JPH07170533A - Color signal system converter - Google Patents

Abstract

PURPOSE:To obtain a color signal system converter suitable for circuit integration in which no hue fluctuation takes place due to conversion of a chroma signal even when the phase of signal from a 90 deg. phase sifter is in variation resulting from dispersion in manufacture. CONSTITUTION:A burst signal B among an input signal and the signal B passing through a 90 deg. phase sifter 1 is switched for each 1H in the color signal system converter. Furthermore, the sum of a chroma signal C in the input signal and an output chroma signal from the phase shifter 1 at an adder 5 or the output of a voltage source 3 is selected for each 1H. Thus, a phase difference between the original signal being the output of the adder 5 and the signal resulting from 90 deg.- phase sifting the signal is 45 deg., and then is establishes a pseudo PAL conversion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color signal system conversion device, and more particularly to a color signal system conversion device for performing color signal system conversion from an NTSC signal of a carrier color signal to a PAL signal in television signal processing. .

[0002]

2. Description of the Related Art In conventional television signal processing,
FIG. 5 shows the configuration of the color signal system conversion apparatus from the NTSC signal to the pseudo PAL signal. In FIG. 5, 50 is NTSC
Input terminal for inputting a carrier color signal (hereinafter, referred to as an NTSC signal) of the system, 51 denotes an input carrier color signal of +45.
+ 45 ° phase shifter for phase shifting, 52-45 ° phase shifter for shifting input carrier color signal by -45 °, 2 an amplifier for amplifying input carrier color signal by a predetermined amplification factor, 3 is a voltage source having a predetermined voltage value whose one end is grounded, and 4 is the above +
It is a switch that switches and outputs any one of the four signals from the 45 ° phase shifter 51, the −45 ° phase shifter 52, the amplifier 2, and the voltage source 3. Then, the NTSC signal input by these is converted into a carrier color signal of a pseudo PAL system (hereinafter, referred to as a pseudo PAL signal),
It is output from the output terminal 54. In addition, FIG.
(a), (b) is a waveform diagram showing an NTSC signal, a pseudo PAL signal, and their phase relationship.

Next, the operation will be described. In television signal processing, NT
When the signal is converted from the SC signal to the pseudo PAL signal, the burst signal B of the input NTSC-system carrier color signals is +45 the input carrier color signal at every horizontal period.
The output of the + 45 ° phase shifter 51 shifted by ° and the output of the -45 ° phase shifter 52 shifted by -45 ° from the input carrier color signal are switched. For example, the signal amplified by the amplifier 2 by +6 dB and the predetermined voltage of the voltage source 3 are switched. This state is shown in FIG.

When the NTSC signal shown in FIGS. 6 (a) and 6 (b) is converted into a pseudo PAL signal, the burst signal B becomes
(c) As shown in (d), it swings ± 45 ° for every 1H (b1 swings + 45 ° and b2 swings -45 ° in FIG. 6D), and the chroma signal C is + 6d.
The B-amplified C1 and the cut-off C2 are switched every 1H. As a result, a pseudo PAL signal as shown in FIG. 6 (c) is generated.

However, when the + 45 ° phase shifter 51 and the −45 ° phase shifter 52 are configured in the IC, the phase shifters 51 and 52 are phased in the same direction due to variations in manufacturing of the IC. It shifts. Therefore, as shown in FIG. 6 (e), the phase relationship between the chroma signal C and the burst signal B (chroma signal C
The phase of 1 is c1 'and the phases of burst signals B1 and B2 are b
1 ', b2') goes wrong and the hue turns. Therefore, at present, it is necessary to configure or adjust the ± 45 ° phase shifters 51 and 52 outside the IC, which causes a cost increase.

[0006]

As described above, in the conventional color signal system converter, the + 45 ° phase shifters 51, -45 are used.
° When the phase shifter 52 is configured in the IC, the phase shifters 51 and 52 are out of phase in the same direction due to variations in the manufacture of the IC, and the chroma signal and the burst signal are shifted as shown in Fig. 6 (e). Since the phase relationship with and shifts the hue, it is now necessary to configure the ± 45 ° phase shifters 51 and 52 outside the IC or to adjust them, which is a factor of cost increase. There is a problem that it has become.

The present invention has been made in order to solve the above-mentioned problems, and even if the phase of the 90 ° phase shifter shifts due to manufacturing variations, there is no change in hue due to conversion of the chroma signal. It is an object of the present invention to obtain a color signal system conversion device which is obtained and which is suitable for use as an IC.

[0008]

A color signal system converter according to the present invention adds a phase shifter for shifting an input carrier color signal by 90 °, and an output of the phase shifter and the input signal. An adder for amplifying the output of the adder, a switch for switching four signals among the input signal, the output of the phase shifter, the output of the amplifier, and the DC voltage, and a burst signal Switching the output of the input signal and the output of the phase shifter for each horizontal period and outputting as a chroma signal by switching the DC voltage and the output of the amplifier for each horizontal period. Is.

Further, according to the present invention, in the above-mentioned color signal system converter, the carrier color signal has the same structure as the first phase shifter (variable phase shifter) for phase-shifting the inputted carrier color signal by 90 °. A second variable phase shifter having a frequency sine wave as an input; and a wave detector for phase-comparing the input carrier color signal frequency sine wave with the output of the second phase shifter, The second variable phase shifter is controlled by the output of the wave detector so that the phase shift amount of the second variable phase shifter becomes 90 °, and the first phase shift to which the carrier color signal is input. The output of the detector controls the phase shifter so that the phase shift amount of the first phase shifter becomes 90 °.

Further, according to the present invention, in the above-mentioned color signal system conversion device, the input carrier color signal and the output of a first phase shifter (variable phase shifter) for phase-shifting the input carrier color signal by 90 ° are provided. Of the first phase shifter is controlled by the output of the detector so that the phase shift amount of the first phase shifter becomes 90 °.

[0011]

According to the present invention, the phase shifter for shifting the input carrier color signal by 90 °, the adder for adding the output of the phase shifter and the input signal, and the output of the adder are amplified. And a switch for switching four signals among the input signal, the output of the phase shifter, the output of the amplifier, and the DC voltage. The burst signal includes the input signal every horizontal period and the switch. The output of the phase shifter is switched and output, and as a chroma signal, the DC voltage
And a configuration in which the output of the amplifier is switched and output, and the sum of the input and the 90 ° phase shifter output is used as a chroma signal, and the 90 ° phase shifter output and the input signal are used as two bursts. Therefore, even if the phase of the 90 ° phase shifter shifts due to manufacturing variations, it is possible to obtain the one that does not cause the hue variation due to the conversion of the chroma signal, and the color signal system conversion device suitable for IC implementation can be obtained.

Further, according to the present invention, a second variable shifter having a sine wave of a carrier color signal frequency as an input, which has the same structure as the first phase shifter for 90 ° phase-shifting the inputted carrier color signal. A phaser, a sine wave of the input carrier color signal frequency,
A detector for phase-comparing the output of the second phase shifter, and the second variable phase shifter having the output of the detector,
The phase shift amount of the second variable phase shifter is controlled to be 90 °, and the first phase shifter to which the carrier color signal is input is controlled by the output of the detector. Since the phase shift amount of the phase shifter is controlled to be 90 °, an apparatus capable of performing more accurate color signal system conversion can be obtained.

Further, according to the present invention, the input carrier color signal and the first carrier color signal are phased by 90 °.
Since it has a wave detector that performs phase detection with the output of the phase shifter, the output of this wave detector controls the phase shift amount of the first phase shifter so that it becomes 90 °. The circuit configuration becomes simpler.

[0014]

EXAMPLES Example 1 FIG. 1 shows a color signal system converter for converting NTSC to pseudo PAL according to a first embodiment of the present invention. In FIG. 1, 10 is an input terminal to which an NTSC carrier color signal is input, 1 is a 90 ° phase shifter that shifts the input carrier color signal by + 90 °, and 5 is an input carrier color signal and the above 90 °. An adder that adds the output of the phase shifter,
2 is an amplifier that amplifies the output of the adder 5, 3 is a constant voltage source whose one end is grounded, 4 is the output of the 90 ° phase shifter 1, the output of the amplifier 2, and the input carrier color A switch for switching between a signal and one of four signals of the voltage of the constant voltage source 3 and outputting the signal to the output terminal 11.

