JPH02267764A - Magnetic tape reproducing device - Google Patents

Abstract

PURPOSE:To eliminate a restriction of an operation amplifier, etc., and to enlarge enough a DC gain of an integration filter and hence to facilitate an alternation of filtering characteristics by fetching an output of a tracking detection circuit as a digital value and filing it digitally after adding with a speed error calculator. CONSTITUTION:A feedback loop consisting of a speed detector 7, a synchronization detector 4, a reference value generator 10, a digital filter 22, a D/A converter 23 and a driving circuit 13 is operated in order that an output frequency of the detector 7 becomes a value equivalent to a generated data of the generator 10 to be stable. Now, the digital filter 22 is constituted to be given integration filtering characteristics, and a capstan motor 5a is rotated at an almost constant rotation speed. By this method, torque of the motor 5a is given to a magnetic tape 1 by a pinch roller 6 and a capstan shaft 5b to make it travel at a constant speed. That is, a characteristic alternation of the filter is feasible in a way of software, thus simplifying hardware concerned.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic tape playback device that can be used in digital audio recorders, video tape recorders, and the like.

Conventional technology In a digital audio tape recorder that performs recording and playback using a rotating head, a signal (tracking detection signal) for detecting the positional relationship between the head and the recorded track is placed at a predetermined location on the track formed on the magnetic tape. A method has been used in which a head is recorded on a track (called ``track detection signal'') and the head is made to travel correctly on a track using this tracking detection signal during playback (for example, Japanese Patent Application No. 1988-9304).

An example of the above-mentioned conventional magnetic recording/reproducing device will be described below with reference to the drawings.

Figure 2 shows an example of a magnetic tape on which tracking detection signals are recorded, Figure 3 shows an example of a tracking signal recording pattern, and Figure 8 shows an example of a magnetic tape on which a tracking detection signal is recorded. FIG. 2 is a diagram showing an example of a device that performs tracking (controlling the head so that it travels correctly on a recorded track is referred to as "tracking").

In the example of FIG. 8, the tracking detection signal includes a pilot signal (hatched areas in FIG. 3) that detects the degree of overlap between the head and adjacent tracks from crosstalk, and a synchronization signal (hatched areas in FIG. 3) that synchronizes the detection. Figure 30
1.302 hatched area).

In FIG. 8, 2 a and 2 b are a pair of heads that sequentially record and reproduce tracks from each other, and 3 is a head 2 a.

2b is a rotating cylinder attached, 1 is a magnetic tape,
16 is a bandpass filter that filters a pilot signal for tracking from the outputs of the heads 2a and 2b;
17 is a rectifier; 14 is a synchronization signal detection circuit that detects a synchronization signal from the outputs of the heads 2a and 2b; and 15 is a two-pulse pulse SP1 immediately after the synchronization signal detection circuit 14 detects the synchronization signal, and pulse SP2 after a certain period of time. 18 is a sample-and-hold circuit that samples and holds the output of the rectifier 17 at the timing of pulse SP1; 19 is the output of the sample-and-hold circuit 18 and the rectifier 1;
A subtracter 20 takes the difference between the output signals of 7 and 20 a subtracter 19 at the timing of the pulse SP2 output from the pulse generation circuit 15.
A sample and hold circuit that samples and holds the output of
9a and 9b are reels on which the magnetic tape 1 is turned clockwise; 8a;
8b is a post forming a running path for the magnetic tape 1; 5a;
.

5b is a capstan motor and a capstan shaft for running the magnetic tape 1, 6 is a pinch roller, and 7 is a capstan motor and a capstan shaft for running the magnetic tape 1;
FGl outputs a signal with a frequency proportional to the rotation speed of the capstan motor 5a; 41 is an F/V converter; 11
0 is a reference voltage generator that generates a voltage corresponding to the desired capstan rotation speed, 11 is a subtracter that takes the difference between the output of the reference voltage generator 110 and the output of the F/V converter 41, and 12
13 is an adder that adds the output of the sample and hold circuit 20 and the output of the subtracter 11; 42 is an integral filter that integrates the output of the adder 12 to improve control characteristics in the low frequency range;
is a drive circuit that drives the capstan motor 5a based on the output of the integral filter 42.

