JPH073740Y2 - Carrier color signal converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to an apparatus provided in, for example, a video tape recorder for export, for converting between an NTSC system and a PAL system, and particularly for converting a carrier color signal.

<Prior Art> For example, some video tape recorders exported to European countries are equipped with a device for converting the NTSC system to the PAL system. Among such system converters, an apparatus for converting a carrier color signal is shown in FIG. 2, for example. In the figure, the amplifier circuit 20 includes
NT separated from the luminance signal by a comb filter (not shown)
SC-type carrier color signal is given. The carrier color signal amplified by the amplifier circuit 20 is demodulated by the demodulation circuit 21 and the color synchronization circuit 22.
Given to each. The color synchronization circuit 22 includes an automatic phase control circuit (APC) 23 and an oscillation circuit 24 having a frequency (f = 3.579545MHz) corresponding to an NTSC color subcarrier, and outputs a color subcarrier for demodulation. . The demodulation circuit 21 demodulates the color difference signal from the carrier color signal using this color subcarrier. This color difference signal is given to the modulation circuit 26 via the low pass filter 25. This modulation circuit 26 has a PA
Frequency corresponding to L sub-system color subcarrier (f = 4.433619MH
The color subcarrier from the oscillation circuit 27 of z) is given,
This color subcarrier is modulated with the color difference signal from the low pass filter 25 to form a PAL system carrier color signal. The PAL type carrier color signal is output through the bandpass filter 28.

In such a conventional carrier color signal converter, only a one-way conversion from the NTSC system to the PAL system is possible, and a carrier color signal converter capable of mutual conversion in both directions is desired.

For example, in the conventional example of FIG. 2, in order to enable conversion from the PAL system to the NTSC system, simply speaking, in addition to the above two oscillation circuits 24 and 27, further, the PAL system transport is performed. It is good to provide two oscillation circuits, one for demodulating the color signal and the other for modulating the demodulated color difference signal into the carrier color signal of the NTSC system, but the number of parts increases. There is a problem that the manufacturing cost is high.

<Purpose of Invention> The present invention has been made in view of the above points, and has a relatively simple configuration without increasing the number of oscillation circuits.
An object of the present invention is to provide a carrier color signal conversion device capable of mutually converting an SC carrier color signal and a PAL carrier color signal.

<Construction of Device> In order to achieve the above-mentioned object, the present invention is a carrier color signal conversion device for performing mutual conversion between an NTSC carrier color signal and a PAL carrier color signal, NTSC equipped with an oscillating circuit having a frequency corresponding to the color sub-carrier and an automatic phase control circuit for controlling the phase of the output of the oscillating circuit so that the color sub-carrier matches the phase of the burst signal of the input carrier color signal. The color synchronization circuit for the system, the oscillation circuit of the frequency corresponding to the color subcarrier of the PAL system, and the phase of the output of the oscillation circuit so as to be the color subcarrier that matches the phase of the burst signal of the input carrier color signal. A PAL system color synchronizing circuit having an automatic phase control circuit for controlling, and a carrier color signal to be converted are provided, and based on a switching signal corresponding to the conversion, the carrier color signal in the two color synchronizing circuits is controlled. Pair of A carrier color signal switching circuit for switching and outputting to a corresponding color synchronizing circuit and each color subcarrier output from each of the color synchronizing circuits are given together, and based on the switching signal, one corresponding color subcarrier is A demodulation color subcarrier switching circuit for switching and outputting as a demodulation color subcarrier and each color subcarrier output from each of the color synchronization circuits are given together, and based on the switching signal, the corresponding other color subcarrier is supplied. A modulation color subcarrier switching circuit for switching and outputting a carrier as a color subcarrier for modulation, and a color difference signal from the carrier color signal to be converted by the one color subcarrier from the demodulation color subcarrier switching circuit. And a modulation circuit for modulating the other color subcarrier from the modulation color subcarrier switching circuit with a color difference signal from the demodulation circuit.

According to the above configuration, each color sub-carrier output from the NTSC system color synchronizing circuit including the NTSC system oscillation circuit and the PAL system color synchronizing circuit including the PAL system oscillation circuit is used for demodulation color The sub-carrier switching circuit and the modulation color sub-carrier switching circuit switch and output to the demodulation circuit and the modulation circuit based on the switching signal according to the conversion, so that they are also used as the demodulation color sub-carrier and the modulation color sub-carrier. It is possible to perform mutual conversion between an NTSC carrier color signal and a PAL carrier color signal with two oscillator circuits, an NTSC system color synchronization circuit oscillator circuit and a PAL system color synchronization circuit oscillator circuit. .

<Embodiment> An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram of an embodiment of the present invention.
The carrier color signal converter of this embodiment is basically an NTSC
Frequency corresponding to the color subcarrier for the system (f = 3.579545MH
z) oscillation circuit 8 and automatic phase control circuit (APC) 9 for NTSC system color synchronization circuit 1 and PAL system for color subcarrier frequency (f = 4.433619MHz) oscillation circuit 10
And a PAL system color synchronizing circuit 2 having an automatic phase control circuit (APC) 11, and a carrier color signal to be converted corresponding to an NTSC system or PAL system based on a switching signal corresponding to the conversion.
The carrier color signal conversion circuit 3 for switching and outputting to the system color synchronizing circuit 1 or 2 and each color subcarrier from both color synchronizing circuits 1 and 2 are given together, and based on the switching signal, one of the corresponding color subcarriers is supplied. A demodulation color subcarrier switching circuit 4 for switching and outputting a carrier and each color subcarrier from both color synchronizing circuits 1 and 2 are given together, and the corresponding other color subcarrier is switched and output based on the switching signal. A modulation color subcarrier switching circuit 5 and a demodulation circuit 6 for demodulating a color difference signal from a carrier color signal to be converted by the color subcarrier of the demodulation color subcarrier switching circuit 4.
And a modulation circuit 7 for modulating the color subcarrier from the modulation color subcarrier switching circuit 5 with the color difference signal from the demodulation circuit 6.

The carrier color signal switching circuit 3 is supplied with the carrier color signal to be converted, which is amplified by the amplifier circuit 12, and a switching signal corresponding to the conversion, for example, by a manual operation. Based on this switching signal, the carrier color signal switching circuit 3 switches and outputs the carrier color signal to the corresponding NTSC system or PAL system color synchronizing circuit 1 or 2.

For example, in the case of converting an NTSC system carrier color signal into a PAL system carrier color signal, the carrier color signal switching circuit 3 includes an NTSC
The carrier color signal of the system and the switching signal corresponding to the conversion are given, and thereby the carrier color signal of the NTSC system is output to the corresponding color synchronizing circuit 1 for the NTSC system. Further, when converting a PAL system carrier color signal into an NTSC system carrier color signal, the carrier color signal conversion circuit 3 is provided with a PAL system carrier color signal and a switching signal corresponding to the conversion. Outputs the PAL system carrier color signal to the corresponding PAL system color synchronizing circuit 2.

NTSC system color synchronization circuit 1 and PAL system color synchronization circuit 2
Are provided with automatic phase control circuits (APC) 9 and 11, respectively. Each of the color synchronization circuits 1 and 2 outputs each color subcarrier corresponding to each system to the demodulation color subcarrier switching circuit 4 and the modulation color subcarrier switching circuit 5, respectively. Synchronous circuit for each color 1, 2
When the carrier color signal is supplied from the carrier color signal conversion circuit 3, outputs a color subcarrier that matches the phase of the burst signal of the carrier color signal.

The demodulation color subcarrier switching circuit 4 is supplied with each color subcarrier from the two-color synchronizing circuits 1 and 2 and the switching signal, and one of the corresponding color subcarriers is demodulated based on the switching signal. Is output to the demodulation circuit 6. For example, when converting an NTSC system carrier color signal to a PAL system carrier color signal, the color subcarrier from the NTSC system color synchronizing circuit 1 is sent to the demodulation circuit 6 based on a switching signal corresponding to the conversion. In the case of outputting and converting the PAL system carrier color signal into the NTSC system carrier color signal, the color subcarrier from the PAL system color synchronizing circuit 2 is demodulated based on the switching signal corresponding to the conversion. Output to 6.

