KR800001581B1 - Frequency conversion circuit of chrominance signal - Google Patents

Abstract

In a VTR system, the conversion cct. could eliminate the dispersion of tint at the beginning of field. The cct. includes a variable frequency oscillator(31). The signals for frequency conversion to the carrier color signals are produced by the signals from the oscillator(31) and the carrier color signals are converted into frequency mode by the signals for frequency conversion. Whenever the track is selected, oscillation frequency of the oscillator is changed to frequency interleave at the adjacent tracks each other.

Description

Frequency conversion circuit of carrier color signal

1 to 6 illustrate a special recording and reproducing method of a color video signal.

1 shows a rotating magnetic head arrangement.

2 is a view showing a state of magnetic voids of the rotating magnetic head.

3 shows a recording pattern on a magnetic tape.

4 is a schematic diagram of a recorder.

5 is a schematic diagram of a regeneration system.

6 shows a frequency spectrum for explanation thereof.

7 is a waveform diagram for explaining the present invention.

8 is a system diagram showing one example of the circuit of the present invention.

When recording a color video signal on magnetic tape or the like, the recording density can be greatly increased by the following method.

That is, when recording on the magnetic tape, as shown in FIG. 1, two rotating magnetic heads H _A and H _B are attached at an angle interval of 180 degrees, and the tape 1 is attached to the tape guide drum 2. ) Runs roughly over an angle range of 180 degrees, but as shown in FIG. 2, the gaps G _A and g _B of the heads H _A and H _B with respect to the scanning direction indicated by arrows (3). Different angles of inclination Then, the heads H _A and H _B are rotated once in one frame, for example, and as shown in FIG. 3, the tracks T _A and T _B are alternately formed every head as the heads H _A and H _B.

만큼 다른 f_S+f_B라는 주파수의 신호를 공급하여, 스위치회로(17)를, 절환신호 SC에 의하여 헤드 H_A가 테이프(1)에 대접하는 피일드에 있어서의 도면의 상태로 절환하여 이것에 의하여 f_S+f_A라는 주파수의 신호를 취출하고, 헤드 H_B가 테이프(1)에 대접하는 피일드에 있어서는 도면의 상태와는 반대의 상태로 절환하여 이것에서 f_S+f_B라는 주파수의 신호를 취출하여, 이것을 주파수 변환기(16)에 공급한다. 따라서, 주파수 변환기(16)로부터는, 헤드 H_A가 테이프(1)에 대접하는 피일드에서는, 부반송파의 주파수가 f_A로 된 반송색신호 CA가 얻어지고, 헤드 H_B가 테이프(1)에 대접하는 피일드에서는, 부반송파의 주파수가 f_A로 된 반송색신호 CA가 얻어지고, 헤드 H_B가 테이프(1)에 대접하는 피일드에서는, 부반송파의 주파수가 f_B로 된 반송색신호가 얻어진다. 이 반송색신호 CA,CB는 합성기(14)에 공급하여, 피변조 휘도신호와 합성하여, 그 합성출력을 암프(18)를 통해서 헤드 H_A및 H_B에 공급한다.In this case, in recording, as shown in FIG. 4, the color image signal from the input terminal 11 is supplied to the low pass filter 12 to obtain a luminance signal, which is supplied to the frequency modulator 13, A modulated luminance signal occupying the high frequency side of the recordable / reproducible frequency band is obtained and supplied to the synthesizer 14. The input color video signal is further supplied to the band pass filter 15 to take out a carrier signal whose frequency of the subcarrier is f _S , which is supplied to the frequency changer 16 to perform frequency conversion on the low frequency side. In this case, one input terminal of the switch circuit 17 is supplied with a signal of frequency f _S + f _A , while the other input terminal has a horizontal frequency of f _H.

