JPH05128729A - Magnetic reproducing device - Google Patents

Abstract

PURPOSE:To detect and discriminate the abnormality of the operation state and to take a countermeasure like tap coefficient update stop in accordance with the result by comparing an input signal or an output signal for an adaptive control part with a prescribed reference value or comparing signals in inter- channel corresponding parts of plural channels. CONSTITUTION:An input value discriminating circuit 31 is inserted to the way of the input signal line from a detection characteristic circuit 13 to an adaptive control part 17, and an error signal discriminating circuit 32 is inserted to the way of the error signal line from an adder 16 as an error detector to the control part 17, and a tap coefficient value discriminating circuit 33 is inserted to the way of the tap coefficient signal line from the control part 17 to a digital filter 14. The occurrence of the abnormal state like dropout, noise, or burst error during the reproducing operation is detected by these circuits 31 to 33, and coefficient update is so limited that the tap coefficient is not an abnormal value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic reproducing device,
In particular, the present invention relates to a magnetic reproducing device for converting a video signal into a digital signal and reproducing a signal recorded on a magnetic recording medium by utilizing a so-called partial response system.

[0002]

2. Description of the Related Art Generally, in magnetic recording / reproducing, an equalizer is used to compensate for amplitude distortion, phase distortion, etc. due to recording / reproducing characteristics with respect to a magnetic recording medium. In recent years, even in such magnetic recording / reproduction, an adaptive equalization method used in communication has been adopted.

Adaptive equalization has been conventionally developed as a technique for performing high-speed data transmission using a telephone line. In a telephone line, the transmission line characteristics change depending on the connection state of the line. Therefore, if the fixed equalizer is used, the transmission line characteristics cannot be completely corrected, and it becomes necessary to adaptively adjust the characteristics of the equalizer.

In such a communication system, a method (automatic equalization) of transmitting a necessary signal after transmitting a signal whose waveform is known in advance and checking transmission line characteristics, and a signal to be transmitted itself are used. There is a method (adaptive equalization) for examining transmission line characteristics. In either case, the purpose of the equalizer is to faithfully restore the transmission signal waveform by automatically removing the distortion from the reception signal waveform that has been distorted when passing through the transmission path.

In order to consider the application of the above-mentioned adaptive equalization to magnetic recording / reproducing, a magnetic tape (video tape) is used as a magnetic recording / reproducing apparatus by converting a video signal into a digital signal and using a so-called partial response system. It is assumed that a digital VTR (video tape recorder) that records and reproduces data is recorded. The partial response method is a method of shaping the spectrum of the code by positively utilizing intersymbol interference due to the transfer characteristic of the transmission path (or recording medium). For example, in the partial response class IV, NRZI code, interleaved NR
ZI code and the like belong. A so-called precoder is provided on the recording side, and the input data is converted into an intermediate sequence in order to avoid propagation of a code error during reproduction (identification). FIG. 6 shows an example of the configuration on the reproducing side when the adaptive equalization system is adopted in a digital VTR that performs magnetic recording and reproduction by using such a partial response system.

In FIG. 6, a magnetic signal recorded on a magnetic tape (not shown) is converted into an electric signal by the magnetic head 101, amplified by the reproduction amplifier 102, and sent to the detection characteristic circuit 103. The detection characteristic circuit 103 has a characteristic (1 + D) which is the detection characteristic (encoding characteristic) of the partial response.
The output signal from the detection characteristic circuit 103 is a so-called FIR.
After being supplied to the equalizer 104 including a (finite impulse response) filter or a transversal filter and subjected to an adaptive equalizing process, the decoding circuit 10
5, the data sequence is decoded at the time of recording by discriminating between "1" and "0" by level comparison (comparing) or the like.

The output d from the decoding circuit 105 is sent to the adder (error detector) 106 and the output y from the equalizer 104 is subtracted, whereby an error (residual) e is taken out, and this error e is obtained. It is sent to the adaptive control unit 107. The output x from the detection characteristic circuit 103 is supplied to the adaptive control unit 107 as a so-called reference input. The adaptive control unit 107 adjusts the filter characteristic of the equalizer 104 so as to minimize the signal power of the error (residual error). When a so-called transversal filter is used for the equalizer 104, the multiplication coefficient (tap coefficient) for each tap is adaptively modified and updated, so that the characteristics of the transversal filter are the electromagnetic characteristics during magnetic recording and reproduction. It is adjusted to have a shape close to the inverse characteristic of the conversion characteristic.

The output from the decoding circuit 105 is sent to the signal processing circuit 108 for reproduction of the sync block, error correction, etc., and then to the video signal processing circuit 109 for restoration of the original image data. .. Besides this, although not shown,
The output data from the signal processing circuit 108 is sent to an audio signal processing circuit, a subcode signal processing circuit, etc., and each processing is performed.

[0009]

By the way, during actual recording / reproduction in such a digital VTR (video tape recorder), so-called dropout, burst error, or clogging of the magnetic head (clogging). Etc. may occur, and when such an abnormality occurs, some countermeasure is required. For example,
If the adaptive control unit 107, the equalizer 104, and the like perform the steady adaptive control operation despite the occurrence of the abnormality, the tap coefficient is updated to an incorrect value, which is correct. The conversion operation is not performed. Further, if this abnormal state continues for a long time, the value becomes uncorrectable, and there is a possibility that the equalizing ability is lost.

Therefore, when an abnormality occurs due to the dropout, burst error, clogging, etc., it is important to detect it as soon as possible and take some necessary measures.

By the way, in a device such as a digital VTR which has an enormous amount of data to be recorded / reproduced, particularly in a VTR of HD (high definition) TV signal, for example, the relative speed between the magnetic head and the tape is increased or recording is performed. By increasing the number of playback channels, the amount of data that can be recorded and played is significantly increased. In this case, each recording / reproducing channel has its own circuit, and its own signal processing is performed. However, since the conditions for actual recording / reproducing are almost the same and the correlations of the signal levels etc. are high, these It is conceivable to focus on the difference between the recording / reproducing signals of the channels.

The present invention has been made in view of such a situation, and when an abnormality such as a dropout, a burst error, or a clogging occurs, these abnormalities can be quickly detected and the adaptive equalization operation can be performed. An object of the present invention is to provide a magnetic reproducing device that can prevent adverse effects.

[0013]

A magnetic reproducing apparatus according to a first invention of the present application is a magnetic reproducing apparatus for reproducing magnetic data recorded on a magnetic recording medium, in which a characteristic of a reproduced signal from a magnetic head is compensated. A filter serving as an equalizer, a decoding circuit for decoding an output signal from the filter, and an adaptive control for adaptively adjusting the characteristics of the filter based on an input signal to the filter and an input / output signal to the decoding circuit. The above-described problem is solved by including a unit and a determination unit that compares the input signal or the output signal of the adaptive control unit with a reference value to determine whether the value of the signal is appropriate.

The magnetic reproducing apparatus according to the second invention of the present application is an equalizer for compensating the characteristics of the reproduction signal from the magnetic head in the magnetic reproducing apparatus for reproducing the magnetic data recorded on the magnetic recording medium. It has a filter, a decoding circuit for decoding the output signal from the filter, and an adaptive control unit for adaptively adjusting the characteristics of the filter based on the input signal to the filter and the input / output signal to the decoding circuit. By providing at least two channels of a reproduction system formed by the above, and providing comparison means for judging whether or not the operation is normal by comparing the signals of the corresponding portions of these channels with each other, To solve.

Here, the determining means determines whether the magnitude of the input signal to the filter is appropriate, and whether the magnitude of the error signal between the output from the decoding circuit and the output from the filter is appropriate. , And whether or not the value of the tap coefficient updated and output by the adaptive control unit is appropriate, to determine whether or not the tap coefficient of the filter is actually updated. do it. Further, the comparison means compares, for example, the stability of the state between the respective channels, and examples of the stability index include input / output signals to the filter, output signals from the decoding circuit, and the like. As the signal of the equalization circuit system, the error signal,
The correction amount of the tap coefficient can be used.

[0016]

An abnormal operation state is detected and judged by comparing an input signal or an output signal to the adaptive control unit with a predetermined reference value or by comparing signals of corresponding portions between a plurality of channels. According to this result, necessary measures, for example, stopping the tap coefficient update, can be taken.

[0017]

1 is a block circuit diagram showing a schematic structure of a reproducing system of a digital VTR as described above as an embodiment of a magnetic reproducing apparatus according to the present invention. In FIG. 1, a magnetic signal recorded on a magnetic tape (not shown) is converted into an electric signal by a magnetic head 11 in a mechanical block (not shown) of a VTR and then amplified by a reproduction amplifier 12. It is sent to the detection characteristic circuit 13. The detection characteristic circuit 13 has the characteristic (1 + D) which is the detection characteristic (encoding characteristic) of the partial response described above. The output signal from the detection characteristic circuit 13 is supplied to the digital filter 14, which is a main part of the equalizer. A so-called FIR (finite impulse response) filter or a transversal filter is generally used as the digital filter 14, and its filter characteristic is adaptively adjusted by an adaptive control unit 17 described later. The output signal from the filter 14 is supplied to the decoding circuit 15 and is discriminated as "1" or "0" by level comparison (comparing) or the like to decode the data sequence at the time of recording. The output signal from the decoding circuit 15 is taken out via the output terminal 15 _OT and sent to the signal processing circuit 108 shown in FIG.

The adder (error detector) 16 is the decoding circuit 1
An error (residual) e is taken out by subtracting the output y of the equalizer filter 14 from the output d of 5, and this error e is sent to the adaptive control unit 17. The output x from the detection characteristic circuit 13 is supplied to the adaptive control unit 17 as a so-called reference input. The adaptive control unit 17 modifies and updates the coefficient (tap coefficient) of the digital filter 14 so as to minimize the signal power of the error (residual), so that the equalizer characteristic is an electromagnetic conversion characteristic during magnetic recording and reproduction. It is adjusted to have a shape close to the inverse characteristic of. That is,
The digital filter 14 and the adaptive control unit 17 constitute a so-called adaptive filter, and the adaptive equalizer can be regarded as one using an adaptive filter for the equalizer.

In FIG. 1, the input value judging circuit 31 moves from the adder (error detector) 16 to the adaptive control unit 17 in the middle of the input signal path from the detection characteristic circuit 13 to the adaptive control unit 17.
An error signal determination circuit 32 is inserted in the middle of the error signal path to the digital filter 14, and a tap coefficient value determination circuit 33 is inserted in the middle of the tap coefficient signal path from the adaptive control circuit 17 to the digital filter 14. These determination circuits 31 to
33 detects the occurrence of an abnormal state due to so-called dropout, noise, burst error, etc. during playback operation, and limits the tap coefficient when updating it so that it does not take an abnormal value. Of the
The input value determination circuit 31 determines whether the magnitude of the input signal is appropriate, the error signal determination circuit 32 determines whether the magnitude of the error signal is appropriate, and the tap coefficient value determination circuit 33 determines the tap coefficient to be updated. It is to judge whether or not the value of is appropriate. Each of these determination circuits will be further described below.

The input value judgment circuit 31 judges whether or not the level of the input signal is within a predetermined appropriate input value range, and when it is not within this appropriate value range, updating of the tap coefficient is prohibited. is doing. This is because the signal input to the equalizer is within a certain range during normal operation, but the input may suddenly increase or decrease for some reason, so the input signal is limited. is there.

The error signal judgment circuit 32 judges whether or not it is within a predetermined appropriate error signal range, and prohibits the updating of the tap coefficient when it is outside this appropriate value range. This is because when the adaptive equalization algorithm works well (converges), the error signal takes a steady value in a relatively narrow range according to the S / N, but deviates greatly from this steady value range. In this case, it is considered that the state of the signal has changed (abnormal state), so that the error signal is limited.

Next, the tap coefficient value determination circuit 33 also determines whether or not the tap coefficient value is within a predetermined range of appropriate tap coefficients,
When the value is out of this range, updating of the tap coefficient is prohibited. This is because even when the tap coefficient is considered to have converged in adaptive equalization, the value of the coefficient repeatedly repeats small fluctuations due to noise, etc., but the fluctuation is within a certain range, and This is because there is a range in which the tap coefficient can be set even when the tap coefficient settles in a convergent state, and it is considered that some abnormality has occurred when the tap coefficient is out of these ranges.

These conditions may be used alone or in combination. When used in combination, for example, after the input value determination circuit 31 first determines whether or not the input value is appropriate, the error signal e is calculated from the filter output and the desired response (output of the decoding circuit 15).
This error signal e is checked by the error signal determination circuit 32 as described above, and if it is within the normal range, the adaptive control unit 17 calculates a new tap coefficient value. After the tap coefficient value determination circuit 33 checks whether or not each of the calculated tap coefficient values is an appropriate value, the actual tap coefficient is updated in the digital filter 14 for the first time. When each determination condition is not satisfied, the algorithm is stopped at that point, the update of the tap coefficient is prohibited, and the previous tap coefficient is used as it is.

Here, the range of each appropriate value in each of the above judgment conditions is set in advance by experience or experiment, and R
Record on OM or tape. Alternatively, the error signal and the tap coefficient value may be obtained as an average value of values in a certain section during the actual equalization algorithm as the value of the converged state, and the determination may be performed based on the difference from the average value. .. The threshold value for making a determination using such a difference may be stored in advance in a ROM, a tape, or the like as in the above.

Next, the filter 14 and the adaptive controller 17
An example of a specific configuration of a so-called adaptive filter including and will be described with reference to FIG. In FIG. 4, the reference input x from the input terminal 14 _IN is a delay element according to the number of taps, for example, four delay blocks 21a, 21.
It is sent to the series circuit of b, 21c and 21d. Input x ₀ from the input terminal 14 _IN and each delay element 21a, 21
Outputs x- ₁ , x- ₂ , x- ₃ , x from b, 21c, 21d
_-4 is a coefficient multiplier 22a, 22b, 22c, 2 respectively
2d and 22e, and are multiplied by filter coefficients (filter tap coefficients) w ₀ , w ₁ , w ₂ , w ₃ and w ₄ , respectively, and then added. That is, the coefficient multipliers 22a, 2
The outputs from 2b are added by the adder 23a, the output from the coefficient multiplier 22c and the output from the adder 23a are added by the adder 23b, and the same applies to the coefficient multipliers 22d and 23d in the adders 23c and 23d. The output from 22e is also sequentially added to form an output y, which is sent to the decoding circuit 15. Each filter coefficient w ₀ , w ₁ , w ₂ , w ₃ , w ₄ is
It is adapted to be modified by a coefficient modification (update) control signal from the adaptive controller 17.

As the adaptive algorithm used in the adaptive control unit 17, many methods have been proposed.
As one specific example thereof, an LMS (least mean square, least mean square) algorithm will be described. Here, the number of the delay elements is generalized to L, and the delay elements 21 ₁ , 21 ₂ , ..., 21 _L are set. At this time, the first input x ₀ and each of these delay elements 23 ₁ ,
23 ₂ , ..., Each output from 23 _L x _-1 , x _-2 , ...
., X- _L are coefficient multipliers 24 ₀ , 24 ₁ , 2 respectively
4 _2, ..., is transmitted to the 24 _L, the filter coefficients are w _0, w _1, w _2, is multiplied ..., and w _L, shall be added is sent to the adder.

The input data at the k-th sampling period (time k) of the data sequence of the input x and the delayed output data from the delay elements 21 ₁ , 21 ₂ , ..., 21 _L are respectively x _k , X _k-1 , x _k-2 , ..., x
_{When kL} is set, the input vector X _k subjected to FIR filtering is set as X _k = [x _k x _k-1 x _k-2 ... X _kL ] ^T (1). T in the equation (1) represents a transposed symbol. For this input vector X _k, each filter coefficient (weighting coefficient) and _{w k0, w k1, w k2} , ···, w kL, when the FIR filter output and y _k, the relationship between the input and output follows (2)
It becomes like a formula.

Y _k = w _k0 x _k + w _k1 x _k-1 + ... + w _kL x _kL (2) Further, a filter coefficient vector (weight vector) W
a _k, if W _k = _{[w k0 w k1 w k2 ··· w} kL ] ^T ··· (3) the definition, input-output relationship ^{_{is, y k = X k T W}} k = W k T X k ... is described as (4). If the desired response is d _k , the error ε _{k from the} output is expressed as ε _k = d _k −y _k = d _k −X _k ^T W _k (5). The following equation is used to update W _k so that ε _k approaches 0.

[0029] W _{k +} 1 = is _{W k -μ ▽ k ··· (6} ) μ in this equation, is the gain factor that determines the speed and stability of adaptation, ▽ _k represents the gradient. The LMS algorithm, ▽ _k is not estimated from the short-term average of epsilon _k ^2, used by partially differentiating epsilon _k ² directly. ^{_{▽ k = δε k 2 / δW}} = -2ε k X k ··· (7) The equation (7) is substituted into the equation (6), the coefficient update _{equation, W k + 1 = W k} + 2με k It is expressed as X _k (8).

In FIG. 2, the input value determination circuit 31 can be inserted and connected between the input terminal 14 _IN and the adaptive control unit 17, and the error signal determination circuit 32 can be inserted between the adder 16 and the adaptive control unit 17. Can be inserted and connected, and the coefficient multipliers 22a to 22e of the adaptive controller 17 and the digital filter 14 can be connected.
The tap coefficient value determination circuit 33 can be inserted between the two, and by providing at least one of them, appropriate adaptive equalization can be performed without being affected by a sudden change.

Here, FIG. 3 shows a concrete example of the change of the tap coefficient with the passage of time. A of FIG. 3 is a conventional example, and B of FIG. 3 is an embodiment of the present invention as described above. It corresponds. During the period T _D in FIGS. 3A and 3B, the signal is abnormal due to the above-mentioned dropout or the like.

First, FIG. 3A shows an example of execution of a conventional algorithm. However, the value of the tap coefficient greatly changes due to disturbance, dropout, etc., and normal equalization cannot be performed. It takes time to return to. On the other hand, in the algorithm of the embodiment of the present invention shown in FIG. 3B, since the tap coefficient is not changed (prohibited) with respect to a sporadic input abnormality, it is not adversely affected. Since the change of the tap coefficient is limited in this way, it is possible to quickly return to the original state after the abnormality of the signal such as dropout ends.

Next, another embodiment of the present invention will be described with reference to FIG.
Will be described with reference to. In FIG. 4, the magnetic signals recorded on the magnetic tape (not shown) are converted into electric signals by the magnetic heads 1 and 11 used for the rotary head of the VTR, and then amplified by the reproduction amplifiers 2 and 12, respectively. The reproduction signal from the reproduction amplifier 2 is sent to the detection characteristic circuit 3, and the reproduction signal from the reproduction amplifier 12 is sent to the detection characteristic circuit 13. The output signal from the detection characteristic circuit 3 is supplied to the digital filter 4, which is a main part of the equalizer. As the filter 4, a so-called FIR (finite impulse response) filter or a transversal filter is used as described above, and its filter characteristic is adaptively adjusted by the adaptive control unit 7 described later. This filter 4
The output signal from is supplied to the decoding circuit 5, and the data series at the time of recording is decoded by discriminating between "1" and "0" by level comparison (comparing) or the like. The output signal from the decoding circuit 5 is taken out via the output terminal 5 _OT . The output from the detection characteristic circuit 13 is taken out from the output terminal 15 _OT via the filter 14 and the decoding circuit 15. The respective data signals from these output terminals 5 _OT and 15 _OT are sent to the above-mentioned signal processing circuit 108 shown in FIG. 6 and the like. The operation on the adaptive filter side including the filter 4 and the adaptive control unit 7, and the filter 14 and the adaptive control unit 17
The operation on the adaptive filter side consisting of is similar to that of the embodiment of FIG.

Next, the stability detection circuit 8 is supplied with the respective output signals from the reproduction amplifier 2, the detection characteristic circuit 3, the digital filter 4, the decoding circuit 5, etc., and stabilizes the signal of the channel on the head 1 side. The state is calculated. The stability detection circuit 18 is supplied with the respective output signals from the reproduction amplifier 12, the detection characteristic circuit 13, the digital filter 14, the decoding circuit 15, etc., and calculates the stable state of the signal of the channel on the head 11 side. Is. The detection output signals from the stability detection circuits 8 and 18 are sent to the comparison circuit 9 and compared with each other to determine whether or not any channel has an abnormality. The output of the determination result or the comparison result is taken out through the output terminal 9 _OT , and for example, the operation is stopped or the alarm lamp is turned on for notifying that an abnormality has occurred.

Here, when there is a reproducing circuit system of a plurality of channels as described above, the abnormality (trouble) of each channel can be detected by using the information such as the signal state between these channels. The reason is as follows. That is, consider a case where some change appears in a stable state. When this change appears only in a specific channel for a long time, the circuit after the head of that channel,
It is considered that troubles such as head clogging and circuit loss occurred. On the other hand, if the same state change appears in all the channels, it is unlikely that troubles will occur in a plurality of circuits at the same time, and therefore it can be considered that the state change due to the tape has occurred. From this point of view, it is possible to find a trouble for each channel by comparing signals and states between the channels.

As the index of the stable state, not only the signal of the reproduction circuit system but also various information of the adaptive equalization circuit system, for example, the error signal e or Δe, e ² , Δe ² and the correction amount of the tap coefficient. Δw, or the total of multiple taps ΔΣ
It is conceivable to use w, deviation from the average value, or the like.
Therefore, it is possible to determine a trouble during the adaptive equalization. An example of this circuit is shown in FIG.

In FIG. 5, the stability comparison circuit 10
Compares the above-mentioned error signals from the adaptive control circuits 7 and 17, the correction amount of the tap coefficient, and the like between the channels to determine whether the operation is normal. The output signal from the stability comparison circuit 10 is taken out through the output terminal 10 _OT and used to stop the operation or generate an alarm as described above. Note that the other configuration of FIG.
Since the configurations are the same as those in FIG. 4 and FIG. 1 described above, corresponding parts are designated by the same reference numerals, and description thereof will be omitted.

The present invention is not limited to the above-described embodiment, and for example, the specific configuration of the filter 14 and the algorithm used in the adaptive control unit 17 are the same as the FIR filter and the LMS algorithm of the above-mentioned embodiment. Not limited. Further, the applicable equipment is not limited to the digital VTR, and the present invention can be applied to a digital tape recorder, an analog VTR and the like.

[0039]

As is apparent from the above description, according to the magnetic reproducing apparatus of the first invention of the present application, in the magnetic reproducing apparatus for reproducing the magnetic data recorded on the magnetic recording medium, the magnetic head Using an adaptive filter as an equalizer that compensates the characteristics of the reproduced signal from, the input signal or output signal of the adaptive control unit of this adaptive filter is compared with a reference value to determine whether the signal value is appropriate, and the determination result By prohibiting the update of the tap coefficient of the adaptive filter, etc., the adaptive operation of the adaptive filter can be quickly returned to the converged state or the normal state after the end of the variation without being affected by the sudden variation. it can.

Further, according to the magnetic reproducing apparatus of the second invention of the present application, a filter serving as an equalizer for compensating the characteristic of the reproduced signal from the magnetic head, and a decoding circuit for decoding the output signal from this filter are provided. , An adaptive control unit for adaptively adjusting the characteristics of the filter based on an input signal to the filter and an input / output signal to the decoding circuit. By judging whether the operation is normal by comparing the signals of the corresponding parts of the channels with each other, it is possible to detect abnormalities (trouble) such as clogging of the head at an early stage, issue an alarm, etc. Can prompt treatment.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing a schematic configuration of a part of a reproducing system of a digital VTR as an embodiment of a magnetic reproducing apparatus according to the present invention.

FIG. 2 is a block circuit diagram showing a specific example of an internal configuration of an adaptive equalizer (adaptive filter) used in the embodiment.

FIG. 3 is a graph showing how a tap coefficient of an adaptive filter changes with time.

FIG. 4 is a block circuit diagram showing a schematic configuration of a part of a reproducing system of a digital VTR which is another embodiment of the magnetic reproducing apparatus according to the present invention.

FIG. 5 is a block circuit diagram showing a schematic configuration of a part of a reproducing system of a digital VTR which is still another embodiment of the magnetic reproducing apparatus according to the present invention.

FIG. 6 is a block circuit diagram showing a schematic configuration of a reproduction system of a digital VTR used for explaining a conventional technique.

[Explanation of symbols]

 1, 11 ... magnetic head 3, 13 ... detection characteristic circuit 4, 14 ... filter (equalizer) 5, 15 ... decoding circuit (comparator) 6, 16 .... Adder (error detector) 7, 17 ... Adaptive control unit 8, 18 ... Stability detection circuit 9 ... Comparison circuit 10 ... Stability Comparator circuit 31 ... Input value judgment circuit 32 ... Error signal judgment circuit 33 ... Tap coefficient value judgment circuit

Claims (2)

[Claims] 1. A magnetic reproducing apparatus for reproducing magnetic data recorded on a magnetic recording medium, a filter serving as an equalizer for compensating characteristics of a reproduced signal from a magnetic head, and a decoding circuit for decoding an output signal from the filter. An adaptive control unit that adaptively adjusts the characteristics of the filter based on an input signal to the filter and an input / output signal to the decoding circuit, and compares an input signal or an output signal of the adaptive control unit with a reference value. And a determination means for determining whether or not the value of the signal is appropriate. 2. A magnetic reproducing apparatus for reproducing magnetic data recorded on a magnetic recording medium, a filter serving as an equalizer for compensating for characteristics of a reproduced signal from a magnetic head, and a decoding circuit for decoding an output signal from the filter. And at least two channels of a reproduction system including an adaptive control unit that adaptively adjusts the characteristics of the filter based on an input signal to the filter and an input / output signal to the decoding circuit. A magnetic reproducing apparatus, characterized in that it is provided with a comparing means for judging whether or not the operation is normal by comparing the signals of corresponding portions of the respective channels with each other.