JPH0231305A - Waveform equalizing circuit for magnetic disk device - Google Patents

Abstract

PURPOSE:To prevent the erroneous detection of a peak position and to improve a reading margin by providing a means to control the amplitude of the synthesized wave of an incident wave and a reflected wave from a delay element in correspondence to a cylinder position and executing optimum waveform equalization in correspondence to the cylinder position. CONSTITUTION:An isolated wave to be reproduced by a magnetic head is inputted, delayed by a delay line 1 and inputted to the + side of a differential amplifier 4. An AGC AMP3 determines the amplitude of the synthesized wave of the incident wave and the reflected wave from the differential amplifier 4. However, the gain of this AGC AMP3 is set to the table of a CPU6 in advance and converted to be analog by a D/A converter 5. Then, the gain of the AGC AMP3 is controlled. In the differential amplifier 4, by respectively subtracting an output waveform, which comes from the AGC AMP3, from the input waveform of the + side, the bottom of the reproducing isolated wave is cut off. Then, the optimum waveform equalization is executed. Thus, the exact peak position can be detected and the reading margin can be improved.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a waveform equalization circuit for a magnetic disk drive.

(Prior Art) Conventionally, in a magnetic disk device, when magnetization reversal recorded on a medium is reproduced using a magnetic head, a solitary wave as shown in FIG. 3 can be obtained. However, when the interval between magnetization reversals becomes narrower, the solitary waves interfere with each other, and the peak position of the solitary wave shifts from its original position as shown in FIG. In magnetic recording, information is contained in the magnetization reversal part recorded on the medium, that is, the peak position of the reproduced solitary wave, and if the peak position of the solitary wave shifts, the reading margin will decrease as a result. become.

In magnetic storage devices, in order to prevent this, a waveform equalization circuit as shown in Figure 5 is used. This prevents peak position shifts due to waveform interference.

The operation of the conventional waveform equalization circuit shown in FIG. 5 will be explained below. In FIG. 5(4), 51 indicates the signal ΔT
52 is an input resistor for matching the input impedance of the delay element 51; 53 is an amplifier for buffering a signal consisting of an input wave and a reflected wave generated at the input terminal of the delay element; 54; 55 is an attenuator that determines the amplitude of the composite wave of the input wave and the reflected wave, and 55 is a differential amplifier that amplifies the difference between the signal delayed by the delay element 51 and the composite wave whose signal amplitude is determined by the attenuator 54. It is. Fifth
In FIG. 3), if a solitary wave like 1 is obtained as an input signal, a signal delayed by ΔT from the input is generated on the + side of the differential amplifier 55 due to the delay element 51. Further, a composite wave of the input signal and the reflected wave from the + side of the differential amplifier 55 is inputted as a signal C to one side of the differential amplifier 55, and the amplitude is determined by the amplifier 53.
An output waveform like d can be obtained from Hc. The waveform of d is b
Since the waveform of C is subtracted from the waveform of C, the bottom of the solitary wave is cut off, and interference between the solitary waves when the interval between magnetization reversals becomes narrow can be prevented.

Generally, when reproducing magnetization reversal recorded on a magnetic recording medium using a head, the head speed is higher on the outer circumference than on the inner circumference, so the width of the solitary wave is larger on the outer circumference than on the inner circumference. It gets narrower. However, in the conventional example, since the r-in of the attenuator 54, which determines the amplitude of the composite wave of the incident wave and the reflected wave, is fixed, the outer circumference is equalized by the same amount as the inner circumference, as shown in FIG. In addition, an overcorrection condition occurs, resulting in false detection in peak detection, resulting in problems such as a decrease in reading simmering margin.

(Problems to be Solved by the Invention) An object of the present invention is to solve the above-mentioned conventional problems, prevent false detection of peak positions, and improve the read shimarine by a waveform equalization circuit for a magnetic disk device. The goal is to provide the following.

[Configuration of the Invention (Means for Solving the Problems) The waveform equalization circuit of the magnetic disk device according to the present invention comprises (1)
) In a waveform equalization circuit of a magnetic disk drive having a delay element that delays an input signal and an input resistor that matches the input impedance of this delay element, in order to obtain optimal waveform equalization at the cylinder position, It is characterized by comprising means for controlling the amplitude of a composite wave of an incident wave and a reflected wave from the delay element in accordance with the cylinder position. (2) The means for controlling the amplitude of the composite wave of the incident wave and the reflected wave from the delay element according to the cylinder position is characterized by using a table of the CPU.

(Function) According to the present invention, when waveform equalization is performed using a composite wave of an incident wave and a reflected wave, the head speed is greater at the outer circumference than at the inner circumference, and the width of the solitary wave becomes narrower. Therefore, if the same synthesized wave as that for the inner frequency is used, overcorrection may occur and false detection of the peak position may occur. Therefore, for example, an amplifier (for example, AGCAMP) controlled by the CPU K may be provided.
By controlling the amplification degree of this amplifier to optimally control the amplitude of the composite wave according to the cylinder position, it is possible to perform waveform equalization optimal for peak position detection at that cylinder position.

(Example) FIG. 1 is a circuit diagram showing the configuration of an embodiment of the present invention.

In FIG. 1, 1 is a delay element for delaying the signal by three signals, 2 is an input resistor for matching the input impedance of delay element 1, and 3 is for connecting the incident wave and the reflected wave from the differential amplifier 4. For example, AGCAMP 4 is a differential amplifier that subtracts the synthesized wave whose amplitude has been optimized by AGCAMP 3 from the input signal from the delay element 1 to cut the base of the reproduced wave. , 5 is CPU
Converter 6 converts the amplification degree of AGCAMP j according to the cylinder into an analog value and supplies it to AGCAMP J. 6 supplies the amplitude change of AGCAMP according to the cylinder position from a preset table to the converter. Indicates a CPU.

FIG. 2 is a diagram showing waveform equalization at the inner and outer circumferences when using the r-in control of AGCAMP 3 in FIG.
FIG. 2 1 shows a regenerated solitary wave on the inner circumference that is input to the + side of the differential amplifier 4 in FIG. 1, and FIG. The composite wave of the wave and the reflected wave, Figure 2C is the solitary wave after waveform equalization at the inner circumference, and the second
Figure d shows the reproduced solitary wave at the outer periphery inputting to the + side of the differential amplifier 4 in Figure 1, and Figure 2 e shows the incident wave and reflected wave at the outer periphery inputting to one side of the differential amplifier 4 in Figure 1. The composite wave, FIG. 2f, shows a solitary wave after waveform equalization at the outer periphery.

The operation of the embodiment of the present invention described above will be explained below.

In FIGS. 1 and 2, the solitary wave reproduced by the magnetic head is input to the waveform equalization circuit shown in fjlc1,
The waveforms delayed by the delay line 1 and input to the + side of the error dynamic amplifier 4 are shown in FIG. 2 a and d. The reason why the width of the solitary wave is narrower at the outer circumference is that the head speed is greater at the outer circumference than at the inner circumference. Further, the incident wave and the reflected wave from the + side of the differential amplifier 4 are inputted to the input of AGCAMP J with a phase difference of 2.2. AGCAMP J determines the amplitude of the composite wave of the incident wave and the reflected wave, but this dyne is
A command is set in the table in advance so that the attenuation increases from the inner circumference to the outer circumference, and is converted into an analog signal by the converter 5.
dyne is controlled. That is, the output waveform of AGCAMP3 is as shown in FIG. Since the width of the solitary wave is narrower on the outer circumference, the output waveform of AGCAMP 3 on the outer circumference and AGCA on the inner circumference will change accordingly.
It can be seen that the amplitude has been adjusted to be smaller than the output waveform of MP3. In this way, a composite wave having an amplitude corresponding to the position of the cylinder, the width of the pick, and the width of the reproduced solitary wave is supplied from the output of AGCAMP j to one side of the differential amplifier 4. In the differential amplifier 4, by subtracting the output waveforms from AGCAMPJ from the input waveforms a and d on the + side, the base of the reproduced solitary wave is cut, and waveform interference can be prevented.

The solitary waves after waveform equalization are shown in Figure 2 e and f, but the AGC
Since the amplitude of the composite wave is adjusted by AMP 3,
Optimal waveform equalization can be performed without overcorrection even at the outer periphery where the width of the reproduced solitary wave is narrow and the base of the solitary wave is smaller than at the inner periphery.

[Effects of the Invention] According to the present invention, for example, the AGC controlled by the CPU
By installing an AMP and increasing or decreasing the amplitude of the composite wave of the incident wave and reflected wave according to the cylinder position, it is possible to perform optimal waveform equalization for that cylinder, making it possible to accurately detect the peak position. Furthermore, it is possible to improve the reading margin.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing the configuration of an embodiment of the present invention, Fig. 2 is a diagram showing waveform equalization of the embodiment shown in Fig. 1, and Figs. 3 and 4 respectively explain waveform interference. Figure for, No. 5
The figure shows a conventional example, and is FIG. 1. 3...AGCAMP, 4...Differential amplifier, 5...
...D/A converter, 6...CPU. 7n, Ihi Anti-Yam Diagram (A) CB)

Claims (2)

[Claims] (1) In a waveform equalization circuit of a magnetic disk drive that has a delay element that delays an input signal and an input resistor that matches the input impedance of this delay element, optimal waveform equalization at the cylinder position can be obtained. 1. A waveform equalization circuit for a magnetic disk drive, comprising means for controlling the amplitude of a composite wave of an incident wave and a reflected wave from the delay element in accordance with the cylinder position. (2) means for controlling the amplitude of a composite wave of the incident wave and the reflected wave from the delay element according to the cylinder position;
2. The waveform equalization circuit for a magnetic disk drive according to claim 1, wherein the waveform equalization circuit is implemented using a table of a CPU.