JPH03104059A - Waveform correcting device for input signal - Google Patents

Abstract

PURPOSE:To make a waveform optimumly thin even to an asymmetric waveform by correcting an input signal with a correcting signal for which the delay time of the input signal is set based on the waveform of the input signal and a rate is determined to attenuate the input signal. CONSTITUTION:A delay signal output part 1 outputs the input signal while being delayed based on the delay time. In such a case, a delay time setting means 4 sets the delay time based on the waveform of the input signal, and an attenuating rate setting means 5 sets the rate to attenuate the delay signal for each signal based on the signal waveform. Based on the rate set by the means 5 for each delay signal, a correcting signal output part 2 attenuated the delay signal and outputs it as the correcting signal. A differential amplification part 3 calculates difference between the input signal and the correcting signal and the waveform is corrected and outputted. Thus, even the input signal in the waveform, which is made asymmetric on right and left sides, can be made optimumly thin while being matched with the waveform.

Description

DETAILED DESCRIPTION OF THE INVENTION (Summary) The present invention relates to a waveform correction device for an input signal, and particularly relates to a delayed signal output section that delays and outputs an input signal based on a delay time, and a delayed signal output section that delays an input signal based on a delay time and outputs the delayed signal. A correction signal output section that attenuates the signal outputted by the output signal and outputs it as a correction signal, and a differential amplifier section that calculates the difference between the input signal and the correction signal, corrects the waveform of the input signal, and outputs the corrected signal. Regarding the input signal waveform correction device equipped with the present invention, a delay time setting means for setting a delay time based on the waveform of the input signal is provided, with the aim of optimally narrowing the waveform of the input signal even when the waveform of the input signal is not symmetrical. , based on the waveform of the input signal. The invention also includes attenuation rate setting means for setting the rate at which the signal outputted by the force signal or delayed signal output section is attenuated for each signal.

[Industrial application field]

The present invention relates to a waveform correction device for an input signal, and in particular, a delayed signal output unit that delays an input signal based on a delay time and outputs it as a delayed signal multiple times, and attenuates these delayed signals and outputs it as a correction signal. The present invention relates to an input signal waveform correction device comprising a correction signal output section that calculates a difference between the input signal and the correction signal, and a differential amplification section that corrects the waveform of the input signal and outputs the corrected signal.

In recent years, recording densities have been increasing in magnetic disk devices and the like, and there is a tendency for bit intervals on disks to become narrower.

For this reason, problems such as a decrease in the resolution of the input signal occur due to a peak shift due to waveform interference and an increase in noise jitter. In magnetic disk drives, equalizer circuits are effective and widely used as input signal waveform correction devices for correcting this.

[Conventional technology]

FIG. 6 shows an example of an equalizer circuit used in a magnetic disk device as a conventional input signal waveform correction device.

In the figure, 11 is a delay circuit that delays the input signal by a delay time based on a constant of this circuit and outputs the delayed signal; 12 is an attenuator that attenuates the input signal based on the equivalent quantity k that is the rate at which the input signal is attenuated; 13 is a differential amplifier that outputs the difference between the signal input to the positive end and the signal input to the negative end. Here, the delay time τ has conventionally generally used a value around half the half-width (time at half the signal level), and in this example, it is set to half the half-width.

In such an input signal waveform correction device, as shown in FIG.
is input to the delay circuit 11, the delay time τ from its output terminal
A delayed signal (FIG. 7 (2)) delayed by the same amount of time is output. In addition, since the terminal of the delay circuit 11 has a high impedance, the input signal is totally reflected there and delayed by the delayed signal (Fig. 7 (2)), that is, the input signal (Fig. 7 (2)) is delayed.
1)) A signal delayed by a delay time of 2τ (Fig. 7 (3)
) is output and proceeds in the opposite direction to the input signal.

Therefore, the signal input to the attenuator 12 (Fig. 7 (4)
) is the input signal (Figure 7 (1)) and its delay time 2τ
This becomes a combined signal obtained by superimposing the delayed signal (Fig. 7 (3)). Then, the attenuator 12 receives a signal (seventh signal).
(3)) is attenuated based on the equalization amount k, and a correction signal ((5) in FIG. 7) is output. Therefore, the differential amplifier 13 receives a delayed signal (FIG. 7 (2)) having the same waveform as the input signal (FIG. 7 (1)) at its positive end, and a correction signal (FIG. 7 (2)) at its negative end. Figure 7 (5)> is input, so the delayed signal (7th
By removing the waveform of the correction signal (Fig. 7 (5)) from the waveform of Fig. 7 (2)), the waveform of the input signal is narrowed and the signal (
Figure 7 (6)) was output. Here, the waveforms of the input signal before and after correction are shown in detail in FIG. In the same figure,
Half width 40 (nsec) and half width 60 (nsec)
The delay time of the delay circuit 11 is set to τ=50 (nsec), while the equalization amount of the attenuator 12 is set to k=0.3 for the waveform of the left-right asymmetric input signal (2) consisting of the following. Then, based on these constants, a correction signal (2), which is a combination of the input signal and the reflected signal, is generated. In the figure, the correction signal ■ is shown inverted. Then, in the differential amplification section 13, the difference between the waveform of the input signal ■ and the waveform of the correction signal ■ is obtained and the output signal ■ is obtained. is getting thinner.

(Problem to be Solved by the Invention) By the way, in conventional magnetic disk devices, etc., the waveform of the reproduced signal is not completely symmetrical, but slightly asymmetrical, due to the design characteristics of the magnetic head. was common.

In such a case, the conventional input signal waveform correction device cannot optimally correct the input signal waveform. As shown in FIGS. 7 and 8, this means that the waveform of the correction signal is the same as the waveform of the input signal, and this input signal is
It is a superimposition of the waveform of the signal reflected by the output terminal of 1 with a delay time of 2τ, and is separated from the center by an equal amount of time, and the rising and falling parts of the correction signal are similar to that of the input signal. This is because the signal is symmetrical based on the rising portion, and the symmetrical waveform of the correction signal is used to correct the asymmetrical waveform of the input signal. In addition, since this correction signal, which is a composite signal of the input signal and the signal reflected from the input signal, was attenuated by a preset equalization amount, the input signal and its reflected signal are This is because it was not possible to individually attenuate based on the waveform.

For this reason, if the waveform of the input signal is not symmetrical, it is not possible to optimally narrow the waveform based on the waveform.
There is a problem in that there is a possibility that the error rate due to peak shift and noise jitter cannot be reduced.

SUMMARY OF THE INVENTION An object of the present invention is to provide an input signal waveform correction device that can optimally narrow the input signal waveform even when the waveform is not symmetrical.

(Means for solving the problems) In the present invention, the means for solving the above problems are as follows:
As shown in FIG. 1, there is a delayed signal output section 1 which delays and outputs an input signal based on a delay time, and a delayed signal output section 1 which attenuates the input signal or the signal outputted by the delayed signal output section 1 and outputs it as a correction signal. In the input signal waveform correction device comprising a correction signal output section 2 and a differential amplification section 3 that calculates the difference between the input signal and the correction signal, corrects the waveform of the input signal, and outputs the corrected signal, the input signal a delay time setting means 4 for setting a delay time based on the waveform of the input signal; and a delay time setting means 4 for setting the delay time based on the waveform of the input signal, and a rate at which the input signal or the signal outputted by the delayed signal output section 1 is attenuated is determined for each signal based on the waveform of the input signal. The reason is that 5 stages of attenuation ratio setting are provided.

(Operation) The operation of the present invention will be explained with reference to FIG. 1. First, the delayed signal output section 1 delays the input signal based on the delay time and outputs the delayed signal. At this time, the delay time setting stage 4 sets the delay time based on the waveform of the input signal. At the same time, the attenuation ratio setting stage 5 attenuates the input signal or the signal output from the delayed signal output section 1 based on the waveform of the input signal, and sets a ratio for each signal. Then, the correction signal output section 2 attenuates the input signal or the signal output by the delayed signal output section 1 based on the above-mentioned ratio set for each delayed signal by the attenuation ratio setting means 5 and outputs it as a correction signal. do. Then, the differential amplifier section 3 calculates the difference between the input signal and the correction signal, corrects the waveform of the input signal, and outputs the corrected signal.

Therefore, even if the input signal has an asymmetrical waveform, the delay time of each delayed signal is set based on the waveform of the input signal, and the attenuation rate of the input signal is set for each delayed signal based on the waveform of the input signal. Since the settings are made for each waveform, the waveform of the input signal can be optimally narrowed to match that waveform.

〔Example〕

Embodiments of the input signal waveform correction device according to the present invention will be described below with reference to the drawings.

FIG. 2 is a diagram showing an example of a magnetic disk device using this embodiment. In the figure, 21 is a head IC circuit (Head IC) that reads data on the disk in the head and outputs a data signal, and 22 is an auto gain control amplifier that keeps the output of the data signal output from the head IC circuit 21 constant. (AGC), 2 3 is an equalizer (Equal
24 is a low-pass filter (L) that removes high frequency noise from the data signal output from the equalizer 23.
PF), 2 5 is a peak detector (Pe
ak Detector), 26 is a pulse shaper that detects the peak value of the data signal passed through the low-pass filter 24 and converts the signal into a pulse.
er). The input signal waveform correction device of this embodiment is used as the equalizer 23, and as described above, this device narrows the peak width of the data signal as the input signal and outputs it. Next, FIG. 3 shows the structure of this embodiment when used in the above magnetic disk device. In the figure, the present embodiment is composed of a differential amplification section 31, a first correction signal generation section 41, and a second correction signal generation section 51.

The differential amplifier section 31 accommodates one positive end and two negative ends,
The difference between the signal input to the positive end and the combined signal of the signals input to each negative end is amplified, and the waveform of the input signal is corrected and output.

The first correction signal generation unit 41 uses the signal output from the auto gain control amplifier 22 as an input signal,
It consists of a delay time setting section 42 that sets a delay time τ1 based on the rising portion of the waveform of this input signal, and a combination of coils and capacitors, and sends the input signal by 1 during the delay time and outputs it as a delayed signal. , the positive end of the differential amplifier section 31 which is this delayed signal, and the second correction signal control section 5
1, an equalization amount setting unit 44 that sets an equalization amount k1 that is a rate at which the magnitude of the input signal is attenuated based on the waveform of the input signal, and this equalization amount k
an attenuator 45 that attenuates the input signal according to the above, outputs it as a correction signal, and inputs it to the negative end of the differential amplifier section 31;
In order to prevent the signal from being reflected at the terminal end of the delay circuit 43, the terminal resistor 46 is provided with an impedance Z0 having the same value as the impedance Z1 of the delay circuit 43.

The second correction signal generator 51 also includes a delay time setting unit 52 that sets the delay time τ2 based on the falling portion of the waveform of the input signal, and a combination of a coil, a capacitor, etc., and the delay circuit 42. A delay circuit 53 outputs the delayed signal outputted by the above-mentioned delay time as a delayed signal delayed by the delay time 2, that is, delayed by the delay time (τ1+τ2) from the above-mentioned input signal, and the delayed signal outputted by the delay circuit 53. an equalization amount setting unit 54 that sets the equalization amount k2 based on the waveform, and sets the equalization amount k2 that is a rate at which the magnitude of the input signal is attenuated based on the waveform of the input signal;
Then, the delayed signal is attenuated according to the equalization amount k2 and output as a correction signal? and a terminating resistor 56 having an impedance Z2 having the same value as the impedance Z2 of the delay circuit 53 so as not to reflect a signal at the terminal end of the delay circuit 53.

Next, the effect of this embodiment will be explained in the fourth section showing the waveform of the signal at each point in time.
This will be explained with reference to the figures.

First, the correction signal generation section 41 receives a left-right asymmetric signal ((1)'' in FIG. 4) as an input signal. The delay time τ1 is determined based on the rising part of the waveform of
Set. Then, the delay circuit 43 uses this delay time τ1
The input signal is delayed according to the delay signal (Fig. 4 (2)
”). Since there is a terminating resistor 46 at the end of the delay circuit 43, no signal reflection occurs.
Enter 1. Further, the equalization amount setting section 44 sets an equalization amount k■, which is a rate at which the magnitude of the input signal is attenuated, based on the waveform of the input signal. Then, the attenuator 45 follows the equalization amount k? The input signal is attenuated and output as a correction signal ((3)' in FIG. 4). This correction signal is input to the negative end of the differential amplifier section 31.

In the second correction signal generating section 51, the delay time setting section 52 first sets the delay time τ2 based on the falling portion of the waveform of the input signal. Then, the delay circuit 53 receives the delay signal outputted from the delay circuit 43 (see FIG. 4).
2)') to the above delay time τ2f': , that is, as a result, the time (τ■ + 2
) and outputs a delayed signal ((4)' in FIG. 4). Since there is a terminating resistor 56 at the end of the delay circuit 53, no signal reflection occurs. This delayed signal is then input to the attenuator 55. At this time, the equalization amount setting section 54 sets an equalization amount k1, which is a rate at which the magnitude of the input signal is attenuated, based on the waveform of the input signal. Therefore, the attenuator 55 attenuates the delayed signal according to the equalization amount k2 and outputs it as a correction signal ((5)' in FIG. 4). This correction signal is input to the negative end of the differential amplifier section 31.

? Then, in the differential amplification section 31, first, the above correction signal (FIG. 4 (3)') inputted to each negative terminal and the above correction signal (4th
Figure (5)'') and the combined signal (Figure 4 (6)')
), and find the difference between this resultant signal, the input signal input to the positive end (Fig. 4 (1)''), and the delayed signal (Fig. 4 (2)'), which has the same waveform. .

In other words, the waveform of the input signal (Fig. 4 (1)') is calculated based on the waveform by the equalization amount ■, τ2 and the delay time kyu, k2.
The combined signal (Fig. 4 (6)
)'), the asymmetrical portion is removed from the waveform of the left-right asymmetrical input signal, and an output signal with a narrower peak width ((7)' in FIG. 4) is obtained.

Here, an example of the waveform of the input signal before and after correction is shown in detail in FIG. In the same figure, the waveform of the input signal
This is similar to the conventional example shown in FIG. 8, which is asymmetrical in left and right directions. First, in FIG. 4A, for this input signal "■", the first correction signal generation section and the second correction signal generation section each delay circuit 43. 53 each delay time is j1 =40 (nsec)?, =3
5 (nsec), and each attenuator 45,
The equalization amount of each of 55 is k. =0.3 and K. = 0.65. As a result, in the differential amplifying section 31, a correction signal ゜, which is a resultant signal as shown in the figure, is generated. Then, the differential amplification section 13 determines the difference between the input signal ■' and the correction signal ■'' and sets it as an output signal ■''. The waveform of the output signal ``■'' clearly has a narrower peak width than the waveform after correction according to the conventional example shown in FIG. 8. Note that the corrected signal ``■'' is shown inverted in the same figure.

In addition, in FIG. 5(b), the waveform of the input signal similar to the above
'', the delay time of each delay circuit 43, 53 in the first correction signal generation section and the second correction signal generation section is ?■ as in the conventional example without changing 2?■ =?2 =50 (n
sec), and the equalization amount k for each attenuator 45, 55.
■, K2 values, respectively, k. =0.3 and K. = 0.5. As a result, the corrected output signal ■
゛゜? The waveform has a narrower peak width than the corrected waveform according to the conventional example shown in FIG. 8, and it is sufficient to change only the equalization amount.

Therefore, according to this embodiment, even if an input signal has an asymmetrical waveform, the equalization amount τ■,
τ2 and delay time k. , k2 are set respectively, and the waveform of the input signal is corrected using the waveform of the correction signal created based on them to narrow the peak width. Therefore, an output signal with a waveform from which the asymmetrical portion has been removed is obtained, resulting in an asymmetrical waveform. It is possible to correct the peak shift due to Furthermore, by narrowing the input signal to match its waveform, the influence of noise jitter and the like can be reduced, and ultimately the error rate when recognizing this input signal can be reduced.

In this embodiment, the waveform of the input signal is asymmetrical, but this also applies to a symmetrical waveform, and in that case, the equalization amount k■
and k2 are set to the same value, and the delay times τ1 and τ2 are
can also be set to the same value. Furthermore, in the present invention, it is not necessarily necessary to change both the equalization amount and the delay time, and it is sufficient to change not only the equalization amount but also the delay time as long as the effect of sufficiently thinning the waveform can be obtained.

(Effects of the Invention) As explained above, according to the present invention, even if the input signal has an asymmetrical waveform, the delay time of the input signal is set based on the waveform of the input signal, and the rate at which the input signal is attenuated is set. is set, a correction signal is output, and the waveform of the input signal is corrected using the waveform of the correction signal to narrow the peak width. Therefore, an output signal with a waveform in which the asymmetrical part has been removed is obtained, and the peak shift due to the asymmetrical waveform is can be corrected. Furthermore, by narrowing the input signal to match its waveform, the influence of noise jitter and the like can be reduced, and ultimately the error rate when recognizing this input signal can be reduced.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle of the present invention, FIG. 2 is a diagram showing an example of a magnetic disk device using the input signal waveform correction device of this embodiment, and FIG. 3 is a diagram showing the configuration of this embodiment. FIG. 4 is a diagram showing the waveform of the signal at each point in time in this embodiment, FIG. 5 is a diagram showing the waveform of the input signal before and after correction by this embodiment, FIG. 6 is a diagram showing the conventional example, and FIG. FIG. 8 is a diagram showing the waveform of a signal at each point in time in the conventional example, and FIG. 8 is a diagram showing the waveform of the input signal before and after correction in the conventional example. 1... Delayed signal output section 2... Correction signal output section 3... Differential amplifier section 4... Delay time setting means 5... Attenuation ratio setting means

Claims (1)

[Claims] A delayed signal output section (1) that delays and outputs an input signal based on a delay time, and an input signal or delayed signal output section (1).
) a correction signal output section (2) that attenuates the signal output by the input signal and outputs it as a correction signal; and a differential amplifier section that calculates the difference between the input signal and the correction signal, corrects the waveform of the input signal, and outputs the corrected signal. (3) An input signal waveform correction device comprising: (4) delay time setting means for setting a delay time based on the waveform of the input signal; and 1. A waveform correction device for an input signal, comprising: an attenuation ratio setting means (5) for setting, for each signal, a ratio at which the signal outputted by the delayed signal output section (1) is attenuated.