JPH0575507A - Antenna selection controller - Google Patents

Abstract

PURPOSE:To obtain the voices having the high receiving levels as well as the reduced disturbance of a multipath. CONSTITUTION:The antennas 1A and 1C and the antennas 1B and 1D provided on the roof of a vehicle have the 8-shaped directivity of the same characteristics. A multipath distortion comparator 15 compares the multipath distortion values with each other for the signals received at both antennas 1A and 1B and choose the antenna of the smaller distortion value. The signals of a pair of antennas having smaller distortion value are inputted to a receiving level comparator 25 or 26 through the switching circuits 17 and 18 or 2O and 21. The comparator 25 or 26 compares the receiving levels of the signals received by the antennas with each other. The signal of the antenna having the higher receiving level is closen by a switching circuit 27 or 28 and detected by a detection circuit 29. Then the detected signal is reproduced and outputted by a speaker 30.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna selection control device mounted on a vehicle, and more particularly to a vehicle-mounted antenna selection control device having both directivity and space diversity functions.

[0002]

2. Description of the Related Art Spatial diversity is used as an FM broadcast receiving system in an in-vehicle FM receiver. The space diversity is a method of selecting an antenna having a high reception level by utilizing the fact that the received electric field strengths of the respective antennas are uncorrelated when two omnidirectional antennas are arranged at a certain interval.

FIG. 4 shows the structure of a conventional antenna selection control apparatus based on this type of space diversity system, in which omnidirectional antennas 1 and 2 are arranged at a certain interval, and The input level of the received input signal is compared by the input level comparison circuit 3, the received signal from the antenna with the larger input level is selected by the switching circuit 4, demodulated by the demodulation circuit 5, and reproduced by the speaker 6. obtain.

[0004]

In such conventional space diversity, the received electric field strength is used as the antenna selection means, and therefore it is not effective against multipath interference which is a problem in mobile reception. An object of the present invention is to provide an antenna selection control device capable of obtaining voice with a high reception level with less multipath interference.

[0005]

In order to achieve such an object, the present invention is provided at an arbitrary position of a vehicle at a predetermined interval, has an 8-character directivity characteristic, and has a characteristic of each set. Of at least two antennas that are substantially the same, multipath detecting means for detecting the multipath distortion amount from the received signals of one antenna of each group by comparison, and one antenna of one group is selected based on the detection result. And a second antenna selecting means for comparing the signal levels of the received signals of the antennas of the selected group and selecting the antenna with the higher signal level among the antennas of the selected group. The reception signal selected by the second antenna selection means is demodulated.

[0006]

According to the present invention, at least two sets of antennas each having an 8-character directional characteristic and having substantially the same characteristic are provided, the multipath distortion amount of the received signal of the antennas is detected, and the antennas are detected based on the respective results. Select. And from within it,
Since an antenna with a small amount of multipath distortion and a high reception level is selected by switching, an antenna with a small amount of multipath distortion and a high reception level can be selected.

[0007]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows the configuration of an embodiment of an FM broadcast mobile reception system including an antenna selection control device according to the present invention. 1A, 1B, 1C and 1D are 8-shaped directional antennas, 11, 12, 19, 22 is a tuner, 13, 14,
Reference numerals 23 and 24 are intermediate frequency (IF) amplifiers, 15 is a multipath distortion comparison circuit as the multipath detecting means, 16,
Switching circuits 17, 18, 20, and 21 constitute the first antenna selecting means. Reference numerals 25 and 26 are reception level comparison circuits, and 27 and 28 are switching circuits, which constitute the second antenna selection means. 29 is a detection circuit, 30
Is a speaker.

Each antenna 1A, 1B, 1C, 1D is shown in FIG.
The antennas are arranged on the roof of the car as shown in Fig. 1, and the directivity of each antenna is a figure 8 directivity.
As shown in FIGS. 3A and 3B, B and 1D have the same characteristics, and the directivities thereof are deviated by 90 °.

In FIG. 1, the received signals input from the antennas 1A and 1B are input to the respective tuners 11 and 12, the high frequency signal of the channel is selected, and the intermediate frequency (I
F) and is amplified by IF amplifiers 13 and 14. IF
The signals amplified by the amplifiers 13 and 14 are input to the multipath distortion comparison circuit 15, the multipath distortion amounts of both signals are compared, the one with the smaller distortion amount is selected, and the switching circuit 16 causes the switching circuit 17, 18 or 20, 21 is made conductive.

Specifically, as a result of the comparison of the multipath distortion comparison circuit 15, when the amount of multipath distortion of the signal of the antenna 1A is small, the switching circuits 20 and 21 are turned on, and the IF amplifier 14 outputs the signal of the antenna 1A. The reception signal is applied to the reception level comparison circuit 26 through the switching circuit 20, and the reception signal from the antenna 1C is converted into an intermediate frequency through the switching circuit 21, the tuner 22, and the IF amplifier 23, and after amplification, the reception level is also the same. It is applied to the comparison circuit 26.

In the reception level comparison circuit 26, the antenna 1
The reception signals from A and 1C are compared, and the signal of the antenna with the higher reception level is selected by the switching circuit 27, detected by the detection circuit 29, and reproduced and output from the speaker 30.

On the other hand, as a result of the comparison in the multipath distortion comparison circuit 15, when the amount of multipath distortion of the received signal of the antenna 1B is small, the switching circuits 17 and 18 are brought into the conducting state, and similarly, the antennas 1B and 1D. The reception level of the reception signal is compared by the reception level comparison circuit 28, the signal of the antenna with the higher reception level is detected by the detection circuit 29, and reproduced and output from the speaker 30.

In the above-described embodiment, an example using two sets of antennas has been described, but the present invention is not limited to this. Also, the directivity of the two sets of antennas is 90 °
Although the shift example has been described, the shift example is not limited thereto. Further, as a multipath distortion comparison circuit, for example, Japanese Patent Application No.
-119180, the received signal is envelope-detected, the amplitude modulation component included in the detected signal is extracted to detect the distortion amount of the maximum multipath component, and the multipath amount is compared. One can be used.

[0014]

As described above, according to the antenna selection control device of the present invention, by providing both the functions of the directional diver and the space diversity, it is possible to produce a reproduced voice having a high reception level with less multipath interference. Obtainable.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of an antenna selection control device according to the present invention.

FIG. 2 is a diagram showing an arrangement of antennas.

FIG. 3 is a diagram showing the directivity of an antenna.

FIG. 4 is a configuration diagram of a conventional antenna selection control device.

[Explanation of symbols]

1A, 1B, 1C, 1D Antenna 11, 12, 19, 22 Tuner 13, 14, 23, 24 IF Amplifier 15 Multipath distortion comparison circuit 16, 17, 18, 20, 27, 28 Switching circuit 25, 26 Reception level comparison Circuit 29 Detection circuit 30 Speaker

Claims (1)

[Claims] 1. At least two antennas, which are provided at arbitrary positions on a vehicle at predetermined intervals, have an 8-character directional characteristic, and the characteristics of the respective groups are substantially the same, and one of the respective groups. Multipath detecting means for detecting the amount of multipath distortion from the received signal of the antenna by comparison, first antenna selecting means for selecting one of the antennas according to the detection result, and received signal of the antenna of the selected group Second antenna selecting means for comparing the signal levels of the two and selecting the antenna with the higher signal level from the selected set of antennas,
An antenna selection control device, which demodulates a reception signal selected by the second antenna selection means.