JPH06162666A - Magnetic recording/reproduction device - Google Patents

Abstract

(57) [Summary] [Purpose] Using multi-valued amplitude phase modulation,
Magnetism that enables a low error rate for nonlinear distortion, etc.
An air recording / reproducing device is provided. [Structure] Input an M-bit digital signal sequence to N
Bit conversion circuit 3 for converting a bit digital signal sequence
And 2 corresponding to the N-bit digital signal sequence ^NBelief
The point is far from the origin on the constellation plane.
A signal point with a larger
Mapping circuit that outputs two systems of signals that represent the position of the signal point
Directly quadrature-modulates the path 5 and the signals of the two systems using the carrier wave.
The bias signal is superimposed on the quadrature modulated signal with the cross modulation circuit 6.
The bias adding circuit 8 for folding and the reproduction signal reproduced from the reproduction signal.
Demodulator 17 that demodulates with a raw carrier and the demodulation signal from demodulator 17
Decoder 19 which decodes the signal and outputs the decoded digital signal
Composed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus for digital recording such as a digital video tape recorder.

[0002]

2. Description of the Related Art In a conventional magnetic recording / reproducing apparatus for performing digital recording, normally, an NRZI modulation system or 8-10 is used.
A baseband recording modulation method such as a conversion method is used (for example, "High Density Magnetic Recording Technology Used for Digital VTR", Shozo Nakagawa, Journal of Television Society 3rd.
Volume 5, No. 7 (1981) ", pages 542-548). Further, a multilevel digital modulation method such as multilevel amplitude phase modulation may be used for the purpose of high density recording (for example,
1988 IEICE Spring National Convention C-59).

In a magnetic recording / reproducing apparatus using multi-level amplitude / phase modulation, the signal point arrangement is, for example, four-valued as shown in FIG. 14 and eight-valued as shown in FIG. When the signal point arrangement is 16-valued, the signal point arrangement as shown in FIG. 16 is used. Modulation methods using these three types of signal point constellations are four-level phase modulation (QPS).
K), 8-level phase modulation (8PSK), and 16-level quadrature amplitude modulation (16QAM) (for example, Masayoshi Murotani, Heiichi Yamamoto: "Digital Radio Communication", Industrial Books, Showa 6).
0).

[0004]

However, when a multilevel amplitude phase modulation signal is recorded, the distribution of the signal points of the reproduced demodulation signal has a large variation as shown in FIG. 17 corresponding to the reference signal point farther from the origin. Become. The radius of the circle shown by the dotted line in FIG. 17 represents the standard deviation of the distance distribution between each reference signal point and the signal point of the corresponding reproduction demodulation signal. For example, the reproduction demodulation signal corresponding to the reference signal point whose distance from the origin is r1. It shows that the standard deviation of the distance distribution with the signal point of is σ ₁ ,
Generally, if r ₁ <r ₂ <r _3, then σ ₁ <σ ₂ <σ ₃ .

This is due to the phase shift of the reproduced carrier wave due to the jitter, the envelope fluctuation of the reproduced signal, or the non-linear distortion in the magnetic recording / reproducing process. Therefore the same SN
The error rate is increased as compared with the case of decoding a reproduced demodulated signal with uniform variation regardless of the distance from the origin.

In view of the above problems, according to the present invention, even if the signal point distribution of the demodulated signal corresponds to the reference signal farther from the origin, the variation of the signal points becomes larger, but the farther the reference signal point is from the origin, the greater the signal. It is an object of the present invention to provide a magnetic recording / reproducing apparatus which can obtain a decoded digital signal with a low error rate by arranging so that the point spacing becomes large.

[0007]

In order to achieve the above object, a magnetic recording / reproducing apparatus of the present invention uses an input M-bit digital signal sequence as an N-bit (N is an integer of 2 or more) digital signal sequence. Instead of arranging the bit number conversion circuit for converting into N and the 2 ^N signal points corresponding to the N-bit digital signal string at equal intervals on the constellation plane, the signal points farther from the origin are more The signal point position is represented such that the distance between the signal point and the other signal point is smaller, and the distance between the signal point and the other signal point is smaller.
A mapping circuit that outputs a system signal, a quadrature modulation circuit that quadrature modulates the signals of the two systems using a carrier from a carrier generation circuit and outputs a modulated signal, and a recording signal that is an output of the quadrature modulation circuit. A bias applying unit for superimposing a bias signal having a frequency higher than twice the highest frequency of the recording signal, and magnetic recording / reproducing for recording and reproducing the bias-added recording signal on a magnetic recording medium via a magnetic head. Section, a carrier wave reproducing circuit for reproducing a carrier wave from a reproduction signal reproduced through the magnetic head in the magnetic recording / reproducing section, a demodulator for demodulating the reproduction signal with the reproduction carrier wave, and a demodulation signal from the demodulator And a decoder for decoding and outputting as a decoded digital signal.

[0008]

According to the present invention, the signal of the reproduced demodulated signal on the constellation plane is obtained by the above-mentioned structure due to the influence of the jitter or the envelope fluctuation contained in the reproduced signal in the multi-level amplitude phase modulation or the non-linear distortion in the magnetic recording / reproducing process. Even if the signal points whose distance from the origin is farther from the origin have larger variations, the signal points are arranged in advance to allow them, so the error occurrence frequency of decoded data at the reference point far from the origin is suppressed. The overall error rate is reduced.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic recording / reproducing apparatus according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a magnetic recording / reproducing apparatus of a first embodiment of the present invention.

First, in the first embodiment shown in FIG.
An M-bit digital signal sequence 210 is input from the input terminal 2. The bit number conversion circuit 3 converts the number of bits of the digital signal sequence 210 into a 3-bit digital signal sequence 310. Next, the bit-converted 3-bit digital signal string 310 is input to the mapping circuit 5,
A signal point represented by a 3-bit signal 310 is arranged on the constellation plane. 2 based on this signal point arrangement
The I signal 510 and the Q signal 520 of the system are output from the mapping circuit 5.

Now, the configuration of the mapping circuit 5 used in this embodiment and the arrangement of signal points in the mapping circuit 5 will be described. First, the mapping circuit 5 is a ROM (READ ONLY ME
MORY) and other memory elements
Position data on the constellation plane of eight signal points represented by a 3-bit digital signal is written in the OM memory, and when the 3-bit digital signal output from the bit conversion circuit 3 is input, The position data of the reference signal point on the constellation plane represented by a 3-bit digital signal is read from the memory, and two corresponding I and Q signals are output.

Next, an example of signal point arrangement in the mapping circuit 5 is shown in FIG. In FIG. 8, one of the eight signal points is the origin of the constellation plane and the other seven points are approximately 36 on the concentric circle.
In this example, they are arranged at regular intervals of 0/7 degrees.

Here, the points on the concentric circles may be separated by equal angles and arranged on the concentric circles, or they may be slightly deviated from the equal angles. For example, when the error rate of the decoded data between the signal points 2 and 3, 6 and 7 must be particularly reduced, the signal point distance between the signal points 2 and 3, 6 and 7 should be set large. It is also possible to arrange seven signal points on the concentric circles, and in consideration of the signal points with a high error frequency, the signal points on the concentric circles are not always arranged at equal intervals.

Further, when the variation of the signal point distribution near the origin is extremely smaller than the variation of the signal point distribution near the concentric circle, the signal points inside the concentric circle as in the embodiment shown in FIG. It is also possible to reduce the number of signal points on the concentric circles with large signal point variation by increasing the number of.

Further, in addition to the embodiments of FIGS. 8 and 9, when there are two signal points inside the concentric circles, there is FIG. 10 as one embodiment of the signal point arrangement. In this signal point arrangement, the signal points 1 and 2 are brought close to the arrow direction (the constellation plane origin direction) up to the allowable range of the error rate of the decoded data due to the signal point variation at the two internal points, and the signal points 4, 5 on the concentric circles,
It is also possible to move 7 and 8 further in the direction of the arrow to arrange them, and again, the signal points on the concentric circles are not necessarily arranged at equal intervals, and the signal points are moved according to the conditions as described above. You can let me do it. It is possible that

The arrangement of signal points in the mapping circuit 5 has been described above with reference to the embodiments shown in FIGS. 8, 9 and 10, but the arrangement of these signal points is normally 8-level phase modulation (8PSK). In FIG. 15, eight signal points are arranged on a concentric circle so that the amplitude level of each signal point is constant as shown in FIG. 15, whereas by increasing the signal points near the origin within the concentric circle, This is a large interval at signal points far from the origin on the constellation plane. As a result, at the time of decoding, the signal point variation at the reference signal point far from the origin of the constellation plane is allowed,
The error rate of decoded data at a reference point far from the origin can be reduced.

The output I signal 510 and Q signal 520 from the mapping circuit 5 obtained as described above are input to the quadrature modulation circuit 6 and quadrature modulated by the carrier wave 71 from the carrier wave generation circuit 7 in FIG. It Where I signal 51
The 0 and Q signals 520 are amplitude-modulated by the carrier 71 and the carrier 71 and a 90-degree phase carrier 301 having a 90-degree phase difference from each other in the quadrature modulation circuit shown in FIG.

The modulated signal 61 is input to the burst signal addition circuit 8, and the burst signal addition circuit 8 partially adds a burst signal having the same frequency and the same phase as the carrier wave 71 to the modulated signal as shown in FIG. It Further, the burst signal adding circuit output 81 superimposes the bias signal 91 from the bias signal generating circuit 9 in the bias signal adding unit 10 in order to make the magnetic recording / reproducing process close to linear, and the magnetic recording medium 13 passes through the magnetic head 12. Will be recorded. The signal recorded on the magnetic recording medium 13 is reproduced by the magnetic head 14.

The carrier signal reproducing circuit 18 reproduces a continuous reproduced carrier wave 181 from the burst signal included in the reproduced signal 151 reproduced through the magnetic head 14, and the reproduced signal 151 is reproduced using the reproduced carrier wave 181 shown in FIG. The demodulator 17 shown in FIG. Then, the two demodulated I signal 171 and Q signal 172 from the demodulator 17 are decoded by the decoder 19 and the 3-bit decoded digital signal 191 is output terminal 2
Output from 0.

A second embodiment of the present invention will be described below with reference to the drawings. In the second embodiment shown in FIG. 2, the M-bit digital signal sequence 210 is input from the input terminal 2. The bit number conversion circuit 3 converts the number of bits of the digital signal sequence 210 into a 3-bit digital signal sequence 310.

The bit-converted 3-bit digital signal string 310 is input to the mapping circuit 5, and the signal points represented by the 3-bit signal 310 are arranged on the constellation plane. Based on this signal point arrangement, two systems of I signal 510 and Q signal 520 are output from the mapping circuit 5.

Here, the mapping circuit 5 is composed of a storage element such as a ROM, and the position data on the constellation plane of 8 signal points represented by a 3-bit digital signal are written in the ROM in advance,
When a 3-bit digital signal, which is the output of the bit conversion circuit, is input, the position data of the reference signal point on the constellation plane represented by the 3-bit digital signal is read from the memory, and the two systems of I corresponding thereto are read. It outputs a signal and a Q signal.

Further, as the signal point arrangement in the mapping circuit 5, there are those shown in FIGS. 8, 9 and 10 mentioned in the first embodiment.

Next, in FIG. 2, the output I signal 510 and Q signal 520 from the mapping circuit 5 are input to the orthogonal modulation circuit 6 and are orthogonally modulated by the carrier wave 71 from the carrier wave generation circuit 7. Here, the I signal 510 and the Q signal 520 are
Carrier wave 71 and carrier wave 7 in the quadrature modulation circuit shown in FIG.
Amplitude-modulated by 90-degree phase carrier waves 301 having different phases from 1 and 90 degrees, and added to form a modulated signal 61.

