JPS6193794A - Color signal processor - Google Patents

Abstract

PURPOSE:To simplify circuits and to obtain a PLL with high performance by using a burst of a low-frequency conversion chrominance carrier signal subjected to low-frequency conversion to be recorded on a magnetic tape and a burst of a low frequency conversion color signal reproduced from the magnetic tape for switching. CONSTITUTION:The control input of the 1st signal generating circuit 1 is switched by using a signal from the 1st phase comparator circuit 3 and a signal from the 2nd phase comparator circuit 19 at the 1st signal switching circuit 7 depending on recording and reproduction. The control input of the 2nd signal generating circuit 2 is switched by using a signal from the circuit 19 and a control signal fixed from a constant voltage circuit 6 at the 2nd signal switching circuit 8. The burst of the low-frequency converting color signal inputted to the circuit 19 is switched by using the burst of the low-frequency converting color signal subject to low-frequency conversion recorded on the magnetic tape and the burst of the low-frequency converting color signal reproduced from the magnetic tape by the 3rd signal switching circuit 20.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a color signal that performs frequency conversion of a carrier color signal in a recording system or a reproducing system of a color VTR in which the carrier color signal is recorded after low-frequency conversion. It relates to a processing device.

Conventional configuration and its problems In a conventional color VTR, for example, when recording a color video signal of the NTSC system using the rH3 system, a carrier color signal with a color subcarrier frequency of fso (= 3.58 MHz) is used. is supplied to a frequency conversion circuit for both recording and reproduction, and is low-band converted to a low-band converted color signal with a low-band color subcarrier frequency of f (C = 629 KHz), and is FM-modulated with this low-band converted color signal. The mixed luminance signal is recorded on a magnetic tape.

In addition, when reproducing the signal recorded on this magnetic tape, the low frequency converted color signal in the reproduced signal is
The signal is supplied to a frequency conversion circuit that also serves as a reproduction, and is converted to the original carrier color signal with a color subcarrier frequency of fso, and is added to the FM demodulated luminance signal to output it as an NTSC color video signal. .

A conventional example of a frequency conversion system for recording and reproducing in a color signal processing apparatus as described above will be explained with reference to FIG.

At the time of recording, the carrier frequency signal is separated from the color video signal from the input terminal 15. A carrier color signal is provided.

The above carrier color signal is transmitted through a frequency conversion circuit (CON V(It)
) 1 and 2, and the frequency conversion circuit 12 is supplied with a frequency that is the sum of the color subcarrier frequency fsc and the low frequency conversion color subcarrier frequency fc from the frequency conversion circuit (CONV(I)) 11. A signal of 10 f0 is supplied, and the output of the frequency conversion circuit 12 has a carrier frequency of fsc + fc + f. −
2-'S O+IC signal and fsc +fc J'S
A signal that is the sum of the signals C=fc appears. The output signal of the frequency conversion circuit 12 is passed through a low pass filter (LPF) 13.
A low frequency converted color signal for recording with a color subcarrier frequency fo is extracted at the output terminal 16. Next, a method of creating a signal with a frequency 'sa + IC outputted from the frequency conversion circuit 11 will be explained. First signal generation circuit (VCO) 1
is a voltage controlled oscillator that oscillates at a frequency eight times that of fo when recording and reproducing an NTSC color video signal using the VH3 system, and its control is performed by the output of the switching circuit 7. During recording, the signal switching circuit The output of the first phase comparator (Pc1) 3 is given to the output of the first phase comparator (Pc1). The phase comparator 3 compares the horizontal synchronizing signal of frequency 9 inputted from the input terminal 18 with a signal obtained by dividing the output of the first signal generating circuit 1 by 1/320 with a dividing period (1/n) of 10. Outputs the comparison result as a voltage. During recording, a phase-locked loop (hereinafter referred to as PLL) consisting of the above-mentioned phase comparison circuit 3, switching circuit 7, first signal generation circuit 1, and frequency dividing circuit 10 is used. A signal with a frequency of 320fH is generated by a signal generation circuit (P
S/PI) 5 to divide the frequency and shift the phase by 96 every horizontal period to obtain a frequency of 10 (40Xf in the case of VH3 system).
= 629KH2) is created and is input to one side of the frequency conversion circuit 11. Even when recording in the Beta format or recording color video signals other than the NTSC format, the same effect can be achieved by changing the division ratio of the division period 10 and changing the signal generation circuit 5 to a circuit that performs phase inversion processing. A low-pass conversion color subcarrier is created in the process. The second signal generating circuit (VXO) 2 is a voltage controlled oscillator with a small frequency variable range controlled by a crystal, and oscillates at the color subcarrier frequency fBo. The oscillation frequency of the signal generating circuit 2 is controlled by the output of the switching circuit 8, and the output of the second phase comparator circuit 4 is applied during recording. The switching circuit 9 is a switching circuit for a signal input to one input of the phase comparator (PO2) 4, and the carrier color signal input from the input terminal 15 is applied to one input of the phase comparator 4 during recording.

