Information
-
Patent Grant
-
6445358
-
Patent Number
6,445,358
-
Date Filed
Thursday, March 1, 200123 years ago
-
Date Issued
Tuesday, September 3, 200222 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Brinks Hofer Gilson & Lione
-
CPC
-
US Classifications
Field of Search
US
- 343 828
- 343 711
- 343 712
- 343 713
- 343 702
- 343 872
- 343 700 MS
-
International Classifications
-
Abstract
An antenna includes a radiation conductor unit constructed with a plurality of radiation conductors having different lengths which extend in parallel to each other from an electricity-supplying conductor and a grounded conductor unit which opposes said plurality of radiation conductor in an approximately parallel manner with a predetermined distance therebetween. The radiation conductor unit and the grounded conductor unit are contained in an insulating casing constructed by a pair of cases which is fixed to each other. The casing is provided with a plurality of projections for positioning the radiation conductor unit and the grounded conductor unit.
Description
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.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is an exploded perspective view of an antenna according to a first embodiment of the present invention;
FIGS. 2A and 2B
are explanatory drawings showing a manner in which the displacement of the radiation conductor unit shown in
FIG. 1
is restrained;
FIGS. 3A and 3B
are explanatory drawings showing a manner in which a radiation conductor unit of an antenna according to a second embodiment of the present invention is installed;
FIG. 4
is an exploded perspective view of an antenna according to a third embodiment of the present invention;
FIG. 5
is a perspective view of a conventional on-board antenna; and
FIGS. 6A and 6B
are side views of a vehicle showing manners in which the conventional on-board antenna is mounted.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiments of the present invention will be described below in conjunction with the accompanying drawings.
FIG. 1
is an exploded perspective view of an antenna
10
according to a first embodiment of the present invention. The antenna
10
includes a casing which is constructed by fixing a first case
11
a
and a second case
11
b
together, a radiation conductor unit
12
, and a grounded conductor unit
14
. The radiation conductor unit
12
and the grounded conductor unit
14
are installed in the casing, and are supplied with electricity via a coaxial cable
15
which is led out from the casing.
The first and the second cases
11
a
and
11
b
are constructed of an insulating and heat-resistant material such as ABS plastic. The first case
11
a
has the shape of an open container, and the second case
11
b
has the shape of an inverted open container. In the first embodiment, the first case
11
a
functions as a main case, and the second case
11
b
functions as a cover. Five fixing projections
17
a
to
17
e
and a pair of struts
18
are formed on the inwardly facing bottom surface of the first case
11
a.
The struts
18
are provided with restraining projections
19
on the upper side thereof, and each of the restraining projections
19
has a thinned portion
19
a
as shown in FIG.
2
B. In addition, a semicircular tube
11
c
is formed at the upper edge of an end surface of the first case
11
a,
and a semicircular tube
11
d
is formed at a lower edge of an end surface of the second case
11
b.
The radiation conductor unit
12
includes a first radiation conductor
12
a,
a second radiation conductor
12
b,
and an electricity-supplying conductor
13
. The radiation conductors
12
a
and
12
b
have different lengths and are arranged in parallel to each other. The electricity-supplying conductor
13
is connected to each of the radiation conductors
12
a
and
12
b
at one longitudinal end thereof. The radiation conductors
12
a
and
12
b
and the electricity-supplying conductor
13
are integrally formed by bending a plate constructed of a highly conductive metal such as Cu, Al, etc. A slit
20
is formed between the first radiation conductor
12
a
and the second radiation conductor
12
b,
and the first radiation conductor
12
a
extends along the slit
20
in a form of a plate. The second radiation conductor
12
b
also extends along the slit
20
in a form of a plate, but is longer than the first radiation conductor
12
a.
The leading end of the second radiation conductor
12
b
is bent in the shape of a bracket. The bottom plate portion of this bracket forms an attachment tab
12
c
having an insertion hole
16
b.
The electricity-supplying conductor
13
is provided with a receiving portion
13
a,
which is electrically connected to an inner conductor
15
a
of the coaxial cable
15
, and an attachment tab
13
b
having an insertion hole
16
a
at the lower side thereof. The receiving portion
13
a
and the attachment tab
13
b
are integrally formed in the shape of a step. The attachment tab
13
b
and the above-described attachment tab
12
c
are formed in the same plane, and are fixed to the inwardly facing bottom surface of the first case
11
a
by inserting the fixing projections
17
a
and
17
b
through the insertion hole
16
a
and
16
b,
respectively.
