JP2581273B2 - Magnetic recording / reproducing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus for recording / reproducing on / from a magnetic recording medium.

[Conventional technology]

FIG. 10 is a sectional view of a rotary drum used in a conventional magnetic reproducing apparatus disclosed in, for example, JP-A-63-73219. In the figure, a rotary shaft (1) rotates through a bearing (2). Installed on the drum. The rotating drum (4) is mounted on a rotating shaft (1), and an electromagnetically driven actuator (5) is connected to the rotating drum (4).

FIG. 11 is a diagram showing the relationship between a magnetic head (7) and a recording track (8) in a conventional magnetic reproducing apparatus disclosed in, for example, JP-A-59-68862.

FIG. 12 is a block diagram of a pilot signal generating circuit and a tracking error detecting circuit for generating a tracking error in a conventional magnetic reproducing apparatus disclosed in, for example, JP-A-59-68862. ) Is a reference oscillator (hereinafter abbreviated as OSC), (10) is a presettable counter, (11) is a flip-flop, (12) is a filter, and (14) is a sine wave output from the filter (12). Signal (20) and information signals (1
Mixer for adding 3), (15) a switch for recording / reproduction, (16) a magnetic head for recording / reproduction, (19) a processable counter by a track switching signal (17) and a recording / reproduction switching signal (18) A frequency division ratio control circuit for controlling the frequency division ratio of (10), (22) is a low-pass filter for inputting the reproduced signal (21), and (23) is output from the reference signal (20) and the low-pass filter (22). A mixer for adding a reproduced pilot signal, (24) is an amplifier, (25) is a dividing circuit,
(26a) and (26b) are bandpass filters, (27a) and (2
7b) is an envelope detector, and (28) is an envelope detector.

Next, the operation will be described. At the time of recording on a magnetic tape (T) as a magnetic recording medium, the control circuit (19) switches the frequency division ratio of the processable counter (10) based on the track switching signal (17). Output of counter (10) is flip-flop (11)
After further dividing the frequency by a filter (12), the signal (13) is converted into a sine wave (pilot signal), then added to the information signal (13) by the mixer (14), and the magnetic head (16 ) Is recorded on the magnetic tape (T).

Each time the recording track changes, the track switching signal (1
For switching the 7), for example, 4 of the 14 f ₁ ~f ₄ such as shown in Figure
Different types of pilot signals can be recorded. At this time, the frequency of the pilot signal needs to be set to a frequency that does not impair the information signal (13) in reproducing the information signal (13) and extracting the pilot signal. Selected from KHz to several hundred KHz.

Considering the frequencies of the pilot signals f _{1 to} f _{4 in} FIG. 11 in the case of the 4-frequency pilot system of a consumer 8-mm video tape recorder (VTR), f ₁ + f _A = f ₂ , f ₂ + f _B = f ₃ ...... When set as _{(1) f 4 + f a} = f 3, f 1 + f B = f 4, the reproducing reproduces a recorded signal from the magnetic tape (T) by the magnetic head (16) in FIG. 15 At this time, a pilot signal recorded along with the information signal (13) is also reproduced.

The pilot signal is extracted by the low-pass filter (22). At this time, in addition to the pilot signal being scanned, the pilot signal of a track on an adjacent track (on both sides) is also extracted as crosstalk.

Since the frequency of the pilot signal of the adjacent track is sufficiently lower than that of the video signal or the like, even if azimuth recording is performed, the signal is reproduced as a large crosstalk amount with little azimuth effect.

When the pilot frequency of the reference signal (20) written in the scanning track is added to the reproduced pilot signal by the mixer (23), the pilot signal due to crosstalk from both sides and the reference signal (20) are added. beat beat frequency f _a and f _B in occurs (1) obtained during the.

For example, in Figure 11, when reproducing the track where the pilot signal f ₂ is written as crosstalk
pilot signals f ₁ and f ₃ is also obtained, which when added in a mixer (23), (1) f 2 -f 1 = f A from the equation, f ₂ -f
₃ = beat signal from becoming a -f _B f _A, is f _B obtained.

Next, this is extracted by band-pass filters (26a) and (26b) through an amplifier (24) and a division circuit (25), and then detected by envelope detection circuits (27a) and (27b).
If Figure of the magnetic head (7) is on-track on f _2, it deviates slightly even f ₁ side, the beat signal f _A is increased,
For the opposite case of increasing the beat signals f _B, the tracking control signal (29) is taken out as the output of the differential amplifier (28).