In the figure, FG7. F/V converter 41° group Q voltage generator 110. Integral filter 42. The drive circuit 13 is
The output frequency of FG7 is base'r! Since the voltage becomes stable at a value corresponding to the voltage generated by the r-voltage generator 110, the capstan motor 5a rotates at a substantially constant rotation. The pinch roller 6 and the capstan shaft 5b apply the rotational force of the capstan motor 5a, which rotates at a constant rotation, to the magnetic tape 1, causing it to run at a nearly constant speed.

Next, a method for performing tracking in this conventional example will be explained.

In FIG. 2, 201 is a track, and 202a.

202b is a recording position of a tracking detection signal, 203 is a vector indicating the traveling direction of the head, and 204 is a vector indicating the traveling direction of the magnetic tape 1.

FIG. 3 shows 2 02 a and 202 b in FIG.
This is an enlarged view of one of the areas. 303 and 304 are pilot signals, and signals of the same frequency with less azimuth loss are recorded, and those with the same diagonal lines are recorded by heads with the same azimuth angle. (In the case of the same figure, recording is performed using heads with two azimuth angles.)3
01, 302, and 302a are synchronization signals for detecting signals from adjacent tracks of the pilot signal, and those with the same diagonal lines are recorded by heads with the same azimuth angle.

The tracking detection signal consists of a pilot signal and a synchronization signal.

Head gap 305 of head pair 2 al 2 b
In order to reliably detect the pilot signal, the head width is set wider than the track width.

A bandpass filter 16 selects a pilot signal, and a synchronization signal detection circuit 14 detects a synchronization signal on the track. The pilot signal filtered by the bandpass filter 16 is rectified and detected by the rectifier 17. The synchronization signal detection circuit 14 can be configured with a bandpass filter and a comparator, or can be configured to digitally detect the reproduced signal frequency. For example, if the head gap is
When passing the position shown in FIG. 305, the synchronization signal 302a in that track is detected by the herad gap 305. The pulse generating circuit 15 generates a pulse SPI at the moment when the head detects a synchronization signal, and generates a pulse SP after a certain period of time.
2, a total of two pulses are generated. first pulse SP1
is supplied to the sample and hold circuit 18, and the second pulse SP2 is supplied to the sample and hold circuit 20. S
When the PI is generated, the bed gap 305 is reproducing the pilot signal of the adjacent truck on the right side in the direction of travel, and the SF3 is reproducing the pilot signal of the adjacent truck on the left side in the direction of travel. generated.

Therefore, the sample and hold circuit 18 samples and holds the pilot signal amplitude voltage from the right truck in the traveling direction. Further, a subtracter 19 calculates the difference between the output of the sample and hold circuit 18 and the output of the rectifier 17. science fiction
3, the head gap 305 is reproducing the pilot signal of the adjacent track on the left side in the traveling direction, and the sample and hold circuit 20 samples and holds the difference in the amplitude voltage of the pilot signal from both adjacent tracks.

Since the crosstalk signal from the adjacent track is proportional to the amount of head protrusion to the corresponding track, the sample hold circuit 20 calculates the difference in the amount of head protrusion from both adjacent tracks, that is, the position of the center of the track and the center of the spacing gap. A voltage proportional to the difference is held.

In the conventional example shown in FIG. 8, the relative position between the running position of the heads 2a, 2b and the recorded track is detected as the output of the sample hold circuit 20, and the difference between the outputs of the F/V converter 41 and the reference voltage generator 110 is detected. is added to the head 2 al 2 via the adder 12 and the output signal of the sample hold circuit 20 is controlled to be zero.
The capstan motor 5a is rotated so as to run on the track on which b is recorded.

An integral filter 42 cumulatively integrates the output of the adder 12.

If the output of the adder 12 is not zero, the value of the integral filter changes. Therefore, in a stable state, the input signal to the integral filter 42 becomes almost zero, ensuring a desired tracking state more reliably.