The grounded conductor unit
14
opposes the first and the second radiation conductors
12
a
and
12
b
in an approximately parallel manner with a predetermined distance therebetween. The grounded conductor unit
14
includes a receiving portion
14
a
and a holding portion
14
b
at one end, which are integrally formed by bending a plate constructed of a highly conductive material such as Cu, Al, etc. The grounded conductor unit
14
is provided with three insertion holes: insertion holes
16
c
and
16
d
at one end, and an insertion hole
16
e
at the other end. The receiving portion
14
a
is provided for electrically connecting an outer conductor
15
b
of the coaxial cable
15
thereto, and is formed in the shape of a bracket so that the outer conductor
15
b
can be inserted therein. The holding portion
14
b
is provided for supporting an insulator
15
c
of the coaxial cable
15
, and is formed in the shape of a bracket so that the insulator
15
c
can be inserted therein. The fixing projections
17
c,
17
d,
and
17
e
are inserted through the insertion holes
16
c,
16
d,
and
16
e,
respectively, to fix the grounded conductor unit
14
to the inwardly facing bottom surface of the first case
11
a.
The coaxial cable
15
is constructed by forming the insulator
15
c
and the outer conductor
15
around the inner conductor
15
a
disposed in the center. The inner conductor
15
a
is connected to the receiving portion
13
a
of the electricity-supplying conductor
13
by soldering, and the outer conductor
15
b
is clamped by the receiving portion
14
a
of the grounded conductor unit
14
. Accordingly, the electricity-supplying conductor
13
and the grounded conductor unit
14
are supplied with electricity through the inner conductor
15
a
and outer conductor
15
b.
In addition, the insulator
15
c
of the coaxial cable
15
is clamped by the holding portion
14
b
of the grounded conductor unit
14
, and the exterior of the coaxial cable
15
is sandwiched by the semicircular tubes
11
c
and
11
d
of the first and the second cases
11
a
and
11
b.
Next, the fabrication process of the antenna
10
having the above-described construction will be explained below. First, the fixing projections
17
a
to
17
e
are respectively inserted through the insertion holes
16
a
and
16
b
formed in the radiation conductor unit
12
and the insertion holes
16
c
to
16
e
formed in the grounded conductor unit
14
. Then, the attachment tabs
12
c
and
13
b
and the grounded conductor unit
14
are fixed to the inwardly facing bottom surface of the first case
11
a
by deforming the ends of the fixing projections
17
a
to
17
e,
by using an adhesive, or by other means.
FIG. 2A
is a plan view of a part of the radiation conductor unit
12
, and
FIG. 2B
is a cross sectional view of
FIG. 2A
along line IIB—IIB. As show in
FIGS. 2A and 2B
, the radiation conductors
12
a
and
12
b
are supported by the strut
18
, and the restraining projections
19
are inserted through the slit
20
. Accordingly, the thinned portions
19
a
of the restraining projections
19
are engaged with the edge portions of the radiation conductors
12
a
and
12
b.
Thus, the radiation conductor unit
12
and the grounded conductor unit
14
are positioned and fixed by the fixing projections
17
a
to
17
e.
In addition, the radiation conductors
12
a
and
12
b
are positioned by the struts
18
and the restraining projections
19
. Accordingly, the width of the slit
20
and the distance between the radiation conductors
12
a
and
12
b
and the grounded conductor unit
14
is maintained constant. The coaxial cable
15
is then introduced from the upper side of the first case
11
a.
The outer conductor
15
b
and the insulator
15
c
are inserted into the receiving portion
14
a
and the holding portion
14
b,
respectively. The inner conductor
15
a
at the leading end is put on the receiving portion
13
a,
and the exterior of the coaxial cable
15
is fitted into the semicircular tube
11
c.
Then, the insulator
15
c
is clamped and fixed by the holding portion
14
b,
and the outer conductor
15
b
is clamped and fixed by the receiving portion
14
a.
Thus, the outer conductor
15
b
is electrically and mechanically connected to the grounded conductor unit
14
. The inner conductor
15
a
is soldered on and electrically connected to the receiving portion
13
a.
The outer conductor
15
b
may also be soldered on the receiving portion
14
a
to ensure reliability. In addition, the outer conductor
15
b
and the insulator
15
c
may also be fixed by means other than clamping, for example, by press fitting. Lastly, the opening at the upper side of the first case
11
a
is covered by the second case
11
b
in a manner such that the coaxial cable
15
is led out through the semicircular tubes
11
c
and
11
d.
The first and the second cases
11
a
and
11
b
are then fixed to each other by screws, snaps, an adhesive, or by other means. Accordingly, the fabrication of the antenna
10
containing the radiation conductor unit
12
and the grounded conductor unit
14
in the first and the second cases
11
a
and
11
b
is completed.
In the above-described antenna
10
, multiple resonances occur between the first and the second radiation conductors
12
a
and
12
b
having different lengths and the grounded conductor unit
14
. Accordingly, overall frequency characteristics are improved in a frequency band including multiple resonance frequencies, and the operational bandwidth is increased. In addition, since the first and the second radiation conductors
12
a
and
12
b,
which are arranged in parallel to each other, individually serve as radiators, the size of the antenna
10
is reduced, so that the installation in a vehicle cabin is realized.
As described above, the receiving portions
13
a
of the radiation conductor unit
12
and the receiving portion
14
a
of the grounded conductor unit
14
are disposed in the first case
11
a,
and are covered by the second case
11
b.
In addition, the coaxial cable
15
for supplying electricity is sandwiched by the semicircular tubes
11
c
and
11
d
of the first and the second cases
11
a
and
11
b.
Accordingly, the operation of connecting the coaxial cable
15
is easily performed while the second case
11
b
is removed. In addition, the fixing projections
17
a
to
17
e,
the struts
18
, and the restraining projections
19
are utilized in the process of installing the radiation conductor unit
12
and the grounded conductor unit
14
into the first case
11
a.
The fixing projections
17
a
to
17
e
position and fix the radiation conductor unit
12
and grounded conductor unit
14
. The struts
18
determine the vertical position of the radiation conductors
12
a
and
12
b,
and the restraining projections
19
restrain the displacement of the radiation conductors
12
a
and
12
b
by using the slit
20
. Thus, the radiation conductor unit
12
and the grounded conductor unit
14
are easily installed inside the first case
11
a
at predetermined positions. Accordingly, the antenna
10
is fabricated by a significantly simple process. In addition, the radiation conductor unit
12
and the grounded conductor unit
14
are positioned with high accuracy, so that variation in characteristics of the antenna is reduced.
When the attachment tabs
12
c
and
13
b
are formed not in a horizontal manner but in an inclined manner toward the lower side, the insertion holes
16
a
and
16
b
and the fixing projections
17
a
and
17
b
are not necessary for positioning and fixing the radiation conductor unit
12
. In such a case, the radiation conductor unit
12
is installed in the first case
11
a
by pressing the attachment tabs
12
c
and
12
b
against the inwardly facing bottom surface of the first case
11
a.
At this time, the edge portions of the radiation conductors
12
a
and
12
b
are fitted into the thinned portions
19
a
of the restraining projections
19
, while the attachment tabs
12
c
and
12
b
are deformed. Accordingly, the radiation conductors
12
a
and
12
b
are pressed upward against the top portion of the restraining projections
19
by an opposing force generated by the attachment tabs
12
c
and
13
b.
Thus, the radiation conductors
12
a
and
12
b
and the receiving portion
13
a
are positioned and supported at predetermined positions.
FIGS. 3A and 3B
show a part of an antenna according to a second embodiment of the present invention. According to the second embodiment, a second case
11
b,
which functions as a cover, is provided with a plurality of projections for positioning the radiation conductors
12
a
and
12
b
of the radiation conductor unit
12
. These projections include three restraining projections
31
, which are disposed so as to abut against the peripheral edges of the radiation conductors
12
a
and
12
b,
and one of two screw-receiving portions
32
, which are used for fixing the second case
11
b
to the first case
11
a
(not shown) by screws. As shown in
FIG. 3B
, one of the screw-receiving portions
32
is disposed at an end of the slit
20
. This screw-receiving portion
32
serves to position the radiation conductors
12
a
and
12
b,
and is designed so as to abut against the end surface of the first radiation conductor
12
a
and on the side surface of the second radiation conductor
12
b.
Since the restraining projections
31
and one of the screw-receiving portions
32
abut against a plurality of positions in the peripheral edges of the radiation conductors
12
a
and
12
b,
the displacement of the radiation conductors
12
a
and
12
b
is restrained and the positioning accuracy is increased. In addition, one of the screw-receiving portions
32
, which are necessary for fixing the first and the second cases to each other, is also used for positioning the radiation conductors
12
a
and
12
b.
