JPS63282902A - Magnetic recording and reproducing device by depth recording - Google Patents

Abstract

PURPOSE:To improve the S/N of a signal depth-recorded by inserting a filter means to compensate the frequency characteristic of the erasing rate of a sound FM signal by a luminance FM signal to the recording system of the sound FM signal. CONSTITUTION:Right and left sound signals are respectively inputted from input terminals 1 and 2 and given to a first FM modulation circuit VCO3 and a second FM modulation circuit VCO4. The circuit 3, for example, has 1.3MHz as a center frequency and the circuit 4, for example, has 1.7MHz as the center frequency. A BPF7 cancels a higher harmonics component in the output of the circuits 3 and 4 and obtains the frequency characteristic of the level of sound FM signal to be recorded as a desired one. The output of the BPF7 is supplied through a coupling capacitor 10 to a recording amplifier. This BPF7, for example, has 2MHz as the center frequency and by the frequency characteristic of a low area side, an erasing due to a luminance FM signal is compensated.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a magnetic recording/reproducing apparatus that frequency-modulates an audio signal and records/reproduces it together with other information signals, such as video signals.

(b) Conventional technology 2 In a video tape recorder (VTR) using the magnetic resonance scan method, audio signals are FM (frequency) modulated and recorded/played using a rotating head in the same way as video signals. It is.

One such method is the so-called depth recording method. This is a method in which a relatively low frequency audio carrier that is FM modulated by an audio signal is recorded deep into the magnetic material, and then a video signal is overwritten.
It is adopted in the method.

The recording method in the VH8 system is described in detail in the Technical Report VR59-3 of the Television Society of Japan. To explain briefly, in order to record in stereo, 1.
Carrier signals of 3 MHz (f+) and 1.7 MHz (h) are used, and since the carrier signal of fz is more easily erased by the video signal, the recording current of fl is made larger than that of fl for balance.

By the way, since the audio carriers t+ and h are frequency modulated, the recorded frequency changes depending on the modulation voltage (input audio signal). For example, if the maximum frequency deviation is ±15
QKHz, the difference between the minimum and maximum frequency is 3
QQKH1, the central voice carrier (generally 1-2M
Hz), the degree of cancellation by the video luminance FM signal described earlier is quite different.

Therefore, the thickness of the reproduced audio FM signal (audio frequency modulation signal) is 6.
This is fine if the frequency deviation is small, but if it becomes large, it will result in a difference in the level of the reproduced FM signal, and if the output of the tape is small, it will cause noise and cause noise. This results in a deterioration of the relative signal level (, S/N) and worsens the actual S/N.This is because in the past, only the balance of carrier signals f+ and h was considered.

(C) Problems to be Solved by the Invention The present invention attempts to prevent the above-mentioned deterioration in sound quality due to the fact that the erasure rate of the audio FM signal by the luminance FM signal has a frequency characteristic.

B) Means for Solving the Problems The present invention inserts filter means for compensating the frequency characteristics of the erasure rate of the audio FM signal by the luminance FM signal into the audio FM signal recording system.

(e) Effects Therefore, the reproduction level of the audio FM signal has a flat frequency characteristic, and it is possible to prevent the sound quality from deteriorating as in the prior art.

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

FIG. 1 is a circuit diagram of an embodiment, and FIG. 2 is a characteristic diagram of a bandpass filter.

In Fig. 1, (1) and (2) are input terminals into which left and right audio signals are respectively input, (3) is a first FM modulation circuit (first VCO) with a center frequency of 1.3 MHz, and (4) is a second FM modulation circuit with a center frequency of 1.7 MHz (
2nd V CO), (5) and (6) are adjustment resistors that determine the recording level, and (7) is the FM modulation circuit (3) and (4).
This is a bandpass filter whose purpose is to remove harmonic components in the output and to adjust the level of the recorded audio FM signal to a desired frequency characteristic sound.

The output of the bandpass filter (7) is connected to the resistor (8) (9)
The level of the signal is adjusted at 101, and the signal is supplied to a recording amplifier (not shown) via a coupling capacitor (101).Then, the audio FM signal whose frequency characteristics have been compensated is applied from the recording amplifier to the audio rotary head, and is recorded. It turns out.

The bandpass filter (7) has a center frequency of 2MH2, and the frequency characteristics on the low frequency side are important.

In other words, the lower frequency characteristics compensate for the cancellation caused by the luminance FM signal. The low frequency side of the band pass filter (7) is connected to the audio FM signal band (1, 15
MHz-1.85MHz), approximately 60 (dBl
oct).

In reality, the difference in attenuation between 1.3 MHz and 1.7 MHz (2 MHz is QdB) is 9.5 dB±.
It is 1.5 dB, and has a characteristic that the slope is approximately linear (in decibels).

There is a peak of attenuation near 3.3 MHz on the high frequency side, but this is due to the two FM modulation circuits (3) and (4).
This is to thicken (attenuate) the 6th harmonic included in the output.

The characteristics of the low-frequency side of this bandpass filter (power) were obtained through actual measurements as follows: FM in the luminance signal
Recording was actually performed with the modulation circuit in a non-modulated frequency output state, and characteristics were determined so that the spectrum of the audio FM signal would be flat when reproduced.

In addition, the level adjustment resistor (5M6) takes into account the influence of the low-frequency color signal (if the low-frequency color signal is also recorded, the 1.3 MHz signal will be erased more easily). ), the resistance value of the resistor (6) is increased so that the output of the second FM modulation circuit (4) is further attenuated.

Therefore, the recording/reproducing operation is performed as follows.

If the two FM modulation signals are sine waves, the spectrum will be as shown in Figure 3, and by passing through a filter (C) having attenuation characteristics as shown in Figure 4 in the band of the audio FM signal,
A signal with a spectrum as shown in FIG. 5 will not be recorded. When the signal is erased by the luminance FM signal and reproduced, a flat spectrum as shown in FIG. 4 is obtained. Therefore, deterioration of sound quality can be prevented.

Besides the embodiment of FIG. 1, other types are also conceivable.

These other embodiments are shown in FIGS. 6-9. Components that are the same as in FIG. 1 are given the same reference numerals.

In the configuration shown in FIG. 6, each FM modulation circuit (3) (4) outputs a first filter for harmonic removal. 20th upas filter (Lp F
) N2a) (12b), and the first. The second LPF outputs are combined and output to the recording amplifier via the compensation filter means 0J. In the configuration shown in Fig. 7, the first and second
The outputs of the FM modulation circuits (3) and (4) are combined in the adder circuit (111) and then applied to the filter means 03 via the harmonic removal LPF (2). The filter means U may be of any type as long as it has the above-mentioned characteristics in the band of the audio FM signal.In the configuration shown in FIG.
．． The respective outputs of the second FM modulation circuits (3) and (4) are supplied to compensation filter means (13a) and (13b), and after being combined, the outputs are passed through L P F (121) for harmonic removal. There is.

That is, the embodiment shown in FIG. 1 is similar to the embodiment shown in FIGS.
The LPF and filter means are realized by one bandpass filter (7). Note that if the harmonics are not removed by the LPF, they may adversely affect the video band or cause waveform distortion.

Although the above explanation deals with a combination of a video signal and an audio signal, the present invention is not limited to this, and can be applied to all cases where two information signals are recorded and reproduced using the deep recording method. .

(G) Effects of the Invention As described above, the present invention is effective in improving the S/N of deep recorded signals.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a characteristic diagram of a bandpass filter, FIGS. 3, 4, and 5 are explanatory diagrams for explaining the operation, and FIGS. Figure 7, Figure 8, Figure 9
The figure is a block diagram showing another embodiment. (3) (4)... FM modulation circuit, (C... band pass filter (filter means).

Claims (1)

[Claims] (1) A first FM signal obtained by frequency modulating the first carrier signal with the first information signal is recorded to a relatively deep part of the magnetic recording medium, and a first FM signal obtained by frequency modulating the second carrier signal with the second information signal is recorded into a relatively deep part of the magnetic recording medium. A magnetic recording and reproducing device using deep recording that records a 2FM signal in a superimposed manner on the first FM signal, characterized in that a filter means for compensating for erasure of the first FM signal by the second FM signal is disposed in the path of the first FM signal. A magnetic recording and reproducing device.