Problems to be Solved by the Invention In such conventional techniques, the integrating filter 42 is often constructed from an operating amplifier or the like, which makes it difficult to secure sufficient gain in direct current, and at the same time, it is difficult to maintain integration characteristics at low frequencies. In order to obtain this, there were problems such as the need to use a large electrolytic capacitor, resulting in a large circuit scale and high circuit cost. Further, when changing the integral characteristic according to the operating mode, there is a problem that switching of capacitors and the like must be performed using a circuit.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a magnetic tape playback device in which the filter is digitally processed so that the characteristics can be changed using software, and the hardware can be simplified. The purpose is

Means for Solving the Problems In order to solve the above problems, the present invention provides a magnetic tape reproducing apparatus according to the present invention, in which a pilot signal for detecting a tracking position by crosstalk from an adjacent track and a detection synchronization signal thereof are transmitted to a magnetic tape. A rotating cylinder to which a reproducing head is attached, a driving means for running the magnetic tape, and a reproduction signal from the reproducing head to the track on the magnetic tape. a tracking detection circuit for detecting a recorded tracking signal; an analog-to-digital converter for converting the output of the tracking detection circuit into digital data; and a speed for generating a signal corresponding to the running speed of the magnetic tape in the drive means. a speed error calculator that outputs a difference between the period or frequency of the output signal of the speed detector and a value corresponding to a desired tape speed as a digital value; the analog-to-digital converter; and the speed error calculator. a digital filter that digitally filters the output of the adder; and a digital-to-analog converter that converts the output of the digital filter to an analog voltage; It is characterized by a configuration in which the output of the converter is used as a drive signal to the drive means.

Function The present invention is described above in 111! With this configuration, the output of the tracking detection circuit is taken in as a digital value, summed with a speed error calculator, and then digitally filtered. Therefore, there are no restrictions on operational amplifiers, etc., the DC gain of the integral filter can be sufficiently large, and large components such as electrolytic capacitors are not required. Further, the filtering characteristics can be easily changed in accordance with the change in the operation mode without adding any external parts such as a capacitor.

Example Below, regarding a magnetic tape playback device according to an example of the present invention,
This will be explained with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, and FIG. 2 shows an example of a magnetic tape on which tracking signals described in the conventional example are recorded.
FIG. 3 is a diagram showing an example of tracking signal recording and the running of the head, FIG. 4 is an operation waveform diagram of the embodiment of FIG. 1, and FIG. 7 is a diagram showing an example of the configuration of the period counter in FIG. 1. be.

In the example shown in Fig. 3, the tracking detection signal includes a pilot signal (hatched areas 303 and 304 in the figure) that detects the degree of overlap between the head and adjacent tracks from crosstalk, and a synchronization signal (hatched areas 303 and 304 in the figure) that synchronizes the detection. Figure 301
．． 302. 302 (hatched area a)).

In FIG. 1, 2a+2b is a pair of heads that sequentially record and reproduce tracks, 3 is a rotating cylinder to which heads 2a+2b are attached, 1 is a magnetic tape, and 16 is a band that filters a pilot signal for tracking from the output of heads 2at2b. a pass filter, 17 a rectifier, 14 a synchronization signal detection circuit for detecting a synchronization signal for detecting a pilot signal from the output of the heads 2a+2b;
15 is a pulse generation circuit that outputs two pulses, pulse SP1 immediately after the synchronization signal detection circuit 14 detects the synchronization signal, and pulse SP2 after a certain period of time; and 18 is a sample that samples and holds the output of the rectifier 17 at the timing of pulse SP1. Hold circuit, 18 is sample hold circuit 1
a subtracter 2 which takes the output of the output signal of the rectifier 17 and the output signal of the rectifier 17;
0 is a sample-hold circuit that samples and holds the output of the subtracter 19 at the timing of pulse SP2, 21 is an A/D converter that converts the output voltage of the sample-and-hold circuit 20 into a digital value, and 9a and 9b are the circuits on which the magnetic tape 1 is wound. Reels to be rotated; 8a and 8b are bosses forming a running path for the magnetic tape 1; 5a and 5b are capstan motors and capstan shafts for running the magnetic tape 1; 6 is a pinch roller; 7 is an FGl that outputs a signal with a frequency proportional to the rotation speed of the capstan motor 5a.
4 is a period counter that counts the period of the output signal of FG7;
10 is a basic value generator that generates data corresponding to the desired capstan rotation speed, 11 is a subtracter that takes the difference between the output of the basic value generator 10 and the output of the period counter 4, and 12 is an A/D conversion 22 is a digital filter that filters the output data of the adder 12; 23 is a D/A converter that converts the output data of the digital filter 22 into an analog voltage; 1;
3 is a drive circuit that drives the capstan motor 5a based on the output of the D/A converter 23.

In FIG. 1, bandpass filter 16. Synchronous signal detection circuit 14. Pulse generation circuit 15. Rectifier 17. Sample hold 18. Subtractor 19. The part consisting of the + sample hold 20 constitutes the tracking detection circuit 101, and the F
G7 operates as a speed detector for the magnetic tape 1, and the period calculator 4° reference value generator ZIO and subtractor 11 constitute a speed error calculator. Further, the drive circuit 13. The capstan motor 5a, the capstan shaft 5b, and the pinch roller 6 operate as driving means for the magnetic tape 1.

Next, the operation of this embodiment will be explained.

In the same figure, FG7. Period counter4. Reference value generator 10. Digital filter 22. D/A conversion m23. The feedback loop consisting of the drive circuit 13 operates so that the output frequency of the FG 7 becomes a value corresponding to the data generated by the reference value generator 10 and becomes stable. Here, the digital filter 22 is configured to exhibit the integral filter characteristics shown in the conventional example. Therefore,
The capstan motor 5a rotates at a substantially constant rotation. The pinch roller 6 and the capstan shaft 5b apply the rotational force of the capstan motor 5a, which rotates at a constant rotation, to the magnetic tape 1, causing it to run at a nearly constant speed.

FIG. 7 shows an example of the structure of the period counter 4. As shown in FIG.

701 is a limiter that shapes the output of FG7 into a rectangular wave, 7
02 is a delay circuit, 703 is a clock generator, 704 is a counter that counts the output of the clock generator 703, 705
is a latch circuit. At the rising edge of FG7, the latch circuit 705 latches the count data of the counter 704. Further, the counter 704 is connected to the delay circuit 702 through the delay circuit 702.
It is cleared immediately after the data is latched into the latch circuit 705. Therefore, the number of clock pulses generated by the clock generator 703 during the period of the output signal of FG7 is held in the latch circuit 705.

As described above, the period counter 4 counts and outputs the signal period of the FG7 as a digital value.

In FIG. 2, 201 is a truck, 202 a120
2b is a recording position of a tracking detection signal; 203 is a vector indicating the direction of movement of the head; and 204 is a vector indicating the direction of movement of the magnetic tape 1.

Figure 3 shows 202 a and 202 in Figure 2.
This is an enlarged view of one of the areas b. 303
304 is a pilot signal, and a signal having the same frequency with less azimuth loss is recorded, and the same diagonally shaded signal is recorded by a head having the same azimuth angle. (In the case shown in the figure, recording is performed using heads with two azimuth angles.)
Reference numerals 301, 302, and 302a are synchronization signals for detecting signals from adjacent tracks of the pilot signal, and those with the same diagonal lines are recorded by heads having the same azimuth angle.

In addition, the example shown in the figure shows an example in which the recording length of the synchronization signal is different so that it can be distinguished from adjacent tracks recorded with the same azimuth.

The tracking detection signal consists of the following two pilot signals and a synchronization signal. 305 indicates a head gap, and 306 indicates a moving direction of the helad gap 305.

Head gap 305 of head pair 2 al 2 b
In order to reliably detect the pilot signal, the head width is set wider than the track width.

In FIG. 1, a bandpass filter 16 selectively filters a pilot signal, and a synchronization signal detection circuit 14 detects a synchronization signal on a track. Figure 4A shows the detected synchronization signal, and Figure 4A shows the pilot signal. The pilot signal filtered by the bandpass filter 16 is rectified and detected by the rectifier 17 and shaped into the signal shown in FIG. The synchronization signal M output circuit can be configured with a bandpass filter and a comparator, or can be configured to digitally detect the reproduced signal frequency. FIG. 4A shows an example of extraction using a bandpass filter. The pulse generating circuit 15 generates a pulse SP1 at the moment the head detects the synchronization signal.
After a certain period of time, a pulse SP2 is generated, a total of two pulses. These two pulses are shown in FIG. 4 as h and h, respectively. The sample hold circuit 18 is a pulse SP
The output of the rectifier 17 is sampled and held at I. In FIG. 3, when the head gap 305 advances as shown in the figure, when the synchronization signal detection circuit detects the synchronization signal, that is, when SP1 is generated, the head gap 305 is the pilot signal of the adjacent track on the right side in the direction of travel. The S crosstalk generated after a certain time is regenerated.
F3 is generated when the head gap 305 is reproducing the crosstalk portion of the pilot signal of the adjacent track on the left side in the traveling direction.

Therefore, the sample and hold circuit 18 samples and holds the pilot signal amplitude voltage from the right truck in the traveling direction. In the subtracter 19, the difference between the output of the sample hold circuit 18 and the output of the rectifier 17 is calculated. science fiction
3, the head gap 305 is reproducing the pilot signal of the adjacent track on the left side in the direction of travel, and S
When F3 occurs, the output of subtracter 17 is equal to the difference in pilot signal amplitude voltage from both adjacent tracks being reproduced by the head.

Therefore, the sample-and-hold circuit 20 samples and holds the difference in amplitude voltage of the pilot signals from both adjacent tracks reproduced by the head.

Since the crosstalk signal from adjacent tracks is proportional to the amount of head protrusion to the corresponding track, the sample hold circuit 20 detects the difference in the amount of head protrusion from both adjacent tracks, that is, the difference between the positions of the track center and the center of the spacing gap. A voltage proportional to is held.

The output of the sample hold circuit 20, which is output as the relative position between the traveling position of the head 2 al 2 b and the recorded track, is sent to a period counter 4. By adding the difference of the reference value generator 10 to the output of the subtracter 11 and controlling the output signal of the sample and hold circuit 20 to zero, the heads 2a+2b run in the center of the recorded track. Rotate the capstan motor 5a so as to rotate the capstan motor 5a.

The integration operation of the digital filter 22 greatly increases the effect of zeroing the output signal of the sample and hold circuit 20. That is, if the output of the adder 12 is other than zero, the output increases due to the cumulative effect of the digital filter 22. Therefore, the output of the adder 12 becomes zero,
It becomes steady state.

Therefore, a control circuit with characteristics that can cope with load fluctuations can be constructed without using an operational amplifier or the like.

Furthermore, in FIG. 1, the portion surrounded by a broken line 102, that is, the period counter 4. Reference value generator 10. A/D converter 21
．． Subtractor 11. Adder 12. Digital filter 22
, the D/A converter 23 can be configured as one IC, or furthermore, can be configured as a microcomputer. Especially period counter 4. The digital filter 22 can also be configured by microcomputer software. In particular, when it is realized using microcomputer software, even when changing the operating mode such as the tape speed, the effect is that only the software needs to be changed, and no additional hardware is required.

Next, a configuration example of the digital filter 22 in another embodiment of the present invention will be described. Digital filter 2
The configuration other than 2 is completely the same as the embodiment shown in FIG. 1, and is not illustrated.

FIG. 5 shows an example of the configuration of the digital filter 22, and FIG. 6 shows its characteristic diagram.

501 is an input terminal for receiving the signal from the adder 12 in FIG. 1, 502 is an adder, 503 is a feedback path with a temporary delay element of Z-1, 504 is a thread count counter with a gain of 1, and 505 is a The adder, 50e, is the D/A converter 23 in FIG.
This is the output terminal for

The digital filter shown in FIG. 5 is configured as an IIR type filter (infinite impulse response type filter) having a feedback path.

