JPS6133755Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a television receiver that handles PAL television signals, and in particular separates two color difference signals from a carrier color signal that constitutes the PAL television signal. The present invention relates to a signal processing device for demodulating.

In recent years, with the spread of magnetic reproducing devices such as VTR video discs, the number of television receivers of this type that receives reproduction signals from magnetic reproducing devices and receives images is increasing. However, some of the above-mentioned magnetic playback devices are capable of converting the frequency of the chroma subcarrier of an NTSC television signal into PAL.
There are some that transmit pseudo-NTSC television signals converted to the same format as the playback signal.
Even in conventional television receivers of this type, it has become necessary to receive television signals of the pseudo-NTSC system.

The present invention was proposed in view of these points, and it is a pseudo
It is also capable of receiving NTSC television signals. Hereinafter, the present invention will be explained based on the accompanying drawings.

In the figure, Tin is the terminal to which the carrier color signal CS is supplied, which is connected to the changeover switch circuit via the adder AD.
SW and is also connected to a changeover switch circuit SW via a subtracter SUB. Further, the terminal Tin is connected to an adder AD and a subtracter SUB via a delay line DL. The connection point between the adder AD and the changeover switch circuit SW is the first detector DT ₁
is connected to the AND gate G through the subtractor
The connection point between SUB and changeover switch circuit SW is the second
is connected to the AND gate G via the detector _DT2 . AND gate G is a changeover switch circuit
SW, and the changeover switch circuit SW is connected to the first
is connected to the demodulator DMI and the second demodulator
Connected to DM ₂ .

Next, the operation will be explained. Terminal Tin, PAL
When a carrier color signal based on the television signal of the formula is supplied, as shown in FIG. 2, the addition output cd ₁ obtained by the sum of the carrier color signal CS and the delayed color signal ds is
(B-Y) indicates the first color difference signal. This addition output CD ₁ is the changeover switch circuit SW
will be sent to. Further, the subtraction output cd ₂ obtained from the difference between the carrier color signal CS and the delayed color signal ds is -2(R-
Y) indicates the second color signal. This subtraction output
CD ₂ is also sent to the changeover switch circuit SW. In addition, the delay line DL adder AD and subtractor SUB
is a separation circuit that separates two color difference signals, first and second, from the carrier color signal CS when it receives the carrier color signal CS based on a PAL television signal.
It can be seen that it constitutes SE.

Now, in the present invention, the addition output cd ₁ and the subtraction output cd ₂ are sent to the first and second detectors DT ₁ and DT ₂ , respectively. At this time, the first detector DT ₁ detects the addition output cd ₁ , and when the addition output cd ₁ indicates the first color signal, a DC signal dc ₁ having the first DC level is generated.
is now output. Also a second detector
DT ₂ detects the subtracted output cd ₂ , and the subtracted output cd ₂ is the second
A DC signal _dc2 having a second DC level is output when a color difference signal of .

Both of these DC signals dc ₁ and dc ₂ are applied to an AND gate G. AND gate G is both DC signals
A switching control signal is sent to the changeover switch circuit SW in response to application of dc ₁ and dc ₂ having the above-mentioned first and second DC levels, respectively. The changeover switch circuit SW receives the addition output CD ₁ and the subtraction output CD ₂ , and in response to the switching signal ch, the addition output CD ₁ indicates the first color difference signal and the subtraction output CD ₂ indicates the second color difference signal. When indicating these two color difference signals (for example, R-Y, B
-Y) are directly sent to corresponding first and second demodulators DM1 and DM2, respectively, where each color difference signal is demodulated.

On the other hand, when a carrier color signal based on a pseudo-NTSC television signal, which is obtained by converting the chroma subcarrier frequency of an NTSC television signal to the same as that of the PAL system, is applied to terminal Tin, as shown in Figure 3, , the addition output cd ₁ obtained by the sum of the carrier color signal CS and the delayed color signal ds is 2(R-Y)+2
(B-Y), and this color difference signal [(R-Y)+
(B-Y)] is sent to the changeover switch circuit SW, but the subtraction output cd ₂ obtained from the difference between the carrier color signal CS and the delayed color signal ds becomes zero, and this subtraction output O becomes It will not be sent to the changeover switch circuit SW. On the other hand, the addition output cd ₁ [(B-
Y)+(R-Y)] will transmit the first DC signal dc ₁ to the AND gate G via the first detector DT ₁ , so from the gate G, the switching No control signals are sent. At this time, the changeover switch circuit SW adds the addition output and the subtraction output (actually supplies the addition output to the subtraction output supply line) and branches it to the first and second demodulators DM1 and DM.
Give to 2. First and second demodulators DM1, DM
2 separates and demodulates the color difference signals handled by each.

The changeover switch circuit SW is configured, for example, as shown in the figure. Switch SW1 of switch circuit SW
In the case of PAL system, on one side of the switching signal Ch,
It is switched to the contact P side, and the addition output cd ₁ is directly sent to the first demodulation circuit DM1, and the subtraction output cd ₂ is sent directly to the second demodulation circuit DM2 via the contact P and switch SW1. In addition, switch SW1 of the switch circuit SW is a switching signal in the case of pseudo NTSC system.
The other side of Ch is switched to the contact N side, and the addition output cd ₁ is sent to the first demodulation circuit DM1, and is also sent to the second demodulation circuit DM2 via the switch SW1.
It is also branched and sent to.

As explained above, according to the present invention, by simply making improvements to a television receiver that handles PAL television signals, pseudo-NTSC signals can be output from VTR video discs, etc. as playback output.
It is convenient because it can also receive standard television signals.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram showing an embodiment of the present invention, and FIGS. 2 and 3 are diagrams explaining the same embodiment. CS: carrier color signal, SE: separation circuit, CD ₁ : addition output, CD ₂ : subtraction output, DT ₁ : first detector,
DT ₂ : Second detector, dc ₁ : DC signal, dc ₂ : DC signal, G: (AND) gate, ch: switching control signal, SW: changeover switch circuit, RY, B
-Y: Color difference signal, DM1: First demodulator, DM
2: Second demodulator.

Claims (1)

[Scope of utility model registration request] Receive PAL television signals and use this PAL
The carrier color signal is separated from the television signal of the system, and this is combined with the separated original carrier color signal.
A television receiver that extracts a signal delayed by a horizontal period, adds these two signals to obtain an added output indicating a first color difference signal, and subtracts both signals to obtain a subtracted output indicating a second color difference signal. a first detection means for detecting the addition output and extracting a DC signal having a first DC level when the addition output indicates the first color signal;
a second detection means for detecting the subtraction output and extracting a DC signal having a second DC level when the subtraction output indicates the second color difference signal; Both DC signals are applied, and at this time, the two DC signals are respectively applied to the first
a gate means for extracting a predetermined control output in response to a second DC level; a first demodulator for demodulating the first color difference signal; and a second demodulator for demodulating the second color difference signal. a demodulator, which provides the addition output to the first demodulator when the control signal is applied and provides the subtraction output to the second demodulator, and provides the addition output when the control signal is not applied. A signal processing device comprising: signal supply means for providing the first demodulator and the second demodulator.