JPS6390048A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To execute stable tracking by detecting the frequency components of 16kHz and 46kHz respectively by envelope detectors and controlling the gain of a voltage controlled gain variable amplifier with a voltage level obtained by adding respectively detected values. CONSTITUTION:An output of a switch 18 is applied to the voltage controlled gain variable amplifier 23 and the output of the amplifier 23 is outputted to a tracking error signal output terminal 20. On the other hand, 16kHz, 46kHz frequency components are envelope-detected by respective detectors 14, 15, the outputs of the detectors 14, 15 are applied to a subtractor 16 and an adder 21 and the output of the adder 21 is applied to the amplifier 23 as a control signal through an LPF 22. Although the output level of the adder 21 is a constant when a magnetic head 8 exists in the vicinity of the center of a video track, the level is increased in accordance with a shifted value from the center when the shifted value exceeds a fixed value. Thereby when the head exists in the vicinity of the center of the video track, stable tracking can be executed, and when the head 8 is shifted from the center by the fixed value or more, quick tracking lead-in is executed.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a rotary head type magnetic recording system that controls the running of a magnetic tape using a pilot signal recorded on a video signal track superimposed on a video signal. Playback device (hereinafter referred to as V
(referred to as TR), it is particularly designed to quickly perform phase synchronization pull-in of a tracking control system.

[Conventional technology]

FIG. 3 is a schematic block diagram showing the configuration of a conventional VTR that performs tracking control using pilot signals.

First, the configuration of a tracking control means of a conventional VTR will be explained with reference to FIG. In this figure 3,
The magnetic head 8 is provided on a rotating head drum (not shown). The magnetic head 8 rotates with the rotation of the head drum, and diagonally scans a magnetic tape (not shown).

A head switch signal representing the switching timing of the rotating magnetic head inputted to the head switch signal input terminal 1 is applied to the cyclic frequency generator 2 and the switch 18.

The cyclic frequency generator 2 sequentially generates pilot signals in response to the leading and trailing edges of the head switch signal described above.

During recording, a video signal is input to the video signal input terminal 4,
After being superimposed with the above-mentioned pilot signal, it is amplified via the recording amplifier 5.

Further, the changeover switch 6 is connected to the REC side, and the output of the recording amplifier 5 is supplied to the magnetic head 8 via the rotary transformer 7 and recorded on the magnetic tape.

On the other hand, during playback, the selector switch 6 is switched to the PLAY side, and the video signal including the pilot signal read by the magnetic head 8 is input to the reproducing amplifier 9 via the rotary transformer 7 and the selector switch 6. and amplified.

The output of the regenerative amplifier 9 is given to a low-pass filter 1o, and a pilot signal component is extracted from the regenerated signal.

This pilot signal component and the aforementioned pilot signal that is sequentially generated by the circulating frequency generator 2 during reproduction (hereinafter, during reproduction, it is called a carrier signal and its frequency is referred to as fcR)
is input to the mixer 11, and a signal component having a frequency corresponding to the frequency difference between both signals is output.

The output of mixer 11 is simultaneously filtered by bandpass filter 12, which has a passband of 16 KHz! = 46kHz
(Given to the bandpass filter 13 having a D passband.

The signal that has passed through the bandpass filter 12 is sent to a detector 14
Envelope detection is performed at , and its output is given to subtracter 16 .

On the other hand, the signal that has passed through the bandpass filter 13 is subjected to envelope detection by a detector 15, and its output is also detected by a subtracter 16.
given to.

The output of the subtracter 16 is input to the amplifier 19 as a signal of the same polarity (by a switch 18 which is switched in response to the head switch signal) or as a signal of opposite polarity via an inverting amplifier 17. The output of the amplifier 19 is amplified and outputted to the tracking error signal output terminal 20.

FIG. 4 is a diagram showing video tracks formed obliquely in the longitudinal direction on the magnetic tape 30 and a pilot signal recorded on each video track in a manner superimposed on a video signal.

Next, referring to FIG. 4, the operation of the tracking control means of the VTR shown in FIG. 3 will be explained.

□ During recording, the cyclic frequency generator 2 generates four different frequencies fs in response to the leading and trailing edges of the head switch signal.
, ft, fa, and f+ pilot signals are generated by switching each field.

These four frequencies are, for example, f=102 KHz when recording an NTSC video signal.

f2=118 KHz, f,=164 KHz
, f, = 148 KHz, so that the frequency difference α between f, and f is equal to the frequency difference between f4 and f3, and the frequency difference between f4 and f is almost twice α. The values are set to be close to each other.

These pilot signals are superimposed on the video signal, and as shown in FIG. 4, are recorded by the magnetic head 8 on the magnetic tape 30 by forming video tracks that are inclined in the longitudinal direction of the magnetic tape 30 as fields.

In FIG. 4, the video track FI) Fl e Fs
+F4 indicates that pilot signals of frequencies fw, ft-fs, and f4 are recorded, respectively.

During reproduction, the magnetic head 8 reads a signal from the video track on the magnetic tape 3o, and the reproduced signal is input to the reproduction amplifier 9 via the rotary transformer 7 and the changeover switch 6, and is amplified.