The tracking control signal (2
9) After the phase compensation and the gain compensation in order to keep the stability and the quick response of the control system at predetermined values, the rotating drum (6) is driven by the brush and the slip ring (6) shown in FIG. 4) supplied to the actuator (5) in
By moving the magnetic head, a closed loop control that enables tracking so that the magnetic head always traces a predetermined track is performed.

By controlling the closed loop, even if the recording track is shifted or bent with respect to the head trajectory of the reproducing apparatus, the magnetic head can be made to follow such a track shift.

[Problems to be solved by the invention]

Since the conventional magnetic recording / reproducing apparatus is configured as described above, a tracking system for an extremely narrow track is configured to perform high-density recording / reproducing. In this case, means for detecting a track shift with high accuracy is required. Generally, a track shift is detected by recording a low-frequency pilot signal as described above.

However, in the case of digital magnetic recording, general recording,
Since the reproduced signal has a wide power spectrum from components close to DC to the highest recording frequency, gaps in so-called frequency allocation occur outside the band around the carrier and its surroundings as in conventional analog FM recording. I can't let it.

In particular, it is difficult to insert a low-frequency pilot signal for tracking into a gap in frequency allocation as in the case of the current analog 8 mm VTR in digital recording.

However, in the case of digital recording, if the power level of the pilot signal recorded in the frequency range of the tracking pilot signal is sufficiently higher than the power level of the recording signal obtained by modulating the digital information, the tracking pilot signal during reproduction is reproduced. Can be extracted with a band-pass filter or the like as in the case of the conventional example.

However, as described above, if the power level of the pilot signal is too high for the recording / reproducing signal, which is video and audio information, the waveform distortion will increase when demodulated during reproduction, and the error rate of the digital data will decrease. An increase occurs.

Particularly, when the digital data after the modulation and the tracking pilot signal are added in an analog manner before the recording amplifier at the time of recording and recorded, there is no correlation between the digital data and the pilot signal. Is simply a disturbance signal.

In other words, in the case of digital audio recorders, digital video recorders, and information recording devices that record and reproduce digital signals, the frequency spectrum of the recorded and reproduced signals contains many low-frequency components due to the characteristics of digital recording. When the digitally modulated signal is demodulated, there is no phase difference between the recording / reproducing signal and the pilot signal, resulting in waveform distortion and data error. The rate increases.

Therefore, if the power level of the pilot signal is lowered to reduce the waveform distortion, the servo (tracking) detection signal cannot be obtained because the necessary S / N cannot be obtained, and the servo cannot be applied. There were problems such as disappearance.

Further, during the tracking operation, as described above, since the tracking error is obtained by comparing the crosstalk levels of the pilot signals having different frequencies included in the reproduction signal, the variation in the frequency characteristics of the magnetic head can be reduced. In the reproduction system of the head performing the tracking operation due to the change due to the temperature characteristic, the frequency characteristic of the rotary transformer near the pilot signal frequency of the reproduction system, or the variation in the frequency characteristic of the head amplifier or the temperature characteristic, etc. If either one of the frequencies has higher or lower sensitivity, this difference in sensitivity directly results in a track shift. Also, a track shift occurs due to a difference between two band-pass filter characteristics (a difference in sensitivity and a shift in center frequency) in the track error generating circuit, so that there has been a problem that magnetic recording and reproduction on a narrow track cannot be performed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. In multiplexing the pilot signal with the information signal, the waveform distortion during digital demodulation is minimized as much as possible, and the servo detection signal is reduced. It is an object of the present invention to provide a magnetic recording / reproducing apparatus capable of obtaining a large S / N, narrowing a track pitch, and increasing recording / reproducing density.

[Means for solving the problem]

A magnetic recording / reproducing apparatus according to the present invention includes a rotating drum and an n-channel pair head (n) mounted on the rotating drum.
Is an integer of 2 or more) and a modulation circuit that modulates a digital signal and outputs a digital modulation signal. During recording, a CDS value (Code Word Digital Sum) representing a DC value per block in the digital modulation signal is recorded. The first and second pilot signals multiplexed on the digital modulation signal are generated by periodically changing the DSV value (Digital Sum Variation) in synchronization with the rotation phase of the rotating drum by increasing and decreasing the first and second pilot signals. The digital modulation signals are sequentially recorded by the n-channel pair head so that the two pilot signals are alternately recorded on every other track on the magnetic tape. Neither the first nor the second pilot signal is mixed in the reproduction signal by the channel head corresponding to the track where no recording is made. A magnetic recording / reproducing apparatus which detects a deviation between the channel head and the track based on crosstalk between the first and second pilot signals from the adjacent track and performs tracking control of the n-channel pair head. A signal that detects the deviation between the channel head and the track is fed back to a capstan motor that drives the magnetic tape through a low-pass filter, and the n-channel pair head is moved in parallel with the rotation axis of the rotating drum. This is configured so as to be applied also to the electromagnetically driven actuator for displacing the actuator.

(Operation)

In the magnetic recording / reproducing apparatus according to the present invention, when the channel head traces a track in which either the first or the second pilot signal is multiplexed on the digital modulation signal during reproduction, the two adjacent tracks are used. Has no effect of crosstalk of pilot signals from adjacent tracks since neither the first nor second pilot signal is recorded, and the pilot recorded on the track being traced by the channel head is Since the signal and the digital modulation signal are correlated with each other, it is possible to remove the waveform distortion of the data due to the multiplexing of the pilot signal when demodulating the digital modulation signal.
If the channel head traces a track on which neither the first nor the second pilot signal is multiplexed, the crossover of the first and second pilot signals multiplexed on both adjacent tracks is performed. Although the effect of talk is present, the pilot signal originally multiplexed on the track being traced by the channel head is not multiplexed, so that the effect of the pilot signal multiplexed on the track for tracking should be reduced as a whole. And the waveform distortion of the data due to the multiplexing of the pilot signal when demodulating the reproduced digital modulation signal is reduced.

Therefore, it is possible to realize a high-quality digital signal magnetic recording / reproducing apparatus which can sufficiently suppress the waveform distortion of the data of the reproduced digital modulation signal, and further suppress the waveform distortion sufficiently. Also allows.

Furthermore, the low frequency component of the signal that detects the deviation between the channel head and the track is fed back to the capstan motor, and the tracking control operation is also performed by the capstan motor. And a signal that detects the deviation between the channel head and the track is also applied to an electromagnetic drive actuator that displaces the head in parallel with the rotation axis of the rotating drum, so that relatively high frequency A high-precision tracking control operation capable of coping with track bending having a component is enabled.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, (30) is a PLL (Phase Locked Loop) circuit for generating a pilot signal synchronized with the rotating drum, and (31) is a two-phase pilot signal (A), (B) with inverted phase. The pilot signal generation circuit for generating the digital data (32) is the digitized recording data, (3)
3) is a ROM table in which a conversion algorithm is determined based on a digital modulation method, and (34) is a low-frequency component "DSV value (a), (b)" of digital data modulated by the ROM table (33). A DSV counter composed of an up / down counter and the like for detecting and outputting, (35) is a pilot signal (A), (B) and a DSV value (a), (b)
Comparison command circuit for comparing the ROM table (33)
Logic circuit for serializing the digital data from the head and distributing it to two pairs of magnetic heads (hereinafter abbreviated as heads) (α) and (β); (38a) and (38b) from the logic circuit (36) The recording current of the head (α), (β)
And a modulation amplifier (101).

(38a) and (38b) are reproduction amplifiers for amplifying reproduction signals from the heads (α) and (β), and (39a) and (39b) are for extracting pilot signals for pitch control during recording. Bandpass filters, (40a) and (40b) are detection circuits for checking the level of the pilot signal, (41a),
(41b) is a sample and hold circuit for holding the peak level of the output of the detection circuits (40a) and (40b).
2) is a differential amplifier for obtaining the difference between the pilot signal level reproduced by the head (α) and the pilot signal level reproduced by the head (β), and (43) is a phase amplifier for maintaining stability in the pitch control loop. The gain compensating circuit (44) is a drive amplifier for supplying a drive current to the actuator (5), and each part after the reproduction amplifier constitutes a tracking control means (102).

