JP2000353995A - Diversity device for mobile television and signal receiving method for mobile television - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diversity device for a mobile television and a signal receiving method for the mobile television for always obtaining a satisfactory receiving state across a wide area ranging from the area in which a means electric field is strong to the area in which the mean electric field is weak. SOLUTION: When electric field levels of video signals in plural antennas 1A-1D set at the different positions of a traveling object are a prescribed level or more, the switching of the antenna is operated in the electric field level of a video, and when the electric field levels of the video signals in the antennas are the prescribed level or less, the switching of the antennas is operated in the electric field level of a voice by diversity antenna selecting circuits 5 and 10. Thus, it is possible to receive a signal by selecting the antenna whose receiving state is the most satisfactory across a wide area ranging from the area in which a mean electric field is strong to the area in which a mean electric field is weak.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diversity apparatus for a mobile television and a signal reception method for a mobile television. More specifically, a diversity apparatus for a mobile television that automatically switches a plurality of antennas installed at different positions of a mobile body such as a car, a bus, and a train according to a reception state to obtain the best radio wave reception state. And a method for receiving a signal for a mobile television.

[0002]

2. Description of the Related Art A mobile television mounted on a mobile body such as an automobile, a bus, or a train has a problem that a radio wave is obstructed by a building or the like when moving, and the reception state of the radio wave is difficult to stabilize. Therefore, today, as a radio receiver system for mobile TV, multiple antennas are installed at different positions on the mobile body, the multiple antennas receive radio waves, and the antennas received in the best condition among them are received. Many use a diversity antenna system that preferentially takes in radio signals.

FIG. 2 shows the configuration of a conventional diversity apparatus for mobile television. In FIG. 2, reference numeral 1 denotes a plurality (four in this example) of antennas 1A, 1B, 1C, and 1 installed at different positions on a vehicle body of an automobile (moving body).
D is a diversity antenna. Reference numeral 2 denotes an antenna changeover switch for selecting 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 switch 2. Reference numeral 4 denotes a video detection circuit that detects the intermediate frequency signal amplified and frequency-converted by the high-frequency tuner 3 and outputs a video signal.
Is the video detection output. Reference numeral 5 denotes a video diversity antenna selection circuit that outputs a switching signal to the antenna switching switch 2. Reference numeral 6 denotes a phase locked loop for tuning and selecting the high frequency tuner 3 to the same channel. Reference numeral 7 denotes an audio detection circuit that detects the intermediate frequency signal amplified and frequency-converted by the high-frequency tuner 3 and outputs an audio signal. Reference numeral 9 denotes an audio detection output.

Next, the operation of the above-mentioned conventional diversity apparatus for mobile television will be described. In this device, a high-frequency signal received by the currently selected antenna (1A to 1D) enters the high-frequency tuner 3. In the high frequency tuner 3, the same channel is tuned and selected by the phase locked loop 6. The tuned and selected high-frequency signal is amplified and frequency-converted by the high-frequency tuner 3 to become an intermediate frequency signal, which is input to the video detection circuit 4 and the audio detection circuit 7, respectively. The video detection circuit 4 demodulates the video signal into a video signal and outputs it as a video detection output 8. A part of the demodulated signal is input to the diversity antenna selection circuit 5. The audio detection circuit 7 demodulates the audio signal into an audio signal and outputs it as an audio detection output 9.
The diversity antenna selection circuit 5, to which the video detection output 8 has been input, sends an antenna switching signal to the antenna switching switch 2 during the vertical retrace period of the video signal, and switches to another antenna (1A to 1D) one after another. Then, the electric field level of the image of each antenna (1A to 1D) is compared, and a signal for switching the antenna is sent to the antenna changeover switch 2 so as to switch to the antenna having the highest electric field level of the image. To enjoy stable broadcast reception.

As described above, even in the above-described conventional mobile television diversity apparatus, it is possible to select an antenna (1A to 1D) having a good reception state according to the reception state and obtain a good reception state.

