JPH05211657A - Multi-system carrier chrominance signal demodulator - Google Patents

Abstract

PURPOSE:To provide an inexpensive multi-system carrier chrominance signal demodulator capable of performing the demodulation of a cartier chrominance signal in plural broadcast systems and made of a small scale circuit. CONSTITUTION:The demodulation of the carrier chrominance signal of multi- system can be performed by providing a frequency converter 12 which multiplies an output signal from an oscillator in accordance with each frequency by an inputted carrier chrominance signal and outputs the carrier chrominance signal of frequency of the sum or difference of two frequencies, a selection circuit 16 which outputs by selecting the inputted carrier chrominance signal or the output signal of the frequency converter 12, and a carrier chrominance signal circuit of required minimum system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-system carrier color signal demodulator capable of demodulating a plurality of carrier color signals into color difference signals or color signals.

[0002]

2. Description of the Related Art The frequency of a typical carrier color signal is mainly NT.
There are two types, a 3.58 MHz system used in the SC system and a 4.43 MHz system mainly used in the PAL system. In recent years, multi-carrier carrier color signals are converted into color difference signals or RGB signals by a video display device such as a television compatible with both systems, a magnetic recording / reproducing device having a video display function, a system conversion device for converting a television broadcasting system. 2. Description of the Related Art A multi-system color demodulation device that converts a signal (hereinafter, this conversion is referred to as demodulation) is used. An example of a multi-system carrier color signal demodulation device used in the above-described conventional magnetic recording / reproducing device with a multi-system video display function will be described with reference to the drawings.

FIG. 2 shows a conventional PAL, 3.58 NTSC,
FIG. 3 is a block diagram showing a carrier color signal demodulation device supporting each system of 4.43 NTSC, M-PAL, and N-PAL. In FIG. 2, 21 is 4.43 MHz BPF, 211 is its input, 212 is its output, 22 is 3.58 MHz BPF,
221 is its input, 222 is its output, 23 is a PAL color signal demodulation circuit, 231 is its input, 232, 233 is its output, 24 is a 4.43NTSC color signal demodulation circuit, 24
1 is its input, 242, 243 its output, 25 is 3.
58NTSC color signal demodulation circuit, 251 is its input, 25
2, 253 is its output, 26 is an M-PAL color signal demodulation circuit, 261 is its input, 262, 263 is its output, 2
7 is an N-PAL color signal demodulation circuit, 271 is its input, 2
72 and 273 are outputs thereof, 28 is a selection circuit for selecting an output from each color signal demodulation circuit, 281 to 28A are inputs thereof, 28B and 28C are outputs thereof, and 29 is a matrix for generating RGB signals from color difference signals and luminance signals. Circuit, 29
1 to 293 are its inputs, and 294 to 296 are its outputs.

The operation of the multi-system carrier color signal demodulating device configured as described above will be described below. First, the input video signal is the BPF 21 or 22.
Thus, the carrier color signal is extracted and output to 212 and 222. The carrier color signals are 231, 241, 251,
The signals 261 and 271 are input to the carrier color signal demodulation circuits of 23, 24, 25, 26 and 27 systems. Each system carrier color signal demodulation circuit has a pair of outputs 232, 233, 242.
243,252,253,262,263,272,2
Only one carrier color signal demodulation circuit outputs the RY color difference signal and the BY color difference signal to each of 73, but outputs the regular color difference signal. That is, when the input video signal is PAL, the output 23 of the PAL color signal demodulation circuit 23
If 2,233 is 3.58 NTSC, then 3.58N
Only the outputs 252 and 253 of the TSC color signal demodulation circuit 25 are regular color difference signals. Each carrier color signal demodulation circuit output is 2
The color difference signals are input to the selection circuit 28 from 81 to 28A, and the normal color difference signals are selected and output from 28B and 28C.

[0005]

However, the above-mentioned conventional structure has a problem that the circuit scale is large and the cost is increased because a dedicated carrier color signal demodulating circuit is required for each system. Was there.

The present invention solves the above-mentioned conventional problems by converting the carrier frequency of the carrier color signal in advance so that it can be processed by the minimum carrier color signal demodulator circuit before the carrier color signal demodulator circuit. It is an object of the present invention to provide a multi-system carrier color signal demodulator in which the carrier color signal demodulator circuit is reduced in size to reduce costs.

