JP2002343021A - Reproducing device and equalization parameter setting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately and quickly set an optimum equalization parameter. SOLUTION: In a step [11], a trellis decoder is turned off and the equalization parameter of an analog waveform equalizer is initialized. In a step [12], the equalization parameter is deflected to the initial value and values before and after it to sample the numbers of errors. In a step [13], pieces of error information are compared to determine a climbing direction. In a step [14], the equalization parameter is deflected by one step in the climbing direction. In a step [15], error information is sampled to obtain an evaluation value. In a step [16], the evaluation value is compared with that before change of the equalization parameter. When the evaluation value is smaller (less error), process is returned to the step [14]. When the evaluation value is larger (much error), the equalization parameter before change is taken as the optimum equalization parameter in step [17], and the trellis decoder is turned on in a step [18].

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a reproducing apparatus applied to, for example, a digital magnetic recording / reproducing apparatus and a method of setting an equalization parameter. More specifically, the present invention enables accurate and quick setting of an equalization parameter of an analog waveform equalizer for a signal immediately after reproduction.

[0002]

2. Description of the Related Art For example, in a digital recording / reproducing apparatus, a signal-to-noise ratio is improved by performing trellis encoding on a recording signal sequence during recording and performing trellis decoding on the reproduced signal during reproduction. (See Japanese Patent Application Laid-Open No. 11-186917).
On the other hand, in a digital recording / reproducing apparatus using magnetic recording, for example, before performing a reproducing process using a digital signal,
Analog waveform equalization is performed on a reproduced signal for the purpose of compensating signal characteristics and the like of the recording / reproducing system.

That is, also in a digital reproducing apparatus, a reproduced signal reproduced by, for example, a magnetic head is analog, and the reproduced signal is subjected to A / D conversion and then subjected to digital reproduction processing. Therefore, for example, a clock signal component is extracted from the reproduced signal using a phase synchronization means (PLL), and the A / D is extracted using the extracted clock signal.
Conversion is performed. The clock signal is also used, for example, in digital reproduction processing.

Here, for example, if there is an equalization error in the waveform equalization of the reproduction signal supplied to the phase synchronization means, the jitter component of the extracted clock signal increases and the error rate deteriorates. For this reason, the reproduction signal supplied to the A / D conversion and phase synchronization means is subjected to processing for suppressing an equalization error using an analog waveform equalizer. That is, in such an analog waveform equalizer, the equalization parameter is changed according to the signal characteristics and the like of the recording / reproducing system, and the setting is performed for each device.

[0005]

By the way, the equalization error of the analog waveform equalizer can be basically considered as a random error, and is considered to be equivalent to deteriorating the signal-to-noise ratio of the reproduced signal. Therefore, it is conceivable to detect noise due to such a random error and set an equalization parameter of the analog waveform equalizer so that noise due to the random error is reduced.

However, by performing trellis decoding on the reproduced signal as described above, the noise due to such random errors in the reproduced signal can be improved by about 3 dB in terms of the signal-to-noise ratio in comparison with the so-called Viterbi decoding. It is known to be done. For this reason, in the portion where the signal-to-noise ratio of the original reproduced signal is good, the deterioration of the signal-to-noise ratio due to the above-described equalization error is masked. It becomes difficult for the noise to be detected to reflect the equalization error.

Further, when a magnetic tape is used as a recording medium, a burst error generated due to a protrusion or the like existing on the tape is relatively increased as compared with a random error. It becomes more difficult for an equalization error to be reflected in noise to be detected when setting an equalization parameter of the waveform equalizer. As a result, the control speed of the control when setting the equalization parameter of the analog waveform equalizer described above becomes slow, and it becomes extremely difficult to set the optimum equalization parameter.

The present application has been made in view of the above points, and the problem to be solved is that, in the conventional device, the detection when setting the equalization parameter of the analog waveform equalizer is performed. It is difficult to reflect the equalization error to the noise to be set, and it is difficult to set the optimum equalization parameter accurately and quickly. As a result, it was not possible to prevent the deterioration of the error rate of the system.

[0009]

For this reason, in the present invention, the adaptive digital waveform equalizer and the trellis decoding circuit are made inoperative, and the number of error corrections of the error correction circuit is used as an evaluation value in a state where the adaptive digital waveform equalizer and the trellis decoding circuit are merely a threshold decoder. According to this configuration, the equalization parameter of the analog waveform equalizer is set, and according to this configuration, the noise detected when setting the equalization parameter of the analog waveform equalizer has a good equalization error. And the optimum equalization parameter can be set accurately and quickly.

[0010]

More specifically, the present invention reproduces a trellis-encoded signal, supplies the reproduced signal to a phase synchronizing means through an analog waveform equalizer, and outputs a clock signal phase-synchronized with the reproduced signal. Generating and A / D converting the reproduced signal using the clock signal, and supplying the A / D converted signal to a trellis decoding circuit for trellis encoding through an adaptive digital waveform equalizer; Output signal to the error correction circuit to obtain a reproduction output signal, the adaptive digital waveform equalizer and the trellis decode circuit are disabled, and the error correction circuit error is output in the state of a simple threshold decoder. The equalization parameters of the analog waveform equalizer are set using the number of corrections as an evaluation value.

FIG. 1 is a block diagram showing the configuration of an embodiment of a digital magnetic recording / reproducing apparatus to which a reproducing apparatus and an equalization parameter setting method according to the present invention are applied. It is.

In FIG. 1, a recording signal sequence supplied to an input terminal 10 is supplied to a trellis encoder 11 and trellis encoded. The trellis-encoded recording signal sequence is supplied to the recording head 21 through the recording amplifier 12 and recorded on the magnetic tape 22. Further, the signal recorded on the magnetic tape 22 is reproduced by the reproducing head 23. Then, a reproduction signal reproduced by the reproduction head 23 is taken out through the reproduction amplifier 13.

Further, a reproduction signal (analog signal) from the reproduction amplifier 13 is supplied to an analog waveform equalizer 14 for compensating signal characteristics and the like of the recording / reproduction system. The signal that has passed through the analog waveform equalizer 14 is phase-synchronized (PL
L) 15 and a clock signal component is extracted from the reproduced signal. The signal that has passed through the analog waveform equalizer 14 is supplied to an A / D converter 16, and a clock signal from the phase synchronization unit 15 is supplied to the A / D converter 16 to perform digital conversion of a reproduced signal. .

The digitally converted reproduction signal is supplied to a digital waveform equalizer 17. The signal passed through the digital waveform equalizer 17 is converted to a trellis decoder 18.
To perform trellis decoding. Further, a signal from the trellis decoder 18 is supplied to an error correction circuit 19 using an arbitrary error correction code or the like. As a result, the error correction circuit 19 detects and corrects errors in the supplied reproduction signal, and restores the original recording signal sequence.

At the same time, for example, at the time of factory shipment,
The number of error corrections in the error correction circuit 19 is used as error information as a control microcomputer (CPU) 20.
Supplied to As a result, the microcomputer 20 sets the equalization parameters for the analog waveform equalizer 14 using the error information from the error correction circuit 19 as an evaluation value. That is, this adjustment is performed in the microcomputer 20 according to, for example, the following flowcharts shown in FIGS.

First, FIG. 2 shows the flow of the entire processing. When the processing is started, a signal is recorded in step [1], and reproduction is started. Then, in step [2], the tap coefficients of the digital waveform equalizer 17 are initialized, and in step [3], automatic adjustment of the equalization parameters for the analog waveform equalizer 14 is performed. As a result, the equalization parameters for the analog waveform equalizer 14 are set, and the tap coefficients of the digital waveform equalizer 17 are automatically adjusted in step [4], and the process is stopped.

FIG. 3 shows an algorithm for automatic adjustment by so-called hill-climbing control. When the processing is started in FIG. 3, the trellis decoder 18 is turned off in step [11] to make a simple threshold decoder, and the analog waveform equalizer 1
Four equalization parameters are initialized. Next, step [1
In 2], the number of errors is sampled by assigning an equalization parameter before and after the initial value. Then, in step [13], the three pieces of error information are compared, and the direction in which the error information is small is set as the hill-climbing direction.

In step [14], the equalization parameter is shifted by one step in the above-mentioned hill-climbing direction. Then, in step [15], the error information in that state is sampled to determine an evaluation value. Further, the determined evaluation value is compared with the evaluation value before the change of the equalization parameter in step [16]. If the evaluation value is small (the number of errors is small) in step [16], step [1]
4] and the operations of steps [14] to [16] are repeated.

If the evaluation value is large (there are many errors) in step [16], the equalization parameter before the change is made the optimum equalization parameter in step [17]. Then, in step [18], the trellis decoder 18 is turned on and the processing is stopped. In this way, the equalization parameter when the evaluation value is the smallest (the error is the smallest) is determined as the optimal equalization parameter, and the automatic adjustment of the equalization parameter for the analog waveform equalizer 14 is performed.

In the above-described embodiment, the situation of the number of errors with respect to the change of the equalization parameter when the trellis decoder 18 is turned on is as shown in FIG. 4A. On the other hand, the situation of the number of errors with respect to the change of the equalization parameter when the trellis decoder 18 is turned off is as shown in FIG. 4B, and the number of errors changes with the change of the equalization parameter. Automatic adjustment of the equalization parameter for the analog waveform equalizer 14 is accurate,
And it is done quickly.

Accordingly, in this embodiment, the adaptive digital waveform equalizer and the trellis decoding circuit are made inoperable, and the number of error corrections of the error correction circuit is evaluated as an evaluation value in a state of a simple threshold decoder. By performing the setting of the equalization parameter, the equalization error is satisfactorily reflected in the noise detected when the equalization parameter of the analog waveform equalizer is set, and the optimum equalization parameter can be accurately and quickly determined. Can be set to

As a result, in the conventional apparatus, it is difficult for the noise to be detected when setting the equalization parameter of the analog waveform equalizer to reflect the equalization error, and the optimum equalization parameter can be accurately and promptly determined. It is difficult to set, and as a result, a signal having a large equalization error is supplied to the phase synchronization means and the like, and the deterioration of the error rate of the system cannot be prevented. According to this, these problems can be easily solved.

Thus, according to the above-described reproducing apparatus, the trellis-encoded signal is reproduced, and the reproduced signal is supplied to the phase synchronizing means through the analog waveform equalizer, and the clock signal phase-synchronized with the reproduced signal is obtained. A / D conversion is performed on the reproduced signal using the clock signal, and the A / D converted signal is supplied to a trellis decoding circuit for trellis encoding through an adaptive digital waveform equalizer. A reproduction device for supplying a reproduced output signal to the error correction circuit to obtain a reproduced output signal, wherein the adaptive digital waveform equalizer and the trellis decoding circuit are disabled, and the error correction circuit operates as a simple threshold decoder. By setting the equalization parameters of the analog waveform equalizer using the number of corrections as the evaluation value, The setting of the Do equalization parameter accurately, those that can and quickly perform it.

Further, according to the above-described method for setting the equalization parameters, the trellis-encoded signal is reproduced, and the reproduced signal is supplied to the phase synchronization means through an analog waveform equalizer, and the reproduced signal is phase-shifted. Along with generating a synchronized clock signal, A / D conversion of the reproduced signal is performed using the clock signal, and the A / D converted signal is supplied to a trellis decoding circuit for trellis encoding through an adaptive digital waveform equalizer. Then, the adaptive digital waveform equalizer and the trellis decoding circuit are disabled for the reproducing apparatus that supplies the output signal of the trellis decoding circuit to the error correction circuit and obtains a reproduction output signal, and the state is changed to a mere threshold decoder. Sets the equalization parameter of the analog waveform equalizer using the number of error corrections of the error correction circuit as the evaluation value. And the one in which the setting of the optimum equalization parameters accurate, can be carried out and quickly.

The present invention is not limited to the above-described embodiment, but can be variously modified without departing from the spirit of the present invention.

[0026]

Therefore, according to the first aspect of the present invention, the adaptive digital waveform equalizer and the trellis decoding circuit are made inoperative, and the number of error corrections of the error correction circuit is evaluated as an evaluation value in the state of a simple threshold decoder. By performing the setting of the equalization parameter of the waveform equalizer, the equalization error is favorably reflected in the noise detected when setting the equalization parameter of the analog waveform equalizer,
An optimum equalization parameter can be set accurately and quickly.

According to the second aspect of the present invention, the setting of the equalization parameter of the analog waveform equalizer is performed by automatic adjustment by hill-climbing control by a built-in microcomputer, so that the optimum equalization parameter is set. Can be set accurately and quickly.

According to the third aspect of the present invention, the adaptive digital waveform equalizer and the trellis decoding circuit are made inoperable, and a simple threshold decoder is used. By setting the equalizer parameters of the equalizer, the equalization error is favorably reflected in the noise detected when setting the equalizer parameters of the analog waveform equalizer. It can be set accurately and quickly.

According to the fourth aspect of the present invention, the setting of the equalization parameter of the analog waveform equalizer is performed by automatic adjustment by hill-climbing control by a built-in microcomputer, so that the optimum equalization parameter is set. Can be set accurately and quickly.

As a result, in the conventional apparatus, it is difficult for the equalization error to be reflected in the noise to be detected when setting the equalization parameter of the analog waveform equalizer, and the optimum equalization parameter can be accurately and quickly determined. It is difficult to set, and as a result, a signal having a large equalization error is supplied to the phase synchronization means and the like, and it is not possible to prevent the deterioration of the system error rate. According to this, these problems can be easily solved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a digital magnetic recording / reproducing apparatus to which a reproducing apparatus and a method for setting an equalization parameter according to the present invention are applied.

FIG. 2 is a flowchart for explaining the operation.

FIG. 3 is a flowchart for explaining the operation.

FIG. 4 is a diagram for the explanation.

[Explanation of symbols]

10 input terminal, 11 trellis encoder, 12
Recording amplifier, 13: reproduction amplifier, 14: analog waveform equalizer, 15: phase synchronization means (PLL), 16: A / D converter, 17: digital waveform equalizer, 18: trellis decoder, 19: error correction Circuit, 20: microcomputer (CPU), 21: recording head, 22: magnetic tape, 23: reproducing head

Claims (4)

[Claims] 1. A trellis-encoded signal is reproduced, and the reproduced signal is supplied to phase synchronization means through an analog waveform equalizer to generate a clock signal phase-synchronized with the reproduced signal. A / D of the reproduced signal using a clock signal
Performing a conversion, supplying the A / D-converted signal to a trellis decoding circuit for the trellis encoding through an adaptive digital waveform equalizer, supplying an output signal of the trellis decoding circuit to an error correction circuit, and outputting a reproduced output signal. Wherein the adaptive digital waveform equalizer and the trellis decoding circuit are disabled, and the analog waveform equalization is performed using the number of error corrections of the error correction circuit as an evaluation value in a state of a simple threshold decoder. A reproduction apparatus for setting equalization parameters of a device. 2. The reproducing apparatus according to claim 1, wherein the setting of the equalization parameter of the analog waveform equalizer is performed by automatic adjustment by hill-climbing control by a built-in microcomputer. 3. Regenerating a trellis-encoded signal, supplying the reproduced signal to a phase synchronization means through an analog waveform equalizer, and generating a clock signal phase-synchronized with the reproduced signal; A / D of the reproduced signal using a clock signal
Performing a conversion, supplying the A / D-converted signal to a trellis decoding circuit for the trellis encoding through an adaptive digital waveform equalizer, supplying an output signal of the trellis decoding circuit to an error correction circuit, and outputting a reproduced output signal. For the reproducing apparatus that obtains the above, the adaptive digital waveform equalizer and the trellis decoding circuit are made inoperable, and the analog waveform equalization is performed using the number of error corrections of the error correction circuit as an evaluation value in a state of a simple threshold decoder. A method for setting an equalization parameter, comprising setting an equalization parameter of a vessel. 4. The method of setting an equalization parameter according to claim 3, wherein the setting of the equalization parameter of the analog waveform equalizer is performed by automatic adjustment by hill-climbing control by a built-in microcomputer.