JPS6024631B2 - signal mixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is for superimposing and displaying other information, such as characters and graphics, on the cathode ray tube (hereinafter referred to as CRT) surface of a color television receiver while receiving broadcast waves. The present invention provides a signal mixing device that can efficiently mix information to be superimposed and a broadcast wave video signal in a signal processing system.

Conventionally, as means for mixing two types of signals, the methods shown in Figs.
A circuit like the one shown in the figure is widely used. First, in FIG. 1, a broadcast wave video signal (
A digital information signal (hereinafter referred to as a video signal) to be superimposed on the base of the transistor 4 is inputted to the base of the transistor 4, and an output signal that is a mixture of both signals is obtained from the output terminal 9. be. That is, a digital signal input to the transistor 4 turns on the transistor 3, and turns off the transistor 8 via the inverter 7. Therefore, the video signal is grounded via the resistor 2, and the output terminal 9 has a resistor 5 and a transistor 6.
Only digital signals are output via the . On the other hand, when there is no digital signal input, transistor 3 is turned off and transistor 8 is turned on, and only the video signal is output to output terminal 9. Therefore, the output signal of output terminal 9 is a video signal with a digital signal superimposed on it. Thus, the two signals are mixed.

In addition, in FIG. 2, each base 10, 1 of the differential amplifier
A video signal and a digital signal are respectively input to 1, and the peak voltage Vsp of the video signal and the peak voltage Vd of the digital signal are input.
By setting p so that Vsp<Vdp, an output signal in which a digital signal is combined with a video signal is obtained from the emitter side 12.

However, when these conventionally used signal mixing devices are used in each color signal circuit of a color television receiver, the one shown in FIG. 1 has a problem in that the number of elements constituting the mixing circuit increases.

In addition, ``The one in Figure 2 impairs the color purity on the CRT screen.In other words, even if the digital signal input is only ``red'', ``green'' is
, because the "blue" video signal circuit was operating, there was a problem that the color display was different from the original digital signal.The present invention solves these problems.
It is an object of the present invention to provide a signal mixing layer that can mix two types of signals without impairing the color purity with a small number of elements.

Hereinafter, the present invention will be explained with reference to the illustrated embodiments. FIG. 3 is a circuit configuration diagram of an embodiment of the present invention, and FIG. 4 is a waveform diagram showing the correlation between its operating states. First, in Figure 3, “
13, corners 4 and 15 are red, green, and blue color signal input terminals, respectively; 16 is a first analog switch group inserted in the middle of each color signal transmission path;
18 and 19. 25, 26, and 27 are input devices for red, green, and blue digitized color signals, respectively; 28 is a second analog switch group inserted in the middle of each digitized color signal transmission path; It is composed of switches 29, 30, and 31.

33 is a 3-input NOR gate circuit which receives the digital color signals from the input terminals 25, 26, and 27; 34 is the NOR gate circuit;
an inverter 35 for inverting the polarity of the output signal of the gate 33;
is driven by the inverter output signal and the control signal of the control input terminal 37, and controls the control input terminal 20 of the first analog switch group 16;
This is an AND gate circuit that is driven by the same input signal as the AND gate circuit 35 and controls the control input terminal 32 of the second analog switch group 28 .

A in FIG. 4 is a color signal waveform input to one of the input terminals of the color signal input devices 13, 14, and 15, and B is a color signal waveform input to one of the input terminals 25, 26, and 27 of the digitized color signal. Digital signal waveform input to the input terminal of the same color as waveform A, C is the output waveform of the NOR gate circuit 33, D is the control input terminal 37
, E is the output waveform of the AND gate circuit 36, and F is the input waveform of the AND gate circuit 36.
1 and 2 respectively show output signal waveforms of analog switches to which waveform A is input.

In the embodiment shown in FIG. 3, the color signals "red", "green", and "blue" of television broadcast waves, VTR playback signals, etc. are 13 and 13, respectively.
14 and 15, and color signals such as characters and graphics are applied to input terminals 25, 26, and 27, respectively. The signals of the same color are short-circuited via the analog switch group 28, and each of the short-circuited signals is input to the amplifiers 22 and 23, respectively. It is displayed as follows.

That is, the color signal A in FIG. 4 is input to the input terminal 83, and the color signal B
When inputting color signals to the input terminals 25, NOR
The output of the gate circuit 33 becomes C in FIG.
The output of 4 becomes B in FIG.

Here, when the signal shown in FIG. 4D is input to the control input terminal 37, the output of the AND gate circuit 36 becomes E in FIG. Become. Therefore, the control signal applied to the control input terminal 201 of the first analog switch group 16 and the control signal applied to the control input terminal 32 of the second analog switch group 28 have opposite polarities, and the color signal input terminal 13 , 25 become a completely switched mixed signal (FIG. 4F) when viewed at the input of the amplifier 21. In addition, by configuring the circuit as shown in FIG. 3, the first analog switch group 16 is turned off for any of the color signal input terminals 25, 26, and 27 that are intended to be folded. C without compromising the color purity of the superimposed signal.
It can be displayed on the RT screen.

Next, the effects of the present invention will be explained more clearly with reference to specific examples.

A color television receiver having a circuit configuration as shown in FIG. 27, the positive logic character information synchronized with the synchronization signal of the broadcast wave is digitized and inputted.

When MCI4016 (manufactured by Motorola) is used as the switch groups 16 and 28, a collector type circuit is used as the AND gate circuit 36 and the NAND gate circuit 36, and a positive logic control signal is input to the control input terminal 37, when the broadcast It was confirmed that the signal mixing device shown in FIG. 3 operates efficiently, with text information being superimposed on the image created by the waves, and the color purity of the text information not being impaired. In addition, compared to the conventional method shown in FIGS. 1 and 2 in which the colors red, green, and blue are switched, there is an advantage that the number of prime numbers is reduced. As is clear from the above description, the present invention has two
The color signals of different signal sources are short-circuited through analog switches, and the signal from one signal source is used to mix the two signals by opening and closing each analog switch. This makes it possible to realize an efficient signal mixing device that does not impair color purity.

In addition, in the embodiment of the present invention, the terminals 25, 26,
Although the case where the input signal at terminal 27 and the control signal at terminal 37 are positive logic has been described, even when these signals are negative logic or a combination of positive and negative, this input signal can cause both analog switch groups to mutually connect. Needless to say, it is important to control the polarities in reverse so that when one is on, the other is off.

[Brief explanation of drawings]

1 and 2 are circuit configuration diagrams of a conventional signal mixing device, FIG. 3 is a circuit configuration diagram of an embodiment of the present invention, and FIG. 4A,
B, C, D, E, and F are signal waveform diagrams at each part in FIG. 3. 13, 14, 15, 25, 26, 27... Color signal input terminal, 16... First analog switch group, 20...
Control input terminals of the first analog switch group, 28...second
32... Control input terminal of the second analog switch group, 33... 3-input NOR gate circuit, 34... Inverter, 35... NAND gate circuit, 36... AND gate circuit, 37...Control input terminal. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1 A signal mixing device in a color television receiver that superimposes a color signal of a second signal source on a color signal of a first signal source and displays the result on a cathode ray tube surface, wherein the color signal of the first signal source is A first analog switch group provided in the middle of a signal transmission path, and two analog switch groups provided in the middle of a color signal transmission path of the second signal source, and the first analog switch a signal transmission means configured to short-circuit color signal outputs of the same color system of each of the analog switch group and the second analog switch group; and a three-input NOR gate circuit triggered by each color signal input of the second signal source. , an AN in which the output signal of the NOR gate circuit is input to one input terminal via an inverter, and the control signal is input to the other input terminal.
It has a D gate circuit and a NAND gate circuit driven by the same input as the AND gate circuit, and the output signal of the AND gate circuit is used as the drive signal for the second analog switch group, and the NAND gate using the output signal of the circuit as a drive signal for the first analog switch group;
A signal mixing device characterized in that the second analog switch group closes a circuit and the first analog switch group opens a circuit when each signal input of the second signal source is present.