JPH0722412B2 - Frequency modulation wave recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Use) The present invention is adjacent to a first frequency modulated wave and a low frequency side of a frequency band (hereinafter, simply referred to as a band) occupied by the first frequency modulated wave. The present invention relates to a frequency modulated wave recording apparatus for recording a frequency multiplexed signal with a second frequency modulated wave occupying a predetermined band on a recording medium.

(Summary of the Invention) The present invention records a frequency-multiplexed signal of a first frequency-modulated wave and a second frequency-modulated wave occupying a predetermined band adjacent to the low frequency side of the band of the first frequency-modulated wave. The level of the sideband component that enters the band occupied by the second frequency-modulated wave of the first frequency-modulated wave when amplitude-modulating the first frequency-modulated wave to reinforce the sideband in recording on the medium Is detected and the modulation degree of amplitude modulation of the first frequency-modulated wave is controlled so that the modulation degree becomes smaller as the level increases, so that the second frequency-modulated wave becomes When there is a sideband component that enters the frequency-modulated wave band, the sideband enhancement of the first frequency wave is suppressed, and the interference of the first frequency-modulated wave with the second frequency-modulated wave is reduced. Thing It

(Prior Art) In a helical scan type video tape recorder, in order to improve the quality of an audio signal, a frequency modulation wave is applied to a luminance signal which is a frequency modulation wave and a carrier color signal which is low-frequency converted. The frequency signal is frequency-multiplexed in a predetermined band from the low-frequency part of the luminance signal to the high-frequency part of the low-frequency converted carrier color signal, and the frequency-multiplexed signal is rotated by the rotary magnetic head. There is a method of recording on a track inclined with respect to the running direction of the magnetic tape.

By the way, when a frequency-modulated wave is recorded on a magnetic tape, if the frequency-modulated wave is amplitude-modulated so that the higher the frequency, the smaller the amplitude, when recorded on the tape and reproduced from the tape, the amplitude-modulation changes to the phase modulation. By the conversion effect of
The sideband is strengthened.

FIG. 5 shows a case where the luminance signal is a frequency-modulated wave, and the frequency-modulated wave is amplitude-modulated as described above. The luminance signal Y is supplied to the pre-emphasis circuit 42 to enhance the luminance of the high frequency component. The signal Ye is obtained, and the luminance signal Ye is supplied to the frequency modulation circuit 43, frequency-modulated so that the carrier frequency becomes higher toward the white level side, and the amplitude is kept constant. Yf is obtained.
Then, the frequency modulation wave Yf is supplied to the amplitude modulation circuit 44 and the luminance signal obtained from the pre-emphasis circuit 42.
Due to Ye, the level of the luminance signal Ye is high and the frequency modulated wave
Amplitude modulation is performed such that the higher the frequency of Yf, the smaller the amplitude of the output frequency-modulated wave Ya.

(Problems to be Solved by the Invention) However, as described above, the frequency-modulated wave of the luminance signal and the frequency-modulated wave of the audio signal occupying a predetermined band adjacent to the low frequency side of the frequency-modulated wave of the luminance signal. In the case of recording a frequency-multiplexed signal with and on a magnetic tape, when the frequency modulation wave of the luminance signal is amplitude-modulated and its sideband is enhanced as described above, the frequency modulation wave of the luminance signal is converted into the frequency modulation wave of the audio signal. When there is a sideband component that enters the band, the sideband component is also enhanced, and so-called sound breakup increases.

In view of such a point, the present invention generally provides a frequency-multiplexed signal of a first frequency-modulated wave and a second frequency-modulated wave occupying a predetermined band adjacent to the low-frequency side of the band of the first frequency-modulated wave. When the first frequency modulated wave is amplitude-modulated and its sideband is enhanced by recording the first frequency modulated wave on the recording medium, interference of the first frequency modulated wave with the second frequency modulated wave is reduced. is there.

