JPS6124073A - Magnetic disc device - Google Patents

Abstract

PURPOSE:To obtain a reference signal stable for reproduction by applying amplification and low frequency filtering to a reproducing signal, extracting two kinds of single frequency servo signals and providing a servo reproducing circuit forming the servo signals into pulse trains and extracting an index pulse out of the trains. CONSTITUTION:The servo signal reproduced by a magnetic head 7 is amplified by a reproducing amplifier circuit 8 and its output is inputted to a high pass filter 10 to extract a data signal and a low pass filter 9 to extract the servo signal. Comparators 14, 15 form servo signal components of odd and even number tracks into pulses. An output of an OR circuit 20 is inputted to a delay line 22, an output of the delay line is inputted to AND gates 16, 17 and the output is ANDed with a pulse train of the servo signal. An output pulse of the AND gates 16, 17 is inputted to an OR circuit 21, an output of the OR circuit is a final index signal and the index signal is used for a reference signal for recording/reproducing the data.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a magnetic disk device, and in particular relates to an index servo pattern of a buried servo system using a double-layer magnetic disk tube and its reproduction method (Prior art and its problems) Conventionally, the servo surface servo method has been the mainstream for magnetic disk drives, but in this servo surface servo method, the servo disk and the data disk are placed on separate disk plates, so there may be problems due to differences in ambient temperature. However, there was a risk of errors in positioning accuracy. In particular, with this servo surface servo system, as the track density increases, the positioning error of the magnetic head increases, making it difficult to increase the track density and achieve high recording density. Ta. In recent magnetic disk drives, various data surface servo methods are being considered to improve head positioning accuracy, but two data surface servo methods in particular are the sector servo method that uses a portion of the data surface, and the method that uses the data information itself. Also, a buried servo system is being considered in which a magnetic double layer disk is used, the lower magnetic film is used as a servo information medium, and the information is used.

The sector servo method divides one track into sectors and partially inserts servo information, but it has the disadvantage that track servo is not possible in areas other than the part where servo information is output. The head positioning accuracy is insufficient in terms of density. Furthermore, the servo system that uses data information itself as servo information has the disadvantage that positioning errors occur when the output envelope of the data information changes, since the data information itself is used. On the other hand, a buried servo system that uses two layers of magnetic films uses the upper layer for data information and the lower layer for servo information.

Positioning errors are small because one data head simultaneously detects data and servo information and uses them separately.

However, in the buried servo method using a magnetic double-layer disk, when recording and reproducing data signals, it is necessary to detect an index signal that serves as a reference from the servo signal. Conventionally, in this buried servo method, the servo signals are The data are recorded continuously at the same frequency, but there is a drawback that there is no index signal that serves as a reference for the data signal.(Objective of the Invention) The object of the present invention is to develop a buried servo system that eliminates the above-mentioned drawbacks. An object of the present invention is to provide a servo pattern and an index reproducing method for servo (Arrangement of the Invention) In the present invention, two types of single frequencies are continuously recorded alternately for each track on a lower layer film for servo, and A magnetic double-layer disk having a servo pattern in which index information is recorded in the same sector, a servo head for reproducing the servo pattern, and amplifying and low-pass filtering the reproduced signal to generate two types of single frequencies. 〇 A magnetic disk device characterized by comprising a servo reproducing circuit that extracts a servo signal, converts the servo signal into a pulse train, and outputs an index pulse tll; tl:>f from the pulse train.・Principle) With the above configuration, the index signal can be extracted from a part of the servo signal, so the index signal can be extracted on the same disk surface and data signals can be recorded and reproduced using the index signal as a reference signal. There are many things to do.

Examples of the present invention will be described below in Sections 1.2. This will be explained in detail using Figure 3.

(Example) FIG. 1 shows a servo pattern recorded on the lower servo layer of a magnetic double layer disk, and FIG. 2 shows a reproduced waveform when an index portion is reproduced in each servo track. Furthermore, FIG. 3 is a circuit configuration diagram for extracting an index signal from a servo signal. In FIG. 1, servo information is recorded on the servo magnetic film of a magnetic double-layer disk 1 using a two-frequency method, alternately in odd-numbered tracks 21, 4 and even-numbered tracks 3, and the same information is recorded in the same sector of all servo tracks. For example, when the index signal is a gui pulse, the servo signal reproduced by the servo head is as shown in Fig. 2. Naruguchi and the servo signal reproduced like this,
Extract the index pulse. Next, a reproducing circuit for extracting the index signal from the servo pattern will be explained with reference to FIG.

When the magnetic double layer disk 6 and the magnetic head 7 are located at the position where the reproduction servo signal shown in FIG. 2 (alt (b)) is located, the signal processing will be explained in FIG. The regenerated servo signal is sent to the regenerative amplifier circuit 8.
The low-pass filter 9 inputs the output to a bypass filter (high-frequency p-wave) 10 for extracting a data signal and a low-pass filter (low-pass p-wave) 9 for extracting a servo signal. The output of the even track servo signal extraction filter 11 and the odd track servo signal extraction filter 12 are inputted, and the output of the even track servo signal extraction filter 11 is inputted to the comparator 14 and the servo signal creation circuit 13. The output of the odd track servo signal extraction field 12 is the comparator 1.
5 and is input to the servo signal generation circuit 13. Comparators 14 and 15 pulse the servo signal components of the odd and even tracks. The output pulses of the comparators 14 and 15 are input to the retriggerable monomalte vibrators 18 and 19, respectively, and are simultaneously ANDed (AND) 16
．． 17, respectively. Here, the output pulse width T of the retrigger pull mono multivibrator 18, 190 is T<T with respect to the cycle of the servo signal (servo signal with a small frequency) T in FIG.

If the time interval tTt and T between the 0th order index signal and the servo signals before and after it is set to satisfy the condition <2T, then the 1 time interval T is 'I't> 2 'I'
, and the time interval Ts t Ta < T
By setting the time interval in this way, the retrigger 2-pull mono multivibrator 18° 190 output becomes low level during continuous servo signals, and the T of long-period magnetization. This produces a pulse waveform that rises in between and falls in the index signal portion (di-pulse portion) with short-period magnetization reversal. The outputs of the retriggerable mono multivibrators 18 and 19 are input to the OR circuit 20, and the outputs of the OR circuit 20 are connected to the delay line 22 (delay time T(
The output of the delay line 't is input to the AND gates 16 and 17, and the pulse train of the servo signal and the AN
The output pulse 'j of the AND gates 16 and 17 for each 0, where the output of the AND gate becomes the index signal.
-01'L circuit 21, and the output of the OR circuit becomes the final index signal. Using this index signal as a reference signal for recording and reproducing data (effects of the present invention) By using the present invention, in a buried servo system using a magnetic double layer disk, the servo signal and the index signal can be simultaneously output. Since the same disc surface can be taken out with high precision, a stable reference signal for recording and reproducing data can be obtained.

[Brief explanation of the drawing]

Figure 1 shows the servo pattern recorded on the servo magnetic film on the lower layer of the magnetic double layer disk, Figure 2 (a) t
(b)t (C) is a reproduced servo signal waveform diagram of the index portion, and Figure '3 is a diagram showing an embodiment of the circuit configuration for extracting the index signal from the servo signal.
1 is a magnetic double-layer disk, 2 and 4 are servo patterns for odd-numbered tracks, 3 is a servo pattern for even-numbered tracks, and 5 is an index signal portion. 6 is a magnetic double layer disk, 7 is a magnetic head, 8 is a regenerative amplifier circuit, 9 is a low I (sfilter), 10 is an I-pass filter, 11 is an even track servo signal extraction filter, 12 is an odd track servo signal extraction filter, 1
3 is a digital input error generating circuit, 14.15 is a comparator, 18.19 is a retrigger monomartenometer (ibrator), 16°17 is an AND circuit, 20.21 is a zero circuit, and 22 is a delay line. 0 o l figure

Claims (1)

[Claims] A magnetic double layer disk having a servo pattern in which two types of single frequencies are continuously and alternately recorded on a servo underlayer film for each track, and index information is recorded in the same sector portion on those tracks, and a servo pattern. A servo head that reproduces the signal, amplifies and low-pass filters the reproduced signal, extracts the two types of single-frequency servo signals, converts the servo signal into a pulse train, and generates an index pulse from the pulse train. A magnetic disk device characterized by comprising a servo playback circuit for taking out the data.