JPH0520614A - Waveform equalizer - Google Patents

Abstract

PURPOSE:To enable a good reproducing to be carried out by automatically adjusting a waveform equalization factor in accordance with the degree of frequency degradation by the interference between codes of a regenerating signal. CONSTITUTION:The regenerating signal is synthesized with a reflected signal from an open terminal (b) in the matching terminal (a) of a delay element 1, and the sum signal is performed k-times by an attenuator 2 and sent to a differential amplifier 3. The regenerating signal, as well is inputted to the amplifier 3 through the element 1, and a waveform equalized signal corrected to an original input signal is obtained as this output. Then, when a difference between the peak value and the bottom value of a preamble signal is large relatively and the frequency degradation in a high band is small relatively, a control signal so as to reduce an attenuation factor (k) is outputted from a signal converting circuit 9 to the attenuator 2. When an opposite occasion, the control signal to increase the attenuation factor (k) is outputted. Thus, the attenuation factor (k) is varied automatically in accordance with the degree of the frequency degradation of the regenerating signal, and the waveform equalization factor is adjusted to the optimum value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention corrects the signal waveform of a reproduction signal read from an information recording medium such as a magnetic disk or an optical disk by a magnetic head, an optical pickup or the like to equivalently improve the recording / reproducing characteristics. The present invention relates to a waveform equalizing device for.

[0002]

2. Description of the Related Art FIG. 6 is a circuit diagram showing a conventional waveform equalizer. In the figure, reference numeral 15 is a matching resistor, 16 is a delay element that delays a signal by a certain time τ, 17 is an attenuator for adjusting the waveform equalization rate, and 18 is a differential amplifier. To the input terminal of the matching resistor 15, for example, a reproduction signal obtained by amplifying a signal read from the optical disk is input as a head amplifier output. Here, if the input signal waveform is represented by a time function of f (t + τ) (τ is the delay amount of the delay element),
At the matching end a of the delay element, a sum signal of the input signal f (t + τ) and the reflected signal f (t−τ) from the open end b is obtained.
This sum signal is expressed by the following equation.

F (t + τ) + f (t-τ) (1) This sum signal passes through an attenuator 17, where it is multiplied by K and input to one terminal of a differential amplifier 18. K is an attenuator 17
Is the decay rate of. The signal f (t) via the delay element 16 is input to the other terminal of the differential amplifier 18.
Therefore, at the output of the differential amplifier 18, a corrected signal with respect to the original input signal f (t + τ) is f (t) -K / 2 {f (t + τ) + f (t-τ)} (2) can get. Here, when f (t) = Asimωt, this transfer function H (ω) is generally a cosine function of H (ω) ∝1-2Kcosωτ (3). Therefore, by adjusting the attenuation factor K of the attenuator 17, it is possible to obtain an output signal that is optimally waveform equalized with respect to the input signal. FIG. 7 is a diagram showing the relationship between the frequency of the waveform equalizer and the waveform equalization rate, which is the equalization characteristic when the attenuation rate K = 0.5.

[0004]

However, the above-described conventional waveform equalizer has the following problems. (1) Since the amount of waveform equalization is initially determined by adjusting the attenuation factor K, if the surrounding conditions change such as when the disk changes or the characteristics of the reproducing head vary, the optimum amount of waveform equalization is set. Can't keep it. (2) In the system in which the disc is rotated at a constant speed, the pit length to be recorded differs depending on the information recording position in the disc radial direction, and the inner region of the disc is deteriorated in frequency in the high frequency range due to waveform interference as compared with the outer region. However, since the waveform equalization amount is initially determined as described above, it is difficult to optimally set the waveform equalization amount according to the recording position of the disc.

The present invention has been made to solve such a problem, and its purpose is to automatically adjust a waveform equalization amount to an optimum value in accordance with a change in ambient conditions and a recording position of information,
It is an object of the present invention to provide a waveform equalizer capable of always performing good reproduction.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is, in an apparatus for waveform equalizing a reproduced signal read from an information recording medium according to a predetermined waveform equalization rate, a degree of frequency deterioration of the reproduced signal due to intersymbol interference. Is provided, and means for adjusting the waveform equalization rate according to the detection result of the detection means are provided.

In an apparatus for waveform equalizing a reproduction signal read from an information recording medium according to a predetermined waveform equalization ratio, means for detecting address information of the information recording medium, and the means for detecting the address information of the information recording medium, Means for adjusting the waveform equalization rate according to the recording position of the recording medium is provided.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the waveform equalizer of the present invention. In FIG. 1, reference numeral 1 is a delay element for delaying a head amplifier output read from an information recording medium (not shown) for a predetermined time, and 2 is an attenuator configured to change an attenuation rate according to a control signal. A magneto-optical disk is used as the information recording medium, and the head amplifier output is a reproduction signal read from this disk by a reproduction head (not shown). The output of the delay element 1 and the output of the attenuator 2 are output to the differential amplifier 3, where a differential waveform equalized output signal is generated by correcting the original input signal. Further, 4 is a switch circuit whose opening and closing is controlled by a gate signal which will be described later, 5 is a peak detection circuit for detecting the peak value of the output signal of the differential amplifier 3, and 6
Is a bottom detection circuit for detecting the bottom value. The output signals of the peak detection circuit 5 and the bottom detection circuit 6 are respectively output to the arithmetic circuit 7, and the difference between both outputs is calculated. The difference signal obtained here is a signal representing the degree of intersymbol interference of the reproduced signal waveform. Reference numeral 8 is a comparison circuit that compares the difference signal with a preset reference voltage V _ref and outputs a comparison signal according to the comparison result. Reference numeral 9 is an attenuation factor of the attenuator 2 based on the comparison signal. It is a signal conversion circuit for converting into a control signal to be changed according to the degree.

FIG. 2 is a diagram showing the format of a magneto-optical disk used as an information recording medium in this embodiment.
Each sector has a data area 12 and a preformat area 13
Each pre-formatted area 13 is prerecorded with various information for each sector. The data area 12 is an area in which information can be freely recorded, erased, and reproduced. The pre-format area 13 is, as shown in an enlarged view in the figure, a sector mark SM indicating the beginning of a sector, a preamble area in which a preamble signal serving as a reference signal for synchronization detection is recorded, a sector address, and error detection. The signal is recorded by a CRC or the like. Here, in general, in ISO standard format, etc.,
Since a preamble signal is recorded in the preamble area as a continuous signal having a minimum inversion interval (maximum repetition frequency) of about 10 bytes, the reproduced signal in the preamble area is most likely to be deteriorated in the high frequency characteristic caused by intersymbol interference. growing. Therefore, in this embodiment, as shown in FIG. 2, the gate signal input to the switch circuit 4 is turned on in the preamble region, and at this time, deterioration of the frequency characteristic due to intersymbol interference is detected and the deterioration is corrected. Is.

Next, the operation of this embodiment will be described. FIG. 3 is a waveform diagram showing a reproduction signal of the pre-formatted area 13 shown in FIG. The reproduced signal has a sector mark SM at the beginning, followed by a preamble and an address signal. It can be seen that the reproduced signal in the preamble area has the most deteriorated frequency characteristics due to intersymbol interference as described above, and the amplitude level is attenuated more than other signals. The above reproduced signal is input to the matching end a of the delay element 1 as the head amplifier output. At the matching end a, the reflected signal from the open end b is added, and this sum signal is multiplied by K in the attenuator 2 and input to the differential input terminal (− terminal) of the differential amplifier 3. Further, since the head amplifier output is input to the in-phase input terminal (+ terminal) of the differential amplifier 3 via the delay element 1, the output of the differential amplifier 3 has a waveform corrected with respect to the original input signal. An equalized signal is obtained.

On the other hand, as described above, the gate signal is input to the switch circuit 4 when reproducing the preamble area.
Therefore, when the reproduction of the preamble area is started, the switch circuit 4 is turned on, and the reproduced preamble signal is input to the peak detection circuit 5 and the bottom detection circuit 6. The peak detection circuit 5 and the bottom detection circuit 6 detect the peak value and the bottom value of the preamble signal shown in FIG. 3, and the obtained detection values are output to the arithmetic circuit 7, respectively. The calculation circuit 7 calculates the difference between the peak value and the bottom value, and the calculation result is output to the comparison circuit 8. The comparison circuit 8 compares the output of the arithmetic circuit 7 with the reference voltage V _ref and outputs a comparison signal corresponding to the difference to the signal conversion circuit 9. Then, the signal conversion circuit 9 generates a control signal according to the comparison signal of the comparison circuit 8 and outputs it to the attenuator 2. In this case, when the difference between the peak value and the bottom value of the preamble signal is relatively large and the frequency deterioration in the high frequency band is relatively small, waveform equalization that further emphasizes the high frequency band is not necessary. A control signal for reducing the attenuation rate K is output from 9 to the attenuator 2. On the contrary, when the difference between the peak value and the bottom value is relatively small and the frequency deterioration in the high frequency range is relatively large,
A control signal for increasing the attenuation rate K is output to perform waveform equalization that emphasizes high frequencies.

As described above, the attenuation factor K of the attenuator 2 is automatically changed according to the degree of frequency deterioration of the reproduced signal,
The waveform equalization rate is adjusted to the optimum value by changing the attenuation rate K as shown in FIG. Although the waveform equalization rate is shown in FIG. 4 with the attenuation rate K of the attenuator 2 as a parameter, it can be seen that the waveform equalization rate can be optimally adjusted by changing the attenuation rate K as is clear from the figure. In this way, the attenuation rate K adjusted using the reproduction signal in the preamble area is fixed as the attenuation rate of the sector, and thereafter, waveform equalization is performed with the same attenuation rate. Therefore, the reproduction of the data area is performed at the waveform equalization rate adjusted to the optimum value as described above, so that stable and good data reproduction can be performed. In this case, if the optimum reproduction frequency characteristic is obtained in advance and the reference voltage V _ref is set so as to have that characteristic, the waveform or the like is obtained so as to obtain the optimum frequency characteristic according to the difference between the peak value and the bottom value. The conversion rate can be adjusted. When the reproduction of the preamble area is completed, the gate signal is turned off, and the waveform equalization is performed at the waveform equalization ratio fixed to the optimum value as described above. Then, in the preamble area of the next sector, the gate signal is turned on again, and the attenuation factor of the attenuator 2 is adjusted as described above.

FIG. 5 is a block diagram showing another embodiment of the present invention. This embodiment is applied to a CAV type device in which a disk rotates at a constant rotation speed. In the figure, reference numeral 10 is an address detection circuit for detecting address data from a preformat reproduction signal from a magneto-optical disk which is a recording medium. The address detection circuit 10 adjusts the attenuation rate K of the attenuator 2 based on the detected address data, and sets the waveform equalization rate according to the address. That is, when the address to be reproduced is on the inner circumference side of the disc, the address detection circuit 10 adjusts the attenuation rate K to a large value, and conversely, when the address is on the outer circumference side of the disk, the attenuation rate K is decreased. adjust. This adjusted attenuation rate is fixed until the detection of the next address data. Due to the above, the CA rotating at a constant rotation speed
When reproducing data on a V disc, the frequency deterioration in the high frequency range due to intersymbol interference is generally greater on the inner circumference side of the disc. Therefore, by increasing the attenuation rate K on the inner circumference side of the disc as described above, the frequency The waveform equalization rate can be optimally set according to the deterioration.

[0014]

As described above, according to the present invention, the recording medium is changed or the information recording / reproducing is performed by automatically adjusting the waveform equalization rate according to the degree of frequency deterioration due to intersymbol interference of the reproduced signal. When the ambient conditions such as variations in the characteristics of the working head change, the waveform equalization ratio can be adjusted to the optimum value according to them. Therefore, especially when a removable recording medium such as a magneto-optical disk is used, it is easy to guarantee the compatibility between the recording medium and the device, and the practical effect is great. Also, by adjusting the waveform equalization rate according to the address data, good reproduction can be performed regardless of the reproduction position of the recording medium.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a waveform equalizer of the present invention.

FIG. 2 is an explanatory diagram showing a format of a magneto-optical disk used in the embodiment of FIG.

FIG. 3 is a waveform diagram showing a reproduced signal in a preformatted area.

FIG. 4 is a characteristic diagram showing the waveform equalization rate with the attenuation rate K of the attenuator 2 as a parameter in the waveform equalizer of the embodiment of FIG.

FIG. 5 is a block diagram showing another embodiment of the present invention.

FIG. 6 is a circuit diagram showing a conventional waveform equalizer.

FIG. 7 is a characteristic diagram showing waveform equalization characteristics of the conventional device.

[Explanation of symbols]

1 delay element 2 attenuator 3 differential amplifier 4 switch circuit 5 Peak detection circuit 6 Bottom detection circuit 7 arithmetic circuit 8 Comparison circuit 9 Signal conversion circuit 10 Address detection circuit

Claims (4)

[Claims] 1. An apparatus for waveform equalizing a reproduction signal read from an information recording medium according to a predetermined waveform equalization ratio,
A waveform equalization apparatus comprising: a unit for detecting a degree of frequency deterioration of a reproduced signal due to intersymbol interference; and a unit for adjusting the waveform equalization rate according to a detection result of the detecting unit. 2. The detecting means detects the peak value and the bottom value of the reproduced signal, calculates the difference between the peak value and the bottom value, and calculates the obtained calculation result as a signal indicating the degree of frequency deterioration. The waveform equalizer according to claim 1, characterized in that it comprises means for outputting as. 3. The detecting means is activated during reproduction of a predetermined recording area of the information recording medium, and the waveform equalization rate is adjusted by the degree of frequency deterioration of a reproduction signal of the predetermined recording area. The waveform equalizer according to claim 1. 4. An apparatus for waveform equalizing a reproduction signal read from an information recording medium according to a predetermined waveform equalization rate,
A waveform equalizing device comprising means for detecting address information of the information recording medium, and means for adjusting the waveform equalization rate according to the recording position of the recording medium based on the obtained address information. .