The oscillation output of the signal generation circuit 2 is given to the other input of the phase comparison circuit 4, where the burst of the carrier color signal and the oscillation output of the signal generation circuit 2 are phase-compared, and the comparison result is converted into a voltage. The signal is supplied to the signal switching circuit 8. As mentioned above,! During recording, the phase comparison circuit 4, signal switching circuit 8, and signal generation circuit 2 constitute another PLL,
The output of the signal generation circuit 2 is a signal with a frequency fsc that is phase synchronized with the color subcarrier of the carrier color signal supplied to the input terminal 15, and is supplied to the other input of the frequency conversion circuit 11. f. and f. The frequency conversion circuit 11- generates a signal with a frequency fB6+f0, which is used for low-frequency conversion of the carrier color signal in the recording wave number conversion circuit 12, from the two frequency signals.

Next, the operation during playback will be explained. During playback, the input terminal 16 receives a low-range color subcarrier frequency 10 separated from the playback signal.
A low frequency converted color signal is supplied. The above-mentioned low frequency conversion color signal is supplied to the frequency conversion circuit 12, and the frequency conversion circuit 12 converts the frequency signal from the frequency conversion circuit 11 to the frequency as in the case of recording. +fa signal is supplied, and the output of the frequency conversion circuit 12 has a carrier frequency of fB0+fc + fa = fB,
3 + 2 fa signal and fsc + fc fc = f
A signal that is the sum of the ac signals appears. The output signal of the frequency conversion circuit 12 passes through a bandpass filter 14, and during reproduction, a carrier color signal with a carrier frequency fs0 is extracted at an output terminal 17. The method of creating the signal of frequency fs0+fo output from the frequency conversion circuit 11 is slightly different from that during recording. First, since the frequency control input of the signal generation circuit 2 is given to the switching circuit 8 by the constant voltage circuit (REF) a, the signal generation circuit 2 becomes a fixed oscillator that oscillates at the reference color subcarrier frequency of 18 degrees. The oscillation output of 2 is supplied to one input of the frequency conversion circuit 11 as a reference color subcarrier. Further, the signal generation circuit 1 is controlled by the output signal of the phase comparator circuit 4 via the signal switching circuit 7.

The phase comparator circuit 4 is frequency-converted by a frequency conversion circuit 12 via a switching circuit 9, and then connected to a band-pass filter (BP).
F) The carrier color signal extracted in 14 and the signal generation circuit 2
A reference color subcarrier is supplied from the carrier color signal, and the burst of the carrier color signal and the reference color subcarrier are phase-compared and the phase error is output as a voltage. The oscillation output of the signal generation circuit 1 controlled by the phase error voltage of the phase comparator circuit 4 is subjected to frequency division and phase shift processing in a phase inversion circuit 6. The signal is supplied to the frequency conversion circuit 11 as a signal. As mentioned above, the signal is generated by the closed loop composed of the phase comparator circuit 4, the signal switching circuit 7, the signal generating circuit 1, the signal generating circuit 5, the frequency converting circuit 11, the frequency converting circuit 12, the bandpass filter 14, and the switching circuit 9. During reproduction, the carrier frequency of the carrier color signal output from the output terminal 17 is determined by the signal generator circuit 1.
The subcarrier is controlled to be synchronized with the reference color subcarrier output from the subcarrier.

