JPH08130692A - Booster for video signal and video signal receiver - Google Patents

Abstract

PURPOSE: To amplify the video signal at an amplification factor suitable for the electric field strength. CONSTITUTION: The booster applies to a television booster 2 connecting to a video signal receiver 3 provided with an output terminal 40 for an AGC signal representing a level of a video signal led to an antenna terminal 39. Then the amplification factor of an amplifier circuit 22 amplifying a video signal received by an antenna 1 and outputting the amplified video signal to the video signal receiver 3 changes with the AGC signal sent from the output terminal 40.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION
The present invention relates to a video signal booster in which the amplification factor of an amplifier circuit changes according to a GC signal, and a video signal receiving device that outputs an AGC signal indicating the signal level of a video signal guided to an antenna terminal to the outside.

[0002]

2. Description of the Related Art When using a television in an area where the radio wave from a broadcasting station is weak, such as in a mountain area, in order to compensate for the lack of the level of the video signal and to display an image with less noise,
So-called television boosters for video signals are used. In addition, this television booster is provided with a switch for changing the amplification factor in order to enable amplification that is optimum for the intensity of the video signal received by the antenna.

[0003]

However, when the above-mentioned television booster is used in an area where one station is located at a short distance and another station is located at a long distance, the receivable broadcasting stations are as follows. There was a problem. That is, the television booster is often attached to a position near the antenna, such as a column of the antenna, in order to avoid deterioration of the S / N ratio of weak radio waves. Therefore, since it possible to frequently change the setting of the amplification factor it becomes difficult, the switch configuration is fixed either in advance according to use conditions. As a result, when the amplification factor is set high, the level of the video signal guided to the television becomes excessive when receiving a short-distance broadcasting station. For this reason, saturation occurs in the amplifier circuit inside the television, the brightness of the image is inverted, and the screen is difficult to see. On the other hand, if the amplification factor is set low in order to match a short-distance broadcasting station, if a long-distance broadcasting station is received, the image will contain a lot of noise due to insufficient video signal levels, and the screen It was hard to see.

The present invention was devised to solve the above problems, and an object of the present invention is to change the amplification factor based on the AGC signal output from the video signal receiving device. Another object of the present invention is to provide a video signal booster capable of amplifying a video signal with an optimum amplification factor for each of a strong electric field radio wave and a weak electric field radio wave. Another object of the present invention is to provide a video signal receiver capable of optimizing the amplification factor of the video signal booster according to the signal level by sending the AGC signal to the video signal booster. Especially.

[0005]

In order to solve the above-mentioned problems, a video signal booster according to a first aspect of the present invention is an AGC that indicates a signal level of a video signal guided to an antenna terminal.
It is applied to a video signal booster connected to a video signal receiving device provided with a signal output terminal, amplifies the video signal received by the antenna, and outputs the amplified video signal to the video signal receiving device. The amplification factor of the amplification circuit is changed according to the AGC signal sent from the output terminal. In the video signal receiving device according to the present invention, the amplification factor of the amplification circuit for amplifying the video signal received by the antenna and transmitting the amplified video signal to the outside is an AGC signal given from the outside. An output for applying to a video signal receiving device to which a video signal booster that changes in accordance with the above is connected, and for outputting to the outside an AGC signal indicating the signal level of the video signal output from the video signal booster and guided to the antenna terminal. The terminal is provided.

[0006]

The operation of the invention according to claim 1 will be described below. The video signal amplified by the video signal booster is sent to the antenna terminal of the video signal receiving device. Further, an AGC signal indicating the signal level of the video signal guided to the antenna terminal is transmitted from the output terminal of the video signal receiving device. That is, the AGC signal indicates the signal level of the video signal output from the video signal booster, and equivalently indicates the signal level of the video signal guided to the video signal booster. Therefore, the video signal booster amplifies the video signal with a small amplification factor when the signal level of the video signal received by the antenna is strong. When the signal level of the video signal received by the antenna is weak, the video signal is amplified with a large amplification factor. That is, the video signal booster amplifies the video signal at an amplification rate that is optimum for the strength of the guided video signal.

The operation of the invention according to claim 2 will be described below.
The video signal received by the antenna is amplified by the video signal booster. Further, the video signal receiving device outputs the AGC signal from the output terminal to indicate the signal level of the video signal amplified by the video signal booster.
That is, the AGC signal sent to the output terminal indicates the signal level of the video signal output from the video signal booster,
Equivalently, the signal level of the video signal guided to the video signal booster is shown. Therefore, the video signal booster amplifies the video signal with a small amplification factor when the signal level of the video signal received by the antenna is strong. When the signal level of the video signal received by the antenna is weak, the video signal is amplified with a large amplification factor. That is, the video signal booster amplifies the video signal at an amplification rate that is optimum for the strength of the guided video signal.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an electrical configuration of an embodiment of a so-called television booster for video signals and a video signal receiving apparatus according to the present invention.

In the figure, an antenna 1 is composed of a combination of two types of antennas, an antenna for the VHF band and an antenna for the UHF band, or one of the two types of antennas. Then, the received video signal is output to the input terminal 21 of the television booster 2.

The television booster 2 is a small-sized waterproof device, and is a block attached to a position near the antenna 1, such as a pillar to which the antenna 1 is attached. The amplification circuit 22 and the AGC are used. And an amplifier circuit 23. Then, the video signal received by the antenna 1 and guided to the input terminal 21 is amplified with an optimized amplification factor. The amplified video signal is output to the output terminal 24.
Send to.

More specifically, the AGC amplifier circuit 23 is a block for amplifying the AGC signal guided to the input terminal 25, and outputs the amplified AGC signal to the amplifier circuit 22. In the amplifier circuit 22, the TV booster 2 is UH.
In the case of a model dedicated to the F band, it is composed of an amplifier circuit for the UHF band, and in the case of a model for both the UHF band and VHF band, it is composed of an amplifier circuit for the UHF band and an amplifier circuit for the VHF band. Then, the video signal guided to the input terminal 21 is amplified with an amplification factor according to the level of the AGC signal output from the AGC amplifier circuit 23, and the amplified video signal is output to the output terminal 24.

The video signal receiving device 3, which is specifically a television, includes a tuner 31, a VIF amplifier circuit 32,
Signal processing circuit 33, CRT 34, RF AGC amplifier circuit 3
5, output amplification circuit 36, AGC detection circuit 37, and A
In the case of including the GC amplifier circuit 38 and omitting the output amplifier circuit 36 and the output terminal 40, the television is known as a prior art.

The tuner 31 is a block that amplifies and frequency-converts a video signal of a channel designated by a control unit (not shown) in the video signal guided to the antenna terminal 39. The intermediate frequency signal generated by is output to the VIF amplifier circuit 32.
The VIF amplifier circuit 32 is a block that amplifies the intermediate frequency signal generated in the tuner 31, and the like.
The amplified intermediate frequency signal is output to the signal processing circuit 33.
The signal processing circuit 33 is a block that performs video detection of the amplified intermediate frequency signal, signal processing such as separation of a luminance signal and color signal, and generation of a synchronization signal. The processed signal and the generated synchronization signal Then, the CRT 34 is driven.

The AGC detection circuit 37 has an antenna terminal 39.
In order to show the signal level of the video signal guided to, the AGC signal is a block based on the level of the synchronizing signal in the video signal. Then, the generated AGC signal is output to the AGC amplifier circuit 38. AGC amplifier circuit 38
Is a block for amplifying the AGC signal generated by the AGC detection circuit 37, and controls the amplification factor of the VIF amplification circuit 32 with the amplified AGC signal. Further, the amplified AGC signal is output to the RF AGC amplifier circuit 35 and the output amplifier circuit 36.

The RF AGC amplifier circuit 35 is a block for amplifying the AGC signal supplied from the AGC amplifier circuit 38, and the tuner 3 is supplied with the amplified AGC signal.
Control the amplification factor of 1. The output amplifier circuit 36 is a block that amplifies the AGC signal supplied from the AGC amplifier circuit 38 and converts the output impedance of the amplified AGC signal into a low impedance by using an emitter follower. A converted to low impedance
The GC signal is output to the output terminal 40.

The television booster 2 and the video signal receiving device 3 are connected to each other by a connection cable having a sectional structure in which one signal line is added to a 75Ω coaxial cable. That is, the output terminal 24 and the antenna terminal 39 are connected by the coaxial cable, and the output terminal 40 and the input terminal 25 are connected by the added signal line. Further, the television booster 2 operates by electric power supplied from a dedicated power source, but the dedicated power source has a circuit configuration known as a prior art, and therefore is not shown.

The operation of the embodiment having the above structure will be described below. The video signal received by the antenna 1 is
It is given to the amplifier circuit 22 via the input terminal 21. The video signal amplified by the amplifier circuit 22 is guided to the tuner 31 via the output terminal 24, the coaxial cable, and the antenna terminal 39. Tuner 31, VIF amplifier circuit 3
2, each of the signal processing circuit 33 and the AGC detection circuit 37 performs a predetermined process on the guided signal. As a result, the output of the AGC detection circuit 37 is connected to the antenna terminal 3
An AGC signal indicating the signal level of the video signal guided to 9 appears. At this time, the AGC amplifier circuit 38 to which the output of the AGC detector circuit 37 is guided sets the amplification factor of the VIF amplifier circuit 32 to an optimum value. Further, the RF AGC amplifier circuit 35 to which the output of the AGC amplifier circuit 38 is given sets the amplification factor of the RF amplifier circuit in the tuner 31 to an optimum value.

The AGC signal amplified by the AGC amplifier circuit 38 is amplified by the output amplifier circuit 36,
Converted to low impedance signal. The AGC signal converted to low impedance is output to the output terminal 40, the signal line,
It is given to the AGC amplifier circuit 23 via the input terminal 25. Therefore, the AGC amplifier circuit 23 is
The C signal is amplified, and the amplification factor of the amplifier circuit 22 is controlled by the amplified AGC signal.

That is, when the signal level of the video signal received by the antenna 1 is strong, it indicates that the AGC signal sent from the output amplification circuit 36 has a high signal level. Therefore, the AGC amplifier circuit 23 controls so that the amplification factor of the amplifier circuit 22 becomes small. As a result, the amplifier circuit 22 amplifies the guided video signal with a small amplification factor and sends the amplified video signal to the output terminal 24. When the signal level of the video signal received by the antenna 1 is weak, it indicates that the AGC signal sent from the output amplification circuit 36 has a low signal level. Therefore, the AGC amplifier circuit 23 controls so that the amplification factor of the amplifier circuit 22 increases. As a result, the amplifier circuit 22 amplifies the guided video signal with a large amplification factor, and sends the amplified video signal to the output terminal 24.

That is, the amplifier circuit 22 amplifies the video signal with an amplification factor which is optimum for the strength of the video signal received by the antenna 1. Therefore, when a radio wave from a short-distance broadcasting station and a strong electric field strength is received, the amplification factor of the amplifier circuit 22 becomes small, and the signal level of the video signal guided to the tuner 31 is not excessive. It is limited to the range that does not become. As a result, it is possible to obtain a clear image on the CRT with no brightness reversal or the like even though it is received by a short-distance broadcasting station.
34 is displayed. In addition, when a radio wave from a long-distance broadcasting station and a weak electric field strength is received, the amplifier circuit 2
The amplification factor of 2 increases, and the video signal guided to the tuner 31 has a sufficient signal level. As a result, a clear image with little image noise is displayed on the CRT 34 even though a long-distance broadcasting station is being received.

[0021]

The video signal booster according to the invention described in claim 1 is an image connected to a video signal receiving device provided with an output terminal for an AGC signal indicating the signal level of the video signal guided to the antenna terminal. It is applied to signal boosters. Then, the video signal received by the antenna is amplified, and the amplification factor of the amplifier circuit that outputs the amplified video signal to the video signal receiving device is changed according to the AGC signal sent from the output terminal of the video signal receiving device. There is. Therefore, when the signal level of the video signal received by the antenna is strong, the video signal is amplified with a small amplification factor, and when the signal level is weak, the video signal is amplified with a large amplification factor. It is possible to amplify a video signal with an optimum amplification factor for each of a radio wave and a weak electric field.

According to a second aspect of the present invention, the video signal receiving apparatus amplifies the video signal received by the antenna, and the amplification factor of the amplifier circuit for sending the amplified video signal to the outside is given from the outside. It is applied to a video signal receiving device connected to a video signal booster that changes according to an AGC signal. And output from the video signal booster,
A indicating the signal level of the video signal guided to the antenna terminal
An output terminal for sending the GC signal to the outside is provided. Therefore, the video signal booster amplifies the video signal with a small amplification factor when the signal level of the video signal received by the antenna is strong and with a large amplification factor when the signal level is weak. It is possible to optimize the amplification factor of the video signal booster.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of an embodiment of a video signal booster and a video signal receiving apparatus according to the present invention.

[Explanation of symbols]

 1 Antenna 2 Television Booster 3 Video Signal Receiving Device 22 Amplifying Circuit 23 AGC Amplifying Circuit 25 AGC Signal Input Terminal 36 Output Amplifying Circuit 37 AGC Detection Circuit 38 AGC Amplifying Circuit 39 Antenna Terminal 40 AGC Signal Output Terminal

Claims (2)

[Claims] 1. A video signal booster connected to a video signal receiving device provided with an AGC signal output terminal for indicating a signal level of a video signal guided to an antenna terminal, the video received by an antenna. The amplification factor of an amplifier circuit that amplifies a signal and outputs the amplified video signal to the video signal receiving device is output from the output terminal by the AGC.
A video signal booster characterized by being changed according to a signal. 2. A video signal booster for amplifying a video signal received by an antenna, and an amplification circuit for transmitting the amplified video signal to the outside, the amplification factor of which changes according to an AGC signal given from the outside is connected. A video signal receiving device according to claim 1, further comprising an output terminal for outputting an AGC signal output from the video signal booster and indicating the signal level of the video signal guided to an antenna terminal to the outside. Signal receiving device.