JPH025204A - Digital magnetic recording/reproducing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a digital magnetic recording and reproducing device, and in particular, the present invention relates to a digital magnetic recording and reproducing device, which has a plurality of reproducing heads that respond anisotropically to the direction in which a recording medium is transported; At least one of the playback heads
The present invention relates to a digital magnetic recording and reproducing apparatus in which the direction of anisotropic response of one or more read heads is opposite to the direction of anisotropic response of other read heads.

[Conventional technology]

Generally, when reproducing digital data, the reproduced waveform may differ from the recorded waveform due to the transmission characteristics of the recording medium or the reproducing head. Such deterioration of the reproduced waveform increases as the recording density increases, and in order to detect correct digital data from this reproduced waveform, it is necessary to perform waveform equalization on the reproduced waveform.

Various waveform equalization devices for performing waveform equalization on reproduced waveforms have been proposed in the past, but a transversal filter as shown in FIG. 8 is often used for membrane power. Also,
Such a transversal filter can be digitized by using a register as a delay element and a digital multiplier as a coefficient unit. In this case, there is a method of storing tap coefficients in ROM etc. Often used.

In addition, in recent years, digital magnetic recording and reproducing devices configured to allow editing of recorded data have been proposed.
These devices often have multiple playback heads.

[Problem to be solved by the invention]

By the way, a reproducing head having a magnetoresistive effect (referred to as an MR head) is often used as a reproducing head in a high-density magnetic recording/reproducing device because it is easy to make a thin film. As shown in , recording medium 1
It is often asymmetrical with respect to the running direction of 4. When recorded data is reproduced using an MR head having such an asymmetric structure, the reproduced waveform becomes an asymmetric waveform in the time axis direction.

In the above MR head, as shown in FIG. 9, as the magnetic field H4 applied to the magnetoresistive element (hereinafter referred to as MR element) 12 increases, the output also increases. Further, the magnetic field H, applied to the MR element 12 in the MR head is set when the distance between the upper yoke 11 and the point on the recording medium 14 where the magnetization is reversed (hereinafter referred to as the magnetization reversal point) is the minimum, that is, It reaches its maximum at time T□8 in the positional relationship as shown in FIG.

Now, the recording medium 14 is moving from the upper yoke 11 to the lower yoke 1.
3, that is, in the direction shown by the arrow in FIG. Since the magnetic property is high and the upper yoke thickness S and lower yoke thickness Q have a relationship of S<Q, the results are as shown in FIGS. 10(a) and 10(b).

In other words, Δ is set at the time of the extraction section (T s
aw−Δt), as shown in FIG. 10(a), MR
The magnetic field H, applied to the MR element 12 is reduced by ΔH from the maximum magnetic field applied to the MR element 12, that is, the applied magnetic field H, □ at time T II a
-ΔH).

However, the time (Twax
+Δt), as shown in FIG. 10(b), the lower yoke 13 is formed thicker than the upper yoke 11, so the magnetic field is mainly distributed to the lower yoke 13. As a result, the magnetic field H1 applied to the MR element 12 is (H,□-
ΔH, ) (where ΔHu>ΔH).

Therefore, from time (T,□−Δt) to time (Twax+
The magnetic field H, applied to the MR element 12 until Δt) becomes a distribution curve as shown in FIG.
M from T,□-Δt) to (T1.yo+Δt)
The reproduction output of the R head is as shown in FIG. 11(b).
If the peak point at time T, □ is the center, the waveform will be asymmetrical in the time axis direction.

However, the MR head shown in FIG.
If it is placed opposite to the running direction of , the time (T, , -
The magnetic field flows at Δt) and (T, , +Δt) are as shown in FIGS. 12(a) and 12(b), respectively. Therefore,
MR from time (T,□-Δt) to (T□8+Δt)
The magnetic field H4 applied to the element 12 and the reproduction output of the MR head form a distribution curve as shown by the solid line in FIGS.
The waveform is different from the distribution curve shown by the broken line in FIGS. 3(a) and 3(b).

Now, as shown in FIG. 8, waveform equalization is performed using an n-tap transversal filter with the reproducing head positioned as shown in FIG. 9 with respect to the transport direction of the recording medium 14. The optimal equalization tap coefficient of T F 01
If T r + + ..., T11, then
If the reproducing head is arranged opposite to the transport direction of the recording medium 14 as shown in FIG. 12, the reproduced waveforms will be different as shown in FIGS. 13(a) and (b), so the tap coefficient T
F 01 T F I + . . . T F+s- cannot perform optimal equalization.

When playback heads with apparently opposite anisotropic responses coexist, if one is selected from the outputs of multiple playback heads to perform correct equalization, the anisotropic response When a playback head in the opposite direction is selected, a new tap coefficient must be set, which results in an increase in the number of hardware and steps.

[Means to solve the problem]

In order to solve the above-mentioned problems, the digital magnetic recording and reproducing apparatus according to the present invention is provided with a plurality of independent reproducing heads that respond anisotropically to the transport direction of the recording medium. In a magnetic recording/reproducing device in which the direction of the anisotropic response of at least one read head is opposite to the direction of the anisotropic response of the other read heads, among the reproduction signals of the plurality of read heads, , a digital transversal filter for waveform equalization, and means for providing a plurality of tap coefficients to the digital transversal filter, and the reproduction signal selected by the selection means is reproduced. The transversal filter is characterized in that the arrangement order of the tap coefficients of the transversal filter is reversed, either forward or backward, depending on the direction of the anisotropic response of the reproducing head.

[For production]

Assume that in the digital magnetic recording and reproducing apparatus of the present invention, a certain reproducing head reproduces a signal recorded on a recording medium and a reproduced waveform shown in FIG. 11(a) is obtained. When this reproduced waveform is sampled at intervals of the tap interval Tb and subjected to waveform equalization using a digital waveform equalizer having 2N+1 taps, a waveform as shown in FIG. 11(b) is obtained.

The tap coefficient at this time is F −Hz F−N+1+
...Fll+ ...FM-1+ If it is FM, the value Y7 of each sampling point after waveform equalization is
becomes.

Now, if we consider the case where the direction of the anisotropic response of the reproducing head is reversed, the reproduced waveform in that case will be inverted in the time axis direction. In other words, if sampling is performed at the same timing, the value at each sampling point will be S''□, = S□, (-■ < m < Korea). If this waveform is equalized with the above tap coefficient, ( −ψ<J<oo) Therefore, equalization is performed by reversing the arrangement order of the tap coefficients, that is, the tap coefficients are changed to F′,=F −4(
-N < j < N), the value of the sampling point after equalization is -Y, .

(-■<l<oo) becomes.

In other words, as shown in FIGS. 7(a) and (b), if the direction of the anisotropic response is reversed, by reversing the arrangement order of the tap coefficients, the waveform after equalization will be anisotropic. It becomes equal to the waveform after equalization before reversing the direction of the sexual response.

In this way, the hardware and process that occur when setting new tap coefficients by reversing the arrangement order of the optimal equalization tap coefficients for a certain playback head and equalizing a reproduced waveform with an opposite anisotropic response. The increase in number can be kept to a minimum, and the same level of equalization can be achieved.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 7. In this embodiment, a magnetic tape 6 is used as a recording medium, and a 7-tap digital waveform equalizer 5 is used as a digital transversal filter for waveform equalization.

As shown in FIG. 1, playback heads (1-1) to (1-N
) are respectively amplified by amplifiers 2, . is a natural number) and is input to a waveform equalizer 5 which is constituted by a digital transversal filter for waveform equalization.

In the waveform equalizer 5, as shown in FIG. 2(a), the input sampling data is stored in memory cells 51a to 51f.
The signal is inputted to a shift register 51 consisting of. The shift register 51 has an output for each tap interval Tb, and each output and input sampling data are input to each multiplier 52a to 52g, and the second
It is multiplied by the tap coefficients T0 to T read out from the ROM 56 shown in FIG. The outputs of each of the multipliers 52a to 52g are input to an adder 54, and the output of the adder 54 is configured to be guided to a subsequent circuit as geometric conversion data.

The ROM 56 shown in FIG. 2(b) has a playback head (1-
n) tap coefficients 00 to C8 are, for example, addresses O to 6.
The tap coefficients C0 to C6 stored in the address of the ROM 56 according to the output of the address generator 55 are
It is designed to be output from 56.

The output of the address generator 55 is also input to a decoder 57, and this decoder 57 receives the tap coefficient C.

It has the same number of outputs as ~C4, for example, if the input is "0"
”, then the output Y0 is “1”, and when the input is “5”, Y,
becomes 1”.

Outputs Y0 to Y6 of the decoder 57 are input to a reversing circuit 58. In the reversing circuit 5B, the first
The playback head (1-
An identification signal (2) is input such that if the anisotropy of 1) to (1-N) is in the same direction as the reproducing head (1-n), it is "0", and if it is in the opposite direction, it is "1".

The reversing circuit 58 has a configuration as shown in FIG. 3, and outputs the signals input to the "1" and "0" sides depending on the state of the identification signal (2). That is, if the identification signal ■ is "O", the outputs Z0 to Z6 become Zo = Yo, Z+ -Y+, ... Zb - Yh, and if the identification signal ■ is "1", the outputs 20 to Z6 are as follows. Zo = Yh - Zl = Ys 1 ... Zb - Y (1
becomes.

The output of the reversing circuit 58 and the output of the ROM 56 are input to a tap select circuit 59. The tap select circuit 59, as shown in FIG.
The output of the ROM 56 is input to the data inputs of 159a to 59g, while the outputs Z0 to Z of the reversing circuit 58 are input to the respective clock inputs. Therefore, the outputs T0 to T of the tap select circuit 59 are the same as those of the reversing circuit 58.
The output of the ROM 56 when the outputs Z0 to Zb rise from O'' to 11'' is output.

In this way, when the identification signal (2) is "0", as mentioned above, Zo "Yo + ... Z h = Y h, so the outputs T0 to T of the tap select circuit 59.

is the rise R of Z0~Z&, that is, Y0~Y
This becomes the output of OM56.

Therefore, the outputs T, ~T6 of the tap select circuit 59 are To''Co, Tt = Ct, ...T
b=Cb, and is input to the multipliers 52a to 52g. The timing chart at this time is as shown in FIG.

On the other hand, when the identification signal ■ is "1", as mentioned above,
Z,=I=Yh,...Zb=Yo, so in the same way, To''' Cb, 'I'+ = Cs,...
・T h = C.

Therefore, the order of the tap coefficients is opposite to that when the direction of the anisotropic response is the same as that of the reproducing head (1-n).

The timing chart at this time is as shown in FIG.

On the other hand, for all of the reproducing heads (1-1) to (1-N), the direction of anisotropic response is measured in advance, and only those whose anisotropic response is opposite are registered in the selection circuit 3. As a result, the selection circuit 3 selects the registered playback heads (1-1) to (1).
-N) is selected, the identification signal ■ is set to "1".

In this way it becomes possible to identify the direction of the anisotropic response.

〔Effect of the invention〕

As described above, the digital magnetic recording and reproducing apparatus of the present invention is provided with a plurality of independent reproducing heads that respond anisotropically to the transport direction of the recording medium, and at least one of the reproducing heads In a magnetic recording/reproducing device in which the direction of the anisotropic response of the read head is opposite to the direction of the anisotropic response of the other read heads, one of the read signals of the plurality of read heads is selected. a digital transversal filter for waveform equalization, and means for providing a plurality of tap coefficients to the digital transversal filter, and the reproduction head is reproducing a reproduction signal selected by the selection means. The arrangement order of the tap coefficients of the transversal filter is reversed or reversed depending on the direction of the anisotropic response of the transversal filter.

In this way, by performing waveform equalization by reversing the order of the tap coefficients in the forward or reverse direction depending on the direction of the anisotropic response of the playback head, a playback head with an anisotropic response in the opposite direction can be selected. Since there is no need to set a new tap coefficient for when the anisotropic response is present, correct equalization can be performed regardless of the direction of the anisotropic response, and the hardware and number of steps can be reduced compared to conventional methods. It produces such effects.

[Brief explanation of the drawing]

1 to 7 show an embodiment of the present invention, in which FIG. 1 is a block diagram showing the main parts of a digital magnetic recording and reproducing device, and FIG. 2(a) is a waveform equalizer. 2(b) is a block diagram of a circuit that forms tap coefficients, FIG. 3 is a circuit diagram of a reversing circuit, FIG. 4 is a circuit diagram of a tap select circuit, and FIG. 5 is a block diagram of a circuit that forms tap coefficients. Timing charts of the signals in each part of a) and (b), and Fig. 6 shows each part of Fig. 2 (a) and (b) when reproduced with a playback head that has an anisotropic response opposite to that in Fig. 5. The timing charts of the signals in FIGS. 7(a) and 7(b) are explanatory diagrams showing the principle of the present invention, respectively. 8 to 13 show conventional examples, in which FIG. 8 is a block diagram showing a conventional transversal filter, FIG. 9 is a configuration diagram of an MR head, and FIGS.
) are explanatory diagrams showing the magnetic field distribution when the MR head is arranged in a certain direction with respect to the transport direction of the recording medium, and FIGS. 11(a) and (b) are respectively FIGS. 10(a) and (b).
) is a magnetic field-output characteristic diagram showing the relationship between the change in the magnetic field H& applied to the MR element and the head output in response to (
a) and (b) are explanatory diagrams showing the magnetic field distribution with the MR head placed in the opposite direction to those in FIGS. 10(a) and (b), respectively, and FIGS. Figure (a) (
FIG. 7 is a magnetic field-output characteristic diagram showing the relationship between the change in the magnetic field H8 applied to the MR element and the head output corresponding to (b). (1-1) to (1-N) are playback heads, 2 is an amplifier, 3
4 is a selection circuit (selection means), 4 is an A/D converter, 5 is a waveform equalizer (digital transversal filter for waveform equalization), 6 is a magnetic tape (recording medium), 51 is a shift register, 52a-- 52g is a multiplier, 54 is an adder, 55
is an address generator, 56 is a ROM, 57 is a decoder, 5
8 is a reversing circuit, and 59 is a tap select circuit. Patent applicant Sharp Co., Ltd. Old Figure 10 (b) Figure (b) Day 4 I'lt Figure 12 (a) Figure 13 (a) Figure 12 (b) Figure 13 (b)

Claims (1)

[Scope of Claims] 1. A plurality of independent playback heads that exhibit an anisotropic response with respect to the transport direction of the recording medium are disposed, and the anisotropic response of at least one of the playback heads is In a magnetic recording and reproducing device whose direction is opposite to the direction of the anisotropic response of other reproducing heads, selection means for selecting one of the reproduction signals of the plurality of reproduction heads and waveform equalization are provided. and means for providing a plurality of tap coefficients to the digital transversal filter; A digital magnetic recording/reproducing apparatus characterized in that the arrangement order of the tap coefficients of the transversal filter is reversed or reversed accordingly.