JPS6173223A - Magnetic recorder and reproducing device - Google Patents

Abstract

PURPOSE:To suppress the unerased level of synchronizing and pilot signals in tracking a control signal, by recording signals for erasing having a fixed frequency at a level higher than that for other signals in recording areas for signals other than the pilot signals and synchronizing signals indicating the start of the tracking control signal areas. CONSTITUTION:A state where new tracking control signals are recorded by overwriting upon synchronizing signals f0' and the synchronizing signals f0' exist on signals for erasing fe as unerased signals and an example of the unerased level of the synchronizing signals f0 against the level of the signals for erasing fe are shown in the figure. It is necessary to set the detecting threshold (V+h) of the synchronizing signals f0, at least, >=0.3, in order to prevent wrong detection of the unerased signals. However, when the unerased level can be lowered to a -20dB level, the erroneous detection can be prevented, if the (V+h) is set at >=0.1, and thus, the margin of the detecting level can be enlarged. When the recording is made while the level of the signals for erasing is raised, the unerased level can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a rotary head type magnetic recording/reproducing device, and particularly to a tracking control device with improved reliability in detecting a tracking control signal.

[Background of the invention]

In a helical scan type magnetic recording/reproducing device using a rotating head, in order to make it smaller and lighter, in order to increase the recording density on the magnetic tape, the performance of related devices (tape, head, etc.) has been improved, and tracking control has been improved. One major issue is how to ensure reliability. This is because the tracks 111g on magnetic tapes are becoming increasingly narrow due to high-density recording, and it is difficult to accurately trace such narrow tracks with the head.
This is because it determines the quality of the entire device.

In conventional home VTRs, a tracking control method has been used in which a reference signal is recorded and reproduced on a control track provided at the end of a magnetic tape, and the phase of the reproduced signal on the magnetic tape is detected and controlled. . However, this method requires a control track on the magnetic tape and also requires a dedicated fixed head for extracting the control signal, which is not suitable for the purpose of making the device smaller and lighter. moreover,
The above method has the disadvantage that it is necessary to accurately set the relative positional relationship between the fixed head and the rotary head for the controlled drag, and it is very difficult to maintain compatibility between each device.

In order to improve the above problems, for example, JP-A-57-1
As shown in Japanese Patent No. 25525, a fixed frequency is recorded as a pilot signal as tracking control information on the entire track, and during playback, adjacent pilot signals of different frequencies are extracted as crosstalk.
There is a method of performing tracking control by detecting a beat component between this crosstalk signal. In this method, the main signal such as the video signal that should originally be recorded and the pilot signal are frequency-multiplexed and recorded, so there is no need for a control trunk or a dedicated fixed head for detecting it. No consideration is given to interference with the signal. In particular, when recording a digital signal such as a PCM signal as the main signal, the amplitude spectrum of the main signal ranges from approximately DC to rl1M.
It is thought that this may extend to the high frequency of H2, and the influence tIJ on the main signal cannot be avoided when frequency multiplexing the pilot signal is recorded.Therefore, as a tracking method that takes into account interference to the main signal as described above, For example, a Kel tracking control method has been proposed for a so-called overlap type POM recorder as disclosed in Japanese Patent Laid-Open No. 57-186227. In this method, PCM
In the area where the signal is recorded, the pilot signal is not subjected to fine frequency multiplexing recording, but instead the signals of the preamble and postamble portions of the PCM signal are used as tracking control signals. However, with this method, when trying to record a new PCM signal including a tracking control signal on a magnetic tape on which some signals have already been recorded, the unerased level of the previously recorded signal is It becomes a problem. This is because tracking control systems usually use crosstalk signals from adjacent tracks to detect tracking deviations. For this reason, it is common to use a relatively long wavelength (low frequency) signal with little azimuth loss effect as the pilot signal.

For long wavelength signals, the magnetic field reaches deep into the magnetic band on the magnetic tape, and if a relatively short wavelength signal is recorded on top of this signal, the long wavelength signal cannot be completely erased.

In such a tracking control method, a pilot signal and/or a synchronization signal for synchronizing the tracking control signal is recorded as a tracking control signal, and each tracking control signal area is completed using this signal as a reference and the adjacent tracks are Compare the viroft signal levels,
A tracking error has been detected. Therefore, in such a system, the most important issue is the detection of a reference pilot signal and/or synchronization signal.

However, the above-mentioned erased residue behaves as noise on the magnetic tape, lowering the detection level margin of the pilot signal and/or synchronization signal, which are the basis of the tracking control signal, and causing erroneous detection of the tracking control signal. [Objective of the Invention] In view of the problems of the prior art described above, an object of the present invention is to prevent erasure even when a new tracking control signal is recorded on an already recorded track. It is an object of the present invention to provide a magnetic recording/reproducing device which is capable of suppressing the residual level to a lower level and improving the detection level margin of a pilot signal and/or a synchronization signal serving as a reference for a tracking control signal.

[Summary of the invention]

In order to achieve the above object, the present invention has the following features: - In a tracking control signal recording area (tracking control signal area), pilot signals and tracking control signal processing are performed.
In the recording area other than the synchronization signal that indicates the start of the rear, an erasing signal with a certain frequency is recorded at a higher level than other signals, thereby lowering the erasing level of the already recorded signal. This is characterized by improving the detection level margin of the tracking control signal during playback.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail with reference to Examples.

Fig. 1 is a block diagram showing an embodiment of a rotary head type POM recorder to which the present invention is applied, Fig. 2 is a pattern diagram of tracks recorded by the device shown in Fig. 1, and Fig. 3 shows a reproduced output waveform. Figure 4 is a diagram of the recording pattern near the synchronization signal and its reproduced waveform when there is an erased residual, Figure 5 is a diagram showing the change in the erased residual level with respect to the recording level of the erased signal, and Figure 6 is the synchronizing signal FIG. 7 is a block diagram showing an embodiment of the recording amplifier according to the present invention, and FIG. 8 is a timing diagram showing the operation of FIG. 7.

In FIG. 1, the magnetic tape 1 is connected to the capstan motor 7.
The capstan motor 7 is controlled by a capstan servo circuit 9 and a rotation speed detector 8. The magnetic heads 2A and 2B have different azimuth angles and are mounted on the rotating cylinder 2C at an angle of about 180° to each other, and are driven by the rotating cylinder motor 4 to the rotating cylinder 20.
rotated with. The rotation of the rotary cylinder motor 4 is controlled at a constant speed by a rotary cylinder motor servo circuit 6 and a rotation speed detector 5. The rotary transformer 5 has a head 2A,
2B is connected to switch 10, and switch 10 is connected to 10A during recording and 10B1 during playback. The signal applied to the human input 'XX' 6 is subjected to processing such as an error detection and correction code, a synchronization signal, and an interleave by a POM recording system signal processing circuit P812, and is applied to the switching circuit 102. Further, the biloft signal generation circuit 13 generates tracking control signal frequencies kfoSf+ -fz, fb, and fe.

Here, fo·fl and fz are frequencies with a small azimuth loss effect, and f l)N fe is a frequency with a large azimuth loss effect. The behavior of each of these signals will be explained in detail later. The output of this pilot) If signal generation circuit 13 is inputted to the switching circuit 11, sorted in a predetermined order, and further outputted to the switching circuit 102.
Timing processing is performed with the output 12A of the OM recording system signal processing circuit. The recording signal 102A is then sent to the recording amplifier 101, and sent to the head via the switch 10. At this time, the recording amplifier 101 receives the timing signal 17K, and the number of grooves is controlled such that the peak value of fe is different from other signals by the time during which the erasing signal f8 is recorded.

On the other hand, the POM reproducing IJ circuit 14 performs error detection and correction on the signals reproduced from the heads 2A and 2B, performs processing such as deinterleaving, and outputs the reproduced signal to the output terminal 15. The tracking control device 18 extracts the pilot signal and the synchronization 1δ signal from the reproduced signal, and outputs an error signal in accordance with the tracking error. The capstan servo circuit 9 uses the daily output of this tracking control device, that is, the error signal, to control the capstan motor 7 during playback.
is controlled, thereby performing tracking control. The timing clock 17 is for generating and outputting a timing clock required for each part, and the capstan servo circuit 91
A frequency clock 170.17D equal to the motor rotation speed is sent to the rotating cylinder motor servo circuit 6. Further, a pilot signal generation circuit 16. Basic frequency clocks 17A and 17B are sent to the tracking control device 18 for generating control signals, respectively.

Figure 2 shows the tracking control signal area of the tape pattern on the magnetic tape 1 formed by the first device. In Figure 2, 19 indicates the track length of the tracking control signal area. These are the erasure signal f8 (24) and the synchronization signal f for sampling position detection.

(25), a blanking signal (26), and pilot signals f1 and f2 (27). These signals are
As shown in FIG. 2, the amount of tracking deviation between each track, that is, the time t converted into head running time is arranged and recorded.

Adjacent tracks are tracks (Ach+'g-ah) scanned by magnetic heads (2A, 2B) having mutually different azimuth angles. 20 is A-ah
The head node scan position, 21 indicates the scan direction, 22 indicates the tape running direction, and 23 indicates the position of the head where the tracking is ahead by 165''.

FIG. 3 is a diagram for explaining the principle of tracking control using output waveforms. Figure 3(a) shows the output waveform for the head position when the tracking error is 0°.
It is shown in correspondence with the figure.

First, the head that has advanced to point A begins to detect the adjacent fo, and at point B, detects its own track 10. then 0
At the point, the adjacent fa on the opposite side is detected.

On the other hand, the blanking signal fB is OD
A certain value is reproduced within the range of E. In this implementation sequence, the detection threshold (V+h) of the synchronization signal fo is set to detect the rising edge of f at point B, and when fB is detected thereafter, the pilot is placed at positions E and H. signal f2
Sampling position 1ffsP1 and SF to detect
3 to the E and H positions. That is, spl and SF
At the position No. 3, the levels of the 50-direction pilot signals f2 on opposite sides are compared, and this difference is determined as error No. 1. Therefore, as shown in No. 31N(a), the tracking error is 0°, that is, the error signal is 0 in the on-track state. On the other hand, as shown in No. 31J(b), when the tracking error is 135°, the level of the pilot signal at SP1 is 01SP2.
The level of the pilot number becomes 1, the error signal becomes 1, and the tracking control is activated. Detection of tracking errors above? IJ is performed in tracking control IJ path 18.

FIG. 4 shows a state in which a new tracking control signal is overwritten and recorded over the synchronization signals f and col described above, and this synchronization signal fa exists on the erasing signal f8 as an erased residue. There is. On the other hand, FIG. 5 shows an example of the remaining erasing level of the synchronizing signal fo with respect to the level of the erasing signal f9.

It can be seen from the figure that when the recording levels of Sfe and fn are the same, the erased residual of fo is -1QdB.

Now, as in the example in Figure 4, the erased residual signal fJ is the synchronization signal f
When the synchronizing signal fa exists prior to the head scanning position, the output waveform of the synchronizing signal fa with respect to the scan position of the head is as shown in FIG. In other words, assuming the worst case, a synchronization signal exists at a level of -10 (LB, that is, approximately 0.3 of the signal to be detected) in a place where no synchronization signal originally exists. In order to avoid erroneously detecting a signal due to the synchronization signal fo, it is necessary to set the detection threshold (V+h) of the synchronization signal fo to at least 03 or higher.However, if this cancellation risk is lowered to a level of -20 dE, It is sufficient to set the setting value to 01 or more, and the margin of the detection level will be expanded.In fact, as shown in Fig. 5, by raising the level of the erasing signal and recording, the unerased area can be eliminated. Figure 6 shows the synchronization signal level detection margin with the amount of tracking error plotted on the horizontal axis.The head width is set to 1.5 times the track pitch. If selected, the output of index No. 3 will be a constant value (1
0), but in the range of ±45° to ±180°, the output decreases as the error wind increases. On the other hand, ±13
With a tracking error of 5 degrees or more, adjacent index signals are detected, so the head output level eventually becomes diamond-shaped as shown in the figure. As mentioned in the section of Fig. 5, if the remaining erasing level is set to 0.3, the index detection level (v+h) must be set to 0.6 or higher, and the tracking error amount of ±1130° As shown in the figure, the upper limit of the detectable range of crosstalk from the μs track is 0.
It becomes 64. Therefore, in the same figure, 0.45410.
3, that is, the detection level margin is approximately 6.6 (iB
You can think about it. However, by applying the present invention,
If the residual erase level is suppressed and the lower limit of v+h is set to 0,1, the detection level margin is 0.64/Q,1,
That is, it is greatly improved to about 16 dE.

Is the configuration of the recording amplifier 101 shown in FIG. 7? FIG.

In the figure, 103 is the output signal 102 of the switching circuit 102.
TTL driver for amplifying the signal level of A, 104-1
06 is a resistor that sets the No. 1 level of the TTL driver output to a predetermined value, 107 is a switch that is switched by 17R (7) timing signal, 108 is a capacitance, 109 is a buffer amplifier, and 110 is a recording amplifier output. . 10
After the signal level of 2A is amplified by the TTL driver 103, the switch 10 is switched by the timing signal 17K of the erasing signal f8 of the tracking control signal, so that the level of only the area portion of the erasing signal changes,
The configuration is such that AC amplification is performed through a capacitance 10B and a buffer amplifier 109.

FIG. 8 shows the timing diagram of FIG. 7, and an output signal 110 is obtained in which only the area of the timing signal 17m is amplified compared to other areas.

〔Effect of the invention〕

As described above, by applying the present invention, it becomes possible to suppress the erasure residual level of the synchronization signal and pilot signal in the tracking control signal, thereby greatly reducing the detection level margin of the tracking control signal. Improvements are possible.

Although the above example shows only one type of signal arrangement, the present invention basically has the same effect on any type of pilot or index signal arrangement, and the above-mentioned method also applies to other arrangements. It goes without saying that the present invention is not limited to the embodiment described above, and that various configurations may be adopted without departing from the gist thereof.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of a rotary head type PCM recorder to which the present invention is applied, FIG. 2 is a diagram of a tracking control signal area in a track pattern, FIG. 3 is a diagram showing a reproduction output waveform, and FIG. The figure is a recording pattern near the synchronization signal and its reproduced waveform, Figure 5 is a diagram showing the remaining erasing level versus erasing signal recording level, Figure 6 is a diagram showing the synchronization signal detection level margin, and Figure 7 is a diagram showing the present invention. FIG. 8 is a timing diagram showing the operation of FIG. 7. FIG. 11...Signal switching circuit 13...Pilot signal generation circuit 18...Tracking control device 101/Recording amplifier 19...Tracking control signal area 24...Erasure signal 25/Synchronization signal fa 26...Blanking Signal fb 27... Pilot signals f1 and f2 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Bubble removal M signal light anchorage input (dB)

Claims (1)

[Claims] 1. A pilot signal or a pilot signal and a pilot signal to be recorded together with a main signal to be recorded in the longitudinal direction of a track formed at a predetermined angle on a magnetic tape by rotating heads having mutually different azimuth angles. having means for generating a tracking control signal such as a synchronization signal for detecting the position of the pilot signal and a signal of a constant frequency that is recorded in a tracking control signal recording area other than the recording area of the pilot signal and the synchronization signal; The tracking control signal is recorded in at least one predetermined area in the longitudinal direction of the track, and the peak value of the recording current of the signal of the certain frequency is different from the peak value of the recording current of the other signals. A magnetic recording/reproducing device characterized by setting and recording a value. 2. In the magnetic recording and reproducing apparatus according to claim 1, by recording a signal of a constant frequency in an area other than the area where the pilot signal and synchronization signal are recorded, the signal previously recorded on the tape is A magnetic recording/reproducing apparatus characterized in that recording is performed by setting a peak value of a recording current of the constant frequency signal so that an amount of unerased data is small enough for practical use. 3. In the magnetic recording/reproducing apparatus according to claim 1 or 2, there is provided a means for generating a timing for recording the signal of a certain frequency, and a recording amplifier for changing the output level by the timing generating means. 1. A magnetic recording and reproducing apparatus comprising: a recording level of the constant frequency signal;