JPH0691666B2 - Video signal recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in the following order.

A Industrial field of use B Outline of the invention C Conventional technology D Problems to be solved by the invention E Means for solving the problem F Working G Example H Effect of the invention A Industrial field of use The present invention The present invention relates to a video signal recording / reproducing apparatus which adopts a method of converting a carrier color signal into a low frequency band when recording a video signal, and particularly to a circuit device for frequency conversion of the carrier color signal.

B. Summary of the Invention The present invention is directed to a recording system in which a first voltage-controlled oscillation circuit for generating a carrier having an original sub-carrier frequency before low frequency conversion, an oscillation output of the first voltage-controlled oscillation circuit, and a low-voltage oscillation circuit are provided. A phase comparison circuit that compares the phase of a burst signal in the carrier color signal before domain conversion, a first loop filter that is interposed between the phase comparison circuit and the first voltage controlled oscillation circuit, and a horizontal frequency A second voltage controlled oscillation circuit for generating a carrier wave of a predetermined frequency proportional to the frequency, a frequency detection circuit for detecting the frequency of the oscillation output of the second voltage controlled oscillation circuit, the frequency detection circuit and the first voltage A carrier color from a second loop filter inserted or inserted between the control oscillation circuit and the oscillation output of the first voltage control oscillation circuit and the oscillation output of the second voltage control oscillation circuit. To low-pass the signal A reproduction system having a conversion carrier wave generation frequency conversion circuit for obtaining a carrier wave and a carrier color signal frequency conversion circuit for low-frequency converting the carrier color signal by the conversion carrier wave obtained from the conversion carrier wave generation frequency conversion circuit. In addition, a reference oscillation circuit that generates a carrier wave of the original subcarrier frequency before low frequency conversion, a voltage control oscillation circuit that should generate a carrier wave of a predetermined frequency proportional to the horizontal frequency, an oscillation output of the reference oscillation circuit and the original Phase comparison circuit for phase comparison with the burst signal in the carrier color signal after being converted to the frequency, the first loop filter interposed between the phase comparison circuit and the voltage controlled oscillation circuit, and the voltage control A frequency detection circuit for detecting the frequency of the oscillation output of the oscillation circuit, and a second loop filter interposed between the frequency detection circuit and the voltage controlled oscillation circuit. A frequency conversion circuit for generating a carrier wave for conversion, which obtains a carrier wave for converting the carrier color signal that has been low-frequency converted to the original frequency from the oscillation output of the reference oscillation circuit and the oscillation output of the voltage control oscillation circuit, A video signal recording / reproducing apparatus having a carrier color signal frequency conversion circuit for converting a carrier color signal, which has been low-frequency converted by the conversion carrier obtained from the conversion carrier generation frequency conversion circuit, into an original frequency, in the recording system. , And the phase comparison circuit of the reproduction system is also used as a single phase comparison circuit, and the first loop filter of the recording system and the first loop filter of the reproduction system are used.
Is used as a single loop filter, and the DC gain of the first loop filter, which is also used, is switched between recording and reproduction so as to be smaller than that during reproduction. The circuit configuration for frequency conversion is simplified, and at the time of recording, the phase-locked loop including the first voltage-controlled oscillation circuit, the phase comparison circuit, and the first loop filter of the recording system is surely locked so that the first A carrier wave synchronized with the burst signal in the carrier color signal to be recorded is surely obtained from the voltage control oscillation circuit, and includes a reference oscillation circuit of the reproduction system, a phase comparison circuit, a first loop filter and a voltage control oscillation circuit. The automatic phase control loop ensures the correct phase of the reproduced carrier color signal so that the steady phase error of the reproduced carrier color signal is sufficiently small. It is intended.

C Conventional Technology In a video tape recorder for recording a video signal on a magnetic tape by a rotary magnetic head, a method of frequency-modulating a luminance signal and low-frequency converting a carrier color signal is used for recording.

FIG. 5 and FIG. 6 show a circuit device for frequency conversion of carrier color signals in a recording system and a reproducing system of an example of a conventional video tape recorder adopting such a system. The subcarrier frequency of the horizontal frequency f _H is 37
This is the case when it is set to 743kHz, which is 8/8 times.

