JPS5968802A - Magnetic recording method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording method, and more particularly to a frequency-separated multiplex recording method.

31\- twice 6.87717 seconds, V with head gap length 0.3 pm
TR is considered to be the limit, and in order to ensure a video signal S/N of 4 odB or more with such a VTR, the luminance signal band should be 2 MHz and the chromaticity signal band should be 0.8 MHz.
Must be within Therefore, such a method cannot secure a sufficient band, so even if cross-modulation interference can be removed, it has the disadvantage that a good reproduced image cannot be obtained due to the narrow band.

Furthermore, as the head gap length becomes narrower, a problem arises in that the recording efficiency decreases.

OBJECT OF THE INVENTION The object of the present invention is to multiplex record a plurality of signals without cross-modulating them.

Structure of the Invention The present invention solves the problem of cross-modulation interference by separating and recording multiple signals using the primary band and secondary band determined by the Herad gap length. The present invention provides a magnetic recording method.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings4.-
7. FIG. 1 is a characteristic diagram showing the relationship between the frequency and reproduction output of the annular magnetic head of a VTR for carrying out the magnetic recording method which is an embodiment of the present invention.

In the figure, reference numeral 1 denotes a magnetic recording/reproducing head (hereinafter referred to as head) in which a coil 4 is wound around a core 3, and the head 1 is provided with a gap 2 having a gap length q.

A magnetic tape 6 is in contact with the head 1.

When the tape is run and reproduced in the state shown in FIG. A reproducing voltage proportional to the temporal change in magnetic flux is generated in the wound coil 4. However, as shown in FIG. 2, when the frequency becomes high and the wavelength λ becomes equal to the gap length q, the magnetomotive force applied to the gap 2 becomes zero, and no reproduction voltage appears in the coil 4.

This is because the gap length q is equal to the signal wavelength λ as shown in Figure 2.
It also occurs when it matches an integer multiple of . For example, tape 5
The playback output in a rotary two-head VTR with a head gear luff length g-0.97 μm and a relative speed of 5.8 ml/second is fl-6MH2°f2-12MH2, which is close to the theoretical value shown in Figure 2. characteristics are obtained.

In addition, tape surface treatment technology has improved, and gap loss due to tape surface roughness has become extremely small.Furthermore, as head processing technology has improved, it has become practical to use a signal with a wavelength λ shorter than the gap length q. It can be made large enough to cause no problems.

Therefore, in this embodiment, a primary band with a frequency of 0 to 6 M) (z) is used to record the luminance signal of the video signal, and a secondary band of a frequency of 6 to 12 MHz is used to record the color signal of the video signal. By using this, it is possible to record a video signal without cross-modulation.

Next, a specific recording and reproducing apparatus for realizing the recording method of the above embodiment will be explained with reference to FIG.

FIG. 3 is a block diagram of essential parts of a VTR for realizing a recording method according to an embodiment of the present invention.

In the figure, 22 is a separation circuit that separates a composite video signal including a luminance signal and a chrominance signal applied from the input terminal 21, and 23 is a separation circuit that separates the luminance signal by frequency deviation (PEA).
K-To-PEAK) 3.0 to 4.5 MHz, F for converting to an FM signal with a center frequency of 3.75 MHz.
M modulation circuit 24 is a pulse width modulation circuit for width modulating the color signal into a pulse having a center frequency of 9 MHz.

26 is the output of the FM modulation circuit 23 and the pulse width modulation circuit 24
This is a mixing circuit for mixing the output of the recording head 26 and applying the mixed output to the recording head 26 that comes into contact with the tape 27.

28 is a reproducing head disposed so as to be in contact with the tape 27; 29 is a separation circuit having a low-pass filter and a bypass filter both having a cutoff frequency of 6 MHz; 30;
31 is an FM detection circuit, 31 is a color signal processing circuit, 32 is a mixing circuit for mixing the output of the FM detection circuit 30 and the output of the color signal processing circuit 31, and 33 is a composite signal output terminal.

Next, the operation of this device will be explained. The NTSC composite video signal applied to the input terminal 21 is separated into a luminance signal and a color signal by a separation circuit 22, and the luminance signal is sent to an FM modulation circuit 2.
The signal is FM modulated at 3 and applied to the gold circuit 257/\-. On the other hand, the separated color signal is applied to a mixing circuit 25 via a Nockle width modulation circuit 24. The mixed signals mixed by the mixing circuit 25 are multiplex recorded on the tape 27 via the magnetic head 26 in a frequency-separated state.

The tape 27 multiplexed in this way is played back by the playback head 28, and the separated modulated luminance signal that has passed through the low-pass filter of the separation circuit 29 is sent to the FM detection circuit 3o.
The signal is detected and demodulated into a luminance signal, which is sent to the output terminal 33 via the mixing circuit 32. On the other hand, the separated modulated color signal that has passed through the no-pass filter of the separation circuit 29 is demodulated into a color signal by the color signal processing circuit 31 and then sent to the mixing circuit 32.
The signal is sent to the output terminal 33 via.

In this way, a composite signal similar to the composite signal applied to the input terminal 21 can be obtained from the output terminal 33.

In this way, in this embodiment, by recording the luminance signal within the primary band of 0 to 6 MHz and the color signal within the secondary band of 6 MHz to 12 MHz, the luminance 8...-7 signal is 2. f5 MHz or more, the color signal is 1.5 MHz or more, and a S/N of 40 dB or more can be secured for each signal, so that good image recording can be performed. Furthermore, recording efficiency can also be improved by increasing the head gap length.

In this embodiment, the luminance signal is transmitted within the first band, and the luminance signal is transmitted within the second band.
Although an example has been shown in which the color signal is recorded within the next band, the present invention is not limited to this, and the color signal may be recorded within the first band, and the luminance signal may be recorded within the second band. Furthermore, although an example has been shown in which a color signal modulated during pulses is recorded within the secondary band, FM modulated or PCM modulated color signals or audio signals may also be recorded.

Effects of the Invention As described above, according to the present invention, the signal band can be greatly expanded compared to the conventional case where only the primary band is used, and good signal recording without cross modulation can be performed. can.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a VTR annular magnetic head for carrying out a magnetic recording method according to an embodiment of the present invention, FIG. 2 is a characteristic diagram showing the relationship between frequency and reproduction output of the head, and FIG.
The figure is a block diagram of main parts showing a specific example of the same VTR. 1... Magnetic head, 2... Air gap, 3.
... Core, 4 ... Coil, 6 ... Magnetic tape, 21 ... Input terminal, 22 ...
・Separation circuit, 23...FM modulation circuit, 24...
... Pulse width modulation circuit, 25 ... Mixing circuit, 26 ... Recording magnetic head, 27 ... Hitting magnetic tape, 28 ... Reproducing magnetic head, 29...
...Separation circuit, 30...FM detection circuit, 31
...Color signal processing circuit, 32...Mixing circuit, 33...Output terminal. Name of agent: Patent attorney Toshio Nakao (1st person)
Figure 2 Δ711 Figure 3 3

Claims (1)

[Claims] (1) A first signal whose shortest recording wavelength within the band is longer than the gap length of the magnetic head, and a second signal whose longest recording wavelength within the band is shorter than the gap length of the magnetic head. A magnetic recording method characterized by recording on a magnetic recording medium via a head. Recording method. Recording method.