(Means for Solving the Problems) In the present invention, the level of the sideband component that enters the band of the second frequency-modulated wave of the first frequency-modulated wave is detected to detect at least the first frequency-modulated wave. For a component having a frequency equal to or lower than a predetermined frequency that belongs to the high frequency part, the modulation degree of the amplitude modulation in the amplitude modulation circuit that performs the amplitude modulation is such that the higher the frequency is, the smaller the amplitude is. The higher the band component level, the smaller the control.

(Operation) According to the above configuration, when the first frequency-modulated wave has a sideband component that enters the band of the second frequency-modulated wave, the enhancement of the sideband of the first frequency-modulated wave is suppressed. To be

(Embodiment) FIG. 1 is an example of a frequency-modulated wave recording apparatus according to the present invention, in which a video signal and a 2-channel audio signal are recorded on a track inclined with respect to the running direction of a magnetic tape.

In the audio signal recording system 10, the two-channel audio signals L and R from the audio signal input terminals 11 and 21 are automatically gain control circuit 12,
22 is supplied to the pre-emphasis circuits 14 and 24 through the noise reduction circuits 13 and 23, and the high-frequency component emphasized audio signals Le and Re are obtained from the pre-emphasis circuits 14 and 24. It is supplied to the frequency modulation circuits 15 and 16, and the frequency modulation circuits 15 and 16 perform frequency modulation with the audio signals Le having center frequencies of f ₁ and f ₂ , respectively, and the frequency modulation circuits 15 and 16 output audio signals Le. Frequency modulated wave of La, Lb
Is obtained, and the audio signal Re is supplied to the frequency modulation circuits 25 and 26, and the frequency modulation circuits 25 and 26 perform frequency modulation with the central frequencies f ₃ and f ₄ by the audio signal Re, respectively, and perform frequency modulation. Frequency modulated waves Ra and Rb of the audio signal Re are obtained from the circuits 25 and 26.

Here, as shown in FIG. 2, the predetermined band Ba extends from the low-frequency part of the frequency-modulated wave Yf of the luminance signal, which will be described later, to the high-frequency part of the low-frequency-converted carrier color signal Cl. The bands of the modulated waves La, Lb, Ra, and Rb are set, and the above-mentioned f _{1 to} f ₄ are set in this band Ba. However, as shown in the figure, f ₁ <f ₂
<A f ₃ <f _4. As an example, f ₁ = 1.38MHz, f ₂ = 1.53MH
z, f ₃ = 1.68MHz, f ₄ = 1.83MHz, frequency modulated wave La, L
The maximum frequency deviation of b, Ra and Rb is ± 50kHz to ± 75kHz.

Then, the audio signal Le, obtained from the frequency modulation circuits 15 and 25,
The frequency-modulated waves La and Ra of Re are supplied to the synthesis circuit 19 through the bandpass filters 17 and 27 having center frequencies f ₁ and f ₃ , and the frequency-modulated waves La and Ra of the audio signals Le and Re of the sound signals Le and Re are supplied from the synthesis circuit 19. A frequency-multiplexed signal is obtained, and the frequency-modulated waves Lb and Rb of the audio signals Le and Re obtained from the frequency modulation circuits 16 and 26 have center frequencies
It is supplied to the synthesizing circuit 29 through the band pass filters 18 and 28 for f ₂ and f ₄ , and the synthesizing circuit 29 obtains the frequency-multiplexed signals of the frequency modulated waves Lb and Rb of the audio signals Le and Re.

In the video signal recording system 30, the video signal from the video signal input terminal 31 is supplied to the low pass filter 41, and the luminance signal Y is taken out from the low pass filter 41.
Is supplied to the pre-emphasis circuit 42 to obtain a luminance signal Ye in which the high frequency component is emphasized as shown in FIG. 3, and this luminance signal Ye is supplied to the frequency modulation circuit 43 so that the luminance signal Ye Frequency modulation is performed in which the frequency is increased toward the white level side, and a frequency modulated wave Yf in which the amplitude of the luminance signal Ye is constant is obtained. As an example, the luminance signal
The frequency fw of the frequency modulation wave Yf at the white peak of Ye is 5.
The frequency fs of the frequency-modulated wave Yf at the sync signal tip of the luminance signal Ye is set to 4.0 MHz, so that the intermediate frequency between the two is set to 4.6 MHz. In addition, in FIG.
Lp is the white peak level of the luminance signal Ye.

The frequency modulation wave Yf is supplied to the amplitude modulation circuit 44 and is amplitude modulated. In this example, the amplitude of the frequency-modulated wave Yf is modulated so that the amplitude of the frequency-modulated wave after amplitude modulation becomes extremely small at a high frequency and the inversion phenomenon does not easily occur in the process of recording and reproducing. When the frequency of the frequency modulated wave Yf is less than or equal to the predetermined frequency, the higher the frequency of the frequency modulated wave Yf, the smaller the amplitude becomes.However, when the frequency of the frequency modulated wave Yf is equal to or higher than the predetermined frequency, the frequency modulation is reversed. This is a case where the wave Yf is made non-linear so that the higher the frequency, the larger the amplitude.

That is, the luminance signal Ye obtained from the pre-emphasis circuit 42 is level-adjusted by the level adjuster 51 and supplied to the subtraction circuit 52. Further, the luminance signal Ye is supplied to the slicing circuit 53, and the component of the luminance signal Ye having a level higher than the white peak level is sliced.
The level of Se is adjusted by the level adjuster 54, and the subtraction circuit
Supplied to 52. Then, in the subtraction circuit 52, the slice signal Se whose level has been adjusted by the level adjuster 54 is subtracted from the brightness signal Ye whose level has been adjusted by the level adjuster 51, and the subtraction circuit 52 outputs the brightness as shown in FIG. signal
The voltage Vs when the part of the level above the white peak level of Ye is reversed to the level below the white peak level
This voltage Vs is supplied to the voltage control amplifier circuit 55, and the output voltage Vc of the voltage control amplifier circuit 55 is the amplitude modulation circuit.
Supplied to 44. The amplitude modulation circuit 44 is a voltage control amplifier circuit, and the voltage Vc of the output of the voltage control amplifier circuit 55 is used as a gain control voltage, and the gain is controlled so that the gain decreases as the voltage Vc increases.

Therefore, when the level of the luminance signal Ye is equal to or lower than the white peak level and the frequency of the frequency-modulated wave Yf is equal to or lower than the predetermined frequency fw, as shown by the solid line 1a in FIG. The higher the frequency of the wave Yf, the more amplitude-modulated frequency-modulated wave Ya obtained from the amplitude modulation circuit 44.
However, when the level of the luminance signal Ye is equal to or higher than the white peak level and the frequency of the frequency modulation wave Yf is equal to or higher than the predetermined frequency fw, as shown by the solid line 1b in FIG. The higher the level of Ye and the higher the frequency of the frequency-modulated wave Yf, the larger the amplitude of the amplitude-modulated frequency-modulated wave Ya obtained from the amplitude modulation circuit 44. That is,
The amplitude of the amplitude-modulated frequency-modulated wave Ya obtained from the amplitude modulation circuit 44 becomes the minimum at the predetermined frequency fw, and becomes larger than the amplitude at the predetermined frequency fw at the frequency exceeding the predetermined frequency fw.

Then, the amplitude-modulated frequency-modulated wave Ya obtained from the amplitude modulation circuit 44 is supplied to the bandpass filter 56, and the sideband that enters the band Ba of the audio signal of the frequency-modulated wave Ya from the bandpass filter 56. The component is taken out, this sideband component is supplied to the level detection circuit 57, and the voltage Vd corresponding to the level of the sideband component that enters the band Ba of the audio signal of the frequency modulated wave Ya is obtained from the level detection circuit 57. The voltage Vd is supplied to the voltage control amplifier circuit 55 described above. The voltage control amplifier circuit 55 uses the output voltage Vd of the level detection circuit 57 as a gain control voltage and a subtraction circuit.
When the voltage Vs obtained from 52 is a value corresponding to a level just between the white peak level of the luminance signal Ye obtained from the pre-emphasis circuit 42 and the sync signal tip level, the output voltage Vc is set to that value. Thus, the gain is controlled such that the larger the voltage Vd, the smaller the gain.