In the recording system, the carrier color signal Cs with a subcarrier frequency of 3.58MHz is input from the input terminal 36R to the carrier color signal frequency conversion circuit 37R.
Is converted into a low frequency band by the conversion carrier generation frequency conversion circuit 38R as described later, and the sub carrier frequency is changed to 743 kHz at the output terminal 39R. The carrier color signal C _L is obtained.

To obtain the above-mentioned carrier wave for conversion, a voltage controlled crystal oscillator circuit 41R that should generate a carrier wave of 3.58MHz, and 378f _H = 5.95MH
A voltage controlled oscillator circuit 51R for generating a carrier wave of z is provided, the carrier color signal Cs supplied to the input terminal 36R is supplied to the burst gate circuit 61, and the burst signal in the carrier color signal Cs is extracted, and the burst Signal is phase comparator 64R
And the carrier wave obtained from the voltage controlled crystal oscillation circuit 41R is supplied to the phase comparison circuit 64R, the output voltage of the phase comparison circuit 64R is supplied to the loop filter 70R,
Output voltage of loop filter 70R is voltage controlled crystal oscillator circuit 4
Phase locked loop (PLL) 6 by being supplied to 1R
5, the carrier wave obtained from the voltage controlled crystal oscillation circuit 41R is synchronized with the burst signal in the carrier color signal Cs.

Further, the carrier wave obtained from the voltage controlled oscillator circuit 51R is supplied to the frequency divider circuit 53R and divided into 1/378, and the frequency-divided carrier wave is supplied to the frequency detection circuit 81 and the frequency from the input terminal 82R. horizontal sync signal S _H in the video signal to be recorded is supplied to a detection circuit 81, the output voltage of the frequency detection circuit 81 is supplied to a loop filter 83, the supply output voltage of the loop filter 83 to the voltage controlled oscillation circuit 51R As a result, the automatic frequency control loop (AFC loop) 85 is configured, and the frequency of the carrier wave obtained from the voltage controlled oscillator circuit 51R is 378 of the horizontal frequency f _H of the video signal to be recorded.
Therefore, the frequency of the carrier wave obtained from the frequency dividing circuit 53R is made equal to the horizontal frequency f _H of the video signal to be recorded.

And 378f _H = 5.95 obtained from the voltage controlled oscillator circuit 51R
The MHz carrier is supplied to the divider 52R and divided into 1/8, and the divided 743kHz carrier and the 3.58MHz carrier obtained from the voltage controlled crystal oscillator 41R are used for conversion carrier generation frequency conversion. It is supplied to the number circuit 38R, and the carrier color signal Cs is supplied from the conversion carrier generation frequency conversion circuit 38R as described above.
It is possible to obtain a carrier wave for conversion having a frequency of 3.58MHz + 743kHz which should be converted to the low frequency range.

In the reproduction system, the low-frequency conversion carrier color signal C _L whose subcarrier frequency is set to 743 kHz is supplied from the input terminal 36P to the carrier color signal frequency conversion circuit 37P, and the conversion carrier generation frequency conversion circuit as described later. 3.58MHz + 743k obtained from 38P
A carrier color signal Cs having a subcarrier frequency of 3.58 MHz is obtained at the output terminal 39P by being converted to the original frequency by the carrier wave for conversion having a frequency of Hz.

To obtain a conversion carrier described above, a crystal oscillator circuit 41P for generating a stable carrier of 3.58 MHz, the voltage controlled oscillator circuit 51P provided to be generated carrier waves of 378f _H = 5.95MHz,
The carrier wave obtained from the voltage controlled oscillator circuit 51P is the frequency divider circuit 53P.
Is supplied to the frequency detecting circuit 91, and the divided carrier is supplied to the input terminal 92.
The horizontal synchronizing signal S _H in the reproduced video signal is supplied from P to the frequency detection circuit 91, the output voltage of the frequency detection circuit 91 is supplied to the loop filter 93, and the output voltage of the loop filter 93 is supplied to the voltage controlled oscillator circuit 51P. As a result, the frequency pull-in loop 96 for the voltage controlled oscillator circuit 51P is configured, and the frequency of the carrier wave obtained from the voltage controlled oscillator circuit 51P becomes 378 times the horizontal frequency f _H of the reproduced video signal, and therefore the frequency divider circuit 53P. The frequency of the carrier wave obtained from is equal to the horizontal frequency f _H of the reproduced video signal.

