JPH084202B2 - Car antenna device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a vehicle antenna device, and more particularly to a vehicle antenna device that can be used for radio broadcasting, a mobile phone, and the like.

BACKGROUND ART Conventionally, a radio broadcast antenna and a car telephone antenna are separately installed in a vehicle body. When these antennas are formed in the shape of a long rod, a plurality of antennas are projected on the vehicle body, which causes a problem in that the aesthetic sense is deteriorated and a wind noise is generated during traveling.

Problem to be Solved by the Invention An object of the present invention is to provide an antenna device for an automobile capable of reducing the number of longitudinal rod antennas protruding from the vehicle body of the automobile.

Means for Solving the Problems The present invention is directed to a stretchable elongated first conductor, an element for frequency band separation which is connected to a lower portion of the first conductor and has a large impedance at a high frequency, and a lower portion of the element. A second longitudinal conductor to be connected, wherein the lower portion of the second conductor is used as a feeding point, only the second conductor is used as an antenna for high frequencies, and at a frequency lower than the frequency at which the second conductor is used as an antenna, An antenna device for an automobile, wherein the first conductor and the second conductor are used as a whip antenna.

Further, the second conductor of the present invention is a whip antenna.

Furthermore, the second conductor of the present invention is characterized in that it is a vertical dipole antenna.

Operation According to the present invention, the impedance of the element is small in a relatively low frequency band such as radio broadcasting, and therefore the first conductor and the second conductor can be used as a whip antenna. In a relatively high frequency band for a car telephone or the like, the element has a large impedance, so that the second conductor is used as an antenna and the traveling wave is transmitted to the first conductor. Will be blocked. In this way, the entire shape can be formed into a pole shape having a substantially longitudinal rod shape and can be shared by different frequency bands. Therefore, it becomes possible to reduce the number of antennas mounted on the body of the automobile. Further, since the lower part of the antenna is used as a high frequency receiving antenna and the entire antenna is used as a low frequency receiving antenna, the feeding points of these two antennas can be shared. Therefore, unlike the case where the high frequency receiving antenna is provided on the upper part of the antenna, it is not necessary to route the antenna cable to the upper part of the antenna, and it can be realized with a simple structure. Furthermore, when the antenna has an expandable structure, it is not necessary to expand or contract the antenna cable, so that the structure can be simplified and high durability can be obtained.

Embodiment FIG. 1 is a perspective view showing a state of an antenna device 1 according to an embodiment of the present invention when it is extended, and FIG. 2 is a perspective view showing the antenna device 1 in a shortened state. The antenna device 1 is attached to a rear trunk or a roof top of a metal body 2 of an automobile and is commonly used for receiving radio broadcasts and for automobile telephones.

FIG. 3 is a vertical cross-sectional view showing a state in which the antenna device 1 is extended as in FIG. A right cylindrical metal base 4 is fixed to the vehicle body 2 via an electric insulator 3 made of a material such as synthetic resin. The first conductor 5, the loading coil 6, and the second conductor 7 are housed in the base body 4 in a telescope shape, and can be shortened as shown in FIG. The first conductor 5 includes conductors 8,8a, 9,10 in order from the top. The loading coil 6 functions as a frequency band separating element having a large impedance in a relatively high frequency band for a car telephone, and has a small impedance in a relatively low frequency band of radio broadcasting.

First conductor 5, loading coil 6, and second conductor 7
When the strand of the loading coil 6 is linearly extended, the total length l1 is defined as λ1 / 4, where λ1 is the wavelength of the frequency band of radio broadcasting.

The frequency band of frequency modulated radio broadcasting in Japan is
76 to 90 MHz, and 11 is set to about 90 cm, for example.
Thus, the first conductor 5, the loading coil 6, and the second
The conductor 7 functions as a whip antenna in the frequency band of radio broadcasting.

The length l2 of the second conductor 7 is determined to be λ2 / 4, where λ2 is the wavelength of the frequency band for car telephones.

