JPS62128607A - Waveform equalizing circuit - Google Patents

Abstract

PURPOSE:To reduce the peak shift as well as the effects of external noises by shaping the waveform read out of a magnetic head and reducing the half value width. CONSTITUTION:A differential amplifier 1 has a very large input impedance and a delay line 2 has a delay amount taud connected to the differential input terminal of a differential amplifier 1 via the 1st and 2nd resistances Rb used for setting the waveform equalization factor K. A signal source 3 is connected to a positive input terminal (a) of the amplifier 1 via the 3rd resistances Ra used for setting the factor K. Then a signal source 4 is connected to a negative input terminal (b) of the amplifier 1 via the 4th resistance Ra used for setting the factor K. Both sources 3 and 4 deliver the differential signals. Here the 5th and 6th resistances Rc are matched with the characteristic impedance R0 of the line 2 together with the 3rd/4th and 1st/2nd resistances Ra and Rb respectively and therefore earths to both ends of the line 2.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a waveform equalization circuit included in a readout circuit of a magnetic recording device, and is applied to shape the waveform read from a magnetic head and improve the quality. It is something to do.

[Conventional technology]

When attempting to increase the density of magnetic recording in a magnetic disk device, interference between the waveforms of read signals causes stain pressure, lowering of the signal level, and pattern peak shift.

Signal detection performance is degraded. For this reason, a waveform equalization circuit is applied to the readout circuit to narrow the half-width of the readout waveform to reduce mutual interference between waveforms, thereby reducing the voltage level drop and pattern peak shift. .

Figure 3 shows 2For example, 2Japan Communication Technology Co., Ltd.'s technical report NK.
This is an example of a waveform equalization circuit using a conventional delay line, which is detailed in ``Reproduction Waveform Modification in Magnetic Recording'', 6759r. In the figure, (1) is a differential amplifier with very large input impedance fi, and (2) is the delay amount τ
d is a delay line with characteristic impedance 0! 0. (
31 represents the read signal source of the magnetic head with equal constraints, and Ra and Rc are resistances. Here “b”
+ ``c'' determines the waveform equalization rate K, and the combination of ``a+''b+ RC matches the characteristic impedance RQ of the delay line.

Next, the operation will be explained.

Consider the case where a solitary wave n(t,) is input through the signal line (3). At this time, a differential form of the arctangent function is assumed as E(().

When this signal B(i) is input, a voltage is generated at the matching end (1) of the delay line (2).

The voltage generated at this matching terminal is divided into multiple parts by the resistance line and R8, and the voltage is inputted to the negative input terminal of the differential amplifier (1).

On the other hand, the reflection end (b) of the delay line is not matched by characteristic impedance, and in this case, the signal input from the matching end (a) is totally reflected at the reflection end (b) after a delay time τd. At that time, a voltage twice as high as the input signal voltage (from the matching end (a)) is generated at the reflection end.

When inputting a signal E(t) from signal source (3) 2
A voltage is generated at the reflective end (b).

Therefore, the output of the differential amplifier is And then.

becomes.

Here, if we replace t-τd with t.

This waveform equalization circuit multiplies the sum of a signal delayed by a time τd and a signal advanced from the original waveform signal to the waveform equalization rate.

The difference between the two will be output. Figure 4 shows the effect of this waveform equalization, in which (a) is an input isolated waveform with a half-width W50, (b) is a signal that is advanced by time τd and multiplied by the waveform equalization rate, and Delayed by time τd,
Shows the signal multiplied by the waveform equalization rate. (C) is a solitary wave after waveform equalization, and as shown in Fig. 91, the half-width after iso-death is narrower than before equalization.

[Problem that the invention seeks to solve]

In general, magnetic disk drives use
Inputs and outputs of signal processing circuits are often configured in a differential manner. However, as shown in Figure 3, the conventional waveform equalization circuit does not have a differential input, so it is difficult to destroy the differential system in this part, and the signal-to-noise ratio is low against external noise. This will lead to deterioration.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a circuit that performs waveform equalization on differential inputs and reduces peak shifts.

[Failure to solve the problem]

In the waveform equalization circuit of the magnetic disk device according to the present invention, a delay line is connected between the positive and negative input terminals of a differential amplifier via a resistor, and the differential signal waveform input to the waveform equalization circuit is It is connected to the positive and negative input terminals of the differential amplifier via the terminal.

[Effect]

The waveform equalization circuit according to the present invention has a differential configuration for both input and output, and the waveform is equalized and amplified, so that peak shift can be reduced without deteriorating the signal-to-noise ratio.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. This waveform equalization circuit performs multi-waveform equalization by multiplying the input signal Ft(t,) by a waveform equalization rate and further subtracting a signal delayed by the delay amount τd.

In Figure 1, (1) is a differential amplifier with a very large input impedance, and (2) is a first set of waveform equalization ratio settings at the differential input terminal of differential amplifier (1).
．． L (31 is the positive input terminal (a) of the differential amplifier (1)
) is a signal source connected to a third resistor for setting the waveform equalization rate, and (41 is a differential amplifier (1)
It is a signal source that is connected to the negative input terminal (1) of the signal generator (1) via the 40th wire resistor Ra for setting the waveform equalization rate, and outputs a differential signal together with the signal source (3).

Also, the capital is the third. Fourth and first. Second resistance~+”
b and the characteristic impedance PL of the delay line (2) (,
A fifth . This is the sixth resistance.

At this time, the characteristic impedance 0 of the delay line (2) is matched by each resistor, and the signal source (3), (41
Suppose that the output impedance of the differential amplifier (1) is very small, and the input impedance of the differential amplifier (1) is very large.

is the consistency condition.

Next, the operation of this waveform equalization circuit will be explained.

E(t
) and −E(t) are input. At this time,
A voltage KoFi(t) KI B(t-τd) is generated at the input terminal (a) of the differential amplifier (11). In this figure, KIB(-τd) is shown in the same figure (b), and KoE(t)-
1B (-τd) is shown in the same figure (c). Further, a voltage of opposite polarity to this voltage is also generated at the other input terminal (bJ) of the differential amplifier (1).

At this time, the waveform equalization rate is It can be expressed as

That is, this waveform equalization circuit can operate on the isolated wave g(t,) by multiplying the waveform by the waveform equalization rate and further subtracting a signal delayed by the delay amount τd.

In this way, according to the above embodiment, a differential signal is input to the positive and negative input terminals of the differential amplifier through the respective resistors, and this input signal is attenuated by the voltage dividing resistor, and is then input through the delay line. Since the signal is supplied to each other terminal of the differential amplifier, the half width W50 can be narrowed, and the influence of external noise can also be reduced.

In the explanation of this waveform equalization circuit, we have shown an example where a symmetrical solitary wave is input as shown in Figure 2.1 For example, depending on the conditions of the recording medium or magnetic head, the solitary wave itself may not be symmetrical. There is also. For example, even in the case of the solitary wave shown in FIG. 5, by applying this waveform equalization circuit, it is possible to narrow the half-width W50.

〔Effect of the invention〕

As described above, the waveform equalization circuit according to the present invention shapes the waveform read from the magnetic head.

By reducing the half width W50, the peak shift (Q
) It is possible to reduce the noise and at the same time reduce the influence of external noise, making it possible to realize a highly reliable readout circuit.

[Brief Description of the Drawings] Figure 1 is a circuit diagram of a waveform equalization circuit according to an embodiment of the present invention, Figure 2 is a diagram simulating the principle of waveform equalization according to the present invention, and Figure 3 is a diagram of a conventional waveform equalization circuit. The circuit diagram of the equalization circuit, FIG. 4 is a diagram simulating the principle of conventional waveform equalization, and FIG. 5 is a diagram simulating the principle of another waveform equalization according to the present invention. In the figure, (1) is a differential amplifier, (2) is a delay line, (3) is a signal source, and ~ is a third . The fourth resistor, FLb, is the first resistor. The second resistance, Rin. is the fifth. This is the sixth resistance. Note that the same reference numerals in the two figures indicate the same or corresponding parts.

Claims (1)

[Claims] In a waveform equalization circuit included in a signal readout circuit of a magnetic recording device, first and second resistors are connected to two positive and negative input terminals of a differential amplifier, and the other terminals of the first and second resistors are Each of the differential input signals is connected to a delay line having two connection terminals, and each of the positive and negative polarity signals of the differential input signal is connected to the two positive and negative input terminals of the differential amplifier via a third and fourth resistor. The two connection terminals of the delay line have a fifth,
A sixth resistor is connected and the other is grounded, and the matching with the characteristic impedance of the delay line is determined by the first,
A waveform equalization circuit characterized in that it is implemented by a combination of second, third, fourth, fifth, and sixth resistors.