JPS58223983A - Signal converter - Google Patents

Abstract

PURPOSE:To convert simply a color television signal, by balanced-modulating a chroma signal component of the NTSC system and mixing a signal passing through a demodulating means and a modulating means with a burst signal in matching with the PAL-M system. CONSTITUTION:The chroma signal component 1 of the NTSC system is balanced-modulated at a balanced modulator 4 together with the 1st reference signal. Further, the 1st color signal is demodulated from an output of the balanced- modulator 4 at a B-Y demodulator 7 based on the 2nd reference signal 11. Further, the 2nd color signal is demodulated at an R-Y demodulator 8 based on the 2nd reference signal whose polarity is inverted through a PAL switch 10 at each 1H. Further, the 1st and the 2nd color signals are modulated at B-Y and R-Y modulators 13, 14 the result is mixed at a mixer 16 together with a burst signal matching to the PAL-M system from a burst signal generator 17 to obtain the chroma signal of the PAL-M system.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal conversion device suitable for converting an NTSC color television signal to a PAL-M color television signal adopted in Brazil and other countries.

In general, color television signals of the NTSC and PAL-M systems have the same horizontal and vertical scanning frequencies, and there is no difference in luminance signal components, only chroma signal components. This phase point is the point where the color subcarrier frequency of the chroma signal is shifted by -i/H (where /H is the horizontal scanning frequency), that is, 8.934 KHz, and the point where the vector of the chroma signal is centered on the B-Y axis. This point is inverted every IH (one horizontal scanning period).

The present invention has been made in view of the above points, and is a signal conversion method that can easily convert an NTSC color television signal obtained from a broadcasting station, a VTR, etc. into a PAL-M color television signal. It provides equipment.

In particular, in the present invention, with a simple configuration, 3.579545MH
The NTSC color subcarrier signal of z is 3.5756
At the same time, it is converted into a 11MHz PAL-M color subcarrier signal and inverted for each IH with respect to the B-Y axis.
This is to obtain an LM system color television signal.

The present invention will be described below with reference to embodiments shown in the drawings. The drawing shows a block diagram of an embodiment of the invention, in which an NTSC composite video signal is supplied to the input terminal 1, and a horizontal synchronizing pulse is supplied to the input terminal 2. This composite video signal is now passed through a bandpass filter 3,
An NTSC chroma signal having a color subcarrier component of 3.579545 MHz is derived through this filter 3.

4 ′″0″°～Signal balance ′′chu” 7155155MH obtained from the reference signal oscillator 5
Balanced modulation is performed based on the z reference signal. As a result, a chroma signal in which the color subcarrier component is frequency-converted to 3.575611 MHz is extracted from the balanced modulator 4 via the bandpass filter 6, and this is supplied to the BY demodulator 7 and the R-Y demodulator 8. be done.

On the other hand, the horizontal synchronizing pulse supplied to input terminal 2 is supplied to flip-flop 70, and this flip-flop 9 is connected to II
The IH switching pulse obtained from the flip-flop 9 is supplied to the PAL switch 10, and the PAL switch 10 performs a polarity inversion operation for each IH.

11 is 3 that matches the color subcarrier frequency of the PAL-M system.
, 575,611 MHz color subcarrier oscillator, and the 3,575,611 MHz subcarrier signal oscillated by this oscillator 11 is inverted in polarity for each LH by the PAL switch 10 and then supplied to the R-Y demodulator 8. After being phase-shifted by 90° via a 90° phase shifter 12 consisting of a capacitor C1 and a resistor R1, the signal is supplied to a BY demodulator 7. 1 As a result, the BY demodulator 7 demodulates the BY color difference signal, and the BY demodulator 8- demodulates the RY color difference signal. Note that the color difference signal components obtained from the RY demodulator 8 are modally inverted and blurred for each IH.

In this case, the horizontal synchronizing pulse is supplied from the input terminal 2 to the post-rain modulators 7 and 8, and as a result, the demodulators 7 and 8
In particular, a blanking operation for the burst signal included in the chroma signal is performed at the same time.

In this way, each color difference signal obtained from the demodulators 7 and 8 is supplied to a BY modulator 13 and an RY modulator 14, respectively. The R-Y modulator 14 is supplied with a color subcarrier signal of 3.575611 MHz obtained from the color subcarrier oscillator 9, and the B-Y modulator 13 is supplied with a 90° phase shift signal consisting of a coil L1 and a capacitor C2. 90 through vessel 15
A phase shifted color subcarrier signal is provided. As a result, in both scales 13.14, the B-Y color difference signal and the R-Y color difference signal have a phase difference of 90', 3,575611MH
These modulation numbers 18 are quadrature-two-phase modulated with the color subcarrier of z and are supplied to a mixer 16.

Furthermore, a reference signal of 3,575,611 MHz whose polarity is inverted every 1H is supplied to the burst signal generator 17 via the PAL switch 10, and a horizontal synchronizing pulse is supplied from the input terminal 2. Then, in the generator 17, a burst signal (matching the PAL-M method in which the phase is alternately shifted by ±45° for each IH with respect to the -(B-Y) axis) is created, and this burst signal is also switched. It is supplied to the mixer 16 mentioned above. In the mixer 16,
The modulated signals obtained from each of the modulators 13 and 14 and the noise I signal obtained from the burst signal generator 17 are mixed, and at this time, the output terminal 3. A chroma signal compatible with the 575,611 MHz PAL-M system is derived.

Thus, according to the signal conversion device of the above embodiment, two modulators and demodulators 7, 8, 13 and 14, two reference signal oscillators 5 and 11, and a balanced modulator 4, a PAL switch io, etc. are used. With a simple configuration, an NTSC chroma signal can be converted into a PAL-M chroma signal.

Note that there is no difference in the luminance signal components of both the NTSC system and the PA and LM systems, so by superimposing the NTSC system's brightness signal with the PAL-M system's chroma signal, You can get a color television signal of any system.

As described above, according to the signal conversion device of the present invention, N'I
” Since it is possible to convert an SC system color television signal to a PAL-M system color television signal relatively easily, it is possible to convert it into a PAL-M system color television signal relatively easily.
Once the reproduced color television signal is reproduced using TR and once converted into a PAL-M color television signal by the device of the present invention, it can be easily viewed on a PAL-M television receiver. is not possible.

[Brief explanation of the drawing]

4... Balanced modulator, 5... Reference signal oscillator, 7
...B-Y demodulator, 8...R-Y demodulator, 1
0...PAL switch, 11...Reference signal oscillator, 13...B-Y modulator, 14...R-Y modulator, 16...Mixer, 17...7<-st signal generator.

Claims (1)

[Claims] 1. Means for converting the frequency of the chroma signal by balanced modulating the chroma signal component of the NTSC system together with a first reference signal; a first demodulating means for demodulating a color signal; a means for demodulating a second color signal from the chroma signal based on a signal whose polarity is inverted for each LH by passing the second reference signal through a PAL switch; a first modulation means that modulates the second reference signal based on the first color signal; a second modulation means that modulates the second reference signal based on the second color signal; means for creating a burst signal conforming to the PAL-M system based on the second reference signal, and mixing the both tone signals obtained from the first and second modulation means and the burst signal. 1. A signal conversion device comprising means for obtaining a PAL-M chroma signal, and converting an NTSC chroma signal into a PAL-M chroma signal.