JP2772177B2 - Color signal recording / reproducing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color signal recording / reproducing system.

[0002]

2. Description of the Related Art The configuration of a recording system and a reproducing system in a conventional color signal recording / reproducing NTSC system are shown in FIGS. 5 and 6, respectively. In addition, FIGS. 7 (a), (b),
(C), (d) and (f) are diagrams showing the frequency spectrum of each signal in the conventional example.

In the case of a recording system, in FIG. 5, only the carrier chrominance signal of the luminance signal and the carrier chrominance signal inputted from the input terminal 67 is extracted by the bandpass filter 29 and inputted to the frequency converter 30. At the same time, only the burst signal of the carrier chrominance signal is input to the phase comparator 32 via the burst gate circuit 31, and the voltage controlled oscillator (hereinafter, V
The oscillation output signal of the VCO 33 is controlled by an output voltage corresponding to the phase difference, and an oscillation output signal (frequency f _SC ) synchronized with the burst signal is output. , Are input to the frequency converter 38.

On the other hand, the oscillation output signal of the VCO 35 is compared in the frequency comparator 34 with a horizontal synchronizing signal (functioning as a reference signal) inputted from an input terminal 68, and a frequency difference between the two signals is obtained. The oscillation frequency of the VCO 35 is controlled via the corresponding correction voltage, an oscillation output signal corresponding to the frequency of the horizontal synchronization signal is output, and the frequency divider 36 divides the frequency by 1 / n (n is a positive integer) ( Frequency f _LC ), frequency converter 38 via phase shift circuit 37
Is input to

[0005] From the frequency converter 38, two signals having frequencies obtained by adding and subtracting the frequencies of the two signals input from the VCO 33 and the phase shift circuit 37 are output and input to the bandpass filter 39. Via 39, the frequency of the high frequency component (f _SC + f _LC = f _C )
Are selected and output, and input to the frequency converter 30. In the frequency converter 30, the carrier chrominance signal (frequency f _SC ) input from the bandpass filter 29 is used.
And the frequency of two signals of the signal (frequency f _C ) output from the bandpass filter 39 are added and subtracted and output.
Via the low-pass filter 40, the frequency (f
_The low-frequency conversion color signal corresponding to ( _C− f _SC ) is extracted and output via the output terminal 69.

At the time of reproduction, in the reproduction system shown in FIG. 6, the reproduction low-frequency conversion color signal (reproduction low-frequency conversion color signal) out of the FM-modulated reproduction luminance signal and reproduction low-frequency conversion color signal input from the input terminal 70. Only the frequency f _SL ) is the low-pass filter 41
And input to the frequency converter 42. On the other hand, the oscillation output signal of the VCO 44 is compared with the reproduced horizontal synchronizing signal input from the input terminal 71 in the side lock prevention circuit 43, and the VCO 44 is output via the correction voltage corresponding to the frequency difference between the two signals. Is output, an oscillation output signal corresponding to the frequency of the horizontal synchronizing signal is output, the frequency is divided by 1 / n in the frequency divider 45, and the reproduced low-frequency converted carrier wave signal is outputted through the phase shift circuit 46. (Frequency f _LC ) is input to the frequency converter 47. An oscillation output signal (frequency f _SC ) of the oscillator 53 is also input to the frequency converter 47 as another input signal, and the frequencies of these two signals are added and subtracted and output. The signal corresponding to the frequency of the high frequency component (f _SC + f _LC = f _C ) is extracted through the frequency converter 42 and input to the frequency converter 42.

The frequency converter 42 has two signals, the reproduced low-frequency converted chrominance signal (frequency f _SL ) input from the low-pass filter 41 and the signal (frequency f _C ) input from the band-pass filter 48. the output frequency of the is subtraction, via a bandpass filter 49, the reproduced carrier chrominance signal corresponding to the low-frequency component of the frequency _{(f C -f SC = f S} ) is extracted, via the comb filter circuit 50 Output terminal 69
Is output via. In this case, the comb filter circuit 5
Only the burst signal in the reproduced carrier chrominance signal output from 0 is input to the phase comparator 52 via the burst gate circuit 51, and the phase comparator 52 compares the phase with the oscillation output signal of the oscillator 53. A signal synchronized with the frequency of the burst signal is output from the VCO 44 via a phase difference voltage corresponding to the phase difference between the two signals.
It is input to the frequency converter 47.

That is, at the time of recording, the carrier color signal is converted into a low-frequency conversion color signal, and at the time of reproduction, the reproduced color signal is converted into a reproduced carrier color signal.

[0009]

In the above-mentioned conventional color signal recording / reproducing method, FIGS.
As shown in the frequency spectra of (c), (d), (e) and (f), in the recording system, the carrier color signal input to the low-pass filter 40 via the frequency converter 30 is: components but (f _C -f _SC) and has two of the frequency spectrum of (f _C + f _SC) (see FIG. 7 (a)), the frequency of the (f _C + f _SC) is not required For,
It needs to be removed by the low-pass filter 40. However, since these two frequency spectrums are located at a considerable distance (about 7.2 MHz), the characteristics of the low-pass filter are relatively low as shown in FIG. 7B. Anything having a gradual frequency characteristic may be used.

On the other hand, in the reproducing system, the frequency converter 4
7 has two frequency spectra of (f _C −f _SL ) and (f _C + f _SL ) (FIG. 7C). )), A component of a desired frequency (f _C −f _SC ) therein,
An unnecessary frequency component (f _C −f _SC ) is separated from the frequency component by at most about 2 f _SL (about 1.26 MHz). Therefore, as shown in FIG. 7D, a sharp cutoff characteristic is required as the band frequency characteristic of the band filter 49. Therefore, the characteristic of the band filter 49 must be a narrow band pass characteristic, and the frequency component of the reproduced carrier color signal is partially deleted, which is a major factor of image quality deterioration such as color blur in the reproduced image. There is.

In both the recording system and the reproducing system, the signals output from the frequency conversion circuits 39 and 48 include two frequency spectra of (f _SC -f _LC ) and (f _SC + f _LC ). (See FIG. 7 (e)).
The component of the desired frequency (f _SC + f _LC ) and the component of the unnecessary frequency (f _SC −f _LC ) have a frequency of at most 2f _LC.
(About 1.26 MHz).
Therefore, as shown in FIG. 7F, a sharp cutoff characteristic is required for the band frequency characteristics of the bandpass filters 39 and 48. Therefore, the above-described bandpass filter 49
As in the case of (1), the characteristics of the band filters 39 and 48 are narrow band-pass characteristics. In general, the incorporation of a bandpass filter having such frequency characteristics in a semiconductor integrated circuit has a drawback that it increases the number of external components and the number of pins, which is a hindrance to semiconductor integration.

[0012]

A color signal recording / reproducing method according to the present invention comprises: means for receiving a carrier chrominance signal composed of a first frequency component and extracting a burst signal contained therein; The first synchronized with the phase of the signal
A first oscillation circuit for generating a phase correlation signal, a second oscillation circuit for receiving a horizontal synchronization signal and generating a second phase correlation signal synchronized with the phase of the signal, the carrier color signal and the first A first and a second frequency components, each of which is lower than the first frequency and includes 0, which are lower than the first frequency and demodulated the carrier chrominance signal via the first phase correlation signal. A demodulation circuit for generating a color difference signal of
A first low-pass filter that receives the first color difference signal and removes a harmonic signal contained therein, and a second low-pass filter that receives the second color difference signal and removes a harmonic signal contained therein And receiving the first and second color difference signals from which the harmonic signal has been removed and the second phase correlation signal, and removing the harmonic signal via the second phase correlation signal. A modulation circuit for generating a low-frequency carrier chrominance signal composed of a third frequency component lower than the first frequency and higher than the second frequency obtained by quadrature quadrature-modulating the first and second color difference signals; At least as a recording system.

Further, the color signal recording / reproducing method of the present invention comprises:
A first oscillation circuit for generating an oscillation output signal composed of a first frequency component, a reproduced low-frequency carrier color signal composed of a second frequency component lower than the first frequency, and the oscillation output signal And a first frequency converter for generating a converted signal obtained by converting the carrier frequency of the reproduced low-frequency carrier chrominance signal via the oscillation output signal; A second oscillating circuit for generating a phase correlation signal, a second oscillation circuit receiving the oscillation output signal and the first phase correlation signal, and converting the frequency of the first phase correlation signal via the oscillation output signal. A second frequency converter that generates the phase correlation signal of the second and the second frequency converter that receives the conversion signal and the second phase correlation signal, and demodulates the conversion signal via the second phase correlation signal. Than frequency A demodulation circuit for generating first and second color difference signals composed of a third frequency component including zero, and a first low-frequency signal receiving the first color difference signal and removing a harmonic signal contained therein. A high-pass filter, a second low-pass filter that receives the second color difference signal and removes a harmonic signal contained therein, the first and second color difference signals from which the harmonic signal is removed, and the oscillation An output signal, and a reproduced carrier color signal composed of the first frequency component obtained by quadrature quadrature modulating the first and second color difference signals from which the harmonic signal has been removed via the oscillation output signal. And a modulating circuit that generates the signal as at least a reproduction system.

[0014]

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a recording system according to an embodiment of the present invention. As shown in FIG. 1, the reproduction system of the present embodiment includes a bandpass filter 1, a demodulation circuit 2, a burst gate circuit 3, a phase comparison circuit 4, VCOs 5 and 10, low-pass filters 6, 7 and 13, a modulation circuit 8, a frequency comparison circuit 9, a frequency divider 11, and a phase shift circuit 12. In addition, FIG.
(B), (c), (d) and (f) are diagrams showing the frequency spectrum of each signal in the present reproduction system.

At the time of recording, a carrier chrominance signal (frequency f _SC : see FIG. 3A) extracted from the input terminal 61 via the bandpass filter 1 is input to the demodulation circuit 2 and a burst gate circuit. 3 is input. From the carrier chrominance signal (frequency f _SC ) input to the burst gate circuit 3, only the burst signal is extracted and output, and is input to the phase comparison circuit 4. The oscillation output signal of the VCO 5 is input to the phase comparison circuit 4, a phase comparison with the burst signal is performed, a voltage corresponding to the phase difference is output, and the voltage is input as a control signal for the VCO 5. . Thereby, the oscillation output signal of the VCO 5 is synchronized with the phase of the burst signal, and the frequency f _SC
(See FIG. 3 (b)) and output from the demodulation circuit 2
Is input to

In the demodulation circuit 2, the carrier chrominance signal (frequency f _SC ) output from the bandpass filter 1 is applied to the VCO
5 is demodulated through the signal output from the signal 5, and a color difference signal including two harmonic signals is output. The color difference signal is input to the low-pass filter 6 and the low-pass filter 7 (see FIG. 3D for the pass characteristics). Is done. In the low-pass filters 6 and 7, the harmonic signals are removed, and the color difference signals (frequency f _S1 ,
f _S2 ) is extracted and input to the modulation circuit 8. On the other hand, the oscillation output signal of the VCO 10 is compared in frequency with the horizontal synchronizing signal input from the input terminal 62 in the frequency comparator 9, and is oscillated by the VCO 10 via a correction voltage corresponding to the frequency difference between the two signals. The frequency is controlled, an oscillation output signal corresponding to the frequency of the horizontal synchronizing signal is output, the frequency is divided by 1 / n in the frequency divider 11, and the low-frequency converted carrier signal (frequency f _LC : FIG. ) And input to the modulation circuit 8 via the phase shift circuit 12. In the modulation circuit 8, the low-pass conversion carrier signal input from the phase shift circuit 12 is converted into a quadrature signal via the two color difference signals (frequency f _S1 , f _S2 ) input from the low-pass filters 6 and 7. It is phase-modulated and output as a low-frequency conversion carrier color signal. Since the low-frequency conversion carrier chrominance signal contains unnecessary harmonic signals, these high-frequency signal components are removed by the low-pass filter 13 (refer to FIG. 3E for the pass characteristic). Thus, only the low-frequency conversion carrier color signal component is output via the output terminal 63.

Accordingly, the output terminal 63 outputs a low-frequency conversion color signal obtained by frequency-converting the carrier color signal.

FIG. 2 is a block diagram showing a reproducing system according to one embodiment of the present invention. As shown in FIG.
The reproduction system of this embodiment includes a low-pass filter 14, frequency converters 15 and 22, a demodulation circuit 16, a side lock prevention circuit 17, a VCO 18, a frequency divider 19, a phase shifter 20, an oscillator 21 and low-pass filters 23 and 24
, A modulation circuit 25, a comb filter 26, a burst gate circuit 27, and a phase comparison circuit 28. 4 (a), (b), (c) and (d)
FIG. 3 is a diagram showing a frequency spectrum of each signal in the present reproduction system.

At the time of reproduction, the reproduced low-frequency conversion chrominance signal (frequency f _S1 ) extracted from the input terminal 64 via the bandpass filter 1 is input to the frequency converter 15 and the oscillator 2
(F _SC + f) via the oscillation output signal (frequency f _SC )
_The signal is converted into an intermediate-frequency reproduction conversion color signal (see FIG. 4A) having two frequency spectra of ( _SL ) and (f _SC -f _SL ) and input to the demodulation circuit 16. On the other hand, VCO18
Of the oscillation output signal of the VCO 18 is compared with the reproduced horizontal synchronizing signal inputted from the input terminal 75 in the side lock prevention circuit 17 and the oscillation frequency of the VCO 18 is corrected via the correction voltage corresponding to the frequency difference between the two signals. Is controlled, an oscillation output signal corresponding to the frequency of the reproduced horizontal synchronizing signal is output, the frequency is divided by 1 / n in the frequency divider 19, and the reproduced low frequency conversion carrier signal (frequency f _SL ) is input to the frequency converter 22. For the frequency converter 22, as another input signal,
The oscillation output signal (frequency f _SC ) of the oscillator 21 is also input. According to the difference between the frequencies of these two signals, (f _SC
The signal is converted into an intermediate frequency carrier signal having two frequency spectra of + f _SL ) and (f _SC -f _SL ), and is input to the demodulation circuit 16. In the demodulation circuit 16, the reproduced low-frequency converted color signal extracted through the bandpass filter 1 is demodulated through the intermediate frequency carrier signal, and a reproduced color signal including two harmonic signals is output. Low-pass filters 23 and 24 (see FIG. 4D for the pass characteristics)
Is input to In the low-pass filters 23 and 24, the harmonic signals are removed, and only the reproduced color difference signals (frequency f _S1 , f _S2 : see FIG. 4C) are extracted and input to the modulation circuit 25. In the modulation circuit 25, the oscillation output signal (frequency f _SC ) of the oscillator 21 is subjected to quadrature two-phase modulation via the two reproduced color difference signals (frequency f _S1 , f _S2 ) input from the low-pass filters 23 and 24. Then, the signal is output as a reproduced carrier chrominance signal (frequency f _SC : see FIG. 4C) via the comb filter 26 via the output terminal 66. Of the reproduced carrier color signals, only the burst signal is input to the phase comparison circuit 28 via the burst gate circuit 27, and the oscillation output signal (frequency f
_SC ) and the voltage corresponding to the phase difference is
It is input to the VCO 18 as a phase control signal. Therefore, the oscillation output signal of the VCO 18 is input to the frequency divider 19 as a signal synchronized with the phase of the burst signal output from the burst gate circuit 27.

The phase comparison circuit 28 compares the phase of the burst signal arriving intermittently via the burst gate circuit 27 with the phase of the continuous wave sent from the oscillator 21 to determine the oscillation frequency of the VCO 18. Due to the control function, the oscillation frequency of the VCO 18 may be in a synchronized state (side-locked state) at an erroneous frequency shifted from the normal value by an integral multiple of the horizontal synchronization frequency. The side lock prevention circuit 17 is a circuit for correcting the side lock state of the VCO 18, and is a circuit for fixing the oscillation frequency of the VCO 18 to a predetermined dispersion using the reproduced horizontal synchronization signal input from the input terminal 65 as a reference signal. is there. As a result, a reproduced carrier color signal (frequency f _SC ) obtained by frequency-converting the reproduced low-frequency converted color signal is generated from the output terminal 66.

