JPH02220266A - Peak detection system for analog waveform - Google Patents

Abstract

PURPOSE:To compensate the degradation of resolution of an analog waveform by extracting low and high frequency components from the analog waveform and changing the slice value in accordance with relations between component values to generate a window signal. CONSTITUTION:After waveform shaping in an equalizing circuit 4, an analog waveform RS4 of a read signal is given to extracting circuits 20 and 30 to extract low and high frequency components. A resolution detecting circuit 40 obtains a resolution degradation value RV from the difference between components S3 and S2. A slice level generating circuit 50 uses the value RV to output a slice level value SL, and a window signal generating circuit 10 slices the analog signal RS with the level SL to generate a window signal WS and gives it to a peak position detecting circuit 5. This circuit 5 gives the analog signal waveform to a pulse converting circuit 7 through a differentiating circuit 6, and a peak position signal PS is outputted by the window signal WS. Though the peak crest value is not uniform, the peak of a low crest value is not ignored to accurately detect the peak position because the window signal is generated while crossing a low crest value in this detecting system.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention uses an analog waveform peak detection method and a method for digitizing analog successive signals read out via a head from data stored in a disk storage device. The present invention relates to a method suitable for detecting the peak position of an analog waveform.

[Conventional technology]

In fixed disk devices, floppy disk devices, etc., digital data is of course stored on the disk, but what is actually written to the disk is not the digital value itself, but a method suitable for recording it in an alternating pattern of N and S. This is a code based on a predetermined modulation method. This actual writing pattern differs depending on the modulation method, but in any case, the change in pattern from N to S or from S to N has a meaning on the code.

The signal read out from this stored data by the head has an analog waveform, of course, but it has a maximum or minimum peak at the position corresponding to the change in the pattern described above.
By correctly detecting this peak position and creating a signal in which b and t are interchanged at that position, it is possible to reproduce the digital signal in which data was written from the successive analog signal. However, the continuous signals include noise inherent to the disk recording medium and crosstalk between heads.

Noise is often mixed in due to factors such as unerased data from the previous write, and if you are fooled by false peaks based on this noise and detect it incorrectly, a digital signal that is different from the original write may be created. Therefore, reading errors will occur.

For this reason, various efforts have been made in the past to shape the analog waveform of successive signals to remove the influence of noise as much as possible and to accurately detect only the true peaks. Below, the 6th
An overview of such a conventional peak detection method will be explained with reference to the drawings.

In FIG. 6, an analog successive signal R5I from the head l shown on the left side is usually applied to the preamplifier 2 in the form of a differential signal, and its amplified output is applied to the AGC circuit 3. This AGC circuit 3 originally plays the role of aligning the peak values of successive signals that differ between the outer diameter side and the inner diameter side of the disk, but normally the frequency characteristics of the gain can be set by the time constant τ, and this By appropriately selecting the time constant τ, the original successive signal component, which normally has a different frequency from the mixed noise component, is selectively amplified, and the successive signal 1? is shaped so that the noise component is relatively reduced. S3
can be made.

Furthermore, as shown in the figure, this successive signal R53 is transferred to the equalization circuit 4.
The waveform can be shaped by As this equalization circuit 4, for example, a cosine equalization circuit as shown in FIG. 5 is known. As shown in the figure, the successive signal R33 is received through a common resistor 4d and applied to two inputs of a differential amplifier 4a through a delay element 4b and a variable resistor 4c, respectively, and the output is shaped. The transfer function is expressed using a frequency cosine function, and the gain determined by the ratio of the resistors 4c and 4d and the delay time of the delay element 4b are appropriately set. This makes it possible to shape the peak in an analog waveform into a sharp waveform by reducing its base. In FIG. 5, only the cosine equalization circuit for one differential signal is shown for convenience.

After such waveform shaping, in principle, for example, the successive signal R54 is differentiated by the differentiating circuit 6 shown in the figure, the peak position is detected from the zero-crossing point of the differentiated signal by the pulsing circuit 7, and the signal is converted into a digital peak position signal PS. However, in order to remove false peaks as much as possible, a window signal generation circuit 8 is further provided and this generates window signal -3.
Measures are taken to cause the pulsing circuit 7 to detect peaks only within the time range permitted by 8.

This window signal generation circuit 8 slices the successive signal R34 at an appropriate slice level value to form a window signal WS, and uses this window signal -S as a so-called window frame to pulse only the peaks within it. 8, the peaks having a peak value lower than the slice level based on noise in the analog waveform of the successive signal are ignored, and only the original peaks having a higher peak value are detected. However, since the original peak wave height value based on the written data is likely to fluctuate depending on factors such as the flying height of the head from the disk surface, various measures have been taken to determine the upper slice level.

For example, JP-A-51-51918 and JP-A-51-5
The conventional technology described in Publication No. 6165 does not fix the slice level, but instead uses a floating slice level that reflects the actual peak values of successive signal peaks, thereby reducing sudden low peak values due to noise. peaks are selectively ignored.

Even with the conventional method described above, unless the data recording density is particularly high, the write signal of the original waveform when the data is written to the disk is converted from the continuous data signal with a complex waveform including noise to the peak position signal PS. can be played correctly.

(Invention tries to solve!!11141) However,
As the recording density of data on the disk surface increases in order to increase the storage capacity of the disk storage device, the quality of the analog waveform of successive signals deteriorates considerably, so conventional methods cannot sufficiently prevent the occurrence of errors. It's starting to disappear.

For example, if you increase the recording density so that a 3.5-inch fixed disk device has a capacity of several hundred megabytes, even if you use a high-quality storage medium for the disk, it will correspond to the position where the writing pattern switches between N and S. The wave height values of the original peaks in the successive signals become irregular. In other words, the fidelity of the analog waveform of successive signals with respect to the writing pattern on the disk decreases, and from the side that processes the analog waveform, this means that the resolution of each peak in the writing pattern decreases. It will come. Since the analog waveform with such reduced resolution has many peaks with considerably low peak values, it becomes very difficult to distinguish between such original peaks and peaks due to noise. For this reason, in conventional peak detection methods, when false peaks caused by noise are removed, the original peaks are also ignored.

Regarding the cosine equalization method for waveform shaping, it is difficult in practice to match the delay time well with the gain to obtain a high shaping effect, and it is difficult to set the equalization amount fixedly. If it is left as is, it is difficult to provide high waveform shaping performance to irregular peaks in an analog waveform with reduced resolution as described above.

SUMMARY OF THE INVENTION An object of the present invention is to overcome such difficulties and to obtain a peak detection method capable of compensating for the reduction in analog waveform resolution.

[Means to solve the problem]

According to the present invention, this purpose is to first extract two frequency components contained in an analog waveform, and then slice the analog waveform using a slice level signal whose value changes depending on the magnitude relationship of the image component values to obtain a window signal. This is achieved by creating a window signal and detecting the peak position from the analog waveform within the time range allowed by this window signal.

In addition, a resolution reduction value indicating the degree of reduction in resolution of the analog waveform is created from the magnitude relationship between the above two component values, and the analog waveform is shaped using the waveform equalization method with an equal north wall according to this resolution reduction value. Alternatively, it is advantageous to shape the analog waveform in advance by controlling the time constant of the AGC circuit accordingly, and to detect the peak from the shaped waveform.

(Function) According to the present invention, unevenness in peak height values in an analog waveform with reduced resolution tends to occur when at least two frequency components are originally mixed in the waveform. By extracting these two frequency components (for example, a low frequency component and a high frequency component) from an analog waveform and comparing the magnitudes of these component values, it is possible to accurately determine whether and to what extent the peak wave height values are uneven. The slice level value is changed according to the magnitude relationship of these image frequency component values, and the analog waveform is sliced by this slice level value to generate a window signal according to the degree of unevenness of the peak wave height value. By rationally creating this, it is possible to prevent an original peak with a low peak value from being ignored during peak detection.

For example, in a disk storage device that uses the so-called MFM modulation method, N and S patterns on the disk are written in a combination of two widths, and the analog waveform of the subsequent signal has, for example, 1.25 MHz and 2.25 MHz. When the waveforms of two fundamental frequency components of 50 MHz are mixed and the resolution is reduced, the peak value of the waveform of the higher frequency component is usually higher than the peak value of the waveform of the lower frequency component. low.

Therefore, if the resolution reduction value is the value obtained by subtracting the component value obtained by extracting the high frequency component from the component value obtained by extracting the low frequency component from the analog waveform, then this value is the degree of unevenness of the peak wave height value. You can know from. Therefore, when this resolution reduction value is large, the slice level value is lowered to ensure that the peaks with low wave height values are sliced at this slice level to create a window signal, so that the peaks with low wave height values are not ignored. Can be done.

The resolution reduction value created as above can also be used to control waveform shaping by a cosine equalization circuit or an AGC circuit. When this resolution reduction value is large, the base of each peak is wide and the peak value of the high frequency component waveform is particularly reduced due to waveform interference with the adjacent peak. The analog waveform can be shaped to compensate for the drop in resolution by strengthening the signal and narrowing the width of the peak base, or by lowering the time constant of the AGC circuit and shifting the frequency characteristics of its amplification toward higher frequencies. Therefore, the accuracy of peak detection can be further improved.

〔Example〕

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 shows an embodiment in which the analog waveform peak detection method according to the present invention is applied to a disk storage device, and the heads 1. Preamplifier 2. AGC
The peak detection circuit 5 consisting of the circuit 31, equalization circuit 4, differentiation circuit 6, and pulse generation circuit 7 is the same as that shown in FIG. 6, so a description thereof will be omitted.

The analog waveform R54 of the successive signal waveform-shaped by the equalization circuit 4 is sent to the low frequency component extraction circuit 20 and the high frequency component extraction circuit 3.
For example, 1.25 MHz and 2.50 MHz mixed in the analog waveform R5d.
The zero resolution detection circuit 40, which extracts the frequency components and generates component values S2 and 53 representing their magnitudes, inputs these component values S2 and 53 and outputs a resolution reduction value RV.

FIG. 3 shows these extraction circuits 20 and 30 and the synthesis means 4.
The zero extraction circuits 20 and 30, which are specific examples of the zero extraction circuits, have the same circuit configuration except for the frequency components that they extract. To explain the low frequency extraction circuit 20, the capacitor 21 and the reactor 22 function as a bypass filter.
The capacitor 23 and the resistor 24 each form a low-pass filter, and the overall frequency is 1.25 MHz, for example.
In this example, one bandpass filter for z is configured to receive the analog waveform R34 of the differential signal, extract a specific frequency component therein, and provide it to the rectifier circuit 25. The rectifier circuit 25 is, for example, a full-wave rectifier circuit using an operational amplifier or the like, and its rectified output is peak-held by an integrating circuit consisting of resistors 26 and 27 and a capacitor 28 provided on the output side, and is extracted as a component value S2. It will be done.

The corresponding part of the high frequency extraction circuit 30 has 30
For example, 2.50 is extracted from the analog waveform R54 by the bandpass filter.
A component value S3 for the MHz frequency component is then extracted.

The resolution detection circuit 40 in this example uses these blue component values S2
and S3 to obtain the resolution reduction value RV. For example, as shown in the figure, it can be configured with a normal difference circuit including a differential amplifier 41, a pair of input resistors 42, and resistors 43 and 44. .

Returning to FIG. 1, a window signal generation circuit IO is provided to provide a window signal -5 to the peak position detection circuit 5. Is this analog signal 1? For example, it is composed of a simple comparator circuit that slices s at slice level SL to generate window signal -5, but in the method of the present invention, the resolution reduction value R'V is used to determine the slice level SL to be applied to this comparator circuit. For this purpose, a slice level generation circuit 50 is provided, which receives the slice level reference value SLO and the resolution reduction value RV as shown in FIG.
It outputs a slice level value SL corresponding to the SL, and is most simply constituted by a simple differential amplifier 51 as shown in the figure. FIG. 2 shows how the slice level SL is controlled in accordance with this resolution reduction value, and shows waveform examples of the window signal -3 and the peak position signal ps.

The analog waveform PS4 shown in FIG. 2(a) indicates a time when there is almost no deterioration in resolution. For example, the analog waveform PSJ on the left side of FIG. There is a long peak in the wavelength corresponding to the waveform of the middle and low frequency components.

On the right side, peaks with short wavelengths corresponding to the waveforms of high frequency components are shown. In this case, the peak values of the low frequency peak and the high frequency peak are almost the same, and when the resolution reduction value RV is small, the slice level For example, the above-mentioned reference value SLO is used. As the head position moves toward the inner diameter of the disk, the data recording density gradually increases and the resolution of the analog waveform 2S4 tends to decrease, and when the head moves to the middle of the disk or the innermost position, it becomes as shown in (b) in the same figure. As shown in (C), the peak value of the high frequency peak becomes lower than that of the low frequency peak, and the resolution decreases, but in this case, in the method of the present invention, the slice level SL
In order to reliably slice even low-frequency peaks, the reference value SLO is sequentially lowered as shown in the figure in accordance with the resolution reduction value RV.

The window signal generation circuit 10 converts the peak in the analog waveform PSJ into a slice level S as shown in FIGS. 2(a) to 2(C).
In this example, the window signal Tl is sliced on both the positive and negative sides by L.
4S, and this window signal -5 corresponding to the case of (C) in the same figure is shown in (B) of the same figure. The peak position detection circuit 5 detects the peak position in the analog signal PSA only within the time range permitted by the window signal WS, as in the conventional case, and detects the peak position in the analog signal PSA, which is output from the peak position signal P.
S is shown in the same figure (e).

As can be seen from the above, in the method of the present invention, the slice level value SL for creating a window signal is controlled in accordance with the decrease in the resolution of the analog waveform, so that the original peak corresponding to the written data has a low peak value. Even if there is a problem, its peak position is reliably detected without being ignored. Also,
Even if a false peak due to noise or the like is mixed into the analog waveform, it is masked by the window signal, as in the past.

The above-mentioned resolution reduction value RV can also be used in the above-mentioned short AGC circuit 3 and equalization circuit 4 to further enhance their effects.

The time constant control circuit 60 sets the time constant τ given to the AGC circuit 3 according to the resolution n reduction value RV, and compensates for the reduction in resolution by controlling the frequency characteristics of the amplification factor. For example, when the resolution reduction value RV increases, the AGC circuit 3
A that serves to improve the resolution by increasing the response speed or shifting the amplification characteristics toward the high frequency side, raising the peak value of the high frequency peak relative to the low frequency peak.
Since the time constant τ given to the GC circuit is usually set by a CR time constant circuit, the time constant control circuit 60 can be configured, for example, to switch the resistance of this time constant circuit in accordance with the resolution reduction value RV.

When the equalization circuit 4 is, for example, the cosine equalization circuit shown in FIG. This is for controlling the equalization amount gs in accordance with the resolution reduction value RV to optimize or enhance the waveform shaping effect of the cosine equalization circuit, and is constituted by, for example, a simple microprocessor.

When the resolution of the analog waveform is low as shown in Figure 2 (C), the bases of adjacent peaks interfere with each other, resulting in a drop in the peak value of the high frequency peak in particular.
When the resolution reduction value RV is large, the reduction in resolution can be compensated for by strengthening the waveform shaping effect of narrowing the base of the peak by the cosine equalization circuit. Since the waveform shaping effect of this cosine equalization circuit depends on the frequency of the peak, it is advantageous in this case to control the equalization amount so as to focus on improving the waveform of the high frequency peak, for example.

However, the delay time and gain, which are equalization amounts, are interrelated, and if they are not matched properly, there is a risk of generating pseudo-noise, so when the equalization amount is set to the limit where this noise does not occur, Since the waveform shaping effect is maximized, the equalization amount to be set is a fairly complex function of the resolution reduction value RV. For this reason, it is actually desirable to find this equalization amount through experiments and store it in advance in the microprocessor as the equalization amount control circuit 70 in the form of a table for the resolution reduction value RV.

〔Effect of the invention〕

As can be seen from the above explanation, in the present invention, we focus on the fact that the reduction in resolution of analog waveforms is due to the fact that waveforms of at least two frequency components coexist within the analog waveform. Extract the components, create a window signal by slicing the analog waveform using a slice level whose value changes according to the magnitude relationship of the image component values, and detect the peak position from the analog waveform within the time range allowed by this window signal. This makes it possible to rationally control the slice level according to the degree of deterioration in resolution of the analog waveform.

Therefore, in the peak detection method according to the present invention, even if the resolution of the analog waveform is poor and the peak values of the peaks included in it are uneven, and a peak corresponding to the written data has a considerably low peak value, the slice Since the level is reliably crossed thereto to create a window signal, the peak position of the low wave height value can be detected accurately without ignoring the peak.

In an analog waveform read by a head from a high-density recorded disk, the wave height value of the normal peak is 50 to 100%.
Conventionally, the precision of head position control, etc. had to be extremely strict, and even then reading errors could not be completely avoided, but with the method of the present invention, it is possible to write under optimal conditions. Since the peak detection signal that reproduces the data can be extracted, it is possible to operate a high-density disk storage device with a large time margin and head position margin, and with improved resistance to modulation, greatly improving its practicality. It becomes possible to increase the storage capacity and storage capacity.

Furthermore, if you use the waveform shaping effect while controlling the AGC circuit and equalization circuit according to the resolution of the analog waveform,
The above effects can be further enhanced. Regarding cosine equalization circuits, conventionally there was a practical problem in which it was difficult to optimize the fixed equalization amount, but with the present invention, by controlling the equalization amount according to the resolution of the analog waveform, By solving this difficulty, the practicality can be significantly improved.

[Brief explanation of the drawing]

1 to 5 relate to the present invention; FIG. 1 is a circuit diagram illustrating a write data reproducing circuit of a disk storage device implementing the analog waveform peak detection method according to the present invention, and FIG. 2 is its operation. 3 is a circuit diagram of a specific configuration example of the low frequency component extraction circuit, high frequency component extraction circuit, and resolution detection circuit in FIG. 1, and FIG. 4 is the configuration of the slice level generation circuit. A circuit diagram showing an example, FIG. 5 is a configuration circuit diagram of a cosine equalization circuit. FIG. 6 is a circuit diagram of a write data reproducing circuit of a conventional disk storage device corresponding to FIG. 1. In FIG. , 4a: differential amplifier, 4b two delay elements, 4c, 4d
: Resistor, 5: Peak detection circuit, 6: Differentiator circuit, 7: Pulsing circuit, 10: Conventional window signal generation circuit, 20: Low frequency extraction circuit, 21.23: Capacitor, 22: Reactor, 24: Resistor , 25: Rectifier circuit, 26.27: Resistor,
28: Capacitor, 30: High frequency extraction circuit, 31.3
2: Capacitor, 32: Reactor, 34: Resistor, 3
5: Rectifier circuit, 36.37: Resistor, 38: Capacitor, 40: Resolution detection circuit, 41: Differential amplifier, 42~
44°: resistance, 50 slice level generation circuit, 51;
Differential amplifier, 60: Time constant control circuit, 70: Equalization amount control circuit, Ij1 equalization amount, PS: Peak position signal, 1151
NRsa + analog signal or successive signal, RV + resolution reduction value, SL slice level value, St, O + slice level reference value, S2: component value of low frequency component, 53
=component value of high frequency component, time constant set to τjAGc circuit, ■: power supply voltage, Ill window signal.

Claims (1)

[Claims] This method detects the peak position in an analog waveform in which two frequency component waveforms coexist.Each frequency component is extracted from the analog waveform, a component value signal indicating its magnitude is created, and the difference between the two component values is detected. Create a slice level signal whose value changes according to the magnitude relationship between An analog waveform peak detection method characterized by: