Communications: radio wave antennas – Antennas – Fractional – multiple – or full wave length linear type
Reexamination Certificate
2001-03-01
2002-09-03
Le, Hoanganh (Department: 2821)
Communications: radio wave antennas
Antennas
Fractional, multiple, or full wave length linear type
C343S702000, C343S7000MS, C343S713000, C343S872000
Reexamination Certificate
active
06445358
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to antennas, and more particularly relates to an on-board antenna used for receiving terrestrial television broadcast signals, etc.
2. Description of the Related Art
A conventional on-board antenna
50
for receiving terrestrial television broadcast signals is shown in FIG.
5
. This conventional antenna
50
includes a rod-shaped radiation conductor
51
which is adjusted so as to resonate at a desired frequency. The angle between the radiation conductor
51
and a pedestal
52
is freely adjusted by inclining a supporting portion
53
relative to the pedestal
52
. As shown in
FIGS. 6A and 6B
, this antenna
50
is attached on a rear window
61
or on a roof
62
of a vehicle
60
.
Generally, to solve the problem of fading, which particularly occurs when signals are received by a moving antenna, a diversity receiving system is adopted in vehicles. In this system, a plurality of the antennas shown in
FIG. 5
are used, and one of the antennas which exhibits the highest receiving level is selected.
With respect to the conventional antennas as described above, the operational bandwidth of a single antenna is not sufficiently wide. Thus, when a wide bandwidth must be covered, as in a case of receiving television broadcast signals, multiple antennas having different operational bandwidths are prepared. In addition, external circuits such as tuning circuits and amplifying circuits are attached. Accordingly, there has been a problem in that a considerably high total cost is incurred to obtain a wide operational bandwidth. In addition, since a plurality of antennas, each of which is relatively large, is used, the antennas are necessarily attached to the exterior of the vehicle. Thus, there are risks in that the antennas will be damaged or stolen. In addition, there is a problem in that the appearance of the vehicle is degraded.
SUMMARY OF THE INVENTION
In consideration of the above-described situation of the conventional technique, an object of the present invention is to provide an inexpensive and compact wideband antenna which is mountable in a vehicle cabin, which is fabricated by a simple process, and which causes small variation in characteristics.
To this end, an antenna of the present invention comprises a radiation conductor unit including an electricity-supplying conductor and a plurality of radiation conductors having different lengths which extend in parallel to each other from the electricity-supplying conductor; a grounded conductor unit which opposes the radiation conductors in an approximately parallel manner with a predetermined distance therebetween; an insulating casing which contains the radiation conductor unit and the grounded conductor unit; and a plurality of projections in an inwardly facing surface of the insulating casing for positioning the radiation conductor unit and the grounded conductor unit.
According to the antenna which is constructed as described above, multiple resonances occur between the radiation conductors having different lengths and the grounded conductor unit. Accordingly, overall frequency characteristics are improved in a frequency band including multiple resonance frequencies, and the operational bandwidth is increased. In addition, since the radiation conductors arranged in parallel to each other individually serve as radiators, the size of the antenna is reduced compared to conventional dipole antennas, so that the installation in a vehicle cabin is realized. In addition, since the projections for positioning the radiation conductors and the grounded conductor unit are provided on the inwardly facing surface of the casing, the radiation conductors and the grounded conductor unit are easily mounted at predetermined positions in the casing. Accordingly, fabrication process is simplified and variation in characteristics is reduced.
The radiation conductor unit may include two radiation conductors which are arranged in parallel to each other with a slit therebetween. Preferably, in such a case, one or more of the projections are inserted through the slit and are engaged with each of the radiation conductors. Accordingly, the risk is reduced in which the radiation conductors will be excessively close to each other and the characteristics of the antenna will be degraded.
One or more of the projections preferably abut against the peripheral edges of the radiation conductors at a plurality of positions. Accordingly, displacement of the radiation conductors is restrained, so that the positioning accuracy is increased.
One or more of the projections are preferably provided with a thinned portion for restraining the displacement of the radiation conductors in the thickness direction by fitting the radiation conductors on the thinned portion. Accordingly, the distance between the radiation conductors and the grounded conductor unit may be maintained constant.
Preferably, the insulating casing is constructed by fixing a pair of cases to each other with screws, and one or more of said projections serve as screw-receiving portions. Accordingly, number of projections which exclusively serve for positioning the radiation conductors is reduced, and the positioning accuracy is increased.
REFERENCES:
patent: 5365246 (1994-11-01), Rasinger et al.
patent: 5898404 (1999-04-01), Jou
patent: 6310586 (2001-10-01), Takahashi et al.
patent: 6333714 (2001-12-01), Takahashi
patent: 6339402 (2002-01-01), Mckivergan
patent: 5-029821 (1993-02-01), None
patent: 2000-040908 (2000-02-01), None
Ikeda Tomoki
Takahashi Toshiyuki
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Le Hoang-anh
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