The length l2 is set to about 9 cm since the frequency band for car telephones is 860 to 940 MHz. Thus the second conductor 7
Acts as a whip antenna in the frequency band of mobile phones.

When the radio broadcast is not received, the conductors 8, 8a, 9 can be shortened and can be kept in the standby state in the frequency band of the mobile phone as described above.

The center conductor 13 of the coaxial cable 12 is connected to the base body 4,
The outer conductor 14 is grounded to the vehicle body 2. Coaxial cable 12
Is connected to the duplexer 15 and the coaxial cable 16
Connected to the radio receiver via a coaxial cable 17
Is connected to a car telephone transceiver via.

In this way, a single pole antenna device can be shared in different frequency bands. Therefore, it is not necessary to install a large number of antennas on the vehicle body, the aesthetics can be improved, and the generation of wind noise during traveling can be suppressed.

Further, since a high frequency antenna is provided in the lower part and the feeding point, that is, the connection point of the center conductor 13 of the coaxial cable 12 is shared by the high frequency antenna and the low frequency antenna,
It is not necessary to draw the coaxial cable 12 to the upper part of the antenna, and particularly when the conductors 5 and 7 and the loading coil 6 can be expanded and contracted, the structure can be greatly simplified and the durability can be improved. it can.

The loading coil 6 has a high impedance with respect to high frequencies, and performs a blocking operation with respect to high frequencies. Therefore, when the antenna is expanded by extending the conductors 8, 8a and 9, the entire length of the first conductor 5, the coil 6 and the second conductor 7 acts as an antenna for low frequencies and is below the coding coil 6 for high frequencies. The second conductor 7 acts as an antenna.

Next, to describe the necessity of the present invention, that is, how to use it,
For automobile antennas, the antenna is retracted (contracts) when not in use to reduce wind noise (sound generated by wind hitting the antenna while driving) and to prevent damage to the antenna.
Is desirable. The present invention has been made in consideration of this point, and in consideration of the fact that a telephone or the like needs to be constantly received by standby, whereas a radio or the like only needs to be received when watching. When the radio is received, the antenna is extended to operate as an antenna for both radio and telephone, and when the radio is not received, it is operated as an antenna exclusively for telephone.

As described above, the loading coil 6 has a high impedance with respect to high frequencies and performs a blocking operation with respect to high frequencies. Therefore, when the antenna is extended, the entire length acts as an antenna for low frequencies and low for high frequencies. The second conductor 7 under the dane coil 6 acts as an antenna.

FIG. 4 is a perspective view showing a state of an antenna device 19 according to another embodiment of the present invention when it is extended, and FIG.
FIG. 6 is a perspective view showing a state in which the antenna device is shortened, and FIG. 6 is a longitudinal sectional view of the antenna device 19 shown in FIGS. 4 and 5 when the antenna device 19 is extended. This embodiment is similar to the previous embodiment,
Corresponding parts are designated by the same reference numerals. It should be noted that
A base body 20 made of metal and formed in a right cylindrical shape is fixed to a metal body 2 of an automobile. First for receiving radio broadcasting
The conductor 21, the loading coil 22, and the second conductor 23 are used. The first conductor 21 includes expandable conductors 24, 25, 26. The loading coil 22 has a configuration similar to that of the loading coil 6 described above, has a large impedance at high frequencies, and prevents signals of high frequency from traveling to the first conductor 21 side.

The second conductor 23 includes conductors 27 and 28. The conductor 27 is a base body via a short-cylinder electric insulator 29 made of synthetic resin or the like.
Mounted so that it can be stored in 20. A conductor 28 is connected to the base body 20 via a metal connecting member 30 extending outward in the radial direction. The inner conductor 13 of the coaxial cable 12 is electrically connected to the conductor 27, and the outer conductor 14 is electrically connected to the conductor 28 via the connection member 30. In a relatively low frequency band such as radio broadcasting, the first conductor 21 and the loading coil
22 and the conductor 27 of the second conductor 23, assuming that the total length l3 when the loading coil 22 is linearly extended, and the frequency band of the radio broadcast is λ1,
It is set according to the formula.

