JPS5950602A - Antenna device - Google Patents

Abstract

PURPOSE:To prevent effectively fading, by providing a processor controlling the switching of each antenna and detecting the video and sound level in response to the number of antennas at this processor so as to select the best antenna by the sound and the video level. CONSTITUTION:Plural antenna elements 1 are arranged, any one of the elements 1 is selected with a high frequency switch 7 and the result is outputted to an output terminal 8. A tuner 2 is connected respectively to each element 1, an output of each tuner 2 is applied to a video detecting circuit 3 and a sound detecting circuit 11, and the level of a video signal and a sound signal detected at the circuits 3, 11 is detected respectively at level detecting circuit 4, 12. The output of the detecting circuits 4, 12 is applied to a discriminating processor 13, and a driving circuit 6 is controlled with a prescribed algorithm reserved in the processor 13. Further, the best antenna is selected by the video and sound level so as to prevent effectively the fading.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to an antenna system for preventing fading used in a vehicle-mounted television.

[Problems with the prior art] Images from a television receiver mounted on a moving object such as a car are
It depends on the electric field strength around the receiving antenna. In addition to direct waves, TV radio waves in cities are reflected and scattered by various structures, and the direct waves and reflected waves interfere with each other, and the electric field strength is strong in some places and weak in some places.

Conventionally, as a countermeasure against this problem, there is a diversity reception method. In this method, multiple antennas are installed at different locations, the input levels of each antenna are compared, and the antenna with the highest level is selected.

In the conventional diverging method, only the video output is used for level comparison. For example, as shown in Figure 1, there are multiple antennas (1) installed at different locations for diversity, a tuner (2) added to these antennas, a video detection circuit (3), a level detection circuit (4), and each antenna. It consists of a comparison circuit (5) for comparing input levels, and a drive circuit (6) for selecting one of the antennas by the comparison circuit and driving the high frequency switch (7).

Although this method uses the video signal output to evaluate antenna selection, the audio signal is outside the video signal band and is approximately 4 MHz above the video signal carrier. Generally, the strength of the electric field generated by an antenna has frequency characteristics, and is usually accompanied by so-called frequency selective fading.The wider the frequency band of the received radio waves, the more uneven the electric field strength within the frequency band.

Therefore, if diversity reception is performed based only on the above-mentioned video output, even if there is a drop in the level of the audio signal, it will not be known.

This results in audio disturbance.

[Object of the Invention] The present invention improves the drawbacks of the conventional device described above, and aims to provide a device that can receive good reception not only of television images but also of audio.

[Summary of the Invention] The present invention is characterized in that in addition to the determination based on video output, audio output is also determined.

[Effects of the Invention] According to the present invention, not only television images but also audio can be received in good condition, and the role of the television can be significantly improved.

[Embodiments of the invention] FIG. 2 shows the configuration of an embodiment of the present invention.

In this embodiment, the branch circuit (14
) is provided, and its output is also guided to the audio detection circuit (111).

The signal detected by the level detection circuit 0) is
1 = Guided to Tsar α floor. This judgment processor (
On the first floor, according to a predetermined algorithm, an antenna is selected and a command is issued to the drive circuit (6) to operate the high frequency switch.

In the configuration shown in FIG. 2, a level detection circuit (4) detects the video level and audio level input to each antenna.

Obtained through 02. Each level is sent to a level judgment processor (1→.In the processor, analog to digital conversion is performed and each signal is obtained as a digital quantity.

FIG. 3 shows an example of the configuration of the processor (13).

Each output obtained from each level detection circuit is converted into a digital value by an A/D converter and stored in a memory (9).

Using this memory, the arithmetic unit 00 selects an antenna according to the following procedure (algorithm), for example.

(1) Compare the video outputs V1 to +V4 of each antenna and find the order of magnitude (for example, V2 (maximum level), V4 (second level), +V1 (third level), +V3 (4 th Luher)).

(2) Next, the audio output level A2 of the anti-nana 2 corresponding to the maximum video output level ÷ 2 is constant.
It is determined whether it is less than or equal to 0 or greater than 0, and if it is greater than or equal to 70, two antennas are selected.

(3) In (2), if ■0 or less, the video output level is 2.
Select the audio output level A4 corresponding to the antenna of the second highest level 4, and determine whether it is below 0 or above 0.

If the number is 70 or more, select 4 antennas.

If it is less than VO, the same procedure is followed.

In the configuration shown in Figure 2, each antenna is connected to a chip, a video detection circuit, an audio detection circuit, a level detection circuit, and a branch circuit, but as shown in Figure 3, there is only one system each for video and audio. It is also possible to switch each antenna at high speed over a certain period of time.

In this case, the timing for switching each antenna in turn is provided by the processor. The processor detects the video and audio levels according to the number of antennas and switches on the previously selected antenna until it selects the antenna according to a predetermined algorithm.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional television diversity direction device, FIG. 2 is a block diagram of an embodiment of the present invention, and FIG. 3 is a diagram showing an example of the configuration of a determination processor used in the present invention. 4
The figure is a configuration diagram of another embodiment of the present invention. 1... Antenna element, 2... Tuner, 3...
Video detection circuit, 4... Level detection circuit, 5... Comparison circuit, 6... Drive circuit, 7... High frequency switch, 8... Output terminal, 11...
Audio detection circuit, 12...Level detection circuit, 13...
Judgment processor, 14... Branch circuit, 9... Memory, 10... Arithmetic unit, Addition... Timing. Agent Patent Attorney Nori Chika *Yuu, <et al. 1-0 Figures 2 and 3

Claims (1)

[Claims] In a television receiving antenna, multiple antennas and
It has a switch circuit that selects one of these antennas, and also has a tuner, video detection circuit, and audio detection circuit connected to these antennas, and a level detector that detects each detection output. An antenna device comprising a processor and a switch driving circuit that determine switching of the switch using both levels.