The output of the regenerative amplifier 9 is given to a low-pass filter 10, and the pilot signal component contained in the regenerated signal is extracted.

For example, if the magnetic head 8 is tracking the video track Fl on the magnetic tape 30 as shown in the fourth IA, the pilot signal component detected by the magnetic head 8 includes the video track Fl.
In addition to the pilot signal of frequency f1 that is superimposed on F1, side lead effects, crosstalk, etc. may occur on both adjacent video tracks (in the example shown in FIG. 4, video tracks F,
and the pilot signal superimposed on the video track (F4). The magnitude of the pilot signals detected from these adjacent video tracks increases as the amount of positional deviation of the magnetic head 8 from the center of the video track being tracked increases.

When tracking the video track F, the above-mentioned pilot signal component extracted by the low-pass filter 10 and the frequency fcR generated by the cyclic frequency generator 2
The carrier signal fl is input to the mixer 11, and the frequency fz of the pilot signal of one adjacent video track F2 is input to the mixer 11.
= 118 KHz and carrier signal frequency FOR=
f, = 102 KHz, and the difference between the frequency of the pilot signal of the other instantaneous video track F4, f, = 148 KHz, and the frequency of the carrier signal, fcR = F, = 102 KH3. 46
A signal component having a frequency of KHz is obtained.

These 16 KHz and 46 KHz signal components are further extracted separately by a band pass filter 12 having a pass band of 16 KHz and a band pass filter 13 having a pass band of 46 KHz.

The output of the bandpass filter 12 is subjected to envelope detection by a wave detector 14, and the output level represents the amount of positional deviation of the magnetic head 8 to the adjacent video track F on the right side.

On the other hand, the output of the bandpass filter 13 is subjected to envelope detection by the wave detector 15, and the output level represents the amount of positional shift of the magnetic head 8 to the adjacent video track F4 on the left side.

By passing both of these outputs through the subtracter 16, the amount of positional deviation of the magnetic head 8 from the center of the video track F can be obtained.

Then, the magnetic head 8 is on video track F1 or F3.
When tracking video track F or F4, the frequency difference between the left and right adjacent video tracks is reversed, so
The output of the subtractor 16 will be of opposite polarity.

Therefore, an inverting amplifier 17 is provided to invert the polarity.
By switching the switch 18 using a head switch signal, the magnetic head 8 is switched to the video track F2 or F.
When tracking 4, it is necessary to invert the polarity of the output of the subtracter 16.

The output of switch 18 is amplified in amplifier 19.

In this way, the tracking error signal output terminal 20
A signal having a voltage corresponding to the amount of positional deviation of the above-mentioned magnetic head 8 from the center of the video track is outputted.
This signal is fed back to the capstan motor to form a control system and achieve good tracking.

[Problem that the invention seeks to solve]

However, in order to perform stable tracking control, it is necessary to consider disturbance suppression characteristics while the control system is synchronized, and the loop dyne of the servo control system cannot be made too high. There was a problem in that tracking synchronization could not be performed quickly in the following cases.

The present invention was made to solve these problems, and an object of the present invention is to provide a magnetic recording and reproducing device that can stably perform tracking control in a steady state and quickly perform tracking control in a transient state. shall be.

[Means for solving problems]

The magnetic recording and reproducing device according to the present invention, before reproducing,
Outputs from two detectors that perform envelope detection of 16 KHz 6 minutes and 46 KHz 8 minutes from the frequency components obtained by mixing the pilot signal and carrier signal, respectively, and a re-detector are added, and the output is calculated according to this added output. An adder is provided to vary the amplification degree of the voltage-controlled variable gain amplifier of the tracking error signal.

[For production]

In this invention, the 16 KHz component and the 46 KHz component
The components are detected by two detectors, and the outputs of the detectors are added together by an adder to vary the amplification degree of the voltage-controlled variable gain amplifier. The gain of the servo control system increases proportionally,
Tracking pull-in is done quickly, and the F of the magnetic head is
If the amount of deviation from the rack center is within a certain range, the gain of the sensor control system is kept at the normal gain, and stable tracking is achieved.

〔Example〕

Embodiments of the magnetic recording/reproducing apparatus of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic block diagram showing the configuration of one embodiment. The embodiment shown in FIG. 1 is the same as the conventional VTR tracking control means shown in FIG. 3 except for the following points.

That is, the output of the switch 18 is applied to the voltage-controlled variable gain amplifier 23 instead of being applied to the amplifier 19, and the output of the voltage-controlled variable gain amplifier 23 is output to the tracking error signal output terminal 20.

Furthermore, the outputs of the detector 14 and the detector 15 are output to a subtracter 16.
It is also provided to the newly provided adder 21. The output of adder 21 is sent to low-pass filter 2
2, and then input to the voltage controlled variable gain amplifier 23 as a control signal.

FIG. 2 is a waveform diagram for explaining the operation of the embodiment shown in FIG. 1. 2nd FXJ (a) is a diagram showing the video track tracked by the magnetic head 8 and the output level of the detector 14 that performs envelope detection of the 16 KHz frequency component obtained corresponding to the video track.
1 is a diagram showing the output level of the detector 15 that performs envelope detection on a frequency component of 46 KHz.

Further, 2nd PI (c) is a diagram showing the output level of the adder 21 which is the sum of the outputs of the detector 14 and the detector 15, and 21N (d) is a diagram showing the output level of the adder 21 which is the sum of the outputs of the detector 14 and the detector 15.
5 is a diagram showing the output level of the subtracter 16 after subtracting the output of 5. FIG.

Furthermore, FIG. 2(e) is a diagram showing the output level of the voltage-controlled variable gain amplifier 23 which amplifies the output of the subtracter 16.

In FIG. 2(e), the solid line represents the output level of the voltage-controlled variable gain amplifier 23, and the broken line represents the output level of the conventional constant gain amplifier 19 for comparison.

Note that in FIGS. 2(a) to 2(e), the horizontal axis represents the distance in the track width direction of the magnetic tape.

Now, assume a period in which the carrier signal has a frequency f, = 102 KHz. As shown in FIG. 4, when tracking near the video track F1 on which the pilot signal of frequency f1 is superimposed, the magnetic head 8 moves from the center of the video track F to the video track F.

The frequency f2 from video track F2 increases as it shifts toward
= The reproduction level of the pilot signal of 118 KHz increases, the signal component of the frequency difference of 16 KHz increases, the output level of the detector 14 increases, and conversely, the reproduction level of the pilot signal of the video track F increases.
, the reproduction level of the pilot signal of frequency f4=148 KHz from , decreases, the signal component of the frequency difference of 46 KHz decreases, and the output level of the f-detector 15 decreases.

Similarly, as the magnetic head 8 shifts from the center of the video track F1 toward the video track F4, the output level of the detector 14 decreases and the output level of the detector 15 increases.

At this time, the output level of the adder 21, which is the sum of the outputs of the wave detectors 14 and 15, is constant when the magnetic head 8 is near the center of the video track Fl, and when the amount of deviation from the center exceeds a certain level. Then, it becomes larger depending on the amount of deviation.

The output of this adder 21 is input as a control signal to a voltage controlled variable gain amplifier 23 via a low pass filter 22. The gain of the voltage controlled variable gain amplifier 23 is set to be directly proportional to the voltage level of the control signal.

As shown in FIG. 2 (e), when the magnetic head 8 is located near the center of the video rack F1, the same tracking error signal as in the case of the constant gain amplifier shown by the broken line is obtained, but the magnetic head 8 When the amount of deviation from the center of video track F exceeds a certain level, a tracking error signal is obtained in which the loop dyne of the servo control system increases as the amount of deviation increases, compared to the case of an amplifier with a constant gain, as shown by the broken line. .

Therefore, when the magnetic head 8 is near the center of the video track F1, stable tracking is performed as in the conventional case, and when the magnetic head 8 is deviated from the center of the video track F1 by a certain amount or more, quick tracking is performed. will be carried out.

In the above description, a VTR has been described, but the present invention is also effective for other information signal storage devices, such as digital audio signal magnetic recording and reproducing devices.

〔Effect of the invention〕

As explained above, this invention is applicable to 16 KHz and 46 KHz.
Since each Hz frequency component is envelope-detected and the added voltage level is used to control the gain of the stain pressure control variable gain amplifier, the control system loop is The loop dyne of the control system is lower than the normal gain when the magnetic head is near the center of the track. tracking is performed stably.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram showing the configuration of an embodiment of the magnetic recording/reproducing apparatus of the present invention, FIG. 2 is a waveform diagram for explaining the operation of the embodiment shown in FIG. 1, and FIG. is a VT that performs tracking control using conventional pilot signals.
FIG. 4, a schematic block diagram showing the configuration of R, is a diagram showing a video track formed on a magnetic tape and a magnetic head. 2... Circulating frequency generator, 7... Rotor IJ) lance, 8... Magnetic head, 9... Regenerative amplifier, 10
．． 22...Low pass filter, 11...Mixer, 1
2.13...Band pass filter, 14.15...
Detector, 21... Adder, 23... Voltage control variable gain amplifier, 30... Magnetic tape. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (2)

[Claims] (1) A magnetic tape in which a plurality of pilot signals having different frequencies are repeatedly recorded in each signal track is played back by a rotating magnetic head, and the running of the magnetic tape is controlled based on the extracted pilot signals. In the recording and reproducing apparatus, a signal generating means for sequentially and repeatedly generating a plurality of signals each having the same frequency as the pilot signal in synchronization with a signal indicating switching of the rotating magnetic head; first and second level detection means for comparing the frequencies of a plurality of generated signals and the extracted pilot signal and detecting the level of a signal component responsive to the difference between the frequencies; a subtracting means for subtracting the output of the second level detecting means, an adding means for adding the outputs of the first and second level detecting means, and a gain of the tape running control system is controlled according to the output level of the adding means. 1. A magnetic recording and reproducing device comprising: gain control means. (2) Magnetic recording according to claim 1, characterized in that the gain control means is variable gain amplification means that amplifies the output of the subtraction means and controls it so that it is directly proportional to the output level of the addition means. playback device.