JP2004296079A - Waveform equalizer and recorded information reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waveform equalizer in which high frequency emphasis is applied to reading signals without increasing intercoding interference even though a shortest run length of the reading signals is equal to or less than twice the clock period in channel clock signals. <P>SOLUTION: Sampling is conducted for the read signals from a recording medium in accordance with the channel clock signals to obtain a read sample value group. Then, an interpolation read sample value group, which may be obtained by sampling the read signals in accordance with the middle clock timing of the channel clock signals, is obtained. Then, an amplitude limiting process is conducted for the interpolation read sample value group to obtain an amplitude limiting read sample value group and sample values of less than front and back two clock periods of the channel clock signals in the group are weighted and added. Then, the read sample value group is delayed to obtain a delayed read sample value group and the weighted and added result and the delayed read sample value group are added to obtain an equalized correction read sample value group. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a waveform equalizer mounted on a recording information reproducing apparatus that reproduces recorded information from a recording medium.

  In order to improve the S / N ratio of a read signal read from a recording medium on which digital data is recorded at high density, a technique for performing waveform equalization by performing a filtering process for emphasizing the high frequency band on the read signal is known. ing. At this time, the improvement ratio of the S / N ratio can be increased as the emphasis of the high frequency on the read signal is increased. However, if the high frequency is excessively emphasized, the intersymbol interference increases. In view of this, a waveform equalizer that can apply high-frequency enhancement without increasing intersymbol interference has been proposed (see, for example, Patent Document 1).

  FIG. 1 is a diagram showing a configuration of a recorded information reproducing apparatus equipped with the waveform equalizer proposed by Patent Document 1. In FIG.

  In FIG. 1, a pickup 1 supplies an A / D converter 3 with a read signal obtained by reading an information signal recorded by 8/16 modulation on a recording disk 2 such as a DVD (Digital Versatile Disc). To do. The A / D converter 3 samples the read signal at a timing according to the channel clock, and supplies a read sample value series R including a sample value series obtained at this time to the waveform equalizer 5. The channel clock is a clock having a period of 1T in an 8/16 modulated information signal.

Amplitude limiting circuit of the waveform equalizer 5 51, such read sample value sequence R a is shown in Figure 2 was obtained by amplitude limited by such an amplitude limitation value T _h and -T _h amplitude limited read sample value sequence R _LIM is supplied to the high-frequency emphasis filter 52. That is, the amplitude limiting circuit 51, when the read sample values of the read sample value sequence R is in range of the amplitude limit value -T _h through T _h is as said amplitude limited read the read sample value sequence R Output as sample value series R _LIM . Further, in the case where each of the read sample values of the read sample value sequence R is greater than the amplitude limit value T _h outputs the amplitude limiting value T _h itself as the amplitude limited read sample value sequence R _LIM. On the other hand, when each read sample value of the read sample value series R is smaller than the amplitude limit value −T _h , the amplitude limit value −T _h itself is output as the amplitude limit read sample value series R _LIM . Each of the amplitude limit values T _h and -T _h is a read sample corresponding to 3T, which is the shortest level inversion interval (hereinafter referred to as run length) in 8/16 modulation, as shown in FIG. The value series R is set to a value that does not limit the amplitude.

The high-frequency emphasis filter 52 includes unit delay elements FD _{1 to} FD ₄ , coefficient multipliers M ₁ , M ₂ , M _3, and M _4, and an adder AD that adds the outputs of these coefficient multipliers. The Each of the unit delay elements FD _{1 to} FD ₄ delays the input value by one clock cycle of the channel clock and outputs the delayed value. The coefficient multipliers M ₁ , M ₂ , M ₃ and M ₄ are coefficient multipliers each having a multiplication coefficient [−k, k, k, −k]. That is, the high-frequency emphasis filter 52 is a transversal filter having tap coefficients [−k, k, 0, k, −k]. With this configuration, the high-frequency emphasis filter 52 generates a high-frequency emphasized read sample value sequence in which only the high-frequency component level of the amplitude-limited read sample value sequence R _LIM is increased, and supplies this to the adder 54. .

The adder 54 adds the high-frequency emphasized read sample value series and the read sample value series R supplied after being delayed by two cycles of the channel clock by the delay element 53, and equalizes the addition result. The corrected read sample value series _RH is output.

  Next, the operation of the waveform equalizer 5 will be described.

In general, a reproduction system for reproducing recorded information from a recording medium has a low-pass filter characteristic. Therefore, each read sample in the read sample value series R corresponding to the highest frequency run length 3T in the 8/16 modulated signal. The value is lowered. Therefore, in order to improve the S / N ratio for the read sample value series corresponding to the shortest run length 3T, the high frequency emphasis filter 52 applies only the read sample value series to the read sample value series corresponding to the run length 3T. Increase the value of. Here, it is desirable that the value of the equalization corrected read sample value sequence R _H at While such zero cross point D ₀ after the high frequency enhancement by the high frequency enhancing filter 52 is also shown in FIG. 2 is zero level constant. However, since the high-frequency emphasis filter 52 is a transversal filter having tap coefficients [−k, k, 0, k, −k] as shown in FIG. 1, for example, the time point D ₋₂ and the time point D _{− in} FIG. 2. _{1 If} the read sample values in each are not the same value, the value of the equalization corrected read sample value series _RH at the zero crossing point D ₀ will fluctuate. In particular, when the value of the tap coefficient k is increased so as to apply high-frequency emphasis strongly, the variation becomes larger, which leads to an increase in intersymbol interference.

Therefore, the amplitude limiting circuit 51, at which it such amplitude limitation value T _h and -T _h shown in FIG. 2, the high frequency of the multiplied by the amplitude limitation to the run length 4T or more read sample value sequence R This is supplied to the enhancement filter 52. According to the amplitude limitation by the amplitude limitation circuit 51, as shown in FIG. 2A, when the run length of the read signal is 3T, the interpolation read sample value series RR is directly subjected to the amplitude limitation. The read sample value series R _LIM is supplied to the high frequency enhancement filter 52. On the other hand, the interpolated read sample value sequence RR corresponding to the above runlength 4T is a zero-cross point D ₀ vicinity is within range of the amplitude limiting value -T _h through T _h, exceed this range at other times it ing. Therefore, if the run length of the read signal is equal to or greater than 4T, as shown in (b) in FIG. 2, at the time other than the zero-cross point D ₀ to the value amplitude limit value -T _h or T _h The fixed amplitude limited read sample value series R _LIM is supplied to the high frequency enhancement filter 52.

At this time, the values at the time points D _-2 and D _-1 (or D ₁ and D ₂ ) in FIG. Therefore, even if the value of the tap coefficient k is increased and high-frequency emphasis is strongly applied, the value variation of the equalization correction read sample value series _RH at the zero crossing point D ₀ does not occur, and the intersymbol interference increases. It is suppressed.

  However, when the modulation method of the recording signal recorded on the recording disk 2 is, for example, (1, 7) modulation in which the shortest run length is 2T, the waveform equalizer 5 as shown in FIG. With the configuration, an increase in intersymbol interference cannot be suppressed.

  FIG. 3 is a diagram showing an example of a waveform form of the read sample value series R read from the recording disk 2 on which the information signal is recorded by the modulation method in which the shortest run length is 2T.