[0006]

However, the above-mentioned conventional diversity apparatus for a mobile television has a problem that an antenna level cannot be correctly selected in a region of a weak electric field where a video signal cannot be detected.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has a diversity apparatus for a mobile television and a mobile television capable of always obtaining a good reception state over a wide area from an area having a strong average electric field to an area having a weak average electric field. It is an object of the present invention to provide a method of receiving a signal for use.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a method for displaying an image when an electric field level of a video signal received by a plurality of antennas installed at different positions of a moving body is higher than a predetermined level. A diversity antenna selection circuit that switches antennas at the electric field level of 、, and switches the antenna at the electric field level of voice in the following cases, selects and receives the antenna with the best reception condition from the area with the strong average electric field to the area with the weak average electric field It is something that can be done.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention provides an antenna changeover switch which receives signals with a plurality of antennas installed at different positions of a moving body and switches the antennas according to the signal state. In the mobile television diversity device having the first means for controlling the antenna changeover switch by comparing the electric field level of the video received by each antenna and comparing the electric field level of the audio received by each antenna. A second means for controlling the antenna changeover switch, wherein a changeover control for switching the antenna changeover switch from the first means to the second means when the electric field level of the image is not at a predetermined electric field level Means for mobile television, characterized in that the area where the average electric field is strong is The antenna changeover switch is controlled by using the electric field level of the antenna, and the antenna changeover switch can be controlled by using the electric field level of the voice signal in a weak area, and the reception state is best from the area having the strong average electric field to the area having the weak electric field. This has the effect that an antenna can be selected and received.

According to a second aspect of the present invention, there is provided an image diversity antenna selection circuit in which the first means compares an electric field level of an image of each antenna and outputs a switching signal to the antenna switch. The second means is formed by an audio diversity antenna selection circuit for comparing the electric field level of the sound of each antenna and outputting a switching signal to the antenna changeover switch, and the switching means is provided by the video diversity antenna selection circuit. 2. The diversity apparatus for a mobile television according to claim 1, wherein an antenna having the best reception state can be selected and received from an area having a strong average electric field to an area having a weak average electric field.

According to a third aspect of the present invention, there is provided a mobile unit having an antenna changeover switch for receiving signals with a plurality of antennas installed at different positions of the mobile unit and switching the antenna in accordance with a reception state. In the television signal receiving method, when the electric field level of the image of each antenna is equal to or higher than a predetermined level, the antenna is switched according to the electric field level of the image. When the electric field level is equal to or lower than the predetermined level, the antenna is switched according to the electric field level of audio. And a method for receiving a signal for a mobile television, characterized in that an antenna having the best reception condition can be always selected and received from an area where the average electric field is strong to an area where the average electric field is weak.

(Embodiment) A diversity apparatus for a mobile television according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an example of the configuration of a mobile television 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 numeral 1 denotes an automobile (mobile).
(Four in this example) installed at different positions on the vehicle body
Of antennas 1A, 1B, 1C and 1D. Reference numeral 2 denotes an antenna changeover switch for selecting 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 switch 2. Reference numeral 4 denotes a video detection circuit that detects the intermediate frequency signal amplified and frequency-converted by the high-frequency tuner 3 and outputs a video signal. Reference numeral 8 denotes a video detection output. Reference numeral 5 denotes a video diversity antenna selection circuit that outputs a switching signal to the antenna switching switch 2. Reference numeral 6 denotes a phase locked loop for tuning and selecting the high frequency tuner 3 to the same channel. Reference numeral 7 denotes an audio detection circuit that detects the intermediate frequency signal amplified and frequency-converted by the high-frequency tuner 3 and outputs an audio signal. Reference numeral 9 denotes an audio detection output. 1
Reference numeral 0 denotes a voice diversity antenna selection circuit that outputs a switching signal to the antenna switching switch 2.

Next, the operation of the diversity apparatus for mobile television according to the embodiment of the present invention will be described.
In this device, the currently selected antenna (1A to 1A) is used.
The high frequency signal received in D) enters the high frequency tuner 3.
In the high frequency tuner 3, the same channel is tuned and selected by the phase locked loop 6. The tuned and selected high-frequency signal is amplified and frequency-converted by the high-frequency tuner 3 to become an intermediate frequency signal, which is input to the video detection circuit 4 and the audio detection circuit 7, respectively. The video detection circuit 4 demodulates the video signal into a video signal and outputs it as a video detection output 8. A part of the demodulated signal is input to the video diversity antenna selection circuit 5. The audio detection circuit 7 demodulates the signal into an audio signal and outputs it as an audio detection output 9, and a part of the output is input to an audio diversity antenna selection circuit 10.

Here, when the video diversity antenna selection circuit 5 determines that the input video detection output 9 is at a level higher than a predetermined electric field level (average electric field level), As in the case of the above-described conventional device, an antenna switching signal is sent to the antenna switching switch 2 during the vertical blanking period of the video signal, and the antenna switching signal is sequentially switched to the other antennas (1A to 1D). Then, the electric field levels of the images of the antennas (1A to 1D) are compared, and the antenna is switched to the antenna having the highest electric field level of the image.
To secure.

On the other hand, if it is determined that the video signal is at a level lower than the level of the average electric field, the switching control of the antenna switch 2 is switched from the video diversity antenna selection circuit 5 to the audio diversity antenna selection circuit 10. . The audio diversity antenna selection circuit 10 sends an antenna switching signal to the antenna switching switch 2 in the same manner as the diversity antenna switching method of the FM receiver. Then, the antenna switching switch 2 is used to sequentially switch to another antenna (1A to 1D). The voice diversity antenna selection circuit 10 compares the electric field level of the sound of each antenna (1A to 1D), sends an antenna switching signal to the antenna switch 2 so as to switch to the antenna having the highest electric field level of the sound, and receives the best radio wave. Secure the antennas (1A to 1D) in the state. After that, when the video signal becomes stronger than the level of the average electric field, the switching control of the antenna switch 2 is switched from the audio diversity antenna selection circuit 10 to the video diversity antenna selection circuit 5 again.

Therefore, in the diversity apparatus for a mobile television according to the present embodiment, the antenna diversity switch 2 is controlled by the video diversity antenna selection circuit 5 in an area where the average electric field is strong, and the audio diversity antenna is selected in an area where the average electric field is weak. The antenna 10 having the best reception state can be easily secured by switching control of the antenna changeover switch 2 by the circuit 10. Thereby, the reception state of the radio wave is stabilized.

[0018]

As described above, according to the present invention, it is possible to easily secure the antenna having the best reception state from the region where the average electric field is strong to the region where the average electric field is weak.
The reception state of radio waves is always stable, and the image quality can be improved.

[Brief description of the drawings]

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Diversity antenna 2 Antenna change-over switch 3 High frequency tuner 4 Video detection circuit 5 Video diversity antenna selection circuit 6 Phase locked loop 7 Audio detection circuit 8 Video detection output 9 Audio detection output 10 Audio diversity antenna selection circuit

Claims (3)

[Claims] 1. A mobile television diversity apparatus having an antenna changeover switch for receiving a signal with a plurality of antennas installed at different positions of a moving body and switching the antenna in accordance with a signal state. A first means for comparing the electric field level of a received image and controlling the antenna changeover switch; and a second means for comparing the electric field level of audio received by each antenna and controlling the antenna changeover switch. A diversity unit for a mobile television, comprising: switching means for switching the control of the antenna changeover switch from the first means to the second means when the electric field level of the image is not at a predetermined electric field level. apparatus. 2. The image diversity antenna selection circuit according to claim 1, wherein said first means compares an electric field level of an image of each of said antennas and outputs a switching signal to said antenna changeover switch. The video diversity antenna selection circuit is formed by an audio diversity antenna selection circuit that compares an electric field level of audio and outputs a switching signal to the antenna selection switch, and the switching unit is provided in the video diversity antenna selection circuit. 1
The diversity device for a mobile television according to the above. 3. A mobile television signal receiving method comprising: receiving signals by a plurality of antennas installed at different positions of a moving object, and having an antenna changeover switch for switching the antenna according to a reception state; When the electric field level of the image is equal to or higher than a predetermined level, the antenna is switched according to the electric field level of the image. When the electric field level is equal to or lower than the predetermined level, the antenna is switched according to the electric field level of the audio. Signal receiving method for mobile television.