JPS60129971A - Equalization system of reproduced waveform - Google Patents

Abstract

PURPOSE:To improve the recording density by subtracting a waveform obtained through the proper adjustment of the amplitude of a second order differentiation of a reproduced waveform from the original reproduced waveform so as to apply more pulse slimming than that executed conventionally thereby decreasing the pattern peak shift. CONSTITUTION:A reproduced isolate pulse read magnetically from a recording medium is expressed in terms of a time function ''(t). The said reproduced isolate pulse ''(t) is differentiated by second order, a waveform K1''(t) obtained by multiplying a weight K1 to the result and a waveform ''(t)-K1''(t) is obtained by subtracting the K1''(t) from the original reproduced isolate pulse pulse waveform ''(t). Thus, pulse slimming is realized without producing the decrease of the amplitude before and after the waveform equalization.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a reproduction waveform equalization method in a magnetic recording device or the like.

[Technical background of the invention and its problems] At present, the capacity of magnetic recording devices continues to increase. Increasing capacity can be considered from two aspects: improvement in linear density and improvement in track density. Now, we will focus on improving the linear density.

As the linear density increases, the interval between adjacent magnetization reversals becomes smaller, and waveform interference becomes more significant. In order to suppress this waveform interference, waveform equalization is performed to improve the quality of the reproduced waveform. Specifically, an operation such as narrowing the width of the base of the isolated pulse (hereinafter referred to as pulse slimming) is performed using a circuit. Many methods have already been proposed as this equalization method. Here, the cosine equalization method, which is generally widely used, will be explained.

FIG. 1 is a diagram explaining the principle of the cosine equalization method. FIG. 1(a) shows isolated pulses read out from a recording medium by a magnetic head. Let this solitary pulse waveform be expressed by a time function j (ri). (b) is based on this regenerated solitary pulse, gives the regenerated solitary pulse a lead and a delay of time τ, and changes its amplitude to a weight. The two K K waveforms multiplied by
(t+τ) is shown. (c) is the sum of the waveforms of the two weighted reproduced isolated pulses given time advance and delay, that is, t) T (t + τ) + f (
t-τ)). (d) shows the waveform of (C) subtracted from the reproduction isolated pulse that is the reference of (a), that is, K f(ri-7(j(t+τ)+f(t-τ)), which is a cosine-shaped This is the final isolated waveform obtained by applying equalization. By performing the above series of operations, the base portion of the reproduced isolated pulse is removed, and a narrowed isolated pulse can be obtained.

However, as can be seen from the above description, in the cosine equalization method, the amplitude of the isolated pulse waveform after iso-death is smaller than the amplitude of the reproduced isolated pulse waveform before equalization. Therefore, it has the disadvantage that the threshold level must be set more strictly during demodulation.

[Object of the Invention] The present invention improves the drawbacks of the conventional waveform equalization method described above, and aims to provide a waveform equalization method that performs pulse slimming without causing a decrease in amplitude. be.

[Summary of the Invention] The present invention performs waveform equalization during reproduction and demodulation processes in a magnetic recording device by subtracting a waveform obtained by appropriately adjusting amplitude from a reproduced waveform to a waveform obtained by second-order differentiation of the reproduced waveform. , it is possible to realize pulse slimming without causing a decrease in amplitude before and after waveform equalization.

[Effects of the Invention] According to the present invention, pulse slimming can be realized without reducing the amplitude. As a result, the positional shift of the peak of the reproduced waveform due to waveform interference (hereinafter referred to as pattern peak shift) can be reduced, and the recording density can be improved by the margin generated.

[Embodiments of the Invention] The present invention will be described in detail. FIG. 2 is a diagram explaining the principle of the equalization method according to the present invention. (a) shows a reproduced isolated pulse magnetically read out from a recording medium, and is assumed to be expressed by a time function f (t). (b
) fl This is a waveform obtained by second-order differentiating this reproduced isolated pulse and multiplying its amplitude by a weight Kl, and is expressed as Kxf'' (1).
) is the waveform obtained by subtracting the waveform of f(t) K1 f'(
t). This waveform (c) is an isolated waveform finally obtained by applying the equalization of the present invention.

Comparing the reproduced isolated pulse before waveform equalization in (a) and the isolated pulse after waveform equalization in (C), it is clear that the amplitude has increased and pulse slimming has been performed.

A comparison between waveform equalization and cosine equalization according to the present invention is shown below.

First, let us consider to what extent an isolated pulse can be slimmed by the equalization method of the present invention without generating a condensed peak.

Assume here that the regenerated solitary pulse is expressed in Lorentzian form. Therefore, the isolated pulse waveform Fl(t) after applying the waveform equalization of the present invention is as follows: Fl(t) = f(t) - Kdτt) This post-mortem isolated pulse waveform Fl(t) has a condensation peak. In order to avoid this, there must be no solution for F2'(t) = 0 other than 1 = = Q. It is sufficient to satisfy this condition.

Assuming that we have the critical condition of hot weather, the isolated pulse waveform after waveform equalization is (from equation 81). The amplitude normalized to the amplitude of the isolated pulse before equalization is shown in Figure 4 (,i,).For comparison, the reproduced isolated waveform before equalization is shown in (h) and (k). It can be seen that the value has increased by a factor of 1, and the half width has also decreased.

Let us consider the first-order cosine equalization method. The isolated pulse p(t) after iso-death is shown as...(6). The conditions under which no condensation bias occurs when this cosine equalization is applied are given by: Now, considering the case where equality holds at the criticality of the condition that does not produce this condensed peak, 1 (= 0.5 = 1.37°) Applying this condition to equation (6)... (γ) The shape of the isolated waveform after cosine equalization is shown in Figure 3 (j).
FIG. 4(m) shows the amplitude normalized to the amplitude of the isolated pulse before equalization. As is clear from Figure 3, the amplitude of the isolated pulse subjected to cosine equalization is smaller than that of the isolated pulse before equalization, and the half-width is larger than that of the isolated pulse subjected to equalization according to the present invention. .

If K is set to a value larger than 0.5 under conditions that do not produce condensed peaks when performing the above cosine equalization, the half-width decreases,
Although the value approaches that of the equalization method according to the present invention, the amplitude decreases significantly. If K is set to a value smaller than 0.5, the amplitude will increase, but the half-width will also increase, and the shape will only approach that of the isolated pulse before equalization, but the effect of waveform equalization will become smaller.

Next, FIG. 5 shows an example of a circuit configuration for realizing the waveform equalization method of the present invention. In FIG. 5, reference numeral 1 denotes an input terminal to which a reproduced waveform is input. 2 is a timing adjustment circuit, 3 is 2
A rank divider, a 4-digit gain adjustment circuit, 5 is a differential amplifier, and 6 is the output terminal of the waveform after equalization.

The playback signal input to 1 is divided into two parts, one of which is
The signal is delayed for a certain period of time by the timing adjustment circuit 5 and reaches the differential amplifier 5. The other divided reproduced signal is divided into two orders by a 302-order differentiator, adjusted to an appropriate amplitude by a gain adjustment circuit 4, and inputted to a differential amplifier 5. The two input waveforms are subtracted in the differential amplifier 5 and output to 6.

The time delayed by the timing adjustment circuit No. 2 is set to be equal to the amount of time delay caused by the second order circuit No. 3 and the gain adjustment circuit No. 4. Moreover, with such a circuit configuration, the waveform equalization according to the present invention can be realized.

As described above, the present invention performs pulse slimming more than conventionally performed and reduces pattern peak shift by subtracting from the reproduced waveform a waveform in which the amplitude of the second-order waveform of the reproduced waveform is appropriately adjusted. This will improve recording density.

[Brief explanation of drawings]

Fig. 1 is a diagram for explaining the principle of the cosine equalization method, Fig. 2 is a diagram for explaining the principle of the equalization method according to the present invention, and Figs. 3 and 4 are diagrams for explaining the principle of the cosine equalization method. FIG. 5 is a diagram for comparing the effects of the equalization method according to the present invention and FIG. 5 is an example of a circuit configuration for realizing the equalization method according to the present invention. 2...Timing adjustment, 3...Second floor number divider 4...
・Gain Adjustment Circuit Agent Patent Attorney Noriyuki Chika (and 1 other person) No. 1
Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] An appropriate method for converting a reproduced waveform into a second-order differential waveform of the reproduced waveform during the reproduction and demodulation processes in a magnetic recording device.