JPH08340489A - Conversion device for high frequency reception - Google Patents

Abstract

PURPOSE: To attain received picture quality of high sensitivity by improving the reception sensitivity even in an area (weak electric field area) where a TV signal level is low. CONSTITUTION: The TV signal is inputted from an external antenna to an antenna input terminal 1. With a control signal outputted from a voltage detector 21 which detects an RF.AGC voltage 20 varying with the level of the input signal, 1st and 2nd switch circuits are switched. In general, when the input level is low (weak electric field level), the 1st and 2nd switches 3 and 5 are connected to (a) sides and the output signal of the 1st switch 3 is inputted to the 2nd switch 5 through a high frequency amplifier 4. Further, when the level is high, the 1st and 2nd switches 3 and 5 are switched to (b)) sides and the output signal of the 1st switch 3 is inputted directly to the 2nd switch 5 through a signal path 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency receiving and converting device which is provided in a video tape recorder (hereinafter referred to as VTR) and is effective as a receiving front end means.

[0002]

2. Description of the Related Art An example of a conventional high frequency receiving and converting device will be described with reference to FIG.

FIG. 2 shows recording of a VTR and an antenna / tuner for receiving a conventional television (hereinafter referred to as TV) broadcast, a video / audio demodulation circuit for demodulating an intermediate frequency signal from the tuner into a baseband signal of video / audio. RF that converts the video and audio signals reproduced and output from the unit to high-frequency signals
It is a block diagram which shows an example of the high frequency receiving conversion device comprised from the modulator. In FIG. 2, 1 is an antenna input terminal to which a high frequency signal such as a TV broadcast signal is input from the antenna, 2 is an antenna output terminal, and this antenna output terminal 2 is connected to a television receiver (not shown) through a coaxial cable. It is connected. Also, RF
The high frequency modulated signal from the modulator 11 is output to the antenna output terminal 2 through the switch circuit 10 and connected to the television receiver via the coaxial cable. At this time, the high frequency signal output from the RF demodulator 11 is output by switching the switch circuit 10 by a control signal from the outside, that is, an antenna switching control signal. Reference numeral 9 denotes an antenna distributor, which distributes a high frequency signal from the antenna input terminal 1 to the tuner 14 and the antenna output terminal 2 through the switch circuit 10. An RF modulator 11 RF-modulates a video / audio signal from the recording unit of the VTR to a baseband video / audio signal obtained through a video / audio processing circuit to extract a high frequency signal, and switches the antenna input from the switching signal input terminal 7. The switch circuit 10 is switched by the control signal and is output to the antenna output terminal 2. Generally, domestic VTRs output signals of 1-channel or 2-channel video and audio carrier frequencies, which can be connected to a television receiver via a coaxial cable for reception. A switch circuit 10 switches a TV signal from the distributor 9 and a video / audio carrier frequency signal from the RF modulator 11 by an antenna switching control signal, which is generally switched by a transistor or a diode circuit. An antenna switching control terminal 7 is a control signal input terminal for outputting a TV signal from the antenna input terminal 1 or a high frequency signal from the RF modulator 11 to the antenna output terminal 2 as necessary. A tuner 14 receives and selects a TV signal and converts it into an intermediate frequency signal. Reference numeral 15 is an antenna tuner having an antenna section and a tuner section. Reference numeral 16 denotes a video / audio demodulation circuit that demodulates the selected video / audio intermediate wave number signal into a baseband signal.
Reference numeral 17 is a video output terminal for outputting the demodulated base band video signal to a recording / reproducing means (not shown). 18
Is an audio output terminal from which the demodulated baseband audio signal is extracted. The signals extracted from 17 and 18 are input to the video / audio signal processing circuit of the VTR.

[0004]

However, in the above-described conventional configuration, since the TV signal input from the antenna input terminal 1 is directly input to the distributor 9, in a region where the TV signal level is weak (weak electric field region). Since the reception sensitivity is poor, there is a problem that the TV reception image quality deteriorates.

The present invention solves the above-mentioned conventional problems, and provides a high-frequency receiving and converting apparatus which improves the receiving sensitivity even in a region where the TV signal level is weak (weak electric field region) and realizes a highly sensitive received image quality. The purpose is to do.

[0006]

In order to achieve this object, a high frequency receiving and converting device of the present invention is a high frequency receiving device built in a video tape recorder used by connecting to a television receiver. Connected to an antenna input terminal for inputting a television signal to be received at, a first switch for receiving a television signal from the antenna input terminal and switching to two output terminals, respectively, and one output terminal of the first switch High-frequency amplifier,
A second switch that is connected to the high-frequency amplifier and the other output terminal of the first switch and is switchable;
A distributor for distributing the television signal output from the switch, a third switch for switching and outputting one output signal of the distributor and the input signal from the recording / reproducing means of the video tape recorder, and the distributor. And a voltage detector for detecting the RF / AGC voltage of the video / audio demodulation circuit and controlling to switch the first and second switches. Be prepared.

[0007]

According to the above means, a switch circuit, an amplifier and the like are provided in the preceding stage of the distributor of the antenna tuner section, and a high frequency signal from the antenna input is provided with a signal path and a switch circuit through the switch circuit, the amplifier circuit and the switch circuit. It is possible to configure an amplifier circuit section having a signal path that does not pass through the amplifier circuit through and to automatically switch the signal path of the amplifier circuit section by a control signal corresponding to the RF / AGC voltage of the video / audio demodulation circuit section. With the configuration
Even in an area where the signal level is weak (weak electric field area), the reception sensitivity can be improved and a high-sensitivity reception image quality can be realized.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a high frequency receiving and converting apparatus of this embodiment. In FIG. 1, the same components as those of the conventional technique are designated by the same reference numerals and the description thereof will be omitted. 3 is a first switch circuit connected to the output of the antenna input terminal 1, 4 is a high frequency amplifier for amplifying the signal output from the first switch circuit 3, and 5 is the output signal of the high frequency amplifier 4 or the first switch. A second switch for switching the output signal of 3 and a signal path 6 for connecting the output of the first switch circuit 3 to the second switch circuit 5. Two
0 is an RF / AGC voltage generated in the video / audio demodulation circuit section 16 and is a voltage that changes in accordance with the electric field strength of the TV signal input to the antenna input terminal 1. 21 is RF
It is a voltage detector that detects the AGC voltage 20 and outputs a LOW or HIGH control signal. This voltage detector 21
Is composed of a comparator circuit, but is not limited to this. The first switch circuit 3 is switched by a control signal output from the voltage detector 21. Reference numeral 8 is a high-frequency amplifier circuit section including the first switch circuit 3, the second switch circuit 5, the high-frequency amplifier 4, and the signal path 6.

The operation of the high-frequency amplifier circuit section 8 of the present invention constructed as above will be described below.

First, a TV signal is input from the external antenna to the antenna input terminal 1. The first and second switch circuits are switched by the control signal output from the voltage detector 21 that detects the RF / AGC voltage 20 that changes according to the level of the input signal. Generally, when the input level is low (weak electric field level), the first and second
Switches 3 and 5 are connected to the a side, and the first switch 3
Output signal of the second switch 5 via the high frequency amplifier 4.
Is input to When the input level is high, the first and second switches 3 and 5 are switched to the b side, and the output signal of the first switch 3 is directly input to the second switch 5 via the signal path 6. It

Next, the TV signal is distributed to the tuner 1 by the distributor 1.
4 and the antenna switch 10. The tuner 14 receives and selects a desired signal, converts it into an intermediate frequency signal, and inputs it to the video / audio demodulation circuit 16. The intermediate frequency signal input to the video / audio demodulation circuit 16 is demodulated to a baseband video / audio signal and transmitted to the video / audio signal processing means (not shown) of the VTR via the video signal terminal 17 and the audio signal terminal 18. To be done. The other TV signal from the distributor 9 is input to the antenna switch circuit 10. When the antenna switch circuit 10 is connected to the a side, it is output from the antenna output terminal 2 and transmitted to the TV receiver via the coaxial cable.

When the video / audio signal reproduced by the VTR is input to the TV receiver, the antenna switch 10 is connected to the side b, and the video input terminal 12 and the audio input terminal 13 are connected.
The video and audio signals input to and are the RF modulator 1
1 is output from the antenna output terminal 2 to the TV receiver via the coaxial cable.

As described above, according to this embodiment, the RF / AGC voltage in the video / audio demodulation circuit 16 is detected by the voltage detector 2.
1 to generate a control signal, and the first and second signals are generated according to the strength of the TV signal level input to the antenna input terminal 1.
The switch circuit is switched.

[0015]

As described above, according to the present invention, the first and second switch circuits, the high frequency amplifier and the like are provided in the preceding stage of the distributor of the antenna tuner section, and the high frequency signal from the antenna input is supplied to the first switch circuit and the high frequency signal. An amplifier circuit section having a signal path passing through the amplifier and the second switch circuit and a signal path not passing through the high frequency amplifier through the first and second switch circuits is configured, and the signal path of the amplifier circuit section is a video / audio demodulation circuit. By making it possible to switch automatically by the control signal corresponding to the RF / AGC of the unit, the receiving sensitivity is improved even in the area where the TV signal level is weak (weak electric field area), and the high sensitivity with good distortion characteristics It is possible to realize the excellent received image quality of.

[Brief description of drawings]

FIG. 1 is a block diagram of a high frequency receiving and converting device according to an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional high frequency receiving and converting device.

[Explanation of symbols]

 1 Antenna Input Terminal 2 Antenna Output Terminal 3 First Switch Circuit 4 High Frequency Amplifier 5 Second Switch Circuit 6 Signal Path 9 Antenna Distributor 10 Antenna Switch Circuit 11 RF Modulator

Claims (1)

[Claims] 1. A high-frequency receiving device built into a video tape recorder used by connecting to a television receiver, comprising: an antenna input terminal for inputting a television signal received by an antenna; and a television from the antenna input terminal. A John signal is input to the two output terminals and can be switched to each of the two output terminals, a high frequency amplifier connected to one output terminal of the first switch, and the other of the high frequency amplifier and the first switch. A second switch that is connected to an output terminal and can be switched respectively, a distributor that distributes the television signal output from the second switch, one output signal of the distributor, and recording of a video tape recorder. A third switch for switching and outputting the input signal from the reproducing means, and the other output signal of the distributor. And a video and audio demodulation circuit for demodulating the video and audio signals,
A high-frequency reception conversion device, comprising: a voltage detector that detects an AGC voltage and controls to switch the first and second switches.