JPH043682B2 - - 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.

[Prior Art] Conventionally, pole antennas have been the main vehicle antenna devices. On the other hand, vehicles include various vehicle-mounted wireless devices such as radios, televisions, personal radios, and telephones.

[Problems to be Solved by the Invention] Problems of the Prior Art However, in a vehicle equipped with all of these wireless devices, a large number of pole antennas are installed, which causes the following 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 the generation of wind noise, damage to the pole antenna due to tampering, theft, and the sticking of sliding parts due to intrusion of dirt or dust, which are the essential drawbacks of antennas that protrude outside the vehicle body.

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.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a magnetic shielding box provided in the vehicle interior with an opening of a predetermined width and length formed on a surface facing the vehicle body, and a magnetic shielding box located in the vicinity of the opening. and a pickup coil provided within the magnetic shield box.

[Function] As is clear from the above-described configuration, according to the vehicle antenna device according to the present invention, when an induced current is formed in the vehicle body due to the radio waves to be received, the magnetic field due to the induced current is generated within the magnetic shield box. It is picked up by the pick-up coil.

[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, and FIG. 2 is a partially cutaway perspective view of a magnetic shielding box (hereinafter abbreviated as "box") applied to this first embodiment. As shown in FIG. 2, the box 10 has an opening 1 of a predetermined width and length on one side.
2, and the box 10 is fixed in the vehicle interior by well-known fixing means (not shown) so that the opening surface faces and approaches the vehicle body 14. The surface of this vehicle body 14 has a coating layer 14a. A pick-up coil 16 is provided opposite to and adjacent to the opening 12, a variable capacitor 18 is connected to the pick-up coil 16 to form a loop, and a part of this loop is connected to a box 10 and a coaxial wire to which a ground external wire 20a is fixed. This configuration is connected to the core wire 20b of the cable 20.

Hereinafter, the operation of the first embodiment will be explained with reference to the basic principle diagrams shown in FIGS. 3 and 4. Third
The basic principle diagram in the figure is the magnetic field H created by the line current I.
The figure shows a state in which V is picked up by a loop and an open-circuit voltage V is generated.

By the way, when a vehicle enters a place where radio waves to be received exist, an induced current is formed in the vehicle body 14 by the radio waves based on Maxwell's basic equation. This induced current flows in a planar manner. Figure 4 shows the above induced current as the five line currents A to E.
This figure shows the magnetic fields H _A to H _E generated near the center of the loop-shaped pickup coil.If the width (interval) of the aperture 12 is made smaller, the resolution increases but the gain decreases. This shows that if the width is increased, the gain increases, but the directional resolution and selectivity of the induced current decreases.

A high frequency magnetic field based on the induced current formed in the vehicle body 14 is picked up by a pickup coil 16 and transmitted to the coaxial cable 20. At this time, by adjusting the capacitance of the capacitor 18 in the loop, the Q (frequency sharpness) of the loop can be increased. Further, by adjusting the position of the capacitor 18 and the box connection line 28 of the loop, the input impedance can be adjusted to 50Ω, thereby improving the sensitivity of the antenna. In addition, in this example,
Because the Q is high, it is possible to measure only specific frequencies, or it is necessary to remove the case and adjust the capacitor for each frequency used.

A second embodiment is shown in FIG. 5, and has a configuration in which a variable capacitance diode 22 and a capacitor 24 are connected in series with a pickup coil 16, and a power supply line 26 is connected to a connection path between the variable capacitance diode 22 and the capacitor 24. be. In this second embodiment, the capacitance of the variable capacitance diode 22 is changed by a DC voltage applied to the variable capacitance diode 22 via the power supply line 26, so that matching can be performed externally.

[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 installed together are eliminated. Ru. In addition, since the outer skin of the vehicle body is used as the antenna element, each antenna device is common and there is no mutual interference, greatly improving usability and installation, and ensuring antenna performance that fits each function. You can get the desired effect.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a first embodiment of a vehicle antenna device according to the present invention, FIG. 2 is a partially cutaway perspective view of a magnetic shielding box applied to this first embodiment, FIG. FIG. 4 is a diagram explaining the basic principle of the present invention, and FIG. 5 is a configuration diagram of a second embodiment. 10... Magnetic shield box, 12... Opening, 14... Vehicle body, 16... Pick-up coil, 18... Variable capacitor, 20... Coaxial cable, 22... Variable capacitance diode, 24... Capacitor.

Claims (1)

[Claims] 1. A magnetic shield box having an opening of a predetermined width and length formed in a surface facing the vehicle body and provided inside the vehicle interior, and a pickup coil provided in the magnetic shield box opposite to and in close proximity to the opening. An antenna device for vehicles.