JP2512069B2 - Digital magnetic recording / reproducing device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a digital video tape recorder (DVT).
R) and other digital magnetic recording and reproducing devices.

2. Description of the Related Art In a conventional digital magnetic recording / reproducing apparatus, a baseband recording modulation system such as an NRZI system or an 8-10 conversion system is often used on the basis of saturated recording of a binary signal (for example, "Digital VTR"). High Density Magnetic Recording Technology Used for "Shozo Nakagawa, Journal of the Television Society, Vol. 35, No. 7
Issue (1981) pages 542-548).

In addition, in the field of communication, multi-value digital modulation methods such as multi-valued quadrature amplitude modulation (hereinafter referred to as multi-valued QAM) are being introduced in order to effectively use the transmission band. Since the magnetic recording / reproducing process has non-linearity, the PSK method with constant amplitude may only be used.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the configuration using the baseband modulation method as described above, the utilization efficiency of the recording frequency band (the bit rate that can be transmitted per unit band) is about 1.8 bps / Hz, This leads to an increase in tape consumption and makes long-time recording difficult.

Also, if a digital modulation method such as multi-level QAM is used, it is possible to improve the utilization efficiency of the recording frequency band.
There was a problem that S / N increased. Furthermore, due to the nonlinearity and amplitude fluctuations that occur during the magnetic recording / reproducing process, multi-level QAM
Made it difficult to use.

In order to solve the above-mentioned problems, a digital magnetic recording apparatus of the present invention is a multi-value digitizer for converting a digital signal into a multi-value digital code and adding burst information, and the multi-value digitizer. A quadrature two-phase modulator for quadrature amplitude modulating a digital code,
The frequency relationship between the clock signal used for the multi-level digital code (frequency is f _C ) and the carrier signal used for the quadrature amplitude modulation (frequency is f _H ) is f _H = n / m · f
_C (n ≦ m, n, m is a positive integer), and the timing at which the phases of the clock signal and the carrier signal match T = l · m /
a multi-valued quadrature amplitude modulation signal which is an output of the quadrature two-phase modulator, and a synchronous oscillator for generating a burst timing signal for each f _C (= l · n / f _H , 1 is a positive integer) It is characterized by having a recording system for recording on a magnetic recording medium.

The digital magnetic reproducing apparatus of the present invention reproduces a signal recorded by the above-mentioned digital magnetic recording apparatus, and is added by the multilevel converter included in the reproduced multilevel quadrature amplitude modulation signal. Burst detection circuit for detecting burst information, a burst amplitude detection circuit for detecting an amplitude value of the burst information, and a burst amplitude detection circuit for determining the amplification degree of the multilevel quadrature amplitude modulation signal reproduced from the magnetic recording medium. And a reproduction system having a reproduction equalizer that is controlled according to the detection result.

Effects The present invention, by the above configuration, it is possible to set the carrier frequency used for multi-level quadrature amplitude modulation as low as possible, and by using the low frequency of good transmission C / N of the magnetic recording medium, the transmission S / N can be improved. Further, by performing bias recording, it is possible to alleviate the non-linearity that occurs in the magnetic recording / reproducing process, and further control the amplification degree on the reproducing side based on the burst information to improve the amplitude fluctuation. Further, since multi-valued QAM is used, it is possible to improve the utilization efficiency of the recording frequency band as compared with the baseband modulation method.

Embodiment A digital 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 showing a main configuration of a digital magnetic recording / reproducing apparatus according to an embodiment of the present invention. The digital signal is input to the input terminal 1. The digital signal input to the input terminal 1 is based on the clock signal (frequency is f _C ) output from the synchronous oscillator 10,
At 3, it is converted to a multilevel digital code (a digital code with several amplitude level values). Also, in the multi-value digitizers 2 and 3,
Burst information is added based on the burst timing signal output from the synchronous oscillator 10. For example, the amplitude value of the multilevel digital code output from the multilevel converter 2 is set to zero, and the amplitude value of the multilevel digital code output from the multilevel converter 3 is set to the maximum value. By setting as described above, the burst information modulated by the quadrature two-phase variable width device 6 becomes a burst wave of a carrier signal (frequency is f _H ). Next, the multilevel digital codes output from the multilevel converters 2 and 3 are frequency-limited by the low-pass filters 4 and 5, and the quadrature 2
It is input to the phase modulator 6. In the quadrature two-phase modulator 6 having the root roll-off characteristic, the low-pass filters 4 and 5 use the carrier signal output from the synchronous oscillator 10 (the frequency is f _H ) to quadrature-amplitude-modulate the multilevel digital code. . Next, the multi-valued quadrature amplitude modulation signal output from the quadrature two-phase modulator 6 is added to the bias signal output from the bias signal oscillator 8 by the adder 7 to perform bias recording, and is added via the magnetic head 9. , Is recorded on the magnetic recording medium 19. Next, in the synchronous oscillator 10, the clock signal (frequency is f _C ), the burst timing signal (cycle is T), and the carrier signal (frequency is f _H ) satisfy the following relationship. To output. That is, the relationship between the clock signal frequency f _C and the carrier signal wave number f _H is
Let f _H = n / m, f _C (where n ≦ m, n, m is a positive integer).
Also, the cycle T of the burst timing signal is T = 1 / m /
Let f _C = l · n / f _H (where l is a positive integer). For example, when n = 4 and m = 5, the signal frequency spectrum at the LPFs 4 and 5 in FIG.
0.5), and the frequency relationship shown in the multilevel quadrature amplitude modulation signal spectrum of FIG. According to the above relation, T
When the clock signal and the carrier signal have the same phase for each cycle and the burst wave of the carrier signal is transmitted as described above, the clock signal and the carrier signal can be reproduced on the reproducing side. Further, the synchronous oscillator 10 is, specifically,
The main block configuration shown in FIG. 2 is obtained. That is, the oscillation circuit
21 output reference signals (which have a frequency of n · f _C ) are m
It is output to the frequency dividing circuit 22, the n frequency dividing circuit 23, and the burst timing generating circuit 24. The m-divider circuit 22 divides the reference signal by m to generate the carrier signal, and the phase selector circuit
Output to 25. Similarly, the n-divider circuit 23 divides the reference signal by n to generate the clock signal, and outputs the clock signal to the phase selection circuit 26. The burst timing generating circuit 24 divides the reference signal by 1 · m · n to generate and output a burst timing signal. Further, the phase selection circuits 25 and 26 select a phase so that the burst timing signal, the carrier signal and the clock signal always have a constant phase relationship, and output the carrier signal and the clock signal.

Next, returning to FIG. 1, the reproducing side will be described. The multilevel quadrature amplitude modulation signal recorded on the magnetic recording medium 19 is reproduced via the magnetic head 9 and input to the reproduction equalizer 11 and the phase locked oscillator 12. Here, the phase-locked oscillator 12
Is a block diagram of the main part shown in FIG. That is, the burst detection circuit 31 detects a burst wave, which is a carrier signal, from the reproduced multilevel quadrature amplitude modulation signal and outputs it. Next, the phase comparison circuit 33, the LPF 34, the oscillation circuit 35, and the m division circuit 3
7 constitutes a phase-locked loop (Phase Locked Loop),
The carrier wave signal phase-synchronized with the burst wave is output from the m frequency dividing circuit 37. Further, a frequency-synchronized reference signal (having a frequency of n · f _C ) is generated from the oscillation circuit 35, and n
Output to the frequency dividing circuit 36. The n-divider circuit 36 divides the reference signal by n and outputs a frequency-synchronized clock signal to the phase selection circuit 38. The phase selection circuit 38 selects the phase of the clock signal based on the burst wave detected by the burst detection circuit 31, and outputs a regular clock signal. Next, the burst amplitude detection circuit 32 compares the amplitude value of the burst wave detected by the burst detection circuit 31 with a reference value, detects the amplification degree that gives a normal amplitude value, and outputs it.

Next, returning to FIG. 1, the reproduction equalizer 11 amplifies the reproduced multilevel quadrature amplitude modulation signal based on the amplification degree output from the phase-locked oscillator 12, and at the same time generated in the magnetic recording / reproduction process. The frequency deterioration is corrected and output to the synchronous detector 13. The synchronous detector 13 demodulates the reproduced multilevel quadrature amplitude modulation signal using the carrier signal output from the phase locked oscillator 12, and outputs the demodulated multilevel quadrature amplitude modulated signal to the low pass filters 14 and 15. The low-pass filters 14 and 15 limit the frequency of the root roll-off characteristic and output the reproduced multilevel digital code to the inverse multilevel converters 16 and 17. In the inverse multilevel converter 16, 17, while using the clock signal that is the output of the phase locked oscillator 12 to convert the multilevel digital code to the original digital code, the burst wave that is the output of the phase locked oscillator 12 Based on the timing, the burst information is removed and the original digital code is output to the terminal 18.

In the above embodiment, the method of reproducing the carrier signal by applying the phase synchronization using the burst wave was described.
Similar results can be obtained by using a carrier signal reproduction method such as a multiplication method, an inverse modulation method, a Costas method (particularly, a selective control type).

Further, in the above embodiment, the case where the quadrature amplitude modulation method is used is described, but the phase modulation method (multilevel PSK) is used.
It can also be used for other modulation methods such as.

As described above, according to the present invention, on the recording side of the digital magnetic recording / reproducing apparatus, the clock signal frequency f _C and the carrier signal frequency f _H are f _H = n / m · f _C (however, , N ≦ m,
n and m are positive integers), and the period T of the burst timing signal is T = 1 / m / f _C = l / n / f _H
(Where l is a positive integer), and the burst wave of the carrier wave is added according to the burst timing signal. Therefore, the clock signal and the carrier signal can be reproduced on the reproducing side by using the burst wave, and the frequency of the carrier signal can be set to be lower than the clock signal frequency. Therefore, transmission of magnetic recording media
Low frequencies with good C / N can be used, and transmission S / N can be improved.

The non-linearity in the magnetic recording / reproducing process is improved by performing bias recording.

Further, with respect to the amplitude fluctuation occurring in the magnetic recording / reproducing process, the amplitude value of the burst wave is detected and the amplification degree of the reproduced multilevel quadrature amplitude modulation signal is controlled, so that the amplitude fluctuation is also improved. can do.

In addition, since recording / reproducing is performed using a multilevel quadrature amplitude modulation signal, it is possible to improve the utilization efficiency of the recording frequency band as compared with the paceband modulation method.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1A and 1B are block diagrams showing a main part of a digital magnetic recording / reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a block diagram showing a main part of a synchronous oscillator, and FIG. FIG. 4 (a) is a signal frequency spectrum diagram after passing through an LPF, and FIG. 4 (b) is a frequency spectrum diagram of a multi-valued quadrature amplitude modulation signal. 2,3 ... Multi-value converter, 4,5 ... LPF, 6 ... Quadrature two-phase modulator, 7 ... Adder, 8 ... Bias signal oscillator, 9 ...
Magnetic head, 10 ... Synchronous oscillator, 11 ... Playback equalizer, 12 ... Phase-locked oscillator, 13 ... Synchronous detector, 14,15
…… LPF, 16,17 …… Inverse multi-value converter, 19 …… Magnetic recording medium,
21 …… Oscillation circuit, 22 …… m divider circuit, 23 …… n divider circuit, 24 …… Paste timing generation circuit, 25,26 …… Phase selection circuit, 31 …… Paste detection circuit, 32 …… Paste Amplitude detection circuit, 33 ... Phase comparison circuit, 34 ... LPF, 35 ...
… Oscillator circuit, 36 …… n divider circuit, 37 …… m divider circuit, 38
...... Phase selection circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Etsuto Nakatsu 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Masaaki Kobayashi 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. In-house (56) References JP-A-55-22261 (JP, A)

Claims (4)

(57) [Claims] 1. A multilevel converter for converting a digital signal into a multilevel digital code and adding burst information, a quadrature binary phase modulator for quadrature amplitude modulation of the multilevel digital code, and the multilevel digital code. Clock signal (frequency f _C
And a carrier signal (frequency is f _H ) used for the quadrature amplitude modulation is f _H = n / m · f _C (n ≦ m,
n and m are positive integers, and the timing at which the phases of the clock signal and the carrier signal match T = l · m / f _C (= l
Each n / f _H , 1 is a positive integer), a synchronous oscillator for generating a burst timing signal is provided, and the multilevel quadrature amplitude modulation signal output from the quadrature two-phase modulator is recorded on the magnetic recording medium. A digital magnetic recording device having a recording system. 2. A digital magnetic recording apparatus according to claim 1, wherein the multi-valued quadrature amplitude modulation signal is applied to the magnetic recording medium by applying a bias signal to perform bias recording. 3. A multilevel converter for converting a digital signal into a multilevel digital code and adding burst information, a quadrature binary phase modulator for quadrature amplitude modulation of the multilevel digital code, and the multilevel digital code. Clock signal (frequency f _C
And a carrier signal (frequency is f _H ) used for the quadrature amplitude modulation is f _H = n / m · f _C (n ≦ m,
n and m are positive integers, and the timing T = l · m / f _C (= 1) at which the phases of the clock signal and the carrier signal coincide with each other.
A synchronous oscillator for generating a burst timing signal for each n / f _H , l and a recording system for recording a multilevel quadrature amplitude modulation signal output from the quadrature two-phase modulator on a magnetic recording medium A digital magnetic reproducing device for reproducing a signal recorded by a digital magnetic recording device comprising:
A burst detection circuit for detecting burst information added in the reproduction signal by the multilevel converter, a burst amplitude detection circuit for detecting an amplitude value of the burst information, and the multi-value reproduced by the magnetic recording medium. A digital magnetic reproducing apparatus comprising a reproducing system having a reproducing equalizer for controlling an amplification degree of a value quadrature amplitude modulation signal according to a detection result of the burst amplitude detecting circuit. 4. A multilevel converter for converting a digital signal into a multilevel digital code and adding burst information, a quadrature phase modulator for quadrature amplitude modulation of the multilevel digital code, and a multilevel digital code. Clock signal (frequency f _C
And a carrier signal (frequency is f _H ) used for the quadrature amplitude modulation is f _H = n / m · f _C (n ≦ m,
n and m are positive integers, and the timing at which the phases of the clock signal and the carrier signal match T = l · m / f _C (= l
Each n / f _H , 1 is a positive integer), a synchronous oscillator for generating a burst timing signal is provided, and the multilevel quadrature amplitude modulation signal output from the quadrature two-phase modulator is recorded on the magnetic recording medium. A recording system, a burst detection circuit for detecting the burst information added by the multilevel converter included in the multilevel quadrature amplitude modulation signal reproduced from the magnetic recording medium, and an amplitude value of the burst information. A reproduction system having a burst amplitude detection circuit and a reproduction equalizer for controlling the amplification degree of the multilevel quadrature amplitude modulation signal reproduced from the magnetic recording medium according to the detection result of the burst amplitude detection circuit. A digital magnetic recording / reproducing apparatus characterized by the above.