JPS61206325A - Television receiver - Google Patents

Abstract

PURPOSE:To improve the video color sensitivity even at a medium/weak electric field district with simple constitution by incorporating an antenna terminal board and a booster and using a switching circuit so as to switch a TV signal inputted from an antenna only at medium/weak electric field thereby activating the booster for amplification. CONSTITUTION:A broad band high frequency amplifier 4 is inserted between an antenna 1 and a tuner 7, the amplifier 4 is provided in the antenna terminal board of a TV receiver and a switching circuit 5 and a mode switching circuit 6 are used to operator or inoperate the amplifier 4. That is, the mode switching circuit 6 is brought into the on-mode at medium/weak electric field and the circuit 5 brings the amplifier 4 into the operating state so as to amplify the broadcast signal, which is fed to the turner 7. On the other hand, the circuit 6 is brought into the off mode at a strong electric field, the circuit 5 stops the operation of the amplifier 4 and connects directly the antenna 1 and the turner 7. Thus, a picture with high quality is displayed in each electric field.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a high frequency amplification device for a television receiver.

BACKGROUND OF THE INVENTION Generally, in areas with weak electric fields, even if the antenna installation point is selected and a high-performance antenna is used, sufficient image quality may still not be obtained. In addition, even if the input electric field of the antenna is sufficient for building joint reception, if the distance from the antenna to the television receiver is long or the number of television receivers increases, the attenuation due to the line will increase as the distance from the main line increases. The input level of the television receiver drops and snow noise appears on the screen.

As a measure to improve this, conventionally, as shown in Fig. 4, a high frequency amplifier 4 (hereinafter referred to as a booster) is inserted between the antenna 1 and the splitter 11 to increase the video and color sensitivity and produce high quality images. However, if the booster is not used properly (the location where the booster is installed), it may actually worsen the S/N ratio and deteriorate the image quality.

Additionally, because all-channel boosters (wideband boosters) are extremely expensive, most households in areas with medium to weak electric fields do not have boosters installed.

Problems to be Solved by the Invention As described above, conventional boosters have problems in that the S/N ratio deteriorates depending on the location where they are installed, and because they are expensive, they are not widely used in households outside of specific areas.

The present invention solves these conventional problems, and by integrating with a television receiver with a simple configuration, it can improve video and color sensitivity and receive high-quality images even in areas with medium and weak electric fields. The purpose of this invention is to provide a receiver that can perform the following functions.

Means for Solving the Problems In the present invention, the antenna terminal board and the booster are integrated, and the television broadcast signal input from the antenna is switched by a switching circuit only when the electric field is medium or weak, and the booster is operated to amplify it. The signal is then supplied to the tuner.

Operation With the above configuration, for example, when a television broadcast signal has a weak electric field, the switching circuit becomes the booster side, and the booster operates to amplify the input signal and supply a high-quality signal to the subsequent circuits. On the other hand, when there is a strong electric field (for example, when there is an extreme level difference between input channels), the switching circuit becomes the through side, the booster stops operating, and the input signal from the antenna is supplied to the tuner as is.

EXAMPLE An example of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 2 is a block diagram of a television receiver in one embodiment of the present invention. In FIG. 2, a broadband high frequency amplification device 4 is provided between the antenna 1 and the tuner 7.
and this high frequency amplification device 4 is installed in the antenna terminal board 2 of the television receiver, and the high frequency amplification device 4 is inserted using the switching circuit 5 and the mode switching circuit 6.
or disconnect the high frequency amplifier 4 from the signal supply path from the antenna 1 to the tuner 7 and directly apply the television broadcast signal from the antenna 1 to the tuner 7 without passing through the high frequency amplifier 4. In other words, when the electric field is medium or weak, the mode switching circuit 6 is set to the on mode, and the switching circuit 5 outputs the high frequency amplifier 4.
By activating the television broadcast signal from the antenna 1, the high frequency amplification device 4 on the antenna terminal 3
The signal is amplified and applied to the tuner 7.

On the other hand, in the case of a strong electric field, the mode switching circuit 6 is set to off mode, the switching circuit 5 stops the operation of the high frequency amplifier 4, and the high frequency amplifier 4 is switched off from the signal supply path from the antenna 1 to the tuner 7. Detach antenna 1
and tuner 7 are directly connected.

In this way, the high frequency amplifier 4 is installed on the antenna terminal board 2 in the television receiver, and the mode switching circuit 6 switches the operating state to control the level of the television broadcast signal from the antenna 1. It is possible to obtain a good signal in an electric field of , and to project a high-quality image.

FIG. 1 shows a concrete example of the main parts of this circuit. In the high frequency amplifier 4, Ql is an amplification transistor, C5 is a coupling capacitor, C6 and L2 are impedance conversion capacitors and coils, R1 and R2 are transistor pace bias resistors, 9 is a neutralization capacitor, R4 and C8 are the high-frequency compensation resistor and capacitor, the L3 harmonic link coil, and the C9 harmonic coupling capacitor.

In the switching circuit 5, D1 to D4 are switching diodes, C11 is a coupling capacitor, and RR
HANO (Ias resistance, L4'``5'' 14 and L6.C
12, L7. C13 is a filter that prevents high frequency components from being transmitted to the mode switching circuit 6.

Further, in the mode switching circuit 6, 6a is a mode switching switch whose common terminal is connected to a 10B power source. 01
~C3,Ll are a capacitor and coil for lightning protection.

For example, if the mode changeover switch 6a is set to the ON terminal side, a voltage of 10B is applied to the bias resistors R2 and R3, and the booster circuit 4 is activated. As a result, the television broadcast signal from the antenna 1 is amplified by the booster circuit 2, passes through the coupling capacitor C1, and is output. At this time, D
2. D4 has a voltage of 10B at L4. are biased and conductive from L5, while D1. D3 is reverse biased and in cutoff. If the electric field is weak and the image quality is poor, press the mode switch 1 above. All you have to do is flip Chiro a to the on-side terminal as described above.

On the other hand, in a strong electric field, the signal may be input directly from the antenna 1 to the tuner 7 without passing through the booster circuit 2. Therefore, at this time, the mode changeover switch 6a is turned to the OFF terminal. This causes the diode DD to go from 10B to L.
6. I, 7 conducts, and diodes D2. D
4 is reverse biased and enters the cutoff state, booster circuit 2 stops operating, and the signal from antenna 1 is changed from C4→
It is output along the path D1-+D11→D3→D1° and is applied to the tuner 7.

With the above configuration, when the mode selector switch 6a is used to operate the booster circuit 2 to amplify the television broadcast signal and supply it to the tuner 7 when the electric field is medium or weak, images with excellent image quality can be produced in any electric field. It becomes possible to obtain.

FIG. 3 shows an example of the characteristics of the booster circuit 2. The horizontal axis shows the frequency and the vertical axis shows the gain. Characteristic A is booster circuit 2.
It shows the gain of the signal input to the tuner 7 without going through the signal, and by inserting the booster circuit 2, the gain is improved as shown in characteristic B. Effects of the Invention As described above, according to the present invention, the high frequency amplification device By installing it at the antenna terminal inside the television receiver and configuring it to amplify the television broadcast signal and supply it to the tuner, signal loss is reduced not only in strong electric fields but also in medium and weak electric fields. It is possible to obtain high-quality images with little noise.

[Brief explanation of the drawing]

Fig. 1 is a specific circuit diagram of the main parts of a television receiver according to an embodiment of the present invention, Fig. 2 is a block diagram of a television receiver according to an embodiment of the present invention, and Fig. 3 is its characteristics. 4 are professional diagrams of a television receiver for a conventional public listening system. 2...Antenna terminal board, 4...Broadband high frequency amplifier, 6...Switching circuit, 6...
...Mode switching circuit. Name of agent: Patent attorney Toshio Nakao and one other person - Aoi A? ζ

Claims (1)

[Claims] A high-frequency amplification device for broadband amplifying the television broadcast signal is installed in the antenna terminal board of the television receiver, and the high-frequency amplification device is operated to amplify the television broadcast signal before supplying it to the tuner. 1. A television receiver comprising: a switching circuit for switching between stopping the operation of the high frequency amplifier and supplying the television broadcast signal to the tuner without amplifying the television broadcast signal.