JPH0228950B2 - TAHOSHIKITE REBIJONJUZOKI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a multi-system television receiver capable of receiving images in any of the NTSC, PAL, and SECAM broadcasting systems, and particularly to a comb-shaped filter circuit.

Conventional configurations and their problems In recent years, there has been a demand for multi-system television receivers that can receive images from any of the NTSC, PAL, and SECAM broadcasting systems. Also, on the other hand
The NTSC system uses a comb-shaped filter circuit that utilizes the frequency interleaving principle of color television waves to improve cross-color and resolution.

This will be explained below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a conventional multi-system television receiver. One of the video signals inputted here passes through a delay line 1 and a chroma trap circuit 5, where a luminance signal is taken out and supplied to a video control circuit 6.

On the other hand, this video signal is
Bandpass filter circuit 2 for PAL signals or bandpass filter circuit 3 for NTSC signals
through PAL or NTSC chroma demodulation circuit 7
supplied to

Furthermore, on the other side, it passes through a bell filter circuit 4 for SECAM signals, and then passes through a SECAM chroma demodulation circuit 8.
supplied to

The luminance signal that has passed through the video control circuit 6 and the chroma signal that has passed through the chroma demodulation circuit 7 or 8 depending on each system are mixed by the video amplifier circuit 9 and supplied to the CRT 10.

Furthermore, FIG. 2 is a circuit diagram of a conventional example of a comb-shaped filter circuit for a television receiver that can only receive images of the NTSC system.

Here, the input video signal passes through an impedance conversion transistor 11, and from its emitter, one signal is supplied from a capacitor 12 to the collectors of transistors 18 and 19 through a resistor 14 and a resistor 15. On the other hand, a resistor 26 and a capacitor 2 are connected to the emitter of the transistor 11.
The video signal applied to the 1H delay line 13 via the 1H delay line 13 is delayed by one horizontal scanning period, and is supplied to the bases of the transistors 18 and 19 in opposite phases to each other.

Therefore, a video signal containing only the chroma signal component is generated at the collector of the transistor 18 by mixing with the video signal supplied without delay.
It is added to the base of the impedance conversion transistor 25, and is supplied from its emitter to the NTSC bandpass filter circuit 3.

On the other hand, a video signal containing only a luminance signal component is generated at the collector of the transistor 19, and is applied to the base of the impedance conversion transistor 24, and is supplied to the delay line 1 from its emitter.

The comb filter circuit improves cross color and resolution when using the NTSC system. However, in the SECAM system, the chroma signal is FM-modulated, so even if the above circuit is used, it is theoretically impossible to separate the video signal into two video signals consisting only of the chrominance signal component and only the luminance signal component. Also
In the PAL system, the interleaved position is
Since it is different from the NTSC system, it is necessary to allow a longer delay time for the video signal to be mixed than the NTSC system. (Approximately 2 horizontal scanning periods) For this reason, in an image that includes a portion with rapid color changes, discontinuity in color information components becomes noticeable, resulting in a significant drawback in that the screen turns back and becomes difficult to view.

Purpose of the Invention The present invention allows the video signal to pass through a comb-shaped filter circuit in the case of the NTSC system, taking advantage of its advantages, and blocks the comb-shaped filter circuit in the case of the PAL and SECAM systems, thereby allowing the video signal to pass through the comb-shaped filter circuit. The object of the present invention is to provide a multi-system television receiver that can pass through as is.

Structure of the Invention A multi-system television receiver according to the present invention is provided by adding a video signal to each collector of a differential amplifier to which a video signal delayed by one horizontal scanning period and having different phases is applied to the base through a resistor. A comb filter circuit is constructed at each collector output terminal of the amplifier to take out a video signal containing only a luminance signal component and a video signal containing only a chroma signal component, and the emitters of the differential amplifiers are connected to each other via a resistor. In addition to connecting the point to ground through a diode, a switching circuit is installed at the base of the differential amplifier to operate as a differential amplifier in the case of the NTSC system, and to shut off the differential amplifier in the case of the PAL and SECAM systems. connected
This has the effect of maintaining conventional performance when using the PAL and SECAM systems, and improving cross color and resolution when using the NTSC system.

DESCRIPTION OF EMBODIMENTS A multi-system television receiver according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 3 shows a circuit diagram of a multi-system television receiver according to an embodiment of the present invention. In the figure, the same elements and circuits as in FIGS. 1 and 2 are given the same numbers.

Here, the diode 29 connects the anode to the resistor 1
The diode 28 has an anode connected to the resistor 23 and a cathode connected to the ground.

In the case of the NTSC system, a high level voltage is output from the system switching circuit 30, so the diode 29 is cut off, the differential amplification transistors 18 and 19 forming the comb filter circuit operate, and the impedance conversion transistor 24 is turned off. A video signal containing only the luminance signal component is supplied from the emitter of the other impedance conversion transistor 25, and a video signal containing only the chroma signal component is supplied from the emitter of the other impedance conversion transistor 25, and is guided to the NTSC bandpass filter circuit 3. .

On the other hand, in the case of the PAL or SECAM method, a low level voltage is output from the method switching circuit 30, so the diode 29 is turned on and the transistors 18 and 19 are cut off, so that the original signal input to the base of the transistor 11 is The same is supplied from the emitters of transistor 24 and transistor 25, from which transistor 24 supplies delay line 1 and chroma trap 5 of PAL and SECAM.
The brightness signal is transmitted through the transistor 25.
PAL bandpass filter circuit 2 or
It is supplied to SECAM bell filter circuit 4.

Note that the diode 28 is inserted so that the transistors 18 and 19 are completely cut off in the PAL and SECAM systems.

Effects of the Invention As described above, according to the present invention, when configuring a multi-system television receiver, PAL and
When using the SECAM system, the comb-shaped filter circuit is shut off and the video signal passes through as is, ensuring the original performance.When using the NTSC system, the comb-shaped filter circuit is operated, which has the effect of improving cross color and resolution. It is something.

[Brief explanation of drawings]

Figure 1 is a block diagram of a conventional multi-system television receiver, Figure 2 is a circuit diagram of a comb filter circuit of a conventional television receiver that can only receive images in the NTSC system, and Figure 3 is a circuit diagram of the present invention. 1 is a circuit diagram of a multi-system television receiver in one embodiment; FIG. 1... Delay line, 2... PAL band pass filter circuit, 3... NTSC band pass filter circuit, 4... SECAM bell filter circuit, 5...
Chroma trap circuit, 6... Video control circuit, 7
...PAL and NTSC chroma demodulation circuit, 8...
SECAM chroma demodulation circuit, 9...video amplifier circuit, 10...CRT, 11, 18, 19, 24,
25...Transistor, 12,27...Capacitor, 13...1H delay line, 14,15,
16, 17, 21, 22, 23...Resistance, 28,
29... Diode, 30... Method switching circuit.

Claims (1)

[Claims] 1. A differential amplifier is provided to each collector to which a video signal is applied via a resistor, and to a base to which a video signal delayed by one horizontal scanning period and whose phases differ by 180 degrees from the video signal is applied to the base. A comb-shaped filter circuit is configured such that a video signal containing only a luminance signal component and a video signal containing only a chroma signal component are taken out from each collector output terminal, and the emitters of the differential amplifiers are connected to each other via a resistor, This connection point is connected to ground via a diode, and the base of the differential amplifier is made to operate as a differential amplifier when using the NTSC system, and to cut off the differential amplifier when using the PAL and SECAM systems. A multi-system television receiver connected to a working switching circuit.