JPH0695378B2 - Position information detection signal generation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a magnetic recording / reproducing apparatus which is used for positioning an information recording / reproducing head so as to face a desired track formed on a magnetic medium. It relates to a method for generating an information signal.

[Conventional technology]

Among a plurality of tracks, such as a magnetic disk or a floppy disk, which records a large amount of information, on which a magnetic head is formed on a recording medium, in a device that positions a track facing a desired track, the track is increased in order to increase the recording capacity. It is effective to make the density of magnetic heads high density, and for this purpose the magnetic heads must be accurately positioned. This positioning is for servos to position the magnetic heads for each track on the recording medium. When a signal is written and data information is recorded / reproduced, a position information signal for controlling the position of the magnetic head is generated based on this servo signal, and in response to this signal, the magnetic head is transferred to the adjacent track. The control is performed in such a manner that the two halves face each other.

Therefore, since the recording / reproducing of the data information is performed after this positioning control is performed, the data information is recorded at a position deviated from the servo signal by half the track width in the track width direction. Various methods such as tribit, dibit, and modified dibit have been proposed as methods for writing the servo signal used for this purpose.

Figure 9 shows a recording state in the case of Toribitsuto, are positioned adjacent the track 1 ₁ to 1 ₄ having a width is W, the above information to each track 1 ₁ to 1 ₄ in the direction for recording and reproducing A sync bit 2 having a period T is recorded, and odd-numbered tracks (hereinafter referred to as odd-numbered tracks) 1 ₁ , 1 ₃ are position control bits (hereinafter, referred to as "position control bits") at a position T / 3 away from the sync bit 2 in the information reading direction. This bit in an odd number track is referred to as an odd number position bit) 3 is recorded, and the even numbered track (hereinafter referred to as an even numbered track) 1 ₂ , 1
_A position control bit 4 (hereinafter, this bit in an even numbered track is referred to as an even numbered position bit) 4 is recorded at a position 2T / 3 away from the sync bit 2 in the information reading direction. It is polar.

FIG. 10 is a waveform diagram when the magnetization pattern of FIG. 9 is read out, and FIG. 10A shows a readout waveform when the magnetic head is located on the odd-numbered tracks 1 ₁ and 1 ₃ and shows a Lorentz-shaped arc. The waveform is read at time t = 0, t = T / 3, t = T according to the magnetization polarity. (B) is a read waveform when the magnetic head is located between the even-numbered tracks 1 ₂ and 1 ₄ and the odd-numbered tracks 1 ₁ and 1 ₃ at time t = 0, t = T / 3, t =
Similarly, at 2T / 3, t = T, it is read as a Lorentz-like isolated waveform. (C) shows a read waveform when the magnetic head is positioned on the even tracks 1 ₂ and 1 _{4. At} time t = 0 and t = 2T / 3, t = T, similarly, the Lorentz-shaped arc waveform is read. Has been issued.

FIG. 11 shows a gate signal used to extract a position signal indicating the relative positional relationship between the magnetic head and the track from the waveforms of FIG. 10, and FIG. 11 (a) shows T / T where the odd position bit 3 exists. An odd-numbered gate signal that keeps "H" (high level) for a predetermined time before and after, centering around 3, and not including the read waveforms of the sync bit 2 and the even position bit 4,
(B) is an even gate signal centering on 2T / 3 where the even position bit 4 exists, and maintaining "H" for a predetermined time before and after depending on the extent that the read waveforms of the sync bit 2 and the odd position bit 3 are not included, They generate a reference pulse by slicing a read waveform of a sync bit 2 (this bit is always read as a constant level regardless of the track position of the magnetic head) generated at every cycle T by a negative level. , Based on this, a phase locked loop,
It is generated by a combination of delay elements and logic circuits.

The signal read from the track 1 ₁ to 1 _4, even gate signal (a), the odd gate signal (b) is applied to two analog switch which is turned on during the "H", the other analog Since the read waveform of the odd position bit 3 is sent to the output of the switch and the read waveform of the even position bit 4 is sent to the output of the other analog switch, each output of each analog switch is provided correspondingly. each peak value in the peak hold circuit is held, it is assumed that shown in Figure 12 in accordance with the relative positional change of the magnetic head and the track ₁ 1 ~1 ₄ (a), signals corresponding to the odd position bits 3 by a dotted line As shown, the signal corresponding to even position bit 4 changes as shown by the solid line.

Therefore, the position detection signal shown in FIG. 12 (b) can be obtained by obtaining the difference between these two peak hold output signals.

Therefore, this position signal (b) becomes zero when the magnetic head is positioned in the middle of the even and odd tracks, and becomes a triangular wave signal indicating either positive or negative level depending on the deviation to either one. The magnetic head is positioned by controlling the position signal so that the level becomes zero.

As another method, as shown in FIG. 13, a sine wave having a frequency of _{1 is applied to} the odd-numbered tracks 1 ₁ , 1 ₃ and the even-numbered tracks 1 ₁ , 1
₄ has a so-called dual frequency system for recording a sine wave of frequency ₂ different from frequency _{1. In} this case, the read waveform of the magnetic head is given by the following equation.

_{S (t) = Asin2π 1 t} + Bsin2π 2 t ...... (1) Thus, when multiplying two Rifuarensu signal indicated by the following equation to S (t) to each _{individual, r 1 (t) = sin2π} 1 t, r2 (t ) = sin2π ₂ t ......
(2) The signal of the following equation is obtained.

_{S (t) r 1 (t} ) = A / 2- (A / 2) cos4π 1 t + (B / 2) cos2π (1 - 2) t - (B / 2) cos2π (1 + 2) t ...... (3) S (t) r2 (t) = B / 2- (b / 2) cos4π 2 t + (A / 2) cos2π (1 - 2) t - (A / 2) cos2π (1 + 2) t ...... (4) was but connexion, these signals ₍₁ - ₂₎ through the filter of the lower cut-off frequency, extracting a low frequency component, (1) formula a, to B, a / 2 and B A DC component having a value of / 2 is obtained, and if the difference between these two DC components is obtained, the
The position signal shown in FIG. 12 (b) is obtained.

[Problems to be solved by the invention]

However, in the method of FIG. 9, the position information of the even-numbered tracks 1 ₂ , 1 ₄ and the odd-numbered tracks 1 ₁ , 1 ₃ are separated by time division, and by the method of FIG. 13, they are separated by frequency division. Therefore, the time division method requires an accurate timing signal generation circuit for reproducing the position signal, and the frequency division method requires a circuit and a multiplication circuit that generate an accurate reference signal having the same frequency and phase. However, when configuring these circuits, if the device is large-scale, the mounting space, price, etc. are not particularly big problems, but in the case of a low-priced small-sized disk device using a small-diameter magnetic recording medium, the mounting space is small. It ’s going to be huge and expensive,
It causes a problem that economic efficiency deteriorates.

[Means for solving problems]

In order to solve the above problems, the present invention is configured by the following means.

That is, in the position information detection signal generating method described above,
For each of the odd-numbered track and the even-numbered track, there is a period of a half-value width of the Lorentz-shaped upright waveform of 0.05 to 0.7 times from that,
In addition, recording is performed so that two bit patterns that do not interfere with each other can be read out, and the difference between the peak-held read signal and the peak-held inverted signal of the read signal is determined. .

[Action]

Therefore, the object can be achieved with a simple circuit configuration including a peak hold circuit and a subtractor.

〔Example〕

Hereinafter, the details of the present invention will be described with reference to the drawings illustrating examples.

FIG. 1 is a diagram showing a magnetization state of a magnetic medium. Reference numerals 5 and 6 are first and second magnetization sections formed in odd-numbered tracks 1 ₁ and 1 ₃ , and 7 and 8 are even-numbered tracks 1 ₂ and 1 _{4 respectively.} The third and fourth magnetized sections formed on the magnetic poles are magnetized by the order of N pole to S pole in the direction of recording / reproducing the signal indicated by the arrow, and the magnetized sections 6 and 7 are opposite to this. The length of the signal recording / reproducing direction of the magnetizing sections 5 and 7 is defined as approximately half of the half-width of the Lorentz arc vertical waveform described later, and the magnetizing sections 6 and 8 have the length of the signal recording / reproducing direction of the Lorentz arc. defined as approximately 5 times the standing wave half width, there as a signal read from the same track is not cause mutual interference, the even tracks 1 ₂ these magnetized sections 5-8 disposed by _printing, 1 ₄ and the odd tracks 1 _1, 1 ₃ and the magnetization-ku, the last part of the magnetization section 5 The magnetic medium 9 is formed by arranging the foremost part of 7 or the foremost part of the magnetized section 5 and the last part of the magnetized section 7 at positions where they are read out at the same timing in the signal recording / reproducing direction and alternately adjacent to each other. .

FIG. 2 shows the recording and reproducing conditions for each track in FIG. 1, and (a) shows the odd track 1 of rank 2k-1 (where k is a positive integer) and the rank adjacent to it from FIG.
It is the figure which extracted even track 1 of 2k and each magnetization section,
In order to form the magnetized sections 5 and 6 shown in the odd numbered track 1 (2k-1), magnetization is performed by the signal shown in FIG. 2 (b) to form the magnetized sections 7 and 8 shown in the even numbered track 1 (2k). Can be magnetized by the signal shown in FIG. 2 (c),
If the signal read out from the information recorded by this when the magnetic head 10 is located on the odd track 1 (2k-1) is shown (d), the odd track 1 (2k-1) and the even track 1 are shown.
If the read signal when the magnetic head 10 is evenly opposed to both (2k) is shown (e), if the read signal is shown when the magnetic head 10 is located on even-numbered track 1 (2k), then (f) And the signal (e) is an odd track 1
The 2-bit pattern that changes from positive to negative due to (d) when read from (2k-1) and even track 1 (2
It is the sum of the two bit patterns that change from negative to positive due to (f) when read from k).

Therefore, the waveform shown in (d) is obtained when the magnetic head 10 is located on the odd numbered track 1 (2k-1), and the waveform shown in (f) is obtained when it is located on the even numbered track 1 (2k). However, the magnetic head 10 has an odd number of tracks 1 (2k
-1) and even-numbered track 1 (2k) evenly face each other, as shown in (e), a waveform having approximately half the amplitude of the waveform shown in (d) and a waveform shown in (f). On the other hand, a composite wave with a waveform having an amplitude of about half is obtained, and in this case, a signal having a negative peak is obtained.

FIG. 3 is a block diagram of a circuit for generating a position information detection signal from the signal of FIG. 2, 11 is a differential amplifier for sending non-inverted output and inverted output, 12 is a peak hold circuit, and the same circuit 11 is summer to the structure shown in FIG. 4, 12 ₁
Is a diode, 12 ₂ is a capacitor, and 12 ₃ is a constant current circuit.

FIG. 5 is a waveform diagram showing the operating condition. The signal read from the odd numbered track 1 (2k-1) in (a) is the shortest magnetization reversal section 5 in the signal recording / reproducing direction, as described above. When the half-width of the arc-shaped standing waveform is approximately half, the Lorentz-shaped standing waveforms read from the respective magnetization reversal portions interfere with each other (b), and the magnetic head 10 has an odd number of tracks 1 (2k-1). Since the signal read out evenly when facing the even track 1 (2k) is the one shown in FIG. 6C, if the positive and negative peak values in FIG. The positive peak value is 1/2 of 2 and is 1, and the negative peak value is 2 for both tracks.
10 is odd track 1 (2k-1) and even track 1 (2k)
When the waveforms are evenly opposed to and, the peak value of the positive portion is about one half of the peak value of the negative portion.

FIG. 6 is a diagram showing these situations. As shown in FIG. 6A, the tracks arranged with the magnetization reversal section 5 having a distance L of about half of the half-width of the Lorentzian arc vertical waveform are adjacent to each other. A magnetic medium 9 is formed, and a magnetic head is formed on the magnetic medium 9.
When 10 is displaced in the W width direction of the track, the magnetic head 10
The signals read from are shown in (b) to (f).

That is, (b) to (f) are magnetic heads shown in (a).
When 10 is located on the central track, y = 0, and with this as a reference, the magnetic head 10 is displaced by 1/4 of the track width W, and y = W / 2, W / 4,0,- It corresponds to each condition when connecting to W / 4 and W / 2.

Here, the positive peak value V ₊ and the negative peak value V _{− in} FIG. 6 are given by the following equations as is apparent from (b) to (f).

I.-W / 2 ≦ y ≦ 0 when _{V + = 2M ...... (5)} V - = M · y / (W / 2) + 2M ...... (6) when the II.0 ≦ y ≦ W / 2 _{V + = -M · y / (} W / 2) + 2M ...... (7) V - = 2M ...... (8) FIG. 7, each peak value V _+, V _- illustrates the situation when hold And (a) shows a characteristic in which a positive peak value is held from the waveform read from the magnetic head 10 when the magnetic head 10 is displaced in the track width W direction,
(B) shows the characteristic in which the positive peak value is held from the signal obtained by inverting the phase of the read signal, and if the result of the operation for obtaining the difference between the signal shown in (a) and the signal shown in (b) is shown. It becomes the characteristic of (c), and this characteristic is given by the following equation when the position of the magnetic head 10 is y and the level of the output signal is Vp.

Vp = V ₊ -V _- =-(2M / W) ・ y (9) That is, in the equation (9), the output Vp becomes zero at y = 0 when the magnetic head 10 is in the normal positioning state, In addition, the slope becomes a straight line indicated by 2M / W.

Therefore, if the characteristic shown in FIG. 7 (c) is obtained, the magnetic head 10 is accurately positioned on each track by using Vp as a position detection signal and controlling it in the direction of zero. be able to.

Therefore, when the servo signal recorded as shown in FIG. 1 is read by the magnetic head 10 and the read signal is processed by the circuit of FIG. 3, the signal sent from the peak hold circuit 12 is shown in FIG. It becomes the one of (a), (b),
When (a) is applied to the non-inverting input terminal of the differential amplifier 11 and (b) is applied to the inverting input terminal, and the difference between them is obtained by the differential amplifier 11 as a subtractor, FIG. 7 (c) is obtained. The signal shown is obtained.

In the magnetization sections 5 and 7 shown in FIG. 1, the length in the signal recording / reproducing direction is approximately half of the full width at half maximum of the Lorentzian arcuate waveform, but in reality, it depends on the material of the parts used and the structure of the equipment. Therefore, there is an optimum value, and in general, when this length is 0.5 to 0.7 times the half-value width of the Lorentzian arcuate waveform, the ratio between the positive and negative peak values of the read signal becomes maximum. The length may be selected according to the situation.

Further, the above is the case of the horizontal recording using the horizontal recording medium and the ring head as the recording medium 9 and the magnetic head 10. However, the vertical recording using the perpendicular recording medium and the perpendicular recording head such as the single pole head may be used. Similarly, in this case, the magnetization pattern for perpendicular recording is as shown in FIG. 8 when viewed from one surface of the magnetic medium, and the opposite surface, that is, the surface on the back side of the paper is magnetized to the opposite polarity to that in the figure. The waveforms obtained by reading these magnetization states with a perpendicular recording head such as a single magnetic pole head are the same as those shown in FIG. 2 (d). Therefore, if the subsequent waveform processing is performed by the circuit shown in FIG. Various modifications such as good are possible.

〔The invention's effect〕

As is apparent from the above description, according to the present invention, since the magnetic head positioning control can be performed by holding the peak value of the signal read by the magnetic head to each individual device, a complicated circuit becomes unnecessary, and the device Can be made small in size and can be easily constructed at a low cost, and a remarkable effect can be obtained in various magnetic recording / reproducing devices.

[Brief description of drawings]

1 to 8 show an embodiment of the present invention, FIG. 1 is a diagram showing an arrangement state of magnetization sections, and FIG. 2 is a signal for forming a magnetization section shown in FIG. 1 and a read signal. FIG. 3, FIG. 3 is a block diagram of the processing circuit, FIG. 4 is a circuit diagram showing an example of the peak hold circuit used in FIG. 3, and FIG. 5 is a diagram showing a part of the magnetization arrangement and the read signal waveform. FIG. 6 is a diagram showing the waveform of the signal obtained from each track, FIG. 7 is a diagram showing the output signal characteristic of the peak hold circuit and the characteristic of the difference signal between them, and FIG. 8 is the magnetization state according to another embodiment. FIG. 9, FIG. 9 and subsequent figures show a conventional example, FIG. 9 shows a magnetization state, FIG. 10 shows a waveform diagram of a signal read from the magnetic medium of FIG. 9, and FIG. 11 shows FIG. Waveform diagram of the gate signal that processes the signal, Fig. 12 shows the characteristics of the position signal, and Fig. 13 shows other signals. It is a figure which shows the number writing method. 1 ₁ to 1 ₄ ...... Truck, 5 to 8 ... Magnetization section, 10 ...
Magnetic head, 11 ... Differential amplifier, 12 ... Peak hold circuit.

Claims (1)

[Claims] 1. A Lorentz-shaped arc-shaped waveform obtained by reading the magnetization state recorded on a plurality of tracks formed on a magnetic medium by a magnetic head that relatively moves in the signal recording / reproducing direction along the tracks. In a position information detection signal generating method for generating a signal indicating position information in the track width direction of the magnetic head based on a signal including, a 0.5-0.7 of a half-width of a Lorentz-shaped arc waveform in the signal recording / reproducing direction on the magnetic medium. A first magnetization section having a length doubled and magnetized in a predetermined direction and a second magnetization section having a magnetization direction opposite to that of the first magnetization section are alternately arranged in the signal recording / reproducing direction. The first track is formed, and the third and fourth magnetized sections whose magnetization directions are opposite to those of the first and second magnetized sections are signal-recorded by adjoining the first track. The first and third magnetization sections are arranged alternately in the raw direction to form second tracks, and the first and third magnetization sections are arranged at the end of the first magnetization section and the forefront of the third magnetization section or the first section. The foremost part of the magnetized section and the last part of the third magnetized section are arranged at positions where they are read out at the same timing in the signal recording / reproducing direction, and the signals read from the same track for the second and fourth magnetized section lengths are mutually And a peak value of the signal read from the magnetic medium and a signal obtained by inverting the phase of the signal is held for each of the first
And a second read signal, and a signal indicating the position information is generated by obtaining a difference between the first read signal and the second read signal. .