As shown in FIG. 3B, when the run length is 3T or more, the amplitude at each of the time points D ₋₂ , D ₋₁ , D _1, and D ₂ due to the amplitude limiting action by the amplitude limiting circuit 51. The limited reading sample values are substantially the same.

However, when the run length 2T, that is, the shortest level inversion interval is equal to or less than twice the clock period in the channel clock signal, as shown in FIG. 3A, the time points D _-2 and D _-1 (or D ₂ And D ₁ ) Amplitude limited read sample values at each do not become the same value. Therefore, if the value of the tap coefficient k is increased to strongly apply high-frequency emphasis, the fluctuation of the value of the equalization correction read sample value series _RH at the zero crossing point D ₀ is further increased, which increases intersymbol interference. It invites.
Japanese Patent Laid-Open No. 11-259985

  The present invention has been made to solve such a problem, and even if the shortest run length of the read signal is not more than twice the clock period of the channel clock signal, the read signal is not increased without increasing the intersymbol interference. An object of the present invention is to provide a waveform equalizer that can apply high-frequency emphasis to the above.

  The waveform equalizer according to claim 1 performs equalization correction by performing waveform equalization processing on a read sample value series obtained by sampling a read signal read from a recording medium according to each clock timing of a channel clock signal. A waveform equalizer for obtaining a read sample value series, which is obtained when the read signal is sampled according to an intermediate clock timing of the channel clock signal based on the read sample value series Interpolating means for obtaining an interpolated read sample value series, amplitude limiting means for obtaining an amplitude limited read sample value series by limiting the interpolated read sample value series with a predetermined amplitude limit value, and in the amplitude limited read sample value series Weights the amplitude limited read sample values less than 2 clock periods before and after the channel clock signal in FIG. The equalization correction is performed by adding a filter that adds and outputs, a delay unit that delays the read sample value series to obtain a delayed read sample value series, and a sum of the delayed read sample value series and the output of the filter Adding means for making a read sample value series.

  The waveform equalizer according to claim 8 performs waveform equalization processing on a read sample value series obtained by sampling a read signal read from a recording medium in accordance with each clock timing of the channel clock signal, and the like. A waveform equalizer for obtaining a correction correction read sample value series, wherein the read sample value series is limited by a predetermined amplitude limit value to obtain an amplitude limit read sample value series, and the amplitude limit read sample A filter that weights and adds amplitude limited read sample values less than two clock cycles before and after the channel clock signal in the value series, and outputs the read signal in the middle of the channel clock signal based on the read sample value series Sample value series that would be obtained when sampling according to the clock timing of Interpolating means obtained as a value series, delay means for delaying the interpolated read sample value series to obtain a delayed interpolated read sample value series, and the sum of the delayed interpolated read sample value series and the output of the filter, etc. And adding means for making a correction correction read sample value series.

  A waveform equalizer according to claim 9 is a waveform equalizer for performing waveform equalization on a read signal obtained by reading an information signal recorded on a recording medium, wherein the read signal is A / D converter that obtains a read sample value series by sampling according to each clock timing of the channel clock signal, and the read signal is sampled at an intermediate timing of each of the clock timings based on the read sample value series Interpolating means for obtaining a read sample value series that would be obtained in the following and obtaining this as an interpolated read sample value series; and limiting the interpolated read sample value series with a predetermined amplitude limit value to obtain an amplitude limited read sample value series Amplitude limiting means to obtain, and amplitude less than 2 clock periods before and after the channel clock signal in the amplitude limited read sample value series A filter for outputting a limit read sample values between each weighted addition to consist.

  A waveform equalizer according to claim 10 performs waveform equalization on a read signal obtained by reading an information signal recorded on a recording medium to obtain an equalization corrected read signal. An A / D converter that samples the read signal according to each clock timing of the channel clock signal to obtain a read sample value series, and an intermediate timing between the clock timings with respect to the read sample value series Interpolating means for interpolating the read sample value series obtained when the read signal is sampled to obtain an interpolated read sample value series; and limiting the read by limiting the interpolated read sample value series with a predetermined amplitude limit value Amplitude limiting means for obtaining a sample value series, and two clock periods before and after the channel clock signal in the amplitude limited read sample value series A filter that weights and adds the amplitude limited read sample values to each other, and an adder that obtains a signal obtained by filtering the filter and adding the read sample value series as the equalization corrected read signal And consist of

  The waveform equalizer according to claim 11 performs waveform equalization processing on a read sample value series obtained by sampling a read signal read from a recording medium in accordance with each clock timing of the channel clock signal. A waveform equalizer for obtaining an equalized correction read sample value series, which is obtained when the read signal is sampled based on the read sample value series according to an intermediate clock timing of the channel clock signal. Interpolating means for obtaining a value series as an interpolated read sample value series, amplitude limiting means for limiting the interpolated read sample value series with a predetermined amplitude limit value to obtain an amplitude limited read sample value series, and the amplitude limited read sample value Amplitude limited read sample values less than 2 clock cycles before and after the channel clock signal in the series A filter for weighted addition and output, a delay means for delaying the interpolated read sample value series to obtain a delayed read sample value series, and the equalized sum of the delayed read sample value series and the output of the filter Adding means for making a corrected read sample value series.

  A waveform equalizer according to claim 12 performs waveform equalization processing on a read sample value series obtained by sampling a read signal read from a recording medium in accordance with each clock timing of a channel clock signal. A waveform equalizer for obtaining a correction correction read sample value series, wherein the read sample value series is limited by a predetermined amplitude limit value to obtain an amplitude limit read sample value series, and the amplitude limit read sample Interpolation means for obtaining a sample value series as an interpolated read sample value series that would be obtained when the read signal was sampled according to the intermediate clock timing of the channel clock signal based on the value series; and the interpolated read sample value Interpolated read sample values less than 2 clock cycles before and after the channel clock signal in the series overlap each other. A filter for adding and outputting, a delay means for delaying the amplitude limited read sample value series to obtain a delayed read sample value series, a sum of the delayed read sample value series and the output of the filter, etc. And adding means for making a correction correction read sample value series.

  According to a thirteenth aspect of the present invention, a waveform equalizer performs waveform equalization processing on a read sample value series obtained by sampling a read signal read from a recording medium in accordance with each clock timing of a channel clock signal. A waveform equalizer for obtaining a correction correction read sample value series, wherein the read sample value series is limited by a predetermined amplitude limit value to obtain an amplitude limit read sample value series, and the amplitude limit read sample A filter that weights and adds amplitude limited read sample values less than two clock cycles before and after the channel clock signal in the value series, and outputs the read signal based on the amplitude limited read sample value series. Interpolate the sample value series that would be obtained when sampling according to the intermediate clock timing Interpolating means for obtaining a sample value series, delay means for delaying the interpolated read sample value series to obtain a delayed read sample value series, and the sum of the delayed read sample value series and the output of the filter, etc. And adding means for making a correction correction read sample value series.

  A recording information reproducing apparatus according to claim 14 is a recording information reproducing apparatus for reproducing recording information from a recording medium, wherein the pickup reads a signal of the recording information from the recording medium, and the reading read by the pickup. A waveform equalizer for performing waveform equalization on a signal to obtain an equalization correction read signal; and a demodulating means for demodulating the equalization correction read signal and outputting a reproduction signal. Is obtained when the read signal is sampled according to an intermediate clock timing of the channel clock signal based on a read sample value series obtained by sampling the read signal according to each clock timing of the channel clock signal. Interpolating means for obtaining a sample value series as an interpolated read sample value series; and Amplitude limiting means for obtaining an amplitude limited read sample value series by limiting with a limit value, and weighted addition of amplitude limited read sample values less than two clock periods before and after the channel clock signal in the amplitude limited read sample value series And a filter for delaying the read sample value series to obtain a delayed read sample value series, and the equalized correction read sample obtained by adding the delayed read sample value series and the output of the filter. Adding means for making a value series.

  A recorded information reproducing apparatus according to claim 15 is a recorded information reproducing apparatus for reproducing recorded information from a recording medium, the pickup for reading a signal of the recorded information from the recording medium, and the reading read by the pickup. A waveform equalizer for performing waveform equalization on a signal to obtain an equalization correction read signal; and a demodulating means for demodulating the equalization correction read signal and outputting a reproduction signal. Amplitude limiting means for limiting the read sample value series obtained by sampling the read signal according to each clock timing of the channel clock signal with a predetermined amplitude limit value to obtain an amplitude limited read sample value series, and Amplitude limited read sample values are weighted and added to amplitude limited read sample values less than two clock cycles before and after the channel clock signal. And an interpolation for obtaining a sample value series that will be obtained when the read signal is sampled in accordance with an intermediate clock timing of the channel clock signal as an interpolated read sample value series based on the read sample value series Means for delaying the interpolated read sample value series to obtain a delayed interpolated read sample value series, and the equalized corrected read sample value obtained by adding the delayed interpolated read sample value series and the output of the filter Adding means for making a series.

  According to a sixteenth aspect of the present invention, there is provided a recorded information reproducing apparatus for reproducing recorded information from a recording medium, a pickup for reading a signal of the recorded information from the recording medium, and a reading read by the pickup. A waveform equalizer for performing waveform equalization on a signal to obtain an equalization correction read signal; and a demodulating means for demodulating the equalization correction read signal and outputting a reproduction signal. A / D converter that samples the read signal according to each clock timing of the channel clock signal to obtain a read sample value series, and based on the read sample value series, the read signal is intermediate between the clock timings. An interpolation method for obtaining a read sample value series that would be obtained when sampling at timing and obtaining this as an interpolated read sample value series Amplitude limiting means for limiting the interpolated read sample value series with a predetermined amplitude limit value to obtain an amplitude limited read sample value series, and two clock periods before and after the channel clock signal in the amplitude limited read sample value series A filter that weights and adds amplitude-restricted read sample values less than each other and outputs the result.

  A recorded information reproducing apparatus according to claim 17 is a recorded information reproducing apparatus for reproducing recorded information from a recording medium, wherein the pickup reads a signal of the recorded information from the recording medium, and the reading is read by the pickup. A waveform equalizer for performing waveform equalization on a signal to obtain an equalization correction read signal; and a demodulating means for demodulating the equalization correction read signal and outputting a reproduction signal. A / D converter that samples the read signal according to each clock timing of the channel clock signal to obtain a read sample value series, and the intermediate timing of each of the clock timings relative to the read sample value series Interpolating means for interpolating the read sample value series obtained when the read signal is sampled to obtain an interpolated read sample value series, and the interpolated read Amplitude limiting means for limiting the sample value series with a predetermined amplitude limit value to obtain an amplitude limited read sample value series, and amplitude limit reading less than two clock periods before and after the channel clock signal in the amplitude limit read sample value series A filter that weights and adds the sample values to each other and outputs, and an adder that obtains, as the equalization-corrected read signal, a signal obtained by performing the filtering process using the filter and adding the read sample value series .

  A recorded information reproducing apparatus according to claim 18 is a recorded information reproducing apparatus for reproducing recorded information from a recording medium, the pickup for reading a signal of the recorded information from the recording medium, and the reading read by the pickup. A waveform equalizer that obtains an equalization corrected read sample value series by performing waveform equalization processing on a read sample value series obtained by sampling a signal according to each clock timing of a channel clock signal, and the equalization corrected read signal And a demodulator that demodulates the read signal and outputs a reproduction signal, wherein the waveform equalizer is configured to sample the read signal according to a clock timing intermediate between the channel clock signals based on the read sample value series. Interpolating means for obtaining a sample value series that will be obtained as an interpolated read sample value series, and the interpolated read sample Amplitude limiting means for limiting the value series with a predetermined amplitude limit value to obtain an amplitude limited read sample value series, and an amplitude limited read sample of less than two clock periods before and after the channel clock signal in the amplitude limited read sample value series A filter for weighting and adding values to each other, a delay means for delaying the interpolated read sample value series to obtain a delayed read sample value series, and a sum of the delayed read sample value series and the output of the filter And adding means for setting the equalized corrected read sample value series.

  A recorded information reproducing apparatus according to claim 19 is a recorded information reproducing apparatus for reproducing recorded information from a recording medium, the pickup for reading a signal of the recorded information from the recording medium, and the reading read by the pickup. A waveform equalizer that obtains an equalization corrected read sample value series by performing waveform equalization processing on a read sample value series obtained by sampling a signal according to each clock timing of a channel clock signal, and the equalization corrected read signal And a demodulating unit that demodulates the read sample value series, and the waveform equalizer limits the read sample value series with a predetermined amplitude limit value to obtain an amplitude limited read sample value series. And based on the amplitude limited read sample value series, the read signal is sampled according to the intermediate clock timing of the channel clock signal. Interpolating means for obtaining a sample value series that will be obtained as an interpolated read sample value series, a filter for weighting and adding interpolated read sample values in the interpolated read sample value series, and the interpolation A filter that weights and adds interpolated read sample values less than two clock cycles before and after the channel clock signal in the read sample value series, and delays the amplitude limited read sample value series to obtain a delayed read sample value series. Delay means for obtaining, and addition means for adding the delayed read sample value series and the output of the filter as the equalization corrected read sample value series.

  A recorded information reproducing apparatus according to claim 20 is a recorded information reproducing apparatus for reproducing recorded information from a recording medium, the pickup for reading a signal of the recorded information from the recording medium, and the reading read by the pickup. A waveform equalizer that obtains an equalization corrected read sample value series by performing waveform equalization processing on a read sample value series obtained by sampling a signal according to each clock timing of a channel clock signal, and the equalization corrected read signal And a demodulating unit that demodulates the read sample value series, and the waveform equalizer limits the read sample value series with a predetermined amplitude limit value to obtain an amplitude limited read sample value series. And amplitude limited read sample values less than 2 clock cycles before and after the channel clock signal in the amplitude limited read sample value series. Based on the filter for weighted addition and output, and the amplitude limited read sample value series, the sample value series that would be obtained when the read signal was sampled according to the intermediate clock timing of the channel clock signal is interpolated and read. Interpolating means obtained as a sample value series, delay means for delaying the interpolated read sample value series to obtain a delayed read sample value series, and adding the delayed read sample value series and the output of the filter are equalized Adding means for making a corrected read sample value series.

  The read signal read from the recording medium is sampled according to the channel clock signal to obtain a read sample value series, and may be obtained when the read signal is sampled according to the intermediate clock timing of the channel clock signal. An interpolated read sample value series is obtained. Then, the result of weighted addition of sample values of less than two clock periods before and after the channel clock signal in the amplitude limited read sample value sequence obtained by performing the amplitude limiting process on the interpolated read sample value sequence, and the above reading The addition result of the delayed read sample value series obtained by delaying the sample value series is defined as an equalization corrected read sample value series.

  Examples of the present invention will be described below.

  FIG. 4 is a diagram showing a configuration of a recorded information reproducing apparatus provided with a waveform equalizer according to the present invention.

  In FIG. 4, a pickup 1 is an A / D converter for reading a read signal obtained by reading an information signal modulated and recorded by, for example, (1, 7) modulation method having a shortest run length of 2T from a recording disk 2. 3 is supplied. The A / D converter 3 samples the read signal at a timing corresponding to the channel clock signal, and supplies a read sample value series R composed of a series of sample values obtained at this time to the waveform equalizer 6. The channel clock signal is a clock signal having a period of 1T in the (1, 7) modulated information signal. That is, the run length 2T is twice as long as the clock period in the channel clock signal.

The waveform equalizer 6 supplies an equalization-corrected read sample value series _RH obtained by performing high-frequency emphasis on the read sample value series R to each of an information demodulation circuit 7 and a PLL (phase locked loop) circuit 8. To do. The data demodulation circuit 7 restores the original information signal by performing (1, 7) demodulation on the equalization corrected read sample value series _RH , and outputs this as a reproduction information signal. The PLL circuit 8 generates a channel clock signal in which the phase error generated in the equalization correction read sample value series _RH is corrected, and supplies this to the A / D converter 3.

  FIG. 5 is a diagram showing an internal configuration of the waveform equalizer 6 according to the present invention.

  In FIG. 5, the interpolation filter 61 performs an interpolation operation on the read sample value series R supplied from the A / D converter 3. By such an interpolation operation, the interpolation filter 61 obtains a sample value series that will be obtained when the read signal read from the recording disk 2 is sampled at an intermediate timing of each clock timing of the channel clock signal. Then, the interpolation filter 61 obtains an interpolated read sample value series RR obtained by interpolating the obtained sample value series in the read sample value series R, and supplies this to the amplitude limiting circuit 51.

In the actual interpolation filter 61, the interpolation calculation process is
(n + 0.5) T
n: Even number
T: 1 channel clock cycle time is spent. Therefore, hereinafter, the operation will be described assuming that a delay of 0.5 · T occurs in the interpolation calculation processing by the interpolation filter 61.

Amplitude limiting circuit 51 supplies the amplitude limited read sample value sequence R _LIM obtained by amplitude limitation such interpolated read sample value sequence RR with the amplitude limiting values T _h and -T _h to the high frequency enhancing filter 52 '. That is, the amplitude limiting circuit 51, when the read sample values in the interpolated read sample value sequence RR is in said amplitude limitation value within -T _h through T _h becomes range, as the amplitude of the interpolated read sample value sequence RR Output as a limited read sample value series R _LIM . Further, in the case where each of the read sample values of the interpolated read sample value sequence RR is greater than the amplitude limit value T _h outputs the amplitude limiting value T _h itself as the amplitude limited read sample value sequence R _LIM. On the other hand, in the case where each of the read sample values of the interpolated read sample value sequence RR is less than the amplitude limiting value -T _h outputs the amplitude limiting value -T _h itself as the amplitude limited read sample value sequence R _LIM. At this time, each of said amplitude limitation value T _h and -T _h is only the interpolated read sample value sequence RR corresponding to the shortest run length 2T is set to a value not placed on the amplitude limitation. That is, the amplitude limiting value T _h is larger than the maximum value of the interval corresponding to the run length 2T in the interpolated read sample value sequence RR, the amplitude limit value -T _h is a section corresponding to the run length 2T Smaller than the minimum value of.

The high-frequency emphasis filter 52 ′ includes unit delay elements FD _{1 to} FD ₃ , coefficient multipliers M ₁ , M ₂ , M _3, and M _4, and an adder AD that adds the outputs of these coefficient multipliers. Is done. Each of the unit delay elements FD _{1 to} FD ₃ delays the input value by one clock cycle of the channel clock and outputs the delayed value. The coefficient multipliers M ₁ , M ₂ , M ₃ and M ₄ are coefficient multipliers each having a multiplication coefficient [−k, k, k, −k]. That is, the high-frequency emphasis filter 52 ′ is a transversal filter having tap coefficients [−k, k, k, −k]. With this configuration, the high-frequency emphasis filter 52 ′ _applies the high-frequency emphasis read sample value sequence whose level is increased only to the sample sequence corresponding to the run length 2T in the amplitude limited read sample value sequence R _LIM. Is generated and supplied to the adder 54. The adder 54 adds the high-frequency emphasized read sample value series and the read sample value series R supplied after being delayed by two cycles of the channel clock by the delay element 53, and equalizes the addition result. The corrected read sample value series _RH is output.

  Next, the operation of the waveform equalizer 6 will be described with reference to FIG.

  6 indicate the respective read samples in the read sample value series R, and the black circle points indicate the interpolated read samples in the interpolated read sample value series RR obtained by the interpolation filter 61. FIG. 6 shows the read samples in the read sample value series R and the interpolated read samples in the interpolated read sample value series RR in each case of run lengths 2T to 4T.

As shown in FIG. 6, each amplitude limitation value T _h and -T _h in the amplitude limiting circuit 51, such that only the interpolated read sample value sequence RR corresponding to the shortest run length 2T is not placed on the amplitude limit Is set to a value. Therefore, as shown in FIG. 6A, when the run length is 2T, the interpolated read sample value series RR is supplied as it is to the high frequency enhancement filter 52 ′ as the amplitude limited read sample value series R _LIM. Is done. On the other hand, when the run length is 3T or more, the interpolated read sample value series RR is within the range of amplitude limit values −T _{h to} T _h only near the zero crossing time D ₀ , but at other times This range is exceeded. Therefore, as in the case run length is equal to or greater than 3T is shown in (b) in FIG. 6, at the time other than the zero-cross point D ₀ is a value which is fixed to the amplitude limiting value -T _h or T _h The amplitude limited read sample value series R _LIM is supplied to the high-frequency emphasis filter 52 ′.

Accordingly, the high-frequency emphasis filter 52 ′ performs amplitude limited read sample values at time points D _−1.5 , D _−0.5 , D _0.5 , and D _1.5 in the amplitude limited read sample value series R _LIM as shown in FIG. Based on the above, the equalization correction read sample value at the time point D ₀ is obtained.

That is, when the equalization correction read sample value at time point D ₀ is Z ₀ ,
Z ₀ = (− k) · Y _−1.5 + k · Y _−0.5 + k · Y _0.5 + (− k) · Y _1.5
Y _-1.5 : Amplitude limited read sample value at time D _-1.5 during R _LIM
Y _-0.5 : Amplitude limited read sample value at time D _-0.5 during R _LIM
Y _0.5 : Amplitude limited read sample value at time D _0.5 during R _LIM
Y _1.5 : Amplitude limited read sample value at time D _1.5 in R _LIM .

At this time, as shown in FIG. 6, the amplitude limited read sample values at the time points D _-1.5 and D _-0.5 (or the time points D _0.5 and D _1.5 ) corresponding to the run length 2T are substantially the same. Further, when the run length is 3T or more, the amplitude limit reading sample value at each of the time points D _−1.5 and D _−0.5 (or time points D _0.5 and D _1.5 ) is also the amplitude limit value −T _h (or T _h). ), They are the same as each other. Therefore, even if the value of the tap coefficient k of the high-frequency emphasis filter 52 ′ is increased so as to strongly apply high-frequency emphasis, the value of the equalization correction read sample value series _RH at the zero crossing point D ₀ remains constant. Therefore, no increase in intersymbol interference occurs.

As described above, in the waveform equalizer shown in FIG. 5, first, the read sample value series R is interpolated at the intermediate timing of the channel clock signal to obtain the interpolated read sample value series RR. Next, an amplitude control process is performed on the interpolated read sample value series RR to obtain an amplitude limited read sample value series R _LIM . Then, in the high frequency emphasis filter 52 ′, the amplitude limited read sample values at each of the four consecutive time points in the amplitude limited read sample value series R _LIM are weighted and added by the coefficient multipliers M _{1 to} M _4, respectively. Here, by delaying the read sample value series R by two clock cycles of the channel clock signal, a read sample value corresponding to an intermediate time point among the four time points is obtained, and this is added to the weighted addition result. The equalization correction read sample value series _RH is obtained.

  However, the number of amplitude-limited read sample values to be weighted and added in the high-frequency emphasis filter 52 ′ is not limited to four, and can be appropriately changed according to the target filter characteristics as long as it is an even number of two or more. It is. At this time, if the number of amplitude-limited read sample values to be weighted is N, the read sample value series R can be delayed by the delay element 53 by a clock period (N / 2) times the channel clock signal. For example, a read sample value corresponding to an intermediate time point among these N amplitude limited read sample values is obtained.

  FIG. 7 is a diagram showing another configuration example of the waveform equalizer 6 according to the present invention.

  In FIG. 7, the double oversampling circuit 62 performs a double oversampling process on the read sample value series R supplied from the A / D converter 3. With this processing, the double oversampling circuit 62 obtains a sample value series that would be obtained when the read signal read from the recording disk 2 was sampled with a clock signal having a clock frequency twice that of the channel clock signal. Ask. The double oversampling circuit 62 supplies the sample value series to the amplitude limiting circuit 51 as an interpolated read sample value series RR.

Amplitude limiting circuit 51 supplies the amplitude limited read sample value sequence R _LIM obtained by amplitude limitation such interpolated read sample value sequence RR with the amplitude limiting values T _h and -T _h to the high frequency enhancing filter 63. That is, the amplitude limiting circuit 51, in the case where each of the read sample values in the interpolated read sample value sequence RR is smaller than the amplitude limiting value T _h, and is greater than the amplitude limiting value -T _h, the interpolation The read sample value series RR is output as it is as the amplitude limited read sample value series R _LIM . Further, in the case where each of the read sample values of the interpolated read sample value sequence RR is greater than the amplitude limit value T _h outputs the amplitude limiting value T _h itself as the amplitude limited read sample value sequence R _LIM. On the other hand, in the case where each of the read sample values of the interpolated read sample value sequence RR is less than the amplitude limiting value -T _h outputs the amplitude limiting value -T _h itself as the amplitude limited read sample value sequence R _LIM. At this time, each of said amplitude limitation value T _h and -T _h is only the interpolated read sample value sequence RR corresponding to the shortest run length 2T is set to a value not placed on the amplitude limitation.

The high-frequency emphasis filter 63 includes delay elements FFD _{1 to} FFD ₃ as shown in FIG. 7, coefficient multipliers M ₁ , M ₂ , M ₃ and M _4, and addition for adding the outputs of these coefficient multipliers. And AD. Each of the delay elements FFD _{1 to} FFD ₃ sequentially takes the input value at a clock timing having a frequency twice that of the channel clock signal, and outputs the delayed value by one period of the channel clock signal. The coefficient multipliers M ₁ , M ₂ , M ₃ and M ₄ are coefficient multipliers each having a multiplication coefficient [−k, k, k, −k]. That is, the high-frequency emphasis filter 63 is a transversal filter having tap coefficients [−k, 0, k, 0, k, 0, −k].

With this configuration, the high frequency emphasis filter 63 generates a high frequency emphasis read sample value series in which the level is increased only for the sample series corresponding to the run length 2T in the amplitude limited read sample value series R _LIM. This is supplied to the adder 54. The adder 54 adds the high frequency emphasized read sample value series and the interpolated read sample value series RR supplied after being delayed by the delay element 64 by three periods of the channel clock, and the addition result is equalized. Output as a correction correction read sample value series _RH .

  Next, the operation of the waveform equalizer 6 shown in FIG. 7 will be described with reference to FIG.

  8 indicate the respective sample values in the interpolated read sample value series RR output from the double oversampling circuit 62 in the case of each of run lengths 2T to 4T.

As shown in FIG. 8, each of the amplitude limit values T _h and −T _h in the amplitude limit circuit 51 is such that only the interpolated read sample value series RR corresponding to the shortest run length 2T does not limit the amplitude. It is set to a valid value. Therefore, as shown in FIG. 8A, when the run length is 2T, the interpolated read sample value series RR is supplied as it is to the high frequency emphasis filter 63 as the amplitude limited read sample value series R _LIM. The On the other hand, when the run length is 3T or more, it is within the range of the amplitude limit value −T _{h to} T _{h in the} vicinity of the zero crossing time point D ₀ , but exceeds this range at other time points. Thus, when the run length is equal to or greater than 3T, as shown in (b) in FIG. 8, the fixed value is the amplitude limit value -T _h or T _h at the time other than the zero-cross point D ₀ near The amplitude limited read sample value series R _LIM is supplied to the high frequency enhancement filter 63.

At this time, the high-frequency emphasis filter 63 performs amplitude limited read sample values at time points D _−1.5 , D _−0.5 , D _0.5 , and D _1.5 in the amplitude limited read sample value series R _LIM as shown in FIG. Based on the above, the equalization correction read sample value at the time point D ₀ is obtained.

That is, when the equalization correction read sample value at time point D ₀ is Z ₀ ,
Z ₀ = (− k) · Y _−1.5 + k · Y _−0.5 + k · Y _0.5 + (− k) · Y _1.5
Y _-1.5 : Amplitude limited read sample value at time D _-1.5 during R _LIM
Y _-0.5 : Amplitude limited read sample value at time D _-0.5 during R _LIM
Y _0.5 : Amplitude limited read sample value at time D _0.5 during R _LIM
Y _1.5 : Amplitude limited read sample value at time D _1.5 in R _LIM .

At this time, as shown in FIG. 8, the amplitude limited read sample values at the time points D _-1.5 and D _-0.5 (or time points D _0.5 and D _1.5 ) corresponding to the run length 2T are substantially the same. Further, the amplitude limit read sample values at the time points D _-1.5 and D _-0.5 (or time points D _0.5 and D _1.5 ) corresponding to run lengths of 3T or more are also set to the amplitude limit value -T _h (or T _h ). Because they are fixed, they are the same.

Therefore, even if set to a large value of the tap coefficients k to multiply strongly high frequency emphasis in the high frequency enhancing filter 63, the equalization corrected read sample value sequence R _H at the zero cross point D ₀ remains constant Therefore, intersymbol interference does not increase.

  In the embodiment shown in FIG. 7, the double oversampling circuit 62 performs a double oversampling process on the read sample value series R supplied from the A / D converter 3. The configuration is not limited. For example, instead of using the double oversampling circuit 62, the read signal may be sampled with a clock signal having a frequency twice that of the channel clock signal at the stage of the A / D converter 3. is there.

In the waveform equalizer shown in FIG. 5 or FIG. 7, a sample value series corresponding to the center tap in the high-frequency emphasis filter 52 ′ (or 63) is added to the adder 54 via the delay element 53 (or 64). To supply. That is, only the sample value series corresponding to the center tap in the high-frequency emphasis filter 52 ′ (or 63) is reflected in the equalization correction read sample value series _RH without being subjected to amplitude limitation by the amplitude limiting circuit 51. It is. However, the amplitude limit by the amplitude limit circuit 51 may be applied to the sample value series corresponding to the center tap.

  FIG. 9 and FIG. 10 are diagrams showing modifications of the waveform equalizer made in view of this point. FIG. 9 is a diagram showing a modification of the waveform equalizer shown in FIG. 5, and FIG. 10 is a diagram showing a modification of the waveform equalizer shown in FIG.

  Further, in the high-frequency emphasis filter 63 shown in FIGS. 7 and 10, it is possible to acquire a sample value series corresponding to the center tap as described above in the filter.

  FIG. 11 is a diagram showing a modification of the waveform equalizer shown in FIGS. 7 and 10 made in view of the above points.

In the high frequency emphasis filter 63 ′ shown in FIG. 11, the delay element FFD ₂ of the high frequency emphasis filter 63 shown in FIG. 7 and FIG. 10 is divided into two stages of delay elements FFD _2A and FFD _2B. The output of the FFD _2A is supplied to the adder AD. At this time, each of the delay elements FFD _2A and FFD _2B is a delay element that takes in an input value at a clock timing having a frequency twice that of the channel clock signal and supplies it to the next stage. According to such a configuration, the sample value series corresponding to the center tap as described above is extracted from the delay element FFD _2A, and is directly supplied to the adder AD. Therefore, according to the configuration shown in FIG. 11, the sample value series corresponding to the center tap is converted into the equalized correction read sample value series without using the delay element 64 and the adder 54 as shown in FIGS. It can be reflected in _RH .

  In the waveform equalizer shown in FIG. 5, only the sample value series corresponding to the center tap in the high-frequency emphasis filter 52 ′ is not subjected to the interpolation processing by the interpolation filter 61, but corresponds to this center tap. Interpolation processing by the interpolation filter 61 may be performed only on the sample value series.

  FIG. 12 is a diagram showing another modification of the waveform equalizer made in view of the above points.

  The functions of the interpolation filter 61, the amplitude limiting circuit 51, the high-frequency emphasis filter 52 ′, and the adder 54 shown in FIG. 12 are the same as those shown in FIG.

In FIG. 12, an interpolation filter 61 applies an interpolated read sample value series obtained by performing the above-described interpolation operation processing to the read sample value series R supplied from the A / D converter 3 to a delay element 53 ′. Supply. The interpolation filter 61 spends the time corresponding to 0.5 period of the channel clock in the interpolation calculation process. The delay element 53 ′ delays the interpolated read sample value series supplied from the interpolating filter 61 by one cycle of the channel clock, and then supplies it to the adder 54. On the other hand, the amplitude limiting circuit 51, the A / D converter 3 amplitude limited read sample value sequence obtained by amplitude limiting by the amplitude limit value T _h and -T _h to the supplied read sample value sequence R from R _LIM is supplied to the high-frequency emphasis filter 52 ′. The high-frequency emphasis filter 52 ′ generates a high-frequency emphasis read sample value sequence having an increased level only for the sample sequence corresponding to the run length 2T in the amplitude limited read sample value sequence R _LIM , This is supplied to the adder 54. The adder 54 adds the high frequency emphasized read sample value series and the interpolated read sample value series supplied after being delayed by one cycle of the channel clock by the delay element 53 ′, and equalizes the addition result. The corrected read sample value series _RH is output.

As described above, in the waveform equalizer shown in FIG. 12, first, amplitude control processing is performed on the read sample value series R to obtain the amplitude limited read sample value series R _LIM . Then, in the high frequency emphasis filter 52 ′, the amplitude limited read sample values at each of the four consecutive time points in the amplitude limited read sample value series R _LIM are weighted and added by the coefficient multipliers M _{1 to} M _4, respectively. During this time, an interpolated read sample value series is obtained by interpolating the read sample value series R at the intermediate timing of the channel clock signal. Then, by delaying the interpolated read sample value series by one clock cycle of the channel clock signal, a read sample value corresponding to an intermediate time point among the four time points is obtained, and this is added to the weighted addition result. The equalization correction read sample value series _RH is obtained.

  At this time, in the waveform equalizer shown in FIG. 12, assuming that the number of amplitude limited read sample values to be weighted and added is N, the interpolated read sample value series is converted into (N / 2) of the channel clock signal by the delay element 53 ′. -1) If the delay is performed by a multiple of the clock period, a read sample value corresponding to an intermediate time point among these N amplitude limited read sample values can be obtained.

  In the waveform equalizer shown in FIG. 12, the sample value series corresponding to the center tap of the high-frequency emphasis filter 52 ′, that is, the sample value corresponding to the intermediate point in time between the four amplitude limited read sample values to be weighted and added. The amplitude is not limited only to the series. However, instead of FIG. 12, the configuration shown in FIG. 13 is adopted so that the amplitude limiting circuit 51 limits the amplitude on the sample value series corresponding to the center tap of the high-frequency emphasis filter 52 ′. good.

  In the above embodiment, the case where the waveform equalizer according to the present invention is applied to the information reproducing apparatus for reproducing the recorded information from the recording medium has been described. However, the application is not limited to the information reproducing apparatus. In short, if the transmission system has a characteristic in which the high frequency band is attenuated, the waveform equalizer according to the present invention can be mounted to perform high frequency enhancement without increasing intersymbol interference. .

In the high frequency emphasis filter, the amplitude limited read sample values at each of the four time points D in the amplitude limited read sample value series R _LIM are weighted and added by the coefficient multipliers M _{1 to} M ₄ , respectively. The number of amplitude limited read sample values to be weighted and added may be at least two. In short, the high-frequency emphasis filter may be configured such that amplitude limited read sample values less than two clock cycles before and after the channel clock signal are weighted and added.

FIG. 3 is a diagram showing a configuration of a recorded information reproducing apparatus provided with a waveform equalizer 5; 6 is a diagram showing a read sample value series R obtained when an information signal recorded by 8/16 modulation is read, and an amplitude limited read sample value series R _LIM obtained by a waveform equalizer 5. FIG. FIG. 6 is a diagram showing a read sample value series R obtained when a (1, 7) modulated and recorded information signal is read, and an amplitude limited read sample value series R _LIM obtained by a waveform equalizer 5; It is a figure which shows the structure of the recorded information reproducing | regenerating apparatus provided with the waveform equalizer 6 by this invention. It is a figure which shows an example of an internal structure of the waveform equalizer 6 by this invention. (1, 7) A diagram showing a read sample value series R obtained when a modulation-recorded information signal is read, and an amplitude limited read sample value series R _LIM obtained by the waveform equalizer 6 according to the present invention. is there. It is a figure which shows another example of the waveform equalizer 6 by this invention. (1, 7) shows a read sample value series R obtained when a modulated and recorded information signal is read, and an amplitude limited read sample value series R _LIM obtained by the waveform equalizer 6 shown in FIG. FIG. It is a figure which shows the modification of the waveform equalizer 6 shown by FIG. It is a figure which shows the modification of the waveform equalizer 6 shown by FIG. It is a figure which shows the modification of the waveform equalizer 6 shown by FIG.7 and FIG.10. It is a figure which shows the modification of the waveform equalizer 6 shown by FIG. It is a figure which shows the modification of the waveform equalizer 6 shown by FIG.

Explanation of symbols

6 Waveform equalizer 51 Amplitude limiting circuit 52 ', 63, 63' High frequency emphasis filter 61 Interpolation filter 62 Double oversampling circuit

Claims (20)

A waveform equalizer that obtains an equalized corrected read sample value sequence by performing waveform equalization processing on a read sample value sequence obtained by sampling a read signal read from a recording medium according to each clock timing of a channel clock signal There,
Interpolating means for obtaining, as an interpolated read sample value series, a sample value series that will be obtained when the read signal is sampled according to the intermediate clock timing of the channel clock signal based on the read sample value series;
Amplitude limiting means for limiting the interpolated read sample value series with a predetermined amplitude limit value to obtain an amplitude limited read sample value series;
A filter for weighting and adding amplitude limited read sample values less than two clock periods before and after the channel clock signal in the amplitude limited read sample value series;
Delay means for delaying the read sample value series to obtain a delayed read sample value series;
A waveform equalizer comprising: addition means for adding the delayed read sample value series and the output of the filter as the equalization corrected read sample value series.   2. The waveform equalizer according to claim 1, wherein the amplitude limit value is larger than a maximum value of a signal level in a section having the shortest level inversion interval in the read signal.   3. The waveform equalizer according to claim 2, wherein the shortest level inversion interval is twice a clock cycle in the channel clock signal.   The interpolating means is a double oversampling circuit that obtains the interpolated read sample value series by sampling the read signal at a clock timing having a frequency twice that of the channel clock signal. Waveform equalizer as described.   The waveform equalizer according to claim 1, wherein the filter is a high-frequency emphasis filter that increases a value of a high-frequency component in the amplitude-limited read sample value series.   6. The waveform equalizer according to claim 5, wherein the high frequency component is a portion having the shortest level inversion interval in the amplitude limited read sample value series.   The waveform equalizer according to claim 1, wherein the filter is a transversal filter having tap coefficients of [−k, k, k, −k]. A waveform equalizer that obtains an equalized corrected read sample value sequence by performing waveform equalization processing on a read sample value sequence obtained by sampling a read signal read from a recording medium according to each clock timing of a channel clock signal There,
Amplitude limiting means for limiting the read sample value series with a predetermined amplitude limit value to obtain an amplitude limited read sample value series;
A filter for weighting and adding amplitude limited read sample values less than two clock periods before and after the channel clock signal in the amplitude limited read sample value series;
Interpolating means for obtaining, as an interpolated read sample value series, a sample value series that will be obtained when the read signal is sampled according to the intermediate clock timing of the channel clock signal based on the read sample value series;
Delay means for delaying the interpolated read sample value series to obtain a delayed interpolated read sample value series;
A waveform equalizer comprising: adding means for adding the delayed interpolation read sample value series and the output of the filter as the equalization corrected read sample value series. A waveform equalizer that performs waveform equalization on a read signal obtained by reading an information signal recorded on a recording medium,
An A / D converter that samples the read signal according to each clock timing of the channel clock signal to obtain a read sample value series;
Interpolation means for obtaining a read sample value series that would be obtained when the read signal was sampled at an intermediate timing of each of the clock timings based on the read sample value series, and obtaining this as an interpolated read sample value series;
Amplitude limiting means for limiting the interpolated read sample value series with a predetermined amplitude limit value to obtain an amplitude limited read sample value series;
A waveform equalizer comprising: a filter for weighting and adding amplitude limited read sample values less than two clock cycles before and after the channel clock signal in the amplitude limited read sample value series. A waveform equalizer that obtains an equalization corrected read signal by performing waveform equalization on a read signal obtained by reading an information signal recorded on a recording medium,
An A / D converter that samples the read signal according to each clock timing of the channel clock signal to obtain a read sample value series;
Interpolation means for interpolating a read sample value series obtained by sampling the read signal at an intermediate timing of each of the clock timings with respect to the read sample value series to obtain an interpolated read sample value series;
Amplitude limiting means for limiting the interpolated read sample value series with a predetermined amplitude limit value to obtain an amplitude limited read sample value series;
A filter for weighting and adding amplitude limited read sample values less than two clock periods before and after the channel clock signal in the amplitude limited read sample value series;
A waveform equalizer comprising: an adder that obtains the equalized corrected read signal by adding the read sample value series to a signal obtained by filtering processing using the filter. A waveform equalizer that obtains an equalized corrected read sample value sequence by performing waveform equalization processing on a read sample value sequence obtained by sampling a read signal read from a recording medium according to each clock timing of a channel clock signal There,
Interpolating means for obtaining, as an interpolated read sample value series, a sample value series that will be obtained when the read signal is sampled according to the intermediate clock timing of the channel clock signal based on the read sample value series;
Amplitude limiting means for limiting the interpolated read sample value series with a predetermined amplitude limit value to obtain an amplitude limited read sample value series;
A filter for weighting and adding amplitude limited read sample values less than two clock periods before and after the channel clock signal in the amplitude limited read sample value series;
Delay means for delaying the interpolated read sample value series to obtain a delayed read sample value series;
A waveform equalizer comprising: addition means for adding the delayed read sample value series and the output of the filter as the equalization corrected read sample value series. A waveform equalizer that obtains an equalized corrected read sample value sequence by performing waveform equalization processing on a read sample value sequence obtained by sampling a read signal read from a recording medium according to each clock timing of a channel clock signal There,
Amplitude limiting means for limiting the read sample value series with a predetermined amplitude limit value to obtain an amplitude limited read sample value series;
Interpolating means for obtaining, as an interpolated read sample value series, a sample value series that would be obtained when the read signal was sampled according to an intermediate clock timing of the channel clock signal based on the amplitude limited read sample value series;
A filter for weighting and adding interpolated read sample values less than two clock cycles before and after the channel clock signal in the interpolated read sample value series;
Delay means for delaying the amplitude limited read sample value series to obtain a delayed read sample value series;
A waveform equalizer comprising: addition means for adding the delayed read sample value series and the output of the filter as the equalization corrected read sample value series. A waveform equalizer that obtains an equalized corrected read sample value sequence by performing waveform equalization processing on a read sample value sequence obtained by sampling a read signal read from a recording medium according to each clock timing of a channel clock signal There,
Amplitude limiting means for limiting the read sample value series with a predetermined amplitude limit value to obtain an amplitude limited read sample value series;
A filter for weighting and adding amplitude limited read sample values less than two clock periods before and after the channel clock signal in the amplitude limited read sample value series;
Interpolating means for obtaining, as an interpolated read sample value series, a sample value series that would be obtained when the read signal was sampled according to an intermediate clock timing of the channel clock signal based on the amplitude limited read sample value series;
Delay means for delaying the interpolated read sample value series to obtain a delayed read sample value series;
A waveform equalizer comprising: addition means for adding the delayed read sample value series and the output of the filter as the equalization corrected read sample value series. A recorded information reproducing apparatus for reproducing recorded information from a recording medium,
A pickup for reading a signal of the recording information from the recording medium, a waveform equalizer for obtaining an equalization correction read signal by performing waveform equalization on the read signal read by the pickup, and the equalization correction read signal Demodulating means for demodulating and outputting a reproduction signal,
The waveform equalizer is
Based on a read sample value series obtained by sampling the read signal according to each clock timing of the channel clock signal, the read signal is obtained when the read signal is sampled according to an intermediate clock timing of the channel clock signal. Interpolation means for obtaining a wax sample value series as an interpolated read sample value series;
Amplitude limiting means for limiting the interpolated read sample value series with a predetermined amplitude limit value to obtain an amplitude limited read sample value series;
A filter for weighting and adding amplitude limited read sample values less than two clock periods before and after the channel clock signal in the amplitude limited read sample value series;
Delay means for delaying the read sample value series to obtain a delayed read sample value series;
The recording information reproducing apparatus comprising: addition means for adding the delayed read sample value series and the output of the filter as the equalization corrected read sample value series. A recorded information reproducing apparatus for reproducing recorded information from a recording medium,
A pickup for reading a signal of the recording information from the recording medium, a waveform equalizer for obtaining an equalization correction read signal by performing waveform equalization on the read signal read by the pickup, and the equalization correction read signal Demodulating means for demodulating and outputting a reproduction signal,
The waveform equalizer is
Amplitude limiting means for limiting the read sample value series obtained by sampling the read signal according to each clock timing of the channel clock signal with a predetermined amplitude limit value to obtain an amplitude limited read sample value series;
A filter for weighting and adding amplitude limited read sample values less than two clock periods before and after the channel clock signal in the amplitude limited read sample value series;
Interpolating means for obtaining, as an interpolated read sample value series, a sample value series that will be obtained when the read signal is sampled according to the intermediate clock timing of the channel clock signal based on the read sample value series;
Delay means for delaying the interpolated read sample value series to obtain a delayed interpolated read sample value series;
And a means for adding the delayed interpolation read sample value series and the output of the filter as the equalization corrected read sample value series. A recorded information reproducing apparatus for reproducing recorded information from a recording medium,
A pickup for reading a signal of the recording information from the recording medium, a waveform equalizer for obtaining an equalization correction read signal by performing waveform equalization on the read signal read by the pickup, and the equalization correction read signal Demodulating means for demodulating and outputting a reproduction signal,
The waveform equalizer is
An A / D converter that samples the read signal according to each clock timing of the channel clock signal to obtain a read sample value series;
Interpolation means for obtaining a read sample value series that would be obtained when the read signal was sampled at an intermediate timing of each of the clock timings based on the read sample value series, and obtaining this as an interpolated read sample value series;
Amplitude limiting means for limiting the interpolated read sample value series with a predetermined amplitude limit value to obtain an amplitude limited read sample value series;
And a filter for weighting and adding amplitude limited read sample values less than two clock cycles before and after the channel clock signal in the amplitude limited read sample value series. A recorded information reproducing apparatus for reproducing recorded information from a recording medium,
A pickup for reading a signal of the recording information from the recording medium, a waveform equalizer for obtaining an equalization correction read signal by performing waveform equalization on the read signal read by the pickup, and the equalization correction read signal Demodulating means for demodulating and outputting a reproduction signal,
The waveform equalizer is
An A / D converter that samples the read signal according to each clock timing of the channel clock signal to obtain a read sample value series;
Interpolation means for interpolating a read sample value series obtained by sampling the read signal at an intermediate timing of each of the clock timings with respect to the read sample value series to obtain an interpolated read sample value series;
Amplitude limiting means for limiting the interpolated read sample value series with a predetermined amplitude limit value to obtain an amplitude limited read sample value series;
A filter for weighting and adding amplitude limited read sample values less than two clock periods before and after the channel clock signal in the amplitude limited read sample value series;
An adder that obtains, as the equalization corrected read signal, a signal obtained by adding the read sample value series to a signal obtained by filtering processing using the filter. A recorded information reproducing apparatus for reproducing recorded information from a recording medium,
A pickup that reads a signal of the recording information from the recording medium, and a waveform equalization process is performed on a read sample value series obtained by sampling the read signal read by the pickup according to each clock timing of the channel clock signal A waveform equalizer that obtains an equalization correction read sample value series, and a demodulator that demodulates the equalization correction read signal and outputs a reproduction signal,
The waveform equalizer is
Interpolating means for obtaining, as an interpolated read sample value series, a sample value series that will be obtained when the read signal is sampled according to the intermediate clock timing of the channel clock signal based on the read sample value series;
Amplitude limiting means for limiting the interpolated read sample value series with a predetermined amplitude limit value to obtain an amplitude limited read sample value series;
A filter for weighting and adding amplitude limited read sample values less than two clock periods before and after the channel clock signal in the amplitude limited read sample value series;
Delay means for delaying the interpolated read sample value series to obtain a delayed read sample value series;
And a means for adding the delayed read sample value series and the output of the filter as the equalization corrected read sample value series. A recorded information reproducing apparatus for reproducing recorded information from a recording medium,
A pickup that reads a signal of the recording information from the recording medium, and a waveform equalization process is performed on a read sample value series obtained by sampling the read signal read by the pickup according to each clock timing of the channel clock signal A waveform equalizer that obtains an equalization correction read sample value series, and a demodulator that demodulates the equalization correction read signal and outputs a reproduction signal,
The waveform equalizer is
Amplitude limiting means for limiting the read sample value series with a predetermined amplitude limit value to obtain an amplitude limited read sample value series;
Interpolating means for obtaining, as an interpolated read sample value series, a sample value series that would be obtained when the read signal was sampled according to an intermediate clock timing of the channel clock signal based on the amplitude limited read sample value series;
A filter for weighting and adding the interpolated read sample values in the interpolated read sample value series,
A filter for weighting and adding interpolated read sample values less than two clock cycles before and after the channel clock signal in the interpolated read sample value series;
Delay means for delaying the amplitude limited read sample value series to obtain a delayed read sample value series, and adding the delayed read sample value series and the output of the filter as the equalization corrected read sample value series And a recorded information reproducing apparatus. A recorded information reproducing apparatus for reproducing recorded information from a recording medium,
A pickup that reads a signal of the recording information from the recording medium, and a waveform equalization process is performed on a read sample value series obtained by sampling the read signal read by the pickup according to each clock timing of the channel clock signal A waveform equalizer that obtains an equalization correction read sample value series, and a demodulator that demodulates the equalization correction read signal and outputs a reproduction signal,
The waveform equalizer is
Amplitude limiting means for limiting the read sample value series with a predetermined amplitude limit value to obtain an amplitude limited read sample value series;
A filter for weighting and adding amplitude limited read sample values less than two clock periods before and after the channel clock signal in the amplitude limited read sample value series;
Interpolating means for obtaining, as an interpolated read sample value series, a sample value series that would be obtained when the read signal was sampled according to an intermediate clock timing of the channel clock signal based on the amplitude limited read sample value series;
Delay means for delaying the interpolated read sample value series to obtain a delayed read sample value series;
And a means for adding the delayed read sample value series and the output of the filter as the equalization corrected read sample value series.

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