Therefore, the carrier frequency at the white peak of the luminance signal Ye
fw and the carrier frequency fs at the tip of the sync signal, the amplitude at the frequency fc just in the middle of the carrier frequency fs does not change, and the modulation degree of the amplitude modulation in the amplitude modulation circuit 44 is the frequency modulation for the audio signal of the frequency modulation wave Yf. Depending on the level of the sideband component that enters the band Ba of the waves La, Lb, Ra, Rb, the degree of modulation is controlled to decrease as the level increases. That is, when the level of the sideband component that enters the frequency modulation wave La, Lb, Ra, or Rb band Ba of the audio signal of the frequency modulation wave Yf is small and the voltage Vd of the output of the level detection circuit 57 is small, The gain of the control amplifying circuit 55 is increased so that the amplitude modulating circuit 55 is formed as indicated by broken lines 2a and 2b in FIG.
The modulation depth of the amplitude modulation at 44 is increased and the frequency modulation wave Yf
Band B of frequency-modulated waves La, Lb, Ra, and Rb for the voice signal of
When the level of the sideband component entering a is large and the voltage Vd of the output of the level detection circuit 57 is large, the gain of the voltage control amplifier circuit 55 is reduced, and as shown by chain lines 3a and 3b in FIG. The modulation degree of the amplitude modulation in the amplitude modulation circuit 44 is reduced. Therefore, when there is a sideband component in the frequency-modulated wave Yf that enters the frequency-modulated wave La, Lb, Ra, or Rb band Ba of the audio signal, the enhancement of the sideband of the frequency-modulated wave Yf is suppressed. The number of breaks does not increase.

The amplitude-modulated frequency-modulated wave Ya obtained from the amplitude-modulation circuit 44 is supplied to the band attenuation filter 45, and the frequency-modulated wave La, Lb, for the above-described audio signal of the frequency-modulated wave Ya.
Sideband components that enter the band Ba of Ra and Rb are attenuated, and the amplitude-modulated frequency-modulated wave Yo of the output of the band attenuation filter 45 is supplied to the combining circuit 32.

Further, the video signal from the video signal input terminal 31 is supplied to the bandpass filter 61, the carrier color signal C having the color subcarrier frequency fsc = 3.58 MHz is taken out from the bandpass filter 61, and the carrier color signal C is obtained. Automatic color signal level control circuit 62
Is supplied to the frequency conversion circuit 63 through the low frequency conversion carrier color signal Cl having the color subcarrier frequency fl and the high frequency conversion carrier color signal Ch having the color subcarrier frequency 2fsc + fl. Signals Cl and Ch are low pass filters 64
Is supplied to the low-pass filter 64, the low-pass-converted carrier color signal Cl is extracted, and the carrier color signal Cl is supplied to the synthesizing circuit 32, and the frequency modulation wave Yo and the carrier color signal Cl are supplied from the synthesizing circuit 32. The frequency-multiplexed signal of is obtained. Note that fl is set to about 0.69 MHz, for example.

Then, a frequency multiplexed signal of the frequency modulated wave Yo and the carrier color signal Cl obtained from the synthesizing circuit 32 is supplied to the synthesizing circuit 71,
Further, the frequency-multiplexed signals of the frequency modulation waves La and Ra of the audio signals Le and Re obtained from the above-mentioned synthesis circuit 19 are supplied to the synthesis circuit 71, and the synthesis circuit 71 outputs the frequency modulation wave Yo and the carrier color signal Cl.
And a frequency-multiplexed signal of the frequency-modulated waves La and Ra of the audio signals Le and Re are obtained, and this frequency-multiplexed signal is supplied to the rotary magnetic head 73 through the recording / amplifying circuit 72, and the head 73 moves in the tape traveling direction. It is recorded on every other inclined track. Further, a frequency multiplexed signal of the frequency modulated wave Yo and the carrier color signal Cl obtained from the synthesizing circuit 32 is a synthesizing circuit.
The frequency-multiplexed signal of the frequency-modulated waves Lb and Rb of the audio signals Le and Re, which are supplied to the synthesis circuit 29, are supplied to the synthesis circuit 81, and the frequency-modulated wave Yo and the carrier color are supplied from the synthesis circuit 81. A frequency-multiplexed signal of the signal Cl and the frequency-modulated waves Lb, Rb of the audio signals Le, Re is obtained, and this frequency-multiplexed signal is supplied to the rotary magnetic head 83 through the recording / amplifying circuit 82, and the head 83 causes the tape running direction. Is recorded on every other track that is tilted with respect to. Rotating magnetic head 73 and
The 83 are attached to each other at an angular interval of 180 degrees and have different azimuth angles.

The amplitude modulation characteristic of the frequency modulation wave Yf in the amplitude modulation circuit 44 is
When the frequency of the frequency modulated wave Yf is equal to or lower than the predetermined frequency, the higher the frequency of the frequency modulated wave Yf, the smaller the amplitude becomes.
When the frequency of the frequency modulated wave Yf is equal to or higher than the predetermined frequency, the amplitude may be constant regardless of the frequency of the frequency modulated wave Yf. Further, if the inversion phenomenon is not a problem, it may be linear so that the amplitude becomes smaller as the frequency of the frequency modulation wave Yf becomes higher.

(Effect of the Invention) According to the present invention, a frequency-multiplexed signal of a first frequency-modulated wave and a second frequency-modulated wave occupying a predetermined band adjacent to the low frequency side of the band of the first frequency-modulated wave When the first frequency modulated wave is amplitude-modulated to reinforce the sideband in recording the recording medium on the recording medium, a sideband component that enters the band occupied by the second frequency modulated wave of the first frequency modulated wave Is detected and the modulation degree of the amplitude modulation of the first frequency modulated wave is controlled so that the higher the level is, the smaller the modulation degree is. When there is a sideband component that enters the band of the second frequency modulation wave, the enhancement of the sideband of the first frequency modulation wave is suppressed,
The interference of the first frequency modulated wave with the second frequency modulated wave is reduced.

[Brief description of drawings]

FIG. 1 is a connection diagram showing an example of a frequency-modulated wave recording apparatus according to the present invention, FIG. 2 is a diagram showing an example of a frequency spectrum of a recording signal, FIG. 3 is a diagram showing waveforms of respective parts, and FIG. FIG. 5 is a diagram showing an example of an amplitude modulation characteristic, and FIG. 5 is a connection diagram showing an example of a conventional modulator that amplitude-modulates a frequency-modulated wave. In the figure, 31 is a video signal input terminal, Y is a luminance signal, and 43 is a first
Frequency modulation circuit, 44 is an amplitude modulation circuit, C is a carrier color signal, 11 and 12 are audio signal input terminals, L and R are audio signals, 15, 16 and
25 and 26 are second frequency modulation circuits, 55 is a voltage control amplifier circuit, 56 is a band pass filter, and 57 is a level detection circuit.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H04N 9/802

Claims (1)

[Claims] 1. A first frequency modulation circuit formed on the basis of a first signal to obtain a first frequency modulated wave occupying a predetermined frequency band, and a first frequency modulation circuit formed on the basis of a second signal, A second frequency modulation circuit for obtaining a second frequency modulation wave occupying a frequency band adjacent to the low frequency side of the frequency band occupied by the frequency modulation wave, and at least a frequency equal to or lower than a predetermined frequency in the first frequency modulation wave. An amplitude modulation circuit that performs amplitude modulation of a component that has a smaller amplitude as the frequency of the component has a higher frequency, and enters the frequency band of the second frequency modulation wave of the first frequency modulation wave. The level detection unit for detecting the level of the sideband component and the modulation degree of the amplitude modulation in the amplitude modulation circuit are smaller as the level detected by the level detection unit is larger. And a recording unit for synthesizing the first frequency-modulated wave and the second frequency-modulated wave that have been amplitude-modulated by the amplitude modulation circuit and recording them on a recording medium. A recording device for frequency-modulated waves, which comprises: