JPH0412044B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multi-channel in-vehicle antenna using a hula hoop antenna, which is particularly capable of receiving AM broadcasts in the KHz band.

Radio waves from mobile devices such as cars can be used for purposes other than work.
AM broadcast, FM broadcast, VHF band TV, UHF
Broadband TV, wireless telephones, etc. tend to cover an extremely wide frequency band. However, if these antennas are arranged near the roof of a vehicle with a high ground clearance (good gain), it is undesirable not only from an aesthetic point of view but also from a driving performance point of view.

The first object of the present invention is to use a hula hoop.
This is an attempt to construct a compact multi-channel composite antenna using a Hoop antenna. The hula hoop antenna is DDRR (Directional−
It is a ring-shaped antenna with a circumference of λ/4 and its performance is equivalent to a whip antenna with a length of λ/4. There are also reports that reception was possible even if the ring-shaped element was lifted horizontally by only about 0.007λ from the ground plane.

By the way, this hula hoop antenna can be used in the KHz band.
When trying to receive an AM broadcast, the wavelength λ is
With a diameter of 190 to 600 m, it is extremely large and cannot be used in vehicles.

Figure 1 shows an example of a vehicle-mounted composite antenna that can solve the above-mentioned problems. 1 is a hula hoop antenna, 2 is its base plate, 3 is a dielectric dome, 4 is a power supply coaxial cable, and 5 is the vehicle body (for example, the roof). , 6 is a dielectric support that electrically floats the ground plate 2 from the main body, 7 is a tuning circuit (group) in the MHz band or higher ranging from FM to TV broadcasting, and 8 is a tuning circuit for AM broadcasting. The main plate 2 is a circular plate with a diameter of about 35 cm, and the dome 3
The height to the surface is about 3 cm. This antenna 1 is supported by a supporter made of plastic or the like on a ground plane 2.

Since broadcasts other than AM broadcasts are in the several 10 to several 100 MHz band, the wavelength λ is on the order of several meters. Therefore, the diameter D of the hula hoop antenna 1 can be realized as several 10 to several 100 mm from D0.25λ/π. FIG. 2 shows an example in which hula hoop antennas 1a to 1c having different diameters are arranged concentrically facing a common ground plate 2, and the antennas are for FM, VHF-TV, and UHF-TV in order from the outside. 4a to 4c are their power supply cables,
Further, C ₁ to _{C 3} are variable capacitors for band adjustment. A plurality of these antennas can be accommodated within the dome 3 of FIG.

On the other hand, for AM, a capacitive antenna is used in which the base plate 2 is an element and the vehicle body 5 is a base plate.
The performance of this antenna is better as the area of the ground plate 2 is wider and the height H from the main body 5 is higher, but if the diameter of the ground plate 2 is 35 cm, H=5 cm or more is sufficient. Therefore, since the height above the ground plane 2 is about 3 cm, a multi-channel composite antenna including AM can be constructed with a height of about 8 cm.

By the way, one end of the tuning circuit shown in FIG. 1 is connected to the antenna 1 through the center conductor 41 of the tuning cable 4, and the other end is connected to the ground plane 2 through the outer conductor 42 of the cable. Further, one end of the tuned circuit 8 is connected to the ground plate 2 through the outer conductor 42 of the cable, and the other end is connected to the same potential as the main body 5. If one end of the tuning circuits 7 and 8, which have different frequency bands, is shared by the ground plane 2 as shown in Figure 3, consideration must be given to obtaining sufficient high-frequency impedance corresponding to each frequency on the receiving circuit side. It is.

A second object of the present invention is to further improve this point and simplify the configuration of the receiving circuit.

The in-vehicle antenna of the present invention has a hula hoop antenna for use in the MHz band or above, which is disposed opposite to the surface conductive layer of a dielectric substrate having conductive layers on both sides, and which is surrounded by a dielectric dome, and which is surrounded by a dielectric dome. The rear conductive layer of the vehicle body substrate is placed so as to be electrically received from the vehicle body, so that the space between the rear conductive layer and the vehicle body is used as a KHz band capacitive antenna. However, this will be explained in detail below with reference to the illustrated embodiment.

FIG. 4 is an explanatory diagram showing the outline of the present invention, in which 10 is an ethylene dielectric substrate approximately 4 mm thick;
is a conductive layer such as copper foil formed on the front and back surfaces, 11
1 is a conductor connected to the back conductive layer 2'. The surface conductive layer 2 corresponds to the ground plate 2 in FIG. 3, and is connected to the outer conductor 42 of the power supply cable 4. Terminal A is connected to the hula hoop antenna 1 through the center conductor 41, terminal B is connected to the surface conductive layer 2 through the outer conductor 42, and terminal C is kept at the same potential as the vehicle body 5, but in the present invention, the conductor A terminal B' connected to the back conductive layer 2' through 111 is provided separately, and a tuning circuit 7 is connected between the terminals A and B.
A tuning circuit 8 is connected between B' and C. In this way, there is a dielectric 1 between terminals B and B'.
Since it is electrically isolated at 0, the design of the receiving circuit side becomes easier. Moreover, since the dielectric substrate 10 is thin, it does not hinder miniaturization.

FIG. 5 shows a specific example, where 11 is a power feeding coaxial cable with 111 as the center conductor, and 112 is its outer conductor. This outer conductor 111 is connected to the vehicle main body 5, but the outer conductor 42 on the cable 4 side is made to pass through the main body 5 without contact. The structure around the antenna 1 is similar to that shown in FIG.

As described above, according to the present invention, the KHz band ~
There is an advantage that a multi-channel vehicle-mounted antenna up to the MHz band can be realized compactly without complicating the configuration of the transmission and reception circuits for the KHz band and MHz band.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing an example of a multi-channel vehicle-mounted antenna, Fig. 2 is an explanatory diagram of a hula hoop antenna with a multiple structure, Fig. 3 is a schematic explanatory diagram of Fig. 1, and Fig. 4 is an embodiment of the present invention. FIG. 5 is a schematic explanatory diagram showing a specific example thereof. In the figure, 1, 1a to 1c are hula hoop antennas,
2 is a front conductive layer, 2' is a back conductive layer, 3 is a dielectric dome, 4, 4a to 4c, 11 is a power supply cable,
5 is the vehicle body, 6 is the support body, 7 and 8 are the tuning circuits,
10 is a dielectric substrate.

Claims (1)

[Claims] 1. A hula hoop antenna for use in the MHz band or above is disposed facing the front conductive layer of a dielectric substrate having conductive layers on both sides, and its surroundings are covered with a dielectric dome, and the back surface conductive layer of the dielectric substrate is An on-vehicle antenna characterized in that the layer is electrically suspended from the vehicle body so that the space between the back conductive layer and the vehicle body is used as a KHz band capacitive antenna.