JPH05314593A - Automatic tracking system in magnetic recording and reproducing device - Google Patents

Abstract

(57) [Abstract] [Purpose] It is not necessary to use two bandpass filters and two detectors to create a tracking error signal, and the circuit configuration is simplified. [Structure] An auto-tracking system that uses a beat signal between a reference pilot signal of a traveling track and a pilot signal of an adjacent track. To extract the beat signal used for auto-tracking, one bandpass filter 6a and a detector 7a are connected to the next stage of the balanced modulator 5.
Only the beat signal with the pilot signal of the adjacent track of only one of the adjacent tracks on both sides of the traveling track is taken out, and the level of the beat signal is updated and stored in the memory 22. The tracking error signal is generated based on the magnitude comparison between the level and the level of the previous beat signal stored.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic tracking system in a magnetic recording / reproducing apparatus such as a VTR.

[0002]

2. Description of the Related Art In a magnetic recording / reproducing apparatus for recording and reproducing a signal on a magnetic tape by a rotary head,
As a method to perform tracking by automatically adjusting the tape traveling speed so that the head travels on the reproducing track during reproduction, an automatic track finding (tracking pilot signal (TPS) is recorded in multiple recording with the main signal during recording. There is a method of ATF).

FIG. 3 shows a recording pattern of a pilot signal by a rotary head which is usually used in a VTR. Pilot signals of four types of frequencies f ₁ , f ₂ , f ₃ , and f ₄ are used. Each frequency f ₁ , f ₂ , f ₃ ,
f ₄ is the horizontal frequency of the NTSC video signal f _H
(= 15.734 kHz), and is defined as follows (see FIG. 4).

F ₁ = 6.5f _H f ₂ = 7.5f _H f ₃ = 10.5f _H f ₄ = 9.5f _H These four types of pilot signals are f _{1 as} shown in the figure.
The data is cyclically switched and recorded in the order of → f ₂ → f ₃ → f ₄ → f ₁ . Pilot signal frequency difference of the adjacent tracks, f in the f ₁ and f _{2 H,} 3f _H between f ₂ and f _3, f ₃ and f ₄ and at f _H, 3f in the f ₄ and f _{1 H}
Is. That is, the frequency difference between adjacent tracks is f _H →
3f _H → f _H → 3f _H are alternately repeated.

FIG. 2 is a block diagram showing an electrical structure of an auto-tracking system in a conventional VTR.

In the figure, 1a and 1b are a pair of rotary heads (recording / playback heads) provided 180 ° apart on a rotary cylinder, 2 is a head amplifier having a head switching section,
3 is a bandpass filter (or a lowpass filter may be used) for extracting pilot signals of frequencies f ₁ , f ₂ , f ₃ , and f ₄ from the reproduced signal, 4 is a reference pilot signal generator, and 5 is a balanced modulator (BM). ), 6a is a first bandpass filter having a center frequency of f _H (16 kHz),
6b is a second bandpass filter having a center frequency of 3f _H (46 kHz), 7a is a first detector, 7b is a second detector, 8 is a differential amplifier, 9 is a polarity inverter, and 10 is a changeover switch. , 11 are timing switching signal generators. The portion enclosed by the broken line may be replaced with software for a capstan motor.

Next, the operation will be described.

At the time of reproduction, the signals recorded on the magnetic tape are read by the heads 1a and 1b. The signals read by both heads 1a and 1b are alternately switched by the head switching pulse from the timing switching signal generator 11 to become a continuous signal, which is input to the head amplifier 2 and amplified. Bandpass filter 3
Extracts only the pilot signal component from the amplified reproduction signal and inputs it to the balanced modulator 5. The reference pilot signal generator 4 generates a reference pilot signal having the same frequency as that of the track on which the head 1a or 1b is currently traveling, and inputs it to the balanced modulator 5. The balanced modulator 5 receives the pilot signal and the reference pilot signal and generates a beat signal.