FIG. 7 shows an example of the 90 ° phase shifter 1, in which 70 is an input, 71 is an NPN transistor, 72, 73 and 74 are resistors, 75 is a capacitor, 7
6 is an output. FIG. 2 is a diagram showing the output waveform of each part during the operation of the circuit of FIG. 1 above. FIG. 2 (a) shows the input carrier color signal, B is a burst signal, and C is a chroma signal. is there. 2 (b) shows the phase of each part of FIG. 2 (a) of the input signal, FIG. 2 (c) shows the phase of the output of the 90 ° phase shifter 1, and FIG. 2 (d) shows The output phase of the adder 5 and the amplifier 2 is shown, and FIG. 2 (e) shows the output of the switch 4 and its phase.

Next, the operation of the apparatus according to the first embodiment will be described with reference to FIGS. 1, 2, and 7. Regarding the burst signal B of the input signals, the switch 4 switches between the one that has passed through the 90 ° phase shifter 1 and the input burst signal every 1H (one horizontal period). As for the chroma signal C, the input signal and the output of the 90 ° phase shifter 1 are added by the adder 5 and the output of the voltage source 3 are switched every 1H (one horizontal period). The output of the adder 5 is the input signal 9
Since it is the sum of the phase-shifted 0 ° and the original signal, the phase difference between the output of the adder 5 (or the output of the amplifier 2) and the original signal and the phase-shifted 90 ° is 45 °, respectively.
Then, the output of the switch 4 is as shown in FIGS. 2 (e) and 2 (f), which is established as a pseudo PAL conversion.

At this time, even if the phase of the 90 ° phase shifter 1 is shifted due to variations, the chroma signal C has two bursts B.
Since it comes to the center of, the hue change due to conversion does not occur. That is, in the PAL system, as the reference phase of the color signal,
Since the central phase of the two bursts B is used, even if the phase shift amount of the 90 ° phase shifter 1 varies, the input and the 90 ° phase shifter 1
Since the sum of the output and the output is used as the color signal, the color signal C always comes to the center of the two burst signals B. Therefore, 90
The hue change due to the variation of the phase shifter 1 does not occur.

As described above, in the color signal system converter according to the first embodiment, the burst signal B among the input signals is
The input burst signal and the one that has passed through the 90 ° phase shifter 1 are switched every 1H, and the chroma signal C is obtained by adding the input signal and the output of the 90 ° phase shifter 1 by the adder 5. Since the output of the voltage source 3 and the output of the voltage source 3 are switched for each 1H, the phase difference between the output of the adder 5 and the original signal and the output of 90 ° phase is 45 °, respectively, so that the pseudo PAL conversion is established. Since the circuit is configured as described above, even if the phase of the 90 ° phase shifter 1 is deviated due to manufacturing variations, it is possible to obtain a color signal conversion device that does not cause a hue change due to conversion of a chroma signal, and is suitable for IC conversion. There is an effect that can be obtained.

Example 2 FIG. 3 shows a color signal system converter for converting NTSC to pseudo PAL according to a second embodiment of the present invention. In FIG. 3, 31 and 32 are first and second variable phase shifters having the same circuit configuration as each other,
Among them, the first variable phase shifter 31 receives the inputted carrier color signal INPUT as its input and shifts the phase by + 90 °, as in the first embodiment. Also, the second
The variable phase shifter 32 of (1) receives the frequency fsc of the input carrier color signal to the carrier color signal frequency input terminal 30 as an input, and
The phase is shifted by 90 °. Reference numeral 6 designates the output of the second variable phase shifter 32 as the carrier color signal frequency input terminal 3
A phase detector for detecting the carrier color signal fsc which is an input to 0, 7 is grounded at one end, the output of the phase detector 6 is applied to the other end, and the voltage is the first and second variable The capacitors are input to the control inputs of the phase shifters 31 and 32. Further, FIG. 8 shows the first and second variable phase shifters 31, 3 described above.
2 is a diagram showing a detailed circuit configuration of No. 2 in FIG.
Is an input, 81 is a voltage-current converter, 82 is an inverter, 83 is a capacitor, and 84 is an output.

Next, the operation of the apparatus according to the second embodiment will be described. The second phase shifter 32 of the first and second phase shifters
Is input with a sine wave of fsc (carrier color signal frequency) to the input terminal 30, and the first phase shifter 31 is input with an NTSC carrier color signal whose format is to be converted. Carrier color signal frequency fsc phase-shifted by 90 ° by the second phase shifter 32
Is detected by the original input signal fsc and the phase detector 6,
After being smoothed by the capacitor 7, the first and second phase shifters 3
1, 32 is input as a control input to control the amount of phase shift. As a result, a PLL loop (Phase Locked L) by the second phase shifter 32, the phase detector 6, and the capacitor 7 is obtained.
oop, phase lock rope) is formed, and feedback is applied so that the phase shift amounts of the first and second phase shifters 31 and 32 become 90 °. As a result, the color signal system converter including the first phase shifter 31, the amplifier 2, the constant voltage source 3, the switch 4, and the adder 5 performs the same operation as in the first embodiment, and As described above, since the phase shift amount of the first variable phase shifter 31 is maintained at 90 ° regardless of variations, there is no fluctuation in the phase difference between burst signals due to variations as compared with the first embodiment. It is possible to perform more accurate color signal system conversion.

As described above, in the color signal system converter according to the second embodiment, the sine wave of the input carrier frequency fsc is input to the second phase shifter 32 of both phase shifters, and the first phase shifter is used. Bowl 3
The input color signal INPUT to be converted in system 1 is input to 1, and the carrier color signal frequency fsc phase-shifted by 90 ° by the second phase shifter 32 is detected by the original input signal fsc and the phase detector 6. After that, the PLL loop (Phase Lo) is input to the first and second phase shifters 31 and 32 to control the phase shift amount.
ck Loop) and the feedback is applied so that the phase shift amount of both phase shifters 31 and 32 is 90 °. Therefore, the color signal system conversion including the first phase shifter 31 is performed. In the device, the phase shift amount of the phase shifter 31 is maintained at 90 ° regardless of manufacturing variations, and there is no fluctuation in the phase difference between bursts due to manufacturing variations as compared with the first embodiment. There is an effect that more accurate color signal system conversion can be performed.

Example 3 FIG. 4 shows a color signal system converter according to a third embodiment of the present invention. In the figure, 6 is a 90 ° phase shifter (variable phase shifter) corresponding to the first phase shifter 1 of FIG. The output of 41 is detected by the input carrier color signal INPUT, and the phase detector for controlling the phase shift amount of the 90 ° phase shifter (variable phase shifter) 41 to 90 ° by the detected output, 7 is one Is a grounded capacitor, the output of the phase detector 6 is applied to the other end, and the voltage is input to the control input of the variable phase shifter 41.

Next, the operation of the third embodiment will be described. In the third embodiment, as in the first embodiment, the 90 ° phase shifter 41, the amplifier 2, the constant voltage source 3, the switch 4, and the adder 5 constitute a color signal system converter. There is.

The output of the 90 ° phase shifter 41 and the input signal are subjected to phase detection by the phase detector 6 over the burst period or the entire period, and after the detected output is smoothed by the capacitor 7, By inputting the 90 ° phase shifter 41 and controlling the amount of phase shift, the phase shifter 4
1, a PLL loop is formed by the multiplier 6 and the capacitor 7, so that feedback is applied so that the phase shift amount of the phase shifter 41 becomes 90 °, which is similar to the second embodiment. , It is possible to perform accurate system conversion into a pseudo PAL signal. Further, in the third embodiment, as compared with the circuit of the second embodiment shown in FIG. 3, only one 90 ° phase shifter (variable phase shifter) is required, so that the circuit scale can be reduced.

[0025]

As described above, according to the present invention, in the television signal processing, in the color signal system conversion device for performing the color signal system conversion from the NTSC signal of the carrier color signal to the PAL signal, a 90 ° phase shift is performed. And input 90
° The sum of the output of the phase shifter is used as the chroma signal, and the 90 ° phase shifter output and the input signal are used as two bursts. Therefore, due to variations in the amount of phase shift due to manufacturing variations of the 90 ° phase shifter, Also, there is an effect that it is possible to provide a color signal conversion device which is suitable for an IC and does not have a hue change due to conversion of a chroma signal.

Further, according to the present invention, a second phase shifter having the same configuration as that of the first phase shifter constituting the color signal system conversion circuit is provided, and the carrier color signal frequency is set to the second phase shifter. A phase-shifted phase shifter is used to detect the original carrier color signal frequency to form a PLL loop, and feedback is applied so that the phase shift amount of both phase shifters becomes 90 °. Therefore, in the phase shifter of the color signal system converter, the phase shift amount is maintained at 90 ° regardless of the manufacturing variations, and there is no fluctuation in the phase difference between the burst signals due to variations, and more accurate. There is an effect that color signal system conversion can be performed.

According to the present invention, the output of the 90 ° phase shifter and the input signal are phase-detected by the phase detector over the burst period or the entire period, and the 90 ° phase shifter shifts according to the detected output. Since the PLL loop including the phase shifter is configured by controlling the phase amount,
As a result, more accurate color signal system conversion can be performed and the circuit scale can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a color signal system converter according to a first embodiment of the present invention.

FIG. 2 is a diagram showing signals in the first embodiment and states of their phases.

FIG. 3 is a diagram showing a color signal system converter according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a color signal system converter according to a third embodiment of the present invention.

FIG. 5 is a diagram showing a conventional color signal system conversion device.

FIG. 6 is a diagram showing a signal and a state of its phase in the conventional device of FIG.

FIG. 7 is a 90 ° phase shifter 1 in the circuit of Embodiment 1 of FIG.
FIG.

FIG. 8 is a diagram showing the configuration of first and second variable phase shifters in the circuit of the second embodiment of FIG.

[Explanation of symbols]

 1 90 ° phase shifter 2 amplifier 3 voltage source 4 switch 5 adder 6 phase detector 7 capacitor 10 input terminal 11 output terminal 30 carrier color signal frequency input terminal 31, 32, 41 variable phase shifter

Claims (3)

[Claims] 1. A color signal system converter, comprising: a phase shifter for shifting an input carrier color signal by 90 degrees; an adder for adding an output of the phase shifter and the input signal; and an adder. An amplifier for amplifying the output of the input signal, the input signal, the output of the phase shifter, the output of the amplifier,
And a switch for switching four signals of DC voltage, and outputs the input signal and the output of the phase shifter by switching as a burst signal for each horizontal period, and as a chroma signal for each horizontal period. A color signal system conversion device characterized in that the DC voltage and the output of the amplifier are switched and output. 2. The color signal system conversion apparatus according to claim 1, wherein the first phase shifter for phase-shifting the input carrier color signal by 90 ° is a variable phase shifter. A second variable phase shifter having the same configuration as the variable phase shifter and having a sine wave of the carrier color signal frequency as an input; a sine wave of the input carrier color signal frequency; and a second phase shifter of the second phase shifter. A detector for phase-comparing with the output, and controlling the second variable phase shifter with the output of the detector so that the phase shift amount of the second variable phase shifter becomes 90 °, The first phase shifter to which the carrier color signal is input is controlled so that the phase shift amount of the first phase shifter becomes 90 ° by the output of the wave detector. Color signal system converter. 3. The color signal system conversion apparatus according to claim 1, wherein the first phase shifter for phase-shifting the input carrier color signal by 90 ° is a variable phase shifter, and the input carrier color. A phase detector that performs phase detection between a signal and the output of the first variable phase shifter is provided, and the phase shift amount of the first variable phase shifter is 90 ° by the output of the phase detector. A color signal system conversion device characterized in that it is controlled so that.