GB2118801A

GB2118801A - Color television signal conversion device

Info

Publication number: GB2118801A
Application number: GB08307621A
Authority: GB
Inventors: Tetsuo Kusakabe; Tetsuro Sakai; Kazuhiko Honda
Original assignee: Tokyo Shibaura Electric Co Ltd
Current assignee: Toshiba Corp
Priority date: 1982-03-19
Filing date: 1983-03-18
Publication date: 1983-11-02
Also published as: DE3309807C2; DE3309807A1; GB2118801B; GB8307621D0

Abstract

Color TV signal data picked up from an NTSC video disc 48 is separated by a separation filter 50 into a first chrominance signal (1.52 MHz) and a luminance signal. In this case, the rotational frequency of the video disc 48 is set such that a horizontal line frequency of the luminance signal is 15.625 kHz which is the line frequency of the PAL signal component. The first chrominance signal (1.52 MHz) is converted by a frequency converter 53 to a second chrominance signal (4.43 MHz). The second chrominance signal (4.43 MHz) is supplied to the first input terminal X1 of a switch 66 through a 45 DEG phase shifter 64 and directly to the second input terminal X2 of the same switch 66. The switch 66 selects the first input terminal X1 in response to a burst gate pulse, and selects the second input terminal X2 during any period other than the burst period. The third chrominance signal is supplied to an R-Y component processing circuit 81. A carrier signal having a frequency (8.86 MHz) twice that (4.43 MHz) of a subcarrier is supplied to the R-Y component processing circuit 81. The R-Y component processing circuit 81 performs an analog multiplication operation, thereby producing a PAL chrominance signal at its output terminal. In a further embodiment a system changeover circuit (78,79, Fig. 8) is provided so that either a PAL or NTSC recorded video disc may be played back. In addition a played back PAL signal may be converted to an NTSC signal. <IMAGE>

Description

SPECIFICATION Color television signal conversion device The present invention relates to a color TV signal conversion device used for converting an NTSC color TV signal to a PAL color TV signal in a video disc reproduction system or a video tape recorder.

The NTSC color television signal includes a luminance signal and a carrier chrominance signal.

The carrier chrominance signal has two color difference signal components R-Y and B-Y which modulate a color subcarrier in accordance with quadrature modulation. In the case of recording the color TV signal on a recording medium such as a video disc, the carrier chrominance signal is frequency-converted to a low frequency and is recorded on the recording medium. Therefore, when a pickup signal from the video disc is reproduced, the low-frequency carrier chrominance signal is demodulated to an original frequency carrier chrominance signal.

Fig. 1 shows a video disc reproduction system for reproducing the signals recorded by the NTSC system.

A color TV signal to be detected and reproduced from the video disc is separated into a lowfrequency carrier chrominance signal Ch, and a luminance signal (Y signal) which includes a synchronizing signal. The signal Ch and Y signal are supplied to input terminals 11 and 12, respectively.

The carrier frequency of the carrier chrominance signal Ch applied to the input terminal 11 is interleaved with that of the Y signal, for example, in the following manner: 195/2 .fH=1.534091 (MHz) where fH is the line frequency.

In order to reconvert the 1 .53-MHz chrominance signal (low-frequency converted chrominance signal) to the 3.58-MHz chrominance signal (original frequency carrier chrominance signal), the 1.53 MHz chrominance signal is supplied to a frequency converter 1 3. The frequency converter 13 multiplies the 1 .53-MHz chrominance signal and a carrier wave (CW) signal (5.11 MHz=1.53 MHz+3.58 MHz). The 5.11MHz carrier wave signal is produced by a VCO (voltage controlled oscillator) 14. The multiplied signal is supplied to a band-pass filter 1 5 having a 3.58 MHz band-pass characteristic. The NTSC 3.58-MHz chrominance signal is then obtained from the band-pass filter 1 5.

This 3.58-MHz chrominance signal is mixed by a mixer 1 6 with the Y signal applied to the input terminal 12. An NTSC color TV signal then appears at an output terminal 17.

A video disc player is subject to a time base error of signal components which is caused by wow and flutter of a turntable or the like. Such a time base error causes significant jitter in the 1 .53-MHz chrominance signal. A video disc player generally has an automatic phase control (APC) loop in order to eliminate such a problem. More specifically, the chrominance signal reconverted to a frequency of 3.58 MHz is supplied to a phase comparator 18 which compares the phase of this input signal with that of a reference signal having a frequency of 3.58 MHz during each burst period.The 3.58-MHz reference signal is produced by a 3.58-MHz oscillator 1 9. A burst gate pulse is obtained from a burst gate pulse generator 21, which receives an output signal from a sync separator 20 which separates a horizontal synchronizing signal from the Y signal supplied to the input terminal 12, and which then supplies an output signal to the phase comparator 18. An output signal from the phase comparator 1 8 is held for a 1-H period by a sample and hold circuit 22, and is supplied to an oscillation frequency control end of the VCO 14 through a low-pass filter 23.

A PAL color TV system has, in addition to the luminance signal, two chrominance signal components (color difference signals) according to which the subcarrier is quadrature-modulated. One (R-Y signal) of the two chrominance signal components is inverted for each successive line. A carrier frequency fsc of the PAL system is generally selected to be 4.43 MHz.

Fig. 2 shows an example of a demodulation circuit for demodulating such a PAL color TV signal.

Referring to Fig. 2, a PAL composite signal is supplied to an input terminal 25 and is then supplied to a C-Y separator 26 which produces a Y signal onto a line 27 and a carrier chrominance signal onto a line 28. The carrier chrominance signal is subjected to addition by an adder 30 and subtraction by a subtractor 31 of a delayed carrier chrominance signal from a 1-H delay line 29. A B-Y signal appears at the output end of the adder 30, while an R-Y signal appears at the output end of the subtractor 31.

These B-Y and R-Y signals are respectively supplied to B-Y and R-Y demodulators 32 and 33.

The line 28 is also connected to a local subcarrier oscillator 35 through a burst phase discriminator 34.

A reference subcarrier signal of 4.43 MHz is supplied to the B-Y demodulator 32 through a 900 phase shifter 36 and is also supplied to the R-Y demodulator 33 through a line changeover switch 37.

Since the R-Y signal changes its polarity for each successive line, the reference subcarrier signal to be supplied to the R-Y demodulator 33 must be inverted by 1800 for each successive line. Thus, the line changeover switch 37 has a 1800 phase shifter 371 and a changeover switch 372. The changeover switch 372 is switched between a 1800 phase shift line 381 and a direct coupling line 382 for each line.

In order to control the switching operation of the switch 372, a sync signal is separated from the PAL composite signal at the input terminal 25 through a sync separator 39. The sync signal is then supplied to a flip-flop 40 which produces a signal which is used as a line changeover signal.

The signals sync-detected by the B-Y and R-Y demodulators 32 and 33 are supplied to a matrix circuit 41 which produces blue, green and red signals B, G and R, respectively.

When the signal recorded by the NTSC system on the video disc is reproduced by an NTSC reproduction system, the reproduced color TV signal is of the NTSC system. Therefore, even if the NTSC reproduced color TV signal is supplied to a color TV receiver of the PAL system, color reproduction image cannot be obtained.

