JPS6159664A - Waveform equalizing circuit - Google Patents

Abstract

PURPOSE:To improve error rate characteristics and the reliability of a thin film head signal reproducing system by obtaining the delay quantity of a delay element as a value specified by an isolated waveform having one positive peak point and two negative peak points of an input signal. CONSTITUTION:A waveform equalizing circuit consists of delay elements 5-8 having delay quantities tau1-tau4 respectively, a terminal resistance R0, attenuators 9-12 having attenuation quantities K1-K4 respectively, and an adder 13. Intervals of time between the positive peak point and two negative peak points are denoted as T1 and T4 and half-amplitude levels of the positive waveform of the isolated waveform are denoted as T2 and T3 with the positive peak point as the boundary with respect to the isolated waveform having one positive peak point and two negative peak points of the input signal supplied to an input terminal 14, and correcting values alpha1 and alpha2 are set to satisfy a formula I, and in this case, delay quantities tau1-tau4 are obtained in accordance with formulas II. This waveform equalizing circuit is used to improve the error characteristic, and the reliability of the thin film head signal reproducing system is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a waveform equalization circuit that corrects distortion of a reproduced signal or the like caused by a thin film head of a magnetic disk device.

In recent years, technological advances in magnetic disk drives have been remarkable, and in particular, the development of thin film heads has significantly improved the trend toward higher density. However, the thin film head is characterized by the generation of a unique negative peak waveform when reproducing an isolated waveform, and since this degrades the reliability of the signal reproducing system, countermeasures are desired.

[Conventional technology]

As a conventional waveform equalization circuit, there is a cosine type waveform equalization circuit whose configuration is shown in FIG.

In the figure, the reproduced signal is input to a termination resistor RO, and after being delayed by a time τ by a delay element 1 having a delay amount τ, it is input to an adder 2 having a sufficiently large input impedance compared to the termination resistor RO. be done.

At this time, the signal is reflected due to the impedance mismatch, is delayed by the delay element 1 again by the time τ, is attenuated by the required amount by the attenuator 3 together with the human input signal, and is sent to the adder with the opposite polarity to the reflective end of the delay element 1. is input.

FIG. 6 shows a waveform diagram of each part of the 51st part. In the figure, when an isolated waveform A having a half-width Wi is applied to the input terminal, a waveform B delayed by a certain amount of time from the solitary wave enlargement appears on the output side of the delay element 1, and becomes large due to the reflection effect due to impedance mismatch. It appears.

Also, due to the reflection effect, the waveform that passes through the delay element 1 in the opposite direction is further delayed by a time τ from the waveform B, and becomes an isolated waveform A.
Together, a composite waveform C is formed, which is attenuated by the required amount in an attenuator 3, and is input into the negative side input terminal of the adder 2 as a waveform. Therefore, the output of the adder 2 becomes a waveform E which is narrowed in the half width direction by subtracting the waveform difference from the waveform A.

Such a cosine waveform equalization circuit is used to correct the solitary wave reproduced waveform by a conventional ferrite head. The same figure (
As shown in bl, since the unique negative peak in the solitary wave reproduced waveform is not removed, a peak waveform that does not correspond to the recorded data occurs in a part with a wide bit interval. Therefore, in terms of error rate characteristics, in particular, the amplitude margin is reduced, which has the disadvantage of significantly lowering the reliability of the signal reproduction system.

[Problem that the invention seeks to solve]

In view of the above-mentioned conventional drawbacks, the present invention provides a thin-film head with a function of removing the negative peak peculiar to the thin-film head in addition to the conventional waveform equalization means that narrows the half-width of the solitary wave reproduced waveform. The purpose of this invention is to provide a waveform equalization circuit suitable for reproduced signals.

[Means to solve the problem]

According to the present invention, this purpose is to provide a waveform equalization circuit comprising a delay element whose output terminal is terminated, an attenuator, and an adder, in which each of the delay elements has a delay amount of τ1.
τ2. τ3. For an isolated waveform composed of four series delay elements with τ4 and having one positive peak point and two negative peak points, which are the human input signals of the series delay elements,
The time intervals between the positive peak point and each of the two negative peak points are set as TI and T, respectively, and the half-width of the positive waveform of the isolated waveform is set as TZ + T3 with the positive peak point as the border, and a correction value is calculated. α8. α2 respectively (T2/2) > α1
> (-rz/2), (T3/2) >αz >(
This is achieved by providing the waveform equalization circuit of the present invention, which is characterized in that the respective delay amounts are calculated using the following formula (%).

[Effect]

That is, the present invention uses a reproduced signal waveform delayed by a delay element, and by appropriately selecting the delay amount of the delay element, cancels out the negative peak in the solitary wave reproduced waveform peculiar to thin-film heads and narrows the half-width. By doing so, the quality of the reproduction signal of the thin film head is improved.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a block diagram of a waveform equalization circuit according to the present invention. In order to make the explanation of the configuration and operation easier to understand, the same parts as in the previous time are given the same reference numerals.

In FIG. 1, numbers 5 to 8 each have a delay amount of τ1°τ2.
τ3. τ4 is the delay element, RO is the terminating resistor, 9 to 12
are the attenuation amounts K+, KZ, and 3, respectively. 4 is an attenuator, 13 is an adder, 14 is an input terminal, and 15 is an output terminal. Further, F- is an output waveform diagram of the first answering section as shown in FIG. Below, with reference to Figure 2, the first
The effect of the diagram will be explained.

In both figures, the input signal (solitary wave reproduction waveform A output from the thin film head) applied to the input terminal 14 is transmitted to the delay element 5.
.about.8 in series and is terminated by a terminating resistor Ro. On the other hand, these four types of delay elements 5 to 8 produce 5 with a time difference.
types of signals can be obtained. Among the five types of signals, delay element 6
The four types of signals F, G, I, and J, except for the output signal H, have attenuation amounts of +, Kz, and 3. It is attenuated by attenuators 9 to 12, which are 4 attenuators. These signals are routed together to summation 513.

The adder 13 sets the output signals of the attenuators 9 and 12 to be positive, based on the polarity of the unattenuated signal H, and the attenuator 10
Addition processing is performed by setting the output signals of and 11 as negative.

As mentioned above, FIG. 3 shows the solitary wave reproduction waveform output from the thin film head, and corresponds to signal A in FIG. 2. This waveform A has one positive peak point P and two negative peak points Q.
and R, and let the time difference between point P and point Q be T, and the time difference between point P and point R be T4. Also, level 5 of P point
The time width (half width) of the 0% level is T, with the vertical axis of point P as the border.
2+T3.

Next, the correction value for correcting the delay amount of each delay element is α
1. As α2, (T2/2) > α+ > (-Tz/2) (T3/2
) > α, > (-T3/2), each delay amount is calculated using the following formula 1% to cancel out the negative peak in the solitary wave peculiar to the thin-film head and narrow the half-width. be able to.

Adding waveform F and waveform J to waveform H in FIG. 2 means that the level value is the same as waveform A of the input signal, and the delay amount τ1
It has the effect of canceling out the negative peak values QO and Ro of the waveform H delayed by +τ2. Therefore, the positive peak value Ql of waveform F and the positive peak value R1 of waveform J are respectively Qo=Q
, The attenuation amount KI and 4 may be set so that Ro=R+.

Also, subtracting waveform G and waveform ■ from waveform H is as follows:
It acts to narrow the half width of waveform H.

Therefore, the attenuation amounts 2 and 3 of the attenuators 10 and 11 may be set to values that sufficiently reduce waveform interference between adjacent bits in the reproduced signal. The correction values α1 and α2 define a range of set values for correction based on the unique reproduction characteristics of the thin film head.

An example of the results of waveform equalization according to the present invention is shown in the waveform (Q
)It was shown to.

〔Effect of the invention〕

As explained in detail above, according to the waveform equalization circuit of the present invention, it is possible to remove the negative peak in the solitary wave reproduction waveform peculiar to thin-film heads, and the half-value width is also narrowed, thereby improving error rate characteristics. It also has a great effect on improving the reliability of the thin film head signal reproducing system.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the waveform equalization circuit according to the present invention, Fig. 2 is an output waveform diagram of the first response section, Fig. 3 is a solitary wave reproduction waveform output from the thin film head, and Fig. 4 is a solitary wave reproduction waveform diagram. A diagram showing a comparison example of a conventional equivalent waveform (b) for waveform (al) and an equalized waveform (C) according to the present invention. 5 shows an output waveform diagram of the answering section. In the figure, 5 to 8 are delay elements whose delay amounts are τ, τ2, τ3, and τ4, 9 to 12 are attenuators,
13 is an adder, P is a positive peak point, and Q and R are negative peak points, respectively. 6

Claims (1)

[Scope of claims] In a waveform equalization circuit comprising a delay element whose output end is terminated, an attenuator, and an adder, the delay elements have delay amounts of τ_1, τ_2, τ_3, and τ_4, respectively.
For an isolated waveform composed of one series delay element and having one positive peak point and two negative peak points, which are the input signals of the series delay element, the positive peak point and two negative peak points The time intervals between each negative peak point are T_1 and T_, respectively.
4, the half-width of the positive waveform of the isolated waveform is T_2+T_3 with the positive peak time as the border, and the correction value α_1,
α_2 is (T_2/2)>α_1>(−T_2
/2), (T_3/2)>α_2>(-T_3/2), each delay amount is determined by the following formulas τ_1+τ_2=T_1+α_1 τ_2=T_2+α_1 τ_3=T_3+α_2 τ_3+τ_4=T_4+α_2 Waveform equalization circuit.