The digital filter shown in FIG. 5 has the following characteristics, and the term 1/(1-Z-1) indicates an integral characteristic. The response characteristic of the above equation is shown in FIG. In the figure, the vertical axis 801 is the transfer gain, the horizontal axis 602 is the frequency, 60
3 is the response characteristic. In the integral characteristic, the gain decreases as the frequency increases, but because of the constant term 1 in the above equation, the gain becomes 1 in the high frequency range.

The frequency fc at which the gain changes from the integral characteristic to 1 is the base K
It can be changed by

-The time delay 2-1 may be the output signal cycle of FG7 in FIG. 1, or may be realized by a timer interrupt of a microcomputer or the like.

Since the integral type digital filter shown in FIG. 5 performs all processing digitally, the DC gain can be made infinite.

As described above, it is possible to digitally process the filter and change the characteristics using software, without using an integral filter composed of an Operaron amplifier or the like, which is necessary in the conventional technology. Therefore, similarly to the embodiment shown in FIG. 1, it is possible to control the rotation of the capstan motor 5a so that the heads 2a+2b run in the center of the recorded track regardless of the presence or absence of load fluctuations.

Effects of the Invention As described above, according to the present invention, by digitally processing the filter so that its characteristics can be changed using software, and furthermore, by realizing it using microcomputer software, it is possible to overcome the conventional technology. This eliminates the need for an integral filter composed of an Operalon amplifier, etc., which was previously required, and also eliminates the difficulty of securing sufficient gain in direct current, which was a problem with Operaron amplifiers, and eliminates the need for a large electrolytic filter to obtain integral characteristics at low frequencies. It is possible to produce great practical effects, such as making it possible to solve problems such as the necessity of using a capacitor, which increases the circuit scale and the circuit cost.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention, FIG.
FIG. 3 is a diagram showing an example of a recorded magnetic tape, FIG. 4 is an operation waveform diagram of the embodiment of FIG. 1, FIG. 5 is a configuration diagram showing a second embodiment of the present invention, and FIG. is a characteristic diagram thereof, FIG. 7 is a diagram of a configuration example of a period counter used in the present invention, and FIG. 8 is a diagram of a conventional example. 1...Magnetic tape, 2a+2b...Reproduction head, 3...Rotating cylinder, 5at 5by 8.
13... Drive means, 101... Tracking detection circuit, 21... Analog-digital converter,
7... Speed detector, 4.10.11... Speed error calculator, 12... Adder, 22... Digital filter, 23... Digital-to-analog converter. Name of agent: Patent attorney Shigetaka Awano and one other person

Claims (3)

[Claims] (1) A device for reproducing a magnetic tape recorded on a track in which a tracking signal for detecting a tracking position by crosstalk from an adjacent track is formed on the magnetic tape, comprising a rotating cylinder to which a reproducing head is attached. a driving means for running the magnetic tape; a tracking detection circuit for detecting a tracking signal recorded on a track on the magnetic tape from a reproduction signal from the reproduction head; and converting the output of the tracking detection circuit into digital data. a speed detector that generates a signal corresponding to the running speed of the magnetic tape in the drive means; and a value corresponding to the desired tape speed based on the period or frequency of the output signal of the speed detector. a speed error calculator that outputs the difference between the speed error calculator and the speed error calculator as a digital value; an adder that adds the outputs of the analog-to-digital converter and the speed error calculator; and a digital filter that digitally filters the output of the adder. , a digital-to-analog converter that converts the output of the digital filter into an analog voltage, and the output of the digital-to-analog converter is configured to be used as a drive signal to the drive means. Tape playback device. (2) The magnetic tape reproducing apparatus according to claim 1, wherein the digital filter is an IIR type filter (infinite impulse response filter) having integral characteristics in a low frequency range. (3) The magnetic converter according to claim 1, wherein the speed error calculator and the digital filter are configured as a microcomputer program, and the analog-digital converter is configured as a hardware built into the microcomputer. Tape playback device.