When the NTSC reproduced color TV signal is supplied to a PAL color TV receiver, a marginally satisfactory reproduced image can be obtained wherein the luminance signal seems unnaturally bright because of different standards. However, as far as the chrominance signal is concerned, since different signal processing systems are adopted in the NTSC and PAL systems, a good reproduced color image cannot be obtained.

In European countries where the PAL system is adopted, the need arises to reproduce the NTSC color TV signal with a PAL color TV receiver. In order to respond to such a demand, in the present satellite relay system, the NTSC color TV signal is completely demodulated by the NTSC system and the demodulated signal is then converted to a PAL color TV signal.

However, it is impossible in practice to apply the techniques used in the satellite relay system to a video disc player whose circuit scale, cost and size are limited.

It is an object of the present invention to provide a simple color TV signal conversion device which converts a pickup signal recorded by the NTSC or PAL system on a video disc to a color TV signal of the opposite (PAL or NTSC) system.

It is another object of the present invention to provide a color TV signal conversion device wherein an output color TV signal from a video disc player for reproducing an NTSC or PAL signal from a video disc can be demodulated by a PAL or NTSC color TV receiver, thereby obtaining a reproduced color image.

In order to achieve the above objects of the present invention, there is provided a color TV signal conversion device, characterized by comprising: base signal generating means for generating color TV signal data which includes a luminance signal and a first chrominance signal frequency-converted to a low frequency; separating filter means for receiving the color TV signal data and for separating the color TV signal data into the first chrominance signal and the luminance signal; first carrier signal generating means; frequency converting means for converting the first chrominance signal to a second chrominance signal, said signal converting means having one input terminal which receives the first chrominance signal from said separating filter means and the other input terminal which receives a first carrier signal from said first carrier signal generating means; first band-pass filter means for receiving an output from said frequency converting means and for producing the second chrominance signal at an output terminal thereof; first switching means for shifting by a predetermined phase of a burst signal included in the second chrominance signal from said first band-pass filter means in every other horizontal period and for producing a third chrominance signal including a phase-shifted burst signal at an output terminal thereof, said first switching means having a first input end which receives the second chrominance signal from said first band-pass filter means through a predetermined-degree phase shifter and a second input terminal which receives the second chrominance signal directly from said first band-pass filter means; first switch controlling means for alternately selecting said first and second input terminals of said first switching means in each successive burst signal period, and for controlling to select said second input terminal during a period except for the burst signal period such that a horizontal sync signal separated from the luminance signal is delayed and shaped to obtain a burst gate pulse which is applied to a control terminal of said first switching means; second carrier signal generating means for generating a second carrier signal having a frequency twice a frequency of the first carrier signal from said first carrier signal generating means; and an R-Y component processing circuit for alternately producing the third chrominance signal and a multiplied signal obtained by multiplying the third chrominance signal and the second carrier signal in an analog manner for every other horizontal line, said R-Y component processing circuit having one input terminal which receives the third chrominance signal from said first switching means and the other input terminal which receives the second carrier signal from said second carrier signal generating means.

This invention can be more fully understood from the following detailed description when taken in conjunction with the accompanying drawings, in which: Fig. 1 is a block diagram of a conventional NTSC color TV signal conversion system; Fig. 2 is a block diagram of a conventional PAL color TV signal conversion system; Fig. 3 is a block diagram of a color TV signal conversion device according to an embodiment of the present invention; Fig. 4 is a block diagram of a color TV signal conversion device according to another embodiment of the present invention; Figs. 5(a) and 5(b) are vector diagrams of a PAL color TV signal, and Fig. 5(c) is a vector diagram of an NTSC color TV signal; Figs. 6(a) to 6(f) are timing charts for explaining the mode of operation of the device shown in Fig.

4; Fig. 7 is a circuit diagram showing part of the device shown in Fig. 4; Fig. 8 is a block diagram of a color TV signal conversion device according to still another embodiment of the present invention; Figs. 9(a) and 9(b) are vector diagrams for explaining the mode of operation of the device shown in Fig. 8; Figs. 10 and 11 are block diagrams showing other embodiments of part of the device shown in Fig. 8, respectively; Fig. 12 is a block diagram of a color TV signal conversion device according to still another embodiment of the present invention; Figs. 13(a) to 13(e) are timing charts for explaining the mode of operation of the device shown in Fig. 12; Fig. 14 is a circuit diagram showing part of the device shown in Fig. 12; and Fig. 1 5 is a block diagram showing part of a color TV signal conversion device according to still another embodiment of the present invention.

The signal components of an NTSC color TV signal, the signal components of the signal recorded by the NTSC system on a video disc, and the signal components of a PAL color TV signal are described hereinafter.

A line frequency fH of the NTSC color TV signal is 1 5.734 kHz. The number of scanning lines is 525. A field frequency fv is 59.93 Hz. A horizontal period (1 H) is 63.36 Used.

A subcarrier frequency fD of the low-frequency converted chrominance signal is 1.53409 MHz (1/2 xfH x 195).

On the other hand, a line frequency fH of the PAL color TV signal is 1 5.625 kHz. A field frequency fv is 50 Hz. The number of scanning lines is 625. A horizontal period (1 H) is 64 ysec.

In order to convert the NTSC horizontal period (63.56 used) to the PAL horizontal period (64 ,ssec), the rotational frequency of the video disc in accordance with the NTSC system must be multiplied by 0.9931 (63.56/64) times the normal frequency. In other words, in order to display the NTSC signal reproduced from the video disc on a screen of a PAL color TV receiver, the rotational frequency of the turntable of the video disc player must be decreased to 0.9931 times the normal frequency. Therefore, the line frequency fH (=15.734kHz) of the NTSC color TV signal can be converted to the line frequency fH (=1 5.625 kHz) of the PAL color TV signal.This can be achieved by changing an oscillation frequency of the reference oscillator in a circuit for controlling the rotation frequency of the turntable motor in the video disc player. As a result, any frequency (line frequency, chrominance signal frequency) other than the field frequency fv can be converted between the NTSC and PAL systems.

The frequencies of the signals of the NTSC video disc and the frequencies of the signals converted by the 0.9931 muitiplication so as to correspond to those in the PAL system are shown in Table 1 below.

Table 1

NTSC PAL Line frequency fH 1 5.734 kHz 1 5.625 kHz Scanning lines 525 525 Field frequency fV (=2/525 fH) 59.93 Hz 59.52 Hz Subcarrier frequency fD (low-frequency conversion) 1.53409 MHz 1.52343 MHz The above description is made assuming that the rotational frequency of the disc as a signal generating means is decreased to 0.9931 times the normal frequency.

The difference between the chrominance signals of the PAL and NTSC systems will be briefly described with reference to Fig. 5. The PAL and NTSC systems are the same in that the two color difference signals B-Y and R-Y are simultaneously transmitted. However, in the PAL system, the phase of the R-Y signal in every successive line is inverted. The R-Y and B-Y signals then modulate the subcarrier in accordance with quadrature modulation. Therefore, according to the vector diagram of the PAL signal, the R-Y signal of the PAL system has a phase in a given line as shown in Fig. 5(a), and it has an inverted phase in the next line as shown in Fig. 5(b). A burst signal BU of the PAL system is shifted by 450 with respect to the B-Y axis.

