JPH04355268A - Recording and reproducing method for magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To avoid the increase of a state in a demodulator by obtaining a binarized state as same as a hardening state at the time of demodulating a recording signal, in a partial response system recording and reproducing system. CONSTITUTION:In a storage system, precording minimizing the propagation of a data error is performed by means of a precorder 21. By means of an NRZI recorder 22, an NRZI recording reversing the direction of recording current when data are '1' is conducted, and the data are recorded in a state magnetizing them on a magnetic recording medium. In a reproducing system, a differential detector 23 using a magnetic head detects voltage proportional to a change dphi/dt of a flux and an equalizer 24 performs equalizing. The data are converted into digital values by a data converter 25 provided with a sampling circuit and an A/D converter. Another calculator 26 performs the calculation processing of the digital data and the obtained data are demodulated by a demodulator 27.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording and reproducing method for a magnetic recording and reproducing apparatus, and more particularly to a recording and reproducing method for a magnetic recording and reproducing apparatus using partial response. As computer systems become faster, magnetic disk devices serving as external storage devices are also required to have faster speeds and larger capacities. For this reason, the frequency of the signals handled by the demodulation circuit of the magnetic disk device increases, the recording density (BPI) on the medium increases, and the signal quality deteriorates. When demodulating such degraded signals, it is becoming difficult to achieve highly reliable demodulation using conventional peak detection.

As an effective method for demodulating a reproduced signal from a magnetic recording/reproducing device, a partial response method has been known for a long time, in which a reproduced signal to which controlled waveform interference is added is sampled at a bit rate and demodulated. As a demodulation method of this partial response method, there are, for example, the following documents. (1) E. R. Kretzmer. ”Genera
lization of a Technique f
or Binary DataCommunication
on”, IEEE Trans. Comm. Te
Ch. COM-14, pp. 67-68 (19
66) (2) H. Kobayashi and D.
T. Tang, “Application of P
artial ResponseChannelCo
ding to magnetic recordin
g systems”IBM J. Res. Dev
elopment. , 14, NO. 4, pp.
368-375, (1970) However, there is no effective method of demodulating a reproduced signal from magnetic recording and reproduction using this partial response method, and its realization has been desired.

0003

2. Description of the Related Art FIG. 4 shows the configuration of a recording system and a reproducing system in a magnetic disk device using a conventional partial response method. In the recording system, first, a precoder 41 is used to perform precoding on data to minimize error propagation, and then data "1" is precoded.
Perform NRZI recording in which the direction of the recording current is reversed,
Information is recorded on a magnetic recording medium in a magnetized state.

This precoding is performed using a precoder 53 consisting of an equivalent circuit as shown in FIG. 5(c). This precoder 53 includes an exclusive OR operation circuit 531 that takes an exclusive OR of two inputs, and an exclusive OR operation circuit 531 that takes an exclusive OR of two inputs.
It is equipped with a delay circuit 532 that delays the sample.
The recording data is input to one input of the exclusive OR operation circuit 531, and the output of the exclusive OR operation circuit 531 is input to the other input via a delay circuit 532. It is.

When the delay amount of the delay circuit 532 is D,
The signal calculation in this precoder 53 is 1/(1+D
) can be expressed as On the other hand, the process of recording precoded signals in a magnetized state on a magnetic recording medium by the aforementioned NRZI recording involves inputting data to an exclusive OR operation circuit 541 as shown in FIG. 5(d). This is equivalent to processing through the arithmetic circuit 54 combined with the delay circuit 542 that delays the data by one sample, and can be expressed as an operation of 1/(1-D).

On the other hand, in the reproducing system, a magnetic head is used to detect a voltage proportional to the change in magnetic flux dφ/dt. This is differential detection, and is equivalent to processing through an arithmetic circuit that is a combination of an exclusive OR arithmetic circuit 521 and a delay circuit 522 that delays the input by one sample of data, as shown in FIG. 5(b). It can be regarded as an operation of (1-D). Conventionally, an exclusive OR operation circuit 5 as shown in FIG.
11 and a delay circuit 512 that delays the input by one sample of data performs the calculation of (1+D), and after performing the calculation equivalent to (I-D2) in total, the signal is sampled. After that, A/D conversion was performed to obtain three-value data of 0, +1, and -1. This ternary data was demodulated by a ternary data demodulation circuit as shown in FIG. 6, which had already been proposed by the present inventors (see Japanese Patent Application No. 2-246072).

