JP2000341185A - Diversity system for mobile tv and signal receiving method for mobile tv - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an satisfactory mobile TV use diversity system that can ensure superior receiving state by suppressing deterioration or distortion of video and audio data even in an area with a strong electric field and to provide a mobile TV use signal receiving method. SOLUTION: A reception electric field state is discriminated, in response to an AGC voltage fed to a high frequency tuner 3 and a signal level detected by an audio detection circuit 7 and discriminated by a signal level detection circuit 10 that generates a DC voltage, and when the reception state indicates a strong electric field state, a power supply supplied to an antenna changeover 2 is turned off and a signal output is obtained by inter-board isolation, so as to suppress deterioration or distortion in video audio data, even in an area with a strong electric field strength thereby ensuring a satisfactory reception state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile TV such as a vehicle-mounted TV or a portable TV mounted on a vehicle such as a car, a bus or a train.
The present invention relates to a diversity apparatus for a mobile TV and a signal reception method for a mobile TV that automatically switches a plurality of antennas installed in a V according to a reception state.

[0002]

2. Description of the Related Art FIG. 2 shows the configuration of a conventional diversity apparatus for a mobile TV. In FIG.
A, 1B, 1C, and 1D are four antennas installed in the automobile. An antenna switching circuit 2 selects one of the signals received by the antennas 1A to 1D. Reference numeral 3 denotes a high-frequency tuner that receives a signal selected by the antenna switching circuit 2. Reference numeral 4 denotes a SAW filter for extracting a video carrier and an audio carrier from a signal amplified and frequency-converted by the high-frequency tuner 3. Reference numeral 5 denotes a video detection circuit for detecting a video carrier output from the SAW filter 4, and reference numeral 6 denotes a video detection output. Reference numeral 7 denotes an audio detection circuit for detecting an audio carrier output from the SAW filter 4, and reference numeral 8 denotes an audio detection output. Reference numeral 9 denotes a video signal comparison circuit that compares the levels of the video signals according to the video signal reception states of the antennas 1A to 1D, and 11 denotes an antenna switching control circuit that outputs a switching signal to the antenna switching circuit 2.

Next, the operation of the above conventional example will be described. In the mobile TV, the currently selected antenna (1A
1D) are converted into intermediate frequency signals by the high-frequency tuner 3, and then are divided into a video intermediate frequency signal (58.75 MHz) and an audio intermediate frequency signal (54.25 MHz) through the SAW filter 4. The intermediate frequency signal of the video signal is detected by a video detection circuit 5 and a video detection output 6 is output. The video signal comparing circuit 9 detects the level of the video signal during the vertical blanking period, and the antenna switching control circuit 11 sends a control signal to the antenna switching circuit 2 to switch to another antenna. On the other hand, the intermediate frequency signal of the audio signal is detected by an audio detection circuit 7 and an audio detection output 8 is output.

As described above, even in the above-mentioned conventional mobile TV diversity apparatus, an antenna having a good reception state can be selected according to the reception state, and a good reception state can be obtained.

[0005]

However, in the above-mentioned conventional mobile-to-TV diversity apparatus, antenna switching is performed under any electric field condition. For this reason, for example, in an area with a strong electric field, there is a problem in that the active elements constituting the antenna switching circuit and the high-frequency tuner are distorted, thereby deteriorating video and audio.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and is an excellent mobile TV capable of suppressing deterioration and distortion of video and audio and ensuring a good reception state even in a strong electric field area. It is an object of the present invention to provide a diversity device for use and a method for receiving a signal for a mobile TV.

[0007]

In order to achieve the above object, the present invention provides a signal level detection circuit for detecting an AGC voltage supplied to a high-frequency tuner and a signal level from an audio detection circuit to generate a DC voltage. In the strong electric field state, the power supply to the antenna switching circuit is turned off to obtain a signal output by board-to-board isolation. However, it is possible to suppress deterioration and distortion of video and audio and to ensure a good reception state.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention comprises a plurality of antennas installed in an automobile, an antenna switching circuit for selecting one of signals received by the plurality of antennas, A high-frequency tuner that receives a signal selected by the antenna switching circuit; a SAW filter that extracts a video carrier and an audio carrier from a signal amplified and frequency-converted by the high-frequency tuner;
A video detection circuit for detecting a video carrier output from the filter, a video signal comparison circuit for comparing the level of the video signal according to the video signal reception state of each antenna, and a voice carrier output from the SAW filter A sound level detection circuit for detecting a signal level from the sound level detection circuit to generate a DC voltage, and a DC voltage generated by the signal level detection circuit. An antenna switching control circuit that determines a reception state from an AGC voltage supplied to the high-frequency tuner, and when the reception state is a strong electric field state, turns off a power supply to the antenna switching circuit and obtains a signal output by isolation between boards. A diversity device for a mobile TV, comprising: In the case of an electric field state, the power supply to the antenna switching circuit is turned off, and a signal output is obtained by the inter-substrate isolation, so that deterioration and distortion of video and audio in a strong electric field area can be suppressed, and always good. This has the effect that a proper reception state can be ensured.

According to a second aspect of the present invention, there is provided a method for receiving a signal for a mobile TV having an antenna switching circuit for receiving a signal with a plurality of antennas installed in an automobile and switching an antenna according to a reception state. Detecting the level of the reception signal selected by the antenna switching circuit, determining the reception electric field state according to the signal level, and turning off the power supply to the antenna switching circuit when the reception state is a strong electric field state A signal receiving method for a mobile TV, characterized in that a signal output is obtained by inter-substrate isolation. When a receiving state is a strong electric field state, a power supply to an antenna switching circuit is turned off, Since the signal output is obtained by the isolation, the deterioration and distortion of the video and audio in the strong electric field area can be suppressed, and the good reception is always achieved. An effect that can be secured state.

(Embodiment) Hereinafter, a diversity apparatus for a mobile TV according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an example of the configuration of a mobile TV diversity apparatus according to the present embodiment. Components corresponding to those in FIG. 2 are denoted by the same reference numerals.

In FIG. 1, reference numerals 1A, 1B, 1C, 1
D is four antennas installed on the automobile. An antenna switching circuit 2 selects one of the signals received by the antennas 1A to 1D. Reference numeral 3 denotes a high-frequency tuner that receives a signal selected by the antenna switching circuit 2.
Reference numeral 4 denotes a SAW filter for extracting a video carrier and an audio carrier from a signal amplified and frequency-converted by the high-frequency tuner 3. Reference numeral 5 denotes a video detection circuit for detecting a video carrier output from the SAW filter 4, and reference numeral 6 denotes a video detection output. Reference numeral 7 denotes an audio detection circuit for detecting an audio carrier output from the SAW filter 4, and reference numeral 8 denotes an audio detection output. Reference numeral 9 denotes a video signal comparison circuit that compares the levels of the video signals according to the video signal reception states of the antennas 1A to 1D.
A signal level detection circuit that generates a DC voltage, and 11 is an antenna switching control circuit that outputs a switching signal to the antenna switching circuit 2. 12 is an antenna switching circuit 1
1 is a power supply circuit that supplies power to the power supply circuit 1.

Next, the operation will be described. In the configuration of the present embodiment, in the mobile TV, a signal from the currently selected antenna (1A to 1D) is transmitted to the high-frequency tuner 3.
Is converted to an intermediate frequency signal by the SAW filter 4
, A video intermediate frequency signal (58.75 MHz) and an audio intermediate frequency signal (54.25 MHz). The intermediate frequency signal of the video signal is detected by a video detection circuit 5 and a video detection output 6 is output. The video signal comparing circuit 9 detects the level of the video signal during the vertical blanking period, and the antenna switching control circuit 11 sends a control signal to the antenna switching circuit 2 to switch to another antenna.

On the other hand, the intermediate frequency signal of the audio signal is detected by an audio detection circuit 7 and an audio output 8 is output. At that time, the signal level detection circuit 10 generates a DC voltage corresponding to the signal level,
, The antenna switching control circuit 11 determines the reception electric field condition. When it is not in the strong electric field state, the antenna switching control circuit 11 can send a control signal to the antenna switching circuit 2 to switch to another antenna. On the other hand, in the case of a strong electric field, the power supply to the antenna switching circuit 2 is turned off, and a signal output is obtained by the isolation between the substrates. That is, in the case of the strong electric field state, since the power is not supplied, the gain (Ga
in) drops, and deterioration and distortion of video and audio can be suppressed even in a strong electric field area.

Therefore, in the diversity apparatus for a mobile TV according to the present embodiment, the power supply to the antenna switching circuit 2 is turned off in the case of a strong electric field state, and the switching is performed so as to obtain a signal output by the inter-substrate isolation. The gain is reduced, so that deterioration and distortion of video and audio can be suppressed even in a strong electric field area.

[0015]

According to the present invention, as is apparent from the above embodiment, in the case of a strong electric field, no power is supplied to the antenna switching circuit. There is an effect that deterioration and distortion can be suppressed.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram of a diversity apparatus for a mobile TV according to an embodiment of the present invention.

FIG. 2 is a configuration block diagram of a conventional mobile TV diversity apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1A antenna 1B antenna 1C antenna 1D antenna 2 antenna switching circuit 3 high-frequency tuner 4 SAW filter 5 video detection circuit 6 video detection output 7 audio detection circuit 8 audio detection output 9 video signal comparison circuit 10 signal level detection circuit 11 antenna switching control circuit 12 Power supply circuit

Claims (2)

[Claims] 1. A plurality of antennas installed on an automobile,
An antenna switching circuit for selecting one of the signals received by the plurality of antennas; a high-frequency tuner for receiving a signal selected by the antenna switching circuit; and a video carrier from a signal amplified and frequency-converted by the high-frequency tuner. A filter for filtering audio carriers, a video detection circuit for detecting a video carrier output from the filter, a video signal comparison circuit for comparing the level of a video signal according to the video signal reception state of each antenna, An audio detection circuit that detects an audio carrier output from a filter; a signal level detection circuit that detects a signal level from the audio detection circuit to generate a DC voltage; and the DC voltage generated by the signal level detection circuit, and The reception state is determined from the AGC voltage supplied to the high-frequency tuner. For state turns off the power supplied to the antenna switching circuit, mobile TV for diversity apparatus being characterized in that anda antenna switching control circuit to obtain a signal output by the inter-substrate isolation. 2. A signal receiving method for a mobile TV having an antenna switching circuit for receiving a signal with a plurality of antennas installed in a car and switching an antenna according to a reception state, the signal being selected by the antenna switching circuit. The level of the received signal is detected, the state of the received electric field is determined according to the signal level, and when the received state is the strong electric field state, the power supply to the antenna switching circuit is turned off, and the signal output is performed by the board-to-board isolation. A method for receiving a signal for a mobile TV, the method comprising: