JPH0458646B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a rotary head type digital signal recording/reproducing device, and in particular, to a device having rotating drums with different diameters, the recording format on each recorded magnetic tape is different. This invention relates to a rotating head PCM recorder which is made to be constant.

[Background of the invention]

Recently, the digitization of audio transmission signals has been rapidly progressing. Regarding tape recorders, a PCM recorder using a conventional VTR has been commercialized, and there is currently a desire for a smaller, audio-only helical scan digital signal recording and reproducing device.

FIG. 1 shows an example of a conventional helical scan type digital signal recording/reproducing apparatus. In Figure 1, 1 is an analog signal input terminal, 2 and 15
1 is a sample hold circuit, 3 and 14 are A/D converters and D/A converters, 4 and 13 are signal processing circuits, 5 is a recording amplifier, 6 is a recording signal output terminal, and 7
₁ is channel 1 recording/playback head, 7 ₂ is channel 2
8 is a rotating drum, 9 is a recording medium, 10 is a head playback output, 11 is a playback amplifier,
12 is a waveform equalization circuit, 16 is an analog signal output terminal, 17 is a reference signal generator, 18 is a clock generation circuit, 19 is an ATF signal generation circuit, 20 ₁ to 20 ₄
21 is a frequency divider circuit, 21 is a multiplexer, 22 is an adder circuit, 23 is a tack pulse, 24 is a position control circuit, 25 is an ATF regeneration control circuit, 26 is a tracking error signal, 27 is a capstan servo circuit,
28 is a capstan motor.

In FIG. 1, first, a recording and reproducing method for digital signals will be described. During recording, an analog signal input from an analog signal input terminal 1 is sampled by a sample/hold circuit 2, and converted into a PCM digital signal by an A/D converter 3.
Next, this PCM digital signal is subjected to error detection, addition of correction codes, synchronization signals, etc. in the signal processing circuit 4 of the recording system, is amplified by the recording amplifier 5, passes through the recording signal output terminal 6, and is rotated at a predetermined number of rotations. The data is recorded by the recording/reproducing head 7 attached to the rotating drum 8 on the recording medium 9 which is driven at a predetermined speed by the capstan motor 28.

During reproduction, the signal recorded on the recording medium 9 is reproduced by the recording/reproducing head 7, and after being amplified by the reproducing amplifier, the waveform equalization circuit 12 corrects the deterioration of the transmission characteristics occurring in the recording medium 9 and the recording/reproducing head 7. .
Next, error detection is performed by the reproduction system signal processing circuit 13.
After correction is made and converted into an analog signal by the D/A converter 14 and sampled by the sample hold circuit 15, the signal is output to the analog signal output terminal 16.
Output from. In addition, the sample hold circuit 2,
15, the A/D converter 3, the D/A converter 14, and the recording system and reproduction system signal processing circuits 4 and 13 are operated by the clock generation circuit 18 based on the reference clock obtained by the reference signal generator 17. It is operated by the generated clock.

There are several problems in making a digital signal recording/reproducing apparatus having such a configuration smaller in size and capable of recording over a long period of time. Among these, there is concern that tracking errors will increase due to narrower tracks.
This created a need for a highly accurate tracking control method.

As a tracking control method, conventional CTL
System and ATF used for 8mm video
(Automatic Track Finding) method.
The ATF method is likely to be adopted in the future because it has the following advantages over the CTL method: (1) it does not require a control track or head, (2) it does not require tracking adjustment, and (3) it is suitable for head servo.

The ATF method using a four-frequency pilot signal will be explained below with reference to FIGS. 1, 2, and 3. Second
The figure is an explanatory diagram of the operation of ATF, and FIG. 3 is a block diagram of the ATF regeneration system.

In FIGS. 2 and 3, ₇₁ is a channel 1 recording/reproducing head, 9 is a recording medium, 29 is a recording medium running direction, 30 is a head rotation direction, 31 is a channel 1 head recording pattern, and 32 is a channel 2 head recording. Pattern, 11 is a reproduction amplifier, 33 is a band pass filter, 34 is a mixer circuit, 35 is a band pass filter for _H , 36 is a band pass filter for 3 _H , 37 is a detection circuit for _H , 38 is a detection circuit for 3 _H , 39 is a differential amplifier, 40 is a gate, 41 is a modulated digital signal, 42 is a reproduced pilot signal ( ₁ to ₄ ), and 43 is a local pilot signal (F ₁ to F ₄ ).

As shown in FIG. 2, the recording medium 9 is driven in a recording medium running direction 29, and signals are recorded in a head rotation direction 30 by rotating recording/reproducing heads 7 ₁ and 7 ₂ . At this time, channel 1 recording/playback head 7
A channel ₁ head recording pattern ₃₁ and a channel 2 head recording pattern 32 are formed by recording alternately with the channel 1 and channel 2 recording/reproducing heads 72, and by making the recording azimuth angles different from each other. In addition, the recorded track width of each track is partially overwritten by the next recording/reproducing head 7 immediately after recording, so that it becomes substantially narrower than the track width of the recording/reproducing head 7. . Therefore, during reproduction, as shown in the figure, when the recording/reproducing head 7 tracks a desired track,
Crosstalk from both adjacent tracks will occur, but since the frequency band of the digital signal being recorded is high, this crosstalk is eliminated by azimuth loss.

The four-frequency pilot signal for ATF is superimposed and recorded on the digital signal in the order of ₁ , ₂ , ₃ , and ₄ for each recording pattern 31, 32. As for the value of each frequency, from the viewpoint of servo, it is best to set the frequency as high as possible, but conversely it must not affect the digital signal spectrum. 8mm
In the VTR example, if the horizontal synchronization signal frequency is _H , then ₁ ≒ 6.5 _H , ₂ ≒ 7.5 _H , ₃ ≒ 10.5 _H , ₄ ≒ 9
_.5H
It is located in a low frequency band that is not affected by the above-mentioned azimuth loss.

In FIG. 1, a reference clock generated by a reference signal generator 17 is input to an ATF signal generation circuit 19. The ATF signal generation circuit 19 is composed of four frequency dividing circuits 20 ₁ to 20 ₄ with different frequency division ratios and a multiplexer 21, and generates a four-frequency pilot signal and also generates a tack pulse 23 synchronized with the rotation period of the rotary drum 8. The multiplexer 21 is switched depending on the output state of the controlled position control circuit 24, and the four-frequency pilot signals are sequentially sent to the adder circuit 22. The addition circuit 22 is
This pilot signal is superimposed on the digital signal to be recorded.

During reproduction, the output of the recording/reproducing head 7 is amplified by the preamplifier 11 and input to the ATF reproduction control circuit 25. As shown in FIG. 3, in the ATF regeneration control circuit 25, this digital signal 41 is first inputted to the bandpass filter 33, and the digital signal 41 is input to the bandpass filter 33.
The regenerated pilot signal 42 ( ₁ to
₄ ) Extract. Next, by the mixer circuit 34,
A reproduction pilot signal 42 ( ₁ to ₄ ) and a local pilot signal 43 having the same frequency as the pilot signal of the track to be scanned by the recording and reproduction head 7.
(F ₁ to F ₄ ) and a difference frequency signal is output. For example, as _shown in FIG.
When tracking, the track width of channel 1 recording/playback head ₇₁ becomes channel 1 recording pattern 3.
1, the reproduced pilot signal 42 includes not only ₃ but also adjacent tracks ₂ and 42.
₄ will also be played. Therefore, the output of the mixer circuit 34 is | ₃ − ₄ |≒ _H , | ₂ − ₃ |
≒
It becomes two frequency components of _3H .

The _H component and 3 _H component in the output signal of this mixer circuit 34 are filtered through respective band pass filters 35,
36, and both band pass filters 35,
Balance adjustment is performed so that the amplitudes of the _H component, which is the output component of 36, and the 3 _H component are equal.

The detectors 37 and 38 are bandpass filters 3
The envelopes of the _H component and the 3 _H component, which are the output signals of 5 and 36, are respectively detected and input to the differential amplifier 39. Further, if the recording/reproducing head 7 currently scanning the output of the differential amplifier 39 is the channel 1 recording/reproducing head ₇₁ , it will be 3 _H - _H , and if it is the channel 2 recording/reproducing head ₇₂ , it will be _H - 3 _H. Once determined, the direction of tracking deviation can be determined.
The gate 40 is actuated by the tracking pulse 23, switches between the two outputs, ie, _3H - _H and _H - _3H , and sends a tracking error signal 26 to the capstan servo circuit 27 at the subsequent stage.

For example, in FIG. 2, if _the channel 1 recording/reproducing head ₇₁ is shifted in the recording medium traveling direction 29 (toward the _right in the figure), the _H component increases,
Also, since the gate 40 is open to the _3H − _H side,
The tracking error signal 26 becomes a positive voltage, and the rotation speed of the capstan motor 28 may be lowered so that this potential becomes zero. Further, if the channel 2 recording/reproducing head ₇₂ scans the track containing the reproduction pilot signal ₂ and also deviates in the recording medium running direction 29, | ₁ − ₂ | _≈H component increases, and the gate 40 becomes _H − 3 Since it is open to _{the H} side, the tracking error signal 26 becomes a positive voltage and works to lower the rotation speed of the capstan motor 28.

FIG. 4 shows the reproduced signal frequency spectrum when ATF is used. Assuming that the sampling frequency s and the number of quantization bits of the digital signal recording and reproducing device are the same as those of compact discs currently in practical use, s = 44.1KHz, 16-bit quantization, and this digital signal is compressed in the time axis and converted into digital FM. When recorded, the transmission rate is approximately 5.5MHz, resulting in the spectrum shown by the solid line in FIG.

As can be seen from FIG. 4, the ATF pilot signal increases the low-frequency components compared to the digital signal, so it may result in a slight deterioration of the error rate. Therefore, the recording level is set at -20 dB with respect to the peak level of the digital signal.

By the way, in such a digital signal recording/reproducing device, various variations are possible, such as reducing the diameter of the rotating drum 8 in order to make it more compact, or increasing the diameter of the rotating drum 8 in response to higher quality. I can take Yon. However, since the diameter of the rotating drum 8 is different, the signal format and recording wavelength on the recording medium 9 are different depending on each device, resulting in a major drawback of incompatibility.

[Purpose of the invention]

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, to provide a rotating head that always maintains the same recording format and recording wavelength on the recording medium regardless of the difference in the diameter of the rotating drum, and that ensures compatibility between each device.
Provides PCM recorder.

[Summary of the invention]

In each device, by setting the product of the rotating drum diameter and the wrapping angle of the recording medium to a constant value, the recording track length is set to a constant value, and the recording signal clock and ATF servo signal frequency are variable controlled in accordance with the rotating drum diameter. However, the recording format and recording wavelength on the recording medium are kept constant.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 5 is a plan view showing an embodiment of the present invention, in which figure a shows a small-sized compatible machine and figure b shows a standard machine. In FIG. 5, 8 is a rotating drum, 9 is a recording medium, 44 is a wrapping angle, 45 is a rotating drum diameter, 4
6 is a pull-out pin, and 47 is a cassette half.

In the present invention, the recording formats on the tapes are made the same in order to ensure compatibility between the tapes recorded by both machines. Therefore, if the rotational speed N of the rotating drum 8 and the feed speed Vt of the recording medium 9 are the same, the recording track length L can be determined by the rotating drum diameter 45 and the wrapping angle 44.

If the rotating drum diameter 45 is φ and the wrapping angle 44 is θ°, the recording track length L can be expressed by equation (1).

L=π・φ・θ/360...(1) In other words, to keep the recording track length L constant,
It is sufficient if φ and θ are constant. For example, if the rotating drum diameter 45 of the small compatible machine in figure a is φ=20
mm, the wrapping angle 44 is θ = 135°, the rotating drum diameter 45 of the standard machine in figure b is φ = 30 mm, and the wrapping angle 44 is θ
If =90° is selected, the recording track length L will be the same as 23.55 mm.

Here, the rotational speed N of the rotating drum 8 is the same for both machines, and the amount of information to be recorded in one recording track length is also the same, so the miniaturized machine shown in figure a has a smaller size than the standard machine shown in figure b. Recording signal clock 90°/135° = 2
/3, the signal recording wavelength on the recording medium 9 becomes the same.

At this time, the signal spectrum shown in Figure 4 is
As the frequency shifts to lower frequencies as shown by the broken line, the ATF signal frequency must be lowered to prevent the error rate from worsening. As with the transmission rate mentioned above, this frequency is 2/3 of the standard device in figure b.
If this is selected, the recording wavelength of the ATF signal on the recording medium 9 will also be the same.

In order to realize the above-mentioned compact compatible machine, in the circuit configuration shown in FIG.
3, and the frequency division ratios of the frequency division circuits 20 ₁ to 20 ₄ in the ATF signal generation circuit 19 may be selected to be a ratio of 45 to the diameter of the rotating drum.

The above description has been made regarding a downsized machine with a small rotating drum diameter 45, but a mechanism with a large rotating drum diameter 45 can also be realized using a similar method.

[Effect of idea]

According to the present invention, the recording format and recording wavelength on the recording medium are recorded at a constant level regardless of the difference in the diameter of the rotating drum, so that it can be reproduced by any device, and its compatibility can be significantly improved. can.

[Brief explanation of drawings]

Figure 1 is a block diagram of a conventional helical scan digital signal recording and reproducing device, and Figure 2 is a block diagram of a conventional helical scan type digital signal recording and reproducing device.
FIG. 3 is a block diagram of an ATF regeneration system, FIG. 4 is a reproduction signal frequency spectrum diagram when ATF is used, and FIG. 5 is a plan view showing an embodiment of the present invention. 4... Signal processing circuit (recording), 7... Recording and reproducing head, 17... Reference signal generator, 19...
ATF signal generation circuit, 20 ₁ to 20 ₄ ... frequency dividing circuit,
21... Multiplexer, 22... Addition circuit, 2
3... Tack pulse, 24... Position control circuit, 2
5...ATF regeneration control circuit, 26...Tracking error signal, 27...Capstan servo circuit,
28...Capstan motor, 33...Band pass filter, 34...Mixer circuit, 35... _H band pass filter, 36...3 _H band pass filter, 39...Differential amplifier, 40... Gate, 42... Reproduction pilot signal, 43... Local pilot signal, 44... Wrapping angle, 45...
Rotating drum diameter, 46... Pull-out pin, 47...
...cassette half.

Claims (1)

[Claims] 1. A recording signal processing circuit that compresses at least a time axis, a rotating drum to which a recording/reproducing head for recording and reproducing the output of the recording signal processing circuit on a recording medium is fixed, and a reproduction signal that expands the time axis during reproduction. a processing circuit; and a servo signal generator for generating a tracking servo signal to be recorded on the recording medium; In a digital signal recording and reproducing apparatus configured such that the recording track length formed on a recording medium is constant, the transmission clock of the recording and reproduction signal processing circuit and the tracking servo signal are adjusted in accordance with the wrapping angle. Make the frequency variable,
A rotary head PCM recorder characterized in that the recording wavelength on the recording medium is kept constant.