JPS62278883A - Carrier chrominance signal frequency convertion circuit - Google Patents

Abstract

PURPOSE:To reduce a time base variation to be produced in a low frequency carrier chrominance signal by applying a phase control in using the burst signal in the carrier chrominance signal as a reference signal, and executing a frequency control, and using the frequency-divided output out of the stabilized oscillating output resulting from the above phase control as a reference signal. CONSTITUTION:The phase of a crystal voltage controlled oscillator 14 is made synchronous with that of the burst signal St in the carrier chrominance signal Cc supplied to a frequency convertion part 12, and is supplied to the part 12 and to a frequency divider 25. Accordingly, a voltage controlled oscillator 15 is frequency-controlled by using a signal Se from the frequency divider 25 as a reference signal. As a result, the oscillating output signal Sa of the crystal voltage controlled oscillator 14 and that Sb of the voltage controlled oscillator 15 are both made at all time stable in their frequencies.

Description

[Detailed description of the invention] 3. Detailed description of the invention The present invention will be explained in the following order.

A. Field of industrial application B. Overview of the invention - C. Prior art D. Problems to be solved by the invention E. Means for solving the problems. Operation (Fig. 1) H Effects of the Invention A Industrial Application Field The present invention provides a carrier color signal that performs a process of converting the frequency of the carrier color signal of a luminance signal and a carrier color signal that form a color video signal. Related to frequency conversion circuits.

B. Summary of the Invention The present invention provides a carrier color signal frequency conversion circuit that converts the frequency of a carrier color signal that forms a color video signal together with a luminance signal to a lower frequency band. The conversion signal is the oscillation output of the first voltage controlled oscillator which should generate a signal with a frequency equal to the carrier wave frequency of the carrier color signal, and the second voltage controlled oscillator which should generate a signal with a frequency proportional to the line frequency. The first voltage controlled oscillator is controlled based on the comparison output obtained by comparing the phases of the oscillation output and the burst signal in the carrier color signal, and the second voltage A divided output obtained by frequency-dividing the oscillation output of the controlled oscillator to obtain a signal with a frequency equal to the line frequency, and a first
By frequency-comparing the oscillation output of the voltage-controlled oscillator with the frequency-divided output obtained by dividing the oscillation output of the voltage-controlled oscillator to obtain a signal with a frequency equal to the line frequency, the frequency is controlled based on the comparison output obtained by comparing the frequency. The frequency stability of the conversion signal can be improved, and the time axis fluctuation that occurs in the frequency-converted carrier color signal due to the frequency instability of the frequency conversion signal can be reduced. .

C. Conventional technology When a color video signal is recorded on a magnetic tape,
The luminance signal and the carrier chrominance signal that form the color video signal are separated from each other, the separated luminance signal is frequency-modulated on the high frequency side, and is converted into a frequency modulated luminance signal, and the carrier chrominance signal is frequency-converted on the low frequency side. A recording method is widely used in which the low-frequency color signals are mixed and supplied to a rotating magnetic head, and then recorded on a magnetic tape by the rotating magnetic head.

When such a recording method is adopted, a frequency conversion circuit is used that converts the frequency of the carrier color signal to a lower frequency band. A color signal frequency conversion circuit is shown.

In the circuit shown in FIG. 2, the frequency f, which is separated from the color video signal, is approximately 3.58M, for example.
A carrier color signal C6 having a carrier wave component of Hz is supplied through an input terminal 11 to a frequency converter 12 for carrier color signals. The frequency conversion signal Sx is also supplied to the frequency conversion section 12 from the conversion signal formation section 13 . The conversion signal forming unit 13 also includes a crystal voltage controlled oscillator (VXO) 1 that should generate a signal having a frequency Esc.
4 oscillation output signal Sa and a frequency proportional to the line frequency fH (approximately 15°75kHz), for example, 378·fH.
a voltage controlled oscillator (VCO) 1 to generate a signal having
A signal Sc having a frequency fL=378·rH/8, which is obtained by dividing the frequency of the oscillation output signal sb of No. 5 by 1/8 in the frequency divider 16, is supplied.

The crystal voltage controlled oscillator 14 is configured to perform phase control by forming a phase-locked loop (PLL), and is supplied to the frequency conversion unit 12 extracted through the burst gate unit 17. The phase of the burst signal St in the carrier color signal Cc and the phase of the oscillation output signal Sa of the crystal voltage controlled oscillator 14 are compared in the phase comparator 1, and the comparison output obtained from the phase comparator 18 is passed through the low-pass filter. The oscillation phase of the crystal voltage controlled oscillator 14 is controlled based on the control signal Spc obtained at the output side of the low-pass filter 19 by being supplied to the (LPF) 19 .

As a result of such control, the oscillation output signal Sa of the crystal voltage controlled oscillator 14 has a frequency fie, and its phase is synchronized with the phase of the burst signal St in the carrier color signal Cc supplied to the frequency converter 12. be taken as a thing.

On the other hand, the voltage controlled oscillator 15 is frequency controlled, and the oscillation output signal s of the voltage controlled oscillator 15 is
b is frequency-divided by 1/378 in the frequency divider 20 and the horizontal synchronizing signal S in the luminance signal that forms the color video signal together with the carrier color signal C0, which is supplied through the terminal 21. are compared in the frequency comparator 22, and the comparison output obtained from the frequency comparator 22 is supplied to the low-pass filter 23. Based on the control signal Sfc obtained at the output side of the low-pass filter 23, the voltage controlled oscillator 15 oscillation frequencies are controlled. As a result of such control, the oscillation output signal S of the voltage controlled oscillator 15
The signal S from the frequency divider 16 obtained by dividing b by 178
It is assumed that c has a frequency fL that is set based on the frequency of the horizontal synchronization signal S8.

Then, in the conversion signal forming section 13, from the oscillation output signal Sa of the frequency fsc from the crystal voltage controlled oscillator 14 and the signal Sc of the frequency fL from the frequency dividing section 16,
The frequency conversion signal Sx supplied to the frequency conversion section 12 described above is formed as a signal having a frequency fe=rsc+fL. As a result, in the frequency converter 12,
The carrier color signal Cc supplied through the input terminal 11 is frequency-converted based on the frequency conversion signal Sx so that the carrier wave component of the frequency f5c is set to the frequency fX-f, c=fL, and is output from the frequency conversion section 12. , a low-band carrier color signal CL having a carrier component of frequency r is obtained.

In this way, the output terminal 24 connected to the output end of the frequency converter 12 receives the low frequency carrier color signal CL obtained by frequency converting the carrier color signal C6 to the low frequency band side.

D Problems to be Solved by the Invention In the conventionally proposed carrier color signal frequency conversion circuit as described above, an oscillation output signal sb with a frequency of 378·fH proportional to the line frequencies f and l is generated. For frequency control of the voltage controlled oscillator 15, a horizontal synchronizing signal Sol in a luminance signal forming a color video signal together with a carrier color signal C9 is used.
is used, so the horizontal synchronization signal SN in the luminance signal
For example, the luminance signal and carrier color signal are required to have a regular line frequency f, but for example, if the luminance signal and the carrier color signal are reproduced from the playback output of a color video signal recorded on a magnetic tape after multiple dubbing, In the case where the horizontal synchronizing signal SH in the luminance signal is separated, the horizontal synchronizing signal SH in the luminance signal contains an error with respect to the normal line frequency "A" that occurs each time dubbing, and therefore is used for frequency control of the voltage controlled oscillator 15. The horizontal synchronization signal SH is the normal line frequency f
N, the voltage controlled oscillator 1
There is a possibility that proper frequency control of No. 5 may not be performed.

Then, the horizontal synchronizing signal SH has the normal line frequencies f, l.
If proper frequency control of the voltage controlled oscillator 15 is not performed due to the fact that the voltage controlled oscillator 15 does not have a The low frequency carrier color signal obtained by the frequency conversion performed by the frequency conversion unit 12 based on Sx includes a considerable amount of time axis fluctuation caused by frequency instability of the frequency conversion signal Sx. turn into.

In view of this, the present invention provides a method in which, when frequency converting a carrier color signal to the lower frequency band side to obtain a low-band carrier color signal, a frequency conversion signal for the carrier color signal is equal to the carrier frequency of the carrier color signal. an oscillation output of a first voltage-controlled oscillator whose phase is controlled to generate a signal having a frequency whose phase is synchronized with the phase of a burst signal in the carrier color signal; and a signal whose frequency is proportional to the line frequency. It is formed based on the oscillation output of the second voltage controlled oscillator whose frequency is controlled to be generated, and not only the phase control of the first voltage controlled oscillator but also the frequency control of the second voltage controlled oscillator. If the frequency conversion is carried out properly at all times, the frequency conversion signal will have excellent frequency stability. Even when separated, the carrier color signal frequency is such that the time axis fluctuations that occur in the low frequency carrier color signal due to frequency instability of the frequency conversion signal are reduced. The purpose is to provide a conversion circuit.

E. Means for Solving the Problems In order to achieve the above-mentioned object, the carrier color signal frequency conversion circuit according to the present invention should generate a signal with a frequency equal to the carrier frequency of the carrier color signal supplied as an input signal. a first voltage-controlled oscillator, a second voltage-controlled oscillator that generates a signal with a frequency proportional to the line frequency, an oscillation output of the first voltage-controlled oscillator, and an oscillation of the second voltage-controlled oscillator. a conversion signal forming unit that obtains a frequency conversion signal from the output;
and a frequency conversion unit that converts the frequency of the carrier color signal to a lower frequency band based on the frequency conversion signal,
First oscillation control for controlling the first voltage controlled oscillator based on a comparison output obtained by comparing the phases of the oscillation output and the burst signal in the carrier color signal for the first voltage controlled oscillator. a first voltage-controlled oscillator for dividing the oscillation output of the first voltage-controlled oscillator to obtain a signal having a frequency equal to a line frequency associated with the carrier color signal; a second frequency dividing section that divides the oscillation output of the second voltage controlled oscillation section to obtain a signal with a frequency equal to the above-mentioned line frequency, and a frequency dividing section obtained from the first frequency dividing section. and a second oscillation control section that controls the second voltage controlled oscillation section based on a comparison output obtained by frequency comparing the frequency output and the frequency division output obtained from the second frequency division section. be done.

F effect In the carrier color signal frequency conversion circuit according to the present invention configured as described above, the first voltage controlled oscillation section is phase-controlled by the first oscillation control section, and the carrier color signal is supplied to the frequency conversion section. has a frequency equal to the carrier frequency of the color signal,
The second voltage-controlled oscillation section sends out an oscillation output whose phase is synchronized with the phase of the burst signal in the carrier color signal, and the second voltage-controlled oscillation section is frequency-controlled by the second oscillation control section, and the first The frequency dividing section divides the oscillation output of the first voltage controlled oscillation section to obtain a signal with a frequency equal to the line frequency, and sends out an oscillation output whose frequency matches the frequency of the frequency-divided output. Then, in the conversion signal forming section, a frequency conversion signal is formed based on the respective oscillation outputs of the first and second voltage controlled oscillation sections obtained as described above, and the signal is supplied to the frequency conversion section. Ru. In the frequency converter, the carrier color signal supplied there as an input signal is frequency-converted based on the frequency conversion signal, and from the frequency converter, the carrier color signal is converted into a low-band carrier whose frequency has been converted to the lower frequency band side. Color signals can be obtained.

In this way, the first voltage-controlled oscillator is configured to perform phase control using the burst signal in the carrier color signal as a reference signal, and the second voltage-controlled oscillator is configured to perform phase control using the burst signal in the carrier color signal as a reference signal. The divided output of the stabilized oscillation output obtained from the first voltage controlled oscillator is used as a reference signal to perform frequency control.
and the phase control and frequency control for the second voltage controlled oscillator are always properly performed, and the frequency conversion signal formed based on the respective oscillation outputs of the first and second voltage controlled oscillators is It has excellent frequency stability, and as a result, time axis fluctuations occurring in the low frequency carrier color signal due to frequency instability of the frequency conversion signal are reduced.

G Example G-1 Configuration (FIG. 1) FIG. 1 shows an example of a carrier color signal frequency conversion circuit according to the present invention. In FIG. 1, parts corresponding to the respective parts in the above-mentioned FIG.
Signals corresponding to the signals obtained in the figure are given the same reference numerals as in FIG. 2, and repeated explanation of each of them will be omitted.

In this example, in addition to the configuration similar to the configuration shown in FIG. Frequency dividing unit 25 that divides the frequency as much as possible
Further, a switch 26 is provided which selectively takes out the signal Se from the frequency dividing section 25 and the horizontal synchronizing signal S supplied through the terminal 21 and supplies it to the frequency comparing section 22 . The switch 26 is controlled by a switch control signal SS supplied from a control signal terminal 27, and normally, its movable contact 26c is connected to the selection contact 26a, and the frequency division signal supplied to the selection contact 26a is The signal Se from the section 25 is taken out through the movable contact 26c.

G-2 operation (Fig. 1) Based on this configuration, the crystal voltage controlled oscillator 14 forms a phase locked loop (PLL) in the same way as in the case of Fig. 2. The oscillation output signal Sa has a frequency f8c, and its phase is synchronized with the phase of the burst signal St in the carrier color signal C6 supplied to the frequency converter 12, It is supplied to the frequency converter 12 and also to the frequency divider 2.
5 is also supplied. The frequency divider 25 divides the frequency of the oscillation output signal Sa by 1/227, for example, to generate a signal Se having a line frequency f. The signal Se from the frequency divider 25 is obtained by dividing the oscillation output Sa of the crystal voltage controlled oscillator 14, which operates under phase control by a phase-locked loop. The signal becomes stable at all times, and switch 2
6 to the frequency comparator 22.

As a result, the frequency of the voltage controlled oscillator 15 is controlled using the signal Se from the frequency dividing section 25 as a reference signal, and the oscillation output signal sb of the voltage controlled oscillator 15 is changed to 1 by the frequency dividing section 20. The frequency of the signal Sd obtained by dividing the frequency by /378 and the frequency dividing unit 25 supplied via the switch 26
is compared with the signal Se from the frequency comparator 22, and the comparison output obtained from the frequency comparator 22 is supplied to the low-pass filter 23. Based on the control signal Src obtained at the output side of the low-pass filter 23, ,
The oscillation frequency of voltage controlled oscillator 15 is controlled. As a result of such control, the signal SC from the frequency divider 16 obtained by dividing the oscillation output signal sb of the voltage controlled oscillator 15 by 1/8 is equal to the frequency of the signal Se from the frequency divider 25, that is, the line frequency. It is assumed that the frequency fL is set based on fl().

At this time, since the signal Se from the frequency divider 25 is always a stable signal having line frequencies f and l, frequency control is performed using the stable signal Se as a reference signal for the voltage controlled oscillator 15. Therefore, the voltage controlled oscillator 15 is always properly controlled in frequency, and its oscillation output signal sb is made stable in terms of frequency.

Then, in the conversion signal forming section 13, from the oscillation output signal Sa of the frequency fie from the crystal voltage controlled oscillator 14 and the signal Sc of the frequency fL from the frequency dividing section 16,
Frequency conversion signal S having frequency fx=fsc”fL
x is formed and supplied to the frequency converter 12.

As a result, in the frequency converter 12, the input terminal 11
The carrier color signal CC supplied through is frequency-converted based on the frequency conversion signal Sx so that the carrier wave component of the frequency fsc is set to the frequency fXrsc=fL,
A low frequency carrier color signal CL having a carrier wave component of frequency fL is obtained from the frequency converter 12, and is sent to the output terminal 24.
is derived. In this case, the oscillation output signal Sa of the crystal voltage controlled oscillator 14 and the oscillation output signal sb of the voltage controlled oscillator 15 used to form the frequency conversion signal Sx
Since both are always stable in terms of frequency, the frequency conversion signal Sx has excellent frequency stability.

Note that when the switch 26 is controlled by the switch control signal Ss and its movable contact 26c is connected to the selection contact 26b, the horizontal synchronization signal from the terminal 21 supplied to the selection contact 26a is Signal S is at movable contact 2
6c and supplied to the frequency comparator 22. Accordingly, the frequency of the voltage controlled oscillator 15 is controlled using the horizontal synchronizing signal S as a reference signal, and the oscillation output signal sb of the voltage controlled oscillator 15 is 178
The signal SC from the frequency dividing unit 16 obtained by frequency division has a frequency fL set based on the frequency of the horizontal synchronization signal SN.
It is assumed that the

Effects of the Invention H As is clear from the above explanation, the carrier color signal frequency conversion circuit according to the present invention converts the carrier color signal, which forms the color video signal together with the luminance signal, to the low frequency band side. In order to obtain the carrier color signal, a frequency conversion signal for the carrier color signal is generated in order to generate a signal having a frequency equal to the carrier wave frequency of the carrier color signal and whose phase is synchronized with the phase of the burst signal in the carrier color signal. The oscillation output of the first voltage controlled oscillator is phase controlled and the second voltage controlled oscillator is frequency controlled to generate a signal with a frequency proportional to the line frequency.
oscillation output of the voltage controlled oscillator, the phase control of the first voltage controlled oscillator is properly performed using the burst signal as a reference signal, and the frequency of the second voltage controlled oscillator is Since the control is always properly performed using the signal obtained by frequency-dividing the oscillation output of the first voltage-controlled oscillator as the reference signal, the frequency stability of the frequency conversion signal can be improved. Therefore, even if the carrier color signal is separated from the reproduced output of a color video signal recorded on a magnetic tape after dubbing multiple times, the color video signal will be transferred together with the carrier color signal. This is due to frequency instability of the frequency conversion signal, which may occur significantly when the horizontal synchronization signal in the luminance signal forming the signal is used as a reference signal in frequency control of the second voltage controlled oscillator. As a result, it is possible to significantly reduce the time axis fluctuations occurring in the low frequency carrier color signal.

[Brief explanation of drawings]

FIG. 1 is a block connection diagram showing an example of a carrier color signal frequency conversion circuit according to the present invention, and FIG. 2 is a block connection diagram showing an example of a carrier color signal frequency conversion circuit according to the present invention.
FIG. 2 is a block connection diagram showing a wave number conversion circuit. In the figure, 12 is a frequency conversion section, 13 is a conversion signal formation section,
14 is a crystal voltage controlled oscillator, 15 is a voltage controlled oscillator, 16, 20 and 25 are frequency dividing sections, 18 is a phase comparison section, and 22 is a frequency comparison section. Figure 1

Claims (1)

[Scope of Claims] A first voltage-controlled oscillator that generates a signal with a frequency equal to the carrier frequency of a carrier color signal supplied as an input signal; an oscillation output of the first voltage-controlled oscillator and the carrier a first oscillation control section that compares the phase of the burst signal in the color signal and controls the first voltage controlled oscillation section based on the comparison output; a first frequency divider that divides the frequency to obtain a signal with a frequency equal to the line frequency associated with the carrier color signal; a second voltage controlled oscillator that generates a signal with a frequency proportional to the line frequency; a second frequency dividing section that divides the oscillation output of the second voltage controlled oscillation section to obtain a signal having a frequency equal to the line frequency; and a divided output obtained from the first frequency dividing section and the second a second oscillation control section that compares the frequencies of the frequency-divided output obtained from the frequency division section and controls a second voltage-controlled oscillation section based on the comparison output; and oscillation of the first voltage-controlled oscillation section. a conversion signal forming unit that obtains a frequency conversion signal from the output and the oscillation output of the second voltage controlled oscillation unit; and a conversion signal forming unit that converts the frequency of the carrier color signal to a lower frequency band based on the frequency conversion signal. A carrier color signal frequency conversion circuit comprising: a conversion section;