JPH0487072A - Magnetic recording device - Google Patents

Abstract

PURPOSE:To reduce the distortion component at reproduction by modulating the amplitude of one of two types of signals that has a relatively high frequency with a signal having a frequency double as high as that of the signal having a relatively low frequency and then recording the modulated signal. CONSTITUTION:The amplitude of one of two types of signals that has a relatively high frequency is modulated with a signal having a frequency double as high as that of the signal having a relatively low frequency. Then this modulated signal is recorded. In this respect, a frequency converter 101 is added to convert the frequency of a low band converting chrominance signal 6 into a double frequency together with a phase shifter 102, and an amplitude modulator 103 which modulates the amplitude of an FM luminance signal 7 with use of the signal 6. In such a recording way, a reproduced signal having a low modulation degree of amplitude, i.e., a reduced distortion component is obtained. Thus the effect is secured for compression of the distortion component caused when the frequency multiplex signals of >=2 types are recorded. Then the signal quality is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to correction of distortion that occurs when frequency multiplexed signals are magnetically recorded and reproduced.

[Prior art] Figure 5 shows, for example, Introduction to Home VTR (Corona Publishing) P. 1
50 is a signal processing circuit block diagram of a conventional home VTR shown in FIG. In the figure, (1) is a Y/C separator that separates the luminance signal and color signal, (2) is the separated luminance signal, and (3) is the luminance signal processing circuit consisting of an emphasis, FM modulator, etc. be. On the other hand, (4) is a separated color signal, and (5) is a color signal processing circuit composed of a frequency converter and the like. (6) is the low frequency conversion color signal, (7)
is the FM luminance signal. (8) is the low frequency conversion color signal (6)
and an FM luminance signal (7), (9) is a recording amplifier, (10) is a magnetic head, and (11) is a magnetic tape.

Next, the operation will be explained.

The video signal is input to the Y/C separator (1), and the luminance signal (
2) and a color signal (4). The luminance signal (1) is subjected to emphasis, FM modulation, etc. by a luminance signal processing circuit (3), and becomes an FM luminance signal (7). Color signal (4)
is converted to a low frequency color signal (6
). FM luminance signal (7) and low frequency conversion color signal (6)
are added by an adder (8) and transmitted as a current to a magnetic head (10) by a recording amplifier (9). This causes the magnetic head (10) to record on the magnetic tape (11).

[Problem to be solved by the invention] FIG. 6 shows the spectrum of the recorded signal.

In the figure, (12) is a low-pass conversion color signal subcarrier,
(13) is the FM luminance signal carrier, (14), (15)
is the distortion component. (a) is a recording signal spectrum.

The FM luminance signal (7) corresponds to the FM luminance signal carrier (13), and the low frequency converted color signal (6) corresponds to the low frequency converted color signal subcarrier (12). This signal is transferred to a magnetic tape (1
1), it is known that distortion components (14) and (15) appear in the FM luminance signal carrier (13) as shown in (b). These distortion components (14), (1
5) appears as a beat in the reproduced video signal and deteriorates the image quality. For this reason, if the recording level of the low-frequency conversion color signal is increased beyond a certain limit, the distortion components (14) and (1
5) increases and stands out on the screen, so the recording level of the low-frequency conversion color signal cannot exceed a certain limit. Therefore, it was not possible to obtain a sufficient S/N ratio of color signals.

The present invention was made to solve the above-mentioned problems, and an object of the present invention is to provide a magnetic recording device that can reduce distortion components.

[Means for Solving the Problems] A magnetic recording device according to the present invention (1) is a device that frequency-multiplexes and records at least two types of signals, and the relative difference between the two types of signals is A recording means for amplitude modulating a high frequency signal with a signal having a frequency twice that of a relatively low frequency signal and recording the result is provided.

(2) The recording means consists of an array of at least an amplitude modulator, a phase shifter, and a frequency converter, with the amplitude modulator on the output side of the luminance signal recording system and the frequency converter on the output side of the color signal recording system. positioned.

(3) Amplitude modulation is performed so that the high frequency signal has a maximum amplitude at positions corresponding to the local maximum and minimum of the instantaneous value of the low frequency signal.

[Operations] The amplitude modulation in this invention has the effect of compressing the distortion components generated when two or more types of frequency multiplexed signals are recorded.
Signal quality is greatly improved.

[Example] An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, (1) to (11) are the same or equivalent parts as in the prior art. (101) is the low-frequency conversion color signal (6
) to double the frequency, (102)
(103) is a phase shifter, and (103) is an amplitude modulator that modulates the amplitude of the FM luminance signal (7) by a low frequency conversion color signal.

Next, the operation will be explained. The steps up to obtaining the FM luminance signal (7) and the low-frequency conversion color signal (6) are the same as in the prior art.

Here, the causes of the distortion components (14) and (15) shown in FIG. 6 will be considered.

Almost all magnetic materials have a saturation magnetic flux density and saturation of magnetization occurs. In other words, even if a magnetic field greater than the - window is applied, there are some areas where magnetization will no longer occur. Therefore, it operates like an amplitude limiter.

When the signal obtained by adding the two types of signals shown in FIG. 7(a) is subjected to such amplitude limitation, the signal becomes as shown in FIG. 7(b). In the figure, (B) is the amplitude limit level.

If two types of signals are separated from this, the results will be as shown in (C) and (d). It can be seen that the signal (d) on the high frequency side is subjected to amplitude modulation at twice the frequency of the signal (C). From the above, the distortion components (14) and (15) shown in FIG. 6 are side hands that amplitude modulate the signal (13).

Based on the above considerations, distortion components can be canceled by applying amplitude modulation to the recording signal in advance.

The low frequency converted color signal (6) is sent to a frequency converter (101)
is converted to twice the frequency by This is a phase shifter (1
02) into an appropriate phase relationship and input to the amplitude modulator (103) to obtain an amplitude-modulated FM luminance signal. The adder (8) and subsequent parts are the same as in the conventional example. By recording in this manner, a reproduced signal with less amplitude modulation, that is, less distortion components (14) and (15) in FIG. 6, can be obtained.

Although the amount of phase shift of the phase shifter is not specified in the above embodiment, if the amount of phase shift of the phase shifter is not appropriately selected, the opposite effect will occur. However, this phase relationship changes depending on the phase characteristics of the circuit and head, and is difficult to understand experimentally. Therefore, we conducted a computer simulation and obtained the following findings.

The calculation method is “K, 5UZUKI: IEEE Tran
According to calculations, a phase shift occurs just by recording, and as shown in Figure 7(e), (d) will have different waveforms.

The reason for this is thought to be that the addition ratio of the FM luminance signal and the low-frequency converted color signal is less than half of the FM luminance signal, so the spread of the magnetic field is different. FIG. 3 shows changes in distortion components with respect to changes in phase amount. The waveform in (a) is a low-frequency converted color signal, and the waveform in (b) is a low-frequency converted color signal converted to twice the frequency.
, ■, ■, ■. The graph (C) shows the magnitude of the distortion component generated due to the magnetic recording and reproduction of the FM luminance signal carrier and the low frequency conversion color signal subcarrier for the phases ① to ②. (60) is the change in the distortion component appearing on the lower side of the FM luminance signal carrier (corresponding to Figure 6 (14)), and (61) is the change in the distortion component appearing on the upper side (corresponding to Figure 6 (15)) This is a change in Here, O
dB is the level of the distortion component when no amplitude modulation is applied. Where both of the curves (60) and (61) become small, that is, near the phase (2), the degree of amplitude modulation received by the reproduced FM luminance signal carrier becomes the smallest. It can also be seen that in the phase range from (1) to (2), the degree of the above-mentioned amplitude modulation becomes small, albeit slightly. In other words, the antinode part of the low-frequency conversion color signal (the local maximum and minimum part of the instantaneous value)
It can be seen that it is sufficient to apply amplitude modulation such that the amplitude is maximum in the vicinity.

Regarding the modulation degree, as shown in Figure 2, a phase shifter (
An attenuator (2) is provided between the frequency converter (102) and the frequency converter (101).
01), a greater effect can be obtained.

FIG. 4 shows the change in the distortion component caused by recording and reproducing the above-mentioned 2 carriers with respect to the degree of modulation.

OdB is the level of the distortion component when no amplitude modulation is applied. In the figure, (10) is the change in the distortion component appearing on the lower side of the FM luminance signal carrier (corresponding to (14) in Figure 6), and (61) is the change in the distortion component appearing on the upper side ((15) in Figure 6).
). This curve (70), (7
1) where both become small, that is, when the modulation depth is 0.
Near 1, the degree of amplitude modulation received by the reproduced FM luminance signal carrier is the smallest. It can also be seen that if the modulation degree is up to 0.2, the degree of the amplitude modulation becomes small, albeit slightly.

In addition, although two types of signals were described in the above embodiment, three types of signals were used.
The same applies even if there are more than one species. That is, it is sufficient to amplitude-modulate the signal having a relatively higher frequency among any two types of signals among three or more types of signals with a signal having twice the frequency of the lower signal.

[Effects of the Invention] As described above, according to the present invention, since magnetic recording is performed after amplitude modulation, distortion components during reproduction can be reduced, and high quality recording and reproduction is possible.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram showing a magnetic recording device according to an embodiment of the invention, FIG. 2 is a circuit block diagram showing a magnetic recording device according to a modification of the embodiment of the invention, and FIGS. 3 and 4 5 is a diagram showing the effect of amplitude modulation, FIG. 5 is a circuit block diagram of a conventional magnetic recording device, FIG. 6 is a diagram showing a spectrum diagram of a recording signal, and FIG. 7 is a diagram explaining the principle of distortion generation. In the figure, (1) is a Y/C separator, (3) is a luminance signal processing circuit, (5) is a color signal processing circuit, (8) is an adder,
(9) is a recording amplifier, (10) is a magnetic head, (11)
is a magnetic tape, (12) is a low frequency conversion color signal subcarrier, (13) is an FM luminance signal carrier, (14L (15)
is the distortion component, (60), (61), (70), (71) are the change curves of the distortion component, (101) is the frequency converter, (1
02) is a phase shifter, (103) is an amplitude modulator, (201)
is an attenuator. In each figure, the same reference numerals indicate the same or corresponding parts. Diagram ■ ■ ■ @ ■ ■ @ Phase diagram 0.050.1 0.2 Modulation degree

Claims (3)

[Claims] (1) A device that frequency multiplexes and records at least two types of signals, in which a relatively high frequency signal is recorded at twice the frequency of a relatively low frequency signal. 1. A magnetic recording device comprising a recording means for recording by amplitude modulating a signal. (2) A video recording device, wherein the recording means includes an array of at least an amplitude modulator, a phase shifter, and a frequency converter;
2. The magnetic recording device according to claim 1, wherein the amplitude modulator is located on the output side of the recording system for the luminance signal, and the frequency converter is located on the output side of the recording system for the color signal. (3) The magnetic recording according to claim 1, characterized in that amplitude modulation is carried out so that the high frequency signal has a maximum amplitude at a position corresponding to a local maximum or minimum of the instantaneous value of the low frequency signal. Device.