FIG. 2 shows 2CH during reproduction in one embodiment of the present invention.
(45a) and (45b) are band-pass filters for extracting a tracking control pilot signal included in the reproduced signals from the magnetic heads α and β. is there. (46) is a multiplier for multiplying the output of the bandpass filter (45a) by the output of the bandpass filter (45b). (47) The movable magnetic heads α and β mounted on the actuator (5) always accurately track the recording track on the basis of the track error signal (signal indicating the direction and amount of the track deviation) output from the multiplier. This is a circuit for compensating the phase and gain of the control system so that a control loop for tracing without deviation is constantly stable and a quick pull-in operation can be realized. Third
The figure shows a method of generating a track error signal when a movable magnetic head of 3 channels is provided.
Are the differential amplifiers that take the difference between the outputs of the head amplifiers (38a) and (38c) and amplify them. (49a) and (49b) are the frequency BHz of the tracking control pilot signal in the recording track pattern in the figure. A band-pass filter for extracting components, a comparator (50) for determining whether the output of the band-pass filter (45a) is large or the output of the band-pass filter (49b) is large, (51a), (5)
1b) is the output of the bandpass filters (45a) and (49a)
An analog switch for selecting the output of the band-pass filters (45b) and (49b), (52) is a hysteresis amplifier for shaping the output of the analog switch (51a), (53) is an inverting amplifier, and (54) ) Is the forward rotation amplifier, (55)
Is an analog switch for selecting between an inverting amplifier (53) and a forward amplifier (54).

FIG. 4 shows an example of the configuration of a tracking control system having a three-channel movable magnetic head.
Is a low-pass filter that passes only the low-frequency component of the track error signal, and (57) is a driver of the capstan motor (58). FIG. 5 shows the output of the α head β head and the output of the multiplication circuit (46) in FIG. 2 in the time axis direction. 6 is a track pattern diagram in FIG. 2, FIG. 7 is a track pattern diagram in FIGS. 3 and 4, FIG. 8 is a recording state diagram of a pilot signal, and FIG.
FIG. 1 is a recording signal frequency spectrum diagram of digital magnetic recording in an embodiment of the present invention.

Next, the operation of the above embodiment will be described. The ROM table (33) stores the digital modulation method of the above embodiment.
In the case of the 8bit-10bit conversion method, the following conversion table is stored.

Therefore, taking an example of this 8-bit to 10-bit conversion method, 1
When the CDS value or 10bit data sequence which is a low-frequency component per data string and _{a 1, a 2, a 3} , a 4, a 5, a 6, a 7, a 8, a 9, a 10, CDS value = a _{a 1 + a 2 + a 3} + a 4 + a 5 ... + a 10.

Here, the values of 1 and 0 are obtained by substituting the values of a _{1 to} a ₁₀ in correspondence with 1 → −1. The above CDS value is 0
When Tmax is 5, the number of times that the same data is allowed to continue, that is, Tmax is 5, since there are 256 or more 10-bit combinations that satisfy 0 <CDS value, 0 <CD
8b by combination of 10-bit data of Tmax = 5 with only S value
It-10-bit conversion becomes possible.

Therefore, when converting the 8-bit recording data to 10 bits, if the CDS values of the 10-bit data string stored in the ROM table (33) are all CDS> 0, the 10-bit data string in the ROM table is Depending on whether the data is output as it is or inverted and output,
It is possible to vary the DSV value obtained by integrating the CDS value.

Here, in order to detect a value obtained by integrating the DC component of the 10-bit data string from the beginning of the data, that is, a DSV value, the data string is counted up from 1 to an up-count by a DSV counter (34) composed of, for example, an up-down counter.
If 0 → counting is continued, the DSV values (a) and (b) in the current data string can be detected.

Based on this, the data string from the ROM table (33) is output as it is (DSV> 0) or inverted (DSV <0) so that the DSV value changes sinusoidally with time and at a constant period with time. ) Or 8bi
When converting t data to 10 bits, a sinusoidal low frequency signal, ie, a pilot signal, can be multiplexed with the recording data (32), ie, digital data, within the modulation scheme.

Here, the sine-wave signal is synchronized with the drum rotation to define the phase relationship on the recording track with respect to the adjacent track, and the phase locked loop signal is used for the PG signal which is the drum rotation phase detection signal. (30)
Are generated by the two-phase pilot generation circuit (31) as a sinusoidal one-frequency pilot signal whose phase changes for each track.

When this is set to f ₀ the frequency of, for example, a pilot signal,
A 4 × f ₀ signal synchronized with the PG signal from the drum circuit is generated from the phase locked loop circuit (30). The two-phase pilot signal generation circuit (31) receiving this signal outputs
By switching the division timing for each track, for example, four mutually can generate a clock shifted by 90deg, by passing the band-pass filter having a center frequency f _0, the sine wave shifted in phase by one frequency The signal can be extracted.