However, in the NTSC system, the BY and R-Y signals quadrature-modulate the subcarrier, as shown in Fig. 5(c). The signals can be expressed by vectors which have the same sign. In this case, a burst signal is shifted by 1 800 with respect to the BY signal.

In order for a PAL receiver to demodulate the signal recorded by an NTSC system on the video disc, the following conditions must be satisfied: (1) A low-frequency converted chrominance signal (1.52 MHz) must be converted to a 4.43-MHz PAL chrominance signal.

(2) The phase of the R-Y signal must be inverted for each successive line.

(3) The phase of the burst signal must be shifted by 450 for every other line.

The device shown in Fig. 3 achieves the above signal conversion.

Referring to Fig. 3, a motor drive circuit 45 controls and drives a turntable motor 46. A signal picked up from a video disc 48 on a turntable 47 is supplied to a separation filter 50 through a signal processing circuit 49. The separation filter 50 separates the TV signal into a first chrominance signal Ch and a luminance signal (Y signal). The chrominance signal Ch and the Y signal are applied to input terminals 51 and 52, respectively.

The carrier frequency of the first chrominance signal Ch applied to the input terminal 51 is 1.52 MHz. This 1 .52-MHz chrominance signal Ch is supplied to a frequency converter 53 which then converts the signal Ch to a 4.43-MHz signal. The frequency converter 53 also receives a first carrier wave (CW) signal (5.95 (MHz)=1.52+4.43) from a voltage controlled oscillator (VCO) 54. The frequency converter 53 multiplies the first chrominance signal (1.52 MHz) and the 5.95-MHz CW signal from a first carrier signal generating means (VCO 54), and produces a second chrominance signal (4.43 MHz). The output from the frequency converter 53 is supplied to a subtractor 56 through a 1 H delay line 55.This 1 H-delayed signal is subtracted from the signal supplied directly from the frequency converter 53, thereby completely eliminating the luminance component. The output from the subtractor 56 is supplied to a 4.43-MHz band-pass filter 57. The video disc play is subject to a time base error of signal components which is caused by wow and flutter of a turntable or the like. Such a time base error causes significant jitter in the 1.53 MHz carrier wave. The video disc player generally has an automatic phase control (APC) loop in order to eliminate such a problem. The output from the band-pass filter 57 is supplied to a phase comparator 58 and is compared by the phase comparator 58 with a 4.43-MHz CW signal during the burst period.It is noted that the 4.43-MHz CW signal is supplied from a 4.43-MHz oscillator 59. A burst gate pulse is obtained from a burst gate pulse generator 61, which receives an output signal from a sync separator 60 which separates a sync signal from the Y signal supplied to the input terminal 52, and which then supplies an output signal to the phase comparator 58. An output signal from the phase comparator 58 is held for a 1 H period by a sample and hold circuit 62, and is supplied to a low-pass filter 63. An output signal from the low-pass filter 63 is supplied to a control terminal of the VCO 54, thereby controlling the oscillation frequency of the VCO 54.

The output signal from the band-pass filter 57 is supplied to a phase shifting means for shifting the phase of the burst signal. More specifically, the output signal from the band-pass filter 57 is supplied to a switch 66 through a 450 phase shifter 64 and a direct coupling line 65. The switch 66 has a stationary contact X1 connected to the 450 phase shifter 64, a stationary contact X2 connected to the direct coupling line 65, and a movable contact X3 connected to an output line 67. The contact X3 is selectively connected to the contacts X1 and X2. This switching operation is performed in accordance with an output from the burst gate pulse generator 61.The switch 66 450-shifts a burst signal BU in Fig. 5(c). An output (i.e., the third chrominance signal) from the switch 66 is supplied to an R-Y component processing circuit 81 through the output line 67.

The output from the 4.43-MHz oscillator 59 is supplied to a doubler 69. The output (i.e., an 8.86 MHz CW signal) from the doubler 69 is supplied to the R-Y component processing circuit 81.

In the R-Y component processing circuit 81, the 8.86-MHz CW signal, the third chrominance signal from the switch 66, and the DC bias signal are modulated by a modulating means so as to convert the phases of the R-Y components symmetrically about the B-Y axis. This conversion is performed every 1 H. Therefore, the output from an oscillator 73 provided comprising a flip-flop is supplied as a timing pulse to the R-Y component processing circuit 81. The oscillator 73 is connected to the output terminal of the sync separator 60. A control signal (timing pulse) which has a frequency half of the line frequency fH appears at the output terminal of the sync separator 60.

The fourth chrominance signal from the R-Y component processing circuit 81 corresponds to a signal obtained by inverting the R-Y component phase among the components of the NTSC chrominance signal every 1 H. The fourth chrominance signal is supplied to a mixer 75. The Y signal is supplied to the input terminal 52 of the mixer 75 through a line 76. As a result, a color TV signal to be reproduced by the general PAL receiver appears at an output terminal 77 of the mixer 75.

Fig. 4 is a block diagram showing the R-Y component processing circuit 81. The same reference numerals as used in Fig. 3 denote the same parts in Fig. 4, and a detailed description thereof will be omitted. The R-Y component processing circuit 81 shown in Fig. 4 comprises a modulator 68, a 4.43-MHz band-pass filter 74, and a line changeover switch 70. The line changeover switch 20 has a stationary contact Z1 connected to the doubler 69, a stationary contact Z2 connected to a bias source 71, and a movable contact Z3 connected to an output line 72. The contact Z3 is selectively connected to the contacts Z1 and Z2 of the switch 70. The switching operation is performed for each successive line.A signal (i) for controlling the above switching operation is supplied from an oscillator 73 connected to the sync separator 60. The control signal (i3 is synchronous with the horizontal sync signal and has a frequency half of the line frequency fH.

The oscillator 73 may comprise a flip-flop which is driven by the horizontal sync signal. An output signal from the line changeover switch 70 is supplied to the modulator 68 through the line 72. The modulator 68 inverts the phase of the R-Y component of the NTSC chrominance signal components for every other line.

An output signal from the modulator 68 is supplied to a O-Y mixer 75 through a band-pass filter 74 of 4.43-MHz. The mixer 75 also receives, through a line 76, the Y signal applied to the input terminal 52. The color TV signal from an output terminal 77 of the mixer 75 can be reproduced by a general PAL receiver.

The mode of operation of the signal switching circuit of the present invention will be described with reference to Fig. 6. Figs. 6(a) to 6(f) show waveforms of the signals appearing in the circuit shown in Fig. 4. The signals in Figs. 6(a) to 6(f) correspond to the signals 03 to (i) shown in Fig. 4.

Fig. 6(a) shows a chrominance signal as the output from the band-pass filter 57; Fig. 6(b) shows a horizontal sync signal as the output from the sync separator 60; Fig. 6(c) shows a burst gate pulse as the output from the burst gate pulse generator 61; Fig. 6(d) shows a line changeover signal as the output signal from the oscillator 73; Fig. 6(e) shows the 8.86-MHz CW signal as the output from the doubler 69; and Fig. 6(f) shows the signal as the output signal from the line changeover switch 70.

Both the PAL signal shown in Figs. 5(a) and 5(b) and the NTSC signal shown in Fig. 5(c) comprise two-color difference signals which quadrature-modulate the subcarrier signal, as previously described.

The NTSC chrominance signal is given by equation (1) below: EN=(ER--EY)cos(osct) +(EB--EY)sin(wsct) (1) where ose is the angular frequency of the subcarrier.

The PAL chrominance signals given below in equations (2) and (3) appear on each successive line: EP=(ER-EY)cos(a;sct)+(EB-EY)sin(a;sct) (2) EP=-(ER-EY)cos(wsct) +(EB--EY)sin(wsct) (3) Equation (2) is the same as equation (1). In order to convert the NTSC signal to the PAL signal components, the original signal in equation (1) is switched for every other line so as to coincide with the signal component shown in equation (3).

The burst signal of the PAL signal is shifted by 450 with respect to the B-Y axis shown in Fig.

5(a) or 5(b). Only the burst signal is extracted from the NTSC signal and is shifted by 450 and delayed before the NTSC signal is converted to the PAL signal.

The mode of operation of the color TV signal conversion device will now be described based on the above. The frequency of the chrominance signal Ch reproduced from the disc and supplied to the input terminal 51 is 1.52 MHz (1.53 x0.993 1) since the rotational frequency of the disc is decreased to 0.9931 times the normal frequency. The 1 .52-MHz chrominance signal is multiplied by the frequency converter 53 with the 5.95-MHz CW signal from the VCO 54. The frequency converter 53 thus produces a second chrominance signal (4.43 MHz).Since the second chrominance signal is frequencyinterleaved with the horizontal sync signal (1/4 fH), the second chrominance signal is subtracted by the subtractor 56 from a chrominance signal which is obtained by 1 H delaying the second chrominance signal by means of the 1 H delay line 55, thereby completely eliminating the luminance signal component. As a result, only the chrominance signal is extracted. The output signal from the subtractor 56 is obtained as a 4.43-MHz chrominance signal through the 4.43-MHz band-pass filter 57 (Fig. 6(a)).

The phase comparator 58, the sample and hold circuit 62, and the low-pass filter 63 constitute an APC loop. The time base error of signal components which is caused by wow and flutter of the turntable or the like and which causes a significant jitter is eliminated so as to obtain a highly stable chrominance signal.

The 4.43-MHz chrominance signal from the band-pass filter 57 is supplied to the switch 66 through the 450 phase shifter 64 so as to shift the phase of the burst signal, and through the direct cpupling line 65. The switch 66 is switched by the burst gate pulse (Fig. 6(c)) such that the contact X1 is connected to the contact X3 only during the burst period, and the contact X2 is connected to the contact X3 during any period except for the burst period. The switch 66 only shifts and delays the phase of the burst signal by 450, thereby obtaining the third chrominance signal shown in Fig. 5(a).

Meanwhile, the output signal from the 4.43-MHz oscillator 59 is supplied to the doubler 69 which then produces the second carrier wave (CW) signal (8.86 MHz) (Fig. 6(e)). This second OW signal is supplied to the line changeover switch 70 and is switched for each successive line in accordance with the output (Fig. 6(d)) from the oscillator 73. In a given line, the contacts Z1 and Z3 of the switch 70 are connected to each other; but in the next line, the contacts Z2 and Z3 thereof are connected to each other. Therefore, the switch 70 produces a signal having the second CW signal component and the DC voltage component which alternately appear for every other line (Fig. 6(f)).

The modulator 69 multiplies the output signal (chrominance signal in which the phase of the burst signal is delayed by 450) from the switch 66 and the output (signal which alternately has the 8.86-MHz signal component and the DC signal component) from the line changeover switch 70.

The above operation is expressed by equations (4) and (5) below.

The chrominance signal is multiplied by the 8.86-MHz CW signal, so that the signal component is given as follows: EP'=I(ER--EY) cos(wsct)+( EB--EY)sin(wsct)j x (--cos(2#sct) =(1 /2) (ER--EY)Icos(3wsct)+ cos(-msct) |(1 /2) )--(1/2) (EB-EY)}sin(3wsct)+sin(-wsct) 1 =(1/2) [-(ER-EY) {cos(3#sct)+cos(cos(#sct)} +(EB-EY){-sin(3cosct) +sin(cosct) Ii (4) The chromimance signal is also multiplied by the DC component, so that the signal component is given as follows:: EP'='j(ER-EY)cos(wsct)+(EB-EY)sin(cosct) lxi x 1 =(EREY)cos(sct) + (EB-EY)sin(wsct) (5) The level adjustment is then performed by the modulator 68, and the output signal from the modulator 68 is supplied to the band-pass filter 74. Therefore, the (3wsc) component in equation (4) is eliminated, and the output signal from the band-pass filter 74 is given as follows: EP'=-( ER-EY)cos(wsct) +(EBEY)sin(wsct) (6) According to the output from the band-pass filter 74, the signals given in equations (5) and (6) are obtained for each successive line. As a result, the chrominance signal components of the PAL system can be obtained.

The output signal from the band-pass filter 74 is mixed by the mixer 75 with the Y signal applied to the input terminal 52, thereby producing the PAL color TV signal at the output terminal 77. In this manner, the NTSC signal can be converted to the PAL signal.

Fig. 7 is a circuit diagram showing the main part of the device shown in Fig. 4. The main part comprises the 450 phase shifter 64, the modulator 68, the doubler 69 and the band-pass filter 74.

Referring to Fig. 7, the phase shifter 64 comprises a transistor Q1 and a low-pass filter of a resistor R1 and a capacitor 01. The base. of the transistor Q1 is connected to the low-pass filter, the collector thereof is connected to a power source (not shown) and the emitter thereof is grounded through a resistor R2. The emitter of the transistor Q1 is also connected to the contact X1 of the switch 66. The burst signal is shifted by 450 and delayed by the low-pass filter which comprises the resistor R1 and the capacitor C1.The gain is attenuated by about 3 dB, so that the original signal is applied to the base of a transistor Q2 through an attenuator of resistors R3 and R4 so that the gain of the original signal will coincide with the gain of the signal from the low-pass filter. The emitter of the transistor Q2 is connected to the contact X2 of the switch 66.

The collector of the transistor Q2 is connected to a voltage line (not shown), and the emitter thereof is grounded through a resistor R5. The resistor R4 is grounded through a DC voltage cutoff capacitor C2.

The doubler 69 comprises a double balanced modulator. This modulator comprises transistors 03 and Q4 which constitute a first differential amplifier, transistors Q5 and Q6 which constitute a second differential amplifier, transistors Q7 and Q8 which respectively supply constant currents to the first and second differential amplifiers, and a transistor Q9 which supplies a constant current to the transistors Q7 and Q8.

The emitters of the transistors Q7 and Q8 are commonly connected to the collector of the transistor Q9 respectively through resistors R7 and R8, respectively. The emitter of the transistor Q9 is grounded through a resistor R9. The collectors of the transistors Q3 and Q5 are connected to each other and their common node is connected to a voltage supply line Vcc. The collectors of the transistors Q4 and Q6 are connected to each other, and a tank circuit as a load which comprises an inductor L1, a resistor R6 and a capacitor C3 is connected between the common node of the collectors of the transistors Q4 and Q6 and the voltage supply line Vcc. A plurality of bias voltage sources V1, V2, V3 and V4 are arranged between the voltage supply line Vcc and ground. A voltage from the bias voltage source V1 is applied to the base of the transistor Q9 and to the bases of the transistors Q7 and Q8 through resistors R10 and R1 1, respectively. A voltage from the bias voltage source V2 is applied to the bases of the transistors Q3 and Q6 through a resistor 1 2. A voltage from the bias voltage source V3 is supplied to the bases of the transistors Q4 and Q5 through a resistor R 3. The bases of the transistors 03 and Q6 are commonly grounded through a capacitor C4.

The 4.43-MHz CW signal from the oscillator 59 is supplied to the bases of the transistors Q4 and Q5 through a capacitor C5 and to the base of the transistor Q7 through a capacitor C6. The 8.86-MHz doubled CW signal is produced from the collectors of the transistors Q4 and Q6. It is noted that the phase of the 8.86-MHz CW signal can be properly adjusted by adopting a variable inductor as the inductor L1 . The 8.86-MHz CW signal is supplied to the contact Z1 of the line changeover switch 70 through a capacitor C7, a transistor Q10 and a capacitor C8.The base of the transistor Q10 is connected to a bias voltage source V5 through a resistor R1 4, the collector thereof is connected to the voltage supply line Vcc, and the emitter thereof is grounded through a resistor R1 5. A capacitor C9 and a resistor RI 6 which are connected to the contact Z2 of the line changeover switch 70 constitute a bias voltage source 71.

The modulator 68 comprises a double balanced modulator. This modulator comprises transistors Q11 and 012 which constitute a first differential amplifier, transistors Q13 and 014 which constitute a second differential amplifier, transistors Q15 and Q16 for supplying constant currents to the first and second differential amplifiers, and a transistor Q17 for supplying a constant current to the transistors Q15 and Q16.

The emitters of the transistors 01 5 and Q1 6 are commonly connected to the collector of the transistor Q17 through resistor R17 and R18, respectively. The emitter of the transistor Q17 is grounded through a resistor R1 9. The collectors of the transistors 011 and 013 are connected to each other, and a common node thereof is connected to the voltage supply line Vcc. The collectors of the transistors Q12 and 014 are connected to each other, and a band-pass filter of an inductor L2, a resistor R20 and a capacitor C10 is connected as a load between the collectors of the transistors Q12 and Q14 and the voltage supply line Vcc. A plurality of bias voltage sources V6, V7 and V8 are arranged between the voltage supply line Vcc and ground.A voltage from the bias voltage source V6 is supplied to the base of the transistor Q1 7 and to the bases of the transistors Q1 5 and Q1 6 through resistors R21 and R22, respectively. A voltage from the bias voltage source V7 is supplied to the bases of the transistors 011 and Q14 through a resistor R23 and to the bases of the transistors Q12 and 013 through a resistor R24.

The chrominance signal (Fig. 6(a)) as the output from the switch 66 is supplied to the base of the transistor 015 through a capacitor 011. The output (Fig. 6(f)) from the line changeover switch 70 is supplied to the bases of the transistors Q11 and Q14. Therefore, the signal which includes the chrominance signal components given by equations (5) and (6) is produced alternately for each 1 H from the collectors of the transistors 012 and 014.This signal is then supplied to the C--Y mixer 75 through a capacitor C12, a transistor 018, and a capacitor 013. The base of the transistor 018 is connected to a bias voltage source V9 through a resistor R25, the collector thereof is connected to the voltage supply line Vcc, and the emitter thereof is grounded through a resistor R26.

The capacitor C10, the resistor R20 and the inductor L2 which are connected to the collectors of the transistors Q12 and 01 4 constitute the 4.43-MHz band-pass filter 74.

Fig. 8 shows a colorTVsignal conversion device according to another embodiment of the present invention. In the first embodiment, a signal recorded by the NTSC system on the video disc is converted to PAL signal components which are then reproduced. However, a case may occur wherein a signal recorded by the PAL system on the video disc needs to be reproduced. In this case, the conversion of the signal to the PAL signal is not required. More specifically, the signal need not be switched by the switch 66 after the burst signal thereof is phase-shifed by 450 and delayed by the 450 phase shifter 64. The 4.43-MHz chrominance signal need not be multiplied by the modulator 68 with the CW signal.

In particular, the switch 66 and the line changeover switch 70 must be stopped by a proper means.

The device shown in Fig. 8 includes such a means. A first changeover switch 78 is arranged between a switch 66 and a burst gate pulse generator 61. A second changeover switch 79 is arranged between a line changeover switch 70 and a 1/2 fH oscillator 73. The first and second changeover switches 78 and 79 are controlled by a system changeover circuit 80.

The first changeover switch 78 has a first contact a1 connected to the burst gate pulse generator 61, a second contact a2 connected to a DC voltage supplying terminal 81 at which a DC signal of logic level "1" appears, and a third contact a3 connected to the line for controlling the switch 66. Similarly, the second changeover switch 79 has a first contact bl connected to the oscillator 73, a second contact b2 which is grounded, and a third contact b3 connected to the line for controlling the line changeover switch 70. The system changeover circuit 80 controls the rotational frequency of the turntable and produces a control signal to switch the first and second changeover switches 78 and 79.

In order to reproduce the signal recorded by the NTSC system, the first and third contacts a 1 and a3 of the first changeover switch 78 are connected to each other, and the first and third contacts b1 and b3 of the second changeover switch 79 are connected to each other. Furthermore, the rotational frequency of the turntable (or disc) is multiplied by 0.9931. Therefore, the arrangement of the device shown in Fig. 8 is substantially the same as that of the device shown in Fig. 4. However, in order to reproduce a signal recorded by the PAL system, the first and second contacts a 1 and a2 of the first changeover switch 78 are connected to each other. Since the DC voltage of logic level "1" is applied to the second contact a2 of the first changeover switch 78, the contacts X1 and X3 of the switch 66 are always connected to each other.in this case, the vectors of the signal supplied to the 45 phase shifter 64 is shown in Fig. 9(a). Since the phase of the burst signal has a constant relationship with that of the CW signal from the 4.43-MHz oscillator 59 by means of the APC loop, the output from a band-pass filter 57 is kept such that the R-Y and BY axes advance by 450 with respect to the CW signal, as shown in Fig. 9(a). Therefore, the chrominance signal which includes the burst signal is delayed by 450 by the connection between the contacts X1 and X3 of the switch 66, as shown in Fig. 9(b). The solid line in Figs. 9(a) and 9(b) indicates vectors of the signal components on a given line, whereas the dotted line indicates those on the next line. The 4.43-MHz CW signal is the reference signal in the vector diagram in Fig. 9(a) wherein the R-T and B-Y components are delayed by the 450 phase shifter 64. However, if it is desired that the output from the band-pass filter 57 be as shown in Figs.

5(a) and 5(b), the contacts X2 and X3 of the switch 66 may be constantly connected.

In this case, the first and second contacts bl and b2 of the second changeover switch 79 are connected to each other, and a control signal is not supplied to the line changeover switch 70. Since the contacts Z2 and Z3 of the line changeover switch 70 are connected to each other, the 8.86-MHz CW signal is not supplied to the modulator 68.

In this manner, even if the signal is recorded by the PAL or NTSC system on the video disc, the recorded signal can be readily reproduced.

The first changeover switch 78 and the switch 66 are not limited to the arrangements shown in Fig. 8. For example, arrangements shown in Figs. 10 and 11 may be adopted. Referring to Fig. 10, when the NTSC video disc played back, the switch 66 is switched for every 1 H, and contacts a2 and a3 of a line changeover switch 78A are connected to each other. However, when the PAL video disc is played back, the contact a1 and a contact a3 of the switch 78A are connected irrespective of the operation of the switch 66. Referring to Fig.11, when the NTSC video disc is played back, the contacts a2 and a3 of the switch 78A are connected and the switch 66 is switched for every 1 H.

However, when the PAL video disc is played back, the contacts a 1 and a3 of the switch 78A are connected to each other, and the switch 66 is switched for every 1 H. Even if the switch 66 is switched for every 1 H, it is constantly connected to the 450 phase shifter 64.

According to another embodiment of the present invention, the doubler 69 shown in Figs. 4 and 8 may be replaced by an 8.86-MHz oscillator, and the 4.43-MHz oscillator 59 may be replaced by a 1/2 frequency divider.

Various changes and modifications may be made within the spirit and scope of the present invention without departing from the spirit and scope of the appended claims.

When the color TV signal conversion circuit of the present invention is employed in a video disc player, an NTSC recorded signal can be readily reproduced by a PAL receiver.

Unlike a conventional system wherein the NTSC color TV signal is completely demodulated and this demodulated signal is then converted to PAL signal components, only a simple circuit is required.

Either a PAL recorded video disc or an NTSC recorded video disc can be readily played back in accordance with control of the system changeover circuit. The signal conversion function is stopped or started as needed.

Fig. 1 2 shows still another embodiment of the present invention. The same reference numerals as used in Figs. 3 and 4 denote the same parts in Fig. 12, and a detailed description thereof will be omitted.

Referring to Fig. 12, an R-Y component processing circuit 81 comprises an adder 82, a modulator 68, a 4.43-MHz band-pass filter 74, a switch 84 and an adder 85.

An output from a switch 66 is supplied to the modulator 68 and the adder 85 through an output line 67. Meanwhile, the output from a 4.43-MHz oscillator 59 is supplied to a doubler 69. The doubler 69 produces an 8.86-MHz continuous signal (CW signal) which is then supplied to the adder 82. A bias voltage source 83 is connected to the adder 82 so as to give a DC component in the doubler output. An output from the adder 82 is supplied to one input terminal of the modulator 68.

An output from the modulator 68 is supplied to the line changeover switch 84 through the bandpass filter 74 for extracting the 4.43-MHz component. An output from the line changeover switch 84 is supplied to the adder 85. The line changeover switch 84 connects or disconnects the band-pass filter 74 with the adder 85. The control signal (frequency of 1/2 fH) from an oscillator 73 is used as a switching control signal. The adder 85 adds the third chrominance signal from the switch 66 which is supplied every 1 H and the carrier signal, which is supplied from the switch 84. The adder 85 produces a PAL converted chrominance signal. This chrominance signal is mixed by a mixer 75 with the luminance signal. The PAL color TV signal appears at an output terminal 77. This TV signal can be reproduced by the PAL color TV receiver.

The mode of operation of the device shown in Fig. 12 will be described with reference to Fig. 1 3.

Figs. 13(a) to 13(e) show waveforms of the signals appearing at main parts of the device shown in Fig.

12. Figs. 13(a) to 13(e) correspond to signals indicated by reference symbols (i) to (i) in Fig.12, respectively. Fig. (a) shows the chrominance signal as the output from a band-pass filter 57: Fig.

1 3(b) shows the horizontal sync signal as the output from a sync separator 60; Fig. 13(c) shows the burst gate pulse as the output from a burst gate pulse generator 61; Fig. 13(d) shows the line changeover signal as the output from the 1/2 fH oscillator 73; and Fig. 13(e) shows the 8.86-MHz CW signal as the output from the doubler 69.

The NTSC chrominance signal is given by equation (1) as follows: EN=(ER-EY)cos(cosct)+(EB-EY)sin(sct) (1) where sc is the angular frequency of the subcarrier. The PAL chrominance signal can be given by equation (2) or (3) in accordance for each successive horizontal line: EP=(ER-EY)cos(cosct)+(EB-EY)sin(#sct) (2) EP=--(ER--EY)cos(wsct)+(EB--EY)sin(osct) (3) Equation (2) is identical to as equation (1). In order to convert the NTSC signal to the PAL signal components, the original signal in equation (1) is switched for every other line so as to coincide with the signal component shown in equation (3).

The burst signal BU in the PAL signal is shifted by 450 with respect to the BY axis as shown in Fig. 5(a) or 5(b). Only the burst signal is extracted from the NTSC signal and is delayed by 450 before the NTSC signal is converted to the PAL signal.

The mode of operation of the above embodiment will be described. The device shown in Fig. 12 operates in substantially the same manner as the devices respectively shown in Figs. 4 and 7, except that the R-Y component processing circuit 81 shown in Fig. 12 operates differently from the circuits respectively shown in Figs. 4 and 7.

In the embodiment shown in Fig. 12, only the operation of the R-Y component processing circuit 81 will be described.

The 4.43-MHz CW signal is supplied from the doubler 69 to the adder 82 and is then added to the DC voltage from the bias voltage source 83. The 8.86-MHz CW signal from the adder 82 includes the predetermined DC component and is supplied to the modulator 68. The 8.86-MHz CW signal with the DC component is multiplied by the modulator 68 with the output (third chrominance signal) from the switch 66.The chrominance signal at the output terminal of the switch 66 is the same as the NTSC signal EN given by equation (1), and an output e1 from the adder 82 is given as follows: ei=i/2+cos(2sct) (7) where a;sc is the angular frequency of the subcarrier (fSC=4.43 MHz).When the multiplication is performed by the modulator 68, an output e2 from the modulator 68 is given as follows: e2={(ER-EY)cos(#sct)+(EB-EY)sin(sct) Ix 1(1 /2)+cos(2cosct) I =( 1/2)}(ER-EY)cos(#sct)+(EB-EY)sin(#sct) I +(1/2)I (ER-EY)cos(osct)-(EB-EY)sin(osct) +(ER--EY)cos(3wsct) +(ES-EY)sin(3wsct) I (8) The output from the modulator 68 is supplied to the band-pass filter 74 so as to extract the 4.43 MHz (fSC) component. The component (3c,)sc) is eliminated from equation (8).An output e3 from the band-pass filter 74 is given as follows: e3=( 1 /2){ (ER-EY)cos(wsct) +(EB-EY)sin(wsct) } +( 1/2)1 (ER-EY)cos(sct)-(EB-EY)sin(sct) I =(ER--EY)cos(#sct) (9) The BY axis component is eliminated from the signal shown in Fig. 5(a), so that only the R-Y axis component is extracted. The R-Y component is supplied to the adder 85 through the line changeover switch 84. Since the line changeover switch 84 is connected and disconnected for each successive line in accordance with the output (Fig. 13(d)) from the oscillator 73, the R-Y component is intermittently supplied to the adder 85.

The adder 85 adds the original signal (NTSC signal EN) from the switch 66 and the output from the line changeover switch 84 at a predetermined ratio and polarity. More specifically, the ratio of the output signal from the switch 66 to the output from the line changeover switch 84 is 1: -2, and these outputs are added by the adder 85 to each other. When the line changeover switch 84 is kept OFF, the output from the adder 85 is the same as that shown in Equation (1) or (2). However, when the line changeover switch 84 is kept ON, an output e4 from the adder 85 is given as follows: e4=EN+(-2 e3) =-( ER-EY)cos(wsct) +( EB-EY)sin(sct) (10) Equation (10) above is equivalent to equation (6). The adder 85 alternately produces the signals given by equations (1) and (6) for every 1 H.Therefore, the NTSC signal is converted to the PAL signal.

The PAL chrominance signal obtained is mixed by the C--Y mixer 75 with the Y signal supplied to the input terminal 52. In this manner, signal conversion can be performed by a simple circuit arrangement.

Fig. 14 is a circuit diagram of the device shown in Fig. 12. The same reference numerals as used in Figs. 7 and 12 denote the same parts in Fig. 14. A circuit of a transistor Q2, resistors R3, R4 and R5, and a capacitor C2 is used to coincide the signal levels at the contacts X1 and X2 of the switch 66. The doubler 69 comprises a doubly-balanced differential amplifier and has the same arrangement as that shown in Fig. 7. The adder 82 comprises a resistor network to add the output (i.e., 8.86-MHz CW signal) from the doubler 69 with the DC component from the bias voltage source 83.The modulator 68 which receives the 8.86-MHz CW signal with the DC component from the adder 82 and the third carrier chrominance signal from the switch 66 has the same arrangement as that shown in Fig. 7. The 4.43-MHz band-pass filter 74 has the same arrangement as that shown in Fig. 7.

Fig. 1 5 shows a color TV signal conversion device according to still another embodiment of the present invention. In the embodiment shown in Fig.15, the modulator 68 (Fig. 12) is replaced with an adder 86, and the adder 82 (Fig. 12) is replaced with a modulator 87.

The modulator 87 multiplies the 8.86-MHz CW signal from a doubler 69 with an original signal (third chrominance signal) from a switch 66. The adder 86 adds the output from the switch 66 with the output from the modulator 87 at a predetermined ratio and polarity.

Referring to Fig.15, the modulator 87 receives an output signal e5 from the doubler 69 and the output (original signal EN) from the switch 66 which are then multiplied to obtain a result as follows: EN x eS={(ER-EY)cos(sct) + (EB-EY)sin(wsct) } x cos(2ct)sct) =(1/2)1 (ER-EY)cos(wsct)-( EB-EY)sin(wsct) +(ER-EY)cos(3msct) +(EB-EY)sin(3cosct)I (11) The output shown in equation (11) is added by the added 86 to the output from the switch 66.If the ratio of the signal from the switch 66 to the signal from the modulator 87 is 1 :2, an output e6 from the adder 86 is given by equation (12) as follows: e6=EN+2 e5 =(ER-EY)cos(wsct)+( EB-EY)sin(wsct) +1 ( ER-EY)cos(wsct)-(EB-EY)sin(cosct) +(ER-EY)cos(30sct)+(EB-EY)sin(30sct) =2(ER-EY)cos(cosct) +(ER-EY)cos(3wsct)+(EB-EY)sin(30sct) (12) The output e6 is supplied to the band-pass filter 74 which eliminates the (3cosc) component therefrom.

An output e7 from the band-pass filter 74 is given as follows: e7=2(ER-EY)cos(wsct) (13) The output e7 is supplied to the adder 85 through the line changeover switch 84. The adder 85 adds the output from the switch 66 with the signal from the line changeover switch 84 in a 1:-1 ratio. When the line changeover switch 84 is kept OFF, the output from the adder 85 is the same as that shown in equation (1). However, when the line changeover switch 84 is kept ON, the output from the adder 85 is the same as the signal given by equation (10) and hence equation (3). The output from the adder 85 is the PAL chrominance signal.

In the device shown in Fig. 12, the band-pass filter 74 is arranged between the modulator 68 and the line changeover switch 84. However, the band-pass filter 74 may be arranged between the line changeover switch 84 and the adder 85 or between the adder 85 and the C--Y mixer 75, thus obtaining the same effect as obtained with reference to Fig. 1 2.

Furthermore, if the line changeover switch 84 is turned off as needed, the signal conversion operation can be arbitrarily stopped.

Furthermore, the doubler 69 may be replaced with an 8.86-MHz oscillator, and the 4.43-MHz oscillator 59 may be replaced with a 1/2 frequency divider.

In the above description, an NTSC signal is converted to a PAL signal. However, a PAL signal may also be converted to an NTSC signal. In this case, when an input (Fig. 5(a)) is supplied to one input end of the adder 85, the line changeover switch 84 is turned off; when the input (Fig. 5(b)) is supplied to this input end of the adder 85, the line changeover switch 84 is turned on. Furthermore, a phase control circuit for controlling the phase of the burst signal must be arranged between the adder 85 and the O-Y mixer 75.

When the color TV signal conversion device of the present invention is used in a video disc player, the signal recorded by the NTSC system can be readily reproduced by a PAL color receiver, and vice versa.

Claims

1. A color TV signal conversion device, comprising: base signal generating means for generating color TV signal data which includes a luminance signal and a first chrominance signal frequency-converted to a low frequency; separating filter means for receiving the color TV signal data and for separating the color TV signal data into the first chrominance signal and the luminance signal; first carrier signal generating means; frequency converting means for converting the first chrominance signal to a second chrominance signal, said frequency converting means having one input end which receives the first chrominance signal from said separating filter means and the other input end which receives a first carrier signal from said first carrier signal generating means;; first band-pass filter means for receiving an output from said frequency converting means and for producing the second chrominance signal at an output end thereof; first switching means for shifting by 450 a phase of a burst signal included in the second chrominance signal from said first band-pass filter means in every other horizontal period and for producing a third chrominance signal including a phase-shifted burst signal at an output end thereof, said first switching means having a first input end which receives the second chrominance signal from said first band-pass filter means through a 450 phase shifter and a second input end which receives the second chrominance signal directly from said first band-pass filter means;; first switch controlling means for alternately selecting said first and second input ends of said first switching means in each successive burst signal period, and for controlling to select said second input end during a period except for the burst signal period such that a horizontal sync signal separated from the luminance signal is delayed and shaped to obtain a burst gate pulse which is applied to a control end of said first switching means; second carrier signal generating means for generating a second carrier signal having a frequency twice a frequency of the first carrier signal from said first carrier signal generating means; and an R-Y component processing circuit for alternately producing the third chrominance signal and a multiplied signal obtained by multiplying the third chrominance signal and the second carrier signal in an analog manner for every other horizontal line, said R-Y component processing circuit having one input end which receives the third chrominance signal from said first switching means and the other input end which receives the second carrier signal from said second carrier signal generating means.

2. A device according to claim 1, wherein said R-Y component processing circuit comprises: second switching means for alternately producing the second carrier signal from said second carrier signal generating means and a DC bias signal from a bias voltage source at an output terminal thereof for every other horizontal line, said second switching means having a first input terminal which receives the second carrier signal and a second input terminal which receives the DC bias signal;; second switch controlling means for frequency-dividing by 1/2 the horizontal sync signal separated from the luminance signal to supply a frequency-divided signal to a control terminal of said second switching means so as to allow said second switching means to alternately select said first and second input terminal for every other horizintal line and to produce an R-Y converted carrier signal at an output terminal of said second switching means;; first modulating means for phase-shifting an R-Y signal component of the third chrominance signal from said first switching means, said first modulating means having one input terminal which receives the third chrominance signal from said first switching means and the other input terminal which receives the R-Y converting carrier signal from said second switching means; and second band-pass filter means, connected to an output terminal of said first modulating means, for extracting a chrominance signal which has a predetermined bandwidth.

3. A device according to claim 1, wherein said R-Y component processing circuit comprises: a first adder for adding the second carrier signal from said second carrier signal generating means and the DC bias signal from said bias voltage source; second modulating means for multiplying the third chrominance signal from said first switching means and the second carrier signal which incudes a DC component from said first adder in an analog manner, said second modulating means having one input terminal which receives the second carrier signal which includes the DC component and the other input terminal which receives the third chrominance signal;; third band-pass filter means, connected to said second modulating means, for extracting the chrominance signal having the predetermined bandwidth; third switching means, connected to an output terminal of said third band-pass filter means, for producing an output corresponding to the output from said third band-pass filter means for every other horizontal line; third switch controlling means for frequency-dividing by 1/2 the horizontal sync signal separated from the luminance signal to supply the frequency-divided signal to a control terminal of said third switching means so as to control ON/OFF operation of said third switching means for every other horizontal line; and second adder for adding the output from said third switching means and an output from said first switching means.

4. A device according to claim 1, wherein said base signal generating means comprises: a turntable on which a video disc is placed; a motor for rotating said turntable; a motor drive circuit for changing a rotational frequency of said motor; and a signal processing circuit for picking up a recorded signal from said video disc on said turntable.

5. A device according to claim 1 , wherein said first carrier signal generating means comprises: a phase comparator for detecting a phase of an output from said first band-pass filter means and a phase of an output from a reference oscillator during a burst signal period and for producing an output corresponding to a phase difference between the outputs at an output terminal thereof, said phase comparator having one input terminal which receives the output from said first band-pass filter means and the other input terminal which receives the output from said reference oscillator; a sample and hold circuit, connected to said output terminal of said phase comparator, for holding the output from said phase comparator for one horizontal period; a low-pass filter for smoothing an output from said sample and hold circuit; and a voltage controlled oscillator an oscillation frequency of which is controlled by a DC output voltage from said low-pass filter so as to produce the first carrier signal.

6. A device according to claim 1, wherein said second carrier signal generating means comprises a reference oscillator and a doubler for doubling a frequency of an oscillation output from said reference oscillator.

7. A device according to claim 1, wherein each of said first and second carrier signal generating means comprises: a reference oscillator for oscillating an oscillation output having a predetermined frequency; a phase comparator for detecting a phase of an output from said first band-pass filter means and a phase of an output from a reference oscillator during a burst signal period and for producing an output corresponding to a phase difference between the outputs at an output terminal thereof, said phase comparator having one input terminal which receives the output from said reference oscillator and the other input terminal which receives the output from said first band-pass filter means; a sample and hold circuit, connected to said output terminal of said phase comparator, for holding the output from said phase comparator for one horizontal period;; a low-pass filter for smoothing an output from said sample and hold circuit; a voltage controlled oscillator an oscillation frequency of which is controlled by a DC voltage of an output from said low-pass filter so as to produce the first carrier signal; and a doubler for receiving the oscillation output from said reference oscillator and for doubling a frequency of the oscillation output to produce a second carrier signal.

8. A device according to claim 2, wherein said second switching means comprises: said first input terminal which receives the second carrier signal from said second carrier signal generating means; said second input terminal grounded through a parallel circuit of a capacitor and a variable resistor; and an output terminal connected to the other input terminal of said first modulating means and to a bias voltage source of said first modulating means.

9. A device according to claim 1, wherein said base signal generating means comprises: a video disc player in which a video disc is placed on a turntable; a motor for rotating said turntable; a motor drive circuit for supplying a drive signal to said motor; and a system changeover switch for supplying a system changeover signal to a control terminal of said motor drive circuit so as to change a rotational frequency of said motor selectively in accordance with an NTSC video disc and a PAL video disc.

10. A device according to claim 1 , which further comprises: a sync separator for separating the horizontal sync signal from the luminance signal; a burst gate pulse generator for delaying, shaping the horizontal sync signal from said sync separator to produce the burst gate pulse; fourth switching means for selectively producing one of the burst gate pulse and a signal having a predetermined level at an output terminal thereof, said fourth switching means having a first input terminal which receives the burst gate pulse from said burst gate pulse generator, a second input terminal which receives the signal having the predetermined level, and said output terminal thereof being connected to said control terminal of said first switching means; a flip-flop for frequency-dividing by 1/2 the horizontal sync signal from said sync separator;; fifth switching means for selectively supplying an output from said flip-flop to a control terminal of said R-Y component processing circuit, said fifth switching means having an input terminal which receives the output from said flip-flop and an output terminal which is connected to said control terminal of said R-Y component processing circuit; and system changeover switch for turning on said fifth switching means when said first input terminal and said output terminal of said fourth switching means are connected to each other, and for turning off said fifth switching means when said second input terminal and said output terminal of said fourth switching means are connected to each other.

11. A device according to claim 1, wherein said R-Y component processing circuit comprises: third modulating means for producing an analog output obtained by multiplying the second carrier signal with the third chrominance signal, said third modulating means having one input terminal which receives the second carrier signal from said second carrier signal generating means and the other input terminal which receives the third chrominance signal from said first switching means; a fourth adder for adding the analog output and the third chrominance signal, said fourth adder having one input terminal which receives the analog output from said third modulating means and the other input terminal which receives the third chrominance signal from said first switching means;; fourth band-pass filter means, connected to an output terminal of said fourth adder, for extracting a signal having a predetermined bandwidth from the output from said fourth adder; sixth switching means, connected to an output terminal of said fourth band-pass filter means, for producing an output corresponding to the output from said fourth band-pass filter means for every other horizontal line; fourth switch controlling means for frequency-dividing by 1/2 the horizontal sync signal separated from the luminance signal to supply the frequency-divided output to said control end of said fourth switching means; and a third adder for adding the output from said fourth switching means and the output from said first switching means.

1 2. A color TV signal conversion device, substantially as hereinbefore described with reference to Figs. 3 to 1 5 of the accompanying drawings.