JP2002158516A - On-vehicle antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an on-vehicle antenna, with which the antenna characteristics are made to stabilize by easily and surely performing grounding close to the base end of a monopole antenna. SOLUTION: Closely to the base end of the monopole antenna, an external conductor 14b of a coaxial cable 14 for transmitting signals is electrically connected via a short conductive connecting plate 16 to a capacity grounding plate 18 of a comparatively wide area in the manner of DC and a double sided tape is provided over all one side of this capacity grounding plate 18. The monopole antenna is located and fixed along with the edge of the rear window glass of an automobile, and the capacity grounding plate 18 is stuck and fixed on a body around a rear window.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle-mounted antenna device in which the antenna characteristics of a monopole antenna are stabilized.

[0002]

2. Description of the Related Art As an example of a vehicle-mounted antenna device, a single wire is disposed and fixed along the edge of a rear window glass of an automobile, and a coaxial cable for transmitting a signal is connected to a base end thereof. There is one that acts as a pole antenna. However, at the base end of this monopole antenna, there was no ground plane ground portion, and a non-parallel current flowed through the outer conductor of the coaxial cable, and the desired antenna function as a monopole antenna could not be obtained. Therefore, in order to improve such a problem, a conductive cable is electrically connected to an outer conductor of the coaxial cable, and the conductive cable is fixed to a body of an automobile by a screw and is electrically connected. Through the conductive cable, the outer conductor of the coaxial cable is grounded, and the non-parallel current is also grounded, so that the antenna function of the monopole antenna is improved.

[0003]

In order to fix the above-described conventional conductive cable to a vehicle body with screws,
Tighten and fix the conductive cable together with existing bolts,
The only way is to drill a new hole in the body and fix it with bolts and nuts. In order to fix the conductive cable with the existing bolt, there is no proper bolt at a desired position, and the conductive cable wired to the appropriate bolt tends to be long. Then, reliable grounding is not performed due to the inductive component and resistance component of the conductive cable itself,
The antenna function cannot be sufficiently improved. The conductive cable is wired along the body, and a stray capacitance is generated between the conductive cable and the body. Then, as the conductive cable vibrates due to the vibration of the automobile or the like, the magnitude of the stray capacitance also changes. Therefore, there is a problem that the ground is unstable and stable antenna characteristics cannot be obtained. In addition, in order to newly drill and mount, the body must be damaged, and the processing and mounting man-hours are required. In addition, the above-mentioned problems caused by the conductive cable cannot be improved.

[0004] The present invention has been made in view of the circumstances of the prior art, and has as its object to provide a vehicle-mounted antenna device in which the antenna characteristics are stabilized by simply and reliably grounding. .

[0005]

In order to achieve the above object, a vehicle-mounted antenna device according to the present invention comprises a short conductive connecting plate for an outer conductor of a coaxial cable for transmitting a signal near a base end of a monopole antenna. The capacitive grounding plate is electrically connected to the body of the vehicle, and the capacitive grounding plate is adhered and fixed to the body of the automobile with a double-sided tape.

Further, the monopole antenna may be arranged and fixed to a rear window glass of an automobile along an edge, and the capacitive ground plate may be adhered and fixed to the body around the rear window.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is an overall view of one embodiment of the vehicle-mounted antenna device of the present invention. FIG. 2 is a diagram illustrating an example in which the vehicle-mounted antenna device illustrated in FIG. 1 is provided in an automobile.

In FIG. 1, two monopole antennas 12 and 12 are arranged on a base 10 at an opening of about 90 degrees, and a central conductor 14 of a coaxial cable 14 and 14 is provided at each base end.
a and 14a are appropriately electrically connected. The outer conductors 14b, 14b of the coaxial cables 14, 14 are electrically connected to one end of a short conductive ground plate 16 made of a conductive material. To the other end of the conductive ground plate 16, a capacitive ground plate 18 made of a conductive material and having a relatively large area is electrically connected.
A double-sided tape (not shown) is provided on the entire surface of one side of the capacitance ground plate 18. The outer conductors 14b, 14b of the coaxial cables 14, 14 and the capacitive grounding plate 18 are of course electrically connected DC.

A vehicle-mounted antenna device 2 having such a configuration.
0 to the rear window glass 2 of the car as shown in FIG.
The monopole antennas 12, 12 are fixed to the indoor side surface along two outer edges from the corners by appropriate clamp members (not shown). Then, the capacitive grounding plate 18 is adhered and fixed to the body of the automobile around the rear window glass 22 by the double-sided tape.

The present inventors have proposed monopole antennas 12 and 1.
2, a folded antenna capable of resonating both the VHF low band and the VHF high band was used. The length D of the conductive connection plate 16 was set to about 150 mm, the width was set to 10 mm, the width L of the capacitive grounding plate 18 was set to 100 mm, and the width W was set to 35 mm. When the experiment was performed with the thickness of the double-sided tape set to 0.4 mm, extremely stable antenna characteristics were obtained. here,
The capacitance between the capacitance ground plate 18 and the body is approximately 8
It is 0 pF and can be grounded with a sufficiently low impedance with respect to the VHF low band. The length D of the conductive grounding plate 16 is about 150 mm, which is extremely short as compared with the conventional conductive cable, so that more reliable grounding is possible.

In the above-described embodiment, the monopole antennas 12, 12 disposed on the rear window glass 22 have been described. However, the present invention is not limited to this, and the present invention is applied to a rod antenna that is projected to the outside and disposed on the body. May be applied. In addition, monopole antenna 1
Each of the antennas 2 and 12 is not limited to a single wire, and may have any shape such as a folded antenna or a zigzag antenna. Further, it is needless to say that the present invention is not limited to the one that receives a VHF signal, and can be applied to an antenna that receives a UHF signal or an FM signal. Further, if a booster is provided in the base 10, the conductive connection plate 16 may be electrically connected to the outer conductor 14b of the coaxial cable 14 for transmitting a signal at a stage preceding the booster. In the above embodiment, the base 10 is provided with two monopole antennas 12 and 12 to constitute a diversity antenna. However, it is easily understood that the present invention can be applied to one monopole antenna 12. You can understand.

[0012]

As is apparent from the above description, the vehicle-mounted antenna according to the present invention has the following special effects.

[0013] In the vehicle-mounted antenna device according to the first aspect, since the capacitive grounding plate is attached and fixed to the body with the double-sided tape, the operation is simple. Moreover, the antenna is grounded near the base end of the monopole antenna, reliably grounded with an extremely small impedance, and the ground impedance does not fluctuate due to vibration or the like, and the antenna characteristics are stabilized.

According to the antenna device of the present invention, in the antenna device disposed on the rear window glass, stable antenna characteristics can be obtained without any trouble caused by the conventional conductive cable.

[Brief description of the drawings]

FIG. 1 is an overall view of an embodiment of a vehicle-mounted antenna device according to the present invention.

FIG. 2 is a diagram showing an example in which the on-vehicle antenna device shown in FIG. 1 is provided in an automobile.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 Monopole antenna 14 Coaxial cable 14b Outer conductor 16 Conductive connection plate 18 Capacitive grounding plate 20 In-vehicle antenna device 22 Rear window glass

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Keiji Ikeda 1112 Shinnohara, Tomioka City, Gunma Prefecture Inside Yokoo Tomioka Plant Co., Ltd. (72) Inventor Kazuhiro Fujimoto 1112 Shinnohara, Tomioka City, Gunma Prefecture Yokoo Tomioka Plant Co., Ltd. F term (reference) 5J046 AA04 AA07 AA09 AB06 MA09 TA05 TA09 5J047 AA04 AA07 AA09 AB06 EA01 EA04

Claims (2)

[Claims] 1. A capacitor grounding plate is electrically connected to an outer conductor of a coaxial cable for transmitting a signal through a short conductive connecting plate near a base end of a monopole antenna. An in-vehicle antenna device characterized by being configured to be adhered and fixed with a tape. 2. The vehicle-mounted antenna device according to claim 1, wherein the monopole antenna is disposed and fixed to a rear window glass of an automobile along an edge, and the capacitive ground plate is attached to the body around the rear window. An in-vehicle antenna device characterized by being adhered and fixed.