The modulation color subcarrier switching circuit 5 is supplied with the respective color subcarriers and the switching signals from the two-color synchronizing circuits 1 and 2, and the other corresponding color subcarrier is supplied to the modulation circuit 7 based on the switching signal. Output as color subcarrier. For example, when converting the carrier color signal of the NTSC system into the carrier color signal of the PAL system, the color subcarrier from the PAL system color synchronizing circuit 2 is supplied to the modulation circuit 7 based on the switching signal corresponding to the conversion. Output,
When converting the PAL system carrier color signal to the NTSC system carrier color signal, the color subcarrier from the NTSC system color synchronizing circuit 1 is supplied to the modulating circuit 7 based on the switching signal corresponding to the conversion. Output.

The demodulation circuit 6 is supplied with the carrier color signal to be converted from the amplifier circuit 12 and the demodulation color subcarrier from the demodulation color subcarrier switching circuit 4. The demodulation circuit 6 demodulates the color difference signal from the carrier color signal to be converted by the color subcarrier. The output of this demodulation circuit 6 is
The carrier wave and the like are removed by the low-pass filter 13 and only the color difference signal is given to the modulation circuit 7.

The color difference signal is given to the modulation circuit 7 through the low-pass filter 13, and the color subcarrier for modulation is given from the color subcarrier for switching circuit 5. The modulation circuit 7 modulates the color subcarrier with a color difference signal and outputs it as a carrier color signal to the bandpass filter 14. The bandpass filter 14 removes higher harmonics and outputs the carrier color signal converted into a desired format.

Note that, unlike the NTSC method, the PAL method inverts the polarity every 1H (1H is a horizontal scanning period). Therefore, in the demodulation circuit 6 and the modulation circuit 7, for example, corresponding demodulation and modulation are performed based on the switching signal. Is performed.

Next, in the carrier color signal conversion device having the above configuration,
The operation of converting an NTSC system carrier color signal into a PAL system carrier color signal will be described. To the amplifier circuit 12, an NTSC carrier color signal separated from the luminance signal by a comb filter (not shown) is given. The carrier color signal amplified by the amplifier circuit 12 is given to the carrier color signal switching circuit 3 and the demodulation circuit 6, respectively. The carrier color signal switching circuit 3 has an NTSC
A switching signal corresponding to the conversion from the system to the PAL system is provided. As a result, the carrier color signal switching circuit 3 outputs the NTSC system carrier color signal to the NTSC system color synchronizing circuit 1.

In the NTSC system color synchronizing circuit 1, the frequency f in phase with the burst signal of the carrier color signal from the carrier color signal switching circuit 3
The color subcarrier for NTSC system of 3.579545 MHz is output to the demodulation color subcarrier switching circuit 4 and the modulation color subcarrier switching circuit 5. At this time, from the PAL system color synchronizing circuit 2,
A color subcarrier for the PAL system having a frequency f = 4.433619 MHz is supplied to the demodulation color subcarrier switching circuit 4 and the modulation color subcarrier switching circuit 2.

In the demodulation color subcarrier switching circuit 4, based on the switching signal corresponding to the conversion from the NTSC system to the PAL system, the color subcarrier (f) corresponding to the NTSC system from the NTSC system color synchronization circuit 1 (f
= 3.579545MHz) to the demodulation circuit 6.

In the modulation color subcarrier switching circuit 5, based on the switching signal corresponding to the conversion from the NTSC system to the PAL system, the color subcarrier (f corresponding to the PAL system from the PAL system color synchronization circuit 2 (f
= 4.433619MHz) is output to the modulation circuit 7.

In the demodulation circuit 6, the color subcarrier for the NTSC system (f = 3.5795
45 MHz), the color difference signal is demodulated from the NTSC system carrier color signal from the amplifier circuit 12. The demodulated color difference signal is applied to the modulation circuit 7 via the low pass filter 13.

In the modulation circuit 7, the PA from the modulation color subcarrier switching circuit 5
The color subcarrier (f = 4.433619MHz) corresponding to the L system is modulated by the color difference signal and output as a carrier color signal of the PAL system through the bandpass filter 14.