[1] When Running on Track A ₀ For example, it is assumed that the head is currently running on track A ₀ in FIG. At this time, the frequency of the beat signal with the immediately preceding adjacent track D ₋₁ is 3f _H , and the frequency of the beat signal with the immediately following adjacent track B ₀ is f _H. When the head is traveling on the track A ₀ , the timing switching signal generator 11 outputs a polarity switching pulse for switching the switching switch 10 to the polarity reversing device 9 side.

When the tape running speed is slow When the running speed of the magnetic tape becomes a little slower, the running of the head is biased toward the preceding adjacent track D ₋₁ .
Then, the output from the balanced modulator 5 is the beat signal component 3f _H of the traveling track A ₀ (pilot signal f ₁ ) and the immediately preceding adjacent track D _-1 (pilot signal f ₄ ).
Will increase. Beat signal component f _H between the traveling track A ₀ and the next adjacent track B ₀ (pilot signal f ₂ ).
Is very few.

Therefore, in the first bandpass filter 6a (center frequency f _H ) and the second bandpass filter 6b (center frequency 3f _H ) in the next stage of the balanced modulator 5, the first bandpass filter is used. The beat signal component extracted by 6a is small, and the beat signal component extracted by the second bandpass filter 6b is large. That is, the level of the detection signal by the second detector 7b is higher than the level of the detection signal by the first detector 7a. At this time, the output of the differential amplifier 8 shifts to the negative side.

By the way, since the change-over switch 10 is changed over to the polarity reversing device 9, the tracking error signal output to the capstan motor servo circuit is shifted to the plus side to increase the running speed of the tape. By the feedback control, automatic tracking is performed on the traveling track A ₀ so that the tracking error signal is always at the same level.

On the contrary to the above, when the tape running speed is fast, when the running speed of the magnetic tape becomes a little faster, the running of the head is biased toward the next adjacent track B ₀ , and the balance modulator 5 outputs As the output, the beat signal component f _H between the traveling track A ₀ (pilot signal f ₁ ) and the next adjacent track B ₀ (pilot signal f ₂ ) increases. The beat signal component 3f _H between the traveling track A ₀ and the immediately preceding adjacent track D _-1 (pilot signal f ₄ ) is extremely small.

At this time, the first bandpass filter 6a
Many beat signal components are extracted at (center frequency f _H ), and the second bandpass filter 6 b (center frequency 3
The beat signal component extracted at f _H ) becomes small, and the second
The level of the detection signal by the first detector 7a is higher than the level of the detection signal by the detector 7b. At this time, the output from the differential amplifier 8 shifts to the positive side,
This is reversed by the polarity reversing device 9, and the tracking error signal output to the capstan motor servo circuit is shifted to the minus side, the tape traveling speed is reduced, and the automatic tracking for the traveling track A ₀ is performed.

As described above, when the head is traveling on the track A ₀ , the beat signal component f _H becomes a signal indicating that the tape traveling speed is high, and the beat signal component 3 f _H
Is a signal indicating that the tape running speed is slow.

[0016] [2] when the running time of the head of the track B ₀ is traveling track B ₀ in FIG. 3, the previous frequency of the beat signal of the adjacent track A ₀ is f _H, and the one behind The frequency of the beat signal with the adjacent track C ₀ is 3f _H. When the head is traveling on the track B ₀ , the timing switching signal generator 11 outputs a polarity switching pulse for switching the switching switch 10 to the differential amplifier 8 side.

When the tape running speed is slow When the running speed of the magnetic tape becomes a little slower, the running of the head is biased toward the preceding adjacent track A ₀ ,
In the balanced modulator 5, the beat signal component f _H between the traveling track B ₀ (pilot signal f ₂ ) and the immediately preceding adjacent track A ₀ (pilot signal f ₁ ) increases. Therefore, the beat signal component extracted by the first bandpass filter 6a (center frequency f _H ) is large, and the beat signal component extracted by the second bandpass filter 6b (center frequency 3f _H ) is small. The level of the detection signal by the first detector 7a is higher than the level of the detection signal by the second detector 7b.

