JP2648334B2 - Magnetic recording method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording system for digitizing an information signal such as a high-definition television signal and recording it on a magnetic recording medium such as a magnetic tape in a multi-track manner. , A multi-bit digital information signal can be recorded with a small number of tracks.

(Summary of the Invention) According to the present invention, when digitizing a high-definition information signal such as a high-definition signal to a PCM or the like and performing multi-track magnetic recording, the LSB side bit of the output of the A / D converter is returned to an analog signal by a D / A converter. , The MSB side multiple bits are equally distributed to multiple tracks for recording, superimposed and recorded on two layers, and utilizing both advantages of digital recording and analog recording, a reproduction information signal with a small number of tracks and a good SN ratio Is obtained.

2. Description of the Related Art Conventionally, in order to magnetically record a digital information signal, for example, an 8-bit digital image signal obtained by digitizing a high-definition broadband image signal by PCM in a multi-track manner, each bit of an 8-track magnetic tape is recorded. The signals were recorded in parallel as they were.

(Problems to be Solved by the Invention) Therefore, conventionally, for example, in order to magnetically record and reproduce a digital image signal having an 8-bit configuration in multiple tracks, it is necessary to use an 8-bit digital image signal.
Since a channel recording / reproducing signal processing system and a magnetic head system are required, there is a problem that the circuit scale of the magnetic recording / reproducing apparatus and the magnetic head driving mechanism become complicated and expensive.

(Means for Solving the Problems) However, in this type of conventional magnetic recording / reproducing method, there is a waste in handling each bit of the digital information signal equally on both the MSB side and the LSB side with equal weight.

On the other hand, in the magnetic recording according to the present invention, among the plurality of bits forming the digital information signal, the multi-bit recording representing the important information component on the MSB side is subjected to multi-track recording via a multi-channel signal processing system. Apply, but LSB
A plurality of bits representing a relatively small information component on the side are returned to a one-channel analog signal by a single signal processing system, and the MSB
The multiple side bits are distributed evenly over the multiple tracks on which they were recorded, respectively, and overwritten, so that an information signal with a high SN ratio can be reproduced comprehensively with the minimum number of tracks, and the LSB side analog signal is In addition, recording and reproduction in a narrow band is performed by amplitude modulation or the like, without using frequency modulation of a carrier wave.

That is, the magnetic recording method of the present invention converts a digital information signal composed of a plurality of bits into a plurality of most significant bits and a plurality of least significant bits, and converts the least significant bits into an analog signal. In a twin-type magnetic head having a plurality of narrow gaps and wide gaps arranged close to each other, a surface magnetic layer having a higher coercive force and a magnetic layer having a lower coercive force are respectively provided through the narrow gaps. In the magnetic recording medium having two layers of the deep magnetic layer, the most important bits are respectively recorded in a plurality of channels of the surface magnetic layer, and the wide gap in the twin magnetic head is The analog signal is distributed to the plurality of channels of the deep magnetic layer in the magnetic recording medium and recorded. It is intended.

(Operation) Therefore, according to the magnetic recording of the present invention, digital magnetic recording / reproduction with a high SN ratio can be performed with a device that is smaller and consumes less power than in the past, and it was conventionally necessary to use an open reel. Magnetic recording can be performed by a cassette.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings with reference to examples.

FIG. 1 shows a configuration example of a magnetic recording / reproducing apparatus according to the method of the present invention. In the illustrated configuration example, for example, the frequency band
22MHz high definition video signal input 1 to A / D converter 2
Sampled at a clock frequency of 54 MHz and converted into an 8-bit digital video signal, of which the LSB side 4 bits 4 (a) to 4 (d) are converted into a 1-channel analog video signal 20 by the D / A converter 19. Reconvert and AM modulator
The carrier is amplitude-modulated by 21 and converted into a carrier analog video signal whose bandwidth is not expanded.

In the magnetic recording of the present invention, as described above, the LSB side bits of the digital information signal are returned to the one-channel analog information signal, and the distributor 22 has the same contents / same as, for example, four channels (a) to (d). Level, and supplied to the twin-type magnetic head 9 via the amplifiers 23 (a) to 23 (d) and the corresponding switches of the switching unit 8, respectively. Recording is performed on the magnetic layer of the tape 10 to the deep layer. The twin-type magnetic head 9 has twin elements in which a wide gap and a narrow gap are back-to-back arranged in parallel by the number of multi-tracks.
Wide and deep recording on 10 magnetic layers.

On the other hand, the 4 bits 3 (a) to 3 (d) on the MSB side of the digital video signal from the A / D converter 2 are synchronized by the synchronization / error correction code adding circuits 5 (a) to 5 (d).
After adding ID and error correction code ECC respectively,
Modulation is performed by the modulators 6 (a) to 6 (d), respectively, and the corresponding switches of the amplifiers 7 (a) to 7 (d) and the switch unit 8 are sequentially passed to the narrow gap of the twin type magnetic head 9 respectively. Each of them is supplied and overwritten and recorded on each track of the surface layer of the magnetic layer in the magnetic tape 10.

In reproducing an 8-bit digital video signal recorded over the four tracks of the surface layer and the deep layer of the magnetic layer in the magnetic tape 10 as described above, first, a twin type digital signal is reproduced from the four tracks of the surface layer. The MSB side 4-bit signal reproduced by the narrow gap of the magnetic head 9 is
Applicable switch and amplifier (HA) of switch unit 8
12 (a) to 12 (d) are sequentially supplied to an equalization and time base correction (TBC) circuit 13 (a) to 13 (d) to perform waveform equalization and reproduction of an appropriate clock. Then, the digital signal 15 is reproduced by the demodulators 14 (a) to 14 (d) and supplied to the D / A converter 17 via error correction circuits (ECC) 16 (a) to 16 (d), and the MSB The digital video signal of 4 bits is converted to an analog video signal 18 representing the outline of an image and supplied to a mixing circuit 34.

On the other hand, the carrier analog video signal 24 uniformly reproduced from the four tracks in the deep portion of the magnetic layer of the magnetic tape 10 by the wider gap of the twin-type magnetic head 9 is converted into an amplifier (H
A) 25 (a) to 25 (d) and equalizing circuits 26 (a) to 26
(D) are sequentially added to each other by a mixing circuit 27 to obtain a carrier analog video signal 28 having a level corresponding to the above-mentioned reproduced digital video signal, and a time axis correction circuit (RF / TBC) 29 performs the same. And time axis correction circuit 13 (a)
(D) to remove the time axis fluctuations, adjust the timing to the above-mentioned reproduced digital video signal, extract the carrier analog video signal 31, detect it by the AM demodulation circuit 32, and detect the minute change of the image. Is restored and supplied to the mixing circuit 34.

Therefore, from the mixing circuit 34, the video signal output 35 that faithfully reproduces the high-definition video signal of the frequency band 22 MHz is output.
Is obtained.

In the configuration example of the magnetic recording / reproducing apparatus according to the method of the present invention described in detail above, the carrier analog video signal obtained by amplitude-modulating the carrier by the AM modulator 21 is magnetically recorded. Instead of amplitude-modulating the carrier, Most commonly, the analog video signal can be magnetically recorded by direct recording using a high frequency bias.

Even when the carrier analog video signal is magnetically recorded in the same manner as in the above-described configuration example, instead of equally dividing the MSB side and the LSB side into four bits, the number of bits is changed from 1 bit to 7 bits. It can also be divided.

In order to strictly adjust the level of the reproduced analog signal between the digital signal processing system transmitting the MSB side 4 bits and the analog signal processing system transmitting the LSB side 4 bits, for example, an 8-bit original digital video The pulse signal of the pulse height corresponding to the signal "00001111" is inserted into the vertical flyback period of each converted output analog video signal in the D / A converter 19 of the analog signal processing system and the D / A converter 17 of the digital signal processing system, respectively. It is desirable to set the reference signal level as the reference signal level.

(Effects of the Invention) As is clear from the above description, according to the present invention, there are a number of effects listed below in magnetic recording.

(A) The number of signal processing channels required for multi-track recording is reduced, and the device can be reduced in size and power consumption can be reduced.

(B) Conventionally, a multi-track magnetic recording of an 8-bit digital signal requires an 8-channel signal processing system and 8 recording tracks, but the present invention requires a 5-channel signal processing system and Four recording tracks are sufficient, and the recording density can be doubled.

Therefore, the digital signal recording of the recording time, which was conventionally achieved only by the magnetic tape of the open reel, can be achieved by the cassette tape, and the operability and reliability of the apparatus are improved.

(C) The economy and mobility of the device are improved by the effects described in the items (a) and (b).

Furthermore, the following items can be cited as individual technical effects.

(D) The disadvantage of analog amplitude modulation recording, in which the bandwidth of the recording signal is narrow but the SN ratio of the reproduction signal is low, is remedied by combining it with digital recording.

(E) Time axis correction circuit (RF / TB) for processing amplitude modulated waves
C) 29 is easy to configure because the signal bandwidth is narrow.

(F) Since there is no DC component in the analog signal obtained by DA-converting the digital signal of the LSB side bit, a recording signal suitable for a rotary head type magnetic recording / reproducing apparatus which exhibits a low-frequency cutoff characteristic by a rotary transformer and a differential characteristic during reproduction is provided. Will be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration example of a magnetic recording / reproducing apparatus according to the method of the present invention. DESCRIPTION OF SYMBOLS 1 ... Video signal input 2 ... A / D converter 3 ... MSB side bit 4 ... LSB side bit 5 ... Synchronization and error correction code addition circuit 6 ... Modulator, 7,23 ... Amplifier 8 ... Switch unit, 9 ... Twin Type magnetic head 10 ... Double-layer magnetic tape, 11 ... Running direction 12, 25 ... Amplifier (HA) 13 ... Equalization and time axis correction (TBC) circuit 14 ... Demodulation circuit 15 ... Digital video signal 16 ... Error correction circuit (ECC) ) 17,19… D / A converter 18,20,33… Analog video signal 21… AM modulator, 22… Distribution circuit 24,28,31… Carrier analog video signal 26… Equalization circuit, 27,34… Mixing circuit 29: Time axis correction circuit (RF / TBC) 30: Control signal, 32: AM demodulation circuit 35: Video signal output

Claims (1)

(57) [Claims] A digital information signal comprising a plurality of bits is divided into a plurality of most significant bits and a plurality of least significant bits, and the plurality of least significant bits are converted into an analog signal. In a twin-type magnetic head having a plurality of gaps and a wider gap arranged close to each other, a surface magnetic layer having a higher coercive force and a deep magnetic layer having a lower coercive force via the narrower gap, respectively. In the magnetic recording medium having two layers, the most important bits are respectively recorded in a plurality of channels of the surface magnetic layer, and the magnetic field is respectively transmitted through the wide gap in the twin magnetic head. A magnetic recording system, wherein the analog signal is distributed to the plurality of channels of the deep magnetic layer of a recording medium and recorded.