JP2000156041A - Optical information reproducing device and optical information reproducing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical information reproducing device and the optical information reproducing method capable of equalizing the distortion of a reproduced signal due to the servo deviation without emphasizing the noise. SOLUTION: The optical information recording device is allowed to continue the adaptive equalization to the optimum equalizing condition against each recording medium, since the arrangement is made so that a servo error adjusting means for adjusting the the servo error of the focusing and tracking of the light beam and also an LMS(least mean square) computing element 9 as the adaptive equalizing means for adaptively equalizing the reproducing impulse response after the adjustment of the servo error as the target reproducing property are provided in the optical information reproducing device for reproducing the information recorded on a recording medium by irradiating the recording medium with the light beam from an optical pickup through an objective lens, thereby the detection margin is available to be wider, and the high density recording/reproducing operation is attained since the reproduction is allowed even in the narrow margin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention can be applied to an optical information reproducing apparatus and an optical information reproducing method for reproducing information recorded on an optical recording medium.

[0002]

2. Description of the Related Art Conventionally, information is magnetized (MO: magneto-optical disk), phase change (DVD: digital versatile disk), dye decolorization (CD-R: rewritable optical disk), pit depth (CD: optical disk) In a recording / reproducing apparatus that modulates a physical change such as a digital signal into a digital signal and records and reproduces it on a recording medium, there is a detection method of equalizing a reproduced signal to a partial response (PR) method and performing maximum likelihood decoding with a Viterbi decoder or the like. It has been used as a data reproduction method.

[0003] As such a partial response system, PR is selected according to the linear density of a reproduced signal.
(1,1), PR (1,2,1), PR (1,2,2)
1), PR (1, 1, 1, 1) and the like are known.
(T. Narahara, et. Al., "A Par
tial-Response Maximum-Lik
elifection Detection Method
for MO Recording ", Jpn.JA.
ppl. Rhys. Vol. 36 (1997) pp. 5
49-556, Part 1, No. IB, January
y 1997)

[0004]

By the way, in the above-described partial response system, when the linear density is high, the focus is shifted (defocus), the skew due to the tilt, or the high NA (NUMERICAL APER) is used.
(TURE: numerical aperture of the objective lens) If there is a shift in the distance between the two groups in the two-group objective lens, the high-frequency portion of the reproduced signal is insufficient, and the reproduced signal is adaptively equalized to the partial response characteristics as described above. There is a disadvantage that the noise component is over-equalized, thereby raising the error rate.

As an example, FIG. 1 shows an impulse response when an optical disk reproduction signal having a cutoff frequency of 0.37 of a reproduction channel clock frequency is defocused. FIG. 1 shows PR at zero defocus.
The (1, 2, 1) Viterbi detector equalizes the reproduction margin so as to maximize it. The interval between the coefficients a0 to a8 is the channel clock cycle 1T. The assumed partial response is PR (1, 2, 1). The impulse response of the reproduced signal when the focus actuator defocuses (above the arrow) under the equalization conditions is shown. Here, since the tap coefficients of the coefficients a1 and a7 that are 3T and 4T (T is a channel clock cycle) away from the center fluctuate, they move in a direction to lose the high frequency characteristics.

Under these conditions of large defocus, the PR
In the case of adaptive equalization to (1, 2, 1), error characteristics are degraded rather than when reproduction is performed with equalization conditions in a state of zero defocus.

The optimum equalization condition is the SNR of the disc.
(IEEE Transac) because it changes according to the frequency characteristic of (Signal to NoiseRetio).
In the fixed response, the detection margin between the disks decreases. This can be optimally adjusted while measuring the Viterbi decoding margin by the signal processing device and the signal processing method of Japanese Patent Application No. 9-357440 by the same applicant and the same inventor. However, performing this adjustment during the reproducing operation requires a number of rotations of the disk, and it is impossible to correct the deviation during the continuous operation.

The present invention has been made in view of the above points, and it is an object of the present invention to propose an optical information reproducing apparatus and an optical information reproducing method which can equalize a distortion of a reproduced signal due to a servo shift without emphasizing noise. Is what you do.