The frequency conversion system of the color signal processing device in the conventional color "/TH" recording or reproducing system in which the carrier color signal is low frequency converted and recorded has been described above. The phase comparator circuit 3 compares the rising or falling edges of the two inputs and determines the H level of the signal.
, L and a high impedance state, and smooths the state with a low-pass filter to obtain a phase comparison output.
The method used is to multiply the two inputs using a multiplier only during the burst period, and after rectifying the multiplication result, smooth it using a pass filter.
Since the frequency is as high as 3.58 MHz in the NTSC system, it has the disadvantage that the circuit configuration is extremely complicated in order to obtain a predetermined performance. Furthermore, in recent years, there has been a trend in color signal processing devices to improve device performance, reduce power consumption, and reduce external components by digitizing or MO5IC the part that conventionally performed analog processing. Regarding circuit 4, it has been difficult to realize it for the same reasons as the drawbacks mentioned above.

OBJECTS OF THE INVENTION The purpose of the present invention is to improve the color subcarrier frequency, which was a drawback in the conventional example. It is possible to perform phase comparison at low conversion frequency 10, simplifying the part corresponding to the phase comparison circuit at conventional frequency fsC and improving performance, and making it suitable for digital conversion. An object of the present invention is to provide a color signal processing device.

Structure of the Invention The present invention provides an i
Wow... □□. Kakaega. Ayo, wa8. □.

a signal generation circuit that generates a low frequency conversion carrier wave from the signal generation circuit; a second signal generation circuit that generates a signal with a frequency that is an integral multiple of the color subcarrier frequency; a first phase comparison circuit that compares the phases of the frequency-divided signal of the signal and the horizontal synchronization signal, and a second phase comparison circuit that compares the phases of the burst of the low-frequency conversion color signal and the low-frequency conversion carrier wave from the signal generation circuit. a constant voltage circuit that provides a fixed control signal whose reference frequency is the frequency of the second signal generating circuit; Second. The first signal switching circuit switches the control input of the first signal generating circuit between the signal from the first phase comparator circuit and the second signal switching circuit during recording and reproduction. Switching with the signal from the phase comparator circuit,
The second signal switching circuit switches the control input of the second signal generation circuit between the signal from the second phase comparison circuit and the fixed control signal from the constant voltage circuit, and the third signal switching circuit switches the control input of the second signal generation circuit between the signal from the second phase comparison circuit and the fixed control signal from the constant voltage circuit. The burst of the low-pass converted color signal input to the second phase comparator circuit is recorded on the magnetic tape. This is used to create a signal for frequency conversion in the recording system or reproduction system of a color VTR.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram of a color signal processing device in one embodiment of the present invention. In FIG. 2, 1 is the first signal generation circuit (VCO), 2 is the second signal generation circuit (VXO), and 3
5 is the first phase comparison circuit (PCl), and 5 is the signal generation circuit (
6 is a constant voltage circuit (RKF), 7 is a first signal switching circuit, 8 is a second signal switching circuit, 1o is a frequency dividing circuit (1/n), 11.12 is a frequency conversion circuit (CONV
(I)), (CONV(II)).

13 is a low-pass filter (LPF), 14 is a band-pass filter (BPF), 16 is a signal input terminal, 16 is a recording color signal output terminal, 17 is a reproduction color signal output terminal, 18 is a horizontal synchronizing signal input terminal, and 19 is a horizontal synchronization signal input terminal. 2 phase comparator circuit (P
O2), 20 is a third signal switching circuit.

The operation of the color signal processing device of this embodiment configured as described above will be described below.

During recording, the input terminal 15 goes to the carrier frequency. Further, the frequency conversion circuit 12 is supplied with a carrier color signal of a frequency f, from the frequency conversion circuit 11. +fC signal is supplied, and the output of the frequency conversion circuit 12 has a carrier frequency of 7ISc+f.
0+f8o-2fs0+f6 signal. +f0-f,
. =f appears, the output signal of the frequency conversion circuit 12 passes through the low-pass filter 13, and a low-pass conversion color signal for recording at the carrier frequency is extracted at the output terminal 16. Frequency f from the frequency conversion circuit 11
11 (+ + fG signal is a low frequency conversion color subcarrier of frequency 10 from the signal generation circuit 6 and the second signal generation circuit
The frequency f, from . is obtained by multiplying the signals by the frequency conversion circuit 11.

For the low frequency conversion color subcarrier of frequency 10, the phase comparison circuit 3 compares the phase of the horizontal synchronizing signal from the input terminal 18 and the signal obtained by dividing the oscillation output of the signal generation circuit 10 by the frequency dividing circuit 10, and the comparison result is switched. By being supplied to the frequency control input of the signal generation circuit 1 through the circuit 7, a signal with a frequency n7''H, which is an integer multiple of 90 horizontal synchronization frequency, is obtained from the signal generation circuit 1, and the signal nA is The signal generation circuit 5 performs frequency division and phase shift or phase inversion processing to generate the signal.The oscillation frequency of the second signal generation circuit 2, which oscillates at the color subcarrier frequency fs0, is controlled by the output of the switching circuit 8. During recording, the output of the phase comparison circuit 19 is given.

The switching circuit 20 is a switching circuit for the signal supplied to one input of the phase comparator circuit 19, and during recording, the switching circuit 20 switches the signal supplied to one input of the phase comparator circuit 19.
The recording low frequency conversion color signal from 3 is applied to one input of the phase comparison circuit 19 through the switching circuit 20. The other input of the phase comparison circuit 19 is given the low frequency conversion carrier wave from the signal generation circuit 5, and here the burst of the low frequency conversion color signal for recording and the low frequency conversion carrier wave from the signal generation circuit 5 are in phase. The comparison result is supplied to the switching circuit 8.

During recording, the above-mentioned phase comparison circuit 19 and switching circuit!
8, signal generation circuit 2, frequency conversion circuit 11, frequency conversion circuit 12, low pass filter 13, and switching circuit 2
PI and L are configured in a closed loop consisting of o, and are controlled so that the carrier wave of the low-pass conversion color signal supplied to the terminal 16 has the same phase and the same frequency as the low-pass conversion color subcarrier created by the signal creation circuit 5. are doing.

Next, the operation during playback will be explained. During reproduction, the input terminal 16 is supplied with a low frequency converted color signal having a low frequency subcarrier frequency of 10, which is separated from the reproduction signal from the magnetic tape. The low frequency conversion color signal is supplied to the frequency conversion circuit 12, and the frequency conversion circuit 12 is further supplied with a signal of frequency f8°+10 from the frequency conversion circuit 11.
The output has a carrier frequency of 8. +f0+f0=f,c+
210 signal and f. +f, -f0=f,. A signal of the sum of the signals appears and passes through a bandpass filter 14 to an output terminal 17 to the color subcarrier frequency. The carrier color signal of is extracted.

To the frequency output from frequency conversion circuit A1. To create the +4 signal, first, it is passed through the switching circuit 8 as the frequency control input of the signal generating circuit 2, and since the output of the constant voltage circuit 6 is given, the signal generating circuit 2 changes to the reference color subcarrier frequency. A fixed oscillator that oscillates at
The oscillation output of is supplied to one input of the frequency conversion circuit 11. Further, the signal generation circuit 1 is controlled by the output of the phase comparator circuit 19 via the switching circuit 7. The phase comparator circuit 19 receives the burst portion of the low frequency conversion color signal supplied from the input terminal 16 via the switching circuit 2o, and the signal generating circuit 5.
The phases of the low-pass conversion color subcarriers created in are compared, and the comparison results are output as voltages.

The PLL operation is performed by a closed loop constituted by the phase comparison circuit 19, switching circuit 7, signal generation circuit 1, signal creation circuit 6, frequency conversion circuit 11, frequency conversion circuit 12, bandpass filter 14, and switching circuit 2o. During reproduction, the signal generating circuit 1 is controlled so that the carrier frequency of the carrier color signal outputted from the output terminal 17 is synchronized with the reference color subcarrier outputted from the signal generating circuit 2.

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

FIG. 3 is a block diagram of a color signal processing device in another embodiment of the present invention. In Fig. 3, 1 is the first signal generation circuit (VCO), 5 is the signal generation circuit (PS/PI), and 6
is a constant voltage circuit (REF), 7 is a first signal switching circuit,
8 is the second signal switching circuit, 1o is the frequency dividing circuit, 11.12
is the frequency conversion circuit (CONV(1)), (CONV(n
)), 13 is a low pass filter (LPF), 16 is a signal input terminal, 16 is a recording color signal output terminal, 17 is a reproduction color signal output terminal, 18 is a horizontal synchronizing signal input terminal, and 20 is a third
21 is a MU/D converter (MU/D); 22 is a signal switching circuit;
is a digital demodulation circuit (DXCODX), 23゜24 is a digital comb filter (COMB), 26 is an encoder (EN (ljODI), 26 is a D/A converter (D/A)
, 27 is a band pass filter (BPF), 28 is a control voltage generation circuit (PO2), and 29 is a second signal generation circuit (v
xO), 30 is an A frequency dividing circuit (1/4). .

The operation of the color signal processing device according to another embodiment of the present invention configured as described above will be described below.

During recording, carrier frequency 18. A carrier color signal of 10 is supplied, passes through a frequency conversion circuit 12 and a low-pass filter 13, and a low-pass conversion color signal converted to a low-pass conversion frequency of 10 is extracted at an output terminal 16. The frequency conversion circuit 12 receives, in addition to the carrier color signal, a low frequency conversion color subcarrier from the frequency conversion circuit 11 with a frequency of 10 created by the signal creation circuit 5 and a frequency f from the A frequency dividing circuit 30. A signal with a sum frequency fsa+fa of the multiplication results of color subcarriers is supplied. The method of creating the low-pass conversion color subcarrier of frequency fc is exactly the same as in the prior art or the first embodiment of the present invention.

to frequency. The method for creating color subcarriers differs from the first embodiment in that an A/D converter 21, a digital demodulation circuit 22, a digital comb filter 24, and a control voltage are used instead of the second phase comparison circuit 19 in the first embodiment. The creation circuit 28 performs almost the same operation. First, the switching circuit 20 converts the low-pass converted color signal after passing through the low-pass filter 13 to the A/D converter 2.
Here, sampling and Mu/D conversion are performed at a frequency 4f0 that is four times the low frequency conversion frequency 10. The oscillation output of the first signal generation circuit 1 is used as the sampling clock of the A/D converter. A/D
The low frequency converted color signal converted into digital data by the converter 21 is converted into two color difference signal data B- by the digital demodulation circuit 22.
Separated into Y and RY. The digital demodulation circuit 22 receives a frequency f from the signal generation circuit 5. A sampling clock with a frequency of 4.7G is supplied from the low-pass conversion color subcarrier and the signal generation circuit 1, and when the burst of the low-pass conversion color coefficient and the low-pass conversion color subcarrier are synchronized, the low-pass conversion The result of sampling the low frequency conversion color signal with a clock having a frequency four times that of the color subcarrier is the color difference signal components B-Y and R-Y.

The data is separated into two color difference signal data by taking advantage of the fact that the data is a repetition of -(B-Y) and -(R-Y).

The two separated color difference signal data B-Y.

R-Y is added to the data from one horizontal period or two horizontal periods ago by digital comb filters 23 and 24, and the addition result becomes color difference signal data (B-Y)', (R-Y)', which is applied to the control voltage. It is supplied to the creation circuit 28. The digital comb filters 23 and 24 are used during reproduction, and may not be used during recording, and the output data R-Y, B-Y of the digital demodulation circuit 23 may be directly supplied to the control voltage generation circuit 28. The control voltage generation circuit 28 is composed of an arithmetic circuit, a D/inverter converter, a filter, etc., and the control voltage generation circuit 28 is configured to calculate the output voltage of the A/D converter 21 and the digital demodulation circuit 22 from the value of the burst section of the color difference signal data of the low frequency converted color signal. A phase error between the demodulation tie and the low frequency conversion color signal is detected, a voltage corresponding to the phase error is created, and is supplied to the second signal generation circuit 29 via the signal switching circuit 8 to change the oscillation frequency. control. A second signal generating circuit 29 outputs the color subcarrier frequency. The oscillation output is divided by the A frequency divider circuit 30 to obtain a frequency f. Frequency conversion circuit 11 as the color subcarrier of
is supplied to During recording, the frequency conversion circuit 11 described above
, frequency conversion circuit 12, low-pass filter 13, signal switching circuit 20. A/D converter 21, digital demodulation circuit 22
, digital comb filter 24, control voltage generation circuit 28
, signal switching circuit 8, signal generation circuit 29, A frequency dividing circuit 30
The PLL consists of a closed loop consisting of This is a method of creating a voltage corresponding to a phase error in the control voltage creation circuit 28. For example, when recording and reproducing an NTSC color video signal, a burst is created by generating a voltage of a certain size in one direction of the B-Y component of the color difference signal. It is also possible to create the (RY)' data, which has a vector and does not contain a redundant component, by directly converting it to D/person and then passing it through an analog low-pass filter, or to create the color difference signal data (RY)', (B -Y )', if t, nθ=<R-Yy/<B-y)' is calculated digitally, θ becomes the phase error itself, and the voltage corresponding to θ may be D/A converted. By inserting a digital zero-order hold filter before D/A conversion, it is possible to omit the analog low-pass filter after D/A conversion, and by using a cyclic digital filter, it is possible to It is also possible to calculate and output the average of errors.

By operating the above-mentioned PLL, the color difference signal data (R-Y)' that has been separated by the digital demodulation circuit 22 and passed through the digital comb filter becomes OK or ta
nθ=(R-Y)//(B-Y)'=.

The oscillation frequency or oscillation phase of the signal generation circuit 29 is controlled so that As a result, the burst of low-frequency conversion color signals outputted from the terminal 16 becomes synchronized with the low-frequency conversion carrier wave created by the signal creation circuit 5.

Next, the operation during playback will be explained. In another embodiment of the present invention, the frequency conversion circuits 11 and 12 are not used during reproduction, and the reproduction low-frequency conversion color signal inputted from the terminal 15 is supplied to the A/D converter 21 via the signal switching circuit 20. ,A/
The D-converted reproduced low-frequency conversion color signal is separated into R-Y and B-Y by the digital demodulation circuit 22, as in the case of recording, and then added to the previous data by 1H by the digital comb filters 23 and 24. (RY)'l (B-Y)' is supplied to the encoder 26. The encoder 25 also has a color subcarrier frequency f. A flock with a frequency of 4f5°, which is four times as large as
/'JIKI-j:"°"04 Since the reference voltage is applied from the constant voltage circuit 6 via the signal switching circuit 8, the signal generating circuit 29 uses the reference carrier frequency f. It oscillates at four times as much.

The encoder 25 generates the color difference signal data (RY)' based on the oscillation clock from the signal generating circuit 29.

(B-Y)' and the color difference signal data (R-Y)'.

(B-Y)' is digitally inverted (R-Y
)', -(B -Y)', respectively (RY)'+ (B -Y)', -(R-
Y )', -(B-Y)' are repeatedly output in the order, and this repeated data is converted into an analog value by the D/A converter 26 to the carrier frequency. A reproduced carrier color signal of The bandpass filter 27 removes harmonics from the digitally modulated reproduced carrier color signal, and the final reproduced carrier color signal is extracted from the terminal 17.

In order for the carrier frequency of the reproduced carrier color signal to become a jitter-free reference frequency, it is necessary for the A/D converter 21 and the digital demodulation circuit 22 to accurately separate the low-frequency converted color signal into two color difference signals. However, during recording, the error voltage from the control voltage generation circuit 28 that was supplied to the signal generation circuit 29 is transferred to the signal generation circuit 1 via the signal switching circuit 7.
By supplying it to the frequency control input of
A PLL is configured by the signal generation circuit 5 and a low frequency conversion carrier wave synchronized with the burst of the reproduced low frequency conversion color signal and a frequency 4fc that is four times the frequency fc of the low frequency conversion carrier wave.

The clock for D/D conversion is obtained.

Effects of the Invention As is clear from the above description, the present invention includes a first signal generating circuit that generates a signal with a frequency that is an integral multiple of the low-pass conversion color subcarrier frequency, and a signal generating circuit that generates a signal from the first signal generating circuit. a signal generation circuit that generates a low-frequency conversion carrier wave, a second signal generation circuit that generates a signal with a frequency that is an integral multiple of the low-frequency conversion carrier frequency, and a frequency-divided signal of the signal from the first signal generation circuit and a horizontal a first phase comparison circuit that compares the phases of the synchronization signals;
a second phase comparison circuit that compares the phases of the burst of the low-frequency conversion color signal and the low-frequency conversion carrier wave from the signal generation circuit; and a fixed control voltage whose reference frequency is the frequency of the second signal generation circuit. A constant voltage circuit that provides the first voltage. Second. Third
The first signal switching circuit converts the control input of the first signal generation circuit between the signal from the first phase comparator circuit and the second phase signal during recording and playback. The second signal switching circuit ′ switches the control input of the second signal generation circuit between the signal from the second phase comparison circuit and the fixed control signal from the constant voltage circuit. The third signal switching circuit records the burst of the low-pass converted color signal input to the second phase comparator circuit on the magnetic tape. Since it is configured to switch between bursts of low-frequency conversion color signals reproduced from Since this is carried out at a high frequency (629 KHz in the VH5 system), the circuit is simple and a PLL with good performance can be obtained.

Further, when the second phase comparison circuit has a demodulation circuit and is configured to perform a phase comparison of ≧ the value of the burst interval of the two demodulated color signals, various phase comparison methods can be considered.
It has the effect of increasing the degree of freedom in design, and can be realized by low-speed digital sampling demodulation, making it suitable for digitalization.

However, as a method of frequency conversion during reproduction, if a method is used in which a low frequency converted color signal is demodulated into two color difference signals using a single carrier demodulation circuit, and then a quadrature two-phase balanced modulated wave is created at a predetermined carrier frequency, the above-mentioned This has the effect that the demodulation circuit of the second phase comparator circuit can also be used as a demodulation circuit for demodulating the low frequency converted color signal into two color difference signals, and the circuit can be omitted.

Further, the demodulation circuit samples the low-frequency converted color signal with a clock frequency four times the low-frequency conversion frequency from the first signal generation circuit, and outputs the signal from the Mu/D converter and the Mu/D converter. It is equipped with a digital demodulation circuit that digitally demodulates the digital data into two color difference signal data.
D after processing the Y component directly or with a digital filter
/A conversion, or digitally obtain the phase error from the R-Y component and B-Y semi-conversion of the demodulated low-frequency conversion color signal, create digital data corresponding to the phase error, and then perform D/A conversion.
the first after converting and passing it directly or through an analog filter.
If the configuration is configured to obtain a control signal for the oscillation frequency of the first signal generation circuit or the second signal generation circuit to be supplied to the signal switching circuit or the second signal switching circuit, various By providing digital filters and arithmetic circuits, it is possible to set constants for fiPLL pull-in, steady phase error, etc., which was impossible with conventional analog circuits, and improve characteristics. In addition, digitalization of circuits, such as replacing analog low-pass filters with digital 0-order hold,
This has the effect of facilitating integration and reduction of circuit components.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional color signal processing device. FIG. 2 is a block diagram of a color signal processing device according to one embodiment of the present invention, and FIG. 3 is a block diagram of a color signal processing device according to another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...First signal generation circuit, 2...Second signal generation circuit, 3...-...First phase comparison circuit, 5...... Signal creation circuit, 6... constant voltage circuit, 7... first signal switching circuit, 8...
...Second signal switching circuit, 1o...Frequency dividing circuit, 11.12...Frequency conversion circuit, 13゛・
...Low pass filter, 14...Band pass filter, 15...Signal input terminal, 16.
... Recording color signal output terminal, 17 ... Reproducing color signal output terminal, 18 ... Horizontal synchronization signal input terminal, 19 ... Second phase comparison circuit , 20...
...Third signal switching circuit, 21...M/D converter, 22...Digital demodulation circuit, 2324...
...Digital wedge filter, 25...
Encoder, 26...D/A converter, 2...
... Band pass filter, 28 ... Control voltage generation circuit, 29 ... Second signal generation circuit, 3
o...A frequency dividing circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure

Claims (4)

[Claims] (1) a first signal generation circuit that generates a signal with a frequency that is an integral multiple of the low-frequency conversion frequency; and a signal generation circuit that creates a low-frequency conversion carrier wave from the signal from the first signal generation circuit;
a second signal generating a signal having a frequency that is an integer multiple of the color subcarrier frequency;
a first phase comparison circuit that compares the phase of the frequency-divided signal from the first signal generation circuit and the horizontal synchronization signal; a second phase comparison circuit that compares the phases of the low-frequency conversion carrier waves; a constant voltage circuit that provides a fixed control signal with the frequency of the second signal generation circuit as a reference frequency; The first signal switching circuit switches the control input of the first signal generating circuit between the signal from the first phase comparator circuit and the second phase signal during recording and playback. The second signal switching circuit switches the control input of the second signal generation circuit between the signal from the second phase comparison circuit and the fixed control signal from the constant voltage circuit. , the third signal switching circuit inputs the burst of the low-frequency converted color signal input to the second phase comparator circuit into the burst of the low-frequency converted color signal that has been low-frequency converted to be recorded on the magnetic tape, and the magnetic tape. a color signal processing device configured to switch between a burst of a low-frequency converted color signal reproduced from the color signal; (2) The color signal processing device according to claim 1, wherein the second phase comparison circuit has a demodulation circuit and performs phase comparison based on values of burst sections of two demodulated color difference signals. (3) As a method of frequency conversion during reproduction, a method is used in which a low-pass converted color signal is demodulated into two color difference signals using a single-stage demodulation circuit, and then a quadrature two-phase balanced modulation wave is created at a predetermined carrier frequency. The color signal processing device according to claim 2, characterized in that the demodulation circuit of the second phase comparison circuit also serves as a demodulation circuit for demodulating the low frequency converted color signal into two color difference signals. . (4) The demodulation circuit includes an A/D converter that samples and A/D converts the low frequency conversion color signal using a clock that is four times the low frequency conversion frequency from the first signal generation circuit, and the A/D converter. Equipped with a digital demodulation circuit that digitally demodulates the output digital data into two color difference signal data, and performs D/A conversion on the R-Y components of the low-pass converted color signal demodulated into digital data either directly or after processing with a digital filter. Alternatively, the phase error is calculated digitally from the R-Y component and B-Y component of the demodulated low-frequency conversion color signal, and after creating digital data corresponding to the phase error, it is D/A converted and converted directly or analog. A patent characterized in that a control signal for the oscillation frequency of the first signal generation circuit or the second signal generation circuit is obtained after being passed through a filter and then supplied to the first signal switching circuit or the second signal switching circuit. A color signal processing device according to claim 2.