JPS5911314B2 - color television receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color television receiver that receives color television signals of two or more different systems, such as PAL system and SECAM system. To provide a device which can improve the performance of color synchronization or color erasure by 10 degrees and improve the performance of line discrimination or color erasure by improving the part for extracting reference signals of different color television signal systems. The purpose is to

First, FIG. 1 shows a schematic diagram of the signal waveforms of the horizontal back porch portion of the PAL signal and the SECAM signal.

15 Same figure A (7) Burst signal 1 in PAL signal
is inserted between the horizontal synchronizing pulse 2 and the color video signal 3 including the luminance signal and the carrier color signal, as shown.

Further, in the SECAM signal B (7) in the figure, a line discrimination signal 4 is inserted between the horizontal synchronizing pulse 2 and the color 20-video signal 3 as shown. That is, the burst signal 1 of the PAL signal is superimposed with a 4.43 MH2 sine wave during the TA time, and the line discrimination signal 4 of the SECAM signal is superimposed with a 4.25 MH2 (B-Y line) or 254 MH2 sine wave during the Tl time. A sine wave of .40MH2 (RY line) is superimposed. Hereinafter, the burst signal 1 in the PAL signal and the line discrimination signal 4 in the SECAM signal will be collectively referred to as a reference signal. Next, PAL/SEC
An example of a conventional main part block diagram of a circuit for extracting and processing a burst signal 1 in a PAL signal and a line discrimination signal 4 in a SECAM signal in a color television receiver capable of receiving both AM and AM signals is shown below. Shown in Figure 2.

In FIG. 2, PAL burst signal 1 or 35 is S
PAL signal including ECAM line discrimination signal 4 and SE
The carrier color signal of the CAM signal is inputted from a signal line 5 to a chroma amplifier 6, where it is suitably amplified and processed by 10 degrees, and then applied from a line 7 to a reference signal extraction circuit 8.

Then, the PAL burst signal 1 or S included in the carrier color signal is controlled by the gate pulse supplied from the line 9.
The ECAM line discrimination signal 4 is extracted, and a carrier color signal not containing these signals is sent from the line 10 to the color demodulation stage, while the burst signal 1 or the component of the line discrimination signal 4 is extracted from the line 12. This extracted reference signal is sent to the line discrimination circuit 13 for the SECAM method.
It is determined whether it is the line discrimination signal 4 of the ECAM system or the burst signal 1 of the PAL system, and the SEC
In the case of AM system signals, it is a line sequential transmission system, so B
It is determined whether the line is the Y line or the R-Y line, and the generation of switching pulses is controlled.

That is, the discrimination voltage is supplied to the flip-flop circuit 15 driven by the horizontal pulse applied from the line 14,
Further, a determination voltage depending on whether the SECAM system is the PAL system is supplied to a switching drive circuit 16 for switching the system according to the received signal. Although not shown in the figure, the operation of the PAL signal processing and SECAM signal processing circuits is switched by the output signal of the system switching drive circuit 16. The reference signal output from the burst extraction circuit 8 to the line 12 is also supplied to the subcarrier generation circuit 17 and the ACC/killer voltage generation circuit 18, and as is known in the art, the R-
Subcarriers for Y and B-Y demodulation are generated and ACC
A voltage or a bright voltage for color erasing is generated. The gate pulse supplied from the line 9 is a pulse that matches the time position to extract the reference signal superimposed on the back porch following the horizontal synchronizing signal 2 shown in FIG. Similarly, in the case of SECAM signals, the pulse width of the gate pulse is preferably exactly T as shown in FIG.
It is desirable that the pulse width be B time.

However, in conventional circuits, a gate pulse with a constant pulse width is used for both types, so if the width is wider than the TA time.

If so, a large amount of extra noise components will be extracted from the PAL signal, resulting in an increase in the dynamic phase error of the reproduced subcarrier and inaccuracy in the focusing operation.
On the other hand, if the pulse width is set to about the TA time so that it is suitable for extracting the burst signal 1 of the PAL signal, the latter part of the line discrimination signal 4 will be lost when the SECAM signal is used, and the signal will be removed from the medium/weak electric field signal. This may result in malfunctions such as color fading. The present invention provides a device that eliminates these inconveniences, and is a device that receives color television signals based on two or more types of systems such as PAL and SECAM, which can receive color television signals according to the format of the received signal. In conjunction with the system switching means that switches the color demodulation circuit etc., the pulse width of the gate pulse width is also switched to extract a reference signal such as a burst signal of a PAL signal or a line discrimination signal of a SECAM signal. This is a characteristic feature.

Hereinafter, FIG. 3 shows a circuit diagram of an embodiment of the present invention, and FIG. 4 shows waveform diagrams of various parts thereof.