The lengths l4a and l4b of the conductors 27 and 28 are determined according to the fourth equation when the wavelength λ2 of the frequency band of the car telephone is used.

(L4a + l4b) in the fifth formula is set to about 17 cm.

When only a mobile phone is used without receiving radio broadcasting, the first conductor 21 and the loading coil 22 may be shortened and housed in the second conductor 23. The first conductor 21, the loading coil 22 and the conductor are used when the radio broadcast is not received and the car telephone communication is not performed.
27 is housed in the base body 20 to obtain the state shown in FIG. The embodiment shown in FIG. 6 uses the so-called sleeve antenna principle. The conductor 28 is connected to the vehicle body 2 and is grounded. It is known that a folded ground having a length of λ / 4 operates in the same manner as a normal element, and this element is a so-called vertical element. It is the same as the dipole antenna. The difference from the antenna of FIG. 3 is that the antenna of FIG. 3 grounds the body that is the vehicle body 2 of the automobile.
Although the characteristics vary slightly depending on the body shape, the vertical dipole antenna itself is an antenna element (dipole), and therefore the characteristics (omnidirectionality) are stable regardless of the body shape.

As described above, the loading coil 22 has a large impedance in the high frequency band of a mobile phone and a impedance as small as possible in the low frequency band of radio broadcasting. An element having another configuration that performs such a function may be used. For example, a parallel resonant circuit may be formed by a coil and a stray capacitance and configured to resonate in a high frequency band and have a large impedance. Good. The lengths l1 to l4 in each of the above-described embodiments may be appropriately changed according to the frequency used, and may be set to values having other magnifications of those wavelengths λ1 and λ2.

Effects As described above, according to the present invention, a single pole-shaped antenna device can be shared in different frequency bands, so that aesthetics are improved and generation of wind noise during traveling is suppressed. Will be able to.

Further, since the lower part of the antenna is used as a high frequency receiving antenna and the entire antenna is used as a low frequency receiving antenna, the feeding points of these two antennas can be shared. Therefore, unlike the case where the high frequency receiving antenna is provided on the upper part of the antenna, it is not necessary to route the antenna cable to the upper part of the antenna, and it can be realized with a simple structure. Furthermore, when the antenna has an expandable structure, it is not necessary to expand or contract the antenna cable, so that the structure can be simplified and high durability can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing a state of an antenna device 1 according to an embodiment of the present invention when it is extended, FIG. 2 is a perspective view showing a shortened state of the antenna device 1, and FIG. 3 is a vertical cross section of FIG. FIG. 4 is a perspective view showing the antenna device 19 according to another embodiment of the present invention when it is extended, FIG. 5 is a perspective view showing the antenna device 19 in a shortened state, and FIG. 6 is FIG. FIG. 1,19 …… Antenna device, 2 …… Car body, 5,21 …… First conductor, 6,22 …… Loading coil, 7,23 …… Second conductor,
4,20 ... Base

Claims (3)

[Claims] 1. A stretchable elongated first conductor, an element for frequency band separation connected to a lower portion of the first conductor and having a large impedance at a high frequency, and an elongated second conductor connected to a lower portion of the element. And using the lower part of the second conductor as a feeding point, using only the second conductor as an antenna for high frequencies, and using the second conductor at a frequency lower than the frequency used as the antenna,
An antenna device for an automobile, characterized in that a conductor and a second conductor are used as a whip antenna. 2. The vehicle antenna apparatus according to claim 1, wherein the second conductor is a whip antenna. 3. The vehicle antenna apparatus according to claim 1, wherein the second conductor is a vertical dipole antenna.