Communications: radio wave antennas – Antennas – With vehicle
Reexamination Certificate
2000-11-09
2002-04-09
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
With vehicle
C343S711000
Reexamination Certificate
active
06369767
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to glass antennas for vehicles, and in particular to glass antennas applied to side glasses or rear glasses of vehicles.
2. Description of the Related Art
Glass antennas in which antenna conductors are formed on a vehicle window glass are superior to conventional rod antennas in that (i) they are designed not to protrude outward, (ii) there is little danger of breakage, and (iii) they do not cause wind noise. For these and other reasons, such glass antennas are widely used.
For example, JP H9-284025A discloses a vehicle glass antenna that is applied to a side glass. With this antenna, a glass antenna is proposed in which the receiving gain is increased over a broad spectrum from FM radio broadcasts to UHF TV broadcasts, while occupying only a little space. The specific antenna pattern is shown in FIG.
9
A. One pattern
15
that is disclosed is an antenna pattern including a first horizontal line
151
extending substantially horizontally from a feeding point, a bend portion
152
bending away from the first horizontal line
151
, and a second horizontal line
153
extending from the bend portion and substantially parallel to the first horizontal line
151
.
Also JP H9-116327A (see
FIG. 9B
) and JP H10-51219A (see
FIG. 9C
) disclose glass antennas
15
having a bend portion
152
and linear portions
151
and
153
that are arranged substantially in parallel.
With regard to high frequency antennas, and in particular glass antennas for car telephones, for example JP H11-17429A and JP H11-127011A disclose glass antennas, in which antenna conductors, feeding points and grounding points are provided on an automobile window glass.
However, all of the antenna patterns disclosed in JP H9-284025A, JP H9-116327A and JP H10-51219A are monopole antennas.
These monopole antennas have an impedance that is lower than the characteristic impedance of the antenna's feeder cable (coaxial cable). Therefore, this impedance mismatch with the feeder cable causes a loss in the receiving sensitivity. As a countermeasure, these conventional antennas often use impedance matching circuits.
However, such impedance matching circuits are also a reason for additional cost.
SUMMARY OF THE INVENTION
It is an object of the present invention to solve these problems and to provide a glass antenna having an impedance that is close to the characteristic impedance of the antenna's feeder cable, even when an impedance matching circuit is not provided.
It is another object of the present invention to provide a VHF band glass antenna that can be arranged on a small space.
The design considerations of the present invention for attaining these objects are as follows.
A glass antenna that can receive the VHF band (specifically, frequencies of 76 to 108 MHz) is provided, for example, on a side glass of a vehicle. If the design frequency is taken as, for example, 90 MHz (&lgr;/4≈0.83 m), then it often can not be fitted onto the side glass as a straight pattern.
Therefore, the antenna pattern is bent into a so-called bent antenna. However, this lowers the impedance of the antenna, as explained above. But by connecting the antenna with ground, the impedance of the antenna pattern is increased and brought closer to the impedance of the feeder cable.
This also can be thought of as making a monopole antenna of a bent dipole antenna.
Thus, in accordance with the present invention, a vehicle glass antenna includes a VHF band antenna provided on a window glass of a vehicle. The VHF band antenna includes an antenna pattern, a grounding point and a feeding point for the VHF band antenna. The antenna pattern includes a first element extending substantially straight, a bend portion bending away from the first element, and a second element that is substantially parallel to the first element extending from the bend portion. The second element is connected to the ground point.
In the vehicle glass antenna, it is preferable that the feeding point and the grounding point are provided in the vicinity of one side of the window glass.
It is preferable that the feeding point and the grounding point are provided in the vicinity of one corner of the window glass.
It is preferable that the first element of the VHF band antenna is provided with a bypass pattern.
It is preferable that the window glass is a side window glass or a rear window glass.
It is preferable that the window glass is either a fixed window glass or a hinged window glass that can be opened and closed.
It is preferable that the vehicle glass antenna further includes a medium frequency (MF) band antenna. It is preferable that the MF band antenna of the vehicle glass is substantially made of one straight pattern.
It is preferable that a feeding point of the MF band antenna of the vehicle glass antenna of claim
8
is arranged near the feeding point and the grounding point of the VHF band antenna.
REFERENCES:
patent: 5598170 (1997-01-01), Nakase
patent: 5905470 (1999-05-01), Fujii et al.
patent: 6292149 (2001-09-01), Endo et al.
patent: 02000013120 (2000-01-01), None
patent: 2001127519 (2001-05-01), None
Iijima Hiroshi
Oka Hidetoshi
Chen Shih-Chao
Merchant & Gould P,C,
Nippon Sheet Glass Co. Ltd.
Wong Don
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