At this time, the output from the differential amplifier 8 is shifted to the plus side, and this is output to the capstan motor servo circuit as a tracking error signal which is shifted to the plus side as it is without passing through the polarity inverter 9.
The running speed of the tape is increased and auto-tracking is performed on the running track A ₀ .

On the contrary to the above, when the tape running speed is fast, when the running speed of the magnetic tape becomes a little faster, the running of the head is biased toward the next adjacent track C ₀ , and the balance modulator 5 outputs As the output, the beat signal component 3f _H between the traveling track B ₀ (pilot signal f ₂ ) and the next adjacent track C ₀ (pilot signal f ₃ ) increases. Therefore, the beat signal component extracted by the first bandpass filter 6a (center frequency f _H ) is small, and the beat signal component extracted by the second bandpass filter 6b (center frequency 3f _H ) is large. The level of the detection signal by the second detector 7b is higher than the level of the detection signal by the first detector 7a.

At this time, the output of the differential amplifier 8 is shifted to the minus side, and the tracking error signal which is also shifted to the minus side is output to the capstan motor servo circuit. As a result, the tape traveling speed is reduced and the tape is traveling. Automatic tracking is performed on the track A ₀ .

As described above, when the head is traveling on the track B ₀ , contrary to the case of the traveling track A ₀ ,
The beat signal component f _H is a signal indicating that the tape traveling speed is slow, and the beat signal component 3f _H is a signal indicating that the tape traveling speed is high.

When traveling on the track C ₀ , it is the same as the traveling track A _0, and when traveling on the track D ₀ , it is the same as the traveling track B ₀ . In summary, the traveling track beat signal component f _H beat signal component 3f _H A ₀ Fast Slow B ₀ Slow Fast C ₀ Fast Slow D ₀ Slow Fast.

[0023]

In the conventional auto-tracking system of the magnetic recording / reproducing apparatus having the above-mentioned structure, the first band-pass filter 6a and the second band-pass filter 6a are used to generate a tracking error signal. 2 band-pass filters having different center frequencies from the band-pass filter 6b are required, and two wave detectors, a first wave detector 7a and a second wave detector 7b, are required. Therefore, there is a problem that the circuit configuration is complicated as a whole.

The present invention was devised in view of the above circumstances, and an object thereof is to provide an auto-tracking system having a simpler circuit configuration in a magnetic recording / reproducing apparatus.

[0025]

An automatic tracking method in a magnetic recording / reproducing apparatus according to the present invention is an automatic tracking method that uses a beat signal between a reference pilot signal of a traveling track and a pilot signal of an adjacent track. As a signal, only the beat signal with the pilot signal of the adjacent track of only one of the adjacent tracks on both sides of the running track is taken out, the level of the beat signal is updated and stored, and the level of the beat signal of this time and the previous stored value are stored. It is characterized in that the tracking error signal is generated based on the magnitude comparison with the level of the beat signal.

[0026]

[Function] The beat signal level is updated and stored at the time of reproduction from each track, and the tracking error signal is generated by comparing the level of the current beat signal and the previous beat signal. Therefore, the beat signal is extracted. Only one bandpass filter and one detector are required.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an auto tracking system in a magnetic recording / reproducing apparatus according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing the electrical structure of the auto-tracking system in the VTR according to the embodiment.

In the figure, 1a and 1b are a pair of rotary heads (recording / playback heads) provided 180 ° apart on a rotary cylinder, 2 is a head amplifier having a head switching section,
3 is a bandpass filter (or a lowpass filter may be used) for extracting pilot signals of frequencies f ₁ , f ₂ , f ₃ , and f ₄ from the reproduced signal, 4 is a reference pilot signal generator, and 5 is a balanced modulator (BM). ). Up to this point, the process is the same as the conventional example (FIG. 2).

Reference numeral 6a is a bandpass filter having a center frequency of f _H (16 kHz), and 7a is a detector at the next stage of the bandpass filter 6a. In this embodiment, the bandpass filter 6b having a center frequency of 3f _H (46 kHz) and the detector 7b at the next stage, which are provided in the conventional example, are not used.

Reference numeral 21 is a smoothing circuit, 22 is a memory, 23 is a differential amplifier, 24 is a polarity inverter, 25 is a changeover switch, and 26 is a timing changeover signal generator. The timing switching signal generator 26 outputs a head switching pulse to the head switching unit in the head amplifier 2 and a polarity switching pulse to the changeover switch 25 at a predetermined timing.
Moreover, it is configured to output a write / read control signal to the memory 22. The smoothing circuit 21 smoothes the output signal from the detector 7a, and the smoothing signal by the smoothing circuit 21 is divided into two, one of which is input to the non-inverting input terminal (+) of the differential amplifier 23, and the other of which is input. Are written in the memory 22. The output port of the memory 22 is connected to the inverting input terminal (−) of the differential amplifier 23.

The output terminal of the differential amplifier 23 is divided into two, one of which is directly connected to one of the input terminals of the changeover switch 25, and the other of which is connected via the polarity inverter 24 to the other input terminal of the changeover switch 25. It is connected to the. The common output terminal of the changeover switch 25 is connected to a capstan motor servo circuit (not shown).

The smoothing circuit 21 may be digital or analog.

Next, the operation of the auto-tracking system in the magnetic recording / reproducing apparatus of this embodiment will be described.

It is assumed that a pilot signal is already recorded on each track on the magnetic tape as shown in FIG.

At the time of reproduction, the signals recorded on the magnetic tape are read by the heads 1a and 1b. The signals read by both heads 1a and 1b are alternately switched by the head switching pulse from the timing switching signal generator 11 to become a continuous signal, which is input to the head amplifier 2 and amplified. Bandpass filter 3
Extracts only the pilot signal component from the amplified reproduction signal and inputs it to the balanced modulator 5. The reference pilot signal generator 4 generates a reference pilot signal having the same frequency as that of the track on which the head 1 a or 1 b is currently traveling, and inputs it to the balanced modulator 5. The balanced modulator 5 receives the pilot signal and the reference pilot signal and generates a beat signal.

Since the contents of the memory 22 are relevant, the operation of the truck D _-1 during traveling will be described before the operation of the truck A ₀ during traveling.

[0038] [1] when the head traveling time track D _-1 track D _-1 (pilot signal f ₄₎ is traveling, the travel speed of the magnetic tape is to a little slow, in the balanced modulator 5 Beat signal component f _H with the immediately preceding adjacent track C _-1 (pilot signal f ₃ ).
Will increase.

Since the center frequency of the bandpass filter 6a is f _H , the detector 7a and hence the output of the smoothing circuit 21 becomes high level, and the previous beat signal level stored in the memory 22 is also large. Become.

On the other hand, when the tape running speed is a little high, the beat signal component 3f _H with the next adjacent rack A ₀ (pilot signal f ₁ ) increases, but the beat signal component f _H is extremely small. The memory 22
The previous beat signal level stored in is also small.

[2] Running on Track A ₀ Next, it is assumed that the head is running on the track A ₀ . At this time, the beat signal component 3f _H with the immediately preceding adjacent track D ₋₁ is blocked by the bandpass filter 6a, and the beat signal component f _H with the immediately following adjacent track B ₀ passes through the bandpass filter 6a. To do. When the head is traveling on the track A ₀ , the timing switching signal generator 26
Outputs a polarity switching pulse for switching the selector switch 10 to the polarity inverter 24 side.