[0022]

As described above, according to the present invention, the carrier chrominance signal is demodulated and subjected to chrominance signal processing, and the quadrature two-phase modulation is performed through a predetermined phase correlation signal, thereby obtaining the carrier chrominance signal. Since the band can be held in a wide band, the image quality of the reproduced image can be maintained well because the band spectrum of the carrier chrominance signal is not suppressed without the need for a narrow band band-pass filter. effective.

Further, since the above-mentioned band filter is not required, the number of external parts and the number of pins can be reduced, and the effect of inhibiting the integration of the semiconductor can be eliminated.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a recording system according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a reproducing system according to one embodiment of the present invention.

FIG. 3 is a diagram showing a frequency spectrum of each signal in the recording system.

FIG. 4 is a diagram showing a frequency spectrum of each signal in the reproduction system.

FIG. 5 is a block diagram showing a conventional recording system.

FIG. 6 is a block diagram showing a conventional reproduction system.

FIG. 7 is a diagram showing a frequency spectrum of each signal in a conventional example.

[Explanation of symbols]

1, 29, 39, 48, 49 Bandpass filter 2, 16 Demodulation circuit 3, 27, 31, 51 Burst gate circuit 4, 28, 32, 52 Phase comparison circuit 5, 10, 18, 33, 35, 44 VCO 6, 7, 13, 14, 23, 24, 40, 41 Low-pass filter 8, 25 Modulation circuit 9, 34, 52 Frequency comparison circuit 11, 19, 36, 45 Divider 12, 20, 37, 46 Phase transition circuit 15 , 22,30,38,42,47 Frequency converter 17,43 Side lock prevention circuit 21,53 Oscillator 26,50 Comb filter

Claims (2)

(57) [Claims] 1. A carrier constituted by a first frequency component.
A means for receiving a color signal and extracting a burst signal contained in the color signal
And a second stage synchronized with the phase of the extracted burst signal.
A first oscillation circuit for generating a phase correlation signal
Second phase correlation synchronized with the phase of this signal
A second oscillation circuit for generating a signal, the carrier color signal and
Receiving the first phase correlation signal; the first phase correlation signal;
The carrier chrominance signal is demodulated through
The second frequency component including 0 which is lower than the frequency of
Demodulation circuit for generating first and second color difference signals to be formed
And a harmonic signal included in the first color difference signal.
A first low-pass filter for removing a signal, and a second color difference signal.
And a second low-pass filter for receiving and removing harmonic signals contained therein.
A high-pass filter and the first and second filters from which the harmonic signal has been removed.
And a second color difference signal and the second phase correlation signal,
Removing the harmonic signal via the second phase correlation signal
Quadrature two-phase modulation of the first and second color difference signals
Lower than the first frequency and lower than the second frequency
Low-frequency carrier signal composed of a third frequency component having a high frequency
At least as a recording system
A color signal recording / reproducing method, characterized in that: 2. An oscillation constituted by a first frequency component.
A first oscillation circuit for generating an output signal;
A playback frequency comprised by a second frequency component lower than the number;
Receiving the gamut carrier color signal and the oscillation output signal,
The carrier frequency of the reproduced low-frequency carrier chrominance signal via a force signal
A first frequency converter that generates a converted signal obtained by converting
The first position which receives the horizontal synchronization signal and is synchronized with the phase of this signal
A second oscillation circuit for generating a phase correlation signal;
Receiving the signal and the first phase correlation signal;
Converting the frequency of said first phase correlation signal via a signal
Frequency converter for generating a second phase correlation signal
And receiving the converted signal and the second phase correlation signal,
Demodulating the converted signal via the second phase correlation signal
Each of the third frequencies including 0 lower than the second frequency.
The first and second color difference signals composed of frequency components are
And a demodulation circuit for generating the first color difference signal.
A first low-pass filter for removing contained harmonic signals;
The second color difference signal is received and a harmonic signal contained therein is received.
A second low-pass filter for eliminating, before Symbol harmonic signal is removed
The first and second color difference signals and the oscillation output signal
Signal, and the harmonic signal is obtained via the oscillation output signal.
Quadrature two-phase modulation of the removed first and second color difference signals
Reproduced carrier color constituted by the first frequency component
A modulation circuit for generating a signal is provided at least as a reproduction system.
Color signal recording / reproducing method.