JPS6396721A - Position signal generating method - Google Patents

Abstract

PURPOSE:To miniaturize a reproducing device, by holding individually the positive and the negative peak values of a Lorentz isolation signal obtained by reading sawtooth magnetization by a magnetic head, and generating the position signal of the magnetic head based on the signal of a difference between the values. CONSTITUTION:The magnetization of a magnetizing section 5 has a polarity opposite to that of a magnetizing section 6, and the lengths of the magnetizing sections 5 and 6 in a signal recording and reproducing direction are set larger than the half value width of a Lorentz isolation signal waveform. Also, a magnetizing section is set in a magnetizing state so that the Lorentz isolation signal waveform (unimodal pulse) having a single polarity can be reproduced. By arranging adjacently an even track and an odd track in which such magnetizing sections are arranged, alternately, a magnetic medium 7 having a width of W in a direction of (y) can be obtained. In digital magnetic recording, a positive and a negative peak always appear alternately to steepen magnetizing transition. Therefore, the sawtooth magnetization in which the magnetizing transition on one side changes steeply, and the magnetizing transition on the other side changes gradually, to obtain the single peak pulse, is remained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of generating a position signal for positioning an information recording/reproducing head of a magnetic recording/reproducing device to a desired trunk position on a magnetic medium. be.

[Conventional technology]

In devices such as magnetic disks and floppy disks that store large amounts of information, which involve positioning the magnetic head on any track among multiple trunks on the recording medium, the storage capacity must be increased (in order to increase the storage capacity, the trunk must be Increasing the density is effective. For this purpose, it is necessary to accurately position the magnetic head. For this positioning, servo signals are sent to each track on the recording medium to position the magnetic head. When recording and reproducing data information, a position signal for controlling the position of the magnetic head is generated based on this servo signal, and based on this position signal, the magnetic head moves to the adjacent track. Since the data information is recorded and reproduced after such control is performed, the data information is shifted from the servo signal by half the trunk width in the track width direction. Various methods have been proposed for writing such servo signals, such as tri-bit, gui-bit, and modified gui-bit.

FIG. 10 is a diagram showing an information detection method in the case of tri-bits. This figure shows the magnetization arrangement recorded on each track. 1 is a magnetic medium in which tracks TR1 to TR4 of width W are arranged adjacently, and each track has a direction in which information is recorded and reproduced. A sync bit 2 having a period T is arranged. In the odd-numbered tracks (hereinafter referred to as "odd-numbered tracks") TRI and TR3, a position control bit (hereinafter referred to as "odd-numbered position bit") 3 is arranged at a position T/3 away from the sync bit 2 in the information reading direction. In the even-numbered tracks (hereinafter referred to as "even-numbered tracks") TR2 and TR4, a position control bit (hereinafter referred to as "even-numbered position bit") 4 is arranged at a position 2T/3 away from the sync bit 2 in the information reading direction. has been done.

Figure 11 shows the waveform when the magnetization pattern in Figure 10 is read out, and Figure 11 (a) shows the readout waveform when the magnetic head is positioned on an odd numbered track, where the Lorentzian isolated signal is t = o. , t-T/3. It is read out at t=T. FIG. 11(b) shows a read waveform when the magnetic head is located between an even track and an odd track, at time t.
-0, t-T/3, t-2T/3. A Lorentzian isolated signal is read out at t=T. FIG. 11(C) shows read waveforms when the magnetic head is positioned on an even trunk, and shows the read waveforms at times t-0, t-2T/3, t-2T/3. A Lorentzian isolated signal is read out at t-T.

FIG. 12 shows a gate signal for reproducing a position signal indicating the positional relationship between the magnetic head and the track from the read signal shown in FIG. In FIG. 12, (a) shows an odd gate signal that maintains a high level for a period of time that does not include the read signal of sync bit 2 and even position bits, centered around T/3 where odd position bits exist; ('b) shows an even gate signal that maintains a high level for a period of time that does not include the read signal of sync bit 2 and odd position bits, centered around 2T/3 where even position bits exist. These gate signals are generated by slicing the read signal of sync bit 2, which is generated every period T, at a negative level to generate a reference pulse, and based on this, a combination of a phase periodic circuit, a delay element, a logic circuit, etc. be done. Since the sync bit 2 is read out at a constant level no matter what track position the magnetic head is in, the gate signal can be generated every period T.

The signal read from the track is input to two analog switches (not shown), and each analog switch outputs the input signal while the even gate signal and odd gate signal are at high level, so one of the analog switches A read signal for even-numbered position bits is outputted to the output, and a read signal for odd-numbered position bits is outputted to the other output.

Each output of the analog switch is input to a peak hold circuit (not shown), and each of the even and odd position bits is held, as shown in FIG. 13(a) in response to changes in the positions of the magnetic head and trunk. The signals corresponding to the odd-numbered position bits are outputted as shown by the solid line, and the signals corresponding to the even-numbered position bits are outputted as shown by the dotted line. By taking the difference between these two peak hold output signals, a position signal as shown in FIG. 13 (G) is obtained.

As can be seen from the above explanation, this position signal is a triangular waveform signal that becomes zero when the magnetic head is located between even and odd tracks, and takes either a positive or negative level as the magnetic head shifts back and forth. The magnetic head is positioned so that the level of this position signal is zero.

Other conventional methods for detecting location information include the first
As shown in FIG. 4, there is a so-called two-frequency system in which a sine wave with a frequency f is placed on odd-numbered tracks, and a sine wave with a frequency ft different from f is placed on even-numbered tracks. in this case,
The magnetic head read signal is 5(t)=A sin(2πf,t)+Bs
It is given in the form i n (2πf, t). 5(t) with two reference signals, r+ (t) = sin(2πf +t), r
By multiplying each by z(t)=s i n (2πrzt), the following signals are obtained.

S (t)r+(t) =A/2- (A/2) c
o s (4πf +t)+ (B/2) c o S
(2π(L fz)t)-(B/2) cos
(2π(r++rz)t)S (t)rz(t)−B
/2− (B/2) cos (4πf 2t)+
(A/2) co S (2π(f+-ft)t)
-(A/2) co s (2π(f++b)t) If we pass these signals through a filter with a cutoff frequency lower than (r, -r,), we get values A/2 and B/2. A DC component is obtained, and if we take the difference between these two DC components, we get
A position signal is obtained as shown in FIG. 13(b).

[Problem that the invention seeks to solve]

As explained above, the method shown in FIG.
The method shown in Figure 4 uses frequency division to separate the signals. As a result, in order to reproduce the position signal, an accurate timing generation circuit is required for time division, and an accurate reference signal generation circuit 9 with matching frequency and phase is required for frequency division. Configuring these circuits is
If the device is large-scale, there will be no major disadvantage in terms of mounting space or price, but with recent low-cost small disk devices that use small-diameter media, the mounting space will be significantly increased and the economy will be poor. It had a major drawback:

The present invention has been made in view of the above points, and its purpose is to provide a position signal generation method that allows obtaining a magnetic recording and reproducing device that is small in size and economical. be.

[Means for solving problems]

To achieve such an object, the present invention provides a method for positioning a magnetic head at a desired track position based on a Lorentzian isolated signal obtained by reading magnetization written in a plurality of tracks on a magnetic medium. In this method, a sawtooth recording current is used to cause sawtooth magnetization having a repetition period longer than the half-width of the Lorentzian isolated signal to remain in each track, and the magnetization states of adjacent tracks are reversed in direction from each other. The positive and negative peak values of the Lorentzian isolated signal obtained by reading out the sawtooth magnetization with the magnetic head are held individually, and a position signal of the magnetic head is generated based on the signal of the difference between these peak values. This is how it was done.

[Effect]

In the present invention, the magnetic head can be positioned without increasing the size of the magnetic recording/reproducing device.

〔Example〕

As mentioned above, in order to position the magnetic head, it is necessary to write a servo signal on the magnetic medium so that the magnetic medium remains magnetized. FIG. 1 is a pattern diagram showing a magnetization pattern for explaining an embodiment of the position signal generation method according to the present invention. In FIG. 1, 5 is a magnetization section of odd-numbered tracks, and 6 is a magnetization section of even-numbered tracks, and the magnetization of magnetization section 5 and magnetization section 6 are of opposite polarity. Signal recording and reproducing direction of magnetization sections 5 and 6 (
The length (in the X direction) is made larger than the half width of the Lorentzian isolated signal waveform. Further, magnetization sections 5 and 6 are in a magnetization state such that a unipolar Lorentzian isolated signal waveform (hereinafter referred to as a "unipeak pulse") can be reproduced, and these magnetization states and recording method will be described later. When even-numbered tracks and odd-numbered tracks in which such magnetized sections are arranged are alternately arranged adjacent to each other, a magnetic medium 7 having a width W in the X direction shown in FIG. 1 is obtained.

Next, the principle of detecting a position signal from such a magnetic medium will be explained. Fig. 2(a) shows a pair of odd track n and even track n+1, and Fig. 2(b) to (g) show the magnetization state and its relationship when the magnetic head 8 is on each track. Current waveforms for recording and playback waveforms are shown. In normal digital magnetic recording, since the magnetization transition is made steep, positive and negative peaks always appear alternately. In this method, in order to obtain a unimodal pulse, as shown in Figures 2(d) and (e), we create a sawtooth magnetization in which one magnetization transition changes sharply and the other magnetization transition changes gently. to remain. To achieve this, the recording current is made into a sawtooth recording current as shown in FIG. In this case, a dedicated analog recording circuit is required, and the magnetic head also requires a high frequency band that allows biasing. Recording is not suitable for digital magnetic recording devices.For this reason, in this method, in order to easily record and reproduce unimodal pulses using an ordinary digital recording circuit and magnetic head, the digital recording circuit is analog-controlled to generate sawtooth pulses. We used non-bias recording, which generates a recording current and leaves sawtooth magnetization behind.With non-bias recording, it is impossible to overwrite recorded information, so the magnetic medium must be completely demagnetized beforehand. However, if the servo information is recorded at the beginning of the medium's use, it will not be rewritten again, so the degaussing process described above is not a problem.

Note that since FIG. 2 is an explanatory diagram for showing the principle of detecting a position signal, the relationship between the recording current and medium magnetization is not strictly described. Actually, Fig. 2(b).

When recording with a recording current as shown in (C), the magnetization changes to +1 as shown in Figure 2(d) due to the non-linear characteristics of the initial magnetization curve of the medium.
The ideal sawtooth magnetization state as shown in Figure 2 does not occur. Details regarding this will be described later.

The position signal is obtained by the following signal processing.

If the tracks having the magnetization state as shown in Fig. 2 (a) are placed adjacent to each other, the reproduced waveform in the trunk n is obtained by the magnetic flux differentiation from di (Fig. In other words, according to the following equation (5), a Lorentzian isolated signal with a positive peak level is read out from the part where the magnetization change is steep and the slope is positive, and a Lorentzian isolated signal with a positive peak level is read out from the part where the magnetization change is slow and the slope is negative. Negative /dx...(5) Here, V(t): Signal X read from the magnetic head 8: Information recording/reproducing direction δ: Medium thickness M: Magnetization 2: Medium thickness direction Φ: The reproduced waveform at track n+1 is shown in Figure 2 (
If the positive and negative levels of the monomodal pulse obtained in this way are peak held, the output will be as shown in Figure 2(f), (g ) The amount of positional deviation of the magnetic head 8 can be obtained by the difference between the positive and negative peak hold outputs, and when the magnetic head 8 is on track n, the DC value E can be obtained. When the position is on track n and l, a DC value -E is obtained, and when it is located in the middle of the track, a DC value of 0 is obtained, and a normal triangular wave position signal 13 is obtained (
Figure 2 (h)).

In this way, according to the present method, a position signal can be easily obtained by simply arranging tracks having sawtooth magnetizations of opposite polarity alternately and observing the reproduced waveform via a peak hold circuit. In addition, since this method generates position signals asynchronously only by peak hold, the phase relationship of magnetization in each track can be arbitrary. However, if the phase relationship is fixed during recording, the amount of crosstalk between tracks can be reduced. becomes constant, making it easy to guarantee the quality of the position signal.

FIG. 3 is a circuit diagram of a circuit that reads a signal from the magnetic medium 7 on which servo information is written as shown in FIG. 1 and generates a position signal from the signal.

In the figure, 8 is a magnetic head, 14 is a differential amplifier that sends out a non-inverted output and an inverted output, and 15 is a peak hold circuit. The peak hold circuit 15 is composed of a circuit as shown in FIG. In FIG. 4, 151 is a diode, 152 is a capacitor, and 153 is a constant current circuit.

Next, the relationship between the sawtooth recording current waveform, medium magnetization, and reproduction waveform will be explained, and an example of improving the waveform of a single peak pulse will be described. FIG. 5 shows medium magnetization and reproduction waveforms when recording is performed with a normal sawtooth recording current. When recording is performed with a recording current as shown in FIG. 5(a), the magnetization changes according to the medium initial magnetization curve, and as shown in FIG. A magnetization state with a small slope in the vicinity remains.The reproduced waveform is the fifth
It becomes a single peak pulse as shown in figure (C), and E, l/E p9
The value of the positive/negative peak level ratio expressed by is approximately 30%.

Figure 6 is an example of improving the recording current waveform to increase the positive peak level (and decrease the negative peak level. In other words, in order to increase the positive peak level, the value Tf becomes the maximum current part of 2). A flat portion indicated by the width is provided. This allows the residual magnetization of the magnetization reversal portion to be thickened. Also, in order to reduce the negative peak level, a step of Δ■ is provided near zero current. This linearly corrects the magnetization change near zero current, and the maximum magnetization is also ±M, which is larger than ±M° in FIG.

With the above improvements, the reproduced waveform can be an ideal single-peak pulse with a large positive peak level and a small negative peak level, as shown in FIG. 6(C), and E n / E
The value of the positive/negative peak level ratio represented by p is approximately 19%.

Examples of improvement effects achieved by the above method are shown in FIGS. 7 and 8. FIG. 7 shows the ratio of step current to reversal current ΔI/I
This is an experimental result of the unimodal characteristic, that is, the positive/negative peak level ratio E n /E p when changing . However, in FIG. 7, only the striations caused by the step current are shown, and the flat part at the maximum current part is not used. Positive/negative peak level ratio E
The smaller the value of n/Ep, the more unimodal it is. According to FIG. 7, the unimodal property is maximum when ΔI/I is 15%, and E n /E p is about 20% at that time. The value of this positive/negative peak level ratio is approximately equal to the value when ideal sawtooth magnetization remains. Also, from Figure 7, Δ
It can be seen that good unimodal properties can be obtained when 1/I is 5 to 20%. If ΔI/I is selected within the above range, good position signal quality can be obtained, but this value can be arbitrarily selected as long as it satisfies the positioning accuracy required by the device, that is, the position signal quality. It is not fixed to the value of .

FIG. 8 shows the effect of improving unimodal property when a flat portion is provided at the maximum current portion of the sawtooth recording current. This is obtained by calculating the peak level of the reproduced waveform using equation (5) when ideal sawtooth magnetization is achieved. The horizontal axis shows the width of the flat part normalized by the half width of the Lorentzian isolated signal waveform, and the vertical axis shows the positive/negative peak level ratio. From FIG. 8, if Tf/W50 is set to 20 to 50%, if no flat part is provided, that is, Tf/W50=0.
It can be seen that the unimodal property can be improved by about 10% compared to .

However, the value of Tf/W5Q can be arbitrarily selected as long as it satisfies the positioning accuracy required by the device, that is, the position signal quality, and is not fixed to the above value.

The above shows that by providing steps and flat parts in the sawtooth recording current, it is possible to improve unimodal property, which is an important parameter from the viewpoint of position signal quality. The effect of steps and flat areas is mainly greater, so by first providing a step, the ideal sawtooth magnetization required to reproduce a single peak pulse remains, and then the current is further flattened. It is desirable to improve the unimodal property by providing a section.

FIG. 9 shows the position signal characteristics obtained by this method.

The horizontal axis represents the track position, and W represents the trunk width.

In FIG. 9, a dotted line 17 is an example of a position signal characteristic when a single peak pulse is recorded and reproduced without providing a step or a flat portion in the sawtooth recording current, and there is a large bend at the peak portion. Further, a solid line 18 is a position signal waveform when the single peak property is improved by providing a step and a flat portion in the current, and the bending of the peak portion (±Vp) is improved. Since the magnetic head is positioned so that the level of the position signal is zero, the positioning error is mostly caused by the zero point, that is, ±(2n -1) W/2 (where n is 1,
2. ) are the characteristics of the vicinity. Therefore, although the position signal obtained by this method has some bends near the peak, this has little effect on positioning performance. However, as shown in FIG. 9, if the single peak pulse is improved, the linear region near the zero point of the position signal will be expanded, so it goes without saying that the positioning performance will also be improved. In any case, according to the present method, a position signal that can be used in practical use can be generated by a position signal generation method that allows for a compact, simple, and economical device configuration.

〔Effect of the invention〕

As explained above, the present invention uses a sawtooth recording current to cause sawtooth magnetization having a repetition period longer than the half-width of a Lorentzian isolated signal to remain in each track, and the magnetization states of adjacent trunks are reversed in direction from each other. The positive and negative peak values of the Lorentzian isolated signal obtained by reading out the sawtooth magnetization with the magnetic head are held individually, and a position signal of the magnetic head is generated based on the signal of the difference between these peak values. This eliminates the need for complicated and large-scale circuits such as conventional timing generation circuits, which has the effect of reducing the size of the magnetic recording/reproducing device that positions the magnetic head and improving its economic efficiency. .

[Brief Description of the Drawings] Fig. 1 is a pattern diagram showing magnetization patterns for explaining an embodiment of the position signal generation method according to the present invention, and Fig. 2 is a pattern diagram showing magnetization states and various signal waveforms. 3 is a circuit diagram showing a circuit that processes a read signal, FIG. 4 is a circuit diagram showing an example of a peak hold circuit, FIG. 5 is a waveform diagram showing an example of a recording current waveform, and FIG. Waveform diagrams showing other recording current waveforms, FIG. 7 is a graph showing the positive/negative peak level ratio with respect to the ratio of reversal current to step current, and FIG. 8 is a graph showing the positive/negative peak level ratio with respect to the width of the flat part.
Fig. 9 is a characteristic diagram showing the position signal characteristics obtained by this method, Fig. 10 is a pattern diagram showing the magnetization arrangement in the conventional method, and Fig. 11 is the waveform of the Lorentzian isolated signal read from the magnetic medium in Fig. 10. FIG. 12 is a waveform diagram showing the waveform of the gate signal when processing the signal shown in FIG. 11, FIG. 13 is a characteristic diagram showing the position signal characteristics obtained by the conventional method, and FIG. FIG. 3 is a pattern diagram for explaining another conventional method. TRI~TR4... Trunk, 5.6... Magnetization section, 7... Magnetic medium, 8... Magnetic head, 9.16.
...Sawtooth recording current, 10...Sawtooth magnetization, 11.1
2... Single peak pulse, 13... Position signal, 14...
Differential amplifier, 17.18...Position signal characteristic curve.

Claims (3)

[Claims] (1) In a method of generating a position signal for positioning a magnetic head at a desired track position based on a Lorentzian isolated signal obtained by reading magnetization written in a plurality of tracks on a magnetic medium, a sawtooth A sawtooth magnetization having a repetition period longer than the half-width of the Lorentzian isolated signal is left in each track by using a recording current, and the magnetization states of adjacent tracks are reversed in the reverse direction, and the magnetic head is used to record the sawtooth magnetization. A position signal generation method in which the positive and negative peak values of the Lorentzian isolated signal obtained by reading are held individually, and a magnetic head position signal is generated based on the signal of the difference between these peak values. (2) The sawtooth recording current has a current step near zero,
The current step portion is characterized in that the ratio of the current amplitude to the magnetization reversal current amplitude used for recording the steep magnetization transition portion of the sawtooth magnetization is set to 5 to 20%. The position signal generation method according to scope 1. (3) Position signal generation according to claim 1, wherein the sawtooth recording current has a flat portion having a width of 20 to 50% of the half width of the Lorentzian isolated signal at its maximum current portion. Method.