[0009]

An optical information reproducing apparatus according to the present invention irradiates a recording medium with a light beam from an optical pickup via an objective lens, and transmits information recorded on the recording medium. In an optical information reproducing apparatus for reproducing, a servo error adjusting means for adjusting a servo error of focus and tracking of the light beam, and an adaptive equalizing means for adaptively equalizing a reproduction impulse response after the servo error adjustment as a target reproduction characteristic. , Is provided.

Further, the optical information reproducing method of the present invention is directed to the optical information reproducing method of irradiating a recording medium with a light beam from an optical pickup via an objective lens to reproduce information recorded on the recording medium. A servo error adjustment step for adjusting the servo error of the beam focus servo;
An adaptive equalization step of adaptively equalizing the reproduction impulse response after the servo error adjustment as a target reproduction characteristic.

According to the optical information reproducing apparatus and the optical information reproducing method of the present invention, the following operations are performed. The adaptive equalization means uses the reproduced RF signal as a target input, a signal sequence obtained by filtering a signal sequence estimated by a decoder by an adaptive filter as an equalization target, compares the target input with the equalization target, and calculates a square error. Is set so as to minimize the adaptive filter, and the reproduction characteristic is estimated.

The adaptive equalizing means, after estimating the reproduction characteristics, uses the signal sequence obtained by convolving the signal sequence estimated by the decoder with the coefficient of the adaptive filter as a target input, and sets the reproduced RF signal as an equalization target, and performs adaptive equalization. I do.

As described above, by adaptively equalizing the reproduction response obtained after the servo error adjustment, distortion due to servo deviation is equalized without unnecessarily emphasizing noise.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an adaptive equalizer according to an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a block diagram showing a configuration of an adaptive equalizer in the optical disc reproducing apparatus according to the embodiment of the present invention. The adaptive equalizer according to the embodiment of the present invention shown in FIG. 2 obtains a reproduction impulse response based on a reproduction signal from a disk and performs adaptive equalization.

In FIG. 2, a reproduction RF read from a disc (not shown) by an optical pickup is provided at a terminal 1.
The signal S1 is supplied, and the analog equalizer 2 performs waveform equalization so as to have a PR characteristic by noise limitation and high-frequency compensation. The reproduced RF signal S2 after the waveform equalization is A
The signal is supplied to the / D converter 3, sampled and quantized by a channel clock synchronized with the signal by an internal PLL, and converted into a digital RF waveform sample sequence S3.

First, when a disk is loaded into an optical disk reproducing apparatus, each servo adjustment of a focus servo and a tracking servo is performed, for example, by the focus control apparatus and method of Japanese Patent Application No. 9-84090 by the same applicant as the present applicant. As shown in an optical disk device, by optimizing a servo offset in a focus servo in an optical disk device using an optical head including a two-group objective lens having a numerical aperture exceeding 0.6,
The adjustment is performed so as to adjust the disc reproduction signal to be the best, or the so-called hill-climbing method or the like in which the servo is adjusted to a position where the envelope signal of the reproduction RF signal S1 is maximized.

The focus control apparatus and method and the optical disk apparatus disclosed in Japanese Patent Application No. 9-84090 are specifically designed so that a reproduced RF signal S1 read from an optical disk rotated by a spindle motor by an optical system is an RF signal. The signal is amplified by the amplifier, and the amplitude is detected by the amplitude detector. The detected amplitude is sent to the control unit. The control unit sends a control signal to the adjustment unit based on the amplitude. On the other hand, the focus error detector performs a predetermined operation on the output of the photodetector of the optical system for detecting the reflected light from the optical disk, and generates an error signal for controlling the focus of the optical system. Then, the adjusting unit returns a control amount for performing focus control of the optical pickup of the optical system to the optical system based on the error signal from the focus error detecting unit and the control signal from the control unit. In this way,
By optimizing the amount of residual focus error (offset) of an optical system using an objective lens having a high numerical aperture, the focus error during operation is always kept within an allowable range.

The analog equalizer 2 is disclosed in, for example, Japanese Patent Application No. 9-35 filed by the same applicant and the same inventor as the present applicant.
With the signal processing device and signal processing method of No. 7440,
AGC (automatic gain control) used for servo circuit, PLL
(Phase locked loop) When the number of taps of the FIR type equalizer in the loop is large, the tap delay becomes large and the control operation becomes unstable. Therefore, the amplitude error and phase error calculated to the target values of AGC and PLL are fed back. By doing so, the evaluation function is optimally adjusted by ensuring stability.

The signal processing apparatus and the signal processing method disclosed in Japanese Patent Application No. 9-357440 specifically include a signal processing method for correcting waveform distortion caused by waveform interference of a signal sequence by a signal delay type equalizer. This signal sequence suppresses the level fluctuation of the short repetition period of the signal sequence received by the signal transmission system by the signal gain adjusting means provided in the preceding stage of the equalizer, and
From the output side of this equalizer, the level variation of this signal sequence in a long repetition period is detected, and the level variation of this signal sequence is corrected by the level variation of this long repetition period to adjust the level reference of this signal sequence. Is suppressed, the operation of this loop can be stably maintained even when a signal processing unit that causes a signal delay is provided in the signal gain adjustment loop of the signal processing device.

Here, at the time of each adjustment, the movable contacts D of the switches (1) 4, (2) 6, and (3) 8 are connected to the fixed contacts C. Therefore, the RF waveform sequence S3 output from the A / D converter 3 is directly supplied to the Viterbi detector 7 via the switch (2) 6. Each adjustment may be performed based on the temporarily determined bit pattern S5 that is Viterbi decoded by the Viterbi detector 7 and output. When PR equalization is performed by the analog equalizer 2, the detected R
The F waveform sequence S2 has a correlation with the preceding and following waveform sequences. The Viterbi detector 7 uses this correlation to determine the most probable bit pattern waveform sequence S5.

After the above-described servo adjustments, the movable contacts D of the switches (1) 4, (2) 6, and (3) 8 are connected to the fixed contacts A. At this time, the reproduction impulse response is identified by checking the optimum equalization state when the reproduction impulse response in the adaptive equalizer in the adjusted state is input and estimating the reproduction characteristic. The identification is performed by an LMS algorithm using an LMS (Least Mean Square) calculator 9. LM
The S calculator 9 is a transversal filter type calculator belonging to the FIR type, and adjusts the coefficient S7 so as to minimize the square of the difference between the target value and the waveform series S4 of the filter output at each sampling time. It is.

At this stage, the reproduced RF waveform sequence S3 is supplied to the target value input terminal of the LMS computing unit 9 via the switch (3) 8, and the input terminal to be equalized via the switch (2) 6. A waveform sequence S4 obtained by adaptively filtering the recording NRZI sequence S5 estimated by the Viterbi detector 7 by the FIR type transversal filter 5 via the switch (1) 4 is supplied.

In the LMS calculator 9, the reproduced RF waveform series S
3 and the transversal filtering waveform sequence S4 are compared, and a coefficient S7 is output so as to minimize the square error. The coefficient S7 is fed back to the coefficient input terminal as a coefficient of the transversal filter 5 and supplied. You.

In this case, the waveform sequence S4 of the transversal filter output is a waveform sequence obtained by convoluting the coefficient sequence S7 of the transversal filter with the recorded NRZI signal sequence S5. The gain of each coefficient [ak] S7 after convergence becomes an estimated value of a bit response (impulse response) corresponding to the reproduction channels a0 to a8 as shown in FIG. The coefficient series [ak] S7 of the estimated reproduction characteristic is supplied to the memory 10 and stored in a predetermined table.

After estimating the reproduction characteristics described above, the movable contacts D of the switches (1) 4, (2) 6, and (3) 8 are connected to the fixed contacts B. At this time, adaptive equalization is performed by the adaptive equalizer using the estimated coefficient S7. The target value input terminal of the LMS equalizer 9 is provisionally determined, that is, the recording NRZI sequence S5 estimated by the Viterbi detector 7 via the switch (2) 6 is stored in the memory 10 Response estimate [ak]
The target reproduction signal S6 convolved in S8 is supplied, and the reproduction RF waveform sequence S4 after being filtered by the transversal filter 5 via the switch (1) 4 is supplied to the input terminal to be equalized.

In this way, the adaptive equalizer described above adaptively equalizes the initial reproduction response at the time of reproduction.

During reproduction, a focus shift may occur due to a temperature characteristic of a circuit system or the like. In this case, the tap coefficients b7 and b1 of the specific equalizer change in order to equalize the response at the time of optimal focus. The coefficient changes b7 and b1 with respect to the defocus amount at this time are as shown in FIG. When the change of this coefficient is large, the above-mentioned applicant of the present invention has a Japanese Patent Application No. 9-8409.
As shown in the focus control apparatus and method No. 0 and the optical disc apparatus, by optimizing the servo offset (defocus amount), the focus is always optimized by adjusting the disc reproduction signal to be the best. It becomes possible.

The same processing as in Japanese Patent Application No. 9-84090 can be performed on factors other than defocus that change the reproduction characteristics.

In this case, the number of taps of the coefficient sequence of the estimated sequence is the same as that at the time of equalization. However, for the sake of simplicity, at the time of equalization, only the coefficients of a few taps near the center are used. It may be a goal.

When calculating the estimated sequence, the NRZI
The Viterbi decoding result from the Viterbi detector 7 is used as the sequence S5.
The RZI sequence may be supplied from outside.

The optical information reproducing apparatus of this embodiment irradiates a recording medium with a light beam from an optical pickup via an objective lens and reproduces information recorded on the recording medium. Servo error adjustment means for adjusting focus and tracking servo error,
LMS as adaptive equalization means for adaptively equalizing the reproduction impulse response after servo error adjustment as target reproduction characteristics
Since the calculation unit 9 is provided, it is possible to continue adaptive equalization to the optimum equalization condition for each recording medium,
This makes it possible to increase the detection margin,
Further, since reproduction is possible even with a narrow margin, high-density recording and reproduction can be performed.

The optical information reproducing apparatus according to the present embodiment
In the above description, since the servo error adjustment in the servo error adjusting means is calibrated based on the adjustment value of the LMS computing unit 9 as the adaptive equalizing means, the detection of the servo deviation is easy and the accuracy of the servo adjustment is improved. be able to.

The optical information reproducing apparatus according to the present embodiment
In the above description, the LMS calculator 9 as an adaptive equalizing means
Is used as a target input, a signal sequence S4 obtained by filtering a signal sequence S5 estimated by a Viterbi detector 7 as a decoder by a transversal filter 5 as an adaptive filter, and And the reproduction characteristic is estimated by setting the coefficient S7 of the adaptive filter so that the square error is minimized. Therefore, the output of the adaptive filter is adapted to the signal sequence estimated by the decoder. Since the coefficient series of the filter is convolved, and each coefficient after the convergence of the adaptive filter becomes an estimated value of the bit response of the reproduction channel, the reproduction characteristics can be easily and reliably estimated.

The optical information reproducing apparatus according to the present embodiment
In the above description, the LMS calculator 9 as an adaptive equalizing means
Sets the signal sequence S6 obtained by convolving the signal sequence S5 estimated by the Viterbi detector 7 as a decoder with the coefficient S8 of the transversal filter 5 as an adaptive filter after estimating the reproduction characteristic, and sets the reproduction RF signal S4 as a target input. Since adaptive equalization is performed as the equalization target, it is possible to adaptively equalize the initial reproduction response obtained after the servo error adjustment.

The optical information reproducing method according to the present embodiment
In a light information reproducing method of irradiating a light beam from an optical pickup to a recording medium via an objective lens and reproducing information recorded on the recording medium, a servo error adjustment step of performing a servo error adjustment of a focus servo of the light beam, An adaptive equalization step of adaptively equalizing the reproduction impulse response after the servo error adjustment as a target reproduction characteristic is provided, so that it is possible to continuously adaptively equalize to the optimum equalization condition for each recording medium. The detection margin can be widened, and reproduction can be performed even with a narrow margin, so that high-density recording and reproduction can be performed.

The optical information reproducing method according to the present embodiment
In the above description, since the servo error adjustment in the servo error adjustment step is calibrated based on the adjustment value in the adaptive equalization step, the detection of the servo deviation is easy, and the accuracy of the servo adjustment can be improved.

The optical information reproducing method according to the present embodiment
In the above description, the adaptive equalization step includes a reproduction RF signal as a target input, a signal sequence obtained by filtering a signal sequence estimated by a decoder with an adaptive filter as an equalization target, and comparing the target input with the equalization target, The coefficients of the adaptive filter are set so as to minimize the square error, and the reproduction characteristics are estimated. Therefore, the output of the adaptive filter is obtained by convolving the coefficient sequence of the adaptive filter with the signal sequence estimated by the decoder. Since each coefficient after the convergence of the adaptive filter becomes an estimated value of the bit response of the reproduction channel, the reproduction characteristics can be easily and quickly estimated.

The optical information reproducing method according to the present embodiment
In the above, the adaptive equalization step includes, after estimating a reproduction characteristic, a signal sequence obtained by convolving a signal sequence estimated by a decoder with a coefficient of an adaptive filter as a target input, a reproduced RF signal as an equalization target, and adaptive equalization. Is performed, it is possible to adaptively equalize the initial reproduction response obtained after the servo error adjustment.

In the above-described embodiment,
Even if the optical disc is a DVD-RAM, other optical discs such as a mini disc (MD) and a rewritable C
It may be a D-ROM or a magneto-optical disk (MO).

[0041]

The optical information reproducing apparatus of the present invention irradiates a recording medium with a light beam from an optical pickup via an objective lens and reproduces information recorded on the recording medium. Each of the recording media is provided with servo error adjusting means for adjusting the servo error of beam focus and tracking, and adaptive equalizing means for adaptively equalizing the reproduction impulse response after the servo error adjustment as a target reproduction characteristic. , It is possible to continue adaptive equalization to the optimal equalization condition, thereby making it possible to widen the detection margin and to enable high-density recording and reproduction because reproduction is possible even with a narrow margin. This has the effect.

Further, in the optical information reproducing apparatus of the present invention, the servo error adjustment in the servo error adjusting means is calibrated based on the adjustment value of the adaptive equalizing means in the above description. The effect is that detection is easy and the accuracy of servo adjustment can be increased.

In the optical information reproducing apparatus according to the present invention, the adaptive equalizing means equalizes a signal sequence obtained by filtering a signal sequence estimated by a decoder with an adaptive filter using a reproduced RF signal as a target input. As the target, the target input is compared with the equalization target, the coefficient of the adaptive filter is set so that the square error is minimized, and the reproduction characteristic is estimated. Since the coefficient sequence of the adaptive filter is convolved with the signal sequence estimated by the decoder, and each coefficient after the convergence of the adaptive filter becomes the estimated value of the bit response of the reproduction channel, the reproduction characteristics can be easily and reliably estimated. This has the effect that it can be performed.

Further, in the optical information reproducing apparatus according to the present invention, the adaptive equalizing means may include, after estimating the reproducing characteristic,
Using the signal sequence obtained by convolving the signal sequence estimated by the decoder with the coefficients of the adaptive filter as a target input, the reproduction R
Since the adaptive equalization is performed with the F signal as the equalization target, an effect is provided that the initial reproduction response obtained after the servo error adjustment can be adaptively equalized.

Further, according to the optical information reproducing method of the present invention, a recording medium is irradiated with a light beam from an optical pickup via an objective lens to reproduce information recorded on the recording medium. A servo error adjustment step for adjusting the servo error of the beam focus servo;
An adaptive equalization step for adaptively equalizing the reproduction impulse response after the servo error adjustment as a target reproduction characteristic is provided, so that it is possible to continuously adaptively equalize to the optimum equalization condition for each recording medium. Thus, it is possible to obtain a wide detection margin, and it is possible to perform reproduction even with a narrow margin, so that high-density recording and reproduction can be performed.

In the optical information reproducing method according to the present invention, the servo error adjustment in the servo error adjustment step is calibrated based on the adjustment value in the adaptive equalization step. The effect is that detection is easy and the accuracy of servo adjustment can be increased.

In the optical information reproducing method according to the present invention, the adaptive equalizing step includes equalizing the signal sequence obtained by filtering the signal sequence estimated by the decoder with the adaptive filter using the reproduced RF signal as a target input. As the target, the target input is compared with the equalization target, the coefficient of the adaptive filter is set so that the square error is minimized, and the reproduction characteristic is estimated. The signal sequence estimated by the decoder is convolved with the coefficient sequence of the adaptive filter, and each coefficient after the convergence of the adaptive filter becomes the estimated value of the bit response of the reproduction channel. The effect that it can be performed is produced.

Further, in the optical information reproducing method of the present invention, in the above, in the adaptive equalizing step, after estimating the reproducing characteristic, the signal obtained by convolving the signal sequence estimated by the decoder with the coefficient of the adaptive filter is used. Since adaptive equalization is performed with the sequence as a target input and the reproduction RF signal as an equalization target, there is an effect that adaptive equalization can be performed on an initial reproduction response obtained after servo error adjustment.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an impulse response at the time of defocusing according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of an adaptive equalizer according to the embodiment of the present invention.

FIG. 3 is a diagram illustrating tap coefficients of an equalizer after adaptation at the time of defocusing according to the embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Terminal, 2 ... Analog equalizer, 3 ... A / D converter, 4 ... Switch (1), 5 ... Transversal filter, 6 ... Switch (2), 7 ... Viterbi detector , 8 ... switch (3), 9 ... LMS computing unit, 10
…… Memory, 11 …… Convolution unit

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Kamon Uemura 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo F-term in Sony Corporation (reference) 5D044 BC02 CC04 FG02 GL02 GL32 5D090 AA01 CC04 DD03 DD05 EE13 EE17 FF41 5D118 AA13 BA01 BB01 BD01 BF02 BF16 BF17 CA01 CA08 CA11 CA13 CD02 CD03 CD08

Claims (8)

[Claims] 1. An optical information reproducing apparatus which irradiates a recording medium with a light beam from an optical pickup via an objective lens and reproduces information recorded on the recording medium, wherein a servo error adjustment of focus and tracking of the light beam is performed. An optical information reproducing apparatus, comprising: servo error adjusting means for performing the following; and adaptive equalizing means for adaptively equalizing the reproduction impulse response after the servo error adjustment as target reproduction characteristics. 2. An optical information reproducing apparatus according to claim 1, wherein said servo error adjustment in said servo error adjustment means is calibrated based on an adjustment value of said adaptive equalization means. Information playback device. 3. The optical information reproducing apparatus according to claim 1, wherein the adaptive equalizing means receives a reproduced RF signal as a target input,
With the signal sequence obtained by filtering the signal sequence estimated by the decoder using an adaptive filter as an equalization target, the target input is compared with the equalization target, and the coefficients of the adaptive filter are set so that the square error is minimized. An optical information reproducing apparatus characterized in that reproduction characteristics are estimated. 4. The optical information reproducing apparatus according to claim 3, wherein the adaptive equalization means convolves the signal sequence estimated by the decoder with the coefficient of the adaptive filter after estimating the reproduction characteristic. An optical information reproducing apparatus characterized in that adaptive equalization is performed using the reproduced RF signal as an equalization target with the target input as a target input. 5. An optical information reproducing method for irradiating a recording medium with a light beam from an optical pickup via an objective lens and reproducing information recorded on the recording medium, wherein a servo error adjustment of a focus servo of the light beam is performed. An optical information reproducing method, comprising: a servo error adjusting step to be performed; and an adaptive equalizing step of adaptively equalizing a reproduction impulse response after the servo error adjustment as a target reproduction characteristic. 6. The optical information reproducing method according to claim 5, wherein the servo error adjustment in the servo error adjustment step is calibrated based on the adjustment value in the adaptive equalization step. Information reproduction method. 7. The optical information reproducing method according to claim 5, wherein in the adaptive equalization step, a signal sequence obtained by filtering a signal sequence estimated by a decoder with an adaptive filter using a reproduced RF signal as a target input is equalized. Comparing the target input with the equalization target, setting coefficients of the adaptive filter so as to minimize a square error, and estimating a reproduction characteristic. Method. 8. The optical information reproducing method according to claim 5, wherein said adaptive equalization step comprises, after estimating said reproduction characteristic, convolving a signal sequence estimated by said decoder with a coefficient of said adaptive filter. Wherein the adaptive equalization is performed using the reproduced RF signal as an object to be equalized as a target input.