In FIG. 3, a video-detected composite color television signal is applied from a line 19 to a bandpass circuit 20VC,
Here, the carrier color signal is extracted and supplied to the chroma amplifier 21. The composite color television signal supplied from the line 19 is also applied to a sync separation circuit 22, where the sync signal is extracted and supplied to the horizontal and vertical oscillator circuits, as well as to the inductance 2 via the capacitor 23.
41 fC is added. That is, as shown in FIG. 4, a horizontal synchronizing pulse such as C is extracted from a horizontal synchronizing signal portion of a PAL signal such as A or a SECAM signal such as B by a synchronization separation circuit 22, and is connected to a capacitor 23 and an inductance 24. By appropriately selecting , a differential waveform like D can be obtained.

The negative part is removed by diode 25, and only the positive part is taken out. And a suitable resistance 26
and an appropriate capacitance 27 including stray capacitance to create a slightly delayed triangular wave-shaped pulse as shown in E, and the transistor . Applied to the base on the 28th. One end of a suitable resistor 29 is connected to the base of the transistor 28, and the other end is connected to switching means of a system switching circuit 30.

Although this switching means is shown in the form of a mechanical switch for convenience of explanation, in reality it can easily be implemented with electronic switching means such as a transistor. This switching means 31 is connected to the contact A side when receiving PAL, and is connected to the contact B side when receiving SECAM. Therefore, due to such switching, the S
During ECAM reception, the base voltage of the transistor 28 is slightly higher and forward biased. Therefore, the resistor 26,
29, 32 and the value of the voltage v are appropriately selected, the transistor 28 becomes conductive at the level AffC when the PAL signal is received by switching the switching means 31 as shown in FIG. 4E, and the SECAM signal is received. Sometimes it can be set to conduct at level b.

As a result, when the PAL signal is received, the transistor 28 conducts at level a, so that a gate pulse having a pulse width approximately equal to TA for the PAL signal is obtained at the collector of the transistor 28, as shown in F in FIG. On the other hand, SECA
When receiving the M signal, the transistor 28 conducts at level b, so that a gate pulse like G whose pulse width is approximately equal to TB for the SECAM signal is obtained. Those Q
Each of the gate pulses is supplied to a reference signal extraction circuit 34 via a line 33, and in either method, only the reference signal portion is accurately extracted without excess or deficiency. As described above, in this device, the pulse width of the gate pulse for extracting the reference signal is switched according to the received signal format, so that the burst signal 1 and line discrimination signal 4 are used even when receiving a PAL signal and when receiving a SECAM signal. The time width can be switched and extracted according to the respective durations TA and TB. Therefore, even when receiving both types of signals at medium or weak electric field strengths, it is possible to reproduce color tones, or switch between color and black and white signals, and even when receiving signals of both types. Line discrimination etc. is more stable and correct than before.
It is something that can be done.

In the embodiment shown in FIG. 3, negative polarity simultaneous pulses, NP
Although the case where an N transistor and a bias voltage of +V are used is shown, it goes without saying that the same implementation can be performed using a positive polarity synchronizing pulse, a PNP transistor, or a voltage higher than +V.

It goes without saying that the present invention can also be applied to the reception of both NTSC and SECAM signals.

[Brief explanation of the drawing]

Figure 1 is a waveform diagram centered on the horizontal back porch of PAL and SECAM color television signals, and Figure 2 is a chroma diagram of a conventional color television receiver that receives both PAL and SECAM signals. FIG. 3 is a block diagram of the main part of the chroma circuit of a color television receiver according to an embodiment of the present invention, and FIG. 4 is a waveform diagram of each part of the apparatus. 20...band pass circuit, 21...chroma amplifier, 22...synchronous separation circuit, 23...
...Capacitor, 24...Inductance,
25...Diode, 26...Resistor,
21... Capacitor, 28... Transistor, 29, 32... Resistor, 30... System switching means, 31... Switching means, 3
4...Reference signal extraction circuit.

Claims (1)

[Scope of Claims] 1. A processing circuit that processes and demodulates received color television signals of two or more different formats, and a processing circuit that processes and demodulates received color television signals of two or more different formats, and a processing circuit that processes and demodulates received color television signals of two or more different formats; a reference signal extraction circuit that extracts the inserted reference signal; a gate pulse generation circuit that supplies the reference signal extraction circuit with a gate pulse for extracting the reference signal; and a gate pulse generation circuit that discriminates the extracted reference signal and receives the reference signal. a switching circuit that discriminates the format of the color television signal received and switches the processing circuit to a receiving state of the format based on the discrimination output, and controls the gate pulse generation circuit based on the discrimination output from the switching circuit. A color television receiver characterized in that the pulse width of the gate pulse is switched to be approximately equal to the time width of a reference signal of the received color television signal. 2. As a gate pulse generation circuit, use a circuit that differentiates the horizontal synchronizing pulse, integrates the differential output a little to generate a triangular wave-shaped pulse, controls switching of the transistor by this pulse, and generates a gate pulse, and applies it to the above transistor. 2. A color television receiver according to claim 1, wherein the pulse width of the gate pulse is changed by switching the bias voltage according to a discrimination output of a switching circuit.