When the tape running speed is slow When the running speed of the magnetic tape remains slow, the running of the head depends on the preceding adjacent track D ₋₁ , and as an output from the balanced modulator 5, The beat signal component 3f _H between the traveling track A ₀ (pilot signal f ₁ ) and the immediately preceding adjacent track D _-1 (pilot signal f ₄ ) increases, but the next adjacent track B ₀ (pilot signal f 1) increases. ₂ ) and the beat signal component f _H becomes extremely small.

Therefore, the beat signal component f _H extracted by the band pass filter 6a (center frequency f _H ) in the next stage of the balanced modulator 5 is small, and this time is output via the detector 7a and the smoothing circuit 21. The beat signal level of is also low. This low-level beat signal level of this time is input to the non-inverting input terminal (+) of the differential amplifier 23.

In synchronization with this, the previous beat signal level is read from the memory 22 and input to the inverting input terminal (-) of the differential amplifier 23. When the tape running speed is slow, the previous beat signal level stored in the memory 22 is high as described in [1]. Therefore, the output of the differential amplifier 23 shifts to the negative side. Since the changeover switch 25 is changed over to the polarity reversing device 24, the tracking error signal output to the capstan motor servo circuit is shifted to the plus side to increase the tape running speed.

The low-level beat signal level at this time due to the slow tape running speed is updated and stored in the memory 22.

Contrary to the above, when the tape traveling speed is fast, when the traveling speed of the magnetic tape remains high, the head traveling is biased toward the next adjacent track B ₀ , and the balance modulator 5 As the output of, the beat signal component f _H between the traveling track A ₀ (pilot signal f ₁ ) and the next adjacent track B ₀ (pilot signal f ₂ ) increases. Therefore, the beat signal component f _H extracted by the bandpass filter 6 a having the center frequency f _H increases, which causes the detector 7 a and the smoothing circuit 21.
This time, the beat signal level output via is high.

This high-level beat signal level of this time is input to the non-inverting input terminal (+) of the differential amplifier 23.
In synchronization with this, the previous beat signal level is read from the memory 22, and the inverting input terminal (-) of the differential amplifier 23 is read.
Entered in. When the tape running speed is slow, the previous beat signal level stored in the memory 22 is low as described in [1]. Therefore, the output of the differential amplifier 23 shifts to the plus side, the tracking error signal inverted by the polarity inverter 24 shifts to the minus side, and is output to the capstan motor servo circuit via the changeover switch 25. Reduce the running speed of.

The high-level beat signal level at this time due to the high tape running speed is updated and stored in the memory 22.

As described above, when the head is traveling on the track A ₀ , a high output level of the smoothing circuit 21 corresponds to a high tape traveling speed, and a low output level thereof is a tape traveling. It corresponds to the slow speed. The same is true when traveling on the track C ₀ .

[3] Running of track B ₀ When the head is running on track B ₀ , the beat signal component f _H with the preceding adjacent track A ₀ passes through the bandpass filter 6 a and becomes 1 The beat signal component 3f _H with the adjacent track C ₀ behind is blocked by the bandpass filter 6a. When the head is traveling on track B ₀ ,
The timing switching signal generator 26 outputs a polarity switching pulse for switching the switching switch 25 to the differential amplifier 23 side.

When the tape running speed is slow When the running speed of the magnetic tape remains slow, the running of the head depends on the preceding adjacent track A ₀ , and in the balanced modulator 5, the running track B ₀ The beat signal component f _H between the (pilot signal f ₂ ) and the immediately preceding adjacent track A ₀ (pilot signal f ₁ ) increases. Therefore, the beat signal component extracted by the bandpass filter 6a (center frequency f _H ) increases, and the beat signal level of this time output via the detector 7a and the smoothing circuit 21 becomes a high level. This high level beat signal level of this time is input to the non-inverting input terminal (+) of the differential amplifier 23.

In synchronization with this, the previous beat signal level is read from the memory 22 and input to the inverting input terminal (-) of the differential amplifier 23. When the tape running speed is slow, the previous beat signal level stored in the memory 22 is low as described in [2]. Therefore, the output of the differential amplifier 23 shifts to the plus side, the tracking error signal passing through the changeover switch 25 as it is shifts to the plus side, and the tape running speed is increased.

The current high level beat signal level due to the slow tape running speed is updated and stored in the memory 22.

Contrary to the above, when the tape traveling speed is fast, when the traveling speed of the magnetic tape remains high, the head traveling is biased toward the next adjacent track C ₀ , and the balance modulator 5 As for the output, the beat signal component 3f _H between the traveling track B ₀ (pilot signal f ₂ ) and the next adjacent track C ₀ (pilot signal f ₃ ) increases, but the previous adjacent track A ₀ And the beat signal component f _H is extremely small. Therefore, the beat signal component extracted by the bandpass filter 6a is reduced, and the beat signal level of this time output from the detector 7a and the smoothing circuit 21 is low.

The low-level current beat signal level is input to the non-inverting input terminal (+) of the differential amplifier 23.

In synchronization with this, the previous beat signal level is read from the memory 22 and input to the inverting input terminal (-) of the differential amplifier 23. When the tape running speed is high, the previous beat signal level stored in the memory 22 is high as described in [2]. Therefore, the output of the differential amplifier 23 shifts to the minus side, and the tracking error signal passing through the changeover switch 25 as it is also shifts to the minus side, thereby reducing the tape running speed.

The low-level beat signal level at this time due to the high tape running speed is updated and stored in the memory 22.

As described above, when the head is traveling on the track B ₀ , a high output level of the smoothing circuit 21 corresponds to a slow tape traveling speed, and a low output level thereof is a tape traveling. It corresponds to the high speed. The same applies when traveling on the track D ₀ .

By repeating the feedback control based on the tracking error signal as described above, automatic tracking is performed on the traveling track so that the tracking error signal is always at the same level.

The relationship between the high and low output levels of the smoothing circuit 21 and the high tape traveling speed is summarized for each traveling track. Becomes

In the present embodiment, the smoothing circuit 21 and the memory 22 are required, but since the existing memory can be used as the memory 22, it is only necessary to increase the number of the smoothing circuits 21. .. Instead, the second bandpass filter 6b and the second detector 7b of the conventional example are used.
Since and can be omitted, the overall circuit configuration is simplified.

In the above embodiment, the band pass filter connected to the next stage of the balanced modulator 5 has the lower center frequency f _H , but the present invention is not limited to this. A bandpass filter of 3f _H having a higher center frequency may be used.

Further, the portion surrounded by the broken line in FIG. 1 may be replaced with software for a capstan motor, and in this case, the external circuit configuration is further simplified.

[0064]

As described above, according to the present invention, since only one bandpass filter and the next-stage detector of the balanced modulator are required, respectively, the circuit configuration can be simplified as a whole. There is an effect that can be.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of an auto tracking system in a magnetic recording / reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an electrical configuration of an auto tracking system in a magnetic recording / reproducing apparatus according to a conventional example.

FIG. 3 is a diagram showing a recording pattern of a general pilot signal on a magnetic tape in a VTR.

FIG. 4 is a frequency spectrum of a pilot signal.

[Explanation of symbols]

 1a, 1b Rotating head 2 Head amplifier 3 Bandpass filter 4 Reference pilot signal generator 5 Balanced modulator 6a Bandpass filter 7a Detector 21 Smoothing circuit 22 Memory 23 Differential amplifier 24 Polarity inverter 25 Changeover switch 26 Timing switching signal generation vessel

Claims (1)

[Claims] 1. An auto-tracking system using a beat signal between a reference pilot signal of a traveling track and a pilot signal of an adjacent track, wherein only one of adjacent tracks on both sides of the traveling track is used as a beat signal. Only the beat signal with the signal is taken out, the level of the beat signal is updated and stored, and a tracking error signal is generated based on the magnitude comparison between the level of the current beat signal and the level of the previous stored beat signal. The auto-tracking method in a magnetic recording / reproducing apparatus characterized in that