The signal of the frequency f _S + f _B is supplied differently, so that the switch circuit 17 is switched to the state of the drawing in the feed where the head H _A serves the tape 1 by the switching signal SC. By taking out the signal of the frequency f _S + f _A and switching to the state opposite to the state shown in the drawing in which the head H _B serves the tape 1, the frequency f _S + f _B Is taken out and supplied to the frequency converter 16. Accordingly, in from the frequency converter 16, the head H _A is P FR to treat the tape (1), the frequency of the subcarriers carrying the color signal CA to f _A is obtained and treated in the head H _B tape (1) in the blood the yield, is the frequency of the sub-carriers carrying the color signal CA to _a f is obtained, and the head H _B blood Ile to treat the tape (1), the frequency of the sub-carriers carrying the color signal in f _B can be obtained. The carrier color signals CA and CB are supplied to the synthesizer 14, synthesized with the modulated luminance signal, and supplied to the heads H _A and H _B through the _amp 18.

In this way, carrier color signals CA and CB of the relationship interleaved with each other are recorded in the adjacent tracks T _A and T _B as shown in FIGS. 6A and 6B.

In the regeneration, as shown in FIG. 5, the regeneration output from the heads H _A and H _B is supplied to the high pass filter 21 through the regeneration amplifier 29 to take out the modulated luminance signal, and the limiter ( The demodulator 23 supplies the demodulator 23 through the signal 22 and supplies the demodulated luminance signal to the synthesizer 24. In the above-described recording, as shown in FIG. 3, even when a so-called guard band is not provided between adjacent tracks T _A and T _B , the modulated luminance signal is a high frequency signal, so that the head H _A is a track. when scanning the T _a this and scanning a portion of the track T _B, also the head when the H _B scans the track T _B this is also to scan a portion of the track T _a, cross-torque does not occur, the synthesizer 24 is provided A luminance signal without crosstalk is supplied.

The regeneration output from the heads H _A and H _B is further supplied to the low pass filter 25 to take out the reproducing transfer color signal. When recording, as described above, when no head guard is provided between adjacent tracks T _A and T _B , when head H _A scans track T _A , this scans part of track T _B , the output of the filter 25 at the time is, as first shown in Fig. 6c also, with respect to the signal C _a signal C _B in which the frequency interleaver eve relationship is to be mixed as the cross-torque component, again head H _B When scanning the track T _B , if it scans a part of the track T _A , the output of the filter 25 at this time has a relationship of frequency interleaving with the signal C _B as shown in FIG. 6D. The signal C _A is mixed as a crosstalk component. The output of this filter 25 is supplied to the frequency converter 26, and as in the case of recording, in the feed where the head H _A reproduces the track T _A by the switching signal SC, as shown in the drawing. The signal of the frequency f _S + f _A is taken out from this state, and in the case where the head H _B reproduces the track T _B , the state is reversed from the state shown in the drawing, where f _S + A signal of frequency f _B is taken out and supplied to the frequency converter 26. Therefore, from the frequency converter 26, in the feed head H _A reproduces the track T _B , as shown in FIG. 6E, the signal CSA in which the frequency of the subcarrier becomes the original frequency f _S is different from that of the frequency H 26. It is obtained that a crosstalk component having a frequency interleaved relationship is mixed, and in the feed where the head H _B reproduces the track T _B , as shown in FIG. 6F, the frequency of the subcarrier is similar to the original frequency f _S. For the signal CS _B which is obtained, a mixture of crosstalk components having a frequency interleaving relationship with this is obtained. Therefore, when the output of this frequency converter 26 is supplied to the C-shaped hair comb-type filter 28, as shown in FIG. 6G, the crosstalk component is removed and the original carrier color signal CS is obtained. The carrier color signal CS is supplied to the combiner 24 and synthesized with the luminance signal.

Thus, at the output terminal 29, a reproduction color video signal without crosstalk is obtained.

In this case, however, as described above, a signal having a frequency of f _S + f _A and a signal having a frequency of f _S + f _B are obtained from another oscillation circuit, and the switch circuits 17 and 27 are used. In order to switch out and to take out, the frequency conversion signal supplied from the switch circuits 17 and 27 to the frequency converters 16 and 28 is converted at the time of inversion of the switching signal SC shown in FIG. As shown in the diagram (b), it becomes discontinuous. For this reason, the carrier color signals obtained by the frequency changers 16 and 26 are also discontinuous at the seam of the shield. In addition, even if an automatic phase adjustment circuit for controlling the frequency of the frequency conversion signal supplied to the frequency converter 26 at the time of reproduction based on the burst signal in the reproduction carrier color signal, a so-called APC circuit, the followability of the APC operation is maintained. Since there is a limit, the carrier color signal cannot be taken out continuously, and color becomes largely distorted at the beginning of the feed.

The present invention is intended to eliminate such drawbacks. Next, an example of the present invention circuit will be described based on FIG.

8 shows a case where the present invention is applied to a recording / playback combiner, where 30 is a recording / playback switching switch, which is switched to the contact point R side at the time of recording and to the contact point P side at the time of reproduction.

In the present invention, a variable frequency oscillator 31 is provided. The free oscillation frequency of this oscillator 31 selects the intermediate degree between 2f _A and 2f _B , for example. The oscillation output of the variable frequency oscillator 31 is supplied to the frequency divider circuit 32. The frequency division ratio of the frequency division circuit 32 is switched for every one day by the above-described switching signal SC. For example, n is an integer,

과

로 절환한다. 그리고 이 분주회로(32)의 출력을 위상검파회로(33)에 공급하여 수평동기신호 pH와 위상비교하여, 그 검파출력을 저역통과 필터(34)를 통해서 가변주파수 발진기(31)에 공급하여 그 발진주파수를 제어한다.When I choose it, the division ratio is

and

Switch to. The output of the frequency dividing circuit 32 is supplied to the phase detection circuit 33 to compare the phase with the horizontal synchronization signal pH, and the detection output is supplied to the variable frequency oscillator 31 through the low pass filter 34. Control the oscillation frequency.

로 분주하여, 그 출력을, 발진회로(36)로 부터의 f_S라는 주파수의 신호와 함께 주파수 변환기(37)에 공급하여, 이것에서 양자의 합의 주파수의 주파수변환용 신호를 얻어, 이것을 기록계의 주파수변환기(16) 및 재생계의 주파수변환기(26)에 공급한다.Then, the oscillation output of the frequency controlled variable frequency oscillator 31 is supplied to the divider 35 by

And the output is supplied to the frequency converter 37 together with the signal of frequency f _S from the oscillator circuit 36 to obtain a signal for frequency conversion of the sum of the frequencies of the two. The frequency converter 16 and the frequency converter 26 of the reproduction system are supplied.

로 절환됨으로써, 가변주파수 발진기(31)의 발진주파수는 2f_A=2nf_H로 되며, 따라서 분주기(35)에서는 f_A라는 주파수의 신호가 얻어지고, 따라서 주파수 변환기(37)에서는 f_S+f_A라는 주파수의 주파수변환용 신호가 얻어진다. 한편, 예컨대 헤드 H_B가 트랙 T_B를 형성 내지 주사하는 피일드에 있어서는, 분주회로(32)의 분주비가

로 절환됨으로써, 가변주파수 발진기(31)의 발진주파수는 2f_B=(2n+1)f_H로 되며, 따라서 분주기(35)에서는 f_B라는 주파수의 신호가 얻어지며, 따라서, 주파수 변환기(37)에서는 f_S+f_B라는 주파수의 주파수 변환용 신호가 얻어진다. 따라서, 상술한 바와 같은 기록, 재생이 되어진다.In this way, for example, in the feed head H _A forms or scans the track T _A , the division ratio of the frequency dividing circuit 32 is

By switching to, the oscillation frequency of the variable frequency oscillator 31 becomes 2f _A = 2nf _H , so that the frequency divider 35 obtains a signal of frequency f _A , and therefore the frequency converter 37 provides f _S + f. _A frequency conversion signal of frequency _A is obtained. On the other hand, in the feed where the head H _B forms or scans the track T _B , the division ratio of the frequency dividing circuit 32 is

By switching to, the oscillation frequency of the variable frequency oscillator 31 becomes 2f _B = (2n + 1) f _H , so that the frequency divider 35 obtains a signal of frequency f _B , and thus the frequency converter 37. ), A signal for frequency conversion of a frequency f _S + f _B is obtained. Therefore, recording and reproduction as described above are performed.

에서

로, 또는 그 반대로 절환되며, 따라서 가변주파수 발진기(31)의 발진주파수가 2f_A에서 2f_B로, 또는 그 반대로 변할 때, 발진기의 성질상 그 발진파형(發振波形)이 불연속적으로 되는 일은 없으며, 연속파형으로서 주파수가 변하도록 된다. 따라서 주파수 변환기(37)에서 얻어지는 주파수 변환용 신호도, 제7c도에 나타낸 바와 같이, 파형이 연속된 것으로 되며, 따라서 주파수 변환기(16) 및 (26)에서 얻어지는 반송색신호도, 그 파형이 연속된 것으로 된다. 그리고, 재생시, 이와 같이 연속된 파형의 재생반송색호가 얻어지므로, APC회로에 의하여 발진회로(36)에서 얻어지는 신호의 주파수를 제어했을 때, APC가 확실히 추종하며, 피일드의 처음에서 색상이 흐터지는 일은 없다.In this case, the dividing ratio of the dividing circuit 32

in

When the oscillation frequency of the variable frequency oscillator 31 changes from 2f _A to 2f _B or vice versa, the oscillation waveform is discontinuous due to the nature of the oscillator. No frequency changes as a continuous waveform. Therefore, the frequency conversion signal obtained by the frequency converter 37 also has a continuous waveform as shown in FIG. 7C. Therefore, the carrier color signal obtained by the frequency converters 16 and 26 also has a continuous waveform. It becomes. When the reproduction is performed, the reproduction carrier color arc of such a continuous waveform is obtained. Therefore, when the frequency of the signal obtained by the oscillation circuit 36 is controlled by the APC circuit, the APC reliably follows the color. There is no distraction.

로 분주한 신호를 공급하여 가변주파수 발진기(31)에서 f_A또는 f_B라는 주파수의 발진출력을 직접 얻어, 이것을 분주기(35)를 통함이 없이 직접 주파수 변환기(37)에 공급하도록 하여도 된다.In addition, the phase detection circuit 33 replaces the horizontal synchronization signal pH.

The oscillation output of the frequency f _A or f _B may be directly obtained from the variable frequency oscillator 31 by supplying the divided signal to the frequency converter 37, and may be supplied directly to the frequency converter 37 without passing through the divider 35. .

fd로 선정하고, 재생계의 머리빗형필터(28)는, 그 때의 반송색 신호와 2수평주기전의 반송색신호를 합성하는 구성으로 한다.The present invention can also be applied to recording and reproducing color video signals of a PAL system. In this case, the difference between f _A and f _{B is} , for example,

Selected by fd, the hair comb filter 28 of the reproduction system is configured to synthesize the carrier color signal at that time and the carrier color signal before two horizontal periods.

Therefore, in this case, for example, n is an integer

과

로 절환하도록 하여 가변주파수 발진기(31)에서 4f_A=4nf_H또는 4f_B=(4n+1)f_H라는 주파수의 발진출력을 얻어, 이것을 발진기(35)로서

로 분주하여 주파수 변환기(37)에 공급하면 된다.When selecting to set the ratio to the frequency division circuit 32,

and

The oscillation output of the frequency 4f _A = 4nf _H or 4f _B = (4n + 1) f _H is obtained from the variable frequency oscillator 31, which is converted into the oscillator 35.

The frequency converter 37 may be dispensed with and supplied to the frequency converter 37.

Claims (1)

A single variable frequency oscillator is provided as shown in the figure and described above in the main text, and a frequency conversion signal for a carrier color signal is formed based on the signal from the oscillator, and the carrier color signal is converted by the frequency conversion signal. And a frequency conversion circuit of the carrier color signal such that the oscillation frequency of the oscillator is varied at each track switching so that the frequency-converted carrier color signal is interleaved with each other in adjacent tracks.

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