Further, the modulated signal 61 is added by the adder 22 with the pilot signal 211 obtained by converting the frequency of the carrier wave 71 from the carrier wave generation circuit 7 by the frequency conversion circuit 21. Then, the adder output 221 superimposes the bias signal 91 from the bias signal generating circuit 9 in the bias signal adding section 10 in order to make the magnetic recording / reproducing process close to linear, and is recorded on the magnetic recording medium 13 via the magnetic head 12. It

The signal recorded on the magnetic recording medium 13 is reproduced by the magnetic head 14. The reproduced modulation signal 141 is a bandpass filter circuit (BPF circuit) 15 for extracting only the modulated signal 151 and a lowpass filter circuit (LPF circuit) for extracting only the pilot signal 161.
(Or high-pass filter circuit (HPF circuit)) 1
6 and are input. In the carrier clock recovery circuit 18,
The carrier 181 required for demodulation by the demodulator 17 and the clock 182 required for decoding by the decoder 19 are reproduced by frequency-converting the pilot signal 161.

Here, the reproduction clock 182 is the same signal as the carrier wave or a signal obtained by multiplying the frequency of the carrier wave by J / L (J and L are natural numbers).

Next, the reproduced modulated signal 151 which is the output signal of the BPF circuit 15 is demodulated by the demodulator 17 shown in FIG. Furthermore, two demodulation I signals 17 from the demodulator 17
The 1 and the demodulated Q signal 172 are input to the decoder 19, and the 3-bit decoded digital signal 191 is output from the output terminal 20.

The third embodiment of the present invention will be described below with reference to the drawings. In the third embodiment shown in FIG. 3, the M-bit digital signal sequence 210 is input from the input terminal 2. The digital signal sequence 210 is converted into a 2-bit digital signal sequence 310 by the bit number conversion circuit 3. Further, the 2-bit digital signal sequence 310 is input to the convolutional encoder 4 and subjected to convolutional coding to become a 3-bit signal 410.

Regarding the convolutional code in the convolutional encoder 4, those described in detail in the literature ("Code theory", Hideki Imai, Institute of Electronics, Information and Communication Engineers, p247-p279) can be adopted.

Next, the convolutionally encoded 3-bit signal 410 is input to the mapping circuit 5, and the mapping circuit 5 arranges the signal points represented by the convolutionally encoded 3-bit signal 410 on the constellation plane. . Based on this signal point arrangement, two systems of I signals 510 and Q
The signal 520 and the signal 520 are output from the mapping circuit 5.

Here, the mapping circuit 5 is composed of a storage element such as a ROM, and the position data on the constellation plane of 8 signal points represented by 3-bit digital signals are written in the ROM in advance,
When a 3-bit digital signal, which is the output of the bit conversion circuit, is input, the position data of the reference signal point on the constellation plane represented by the 3-bit digital signal is read from the memory, and the two systems of I corresponding thereto are read. It outputs a signal and a Q signal.

As signal point arrangements in the mapping circuit, there are those shown in FIGS. 8, 9 and 10 given in the first embodiment.

Next, in FIG. 3, the output I signal 510 and the Q signal 520 from the mapping circuit 5 are input to the quadrature modulation circuit 6 and are quadrature-modulated by the carrier wave 71 from the carrier wave generation circuit 7. Here, the I signal 510 and the Q signal 520 are
Carrier wave 71 and carrier wave 7 in the quadrature modulation circuit shown in FIG.
1 is amplitude-modulated from 90-degree phase carrier waves 301 whose phases are different from each other by 90 degrees and added to form a modulated signal 61.

Then, the burst signal adding circuit 8 partially adds a burst signal having the same frequency and the same phase as the carrier wave 71 to the modulated signal as shown in FIG. The burst signal addition circuit output 81 superimposes the bias signal 101 from the bias signal generation circuit 10 in the bias addition unit 10 in order to make the magnetic recording / reproduction process linear.
Data is recorded on the magnetic recording medium 13 via the magnetic head 12. The signal recorded on the magnetic recording medium 13 is the magnetic head 1
Played by 5.

Further, the carrier reproduction circuit 18 reproduces a continuous reproduction carrier 181 from the burst signal included in the reproduction signal 151 reproduced via the magnetic head 15, and the reproduction signal 151 is demodulated by using the reproduction carrier 181. Demodulate at 17. Then, the two demodulated I signals 1 from the demodulator 17
71 and the Q signal 172 are input to the Viterbi decoder 19, Viterbi decoding is performed, and a 2-bit decoded digital signal is output from the output terminal 20.

The Viterbi decoding in the Viterbi decoder 19 is described in detail in, for example, the literature ("Code theory", Hideki Imai, The Institute of Electronics, Information and Communication Engineers, p280-p312) mentioned as a reference in the prior art. Things can be adopted.

The fourth embodiment of the present invention will be described below with reference to the drawings. In the fourth embodiment shown in FIG. 4, the M-bit digital signal series 210 is input from the input terminal 2. The digital signal sequence 210 is converted into a 2-bit digital signal sequence 310 by the bit number conversion circuit 3. Further, the 2-bit digital signal sequence 310 is input to the convolutional encoder 4 and subjected to convolutional coding to become a 3-bit signal 410.

As for the convolutional code in the convolutional encoder 4, those described in detail in the above-mentioned document ("code theory") can be adopted.

Next, the convolutionally encoded 3-bit signal 410 is input to the mapping circuit 5, and the mapping circuit 5 arranges the signal points represented by the convolutionally encoded 3-bit signal 410 on the constellation plane. . Based on this signal point arrangement, two systems of I signals 510 and Q
The signal 520 and the signal 520 are output from the mapping circuit 5.

Here, the mapping circuit 5 is composed of a storage element such as a ROM, and the position data on the constellation plane of 8 signal points represented by a 3-bit digital signal is written in advance in the memory in the ROM. , When a 3-bit digital signal which is the output of the bit conversion circuit is input, the position data of the reference signal point on the constellation plane represented by the 3-bit digital signal is read from the memory, and two systems corresponding to it are read. It outputs the I and Q signals. Further, as signal point arrangements in the mapping circuit, there are those shown in FIGS. 8, 9 and 10 given in the first embodiment.

Next, in FIG. 4, the output I signal 510 and Q signal 520 from the mapping circuit 5 are input to the quadrature modulation circuit 6 and are quadrature modulated by the carrier wave 71 from the carrier wave generation circuit 7.

Here, the I signal 510 and the Q signal 520 are
Carrier wave 71 and carrier wave 7 in the quadrature modulation circuit shown in FIG.
1 is amplitude-modulated by 90-degree phase carrier waves 301 whose phases are different from each other by 90 degrees, and added to form a modulated signal 61.

Further, the modulated signal 61 is added by the adder 22 with the pilot signal 211 obtained by converting the frequency of the carrier wave 71 from the carrier wave generation circuit 7 by the frequency conversion circuit 21. Then, the adder output 221 superimposes the bias signal 91 from the bias signal generating circuit 9 in the bias signal adding section 10 in order to make the magnetic recording / reproducing process close to linear, and is recorded on the magnetic recording medium 13 via the magnetic head 12. It The signal recorded on the magnetic recording medium 13 is reproduced by the magnetic head 14. The reproduction modulation signal 141 includes a bandpass filter circuit (BPF circuit) 15 for extracting only the modulated signal 151 and a lowpass filter circuit (LPF circuit) (or highpass filter circuit (HPF circuit)) 16 for extracting only the pilot signal 161. Entered in and. In the carrier / clock recovery circuit 18, the carrier 181 and the Viterbi decoder 1 required for demodulation in the demodulation circuit 17
The clock 182 required for decoding in 9 is the pilot signal 16
Playback is performed by frequency conversion of 1.

The Viterbi decoding in the Viterbi decoder 19 is described in detail, for example, in the literature ("Code theory", Hideki Imai, The Institute of Electronics, Information and Communication Engineers, p280-p312) mentioned as a reference in the prior art. Things can be adopted.

Here, the reproduction clock 182 is the same signal as the carrier wave or a signal obtained by multiplying the frequency of the carrier wave by J / L (J and L are natural numbers). Next, the reproduced modulated signal 151 which is the output signal of the BPF circuit 15 is demodulated by the demodulator 17 whose detailed configuration is shown in FIG. Further, the demodulation I signal 171 and the demodulation Q signal 172 of two systems from the demodulator 17 are input to the Viterbi decoder 19 and Viterbi decoding is performed to output a 2-bit decoded digital signal 191 from the output terminal 20.

In the above embodiment, the case where the mapping circuit input is 3 bits and the number of signal points is 8 has been described. Next, 16 signal points are provided on the constellation plane.
Examples of signal point arrangements used in the present invention in the case of points are shown in FIGS. 11, 12, and 13. These signal point arrangements increase the signal point intervals at the signal points farther from the origin on the constellation plane and decrease the signal point intervals at the signal points closer to the origin in the same manner as in the 8-value embodiment. By arranging points, it is possible to reduce the error rate of decoded data by allowing signal point variations at signal points far from the origin.

Further, in the above third and fourth embodiments,
The case where the output 2-bit signal sequence from the bit number conversion circuit is convolutionally encoded by adding a 1-bit redundant bit to a 3-bit digital signal by a convolutional encoder has been described. It is also possible to set 32 signal points on the constellation plane by adding 2 redundant bits to 3 bits and setting the output of the convolutional encoder to 5 bits. That is, the convolutional encoder can add redundant bits K (K is an integer of 1 or more) to N bits (N is an integer of 2 or more) output from the bit conversion circuit.

As described above, according to the present embodiment, the reproduction demodulation signal is reproduced on the constellation plane due to the influence of the jitter or the envelope fluctuation included in the reproduction signal in the multilevel amplitude phase modulation or the non-linear distortion in the magnetic recording / reproduction process. A signal point whose distribution from the origin is farther from the origin has a greater variation in the signal point distribution, so that a signal point with a farther distance from the origin on the constellation plane will be By arranging a signal point with a larger distance and a closer distance from the origin to a smaller distance from other signal points, the error rate of the decoded data at the reference point far from the origin is reduced and the overall error is reduced. It is possible to reduce the rate.

Here, the signal point arrangement on the constellation plane for 8-value phase modulation and 16-value quadrature amplitude modulation is described as the multi-value amplitude phase modulation method.
The same holds for other multilevel modulation methods.

[0051]

As described above, according to the present invention, on the constellation plane due to the influence of the jitter or the envelope fluctuation included in the reproduced signal in the multi-level amplitude phase modulation, or the non-linear distortion in the magnetic recording / reproducing process. Even if the dispersion of the signal point distribution of the regenerated demodulation signal becomes large at the signal point far from the origin, the signal point farther from the origin on the constellation plane allows other signals so that other signals are Since the signal points are arranged so that the distance from the origin is larger and the distance from the origin is closer to the other signal points, the error frequency of decoded data at the reference point far from the origin However, the error occurrence frequency of the decoded data at the reference point close to the origin becomes similar, and it is possible to reduce the error rate comprehensively.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a magnetic recording / reproducing apparatus according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a magnetic recording / reproducing apparatus according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a magnetic recording / reproducing apparatus according to a third embodiment of the present invention.

FIG. 4 is a configuration diagram of a magnetic recording / reproducing apparatus according to a fourth embodiment of the present invention.

FIG. 5 is a block diagram of a modulator used in this embodiment.

FIG. 6 is a schematic diagram of a recording signal to which a burst signal used in this embodiment is added.

FIG. 7 is a block diagram of a demodulator used in this embodiment.

FIG. 8 is a schematic diagram of an arrangement of eight signal points used in this embodiment.

FIG. 9 is a schematic diagram of another eight signal point arrangement used in this embodiment.

FIG. 10 is a schematic diagram of yet another eight signal point arrangement used in this embodiment.

FIG. 11 is a schematic diagram of an arrangement of 16 signal points used in this embodiment.

FIG. 12 is a schematic diagram of another 16-point signal point arrangement used in this embodiment.

FIG. 13 is a schematic diagram of still another 16-point signal point arrangement used in this embodiment.

FIG. 14 is a schematic diagram of a four-valued signal point arrangement (QPSK) used in a conventional magnetic recording / reproducing apparatus.

FIG. 15 is a schematic diagram of an 8-ary signal point arrangement (8PSK) used in a conventional magnetic recording / reproducing apparatus.

FIG. 16 is a schematic diagram of a 16-value signal point arrangement (16QAM) used in a conventional magnetic recording / reproducing apparatus.

FIG. 17 is a schematic diagram showing variations in signal point distribution of a reproduced demodulated signal on a constellation plane.

[Explanation of symbols]

 3 bit number conversion circuit 4 convolutional encoder 5 mapping circuit 6 orthogonal modulation circuit 7 carrier generation circuit 8 burst signal addition circuit 9 bias signal generation circuit 10 burst signal addition unit 12 magnetic head 13 magnetic recording medium 14 magnetic head 15 magnetic head 17 demodulation 18 Carrier wave clock recovery circuit 19 Decoder 21 Frequency conversion circuit 22 Adder

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaaki Kobayashi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (5)

[Claims] 1. A bit number conversion circuit for converting an input M-bit digital signal sequence into an N-bit (N is an integer of 2 or more) digital signal sequence, and 2 ^N corresponding to the N-bit digital signal sequence. Rather than arranging the signal points at equal intervals on the constellation plane, the signal points farther from the origin have a larger distance from other signal points, and the closer the distance from the origin is to the other signals. A mapping circuit that outputs two systems of signals that represent signal point positions so as to reduce the distance between the points and a quadrature that orthogonally modulates the two systems of signals using a carrier from a carrier generation circuit and outputs a modulated signal. A modulation circuit, a burst signal adding circuit for partially adding a burst signal having the same frequency as the carrier wave and the same phase to the modulated signal, and a recording signal output from the burst signal adding circuit. A bias applying unit for superimposing a bias signal having a frequency higher than twice the maximum frequency of the recording signal, and magnetic recording / reproducing for recording and reproducing the biased recording signal on a magnetic recording medium via a magnetic head. Section, a carrier wave reproducing circuit for reproducing a reproduced carrier wave continuous from the burst signal included in the reproduced signal reproduced through the magnetic head in the magnetic recording / reproducing section, and a demodulator for demodulating the reproduced signal with the reproduced carrier wave. And a decoder for decoding the demodulated signal from the demodulator and outputting the decoded signal as a decoded digital signal. 2. A bit number conversion circuit for converting an input M-bit digital signal sequence into an N-bit (N is an integer of 2 or more) digital signal sequence, and 2 ^N corresponding to the N-bit digital signal sequence. Rather than arranging the signal points at equal intervals on the constellation plane, the signal points farther from the origin have a larger distance from other signal points, and the closer the distance from the origin is to the other signals. A mapping circuit that outputs two systems of signals that represent signal point positions so as to reduce the distance between the points and a quadrature that orthogonally modulates the two systems of signals using a carrier from a carrier generation circuit and outputs a modulated signal. A modulation circuit; a frequency conversion circuit which receives the carrier wave as an input and frequency-converts and outputs a frequency-converted pilot signal which is a single frequency signal outside the occupied frequency range of the modulated signal; An adder for adding the ilot signal, a bias applying unit for superimposing a bias signal having a frequency twice or more higher than the highest frequency of the recording signal on the recording signal output from the adder, and the bias-added recording signal A magnetic recording / reproducing unit for recording and reproducing the data on a magnetic recording medium via a magnetic head, and reproducing a carrier wave from a pilot signal included in a reproduction signal reproduced by the magnetic recording / reproducing unit via the magnetic head. Magnetic recording / reproducing comprising a carrier wave reproducing circuit, a demodulator for demodulating the reproduced signal with the reproduced carrier wave, and a decoder for decoding the demodulated signal from the demodulator and outputting it as a decoded digital signal. apparatus. 3. A bit number conversion circuit for converting an input M-bit digital signal sequence into an N-bit (N is an integer of 2 or more) digital signal sequence, and convolutional encoding into the N-bit digital signal sequence. A convolutional encoder that adds a redundant bit of K bits (K is an integer of 1 or more) to an (N + K) -bit digital signal sequence, and 2 ^{N + K} signal points for the (N + K) -bit digital signal sequence. Rather than equidistantly on the constellation plane,
Signals of two systems representing the signal point position are set such that the signal point farther from the origin has a larger interval with other signal points, and the signal point closer to the origin has a smaller interval with other signal points. A mapping circuit for outputting, a quadrature modulation circuit for quadrature-modulating the signals of the two systems using a carrier from a carrier generation circuit and outputting a modulated signal, and a burst signal having the same frequency as the carrier and the same phase as the modulated signal A burst signal adding circuit for partially adding to the signal; a bias adding unit for superimposing a bias signal having a frequency higher than the maximum frequency of the recording signal by a factor of 2 on the recording signal output from the burst signal adding circuit; A magnetic recording / reproducing unit for recording and reproducing the added recording signal on the magnetic recording medium via the magnetic head, and reproduced by the magnetic recording / reproducing unit via the magnetic head. A carrier recovery circuit for reproducing a reproduced carrier wave continuous from the burst signal contained in the raw signal,
A magnetic recording / reproducing apparatus comprising a demodulator for demodulating the reproduced signal with the reproduced carrier wave and a Viterbi decoder for Viterbi decoding the demodulated signal from the demodulator and outputting the decoded signal as a decoded digital signal. 4. A bit number conversion circuit for converting an input M-bit digital signal sequence into an N-bit (N is an integer of 2 or more) digital signal sequence, and convolutional encoding into the N-bit digital signal sequence. A convolutional encoder that adds a redundant bit of K bits (K is an integer of 1 or more) to an (N + K) -bit digital signal sequence, and 2 ^{N + K} signal points for the (N + K) -bit digital signal sequence. Rather than equidistantly on the constellation plane,
Signals of two systems representing the signal point position are set such that the signal point farther from the origin has a larger distance from other signal points and the signal point closer to the origin has a smaller distance from other signal points. A mapping circuit that outputs, a quadrature modulation circuit that quadrature-modulates the signals of the two systems using a carrier from a carrier generation circuit and outputs a modulated signal, and a occupancy frequency range of the modulated signal that is outside the range occupied by the modulated signal. A frequency conversion circuit that frequency-converts and outputs a pilot signal that is a single frequency signal, an adder that adds the modulated signal and the pilot signal, and a recording signal that is the output of the adder of the recording signal A bias applying section for superimposing a bias signal having a frequency higher than twice the maximum frequency, and a recording signal with the bias applied are recorded and reproduced on a magnetic recording medium via a magnetic head. A magnetic recording / reproducing unit, a carrier reproducing circuit for reproducing a reproduced carrier from a pilot signal included in a reproduced signal reproduced by the magnetic recording / reproducing unit via a magnetic head, and a demodulator for demodulating the reproduced signal with the reproduced carrier. And a Viterbi decoder that Viterbi-decodes the demodulated signal from the demodulator and outputs the decoded signal as a decoded digital signal. 5. A bit number converting means for converting an input M-bit digital signal sequence into an N-bit (N is an integer of 2 or more) digital signal sequence, and 2 ^N corresponding to the N-bit digital signal sequence. On the constellation plane, set each signal point to a signal point that is farther from the origin so as to have a larger interval with another signal point, and to have a signal point that is closer to the origin have a smaller distance from another signal point. , A mapping means for outputting two systems of signals representing signal point positions, a quadrature modulation means for quadrature modulating the two systems of signals using a carrier and outputting a modulated signal, and an additional signal obtained based on the carrier. Is added to the modulated signal to obtain a recording signal, and bias adding means for superimposing on the recording signal a bias signal having a frequency higher than the highest frequency of the recording signal by at least twice. Pressurized been recorded signal through the magnetic head a magnetic recording apparatus and recording on a magnetic recording medium.