JPH0375092B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a vehicle antenna device, and particularly to a vehicle antenna device that uses a vehicle body as a part of the antenna.

BACKGROUND ART Conventionally, pole antennas have been mainly used as vehicle antenna devices. On the other hand, vehicles are equipped with a variety of onboard wireless devices such as radios, televisions, personal radios, and telephones, and a vehicle equipped with all of these wireless devices requires a large number of pole antennas. This will cause such inconvenience.

Deterioration of reception performance due to deterioration of each antenna performance due to mutual interference between pole antennas (for example, gain decrease due to impedance change, directivity deterioration, etc.).

Negative impact on vehicle design due to overcrowding of pole antennas.

It is extremely difficult to take measures against wind noise, which is an essential drawback of antennas that protrude outside the car body, damage to pole antennas due to mischief, theft, and sliding parts that become stuck due to intrusion of dirt or dust, etc.

When washing the car, parking it in the garage, etc., it is necessary to store or remove the pole antenna, resulting in poor operability.

OBJECTS OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide a vehicle antenna device that eliminates all the conventional disadvantages and can always ensure the best reception performance.

Structure of the Invention In order to achieve the above-mentioned object, the present invention provides a structure in which the car body walls are mutually connected so as not to form protrusions on the outer surface of the car body so as to collect magnetic flux based on induced current induced in the car body by received radio waves. It has two ferrite cores embedded at right angles and two pick-up coils wound around each of the two ferrite cores and connected to each other, and is non-directional in all directions. do.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing a first embodiment of the present invention. In Fig. 1, a car body outer plate 1 as a car body wall
0 is a conductive iron plate 10a and a coating film 10 on its inner and outer surfaces.
b, 10c, and two mutually orthogonal recesses 12, 14 having arbitrary widths and lengths are formed at arbitrary locations on the inner surface (interior side of the vehicle interior) of the vehicle body outer panel 10. Ferrite cores 16 and 18 having substantially the same dimensions as the recesses 12 and 14 are buried so as to be in contact with the conductive iron plate 10a. A pick-up coil 20 is wound around the ferrite core 16, and both ends of the pick-up coil 20 are connected to the other ferrite core 16.
It is connected in parallel with a pickup coil 22 wound around 8. Further, a series-connected capacitor 24 and a variable capacitance diode 26 are connected in parallel to both ends of the pickup coil 20 to resonate with the frequency of the received broadcast wave. In addition, a high frequency choke coil 28 for applying a control voltage and a shield outer wire 30a of the coaxial cable 30 are connected to both ends of the variable capacitance diode 26, and the variable capacitance diode 26 is connected to both ends of the variable capacitance diode 26 for resonating with the reception frequency.
It is now possible to control the capacity of The tuning capacitance is determined by the inductance of the two pickup coils 20 and 22, the capacitance of the capacitor 24, and the capacitance of the variable capacitance diode 26.

The first embodiment of the present invention has the above configuration, and its operation will be explained below.

When a vehicle enters a location where radio waves to be received are present, the radio waves create an induced current in the vehicle body based on Maxwell's basic equation. The induced current formed in the car body flows through the recesses 12 and 14.
A magnetic flux is formed in the vicinity of . The magnetic flux is collected by the ferrite cores 16 and 18, which are magnetic materials, and a high-density magnetic flux is formed. In this case, if the gap between the vehicle body outer plate 10 and the ferrite cores 16 and 18 is large, the magnetic resistance will increase and sufficient magnetic flux collection will not be possible, so it is necessary to bring the two into sufficiently close contact. The magnetic flux collected in the ferrite cores 16, 18 causes the ferrite cores 16, 18 to
An induced current corresponding to the magnetic flux is formed in the pickup coils 20 and 22 wound around the magnetic flux. The amount of induced current in the pick-up coils 20, 22 is determined by a circuit that tunes to the receiving frequency using a capacitor 24 and a variable capacitance diode 26, and a circuit that tunes the pick-up coils 20, 2
2, and only the Q (resonance magnification) times this resonant circuit is picked up. The resonant frequency of the tuning circuit can be changed by applying a DC voltage to the variable capacitance diode 24 via the high frequency choke coil 28 to vary the capacitance. The current induced in the pickup coils 20, 22 is transmitted to the receiver via the coaxial cable 30.

In this case, with the rectangular recess 12 and the way the pick-up coil 20 is wound as shown, the antenna has maximum gain in the direction perpendicular to the vehicle body skin 10, so omnidirectionality is achieved in all directions. Can not. However, as shown in the first embodiment, the two recesses 12 and 14 are made orthogonal to each other, and the recesses 12 and 14 are made perpendicular to each other.
By embedding ferrite cores 16 and 18 in 14 and connecting pick-up coils 20 and 22 wound around these ferrite cores 16 and 18 in parallel,
It can be made omnidirectional in all directions.

Note that if the current induced in the pickup coil 20 is directly transmitted to the coaxial cable 30 as in the first embodiment, impedance mating may not be achieved between them. Therefore, a second embodiment shown in FIG. 2 was proposed. In the second embodiment, a pick-up coil 20 and a coaxial cable 3
An impedance converter (including an amplifier) 32 is provided in the connection path between the pick-up coil 20 and the coaxial cable 30.
The impedance gap between the coaxial cable 30 and the coaxial cable 30 can be easily removed, and insertion loss with the coaxial cable 30 can be prevented, which is effective in improving the receiving sensitivity of the receiving system.

[Effects of the Invention] As detailed above, according to the vehicle antenna device according to the present invention, since there is no protrusion on the vehicle body surface, all the inconveniences that occur when a large number of conventional pole antennas are arranged in parallel are eliminated. be done. Further, effects such as non-directionality in all directions can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a first embodiment of a vehicle antenna device according to the present invention, and FIG. 2 is a block diagram of a second embodiment. 10... Vehicle body outer plate, 12, 14... Recessed portion, 1
6, 18... ferrite core, 20, 22... pick up coil.

Claims (1)

[Claims] 1. Two ferrite cores embedded in the wall of the vehicle body so as to be orthogonal to each other so as not to form protrusions on the outer surface of the vehicle body so as to collect magnetic flux based on induced current induced in the vehicle body by received radio waves; 1. A vehicle antenna device comprising two pick-up coils wound around two ferrite cores and connected to each other, and having omnidirectional properties in all directions.