JPH03273517A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To enable the recording of high density with a narrowed track pitch by performing the recording in which the phase of a pilot signal is changed per track and controlling the position of a magnetic head in order to offset cross talk between the pilot signals with the phases regenerated from the respective adjacent tracks. CONSTITUTION:When an oscillation frequency of a phase locked loop circuit 30 is set as N X f0, while a frequency dividing ratio is set as 1/N, pilot signals A and B shifted in phase from each other by 360 deg./N can be generated. Then, pilot signals A1 and A2 are recorded by heads alpha and beta, for instance, every other track, and these pilot signals A1 and A2 are the same in frequency, but are shifted in phase from each other by 180 deg. Consequently, for example, on a track where the pilot signal is not recorded, since cross talk components from both adjacent tracks are shifted in phase by 180 deg., they are offset by each other, and at the time of on-track, influence of cross talk of the pilot signal becomes nil. By this method, the high density recording and reproducing is feasible at a narrow track pitch.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The second invention relates to a magnetic recording/reproducing device for recording on or reproducing information from a magnetic recording medium.

[Conventional technology]

FIG. 13 is a sectional view of a rotating drum used in a conventional magnetic reproducing device disclosed in, for example, Japanese Patent Application Laid-Open No. 63-173219. In the figure, a rotating shaft (1) is fixed via a bearing (2). attached to the drum. A rotating drum (4) is attached to a rotating shaft (1), and an electromagnetic actuator (5) is attached to this rotating drum (4).
is connected.

FIG. 14 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, Japanese Patent Laid-Open No. 59-68862.

FIG. 15 is a block diagram of a pilot signal generation circuit and a tracking error detection circuit for generating tracking/knocking errors in a conventional magnetic reproducing device disclosed in, for example, Japanese Patent Application Laid-Open No. 59-68862. ,(
9) is a reference oscillator (hereinafter abbreviated as O8C), (10
) is a presettable counter, (11) is a flip-flop, (12) is a filter, and (14) is a filter (12).
), a mixer (1) that adds the sine wave reference signal (20) outputted from the
5) is a recording/reproducing switch, (16) is a magnetic head for recording/reproducing, and (19) is a track switching signal (17).
) and a recording/reproduction switching signal (18) to control the frequency division ratio of the presettable counter (10), (22) is a low-pass filter that inputs the reproduction signal (21), (23) is a reference A mixer that adds the signal (20) and the regenerated pilot signal output from the low-pass filter (22), (24) an amplifier, (25) a dividing circuit, (
26g), (26b) is a band pass filter, (2
7g), (27b) is an envelope detection circuit, (2
8) are envelope detection circuits (27a), (27b
), and (29) is a tracking control signal output from the differential amplifier (28).

Next, the operation will be explained. When recording on a magnetic tape (T) as a magnetic recording medium, the frequency division ratio of the presettable counter (10) is switched by the control circuit (19) based on the track switching signal (17). The output of the counter (10) is further frequency-divided by a flip-flop (11), converted to a sine wave (pilot signal) by a filter (12), and then added to an information signal (13) and a mixer (14) for recording and reproduction. Changeover switch (15
) through the magnetic head (16)
to be recorded.

Each time the recording track changes, a track switching signal (17
), for example, f, ~ f4 as shown in Figure 14.
Four types of pilot signals can be recorded. At this time, the frequency of the pilot signal is the information signal (13
) and extracting the pilot signal, it is necessary to set the frequency so that the information signal (13) is not impaired, so it is selected, for example, from several tens of KHz to several hundred KHz.

Considering the frequencies of the pilot signals f, to f4 in FIG. 14 in the case of a four-frequency pilot system of a consumer 8 mm video tape recorder (VTR), f, +fA-f2.
f2+fB-f3...(1) f4 +fA=f3,
f, +fB-f4, the first
The magnetic head (16) in Fig. 5 drives the magnetic tape (T
), the pilot signal recorded along with the information signal (13) is also reproduced.

The pilot signal is extracted by a low-pass filter (22), but at this time, in addition to the scanning pilot signal, pilot signals of adjacent tracks (on both sides) are also extracted as crosstalk.

Since the frequency of the pilot signal of the adjacent track is sufficiently lower than that of the video signal, etc., even if azimuth recording is performed, there is almost no azimuth effect and the signal is reproduced as a large losstalk amount.

When the pilot frequency of the reference signal (20) written in the scanning track by the mixer (23) is added to the above reproduced pilot signal, the pilot signal due to crosstalk from both sides and the reference signal (20) are combined. A beat occurs during this period, and the beat frequencies of fA and fB in equation (1) are obtained.

For example, in FIG. 14, when playing the track on which the pilot signal of f2 is written, the pilot signals of f and f3 are also obtained as crosstalk, and when they are added by the mixer (23), ( 1) From formula, f2-f
+-fA, f2 Since f3=fB, the beat signals fA, f.

is obtained.

Next, this is extracted by band pass filters (26a), (26b) via an amplifier (24), a dividing circuit (25), and then an envelope detection circuit (27a), (2
7b), the magnetic head (7) in Fig. 14 detects f.
2, if there is even a slight shift toward f1, the beat signal f^ increases, and in the opposite case, the beat signal fB increases, so the tracking control signal is output as the output of the differential amplifier (28). (29) can be extracted.

The tracking control signal (29
) is subjected to phase compensation and gain compensation in order to maintain the stability and coordination of the control system at predetermined values, and then the rotary drum (4 ) is supplied to the actuator (5) in
By moving the magnetic head, closed-loop control is performed that enables tracking so that the magnetic head always traces a predetermined track.

With the closed-loop control described above, even if the recording track is deviated or curved with respect to the head trajectory of the reproducing device, the magnetic head can be made to follow the recording track so that the track deviation is eliminated.

[Problem to be solved by the invention]

Since the conventional magnetic recording and reproducing apparatus is constructed as described above, a tracking system with extremely narrow tracks is constructed in order to perform high-density recording and reproducing. In this case, a means for detecting track deviation with high accuracy is required, and generally, track deviation is detected by recording a low-frequency pilot signal as described above.

However, in the case of digital magnetic recording, general recording and reproduction signals have a wide power spectrum from components close to direct current to the highest recording frequency. It is not possible to create so-called gaps in frequency allocation outside the peripheral band.

Particularly in digital recording, it is impossible to insert a low-frequency pilot signal for tracking into a gap in frequency allocation, as is the case with current analog 8 mm VTRs.

However, in the case of digital recording as well, if the power level of the pilot signal recorded in the frequency range of the tracking pilot signal is sufficiently larger than the power level of the recorded signal obtained by modulating digital information, the tracking pilot signal will be used during playback. can be extracted using a band-pass filter or the like in the same way as in the conventional example.

However, as mentioned above, if the power level of the pilot signal is made too high relative to the recording/playback signal, which is video or audio information, the waveform distortion will increase when demodulated during playback, which will reduce the error rate of digital data. An increase occurs.

In particular, when recording by adding the modulated digital data and the tracking pilot signal in an analog manner before the recording amplifier, there is no correlation between the digital data and the pilot signal, so they are The signal becomes a mere disturbance signal.

In other words, in the case of digital audio recorders, digital video recorders, and information recording devices that record and playback using digital signals, the frequency spectrum of the recording and playback signals contains many low-frequency components due to the characteristics of digital recording.
When a low-frequency tracking pilot signal is added to the recording/reproduction signal and recorded, there is no correlation between the recording/reproduction signal and the pilot signal when demodulating the digitally modulated signal. Waveform distortion occurs and data error rate increases.

Therefore, if the power level of the pilot signal is lowered in order to reduce waveform distortion, the required S/N of the servo (tracking) detection signal cannot be obtained, making it impossible to apply the servo, and the recording density in the tracking direction of the tape decreases. There were problems such as loss of performance.

The present invention has been made to solve the above-mentioned problems.In multiplexing the pilot signal with the information signal, it is possible to minimize the waveform distortion during digital demodulation, and also to reduce the waveform distortion of the servo detection signal. It is an object of the present invention to provide a magnetic recording/reproducing device which can obtain a large S/N ratio and achieve high recording/reproducing density by narrowing the track pitch.

[Means to solve the problem]

The magnetic recording/reproducing device according to the present invention includes, during recording,
A modulation recording means that intentionally swings the low-frequency component of digital data at a certain frequency of a pilot signal using a desired modulation method, and records the frequency by changing the phase of the frequency for each track, and a magnetic head during reproduction. tracking control means for comparing the phases of the pilot signals recorded on tracks on both sides of a scanning track to be reproduced, and controlling the position of the magnetic head so as to cancel the crosstalk of the pilot signals from the tracks on both sides; It is equipped with the following.

[Effect]

Digital data in this invention is recorded by changing the low-frequency component of the pilot signal at a certain frequency and changing the phase of the pilot signal for each track, and controlling the magnetic head position by detecting the phase of this pilot signal. This reduces the data error rate,
Enables high-density recording and reproduction with a narrow track pitch.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In the figure, (30) is a PLL (phase locked loop) circuit for generating a pilot signal synchronized with the rotating drum, and (31) is a circuit for generating two-phase pilot signals (A) and (B) with opposite phases. (32) is the digitized recording data, (33) is a ROM table in which the conversion algorithm is determined based on the digital modulation method, and (34) is the ROM table (33) that modulates the data. In order to detect and output the low-frequency component element DSV values (a) and (b) J of the digital data, a DSV consisting of an up-down counter, etc.
counter; (35) is a comparison command circuit that compares the pilot signals (A), (B) with the DSV values (a), (b);
(36) is a logic circuit for serializing the digital data from the ROM table (33) and distributing it to two pairs of magnetic heads (hereinafter abbreviated as heads) J (α), (β), (37a), ( 37b) is a recording amplifier for supplying the recording current from the logic circuit (36) to the heads (α) and (β), and these constitute the modulation recording means (101).

(38a) and (38b) are reproduction amplifiers for amplifying reproduction signals from heads (a) and (β); (39a);
, (39b) is a bandpass filter for extracting a pilot signal for pitch control during recording, (4
0a), (40b) are detection circuits for checking the level of the pilot signal, (41B>, (41b) are sample and hold circuits for holding the peak level of the output of the detection circuits (40a), (40b), 42) is a differential amplifier for taking 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. A gain compensation circuit (44) is a drive amplifier for supplying a drive current to the actuator (5), and each section after the reproduction amplifier constitutes a tracking control means (102).

Next, the operation of the above embodiment will be explained. The above ROM table (33) shows that when the digital modulation method of the above embodiment device is an 8bit-10b i conversion method,
Contains the conversion table shown below.

Therefore, taking this 8bit t-10bi as an example of a conversion method, the CDS value, which is the low frequency component per data string, that is, the 10bit data string is converted into al+ 82+ a3+ "4+ a6+
If a6* a7as, ag, a 1 degree, CDS value - a, ten a2 + a3 + a4 + 85...+
al.

becomes.

Here, each value of 1 and 0 is determined by corresponding to 1→-1 and substituted into the above-mentioned 81 to alo.

When considering a CDS value other than O, and assuming that the number of consecutive pieces of the same data, that is, Tmax, is 5, the number of 10-bit combinations where 0<CDS value is 2.
Since there are 56 or more, Tmax is 0<CDS value only.
By combining 10 bit data of =5, 8 bit-
10-bit conversion becomes possible.

Therefore, when converting the recorded data consisting of 8 bits to 10 bits, the 10 bits stored in the ROM table (33)
If all the CDS values of the bit data string are configured with CDS>O, the CDS value will change from the beginning of the data depending on whether the 10-bit data string in the ROM table is output as is or inverted. It becomes possible to vary the DSV value obtained by integrating.

In order to detect the integrated value of the DC component of the 10-bit data string from the beginning of the data, that is, the DSV value, the
If the SV counter (34) continues to count up the data string by 1-up and then count down from 0 to 0, the DSV values (a) and (b) in the current data string can be detected.

Based on this, the ROM table (33
) by selecting whether to output the data string as is (DSV > 0) or invert it and output it (DSV < 0). The low frequency signal or pilot signal can be multiplexed onto the recording data (32) or digital data.

Here, the sinusoidal signal is synchronized with the rotation of the drum to define the phase relationship on the recording track with respect to the adjacent track, and is the rotational phase detection signal P of the drum.
This signal is phase-locked with respect to the G-multiplied signal by the phase-locked loop circuit (30), and is generated by the two-phase pilot generation circuit (31) as a sinusoidal one-frequency pilot signal whose phase changes for each track. .

This means, for example, that the frequency of the pilot signal is f. When you close it,
A phase-locked loop circuit (30) generates a 4×f0 signal synchronized with the PG multiplied signal due to drum rotation.

A two-phase pilot signal generation circuit (31
), by switching the timing of frequency division by 4 for each track, it is possible to generate, for example, four clocks shifted by 90 degrees from each other, and the center frequency f. By passing the signal through a bandpass filter, it is possible to extract a sine wave signal whose phase is shifted by one frequency.

Furthermore, if the oscillation frequency of the phase-locked loop circuit is NXfo and the frequency division ratio is 1/N, pilot signals (A) and (B) whose phases are shifted by (360 deg/N) from each other with the above configuration are obtained. can be generated.

Furthermore, the data in the ROM table (33) is output as is (CDS>Q) or inverted (CDS< Q) By selecting and controlling the method, it is possible to multiplex the pilot signal within the modulation method onto digital data.

When pilot signals are multiplexed using this modulation method, the digital data and pilot signals are correlated with each other (pilot signals are inevitably multiplexed as a modulation algorithm), so the demodulation circuit when reproducing digital data Waveform distortion caused by multiplexing can be removed.

However, even with the above configuration, almost no head azimuth effect can be expected in the low frequency region of the modulation spectrum, especially in pilot signals and the like. On the other hand, since tracking control using pilot signals utilizes the leakage (crosstalk) of pilot signals from both sides, the frequency is intentionally selected to be less affected by the azimuth effect.

Therefore, crosstalk from tracks on both sides of the pilot signal causes waveform distortion when demodulating the reproduced digital data, but since there is a correlation between the pilot signal and the reproduced digital data as described above, the waveform Distortion can be removed to some extent.

Next, the reproducing magnetic head performs a tracking operation due to crosstalk from adjacent tracks, and if the pilot signal is recorded so that when on-track, the power level of the crosstalk becomes zero in principle, then during demodulation waveform distortion can be significantly removed.

In particular, as mentioned above, when the modulation means has an algorithm that generates a pilot signal, its frequency spectrum ram is as shown in Figure 2, and it is possible to record a considerably high power level of the pilot signal. can. For this reason, although the S/N ratio of the tracking control signal (29) of the control system was good, crosstalk was sometimes too strong.

Therefore, in the above modulation method, the head (α) (β)
For example, as shown in FIG. 3, pilot signals AI and A2 are recorded every other track, and these pilot signals AI,
By inputting signals with A2 having the same frequency and a phase shift of 180 degrees, for example, in a track where no pilot signal is recorded, the crosstalk components from both sides are offset by 180 degrees from each other, so they cancel each other out and turn on. During tracking, the influence of pilot signal crosstalk becomes zero.

In the tracks where the pilot signals AI and A2 are recorded, no pilot signals are recorded on either side, so there is no influence of crosstalk. Further, since the pilot signal in the own track is generated within the digital data modulation method during recording as described above, it does not cause noise or disturbance to the attitude data in the own track.

At this time, in digital recording/reproduction such as digital DTR, for example, a plurality of heads are mounted on one actuator because the bit rate is high. Therefore, during reproduction, a head tracing a track on which no pilot signal is recorded is tracked by the tarostalk of the adjacent tracks on both sides.

This tracking is performed by detecting the phase shift of the above-mentioned crosstalk, and the reproduced output from the tracking head that traces the track where the above-mentioned pilot signal is not recorded is filtered through a band-pass filter whose center frequency is the frequency of the pilot signal. After the rotation reference signal is extracted from the drum motor, synchronous detection is performed using a clock equal to the frequency of the pilot signal obtained from the rotation reference signal extracted from the drum motor. It becomes possible to detect whether there is a degree of deviation.

In the input of the above-mentioned synchronous detection, if the tracking head shifts to the right, for example, the phase of the pilot signal recorded on the right track will appear as crosstalk, and if it shifts to the left, the phase will be 180 deg relative to the crosstalk.
By obtaining the g-inverted signal, the above-mentioned detection becomes possible using the synchronous detection circuit.

The tracking error signal is inverted and output every rotation of the drum, but whether or not the track control signal is inverted can be determined by determining the phase of the pilot signal from the head that traces the track where the pilot signal is recorded from the rotation reference. Recognize.

As described above, we have shown a basic recording and tracking method for tracking pilot signals that is free from the effects of pilot signal crosstalk.However, in the case of the above modulation method, there are differences due to wow and flutter in the rotation of the drum motor during recording and playback. Similarly, the timing of synchronous detection may shift due to temperature characteristics of the tape, stretching and shrinking due to changes over time, etc., and normal tracking may not be performed.

Therefore, as shown in Fig. 4, a pilot signal with a frequency of AHz is recorded with the phase shifted by 180 degrees every other track, and similarly a pilot signal with a frequency of BHz is shifted in phase by 1806 degrees every other track, and the above frequency AHz is recorded.
By recording the pilot signal in the gap between the tracks on which the pilot signal is written, tracking can be performed.

A circuit configuration for performing such a tracking operation is shown in FIG. In FIG. 5, the same parts as in FIG. 1 are given the same reference numerals, and redundant explanation will be omitted. (45)
, (46) is a bandpass filter for extracting the tracking pilot signal from the reproduced signal;
7) is a hysteresis comparator for generating a reference clock from the pilot signal that serves as a reference for the synchronous detection circuit (52); (48) is a phase comparator for generating a phase error in the PLL (30); (49) is PLL
(30) is a loop filter for stabilizing the loop in (50) is a voltage controlled oscillator that changes the oscillation frequency based on the output of the loop filter (49), (51) is a voltage controlled oscillator (50) an N frequency divider for multiplying the output of the hysteresis comparator (47) by N;
(52) is a bandpass filter (46) for extracting the other pilot signal for tracking.
) is a synchronous detection circuit for synchronously detecting the output of the PLL circuit (30) based on the output of the PLL circuit (30), (53) is a synchronous detection circuit (
(52) is a normal rotation amplifier, and (54) is a synchronous detection circuit (52).
) is the inverting amplifier inside, and (55) is the normal amplifier (53).
) and the inverting amplifier (54) to the PLL circuit (30).
The switch (56), which is switched based on the output of the tracking control system, is a compensation filter inserted to ensure stability and coordination of the tracking control system.

Next, the operation of the embodiment shown in FIG. 5 will be explained.

The head (α) is extracted by a bandpass filter (45) whose center frequency is the frequency BHz written in the track being traced, and a clock with a frequency of BHz is generated via a hysteresis comparator (47). .

The phase-locked loop circuit (30) has the above frequency BH.
Multiply z by N to create the same frequency AHz as the crosstalk pilot signal (A1). For example, since the pilot signal is recorded as shown in Fig. 6, the pilot signals (A1) and (B1) are phase-synchronized, so the pilot signal (B1) is passed through the phase-locked loop circuit (30). The created reference signal with a frequency of AHz has a frequency A obtained as crosstalk from both sides.
The relationship is synchronized with the Hz pilot signal A1.

The above will be explained in detail with reference to the timing chart diagram of FIG.

In FIG. 7, (62) is the crosstalk component of the pilot signal (A1) reproduced from the head (β) in FIG. 6, (63) is the crosstalk component of the pilot signal (A2), and (64) is the crosstalk component of the pilot signal (A2). Bandpass filter (45)
, (46) above pilot signal (A1) extracted from
, (A2), (65) is a pilot signal (B1) reproduced from the head (β) and extracted from the bandpass filter, (66) is a phase-locked loop of the above signal (65). After multiplying by 3 in the circuit,
A reference clock created by dividing the frequency by 2, (67) is a signal obtained by synchronously detecting the synthesized signal (64) with the reference clock (66), and (68) is a signal obtained by using the compensation filter (56) to detect the signal (6).
7) is a smoothed signal.

In other words, the pilot signal (B1) with a frequency of BHz written on the track being traced by the head (α) is changed to a frequency of AHz by the phase-locked loop circuit (30).
A pilot signal (64) with a frequency of AHz is generated at the reference clock (66) of
By performing synchronous detection using the reference clock (66) in the synchronous detection circuit (52), the direction and amount of the track deviation can be extracted as in the signal (67).

By smoothing this signal (67) with a compensation filter (56), a signal (68) is extracted and fed back to the actuator (5) via a drive amplifier (44), so that the head can avoid track deviation or track bending. A control system that can follow this can be constructed.

As described above, we have demonstrated a modulation method that can synchronously detect crosstalk from both sides using a reference clock recorded on a magnetic tape and cope with the expansion and contraction of a magnetic tape for tracking. Even with this modulation method, the phases of pilot signals on both sides are always shifted from each other by 1 gOdeg, so that when on-track, there is no influence of crosstalk due to pilot signals in any head.

However, the phase relationship between the pilot signals on both sides of the tracking head (α) may deviate due to drum jitter (rotation fluctuation) every other revolution.

Therefore, as shown in Figure 8, three heads (α), (β),
(γ) is mounted on one actuator, and the azimuth angle is 3 when each head is (α), (β), and (γ).
For example, the pilot signal is recorded at every other track at a frequency of AHz and the phase is changed. The drum and capstan rotation time can be calculated using the circuit configuration shown in Figure 9 by writing a signal with a phase shift of 180 degrees at a frequency of BHz and a phase shift of 180 degrees at every other track between the above AHz tracks using three bare heads. It is possible to perform tracking that is completely unaffected by fluctuations and has zero crosstalk effects from both sides.

FIG. 9 shows a circuit configuration for performing the above-mentioned tracking operation, and the same parts as in FIG. 5 are given the same reference numerals and redundant explanation will be omitted. In FIG. 9, (57) is a phase-locked loop circuit for multiplying or dividing the signal obtained from the output of the band-pass filter (45), and (58) is the signal obtained from the output of the band-pass filter (46). (59) is a changeover switch for switching the output of the two phase-locked loop circuits (57) and (58), and (60) is a phase-locked loop circuit for multiplying or dividing the frequency. A changeover switch is used to change the output of the pass filters (45) and (46), and (61) inputs the PG multiplied signal.
one switch (59).

This is a monomulti circuit for adjusting the switching timing of (60).

For example, among the three heads (α), (β), and (γ), if the center head (β) is tracing a track on which a pilot signal with a frequency of BHz is written, then the frequency BHz is the center frequency. The signal extracted by the band-pass filter (46) with a center frequency of AHz is multiplied by N in a phase-locked loop (58) to generate a reference clock with a frequency of AHz. ) to extract the crosstalk on both sides, and perform synchronous detection in the synchronous detection circuit (52) using the reference clock of the center frequency AHz to extract the direction and amount of track deviation in the same manner as in FIG. You can track and provide feedback.

However, in this case, the changeover switch (59).

(60), the track traced by the center head (β) is a track in which a pilot signal with a frequency of BHz is written for each trace in the figure, or a track with a frequency of AH
z track, so there are phase-locked loop circuits (57) and (58) that convert a pilot signal with a frequency of BHz to a frequency of AHz to create a reference clock, and those that convert a frequency of AHz to a frequency of BHz. In other words, it is switched for each trace. The bandpass filters (45) and (46) for extracting crosstalk signals before the synchronous detection circuit (52) are also switched in the same manner.

With the above configuration, the three heads (α) and (β) are rigidly fixed.

Since tracking is performed during playback using the pilot signal written in (γ), there is no influence of rotational fluctuations, and there is no influence of losstalk or tape stretch as described above.

The same effect can be achieved by arranging two or more actuators equipped with the three heads (α), (β), and (γ) on the drum. Furthermore, each head (α), (β), (
(a) Subtract the azimuth angle of γ) (β) < (γ) or (
By setting α)>(β)>(γ), the azimuth effect due to track bending during recording is currently traced at both ends of the three heads relative to the recording pattern of the head (γ) traced previously in the figure. For each of the pattern of the head (γ) and the pattern of the head (α) to be traced next relative to the pattern of the head (γ) currently being traced, the amount of 1 (azimuth angle of head α) - (azimuth angle of head γ) 1 is applied. This makes it possible to record even if the track is slightly curved.

In the pattern configurations shown in Figures 3, 4, and 8 above, in order to accelerate the pull-in of the conventional phase-locked loop circuit, the lower end of the track is set as a reference point as shown in Figures 10, 11, and 12. By providing a pilot signal recording area for clock generation, it is possible to first draw in the phase-locked loop circuit and then use the output of the phase-locked loop circuit as a reference signal for synchronous detection, thereby speeding up the drawing in of the tracking operation.

Furthermore, in FIGS. 10, 11, and 12, at the lower end of the track pattern, although nothing is currently recorded on the track, the crosstalk signal from the previously traced track is reproduced. For example, in the case of two heads, as shown in FIG. 1, during recording, temporary reproduction is performed at the lower end of the track where nothing is recorded,
Pass the crosstalk signal of the previous track through a bandpass filter (
39a) and (39b), and the amplitude at that time is extracted by the detection circuit (40). Then, after being held by the sample and hold circuit (41), every other trace is compared by the differential amplifier (42), and the actuator height is controlled so that the amplitude difference is equal for each trace. Even in a type in which two actuators are mounted in the rotating drum, it is possible to eliminate head step deviation during recording.

Note that the pilot signal is generated using 3 bits to 10 bits.
The explanation has been given using conversion as an example, but even in the case of ternary recording, data 1 can be converted to +1 . 0 to 0. It goes without saying that it is possible to create a pilot signal by counting the DSV value with -1 = 1 and controlling this DSV value in a sinusoidal manner, and it can also be realized with a similar configuration.

We have also shown a method that can generate a pilot signal within a digital modulation algorithm, but for example, a sine wave signal with a phase shift is generated independently of the recording data, and both are added in an analog manner before the recording amplifier described above. However, it goes without saying that the crosstalk of the pilot signal of the scanning track head becomes zero and the same effect can be achieved.

〔Effect of the invention〕

As described above, according to the present invention, the low-frequency component of digital data is changed at a certain frequency of a pilot signal, the phase of the pilot signal is changed for each track, and the phase is recorded and reproduced from tracks on both sides of the track. Since the magnetic head position is controlled to cancel this pilot signal crosstalk, it is possible to obtain a high-quality signal without the influence of pilot signal crosstalk, and the data error rate is low. This has the effect of narrowing the track pitch and enabling higher density recording.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a magnetic recording/reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a frequency spectrum diagram, and FIG.
1 is a track pattern diagram of the device shown in FIG. 1, FIG. 4 is a track pattern diagram of the device shown in FIG. Fig. 7 is a timing chart diagram, Fig. 9 is a track pattern diagram by the device,
9 is a block diagram of another tracking circuit according to the present invention, FIG. 10 is a detailed diagram of the track pattern shown in FIG. 3, FIG. 11 is a detailed diagram of the track pattern shown in FIG. 4, and FIG. 12 is a detailed diagram of the track pattern shown in FIG. Detailed diagram of the track pattern shown in Figure 8,
FIG. 13 is a longitudinal sectional view of a rotating drum, FIG. 14 is a relationship between a magnetic head and a recording track, and FIG. 15 is a block diagram of a conventional magnetic recording/reproducing apparatus. In the figure, (101) is a recording means, and (02) is a tracking control means. In the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] When storing, the phase of a pilot signal generated in synchronization with the rotating drum is inverted, the phase-inverted pilot signal and digital data are input, and the digital data is converted by a desired modulation method. Modulation storage means for changing the low frequency component of the pilot signal at a certain frequency and changing the phase for each track and storing the same; and at the time of reproduction, adjacent tracks on both sides are reproduced from a magnetic head tracing a scanning track. tracking control means for comparing the phases of the pilot signals recorded on the tracks and controlling the position of the magnetic head so as to cancel the crosstalk of the pilot signals from adjacent tracks on both sides.