[0007]

However, in the conventional demodulation method, the three-value state of 0, +1, and -1 can be taken after A/D conversion after sampling. For this reason,
An increase in the number of states can be avoided by using a demodulator that determines the states of multiple samples as shown in Figure 6, estimates the state to be demodulated from the transition of these states, and outputs demodulated data based on this. The problem is that there is no.

[0008] Accordingly, the present invention, in a partial response recording/reproducing method, obtains the same binary state as the magnetization state when demodulating the recorded signal, thereby avoiding an increase in the number of states in the demodulator. It is an object of the present invention to provide a recording and reproducing method for a magnetic recording and reproducing device.

[0009]

[Means for Solving the Problems] The basic configuration of the demodulation method of the present invention that achieves the above object is shown in FIG. As shown in this figure, the present invention includes a positive input into which recording data is input, and a negative input into which the output is delayed by a delay element having a delay time of one period of data. Data processing step 1 involves precoding recording data using a circuit that outputs the exclusive OR operation result of two input signals, or a circuit having the same function as the circuit, and the obtained processed data is processed into NRZI recording. a data recording step 2 in which recorded data is recorded on a magnetic recording medium using a method, a data reading step 3 in which recorded data is read out using a magnetic head from the magnetic recording medium recorded in steps 1 and 2, and the read signal and its An equalization stage 4 performs equalization processing for a class 4 partial response, which can be expressed as a function of adding a signal to a delayed signal passed through a delay element having a delay time of one data cycle, and this equalization stage a data conversion stage 5 which samples the obtained signal at intervals equal to one data period and outputs a three-value digital signal of 1, 0, -1 according to the sample value; Arithmetic step 6, in which arithmetic processing equivalent to exclusive ORing with a signal delayed by a delay element with a delay time of two periods of data is performed to obtain a binary signal equal to the magnetization state of the recorded data. and the signal obtained in the calculation step 6, and a signal obtained by delaying this signal by a delay element having a delay time equivalent to two periods of data similar to the above. This is a partial response type recording and reproducing method characterized by comprising a data demodulation stage 7 in which demodulated data is obtained by performing the following steps.

0010

[Operation] According to the present invention, since the input to the demodulator becomes a binary signal corresponding to the magnetization state on the magnetic recording medium, the number of states to be considered during demodulation is smaller than in the case of three values.
It is possible to reduce the amount of hardware and to speed up the operation accordingly.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 2 shows a recording system in a magnetic disk device using a partial response method according to an embodiment of the present invention.
This shows the configuration of the reproduction system. In the recording system, first, a precoder 21 is used to perform precoding to minimize data error propagation, and then NRZI
Using the recorder 22, NRZI recording is performed in which the direction of the recording current is reversed at data "1", and data is recorded in a magnetized state on the magnetic recording medium.

This precoding is performed using a precoder 53 as shown in FIG. 5(c). This precoder 53 includes an exclusive OR operation circuit 531 that takes the exclusive OR of two inputs, and a delay circuit 532 that delays the input by one sample of data. Recording data is input to one input, and the output of the exclusive OR operation circuit 531 is input to the other input via a delay circuit 532.

When the delay amount of the delay circuit 532 is D,
The signal calculation in this precoder 53 is 1/(1+D
) can be expressed as On the other hand, the process of recording precoded signals in a magnetized state on a magnetic recording medium by the above-mentioned NRZI recording involves inputting data to the exclusive OR operation circuit 541 shown in FIG. 5(d). An arithmetic circuit 54 combined with a delay circuit 542 that delays by one sample.
It is equivalent to processing through , and is an operation of 1/(1-D).

Next, the reproduction system will be explained. In the reproduction system, first, a differential detector 23 using a magnetic head detects a voltage proportional to the change in magnetic flux dφ/dt, and an equalizer 24
After that, the sampling circuit and A/
A data converter 25 including a D converter converts the data into digital values. Then, another arithmetic unit 26 performs arithmetic processing on the digital data, and the obtained data is demodulated using a demodulator 27 to obtain demodulated data.

The processing by the differential detector 23 described above is shown in FIG.
It is equivalent to processing through the arithmetic circuit 52 that is a combination of the exclusive OR arithmetic circuit 521 shown in (b) and the delay circuit 522 that delays the input by one sample of data.
) is calculated. The processing by the equalizer 24 is carried out by the exclusive OR operation circuit 5 shown in FIG.
11 and a delay circuit 512 that delays the input by one sample of data.
2) It is equivalent to performing a corresponding calculation. The processing by the data converter 25 involves sampling the signal obtained by the equalizer 24, and then A/D converting it to 0, +1, -1.
This is the process of obtaining 3-value data.

In the present invention, the arithmetic unit 26 calculates 1/(1-D2) for this three-value data of 0, +1, -1.
This is done using This arithmetic unit 26 includes an equalization circuit 51 in which a delay circuit 512 is inserted in a closed loop connecting the output and negative input of an exclusive OR circuit 511 having two positive and negative inputs shown in FIG. 5(a); An arithmetic circuit 52 in which a delay circuit 522 is inserted in a closed loop connecting the output of an exclusive OR circuit 521 having two positive inputs and one positive input shown in FIG. 5(b).
It may be configured from a series circuit with. With this operation,
The three-value data of 0, +1, and -1 is converted into binary data of -1 and +1, which are equal to the magnetization state of the recorded data.

The above process will be specifically explained using FIG. 3. For example, a data string written to a magnetic recording/reproducing device is
A case where it is "...00111010000..." as shown in FIG. 3(a) will be explained. As described above, the data is subjected to 1/1+D processing by the precoder circuit shown in FIG. 5(c), and the exclusive OR of the current data and the previous precoder output is taken. As a result, the precoder output becomes "...00101100000..." as shown in FIG. 3(b). When this precoder output is recorded in the form of magnetization on a magnetic recording medium by NRZI recording, it becomes as shown in FIG. 3(c). The above is the processing performed by the recording system shown in FIG.

Next, when the track of the magnetic recording medium is traced using a magnetic head, the magnetization state changes according to the change in magnetic flux dφ
The signal is reproduced as a voltage proportional to /dt as shown in FIG. 3(d). When this reproduced signal is subjected to 1+D equalization by the circuit shown in FIG. 5(a), the reproduced signal becomes
) is the waveform shown. When the waveform shown in FIG. 3(e) is sampled at predetermined intervals and the peak value at the time of sampling is A/D converted, the amplitude at the time of sampling is 0, -1, +1, as shown in FIG. 3(f). It is obtained as a three-value signal.

According to the present invention, the circuits shown in FIGS.
/[1-D2] Perform the operation. When this calculation is performed, the three-value signal 0, -1, +1 can be expressed as a binary signal -1 and +1, and as shown in Figure 3(g), the same magnetization state as in Figure 3(c) is obtained. Can be reproduced. Therefore, if this binary data is demodulated by the demodulator at the next stage, demodulated data shown in FIG. 3(h) can be output.

This demodulation method was developed by the inventors in patent application No.
It is sufficient to use the method proposed in No. 246072, and this method is a sequential demodulation method in which recorded data is demodulated from a reproduced signal from a recording medium on which "1" and "0" signals are recorded using a predetermined method. , positive and negative peaks always appear alternately in the reproduced signal. In this demodulation method, all states that can be taken by N consecutive sample values at the same interval as the data cycle of recorded data are set in advance as a pattern by using the regularity that appears in the reproduced signal. Next, in order to compare the N sample values with all possible state patterns, the reproduced signal is sampled at the same interval as the data period of the recorded data, and N consecutive sample values are collected.

At this time, in order to increase reliability, in one embodiment, among the N consecutive sample values in the reproduced signal to be successively compared with a preset pattern, the current N sample values and M out of the previous N samples (M<
N) overlap. Then, the data demodulated using the current N sample values and the M data in the overlapped portion of the data demodulated using the previous N samples are compared, and if they do not match, an error signal is output.

[0022] After that, the mutual magnitude relationship between the N consecutive sample values in the reproduced signal is compared, and it is sequentially determined which of the preset patterns the N consecutive sample groups are most similar to. Then, the most similar state of the existing pattern is output as a "next state" state determination signal while taking into consideration the overlap data. Then, estimation is performed using the state determination result of this "next state" and the previous step, and after a one-step delay, the "previous state" is calculated at the current step.
Based on the two states, the "current state" of the N samples that are currently demodulated is estimated according to the estimation rule, and the estimated current state is output as demodulated data.

[0023] In this state determination, it is only necessary to determine which of all possible binary patterns the pattern is most similar to, so the number of existing patterns can be reduced compared to the method using three values.

[0024]

[Effects of the Invention] As explained above, according to the present invention,
In the partial response recording and reproducing method, since the same binary state as the magnetization state is obtained when demodulating the recorded signal, an increase in the number of states in the demodulator can be avoided.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle configuration of a recording and reproducing method of a magnetic recording and reproducing apparatus according to the present invention.

FIG. 2 is a configuration diagram showing the configuration of a recording system and a reproducing system that implement the recording and reproducing method of the magnetic recording and reproducing apparatus of the present invention.

FIG. 3 is an operation explanatory diagram showing a specific operation of the configuration of FIG. 2;

FIG. 4 is a configuration diagram showing a demodulation system using a conventional partial response method.

FIG. 5 is a block circuit diagram showing the configuration of an arithmetic circuit used for recording and reproducing using the partial response method.

FIG. 6 is a block circuit diagram showing a configuration example of a digital data demodulation system.

[Explanation of symbols]

21...Precoder 22...NRZI recorder 23...Differential detector 24...Equalizer 25...Data converter 26... Arithmetic unit 27...Demodulator 51-54... Arithmetic circuit

Claims (2)

[Claims] [Claim 1] A partial response recording and reproducing method used in a magnetic recording system, wherein the output is delayed by a positive input into which recording data is input and a delay element having a delay time of one cycle of data. A data processing step (1) in which recording data is precoded using a circuit that is provided with a negative input and that outputs the result of an exclusive OR operation of two input signals, or a circuit that has a function equivalent to the circuit. ), a data recording step (2) in which the obtained processed data is recorded on a magnetic recording medium using the NRZI recording method, and a magnetic head is used to extract the recorded data from the magnetic recording medium recorded in steps (1, 2). The data read stage (
3) and the equalization process for class 4 partial response, which can be expressed as the sum of the read signal and the delayed signal passed through a delay element with a delay time of one data cycle. The equalization step (4) is performed, and the signal obtained by this equalization step is sampled at intervals equal to one data cycle, and the sample value is (1, 0, -1).
A data conversion stage (5
), the digital signal, and a signal delayed by a delay element having a delay time of two periods of data are subjected to arithmetic processing equivalent to exclusive ORing of the digital signal and a signal delayed by a delay element having a delay time of two periods of data, and magnetization of the recorded data is performed. an arithmetic step (6) for obtaining a binary signal equal to the state; the signal obtained in the arithmetic step (6) and this signal are delayed by a delay element having a delay time equivalent to two periods of data similar to the above; A recording and reproducing method for a magnetic recording and reproducing apparatus, comprising a data demodulation step (7) in which demodulated data is obtained by performing arithmetic processing equivalent to calculating an exclusive OR with a signal obtained by using a magnetic recording and reproducing apparatus. 2. In the arithmetic step, arithmetic processing equivalent to exclusive ORing of the digital signal with a signal delayed by a delay element having a delay time equivalent to two periods of the same data is performed, Claim 1 characterized in that demodulation is performed by estimating the transition of the magnetization state after obtaining (+1, -1) or (1, 0) information corresponding to the magnetization state on the magnetic recording medium. Demodulation method described in.