378f _H = 5.95MHz obtained from this voltage controlled oscillator circuit 51P
The carrier wave of is supplied to the frequency divider circuit 52P and is frequency-divided to 1/8. The frequency-divided 743 kHz carrier wave and the 3.58 MHz carrier wave obtained from the crystal oscillator circuit 41P are transferred to the carrier wave frequency conversion circuit 38P for conversion. The carrier color signal C that has been supplied and has undergone low frequency conversion from the conversion carrier generation frequency conversion circuit 38P as described above.
_A carrier wave for conversion having a frequency of 3.58MHz + 743kHz, which should convert _L to the original frequency, is obtained.

Then, the carrier color signal Cs obtained at the output terminal 39P is supplied to the burst gate circuit 62, the burst signal in the carrier color signal Cs is extracted, and the burst signal is transferred to the phase comparison circuit 64.
The carrier wave obtained from the crystal oscillator circuit 41P is supplied to the phase comparison circuit 64P while being supplied to the phase comparison circuit 64P.
Is supplied to the loop filter 70P, and the output voltage of the loop filter 70P is supplied to the voltage controlled oscillator circuit 51P, so that the automatic phase control loop (APC loop) 66
And the phase of the carrier color signal Cs obtained at the output terminal 39P is corrected.

By the way, in the above-mentioned circuit device, the carrier color signal frequency conversion circuit 37R of the recording system, the conversion carrier generation frequency conversion circuit 38R, the voltage control crystal oscillation circuit 41R, the voltage control oscillation circuit 51R,
The phase comparison circuit 64R, etc. and the carrier color signal frequency conversion circuit 37P for reproduction system, the conversion carrier generation frequency conversion circuit 38P, the crystal oscillation circuit 41P, the voltage controlled oscillation circuit 51P, the phase comparison circuit 64P, etc. are each one circuit. It is desirable that they are used in common, and by using them in common, the circuit configuration for frequency conversion of the carrier color signal can be greatly simplified. Then, the recording loop filter 70R and the reproducing loop filter 70P
However, if one loop filter can also be used, the overall circuit configuration becomes even simpler.

D Problems to be Solved by the Invention However, when one loop filter is used as the loop filter 70R forming the phase locked loop 65 of the recording system and the loop filter 70P forming the automatic phase control loop 66 of the reproducing system, The DC gain of the loop filter becomes a problem.

That is, if the DC gain of the loop filter 70R that constitutes the phase locked loop 65 of the recording system is too large, the phase comparison circuit 6
When there is an offset in the output voltage of 4R, the loop filter
The output voltage of 70R becomes abnormally high and the phase locked loop 65
May not be locked and the oscillation frequency of the voltage controlled crystal oscillator circuit 41R may not be pulled to the expected 3.58MHz, so the DC gain of the loop filter 70R that constitutes the phase locked loop 65 of the recording system should not be too large. Is required. On the other hand, in order to sufficiently reduce the steady phase error of the reproduction carrier color signal, the automatic phase control loop 66 of the reproduction system is used.
It is necessary to sufficiently increase the DC gain of the loop filter 70P that composes the above. If the DC gain of the loop filter 70P is not sufficiently large, the steady phase error of the reproduced carrier color signal cannot be sufficiently reduced. And the loop filter 70
Even if the DC gain of P is sufficiently large, the frequency pull-in loop 96 including the frequency detection circuit 91 is configured for the voltage controlled oscillator circuit 51P during reproduction, so that the oscillation frequency of the voltage controlled oscillator circuit 51P is the desired value. Reliably pulled into frequency.

In view of such a point, the present invention realizes frequency conversion of a carrier color signal by combining a loop filter forming a phase locked loop of a recording system and a loop filter forming an automatic phase control loop of a reproducing system by one loop filter. In addition to simplifying the circuit configuration for that, the burst signal in the carrier color signal to be recorded from the voltage-controlled oscillation circuit that forms the phase-locked loop by reliably locking the phase-locked loop of the recording system at the time of recording The carrier wave synchronized with the carrier signal is surely obtained, and the phase correction of the reproduced carrier color signal is ensured by the automatic phase control loop of the reproducing system so that the steady phase error of the reproduced carrier color signal is sufficiently reduced.

E Means for Solving the Problems In the present invention, a first voltage controlled oscillator circuit for generating a carrier wave of an original sub-carrier frequency before low frequency conversion in a recording system,
Between the phase comparison circuit for phase-comparing the oscillation output of the first voltage-controlled oscillation circuit and the burst signal in the carrier color signal before low-frequency conversion, and between the phase comparison circuit and the first voltage-controlled oscillation circuit. A first loop filter, a second voltage controlled oscillator circuit for generating a carrier wave of a predetermined frequency proportional to the horizontal frequency, and a frequency for detecting the frequency of the oscillation output of the second voltage controlled oscillator circuit. A detection circuit; a second loop filter inserted or inserted between the frequency detection circuit and the second voltage control oscillation circuit; an oscillation output of the first voltage control oscillation circuit; A conversion carrier generation frequency conversion circuit that obtains a carrier for low-frequency conversion of a carrier color signal from the oscillation output of the second voltage control oscillation circuit, and a conversion carrier obtained from this conversion carrier generation frequency conversion circuit A carrier color signal frequency conversion circuit for converting the carrier color signal into a lower frequency band, a reference oscillation circuit for generating a carrier wave of the original subcarrier frequency before the lower frequency band conversion in the reproduction system, and a predetermined frequency proportional to the horizontal frequency. A voltage control oscillator circuit for generating a carrier wave of a frequency, a phase comparison circuit for phase comparing the oscillation output of the reference oscillation circuit and the burst signal in the carrier color signal after conversion to the original frequency, and this phase comparison circuit, A first loop filter inserted between the voltage control oscillator circuit, a frequency detection circuit for detecting the frequency of the oscillation output of the voltage control oscillator circuit, and a circuit between the frequency detection circuit and the voltage control oscillator circuit. A second loop filter that is inserted in or between the reference oscillation circuit and the oscillation output of the reference oscillation circuit and the oscillation output of the voltage controlled oscillation circuit, and converts the carrier color signal into the original frequency. And a carrier color signal for converting the carrier color signal, which has been low-pass converted by the carrier wave for conversion obtained from the carrier frequency converter for conversion, to the original frequency. In a video signal recording / reproducing apparatus having a frequency converting circuit, one phase comparing circuit serves as both the phase comparing circuit of the recording system and the phase comparing circuit of the reproducing system, and the first loop filter of the recording system and the above The first loop filter of the reproduction system is also used as a single loop filter, and the DC gain of the first loop filter that is also used is made smaller during recording than during reproduction.
Switch between recording and playback.

F. Operation According to the video signal recording / reproducing apparatus of the present invention configured as described above, the DC gain of the first loop filter does not become so large during recording when the first loop filter forms a phase locked loop. Therefore, even if there is an offset in the output voltage of the phase comparison circuit that constitutes the phase-locked loop,
The output voltage of the first loop filter does not become abnormally high, the phase-locked loop is reliably locked, and the carrier-color signal to be recorded from the first voltage-controlled oscillation circuit that constitutes the phase-locked loop. The carrier wave synchronized with the burst signal of is surely obtained, and the DC gain of the first loop filter becomes sufficiently large during the reproduction in which the first loop filter constitutes the automatic phase control loop. The phase of the carrier color signal is surely corrected, and the steady phase error of the reproduced carrier color signal becomes sufficiently small.

G Embodiment FIG. 1 shows an example of a video signal recording / reproducing apparatus according to the present invention.
The horizontal frequency is the subcarrier frequency of the carrier color signal after low frequency conversion.
A phase comparison circuit and a first loop filter that form a phase-locked loop of the recording system and a first loop filter and an automatic phase control loop of the reproduction system and a first loop that are 378/8 times f _H and 743 kHz Not only is the phase comparator circuit and the loop filter each used as a filter, but also the carrier color signal frequency conversion circuit of the recording system, the conversion carrier generation frequency conversion circuit, the first voltage controlled oscillation circuit, and the second
In this case, the voltage control oscillation circuit and the like, the carrier color signal frequency conversion circuit for the reproduction system, the conversion carrier generation frequency conversion circuit, the reference oscillation circuit, and the second voltage control oscillation circuit are also used in one circuit. .

In the recording system or during recording, the video signal before the recording process is obtained at the input terminal 11, and this video signal is supplied to the low-pass filter 12, and the luminance signal Y is supplied from the low-pass filter 12.
Is taken out, and this luminance signal Y is used as a pre-emphasis circuit.
It is supplied to the frequency modulation circuit 14 via 13 and the frequency modulation circuit 14 obtains a frequency-modulated luminance signal Ym occupying a predetermined band of a predetermined carrier frequency. Also, input terminal
The video signal obtained at 11 is supplied to the bandpass filter 16, and the subcarrier frequency from the bandpass filter 16 is 3.58.
The carrier color signal Cs of MHz is taken out, and this carrier color signal Cs is supplied to the carrier color signal frequency conversion circuit 37 through the switch 36 which is switched to the terminal R side at the time of recording, and the carrier frequency signal for conversion is converted as described later. Obtained from circuit 38
Low-frequency conversion carrier color signal C _L whose sub-carrier frequency is 743 kHz is obtained from carrier color signal frequency conversion circuit 37 by low-frequency conversion by the conversion carrier having a frequency of 3.58 MHz + 743 kHz.
Then, the frequency-modulated luminance signal Ym obtained from the frequency modulation circuit 14 and the low-frequency-converted carrier color signal C _L obtained from the carrier color signal frequency conversion circuit 37 are supplied to the combining circuit 18 and combined, and the combination thereof. The signal is led to the output terminal 19.
The composite signal of the frequency-modulated luminance signal Ym and the low-frequency-converted carrier color signal C _L obtained at the output terminal 19 is supplied to a rotary magnetic head (not shown) and tilted with respect to the running direction of the magnetic tape. Will be recorded on the track.

During playback system to play, reproduced from the track which is inclined with respect to the running direction of the magnetic tape, the composite signal of the carrier chrominance signal C _L which is the low-band converting the frequency modulated luminance signal Ym is the rotary magnetic head The synthesized signal obtained at the input terminal 21 is supplied to the high-pass filter 22, the frequency-modulated luminance signal Ym is extracted from the high-pass filter 22, and the frequency-modulated luminance signal Ym is output to the amplitude limiting circuit 23.
Is supplied to the frequency demodulation circuit 24 through the frequency demodulation circuit.
The output of 24 is supplied to the de-emphasis circuit 25, and the luminance signal Y is obtained from the de-emphasis circuit 25. Also,
The composite signal of the frequency-modulated luminance signal Ym and the low-pass-converted carrier color signal C _L obtained at the input terminal 21 is supplied to the low-pass filter 26, and the low-pass filter 26 changes the subcarrier frequency to 743 kHz. is range converted carrier chrominance signal C _L is taken out, the low-frequency converted carrier chrominance signal C _L is supplied to the carrier chrominance signal frequency converting circuit 37 through a switch 36 which is switched to the terminal P side at the time of reproduction, as described below 3.58MHz + 743 obtained from the conversion carrier generation frequency conversion circuit 38
It is converted to the original frequency by the carrier wave for conversion of the frequency of kHz, and the sub-carrier frequency is converted from the carrier color signal frequency conversion circuit 37.
A carrier color signal Cs of 3.58 MHz is obtained. Then, the luminance signal Y obtained from the de-emphasis circuit 25 and the carrier color signal Cs obtained from the carrier color signal frequency conversion circuit 37 are combined.
Is supplied to the output terminal 29 to be synthesized, and a reproduced video signal is derived from the output terminal 29.

In order to obtain the above-mentioned carrier wave for conversion during recording and playback, it becomes a voltage controlled oscillator circuit that should generate a 3.58MHz carrier wave during recording, and a voltage control that serves as a reference oscillator circuit that generates a stable 3.58MHz carrier wave during playback. Crystal oscillator circuit
41 and a voltage controlled oscillator circuit 51 for generating a carrier wave of 378f _H = 5.95MHz during recording and reproduction.

Then, at the time of recording, the carrier color signal Cs having a subcarrier frequency of 3.58 MHz supplied to the carrier color signal frequency conversion circuit 37 is supplied to the burst gate circuit 61 and the burst signal in the carrier color signal Cs is extracted, and the burst The signal is supplied to the phase comparison circuit 64 through the switch 63 which is switched to the terminal R side at the time of recording, and the voltage control crystal oscillation circuit 41
The carrier wave obtained from the above is supplied to the phase comparison circuit 64, the output voltage of the phase comparison circuit 64 is supplied to the loop filter 70 described later, and the output voltage of the loop filter 70 is recorded at the terminal R.
The phase-locked loop (PLL) is configured by being supplied to the voltage control crystal oscillation circuit 41 through the switch 42 that can be switched to the side, and the carrier wave obtained from the voltage control crystal oscillation circuit 41 becomes a burst signal in the carrier color signal Cs. It will be synchronized.

