JPH0548522B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a waveform equivalent circuit used for waveform correction of a reproduced waveform by a thin film magnetic head of a magnetic device.

A magnetic device records information on a magnetic recording medium and reproduces the recorded information using a magnetic head. In recent years, thin film magnetic heads have been widely used in order to achieve higher recording density and improved quality of reproduced information. During reproduction by this thin film magnetic head, negative peaks peculiar to the thin film magnetic head occur particularly at the rising and falling points of the solitary wave reproduction waveform, which is the reproduction signal at the magnetization reversal position of the recording magnetic medium.

This negative peak is a signal that does not correspond to recorded data, and in error rate characteristics, the amplitude margin decreases, significantly lowering the reliability of the signal reproduction system. Therefore, there is a need for a waveform equalization circuit that cancels negative peaks and narrows the half-width without damaging the recording/reproduction waveform.

[Conventional technology]

FIG. 5 shows a block diagram of a conventional waveform equalization circuit, and FIG. 6 shows a signal waveform diagram for explaining the operation of the conventional waveform equalization circuit.

That is, in FIG. 5, the input solitary wave reproduction signal A1 of FIG. 6 is converted into a signal A delayed by τ by a delay circuit 1 whose input is terminated with a resistor R0 and has a delay amount τ.
After that, it is input to the + end of the adder 2, which has a sufficiently large input impedance in proportion to the terminating resistor R0. At this time, due to the impedance mismatch, the signal A is reflected and sent back to the delay circuit 1 by τ
After the waveform shown in Fig. 6B is delayed, the attenuator 3
The signal is attenuated by a predetermined amount and becomes the signal shown in FIG. Adder 2 adds signal A and signal C and cancels the rising and falling points of signal A to obtain a sharp signal as shown in FIG. 6D.

[Problem that the invention seeks to solve]

The above waveform equalization circuit is an example of a circuit that corrects an isolated waveform caused by a conventional ferrite head.
When similar waveform equalization is applied to the reproduced signal of a thin-film magnetic head, due to the unique negative peak in the solitary wave reproduced waveform (see reproduced waveform diagram T2 in Figure 3), the reproduction signal is A negative peak occurs that does not correspond to the recorded data. For this reason, there is a problem in error rate characteristics, particularly in that the amplitude margin is reduced and the reliability of the signal reproduction system is significantly reduced.

Therefore, by having the function of removing the negative peak of the solitary wave reproduction waveform peculiar to thin-film magnetic heads and the function of sharpening the signal by narrowing the half-width of the signal, a signal suitable for reproduction signals of thin-film magnetic heads can be obtained. A waveform equalization circuit is required.

[Means for solving problems]

The present invention provides a waveform equalization circuit that solves the above-mentioned problems, and the means thereof includes, when a signal to be waveform equalized is input, a first delay circuit whose input end is terminated with a predetermined resistance value. , a second delay circuit having a different delay amount from the first delay circuit and connected in series thereto, and the second delay circuit having an output terminal connected to the first input terminal. Connect the terminating resistor and mismatched adder to one end of the input, and
a first attenuator whose input end is connected to the input end of the first delay circuit and whose output end is connected to the second input end of the adder; and an output end of the first delay circuit. and a second attenuator whose input end is connected to the third input end of the adder, and a second attenuator whose output end is connected to the third input end of the adder.

[Effect]

The waveform equalization circuit is an adder in which two delay circuits with different amounts of delay are connected in series, and the output terminal of the series delay circuit has an impedance mismatched with the terminal impedance of the input terminal of the series delay circuit. There are five types of delayed signals: an input wave delay signal obtained by connecting to one input terminal of the The five types of signal levels created above are attenuated by a predetermined amount in an attenuator in accordance with the negative peak shape of the input signal, and added in an adder to obtain the characteristics unique to thin-film magnetic heads. It cancels out the negative peak in the solitary wave and narrows the half-width of the waveform.

〔Example〕

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

FIG. 1 is a block diagram of a waveform equalization circuit according to an embodiment of the present invention, FIG. 2 is a signal waveform diagram for explaining the operation of this embodiment, and FIG. 3 is a reproduction signal waveform diagram of a thin film magnetic head. It shows.

As shown in the block diagram of FIG. 1, the waveform equalization circuit of this embodiment has a first delay having a delay amount τ2, in which the input terminal to which the reproduced signal of the magnetic head is input is terminated with a resistor 4 having an impedance R0. a circuit 5, a second delay circuit 6 connected in series with a delay amount τ1 different from that of the first delay circuit 5, and the terminating resistor 4.
an adder 9 whose first input terminal having an input impedance mismatched with the output terminal of the second delay circuit 6 is connected to the input terminal and the output terminal of the first delay circuit; The adder 9 includes first and second attenuators 7 and 8 that separately attenuate the signal at the point, that is, the reproduced signal and its delayed signal, by a predetermined amount and output the attenuated signals to the second and third input terminals of the adder 9. ing.

The operation will be explained with reference to the signal waveform diagram in FIG. That is, since the output of the second delay circuit 6 can be regarded as an open end, the signal is inverted here, propagates to the terminating resistor 4, and is terminated. As a result, two types of signals are added to the first attenuator 7: a signal with a delay amount of 0 and a signal with a delay amount of 2 (τ1 + τ2) with respect to the input of the waveform equivalent circuit (head reproduction signal) shown in FIG. 2E. , the second attenuator 8 receives a signal whose delay amount is τ2 with respect to the input of the waveform equalization circuit shown in FIG.
Two types of signals +τ2 are added. The adder 9 receives the output signal of the delay circuit 6 (FIG. 2G) and four types attenuated by a predetermined amount corresponding to the negative peak of the reproduced signal by the attenuators 7 and 8, for a total of five types. Signals with time differences are input and added.

At this time, the delay amounts τ1 and τ2 of the delay circuits 5 and 6 are set to (T1/2)≦τ1≦(3T1/2) and T2−(T1 /2)≦τ1+τ2≦T2+(T1/2)
By setting so as to satisfy the above conditions, it is possible to cancel out negative peaks in solitary waves peculiar to thin-film magnetic heads, and to narrow the half-width of the reproduced signal. Further, the attenuation ratio K2 of the first attenuator 7 is approximately the same as the ratio of the positive peak height to the negative peak height of the isolated waveform, and the attenuation ratio K1 of the second attenuator 8 is set to the same level as the ratio of the positive peak height to the negative peak height of the isolated waveform. It is sufficient to set the value to a value that makes waveform interference between bits sufficiently small. In addition, although two delay circuits are used in the explanation of the embodiment of the present invention,
Using one delay circuit with an intermediate tap, we get
Furthermore, it goes without saying that the number of parts used can be reduced and the circuit can be simplified.

FIG. 4 shows a block diagram of a waveform equalization circuit according to another embodiment of the present invention.

The difference from FIG. 1 is that the delay circuit 11,
12 and the attenuation ratio of attenuators 13 and 14. In this embodiment, it is possible to set optimal equalization conditions that correspond to changes in circumferential speed depending on the radial position of the disc-shaped recording medium, so it is possible to obtain high-quality signals at all radial positions of the head, and the device is can significantly improve reliability.

〔Effect of the invention〕

As explained above, according to the present invention, with a relatively simple circuit configuration, it is possible to remove the negative peak in the solitary wave reproduction waveform peculiar to a thin-film magnetic head, and to narrow the half-width of the waveform. ,
This has a great effect on improving the reliability of the thin film magnetic head signal reproduction system.

[Brief explanation of the drawing]

1 and 2 are a block diagram of a waveform equalization circuit according to an embodiment of the present invention and a signal waveform diagram for explaining the operation of the circuit. FIG. 3 is a reproduction signal waveform diagram of a thin film magnetic head, and FIG. FIG. 4 shows a block diagram of a waveform equalization circuit according to another embodiment of the present invention, FIG. 5 shows a block diagram of a conventional waveform equalization circuit, and FIG. 6 explains the operation of the conventional waveform equalization circuit. FIG. In the figure, 1, 11, 12 are delay circuits, 2 is an adder, 3, 13, 14 are attenuators, 4 is an input termination resistor, 5 is a first delay circuit, 6 is a second delay circuit, 7 8 represents a first attenuator, 8 represents a second attenuator, 9 represents an adder, and 10 represents an equalization condition setting circuit.

Claims (1)

[Claims] 1. A first delay circuit whose input terminal, into which a signal to be waveform-equalized, is input is terminated with a predetermined resistance value;
a second delay circuit having a different delay amount and connected in series with the delay circuit;
an adder that is mismatched with the terminating resistor, the output end of which is connected to the first input end of the delay circuit; , and a first attenuator whose output end is connected to the second input end of the adder, and whose input end is connected to the output end of the first delay circuit,
and a second attenuator whose output terminal is connected to the third input terminal of the adder.