If the oscillation frequency of the phase-locked loop circuit is N × f ₀ and the frequency division ratio is 1 / N, the pilot signals (A), (A), (B) can be generated.

In addition, as described above, even without using the phase locked loop circuit, it is also possible to generate the signal by preparing an oscillator triggered by a drum PG signal. At this time,
In order to record the pilot signal to be recorded so that the phase is inverted with respect to the track where no pilot signal is recorded every other track as shown in FIG. 6, for example, not only the frequency and phase of the signal but also the track It is related to the geometric configuration of the pattern.

For example, if the track pitch is T _P , the lead angle is R, and the recording signal wavelength is λ, the recording satisfying (2N−1) λ / 2 = 2T _P / tan (R) (Equation 1) (where N is an integer) Wavelength λ. When the pilot frequency is selected, the output from the phase locked loop circuit (30) in the figure or the recording of the pilot signal based on the continuous sine wave signal obtained as the output of the oscillator that can be triggered by the PG is automatically set at every other track. As shown in FIG. 6, the phase is inverted and recorded.

When the output of the phase locked loop circuit (30) or the oscillator that can be triggered by the PG is realized by the recording pattern in FIG. 6, the output is inverted every two tracks and input to the comparison command circuit (35). The selected wavelength corresponding to the above equation 1 needs to satisfy Nλ = 2T _P / tan (R) (Equation 2).

When an oscillator composed of a digital arithmetic circuit or the like capable of outputting an arbitrary phase every two tracks is used, a pilot signal of an arbitrary frequency that does not satisfy the above equation 1 or 2 can be used, for example, on a track pattern. As shown in FIG. 6, it is needless to say that recording can be performed such that the phase is inverted every other track as viewed from a track on which no pilot signal is recorded. Further, the data in the ROM table (33) is directly output (CDS> 0) or inverted (CDS <CDS) such that the output of the two-phase pilot signal generation circuit (31) and the output of the DSV counter (34) match. If 0) is selected and controlled, it is possible to multiplex a pilot signal in the modulation method with digital data.

When a pilot signal is multiplexed by this modulation method, the digital data and the pilot signal are correlated with each other (the pilot signal is inevitably multiplexed as a modulation algorithm). Waveform distortion due to multiplexing can be removed.

However, even with the above-described configuration, the azimuth effect of the head can hardly be expected in a low frequency region in the modulation spectrum, particularly in a pilot signal or the like. On the other hand, since the tracking control using the pilot signal utilizes the leakage (crosstalk) of the pilot signal from both sides, the frequency is intentionally selected to be less affected by the azimuth effect.

Therefore, crosstalk from the tracks adjacent to the pilot signal causes waveform distortion during demodulation of the reproduced digital data. However, since there is a correlation between the pilot signal and the reproduced digital data as described above, the waveform is distorted. Most of the distortion can be removed.

Also, the reproducing magnetic head performs a tracking operation due to crosstalk from both adjacent tracks, and when on-tracking, if a pilot signal is recorded so that the power level of the crosstalk becomes essentially zero, demodulation during demodulation can be performed. Waveform distortion can be considerably eliminated.

In particular, as described above, when the modulation means has an algorithm for generating a pilot signal, its frequency spectrum is as shown in FIG. 9, and the power level of the pilot signal can be recorded at a considerably high level. . Therefore, the tracking control signal (29) of the control system
The S / N ratio was good but the crosstalk was sometimes too strong.

However, in the above modulation method, the head (α),
In (β), for example, as shown in FIG. 6, pilot signals A1 and A2 are recorded every other track, and the pilot signals A1 and A2 are recorded.
However, by inserting signals 180 ° out of phase with each other at the same frequency, for example, in a track on which a pilot signal is not recorded, crosstalk components from both sides are offset by 180 ° from each other, and cancel each other out.
At the time of on-track, the influence of the crosstalk of the pilot signal becomes zero.

In the track on which the pilot signals A1 and A2 are recorded, no pilot signal is recorded on both sides, so that there is no influence of crosstalk. Also, since the pilot signal in its own track is created in the digital data modulation method at the time of recording as described above,
It does not become noise or disturbance to the attitude data on its own track.

At this time, for example, in digital recording / reproducing such as a digital VTR, a plurality of heads are mounted on one actuator because of a high bit rate. Therefore, at the time of reproduction, a head that traces a track on which a pilot signal is not recorded is tracked by crosstalk between both adjacent tracks.

For example, in FIG. 2, when the magnetic head α traces a track on which the pilot signal A1 is recorded and the magnetic head β traces a track on which no pilot signal is recorded, the bandpass filters (45a), (45a) Four
The output of 5b) is like the fifth α head output and β head output. Here, when the tracking position of the β head approaches the track side where the pilot signal A1 is written, the output of the β head reproduces the pilot signal A1 as a crosstalk signal, and approaches the track side where the pilot signal A2 is written. When the pilot signal A2 is reproduced as a crosstalk signal and is at the center position, since the pilot signals A1 and A2 are recorded in the same amplitude and in opposite phases, the crosstalk signals of A1 and A2 are canceled out, It goes to zero and no pilot signal is reproduced. Therefore,
When the output of the bandpass filter (45a) and the output of the bandpass filter (45b) are multiplied by the multiplier (46), when the β head is shifted to the track A1 side as shown in the output of the multiplier circuit in FIG. , And all negative voltages are obtained when the track is shifted to the track A2 side. The signal obtained by smoothing the output of the multiplier becomes a track error signal indicating the direction and amount of the track deviation of the β head, and based on the track error signal, the phase compensating circuit (47) performs the tracking system stability. In order to ensure quick response, phase compensation and gain compensation are performed, and the driver (44) drives the tracking actuator (5) on which the magnetic heads α and β are mounted, so that the magnetic field can be moved against track deviation and track bending. When the heads α and β follow, magnetic recording / reproducing of an extremely narrow track can be realized.

Further, when tracking is performed by an actuator equipped with three-channel magnetic heads of α, β, and γ as shown in FIG. 3, a pilot signal is recorded as shown in FIG.
By taking the differential of the pilot signals on the tracks on both sides of the 3ch track reproduced at a time (the pilot signals on the tracks on both sides are A1 and A2 when the pilot signal on the center track is B1) A signal of (A1-A2) K (where K is an amplification gain) can be obtained. Since A1 and A2 are signals having the same frequency and inverted phases as shown in FIG. 8, A1-A2 can obtain a signal having the same phase as A1 and a large signal amplitude. ) Is an AHz bandpass filter (45
a), the waveform is shaped by the hysteresis amplifier (52), and the AHz crosstalk signal from the head β extracted by the band-pass filter (45b) obtained from the center head β is subjected to the above-mentioned waveform shaping. By performing synchronous detection (for example, the output of the inverting amplifier (53) is selected when the waveform-shaped signal voltage level is high, and the output of the non-inverting amplifier (54) is selected when the signal voltage level is low), tracking similar to that in FIG. An error signal is obtained. After one rotation of the drum, the pilot signal frequency changes to BHz.

Although the generation of the track error signal in the synchronous detection circuit as described above has been described with reference to FIG. 3, the output of the band-pass filter (45a) as shown in FIG. Bandpass filter (45
It is needless to say that a track error signal similar to that of the synchronous detection circuit can be obtained by multiplying the output of b).

However, the magnetic head or the 3ch system is required to record the data by inverting the phase of the pilot signal on both sides of the 3ch track reproduced at a time in FIG. 3, for example, at the time of recording as compared with the 2ch system. Is possible. This is determined by the mounting accuracy of the three magnetic heads when three separate magnetic heads are mounted on the actuator (5). However, a three-channel magnetic head is formed by an integrated three-channel laminated head made by a laminating process. When configured, the recording gap position in the 3ch magnetic head is accurately defined, so that the phases of both pilot signals viewed from the center magnetic head (β head in the figure) are accurately inverted as described above. Because it can be recorded. However, in the case of 2 channels, both tracks of a track for obtaining a tracking signal (tracks for obtaining a crosstalk signal) do not record at the same time, and one track only has one actuator mounted on a drum. Since the recording is performed later, the phase relationship of the pilot signal may not be accurately maintained due to the drum rotation jitter or the like. However, when the pilot signal frequency is low (the recording wavelength is long), the phase shift due to the drum jitter for each track has a correlation for each track in a system in which only one actuator is mounted on the drum. Since the servo phase shift is sufficiently lower than the drum rotation frequency, there is only a slight
If the pilot signal wavelength is sufficiently larger than the phase shift amount caused by the drum jitter between tracks generated for each rotation, it is sufficiently realistic to perform tracking by the system of FIG.

Also, in the three-channel system shown in FIG.
In the case of a system equipped with only one actuator, the pilot signal frequency written on the center track and the pilot signal frequency written on both tracks of a three-channel track change every rotation, so the pilot required to generate a track error The signal frequency changes for each rotation of the drum. In FIG. 3, the comparator (50) determines which of the tracking pilot signal frequencies reproduced from the magnetic heads α and γ is AB. Then, the analog switches (51a) and (51b) are automatically switched to select a frequency required for the tracking operation.

A tracking system using such phase detection,
A system equipped with a 2ch magnetic head as described above or a 3ch
It has been described that the tracking operation can be realized in a system equipped with a magnetic head having four or more channels, but a tracking operation can be implemented with a configuration similar to a system having a three-channel system. Also, in a system equipped with a magnetic head of three or more channels, the phase of the recording pilot signal can be accurately written between adjacent tracks. It is needless to say that a tracking error can be obtained and a tracking operation can be realized even in the system performed in the same manner as the system shown in FIG.

As described above, the tracking operation is performed by the movable magnetic head by generating the track error, but the actual drum built-in actuator (5) includes
Since the movable range is limited as shown in FIG. 10, during the tracking operation, the low frequency component of the track error signal is reduced to a low frequency as shown in FIG. 4 so that the actuator (5) of the movable head does not exceed the movable range. It is necessary to feed back to the capstan motor by the passing filter (56). Thus, a tracking operation is performed by a capstan motor with respect to a low frequency component such as a track deviation, and a tracking is performed by an actuator (5) equipped with a movable head with respect to a relatively high frequency component such as a track bend.

In a system having a movable head of any number of channels as shown in the track pattern of FIG. 6 and FIG. 7, a crosstalk component due to a pilot signal from both tracks in an arbitrary track is not detected by a predetermined magnetic head. , When on-track to the center of any of the above tracks, both pilot signal components cancel out, or because nothing is written,
Since the crosstalk component in the low frequency region where the pilot signal is dominant becomes zero and is not reproduced, narrowing of the track can be realized particularly in digital magnetic recording in which waveform distortion due to the crosstalk component is a problem.

In the track pattern of FIG. 6, the polarity of the track error signal is always in the same direction, but in the case of FIG. 7, the polarity of the track error signal is inverted every two pairs. It is necessary to make the configuration such that it passes through an inversion circuit.

〔The invention's effect〕

As described above, the magnetic recording and reproducing apparatus according to the present invention
A rotating drum; an n-channel pair head (n is an integer of 2 or more) mounted on the rotating drum; and a modulation circuit for modulating a digital signal and outputting a digital modulation signal. By increasing or decreasing the CDS value (Code Word Digital Sum) representing the DC value per block, the DSV value (Digital Sum Variation) is periodically changed in synchronization with the rotation phase of the rotating drum and multiplexed into a digital modulation signal Generating the first and second pilot signals, and converting the digitally modulated signal to the n-channel pair so that the first and second pilot signals are alternately recorded on every other track on the magnetic tape. -The head is sequentially recorded, and at the time of reproduction, none of the first and second pilot signals of the n-channel pair head are recorded. Based on the crosstalk of the first and second pilot signals from the adjacent tracks mixed in the reproduction signal by the channel head corresponding to the rack, the shift between the channel head and the track is detected, and In a magnetic recording / reproducing apparatus for performing tracking control of a pair head, a signal detecting a deviation between a channel head and a track is fed back to a capstan motor for driving a magnetic tape through a low-pass filter, and n Since the channel pair head is also applied to an electromagnetically driven actuator that displaces the channel pair head in parallel with the rotation axis of the rotating drum, at the time of reproduction, the channel head generates either the first or second pilot signal. The track multiplexed with the digital modulation signal In this case, neither of the first and second pilot signals is recorded on both adjacent tracks, so that there is no influence of crosstalk of pilot signals from adjacent tracks.
Further, since the pilot signal and the digital modulation signal recorded on the track traced by the channel head are mutually correlated, the data waveform distortion due to the multiplexing of the pilot signal can be removed when demodulating the digital modulation signal. If the channel head traces a track on which neither the first nor the second pilot signal is multiplexed, the crossover of the first and second pilot signals multiplexed on both adjacent tracks is performed. Although the effect of talk is present, the pilot signal originally multiplexed on the track being traced by the channel head is not multiplexed, so that the effect of the pilot signal multiplexed on the track for tracking should be reduced as a whole. And the waveform distortion of the data due to the multiplexing of the pilot signal when demodulating the reproduced digital modulation signal is reduced.

Therefore, it is possible to realize a magnetic recording / reproducing apparatus for a high-quality digital signal capable of sufficiently suppressing the waveform distortion of the data of the digital modulation signal to be reproduced, and the waveform distortion is sufficiently suppressed. There is an effect that the reproduction becomes possible.

The pilot signal using the DSV method has a large crosstalk component with respect to off-track, and when performing high-density recording and reproduction by narrowing the track, if the channel head causes a track shift, the waveform of the data is generated by the crosstalk component. There is a possibility that distortion occurs partially.

However, according to the present invention, the low-frequency component of the signal that has detected the deviation between the channel head and the track is fed back to the capstan motor so that the tracking control operation is also performed by the capstan motor, and the channel head and the track are also controlled. Is applied to the electromagnetic drive actuator that displaces the head in parallel with the rotation axis of the rotating drum, so that low-frequency tracking deviation such as track deviation and relatively high frequency components can be eliminated. High-precision tracking control operation that can cope with any of the existing track bends is possible, and it is possible to prevent waveform distortion of data due to the crosstalk component of the pilot signal using the DSV method, and high-quality high-density recording And a magnetic recording / reproducing apparatus capable of reproducing the same. There is an effect that.

[Brief description of the drawings]

1 is a block diagram of a pilot signal recording circuit according to one embodiment of the present invention, FIG. 2 is a block diagram of a tracking control circuit according to one embodiment of the present invention, and FIG. 3 is a tracking error according to one embodiment of the present invention. FIG. 4 is a block diagram of a tracking control system according to an embodiment of the present invention, FIG. 5 is a signal timing chart in FIG. 2, FIG. 6 is a track pattern diagram in FIG. 7 is a track pattern diagram in FIG. 3, FIG. 8 is a recording state diagram of a pilot signal, FIG. 9 is a frequency spectrum diagram in the embodiment of the present invention, FIG. 10 is a sectional view of a rotating drum, and FIG. FIG. 12 is a block diagram of a tracking control circuit in a conventional embodiment, and FIG. 12 is a relationship diagram between a magnetic head and a recording track in the conventional embodiment. In the figure, (1) is a rotating shaft, (2) is a bearing, (3) is a lower drum, (4) is an upper drum, (5) is an electromagnetic actuator, (7) and (16) are magnetic heads, and (9). Is the reference oscillator, (10) is the counter, (11) is the flip-flop,
(12) and (22) are filters, (14) are mixers, (18) are switches, (17) is a division ratio control circuit, (20) is an amplifier,
(30) PLL circuit, (33) ROM table, (34) DSV
Counter, (36) logic circuit, (37) recording amplifier, (38) reproduction amplifier, (44) drive amplifier,
(45a) (45b) (47a) (47b) are bandpass filters,
(46) is a multiplier, (47) is a phase compensation circuit, (48) is a differential amplifier, (50) is a comparator, (51a) (51b) (55)
Is an analog switch, (52) is a hysteresis comparator, (53) is an inverting amplifier, (54) is a forward amplifier, and (56)
Is a low-pass filter, (57) is a motor driver,
(58) is a capstan motor. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] 1. A rotary drum, an n-channel pair head (n is an integer of 2 or more) mounted on the rotary drum,
A modulation circuit that modulates the digital signal and outputs a digitally modulated signal. During recording, the DSV value (Code Word Digital Sum) representing the DC value per block in the digitally modulated signal is increased or decreased to obtain the DSV value ( Digital Sum Variation) is periodically changed in synchronization with the rotation phase of the rotary drum to generate first and second pilot signals multiplexed on the digital modulation signal, and the first and second pilot signals are generated. The digitally modulated signals are sequentially recorded by the n-channel pair heads such that the signals are alternately recorded on every other track on the magnetic tape. And the second pilot signal is mixed with the reproduction signal of the channel head corresponding to the track on which neither is recorded. A magnetic recording / reproducing apparatus for detecting a shift between the channel head and the track based on crosstalk between the first and second pilot signals from the track and performing tracking control of the n-channel pair head. A signal that detects a deviation between the channel head and the track is fed back to a capstan motor that drives the magnetic tape through a low-pass filter, and the n-channel pair head is connected to the rotating shaft of the rotating drum. A magnetic recording / reproducing apparatus characterized in that the voltage is also applied to an electromagnetically driven actuator that displaces the magnetic recording / reproducing apparatus in parallel.