JPH0375089B2 - - 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.

Composition of the Invention In order to achieve the above object, the present invention provides a structure that is embedded in a car body wall without forming a protrusion on the outer surface of the car body so as to collect magnetic flux based on an induced current induced in the car body by received radio waves. Ferrite core and
A pickup coil for resonance and a pickup coil for reducing mismatch loss are wound around the ferrite core so that an induced current is induced based on the magnetic flux collected in the ferrite core.

[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 recess 12 having an arbitrary width and length is formed at an arbitrary location on the inner surface (inside the passenger compartment) of a car body outer plate (conductor iron plate) 10 as a car body wall, and a ferrite core 14 is inserted into the recess 12. It's buried. Since the vehicle body outer panel 10 has coating layers 16 and 18 on the inner and outer surfaces, the ferrite core 14 is inserted and buried in the recess 12 so as to be in contact with the vehicle body outer panel 10. The ferrite core 14 has a pickup coil 2 for resonance and for reducing mismatch loss.
The pickup coil 20 has a capacitor 24 connected in series and a variable capacitance diode 26 connected in parallel.
One end of a high-frequency choke coil 28 is connected between the connection path between the capacitor 24 and the variable capacitance diode 26, and a DC voltage is applied to the variable capacitance diode 26 via the power line 30, so that the capacitance of the variable capacitance diode 26 can be varied. This is the configuration that will be used. The other pickup coil 22 has a number of turns set so that the input impedance is 50Ω, and one end thereof is connected to an impedance converter (including an amplifier) 32, and the other end is connected to the cathode of the variable capacitance diode 26. , the impedance converter 32 and the ground external wire 34a of the coaxial cable 34
is connected to. The output of the impedance converter 32 is connected to the core wire 34b of the coaxial cable 34.

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 vehicle body forms a magnetic flux near the recess 12. The magnetic flux is collected by the ferrite core 14, which is a magnetic material, and a high-density magnetic flux is formed. In this case, the vehicle body outer plate 10
If the distance between the ferrite core 14 and the ferrite core 14 is large, the magnetic resistance will increase and sufficient magnetic flux collection will not be possible, so it is necessary to bring them into close contact with each other.
The magnetic flux collected in the ferrite core 14 forms an induced current corresponding to the magnetic flux in the pickup coils 20, 22 wound around the ferrite core 14. The amount of induced current in the pick-up coil 20 is
It is determined by the parallel resonance between the pickup coil 20 and a circuit that tunes to the reception frequency using the capacitor 24 and the variable capacitance diode 26, and only Q (resonance magnification) times this resonance circuit is picked up.
The resonant frequency of the above-mentioned tuning circuit can be changed by applying a DC voltage to the variable capacitance diode 26 via the high frequency choke coil 28 and the power supply line 30 to vary the capacitance of the variable capacitance diode 26. . The current induced in the pickup coil 22 is transmitted to the receiver via the coaxial cable 34. Since the output impedance of this pickup coil 22 is set to 50Ω, it can be used even if it is directly connected to a 50Ω coaxial cable 34, but in order to achieve a wide band, it is necessary to match the impedance converter 32 and the coaxial cable 34. and is configured to match the pickup coil 22 and the impedance converter 32,
This is to reduce mismatch loss as much as possible.

Figure 2 shows tap 3 on the pick-up coil 20.
6 to form the pickup coil 22. According to this second embodiment, there is an advantage that the number of coils may be small. Note that it is necessary to match the output impedance to 50Ω.

[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. Furthermore, since the mismatch loss is reduced, the antenna always has the effect of ensuring the best reception performance.

[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... Recessed portion, 14... Ferrite core, 20, 22... Pick up coil.

Claims (1)

[Claims] 1. A ferrite core embedded in the car body wall without forming a protrusion on the outer surface of the car body so as to collect magnetic flux based on the induced current induced in the car body by received radio waves, and 1. A vehicle antenna device comprising: a resonance pick-up coil and a mismatch loss reduction pick-up coil that are wound around the ferrite core so that an induced current is induced based on the ferrite core.