded on the magnetic tape, and a relative speed for detecting a relative speed during signal reproduction from the rotation control means and the tape running means. a detection means, a bit synchronization signal extraction means for obtaining phase synchronization with the reproduced signal and extracting a bit synchronization signal, a synchronization extraction control means for controlling the bit synchronization extraction means in accordance with the relative speed, and an extracted bit signal. and data reproducing means for supplying the signal to the signal processing means and reproducing the data, so that when reproduction is performed at an arbitrary speed, the flywheel effect in the loop of the phase locked loop is not lost. Further, a bit synchronization signal corresponding to the playback speed can be reliably extracted from the playback signal without deteriorating the removal effect of noise and out-of-band signals.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the overall configuration of a device according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing the configuration of essential parts of the device according to the embodiment, and FIG. FIG. 4 is a block diagram illustrating the overall configuration of the conventional device, and FIG. 5 is a circuit diagram showing the configuration of the main parts of the conventional device. 1.2...Magnetic head 3...Cylinder 4...Magnetic tape 5...KiV stand 6... ...Pinch roller 7...Tape kite 8...Cylinder rotation control circuit 9...
...Tape running control circuit 10...
Reproduction amplifier 11...... Equalization circuit 12...
...Comparator 13...Demodulation circuit 14...Error correction circuit 15...D/A converter 16.
20... Phase synchronized circuit 17... Phase comparator 18...
......Loop filter 19...
...Voltage controlled oscillator 21...
Relative speed detection circuit 22...Voltage control circuit 23...Voltage addition circuit 24
・・・・・・・・・・・・Take-up side reel Fig. 2 Fig. 3

Claims (1)

[Claims] (1) Cylinder rotation control means for controlling the rotation of a cylinder on which a set of magnetic heads is mounted, tape running control means for controlling the running of a magnetic tape, and reading and processing of data recorded on the magnetic tape. a signal processing means for
relative speed detection means for detecting the relative speed between the cylinder and the magnetic tape during data reproduction from the cylinder rotation control means and the tape running control means; and a bit for obtaining phase synchronization with the reproduced data and extracting a bit synchronization signal. synchronization signal extraction means; synchronization extraction control means for controlling the bit synchronization extraction means according to the relative speed; and data reproduction means for reproducing data by supplying the extracted bit synchronization signal to the signal processing means. A rotary head type digital tape recorder comprising: