KR0144817B1 - Digital playback signal detection device and method - Google Patents

Abstract

The present invention relates to an apparatus and method for detecting a digital reproduction signal, which complements a function of a data detection circuit for compensating for loss and distortion of a reproduction signal. The present invention compensates for the loss of the low frequency band through the integrator of the phase equalizer with the signal reproduced from the predetermined recording medium. The output signal of the phase synchronization unit 10 is delayed into the first and second signals by using two delay elements, and is differentiated after differentially amplifying the second delay signal and the output signal of the phase equalizer. Linearly add and subtract the signal and the first delay signal. In addition, the limiter is connected to the output terminal of the differentiator in the waveform shaping section, and the two limiters are connected to the output terminal of the buffer in the data detector section to remove distortion and noise of the input signal. Therefore, the error rate in data detection can be reduced, and data can be stably detected even if the tape is degraded and the system is unstable.

Description

Digital playback signal detection device and method

1 is a block diagram showing a conventional digital reproduction signal detection apparatus

2 is a detailed block diagram showing a preferred embodiment of the digital reproduction signal detection apparatus according to the present invention.

3a to f are waveform diagrams for explaining the operation of the device of FIG.

4 is a frequency characteristic curve of the device of FIG.

5 is a detailed block diagram showing another embodiment of the digital reproduction signal detection apparatus according to the present invention.

6A to J are waveform diagrams for explaining the operation of the apparatus of FIG.

* Explanation of symbols for main parts of the drawings

20: regeneration amplifier 30: phase equalizer

31: Integrator 35: Phase Compensator

36: amplifier 40, 70: waveform shaping part

41, 71: 3-tap differential equalizer 42, 43, 73, 74: Delay

44,46,75,78: Differential amplifier 45: Differential

47 to 50: buffer 51, 72: low pass filter

60, 80: data detector 77, 82, 83: limiter

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for reproducing a digital signal recorded on a predetermined recording medium. In particular, a data detection circuit for compensating for loss and distortion of a reproduction signal is compensated for to facilitate data restoration and to increase signal to noise ratio. The present invention relates to a digital reproduction signal detection device and a method for stably detecting data even if low.

In general, in a digital magnetic recording and reproducing system for recording and reproducing digital signals such as D-VCR and DAT (Digital Andio Tope Recorder), the analog signals input are recorded as digital signals on a recording medium such as magnetic tape. The reproduced digital signal is restored to a digital signal at the time of recording and then changed back to an analog signal.

However, the reproduction signal has an error rate during data recovery due to the inter-symbol interference due to the characteristics of the rotary transformer and the recording medium located between the magnetic head and the amplifier and the degradation of the S / N ratio. The overall performance of the system had a disadvantage. In order to prevent this disadvantage, conventionally, data was detected after phase correction and amplitude correction were performed on the reproduction signal.

1 is a block diagram showing a conventional digital reproduction signal detection apparatus. The conventional digital reproduction signal detection apparatus of FIG. 1 includes a reproduction amplifier section 11 which amplifies digital data reproduced from a recording medium through a reproduction head into a signal of a predetermined size. A first equalizing unit 12 for correcting the phase of the amplified reproduction signal is connected to the output terminal of the reproduction amplifier unit 11. A second equalizing unit 13 having a structure of a truncation filter is connected to an output terminal of the first equalizing unit 12. More specifically, the second equalizing unit 13 includes two delayers 14 and 15 having taps at intervals T for a predetermined period and an adder 16 for synthesizing the output signals of each tap. It consists of a three-tap equalizer. The variable resistors are connected between the output terminal of each tap and the adder 16.

In Fig. 1, digital data recorded on a predetermined recording medium such as magnetic tape is reproduced through a reproduction head. The reproduction signal is input to the reproduction amplifier 11 and amplified into a signal having a predetermined size. The amplified reproduced signal is input to the first equalizing unit 12 to smoothly correct the out of phase. The phase-corrected reproduction signal is input to the first delay unit 14 of the second equalizing unit 13 and delayed for a predetermined time T and output. The phase-corrected reproduction signal is also output to the adder 16 in which the gain K ₃ is adjusted according to the resistance value of the variable resistor. The first delayed reproduction signal is input to the second delay unit 15 and is delayed by a predetermined time interval T and output. The first delayed regeneration signal is also output to the adder 16 in which the gain K ₂ is adjusted according to the resistance value of the variable resistor. The second delayed regeneration signal is output to the adder 16 by adjusting the gain K ₁ according to the resistance value of the variable resistor. That is, the output signal of each tap changes the gain by adjusting the resistance value of the variable resistor so that it is not affected by the interference between signals. The adder 16 synthesizes an output signal of each tap whose gain is adjusted to improve asymmetry, peak-shift, and amplitude degradation of the reproduced isolated waveform, and then outputs the data to the data detector to detect the original recorded data. Done. However, the above-described conventional detection apparatus only corrects the amplitude correction and the slight asymmetry and the peak-shift or only performs the asymmetry and the slight peak-shift and the amplitude correction but not the ideal equalization in all parts. In order to achieve the ideal equalization, the number of taps of the truncation filter must be increased indefinitely, which makes gain adjustment per tap difficult. In addition, there is a problem that a burden occurs when the automatic equalization algorithm is introduced.

On the other hand, a three-tap cosine equalizer with a differential as a conventional equalizer is disclosed in Japanese Television Society VOL 40, No. 6, 1986 DIFFERENTIATION-BASED WAVEFORM EQ IN HIGH DENSITY DIGITAL MAGNETIC RECORDING. It does not include differential and integral functions. In particular, when the tape deteriorated and the system was unstable and the S / N ratio of the playback signal was very low, accurate data could not be detected.

Accordingly, an object of the present invention is to provide an apparatus and method for detecting a digital reproduction signal which includes an integral and a differentiator in an equalizer to correct the deterioration of a characteristic of a reproduction signal to reduce an error rate when restoring data. In providing.

Another object of the present invention is to limit the undifferentiated signal and the signal before data detection based on a predetermined level when equalizing and detecting the digital reproduction signal, so that the data can be stably detected even at a low S / N ratio. A digital reproduction signal detection device and method thereof are provided.

The digital reproduction signal detecting apparatus of the present invention for achieving the above objects is a digital recording reproduction apparatus for detecting data by equalizing and correcting a signal reproduced from a recording medium, the loss and distortion of the low frequency band of the reproduction signal A phase equalizer for compensating and correcting a phase, and delaying a signal applied from the phase equalizer at a predetermined time interval to generate first and second delay signals, and linearly canceling the phase equalized signal and the second delay signal. Compensating the high frequency component of the added signal by adding the waveform, and converting the waveform to the equalized signal by linearly adding the high frequency compensated signal and the first delay signal, and outputting the phase signal to the output signal and the output signal of the waveform shaping unit. A data detector is provided for detecting the original recorded data using one signal.

In addition, the digital reproduction signal detection method of the present invention for achieving the above object is the equalization method of the digital recording and reproducing apparatus for equalizing and correcting the signal reproduced from the recording medium to detect data, the low frequency band of the reproduction signal Compensating for the loss of the signal, correcting phase misalignment of the region-compensated playback signal, and outputting first and second delay signals by delaying the phase-corrected playback signal at predetermined time intervals. Linearly adding a reproduced signal and a second delayed signal and outputting the same; differentiating the added signal to compensate for a high frequency component of the added signal; and linearly adding the high-pass compensated reproduced signal and the first delayed signal; And adding the equalized signal to output the equalized signal.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram showing an embodiment of a digital reproduction signal detection apparatus according to the present invention. The apparatus of FIG. 2 includes a reproduction amplifier 20 for amplifying a digital data reproduced on a recording medium through a reproduction head into a signal of a predetermined size. The output terminal of the reproduction amplifier 20 is connected to a phase equalizer 30 which performs phase correction by integrating the amplified reproduction signal. The phase equalizer 30 includes an integrator 31 for integrating the amplified reproduction signal and a phase corrector 35 for correcting the phase of the integrated reproduction signal. The waveform shaper 40 connected to the output terminal of the phase equalizer 30 adds the output signal of the phase equalizer 30 and the signal delayed by using N delays to differentiate and differentiate the differential signal and the delayed signal. By linearly adding and filtering the M signals, asymmetry, amplitude degradation, and peak shift of the reproduction signal waveform are corrected. The waveform shaping section 40 includes variable resistors K1 'to K3' for attenuating an input signal, a three-tap equalizer 41, a plurality of buffers 47 to 50 for buffering, and three. A low pass filter 51 for low-passing the playback signal corrected by the tap-differentiator 41. The data detection unit 60 connected to the output terminal of the waveform shaping unit 40 detects the original recording data by using the reproduction correction signal applied from the waveform shaping unit 40 and the reproduction correction signal inverted in phase.

Referring to the configuration of the digital reproduction signal detection apparatus shown in FIG. 2 in more detail, the integrator 31 of the phase equalizer 30 has a resistor R ₁ and a capacitor C at the output terminal of the reproduction amplifier 20. ₁ ) are connected in parallel. The phase corrector 35 amplifies the integrated reproduction signal into a signal of a predetermined magnitude and outputs the in phase and reverse phase signals, respectively, and the coil L and the condenser C ₂ are provided at the in phase output terminals of the amplifier 36. ) Is connected in series, and a variable resistor (VR) is connected to the reverse phase output terminal.

The waveform shaping unit 40 includes two delayers 42 and 43 having taps at predetermined time intervals T by receiving the output signal of the phase equalizing unit 30 through the buffer 47, and having a first delay unit. And a first differential amplifier 44 for amplifying the difference component between the signal inputted to 42 and the output signal of the second delay unit 43. A buffer 48 for buffering an output signal is connected to an output terminal of the first differential amplifier 44, and a differentiator 45 for differentiating a signal applied through the buffer 48 is connected. A buffer 49 is also connected to the output terminal of the first delay unit 42, and is composed of a second differential amplifier 46 that amplifies the difference between the signal applied through the buffer 49 and the differential reproduction signal.

The operation of the digital reproduction signal detection apparatus configured as described above will be described with reference to FIGS. 3 and 4 as follows.

3a to f show the output waveform diagram of the device of FIG. FIG. 3A is a digital data recorded on a predetermined recording medium such as a magnetic tape and a waveform thereof, and FIG. 3B is a waveform diagram of a signal amplified by an amplifier during reproduction. In general, a digital signal reproduced through a magnetic recording medium has a property closer to analog due to the characteristics of the recording medium. That is, as shown in FIG. 3A and FIG. 3B, the amplitude changes rapidly in each inverted portion of the original digital signal. 'A' in FIG. 3c is a waveform diagram in which the level of the DC component is compensated by integrating the amplified reproduction signal, and 'b' is a waveform diagram passing the delay by a predetermined time interval 2T. 3D is a waveform diagram of amplifying the difference components of the 'a' and 'b' waveforms shown in FIG. 3C. FIG. 3E is a waveform diagram obtained by differentiating the waveform of FIG. 3D, and a portion corresponding to each inverted portion of the waveform shown in FIG. 3A is zero-forcing. FIG. 3f is a waveform diagram of amplifying a difference component between the waveform of FIG. 3e and a waveform delayed by a predetermined time interval T. FIG.

In FIG. 2, the waveform of the signal reproduced by the reproduction head from the digital data (waveform shown in FIG. 3A) recorded on a recording medium such as magnetic tape (waveform in FIG. 3B) is due to the nonlinear distortion of the magnetic channel. If the rising and falling curve slopes are double symmetric, and the amplitude amplitude of the peak differs according to the run length, peak-shift is generated due to sign interference. The reproducing signal is amplified by the reproducing amplifier 20 into a signal having a predetermined size (waveform in FIG. 3b). It is integrated according to the time constant value by (R ₁ ) and condenser (C ₁ ). Through the integrator 31, the reproduction signal is compensated for the loss of the low frequency band close to the original signal (the 'a' waveform in FIG. 3C). The amplifier 36 of the phase corrector 35 loses the low frequency band through the integration process. The compensated reproduction signal (the 'a' waveform in FIG. 3C) is input and amplified into a signal having a predetermined size, and output as an amplified signal having the same phase and an inverted phase. The resonant circuit in which the coil L and the capacitor C ₂ are connected in series to the in-phase amplifier stage of the amplifier 36 and the resistance value of the variable resistor VR connected to the inverse amplifier stage correspond to the frequency characteristics of the recording channel. Correct the phase distortion. The reproduction signal whose phase distortion is corrected is input to the 3-tap equalizer 41 through the buffer 47 of the waveform shaping unit 40. That is, the reproduction signal input through the buffer 47 is applied to the first delay unit 42 by adjusting the gain K ₁ according to the resistance value of the variable resistor. The first delay unit 42 delays the input signal by a predetermined time interval T and outputs the delayed signal to the second delay unit 43 and the buffer 49, respectively.

The second delay unit 43 delays the signal applied from the first delay unit 42 by a predetermined time interval T again and outputs the signal to the negative input terminal of the first differential amplifier 44. The gain-adjusted regenerated signal 'K ₁ ', which is output through the output stage drawn between the buffer 47 and the first delay unit 42, has a gain (K ₂ ) adjusted according to the resistance of the variable resistor so that the first differential is adjusted. Output to the positive (+) input terminal of the amplifier (44). The first differential amplifier 44 linearly adds a reproduction signal gain-adjusted by 'K ₁ ''K ₂ ' and a reproduction signal delayed by a predetermined time interval 2T (the 'b' waveform in FIG. 3C) by a buffer 48. (Waveform shown in FIG. 3D) The differentiator 45 in which the capacitor C ₃ and the resistor R ₂ are connected in parallel differentiates the reproduction signal applied through the buffer 48 in accordance with the time constant value to generate a pulse of the reproduction signal. Narrow it down. That is, part of the thereby compensate for the high frequency component (operation 3e degrees waveform) a differential reproduction signal is the gain (K ₃₎ controlled according to the resistance value of the variable resistor a second differential amplifier 46 is attenuated when they are played back (-) Output to the input terminal. The second differential amplifier 46 receives a reproduction signal delayed by a predetermined time interval T applied through the buffer 49 to the positive input terminal and linearly adds the reproduced signal to the buffer 50 (see FIG. 3f). Waveform) The low pass filter 51 low-passes the reproduction signal applied through the buffer 50 to remove high frequency noise generated during the derivative and correction process. The signal output from the low pass filter 51 is applied to the data detector 60.

The buffer 61 outputs an inputted reproduction signal and a signal having the same shape and opposite phase as the input signal to the data detector 62. The data detector 62 amplifies the difference at the reference level of the two input signals so that the rising or falling edge of the data is generated at the point where the two signals are crossed with each other. Outputs signals (+ DATA, -DATA).

4 is a curve representing the frequency characteristics of the apparatus of FIG. 2, and the curve X of FIG. 4 represents the characteristics of the equalizer itself and has a characteristic opposite to that of the channel. Curve Y of FIG. 4 represents gain characteristics of frequencies of reproduction signals in the second apparatus. Curve Z in FIG. 4 shows the reproduction characteristics of EFM (Eight To Fourteen Modulation).

As in the above-described embodiment, when the equalizing device is provided with an integrating means and a differential means to correct the loss of the low and high frequency bands of the reproduction signal due to the magnetic channel characteristics, the asymmetry, amplitude degradation, peak shift, S / N ratio degradation can be corrected.

However, according to the embodiment described above, the signal picked up by the head from the recording medium contains a large amount of noise, and the signal-to-noise ratio becomes worse due to the high frequency emphasis characteristic of the waveform shaping portion. Therefore, since distortion occurs in the reproduction signal waveform corresponding to the rising / falling edge of the original recording data, and the reproduction signal is inclined, time axis error and glitches occur during data detection, and are synchronized with the reproduction clock. There was a problem that a run length error occurred.

In order to prevent this, increasing the level of the playback signal, the distorted portion of the detection point is relatively large, the slope of the playback signal is also urgent to eliminate the anxiety and distortion of the crossing portion when detecting data, Eliminating contact status could reduce data detection error. In fact, when operating the hardware, the level of the reproduction signal should be maximized so that the error occurred within the error correction capability of the system, and there was no problem. However, if the tape deteriorates and the system becomes unstable, the S / N ratio of the playback signal is lowered, so that accurate data cannot be detected in the above-described embodiment.

Therefore, in another embodiment of the present invention, by adding means for limiting the undifferentiated reproduction signal and the reproduction signal before data detection to a predetermined level, the error caused by the unstable contact state of the crossing portion and the loose slope is reduced, and the glitch It can prevent the occurrence and improve the performance of the system.

5 is a detailed block diagram showing another embodiment of the digital reproduction signal detection apparatus according to the present invention. The configuration of the reproduction amplifier 20 for amplifying the signal reproduced by the head in FIG. 5 and the phase equalizer 30 for performing phase correction by integrating the amplified reproduction signal is shown in FIG. Same as the configuration. The waveform shaping unit 70 connected to the output terminal of the phase equalizing unit 30 linearly adds and differentiates an input signal and a signal delayed by using N delay elements and then limits and limits the signal and the delayed signals. By linearly adding and filtering the M pieces, the asymmetry, amplitude degradation, peak shift, and S / N deterioration of the reproduced signal waveform are corrected. The configuration of the waveform shaping section 70 is the same as that of the first embodiment, and only the limiter 77 is additionally connected between the differentiator 76 and the variable resistor K ₃ so that the differential signal is set to a predetermined level. Limiting as a reference removes distortion and noise of the differential signal.

The reproduction correction signal output from the waveform shaping unit 70 is applied to the data detection unit 80. The data detection unit 80 limits the reproduction correction signal and the reproduction correction signal inverted in phase with a predetermined level, and then limits the signal. The original recorded data is detected. The configuration of the data detector 80 is the same as that of the first embodiment, and only two limiters 82 and 83 are additionally connected between the buffer 81 and the data detector 84 to have the same shape and phase. By limiting the two output signals of the opposite buffer 81, respectively, distortion and noise of the two signals are removed.

The operation of the digital reproduction signal detection apparatus configured as described above will be described with reference to the waveform diagram of FIG.

The signal reproduced from the recording medium is amplified by the reproduction amplifier 20 and then applied to the integrator 31 of the phase equalizer 30. At this time, the signal recorded on the recording medium is a digital signal waveform as shown in FIG. 6A, but the amplified reproduction signal is reproduced in the form of FIG. 6B due to distortion, noise, interference, and the like. This signal is integrated in the integrator 31 and then subjected to the phase corrector 35 to correct the phase distortion corresponding to the frequency characteristic of the recording channel, resulting in a signal as shown in FIG. 3C.

The output signal of the phase equalizer 30 is applied to the waveform shaping unit 70 and attenuated by the variable resistors K ₁ ′ (K ₂ ′) and then input to the first differential amplifier 75.

In the 3-tap equalizer 71, the delay times of the two delayers 73 and 74 are fixed to T, and the gain of the non-delayed signal (OT signal) is 1, and the attenuation rate of the variable resistor K3 'is increased. Is set to 1/2, the output signal (6th waveguide) characteristic of this 3-tap differential equalizer 71 is the transfer function H (w) = eEXP (-jwT) * (1 + wK ₃ 'K ₃ 'SINwT). Specifically, the original signal, which has been delayed by 2T, passed through the variable resistors K ₁ ′ (K ₂ ′) is linearly added to the first amplifier 75 to become a signal as shown in FIG. 6d. This signal is applied to the differentiator 76 and differentiated so that the low pass component is removed as shown in FIG. 6E, and the differentiated signal is applied to the first limiter 77. In the first limiter 77, a signal above the upper reference level is a positive signal and a signal below the lower reference level is a negative signal based on the constant level shown in FIG. 6E. The signals between the upper and lower quasi-levels are respectively output as 0 (waveform of FIG. 6f). In this way, the noise included in the A portion of the differential signal (waveform of FIG. 6e) can be removed. The signal output from the first limiter 77 is applied to the second differential amplifier 78 through the variable resistor K ₃ ′ and added to the signal delayed by 1T by the first delay unit 73.

As shown in FIG. 6G, the reproduction signal in which the amplitude correction and the waveform correction are completed, the high pass noise generated by emphasizing the high range is removed and applied to the buffer 81 by passing through the low pass filter 72. The buffer 81 receives the input signal S1 indicated by the solid line in FIG. 6G and the signal S2 indicated by the dotted line having the same phase and opposite phase as the input signal, respectively, in the second and third limiters 82 and 83. Will output The second limiter 82 receives the output signal S1 of the buffer 81 and outputs a signal above the upper reference level as a positive polarity signal (+) and a signal below it as 0 as shown in FIG. 6H. do. The third limiter 83 receives the output signal S2 of the buffer 81 and outputs a signal below the lower reference level as a negative polarity signal (-), and further signals 0 as shown in FIG. 61. do. When the distortion and noise included in the output signals S1 and S2 of the buffer 81 are removed in this manner, the output signals of the two limiters 82 and 83 are applied to the data detector 84. The data detector 84 detects that the rising edge or falling edge of the data is generated at the crossing portion when the two input signals intersect each other with respect to one reference level, thereby accurately recovering the original recorded data form as shown in FIG. 6J. Outputs signals (+ DATA, -DATA).

As described above, in the preferred embodiment of the present invention, a case in which two delayers and one differentiator are used has been described. However, the present invention is not limited thereto, and there are N delayers and M differentiators (M, N Is a natural number, it can be covered up to the case of using M <N), so it will be clear to those skilled in the art that detailed description thereof will be omitted.

As described above, the present invention includes an integrating means and a differential means in the equalizing device to correct the loss of the low and high frequency bands of the reproduction signal due to the magnetic channel characteristics, thereby improving the asymmetry of the reproduction waveform by more than 0.5 times. Amplitude degradation, peak-shift 15% reduction, and S / N ratio degradation can be corrected. In particular, when the eye-pattern is observed, an aperture ratio of 60% or more can be obtained, and thus a very advantageous detection window width can be obtained during data detection, thereby reducing the error rate.

In addition, by limiting the undifferentiated signal and the playback signal before data detection to a certain level, the tape is degraded and the system is unstable, so the data can be stably detected even if the overall S./N ratio is low, thereby improving the overall performance of the system. It can be effective.

Claims (11)

A digital recording and reproducing apparatus for detecting data by equalizing and correcting a signal reproduced from a recording medium, the digital recording and reproducing apparatus comprising: a phase equalizer which compensates and corrects a loss and a distorted phase of a low frequency band of the reproduced signal; And delaying the signal applied from the phase equalizing unit at predetermined time intervals to generate the first and second delayed signals, and linearly adding the phased equalized signal and the second delayed signal to compensate the high frequency component of the added signal. A waveform shaping unit configured to linearly add the high-pass compensated signal and the first delay signal to output the equalized signal; And a data detection unit for detecting an original recording device using an output signal of the waveform shaping unit and a signal in which the output signal is inverted in phase. The apparatus of claim 1, wherein the phase equalizer comprises: an integrator which integrates the reproduction signal; An amplifier for amplifying the integrated reproduction signal into a signal having a predetermined magnitude and outputting each of the in-phase amplified signal and an inverted amplified signal whose phase is inverted; And a coil and a capacitor are connected in series to the common-phase amplifier signal output terminal of the amplifier, and a variable resistor is connected to the reverse-phase amplifier signal output terminal. The digital reproduction signal detection apparatus of claim 1, wherein the waveform shaping unit comprises a differentiator for differentiating the addition signal to compensate for a high frequency component of the addition signal. 4. The digital reproduction signal detection apparatus of claim 3, further comprising a low pass filter for low-passing the signal equalized by the waveform shaping unit. [5] The method of claim 3 or 4, wherein the waveform shaping unit is configured by further connecting a limiter for removing distortion and noise of the differentiated signal by limiting the differentiated addition signal to a predetermined reference level at the output terminal of the differentiator. A digital index reproduction signal detection device. 6. The limiter of claim 5, wherein the limiter receives a differential addition signal and outputs a signal above the upper reference level as a positive signal, a signal below the lower reference level as a negative signal, and a signal between the upper and lower quasi-levels as 0. A digital reproduction signal detection apparatus, characterized in that. The data detection unit of claim 1, wherein the data detection unit includes first and second limiters for limiting the output signal and the phase inversion signal of the waveform shaping unit to a predetermined reference level to remove distortion and noise of the two signals. Digital playback signal detection device. 8. The apparatus of claim 7, wherein the first limiter receives an output signal of the waveform shaping unit and outputs a signal above a reference level as a positive polarity signal and a signal below it as a zero signal. 8. The apparatus of claim 7, wherein the second limiter receives an inverted output signal of the waveform shaping unit and outputs a signal below a reference level as a negative signal and a signal above 0 as a negative signal. An equalization method of a digital recording and reproducing apparatus for equalizing and correcting a signal reproduced from a recording medium to detect data, comprising: compensating for a loss of a low frequency band of the reproduction signal; Correcting a phase shift of the low-pass compensated reproduction signal; Outputting first and second delayed signals by delaying the phase-corrected reproduction signal at predetermined time intervals; Linearly adding and outputting the phase corrected reproduction signal and the second delay signal; Differentiating the added signal to compensate for a high frequency component of the added signal; And linearly adding the high-pass compensated reproduction signal and the first delayed signal to output an equalized signal. 11. The method of claim 10, further comprising the step of low-passing the equalized signal.