[0007]

To achieve this object, a multi-system carrier color signal demodulator of the present invention comprises at least one oscillator having an oscillation frequency of f1 before a conventional carrier color signal demodulator circuit, A frequency converter that multiplies the output signal of the frequency f1 from the oscillator and the input carrier color signal and outputs the carrier color signal of the sum or difference frequency of the two frequencies, and the input carrier color signal or frequency. A carrier color frequency conversion circuit composed of a selection circuit for selecting and outputting the output signal of the converter is added.

[0008]

With this configuration, it is possible to demodulate multi-system carrier color signals only by providing a carrier color frequency conversion circuit of a minimum required system by converting the frequency of carrier color signals.

[0009]

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

FIG. 1 shows an embodiment of the present invention, which is 4.43.
2. NTSC and PAL carrier color signal demodulation circuits.
By adding a carrier color frequency conversion circuit from the 58 MHz system to the 4.43 MHz system, it is possible to further demodulate carrier color signals of 3.58 NTSC system, M-PAL system, and N-PAL system. It is a block diagram of a signal demodulation device. In FIG. 1, 11 is 3.58 BPF,
111 is its input, 112 is its output, 12 is a frequency conversion circuit, 121 is its input, 122 is its output, 13 is a 3.58 NTSC oscillator, 131 is its output, 14 is an M-PAL oscillator, and 14 is its output. Output, 15 is N-PA
L oscillator, 151 its output, 16 selection circuits 1, 1
61 and 162 are inputs thereof, 163 is an output thereof, 1B is a selection circuit 3, 1B1, 1B2 and 1B3 are inputs thereof, 1B4.
Is its output, 17 is 4.43 BPF, 171 is its input, 172 is its output, 18 is a PAL system carrier color signal demodulation circuit, 181 is its input, 182, 183 is its output, 19 is 4.43 NTSC system carrier color. Signal demodulation circuit,
191 is its input, 192, 193 is its output, 1A is the selection circuit 2, 1A1-14 are its input, 1A5, 1A6.
The output 1C is a matrix circuit for generating RGB signals from color difference signals and luminance signals, 1C1 to 1C3 are its inputs, and 1C4 to 1C6 are its outputs.

The operation of the multi-system carrier color signal demodulation circuit configured as described above will be described with reference to FIG.
First, when a carrier color signal (hereinafter simply referred to as a color signal) input to 111 and 162 is 3.58 NTSC, it is first input to the input 121 of the frequency conversion circuit 12 from the signal 112 through the 3.58 BPF 11. ..

On the other hand, as the fixed oscillator for frequency conversion, the 3.58 NTSC oscillator 13 is selected by the selection circuit 31 and is input to the input 122 of the frequency conversion circuit 12 from 314. The oscillation frequency of the 3.58 NTSC oscillator 13 is 854074 Hz (4433) which is the difference in carrier color frequency.
619-3579545). Then, the 3.58 NTSC signal input from 121 by the frequency conversion circuit 12 is converted into a 4.43 NTSC signal and output to 123. Next, the input of 161 is selected by the selection circuit 16 and output to 163.

Next, when the color signal input to 111, 162 is M-PAL, the oscillator selected by the selection circuit 31 is the M-PAL oscillator 14 and its frequency is 858008 Hz. Except for the above, the input is exactly the same as when the input is 3.58 NTSC, and the output of the selection circuit 16 is a PAL-M whose color signal frequency is 4.43 MHz.
The signal is output.

Further, when the color signal input to 111 and 162 is N-PAL, the oscillator selected by the selection circuit 31 is the N-PAL oscillator 15 and its frequency is 851563 Hz. For example, a general PAL signal is output to the output of the selection circuit 16 exactly as described above.

When the color signals input to 111 and 162 are PAL signals or 4.43 NTSC signals, the selection circuit 16 selects 162 inputs.
The color signal of PAL, 4.43 NTSC is output to 3 as it is.

On the other hand, since the color signal output to 163 contains unnecessary frequency components of the sum of 121 and 122, the unnecessary frequency components of the sum are removed by the 4.43 BPF 17. As a result, the output of 172 is PAL,
4.43NTSC, 3.58NTSC, M-PAL, N
-Any PAL color signal is input, a PAL signal, a 4.43 NTSC signal, or a 4.43 MHz MP
The AL signal will be output. Where 4.43 MH
The difference between the M-PAL signal and the PAL signal of z is
Since the horizontal synchronizing frequency and the vertical synchronizing frequency are different, the color signal demodulating circuit in the next stage can be demodulated by the same circuit, that is, the PAL color signal demodulating circuit. That is, the PAL color signal demodulation circuit 18 and 4.43N are used as the color signal demodulator.
The TSC demodulation circuit 19 can demodulate all signals. The PAL demodulated RY color difference signal and the BY color difference signal are output to the outputs of 182 and 183, and the NTSC demodulated RY color difference signal and the BY color difference signal are output to 192 and 193. The four outputs are 301, 302, 303,
It is input to the selection circuit 30 from the input of 304. The output of 172 is PAL signal 4.43MH by the selection circuit 30.
In the case of the M-PAL signal of z, the inputs of 301 and 302 are output, and when the output of 172 is 4.43 NTSC, the inputs of 303 and 304 are output to 305 and 306, and are the inputs of 321 and 322 of the matrix circuit 32. Meanwhile, 323
A luminance signal is input to the input of the matrix input, and the matrix circuit 32 outputs the RGB signals to its outputs 324 to 326 from the three inputs.

As described above, according to this embodiment, at least 1 having the oscillation frequency of f1 is provided before the carrier color signal demodulation circuit.
Frequency converter for multiplying two oscillators, an output signal of frequency f1 from the oscillator and the input carrier color signal, and outputting a carrier color signal of a sum or difference frequency of the two frequencies, and an input carrier By adding a carrier color frequency conversion circuit composed of a selection circuit for selecting and outputting a color signal or an output signal of a frequency converter, PAL, 4.43NT
Color signal demodulation of SC, 3.58 NTSC, M-PAL and N-PAL is possible only with the PAL color signal demodulation circuit and the 4.43 NTSC demodulation circuit.

[0018]

As described above, according to the present invention, at least one oscillator having an oscillation frequency of f1 is provided in front of the carrier color signal demodulation circuit, and an output signal of the frequency f1 from the oscillator and an inputted carrier color signal. A carrier composed of a frequency converter that multiplies and outputs a carrier color signal of a sum or difference of two frequencies, and a selection circuit that selects and outputs an input carrier color signal or an output signal of the frequency converter. By providing the color frequency conversion circuit, it is possible to realize an excellent multi-system carrier color signal demodulation circuit that can easily demodulate color signals of a plurality of systems with a circuit scale and cost that are smaller than conventional ones.

[Brief description of drawings]

FIG. 1 is a block diagram of a multi-system carrier color signal demodulation circuit according to an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional multi-system carrier color signal demodulation circuit.

[Explanation of symbols]

 11 3.58 MHz BPF 12 Frequency conversion circuit 13 3.58 NTSC oscillator 14 M-PAL oscillator 15 N-PAL oscillator 16 Selection circuit 1 17 4.43 MHBPF 18 PAL color signal demodulation circuit 19 4.43 NTSC color signal demodulation circuit 1A selection Circuit 1B selection circuit

Claims (1)

[Claims] 1. A carrier color signal having a sum or difference frequency of two signals obtained by multiplying at least one oscillator having an oscillation frequency of f1 and an output signal of the frequency f1 from the oscillator and an inputted carrier color signal. And a carrier color frequency conversion circuit configured to select and output an inputted carrier color signal or an output signal of the frequency converter, and a carrier color signal of frequency f2 to a color difference signal or It is added to the input of a conventional carrier color signal demodulation circuit capable of demodulating R, G, B, etc. color signals, so that not only the carrier color signal of frequency f2 but also frequency f2 + f1 or frequency | f2-
A multi-system carrier color signal demodulation device characterized in that at least one carrier color signal of f1 | carrier color signals can be demodulated into color difference signals or R, G, B signals.