Next, when converting the PAL system carrier color signal to the NTSC system carrier color signal, the PAL system carrier color signal is given to the amplifier circuit 12. The carrier color signal switching circuit 3, the demodulation color subcarrier switching circuit 4 and the modulation color subcarrier switching circuit 5 include:
A switching signal corresponding to the conversion is applied, and based on this switching signal, switching is performed in the opposite direction to the above-described conversion from the NTSC system to the PAL system. That is, the carrier color signal switching circuit 3 outputs the PAL system carrier color signal from the amplifier circuit 12 to the PAL system color synchronizing circuit 2 based on the switching signal. The demodulation color subcarrier switching circuit 4 outputs the color subcarrier (f = 4.433619 MHz) corresponding to the PAL system from the PAL system color synchronization circuit 2 to the demodulation circuit 6 based on the switching signal. The modulation color subcarrier switching circuit 5 outputs the color subcarrier (f = 3.579545 MHz) corresponding to the NTSC system from the NTSC system color period circuit 1 to the modulation circuit 7 based on the switching signal.

As a result, the demodulation circuit 6 demodulates with the color subcarrier corresponding to the PAL system (f = 4.433619MHz), and the modulation circuit 7 modulates with the color subcarrier corresponding to the NTSC system (f = 3.579545MHz). Done. In this way, the PAL system carrier color signal is converted into the NTSC system carrier color signal and output.

In this way, the respective color subcarriers from the NTSC system color synchronizing circuit 1 and the PAL system color synchronizing circuit 2 are switched and output by the demodulating color subcarrier switching circuit 4 and the modulating color subcarrier switching circuit 5 in accordance with the conversion. By doing so, it can be used for both demodulation and modulation, so that the mutual conversion between the NTSC system carrier color signal and the PAL system carrier color signal can be performed with a relatively simple configuration of two oscillator circuits 8 and 10 similar to the conventional one. It will be possible.

<Effects of the Invention> As described above, according to the present invention, each color subcarrier from the NTSC system color synchronization circuit and the PAL system color synchronization circuit is demodulated to a demodulation color subcarrier switching circuit and a modulation color subcarrier switching circuit. By switching output according to the conversion, it can be used for both demodulation and modulation, so it has a relatively simple structure of two oscillation circuits similar to the conventional one, and therefore a relatively low manufacturing cost. Mutual conversion between a color signal and a PAL system carrier color signal is possible.

Moreover, since each color synchronization circuit is provided with the automatic phase control circuit, a stable color subcarrier with a small phase error can be given to the demodulation circuit.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional example. 1 ... NTSC system color synchronizing circuit, 2 ... PAL system color synchronizing circuit, 3 ... carrier color signal switching circuit, 4 ... demodulation color subcarrier switching circuit, 5 ... modulation color subcarrier switching circuit , 6 ...
… Demodulation circuit, 7… Modulation circuit.

Claims (1)

[Scope of utility model registration request] 1. A carrier color signal converter for performing mutual conversion between an NTSC carrier color signal and a PAL carrier color signal, wherein an oscillation circuit and an input of a frequency corresponding to an NTSC system color subcarrier are provided. Color synchronization circuit for NTSC system equipped with an automatic phase control circuit that controls the phase of the output of the oscillation circuit so that the color subcarrier that matches the phase of the burst signal of the carrier color signal, and the PAL system color subcarrier Color synchronization for PAL system equipped with an oscillating circuit having a frequency corresponding to the above and an automatic phase control circuit for controlling the phase of the output of the oscillating circuit so as to obtain a color subcarrier that matches the phase of the burst signal of the input carrier color signal A carrier color signal to be converted, and a carrier color signal for switching and outputting the carrier color signal to a corresponding color synchronizing circuit of the two color synchronizing circuits based on a switching signal corresponding to the conversion. The conversion circuit and the respective color subcarriers respectively output from the both-color synchronizing circuit are given together, and one of the corresponding color subcarriers is switched and output as a color subcarrier for demodulation based on the switching signal. The color sub-carrier switching circuit and each color sub-carrier output from each of the color synchronizing circuits are given together, and the other corresponding color sub-carrier is switched and output as a color sub-carrier for modulation based on the switching signal. A modulation color subcarrier switching circuit, a demodulation circuit that demodulates a color difference signal from the carrier color signal to be converted by the one color subcarrier from the demodulation color subcarrier switching circuit, and the modulation color subcarrier A carrier color signal conversion device, comprising: a modulation circuit that modulates the other color subcarrier from the carrier switching circuit with a color difference signal from the demodulation circuit.