Further, the carrier wave obtained from the voltage controlled oscillator circuit 51 is supplied to the frequency divider circuit 53 and is divided into 1/378, and the frequency-divided carrier wave is supplied to the frequency detection circuit 81, and the low-pass filter 12 The luminance signal Y obtained from the above is supplied to the horizontal synchronizing signal separation circuit 82, the horizontal synchronizing signal in the video signal to be recorded is taken out, the horizontal synchronizing signal is supplied to the frequency detecting circuit 81, and the horizontal detecting signal of the frequency detecting circuit 81 A switch for supplying the output voltage to the loop filter 83 and switching the output voltage of the loop filter 83 to the terminal R side during recording.
By being supplied to the voltage controlled oscillation circuit 51 through 84, an automatic frequency control loop (AFC loop) is configured,
The frequency of the carrier wave obtained from the voltage controlled oscillator circuit 51 becomes 378 times the horizontal frequency f _H of the video signal to be recorded, and thus the frequency of the carrier wave obtained from the frequency divider circuit 53 is the horizontal frequency of the video signal to be recorded. to be equal to f _H.

And 378f _H = 5.95M obtained from the voltage controlled oscillator circuit 51
The carrier wave of Hz is supplied to the frequency dividing circuit 52 and is divided into 1/8,
743kHz frequency-divided carrier and voltage controlled crystal oscillator circuit
The 3.58 MHz carrier wave obtained from 41 is supplied to the conversion carrier wave generation frequency conversion circuit 38, and as described above, the carrier color signal Cs of the conversion carrier wave generation frequency conversion circuit 38 should be converted to the low frequency band of 3.58 MHz + 743 kHz. A carrier wave for frequency conversion is obtained.

At the time of reproduction, the carrier wave obtained from the voltage controlled oscillator circuit 51 is supplied to the frequency divider circuit 53 and divided into 1/378, and the frequency-divided carrier wave is supplied to the frequency detection circuit 91,
Luminance signal Y obtained from the aforementioned de-emphasis circuit 25
Is supplied to the horizontal sync signal separation circuit 92 to extract the horizontal sync signal in the reproduced video signal, the horizontal sync signal is supplied to the frequency detection circuit 91, and the output voltage of the frequency detection circuit 91 is supplied to the loop filter 93. , A switch for switching the output voltage of the loop filter 93 to the terminal P side during reproduction
By being supplied to the voltage controlled oscillator circuit 51 through 94, a frequency pull-in loop for the voltage controlled oscillator circuit 51 is formed, and the frequency of the carrier wave obtained from the voltage controlled oscillator circuit 51 is 378 times the horizontal frequency f _H of the reproduced video signal. Therefore, the frequency of the carrier wave obtained from the frequency dividing circuit 53 is made equal to the horizontal frequency f _H of the reproduced video signal.

During reproduction, the switch 42 is switched to the terminal P side and a predetermined voltage from the power supply 43 is supplied to the voltage control crystal oscillation circuit 41 through the switch 42, so that the voltage control crystal oscillation circuit 41 stabilizes at 3.58 MHz. Carrier wave is obtained. Then, 378f _H obtained from the voltage controlled oscillator circuit 51 is
The 5.95MHz carrier wave is supplied to the frequency divider circuit 52 and is divided into 1/8, and the divided 743kHz carrier wave and the 3.58MHz carrier wave obtained from the voltage controlled crystal oscillator circuit 41 are the conversion carrier wave generation frequency. 3.58MHz + 743kHz which should be supplied to the conversion circuit 38 and converted into the original frequency of the carrier color signal C _L which has been low-frequency converted by the conversion carrier generation frequency conversion circuit 38 as described above.
A carrier wave for converting the frequency is obtained.

Then, the carrier color signal Cs having a subcarrier frequency of 3.58 MHz obtained from the carrier color signal frequency conversion circuit 37 is supplied to the burst gate circuit 62, the burst signal in the carrier color signal Cs is extracted, and the burst signal is reproduced. It is supplied to the phase comparison circuit 64 through the switch 63 that can be switched to the terminal P side, the carrier wave obtained from the voltage controlled crystal oscillation circuit 41 is supplied to the phase comparison circuit 64, and the output voltage of the phase comparison circuit 64 is the loop filter described later. The output voltage of the loop filter 70 is supplied to the voltage-controlled oscillation circuit 51 through the switch 84 which is switched to the terminal P side at the time of reproduction, so that the automatic phase control loop (APC loop)
And the phase of the carrier color signal Cs obtained from the carrier color signal frequency conversion circuit 37 is corrected.

The loop filter 70 includes, for example, a low-pass filter 71 to which the output voltage of the phase comparison circuit 64 is supplied, a low-pass filter 72 to which the output voltage of the low-pass filter 71 is supplied, an output voltage of the low-pass filter 71, and an output of the low-pass filter 72. And an adder circuit 79 for adding voltages. The low-pass filter 71 has a flat frequency characteristic as shown in FIG. 2 in which the cutoff frequency f ₁ is several tens of kHz. The low-pass filter 72 is connected between, for example, an operational amplifier circuit 73 having a gain of 1 / X in which the output voltage of the low-pass filter 71 is supplied to a non-inverting input terminal, and an output terminal of the operational amplifier circuit 73 and ground. A capacitor 74 having a capacitance of C, an amplifier circuit 75 having a gain of 1 to which the terminal voltage of the capacitor 74 is supplied, and a gain of 1 /
It is composed of an attenuation circuit 76 for A and a switch 77 for connecting the attenuation circuit 76 between the output terminal of the amplification circuit 75 and the inverting input terminal of the operational amplification circuit 73 during recording, and the switch 77 is on the terminal R side during recording. To the terminal P side during reproduction.

Assuming that the input voltage of the low-pass filter 72 is Vi and the output voltage is Vo, the switch 77 is switched to the terminal R side during recording as described above, so that the output terminal of the amplifier circuit 75 and the operational amplifier circuit.
Since the attenuation circuit 76 is connected between the inverting input terminal of 73, Next to Becomes Therefore, the transfer function of the low-pass filter 72 during recording is Becomes On the other hand, at the time of reproduction, the switch 77 has the terminal P.
When the low pass filter 72 is reproduced, the transfer function is as follows: Becomes

Therefore, the frequency characteristic of the low-pass filter 72 is such that, at the time of recording, as shown by the solid line 1R in FIG. 3, at a frequency higher than f ₂ = 1 / 2πCXA, the gain becomes larger as the frequency becomes lower, but f ₂
At the frequencies below, the gain is kept constant,
At the time of reproduction, as shown by the broken line 1P in FIG. 3, the lower the frequency is, the larger the gain is, even if the frequency is f ₂ or less. Therefore, the frequency characteristics of the loop filter 70, the time of recording, as shown by the solid line 2R of FIG. 4, f ₃ between f ₁ is a cut-off frequency of greater than f ₂ f ₂ with the above-mentioned low-pass filter 71 the gain increases as the frequency is lower at lower frequencies, it is assumed that the gain is suppressed to a constant in the f ₂ frequencies below, during playback, as shown by the dashed line 2P of FIG. 4, f containing f ₂ or less _At frequencies below _{3, the} lower the frequency, the greater the gain. In this case, f ₂ is selected to be several Hz and f ₃ is selected to be several 10 Hz. Therefore, the gain of the loop filter 70 at several Hz or less, that is, the DC gain does not become so large at the time of recording, but becomes sufficiently large at the time of reproduction.

As described above, since the DC gain of the loop filter 70 does not become so large during recording when the loop filter 70 constitutes a phase locked loop, even if the output voltage of the phase comparison circuit 64 constituting the phase locked loop has an offset, the loop The output voltage of the filter 70 does not become abnormally high, the phase-locked loop is reliably locked, and the carrier wave is supplied from the voltage-controlled crystal oscillation circuit 41 forming the phase-locked loop to the carrier color signal frequency conversion circuit 37. A carrier wave synchronized with the burst signal in the color signal Cs can be reliably obtained. Further, during reproduction in which the loop filter 70 constitutes an automatic phase control loop, the DC gain of the loop filter 70 becomes sufficiently large, so the phase correction of the carrier color signal Cs obtained from the carrier color signal frequency conversion circuit 37 by the automatic phase control loop is performed. And the steady phase error of the carrier color signal Cs obtained from the carrier color signal frequency conversion circuit 37 becomes sufficiently small.

H According to the present invention, the circuit configuration for frequency conversion of the carrier color signal is simplified, and at the time of recording, the first voltage controlled oscillation circuit, the phase comparison circuit and the first loop filter of the recording system are provided. The phase-locked loop including is surely locked, the carrier wave synchronized with the burst signal in the carrier color signal to be recorded is surely obtained from the first voltage controlled oscillation circuit, and the reference oscillation circuit and the phase comparison circuit of the reproduction system are provided. The phase correction of the reproduced carrier color signal is surely performed by the automatic phase control loop including the first loop filter and the voltage controlled oscillator circuit, and the steady phase error of the reproduced carrier color signal is sufficiently reduced.

[Brief description of drawings]

FIG. 1 is a connection diagram showing an example of a video signal recording / reproducing apparatus according to the present invention, and FIGS. 2, 3, and 4 are frequency characteristics of a low-pass filter and a whole loop filter constituting a loop filter of the main part thereof. Showing FIG. 5, FIG. 5 and FIG.
FIG. 1 is a connection diagram showing a circuit device for frequency conversion of carrier color signals in a recording system and a reproducing system as an example of a conventional video data recorder. In the figure, 37 is a carrier color signal frequency conversion circuit, 38 is a conversion carrier generation frequency conversion circuit, 41 is a voltage controlled crystal oscillation circuit,
51 is a voltage controlled oscillation circuit, 64 is a phase comparison circuit, 70 is a loop filter, 81 and 91 are frequency detection circuits, and 83 and 93 are loop filters.

Claims (1)

[Claims] 1. A first voltage controlled oscillator circuit for generating a carrier wave of an original sub-carrier frequency before low frequency conversion in a recording system,
Between the phase comparison circuit for phase-comparing the oscillation output of the first voltage-controlled oscillation circuit and the burst signal in the carrier color signal before low-frequency conversion, and between the phase comparison circuit and the first voltage-controlled oscillation circuit. A first loop filter, a second voltage controlled oscillator circuit for generating a carrier wave of a predetermined frequency proportional to the horizontal frequency, and a frequency for detecting the frequency of the oscillation output of the second voltage controlled oscillator circuit. A detection circuit; a second loop filter inserted or inserted between the frequency detection circuit and the second voltage control oscillation circuit; an oscillation output of the first voltage control oscillation circuit; A conversion carrier generation frequency conversion circuit that obtains a carrier for low-frequency conversion of a carrier color signal from the oscillation output of the second voltage control oscillation circuit, and a conversion carrier obtained from this conversion carrier generation frequency conversion circuit It has a carrier color signal frequency conversion circuit that converts the carrier color signal to a lower frequency band, and a reference oscillator circuit that generates a carrier wave of the original sub carrier parallel frequency before low frequency conversion in the reproduction system, and a proportional to the horizontal frequency. A voltage control oscillation circuit for generating a carrier wave of a predetermined frequency, a phase comparison circuit for performing phase comparison between the oscillation output of the reference oscillation circuit and the burst signal in the carrier color signal converted to the original frequency, and this phase comparison circuit A first loop filter interposed between the voltage control oscillator circuit and the voltage control oscillator circuit, and a frequency detection circuit that detects the frequency of the oscillation output of the voltage control oscillator circuit.
A second loop filter inserted or interposed between the frequency detection circuit and the voltage controlled oscillator circuit;
A frequency conversion circuit for generating a carrier wave for conversion, which obtains a carrier wave for converting the carrier color signal which has been low-frequency converted to the original frequency from the oscillation output of the reference oscillation circuit and the oscillation output of the voltage control oscillation circuit, and this conversion. A carrier color signal frequency conversion circuit for converting the carrier color signal, which has been low-frequency converted by the conversion carrier wave obtained from the carrier wave generation frequency conversion circuit, to the original frequency, and has the recording system phase comparison circuit and the reproduction system. The phase comparison circuit of the system is also used by one phase comparison circuit, and the first loop filter of the recording system and the first loop filter of the reproduction system are also used by one loop filter and are also used as this. A video signal recording / reproducing apparatus capable of switching between recording and reproducing so that the DC gain of the first loop filter is smaller during recording than during reproduction.