JPH0375088B2 - - 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 is 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. A pick-up coil 20 is wound around this ferrite core 14, and a capacitor 22 connected in series is connected to this pick-up coil.
and a variable capacitance diode 24 are connected in parallel. One end of the pick-up coil 20 is connected to a ground outer wire 26a of a coaxial cable 26 for connection to a receiver (not shown), and the other end is connected to a core wire 26b. Between the capacitor 22 and the variable capacitance diode 24,
One end of the high-frequency choke coil 28 is connected, and a DC voltage is applied to the variable capacitance diode 24 via a power line 30, so that the capacitance of the variable capacitance diode is varied.

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 the two must be in close contact with each other. The pick-up coil 2 is wound around the ferrite core 14 by the magnetic flux collected on the ferrite core 14.
An induced current corresponding to the magnetic flux is formed at zero. The amount of induced current in the pick-up coil is
2, a circuit for tuning to the receiving frequency using a variable capacitance diode 24, and the pickup coil 20. Only the Q (resonance magnification) times this resonance circuit is picked up. The resonant frequency of the tuned circuit can be changed by applying a DC voltage to the variable capacitance diode 24 via the high frequency choke coil 28 and the power line 30 to vary the capacitance of the variable capacitance diode 24. . The current induced in the pickup coil 14 will be transmitted to the receiver via the coaxial cable 26.

Pickup coil 1 as in the first embodiment above.
The current induced in 4 is passed directly to the coaxial cable 26.
If the signal is transmitted between the two, the impedance may not be balanced between the two. Therefore, in the second embodiment shown in FIG. 2, an impedance converter (including an amplifier) 32 is provided at the connection between the pickup coil 20 and the coaxial cable 26. With this configuration, the pickup coil 20 and the coaxial cable This is effective in improving the receiving sensitivity of the receiving system since it is possible to eliminate impedance tension between the coaxial cable 26 and the coaxial cable 26, and also prevent insertion loss in the coaxial cable 26.

[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 vehicle body is used as an antenna element and the induced current flowing through the vehicle body is detected based on the received radio waves, the antenna has the effect of always 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...Recess, 14...Ferrite core, 20...Pickup 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 pickup coil wound around the ferrite core so as to induce an induced current based on the ferrite core.