JP2778312B2 - Magnetic reproduction circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reproducing circuit used in a magnetic recording / reproducing apparatus.

[0002]

2. Description of the Related Art As a magnetic reproducing circuit for detecting a magnetization reversal position from a reproduction signal read from a magnetic recording medium having a magnetic recording component in both directions of movement of a magnetic head and a direction perpendicular thereto, a Hilbert transform filter and a delay are used. A circuit using an element is disclosed in, for example, JP-A-62-231404,
(BJ Langland “Phase Equalization for Perpendicul
arRecording ”IEEE Trans.on Magn., MAG-18, pp1247-12
49) etc.

[0003] Figure 5 is a block diagram showing a configuration of a reproducing circuit of this conventional type, reference numeral 1 denotes an input terminal of the reproduced signal from the magnetic head (not shown), 2 Hilbert transform filter, 3 is a delay element, 4 is an amplification coefficient tan
is an amplifier for θ, 5 is a subtractor, 6 is an amplifier for an amplification coefficient cos θ, and 7 is an output terminal.

Next, the operation will be described. For the explanation, see Reference 2 (Roberti. Potter “Analysis of Saturation Magne
tic Recording Based on Arctangent Magnetization Tr
ansitions ”J.Apll.Phys.Volume 41.P1647〜1651 (197
0)), a reproducing waveform model derived from a reciprocity theorem using a Kahlkist model as a head magnetic field and an inverse tangent function model as a residual magnetization of a medium is used.
In the same model, the moving direction component of the magnetic head (hereinafter referred to as a longitudinal component) and the vertical direction component (hereinafter referred to as a vertical component)
The parameter θ is used as the ratio of cos θ: sin θ.

Here, assuming that the width of magnetization reversal is a, the spacing is d, the gap length is g, and the distance x is a variable, the reproduced signal e ₀ (x) applied to the input terminal 1 is expressed by the following equation (1). It is. _{e 0 (x) = e x} (x) · cosθ + e y (x) · sinθ (1) i.e., regeneration of the formula (1) signal e ₀ (x), the following equation (2)
In the longitudinal component e _x (x) represented represented by the sum of the formula (3) vertical component e _y represented by (x).

[0006]

(Equation 1)

FIG. 6A shows the reproduction signal e ₀ (x), and FIG.
Is the longitudinal component e _x (x), and FIG.
₆ is a time chart showing a signal waveform of _y (x). As is clear from the figure, the longitudinal component e _x (x) has a left-right symmetry, the vertical component e _y (x) has a point-symmetric waveform, and the reproduced signal e ₀ (x) which is the sum of the waveforms has an asymmetric waveform. By the way, the longitudinal component e _x
(x) and the vertical component e _y (x) have a relationship represented by the following equations (4) and (5).

[0008]

(Equation 2)

Therefore, by the Hilbert transform, the equation
Conversion of both (2) and (3) is possible, and thus the reproduced signal e
The output e _h (x) after the Hilbert transform by the Hilbert transform filter 2 of ₀ (x) is expressed by Expression (6). _{e h (x) = - e} x (x) · sinθ + e y (x) · cosθ (6)

The converted output signal e _h (x) is amplified by the amplifier 4 to obtain a signal tan θ · e _h (x).
By subtracting the reproduction signal e ₀ (x) compensated for the delay caused by the Hilbert transform filter 2 and the amplifier 4 by the delay element 3 and amplifying it by the amplifier 6, the output terminal 7
As shown in (7), the _{e c (x) = {e} 0 (x) -tanθ · e h (x)} cosθ = e x (x) (7) symmetrical waveform shown in FIG. 6 (b) The signal e _c converted into the longitudinal component e _x (x) is obtained, and the magnetization reversal position can be detected.

[0011]

Since the conventional magnetic reproducing circuit using the Hilbert transform filter is configured as described above, a desired converted signal output cannot be obtained unless the parameter θ relating to the ratio of the longitudinal component to the vertical component is known. I can't get it. Therefore, it is necessary to add a new arithmetic circuit for calculating θ, and there has been a problem that the circuit becomes complicated. Further, when the product specifications are determined in advance so that the value of θ falls within a predetermined value, there arises a problem that it is necessary to strictly manage variations in magnetic characteristics of the medium, recording and reproduction conditions of the apparatus, and the like.

The present invention has been made in order to solve the above-mentioned problems, and does not require the calculation of the component ratio, and the component ratio varies depending on the orientation ratio of the medium, recording conditions, and the like. It is another object of the present invention to provide a magnetic reproducing circuit capable of detecting a magnetization reversal position.

[0013]

According to a first aspect of the present invention, there is provided a magnetic reproducing circuit comprising: a Hilbert transform filter and a delay element for inputting both signals reproduced from a magnetic recording medium; and a Hilbert transform filter and a delay element. divisor one of the two output divider and the other performs the division as the divisor includes arctangent calculator for converting an output of the divider to the arctangent, and a differential calculator for differentiating the output of the arctangent calculator It is a thing.

According to a second aspect of the present invention, there is provided a magnetic reproducing circuit comprising a Hilbert transform filter and a delay element for inputting both signals reproduced from a magnetic recording medium, and a first differential for inputting both outputs of the Hilbert transform filter. Arithmetic unit and first
, And a second input that inputs the outputs of the delay elements together
, A second squarer, a first multiplier for multiplying both outputs of the Hilbert transform filter and the second differentiator, and both outputs of the delay element and the first differentiator Multiplier, a subtractor for calculating a difference between both outputs of the first and second multipliers, and a first and second 2
An adder for calculating the sum of both outputs of the multiplication operation unit, and a divider for performing division using the output of the subtractor as a dividend and the output of the adder as a divisor.

[0015]

According to the first aspect of the present invention, a signal obtained by Hilbert transforming a reproduced signal in which a vertical component and a longitudinal component are superimposed by a Hilbert transform filter is divided by a reproduced signal in which a delay caused by the conversion is compensated for by a delay element. Calculates the arc tangent of the divided value with the arc tangent calculator, and obtains the differential value of the arc tangent with the differential calculator, thereby irrespective of the component ratio between the vertical component and the longitudinal component. A symmetrical signal waveform centered on the position is obtained.

According to a second aspect of the present invention, a signal obtained by Hilbert transforming a reproduced signal in which a vertical component and a longitudinal component are superimposed by a Hilbert transform filter, and a reproduced signal in which a delay caused by this conversion is compensated for by a delay element, are obtained. Is multiplied by a first multiplier with a signal differentiated by a differential operation unit, and a signal obtained by differentiating a signal Hilbert-transformed by the Hilbert transform filter by a first differential operation unit with a signal delayed by the delay element A signal obtained by multiplying by a second multiplier, a difference between the output signals of the first and second multipliers, and a signal obtained by squaring a signal subjected to the Hilbert transform by the Hilbert transform filter by a first square calculator, and The division value obtained by dividing the sum of the signal delayed by the delay element and the signal squared by the first square calculator by a divisor is obtained by the divider, so that the magnetization is independent of the component ratio between the vertical component and the longitudinal component. Inversion Symmetrical waveform around the location is obtained.

[0017]

【Example】

Embodiment 1 FIG. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of the first invention of the present invention. In the drawing, reference numeral 10 denotes a reproduction signal input terminal, 11 an A / D converter for converting an input analog signal into a digital signal, 12 is a Hilbert transform filter, 13
Is a delay element having the same delay time as the Hilbert transform filter 12, 14 is a divider for performing a division process using the output of the Hilbert transform filter 12 as a dividend and the delay element 13 as a divisor, and 15 is previously written in a storage element such as a ROM. An arc tangent calculator for reading out the inserted arc tangent function characteristic value, calculating and outputting the arc tangent value of the input value, 16 is a differential calculator for calculating and outputting a differential value of the input value, and 17 is an input digital signal. Is a D / A converter for converting the analog signal into an analog signal, and 18 is an output terminal.

Next, the operation will be described using a reproduced waveform model similar to the conventional example. When Equation (1) is transformed into polar coordinates,
The following equation (8) is obtained.

[0019]

(Equation 3)

[0020] Here, φ (x) = - a ψ (x) + θ (9 ) ψ (x) = tan -1 {e y (x) / e x (x)} (10). Therefore, the differential amount of φ (x) Y (x) = dφ (x)
/ Dx

[0021]

(Equation 4)

## EQU1 ## _{Here, e x (-x) = e} x (x), (12) e y (-x) = - e y (x) (13) Since Y (x) = dφ (x ) / dx is even function And becomes a symmetric function centering on the magnetization reversal position. Therefore, by obtaining the differential value of the arctangent of the ratio of the vertical component e _y (x) to the longitudinal component e _x (x) of the reproduced signal e ₀ (x), is independent of the magnetization reversal position is sought and theta. By the way, from equation (14),

[0023]

(Equation 5)

[0024] and, the differential value of the arctangent of the ratio of the vertical component e _y (x) to the longitudinal component e _x (x) of the reproduced signal e ₀ (x), the reproduced signal e ₀
It becomes equal to the derivative of the inverse tangent of the ratio between the Hilbert transform value e _h (x) of (x) and the reproduced signal e ₀ (x).

In FIG. 1, the analog reproduction signal e ₀ (x) input to the input terminal 10 is supplied to the A / D converter 11
, And the output signal is Hilbert transformed by the Hilbert transform filter 12, and the output e _h (x) is applied to the divider 14 as a dividend. On the other hand, the digitally converted reproduced signal e ₀ (x) is
In 3, the delay of the operation time in the Hilbert transform filter 12 is corrected and applied to the divider 14 as a divisor. The operation output e _h (x) / e ₀ (x) of the divider 14 is the arctangent operation unit 1
5 and its arctangent value tan ^-1 {e _h (x) / e
₀ (x)}, and is differentiated by the differentiator 16 to obtain the ratio of the vertical component e _y (x) to the longitudinal component e _x (x) of the reproduced signal e ₀ (x) shown in equation (14). An arctangent differential value Y (x) is obtained.
As described above, this value is a symmetric function centered on the magnetization reversal position. Therefore, if the D / A converter 17 converts the value into an analog signal and detects the zero point position, the magnetization reversal position becomes independent of θ. Desired.

In the above embodiment, the division by the divider 14 is performed by using the output of the Hilbert transform filter 12 as the dividend and the output of the delay element 13 as the divisor. However, even if the divisor and the dividend are exchanged, the equation (11) can be obtained. Just by reversing the sign, it becomes a symmetric function centering around the magnetization reversal position,
Similar effects can be obtained.

Embodiment 2 FIG. FIG. 2 is a block diagram showing the configuration of an embodiment of the second invention of the present invention.
0 is a reproduction signal input terminal, 11 is an A / D converter, 12 is a Hilbert transform filter, 13 is a delay element, and 17 is D / A
A converter 18 is an output terminal, and the above is the first embodiment shown in FIG.
Is similar to 19 is a Hilbert transform filter 1
A first differential calculator for calculating and outputting the differential value of the input value from the second input device, 20 a second differential calculator for calculating and outputting the differential value of the input value from the delay element 13, and 21 a Hilbert transform A first multiplier that calculates and outputs a multiplication value of an input value from the filter 12 and an input value from the second differential calculator 20;
22 is an input value from the delay element 13 and the first differential calculator 1
A second multiplier 23 calculates and outputs a multiplied value of the input value from the input unit 9 and outputs a difference between the output value from the first multiplier 21 and the output value from the second multiplier 22. Output subtractor,
Reference numeral 24 denotes a first square calculator for calculating and outputting the square value of the input value from the Hilbert transform filter 12, and reference numeral 25 denotes a second square calculator for calculating and outputting the square value of the input value from the delay element 13. The square operator 26 is a first and second square operator 24, 25
Adder for adding and outputting the output values of
This is a divider that calculates and outputs a division value using the output value from the dividend as a dividend and the output value from the adder 26 as a divisor.

Next, the operation of this embodiment will be described. In the first embodiment described above, the differential amount Y (x) of φ (x) is converted to the reproduction signal e ₀ (x).
Of was calculated from the differential value of the arctangent of the ratio of the Hilbert transform value e _h (x) and the reproduced signal e ₀ (x), the molecules in the last term in equation _{(11), e y (x} ) · e x the _{'(x) -e x (x} ) · e y' (x) the dividend, the denominator, by obtaining a quotient which is a ^{_{e x 2 (x) + e}} y 2 by the divisor (x), in the same manner as in example 1 The magnetization reversal position is obtained irrespective of θ. By the way, from the equations (11) and (14), the following equation (1
5) is obtained.

[0029]

(Equation 6)

Therefore, e _h (x) · e ₀ ′ (x) −e ₀ (x) · e _h ′
It suffices to find a division value with (x) being the dividend and e ₀ ² (x) + e _h ² (x) being the divisor.

In FIG. 2, the analog reproduction signal e ₀ (x) input to the input terminal 10 is
, And the output signal is Hilbert-transformed by the Hilbert transform filter 12, and the output e _h (x) is applied to the first differential calculator 19 and the first square calculator 24. On the other hand, the digitally converted reproduced signal e ₀ (x) is converted by the delay element 13 into the Hilbert transform filter 1.
The delay of the calculation time at 2 is corrected and applied to the second differential calculator 20 and the second square calculator 25. Then, the reproduced signal e ₀ (x) calculated by the second differential calculator 20
Is the first derivative e ₀ ′ (x) and the Hilbert transform signal e _h (x)
And the multiplied values e _h (x) · e ₀ ′
(x) is obtained, and the differential value e _h ′ (x) of the Hilbert transform signal e _h (x) calculated by the first differential calculator 19 and the delayed reproduction signal e ₀ (x) are converted into the second multiplier 22 and their multiplied values e ₀ (x) · e ′ _h (x) are obtained.
The difference between the output multiplied values of the second multipliers 21 and 22 is
Required by Further, the square value e of the Hilbert transform signal e _h (x) calculated by the first square calculator 24
The sum of _h ² (x) and the square value e ₀ ² (x) of the reproduced signal e ₀ (x) calculated by the second square calculator 25 is obtained by the adder 26. Then, division is performed by the divider 27 using the output subtraction value from the subtractor 23 as a dividend and the output addition value from the adder 26 as a divisor, and Y (x) shown in Expression (15) is obtained. This output signal is converted into an analog signal by the D / A converter 17, the zero point position of the signal is detected, and the magnetization reversal position is obtained regardless of θ.

In the calculation of the digital quantity by the Hilbert transform filter 12 in the first and second embodiments, the equation (1)
The approximate expression shown in 6) is used,

[0033]

(Equation 7)

In practice, there can be no negative delay element,
As shown in Expression (17), the operation is further delayed by mT.

[0035]

(Equation 8)

FIG. 3 is a circuit diagram showing a specific example of the Hilbert transform filter 12 for performing the Hilbert transform based on the equation (17). The input terminal 30, the delay amount is (m-2) T,
A plurality of delay elements 31, 32, 33, 34, 35 of (m-1) T, (m + 1) T, (m + 2) T to 2mT, and amplification coefficients of 1 / mπ to 1 / 2π, 1 / π, 1 / π, 1 / 2π ~
A plurality of operational amplifiers 40, 41, 42, 4 of 1 / 2mπ
3, 44, 45, adders 46 and 47, an adder / subtractor 48, and an output terminal 49.

FIG. 4 is a circuit diagram showing a specific example of the differential calculators 16, 19 and 20.
1, an adder / subtracter 52 and an output terminal 53.

In each of the above embodiments, various operations are performed by a digital circuit. However, it is not always necessary to convert the reproduced signal into a digital signal, and the reproduced signal may be calculated by an analog amount. Although a filter for reducing noise and the like is not described, it is possible to insert a filter if necessary.

[0039]

As described above, according to the first aspect of the present invention, the Hilbert transform filter and the delay element for inputting together the signal reproduced from the magnetic recording medium, and the outputs of both the Hilbert transform filter and the delay element are provided. Divide one, the other
Divider for performing division as the divisor, the arctangent calculator for converting an output of the divider to the arctangent, and since having a differential calculator for differentiating the output of the arctangent calculator are reproduced from the magnetic recording medium Even if the reproduced signal is an asymmetrical waveform in which the vertical component and the longitudinal component are superimposed, the magnetization reversal position can be correctly determined even if the component ratio is not determined, even if the component ratio varies depending on the orientation ratio of the medium, recording conditions, etc. Thus, an output signal which can be detected can be obtained, and there is an effect that an inexpensive magnetic reproducing circuit can be obtained without requiring a circuit for calculating the component ratio or a means for maintaining the component ratio at a predetermined value.

According to the second aspect of the present invention, a Hilbert transform filter and a delay element for inputting both signals reproduced from a magnetic recording medium and a first differential operation for inputting both outputs of the Hilbert transform filter are provided. Multiplier, a first square arithmetic unit, a second differential arithmetic unit and a second square arithmetic unit for inputting both outputs of the delay element, and a multiplication of both outputs of the Hilbert transform filter and the second differential arithmetic unit Multiplier, a second multiplier for multiplying both outputs of the delay element and the first differential operation unit, and a subtractor for calculating a difference between both outputs of the first and second multipliers , An adder that calculates the sum of the outputs of the first and second square calculators, and a divider that performs the division using the output of the subtractor as a dividend and the output of the adder as a divisor. In addition to providing the same effects as the first aspect, Compared to the first invention, there is an effect that it is not necessary to perform complicated arctangent calculation performed by reading the pre-inverse tangent function characteristic values were written to the storage device such as a ROM.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the first invention of the present invention.

FIG. 2 is a block diagram showing a configuration of an embodiment of the second invention of the present invention.

FIG. 3 is a circuit diagram showing a specific example of a Hilbert transform filter in these embodiments.

FIG. 4 is a circuit diagram showing a specific example of a differential calculator in these embodiments.

FIG. 5 is a block diagram showing a configuration of a conventional reproducing circuit.

FIG. 6 is a time chart showing a reproduction signal and signal waveforms of a longitudinal component and a vertical component thereof.

[Explanation of symbols]

 Reference Signs List 12 Hilbert transform filter 13 Delay element 14 Divider 15 Arc tangent calculator 16 Differential calculator 19 First differential calculator 20 Second differential calculator 21 First multiplier 22 Second multiplier 23 Subtractor 24 First 1 square operator 25 second square operator 26 adder 27 divider

Claims (2)

(57) [Claims] 1. A Hilbert transform filter and a delay element for inputting both signals reproduced from a magnetic recording medium, a divider for dividing one of the outputs of the Hilbert transform filter and the delay element as a dividend and the other as a divisor, A magnetic reproducing circuit comprising: an arctangent calculator for converting an output of a divider into an arctangent; and a differential calculator for differentiating an output of the arctangent. 2. A Hilbert transform filter and a delay element for inputting both signals reproduced from a magnetic recording medium, a first differential calculator and a first square calculator for inputting both outputs of the Hilbert transform filter, A second differential operation unit and a second square operation unit for inputting both outputs of the delay element, a first multiplier for multiplying both outputs of the Hilbert transform filter and the second differential operation unit, and the delay element And a second multiplier for multiplying both outputs of the first differential operation unit,
A subtractor for calculating a difference between both outputs of the second multiplier, an adder for calculating a sum of both outputs of the first and second square calculators,
And a divider for performing a division using the output of the subtractor as a dividend and the output of the adder as a divisor.