Thus, the number of projections which exclusively serve to position the radiation conductors
12
a
and
12
b
is reduced.
When the second case
11
b
is capable of positioning the radiation conductors
12
a
and
12
b
as described above, there is no need to provide the struts
18
and restraining projections
19
in the first case
11
a
as shown in
FIGS. 1 and 2
. The attachment tabs
12
c
and
12
b
of the radiation conductor unit
12
and the grounded conductor unit (not shown in FIGS.
3
A and
3
B), however, are fixed to the inwardly facing bottom surface of the first case in a similar manner as described in the first embodiment. Thus, the fixing projections
17
a
to
17
e
shown in
FIG. 1
are still necessary.
FIG. 4
is an exploded perspective view of an antenna
40
according to a third embodiment. The antenna
40
differs from the antenna
10
of the first embodiment shown in
FIG. 1
in the following point. That is, the antenna
40
includes three struts
41
a
to
41
c
which are provided with positioning projections
42
a
to
42
c,
respectively, on the upper surfaces thereof. The positioning projections
42
a
to
42
c
are inserted into insertion holes
21
a
to
21
c,
respectively, which are formed in the radiation conductors
12
a
and
12
b
of the radiation conductor unit
12
. With reference to
FIG. 4
, the radiation conductor unit
12
is positioned and fixed on the inwardly facing bottom surface of the first case
11
a
by inserting the fixing projections
17
a
and
17
b
into the attachment tabs
12
c
and
13
b.
At this time, the first radiation conductor
12
a
is supported by the strut
41
a
in a manner such that the positioning projection
42
a
is inserted through the insertion hole
21
a.
Similarly, the second radiation conductor
12
b
is supported by the struts
41
b
and
41
c
in a manner such that the positioning projections
42
b
and
42
c
are inserted through the insertion holes
21
b
and
21
c,
respectively. Thus, the radiation conductors
12
a
and
12
b
are positioned with high accuracy, so that variation in characteristics of the antenna is reduced.
The grounded conductor unit
14
of the third embodiment has a different shape compared to that in the first embodiment. As shown in
FIG. 4
, the grounded conductor unit
14
of the antenna
40
is designed so as to be positioned and fixed on the inwardly facing bottom surface of the first case
11
a
in a manner such that fixing projections
17
f
and
17
g
are inserted through insertion holes
16
f
and
16
g.
In addition, the grounded conductor unit
14
is positioned directly below the slit
20
between the radiation conductors
12
a
and
12
b.
Other parts of the antenna
40
shown in
FIG. 4
have the same constructions as those described in the first embodiment. Thus, components corresponding to those shown in
FIG. 1
are denoted by the same reference numerals, and redundant explanations are thus omitted.
Claims
- 1. An antenna comprising: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 said electricity-supplying conductor; a grounded conductor unit which opposes said plurality of radiation conductors in an approximately parallel manner with a predetermined distance therebetween; an insulating casing which contains said radiation conductor unit and said grounded conductor unit; and a plurality of projections in an inwardly facing surface of said insulating casing for positioning said radiation conductor unit and said grounded conductor unit.
- 2. The antenna according to claim 1, wherein said radiation conductor unit includes two radiation conductors which are arranged in parallel to each other with a slit therebetween, and wherein one or more of said projections are inserted into said slit and are engaged with each of said two radiation conductors.
- 3. The antenna according to claim 1, wherein one or more of said projections abut against the peripheral edges of said plurality of radiation conductors.
- 4. The antenna according to claim 1, wherein one or more of said projections are provided with a thinned portion for restraining the displacement of said plurality of radiation conductors in the thickness direction by fitting said plurality of radiation conductors on said thinned portions.
- 5. The antenna according to claim 1, wherein said insulating casing is constructed by fixing a pair of cases to each other with screws, and wherein one or more of said projections serve as screw-receiving portions.
Priority Claims (1)
| Number |
Date |
Country |
Kind |
| 2000-065156 |
Mar 2000 |
JP |
|
US Referenced Citations (5)
| Number |
Name |
Date |
Kind |
| 5365246 |
Rasinger et al. |
Nov 1994 |
A |
| 5898404 |
Jou |
Apr 1999 |
A |
| 6310586 |
Takahashi et al. |
Oct 2001 |
B1 |
| 6333714 |
Takahashi |
Dec 2001 |
B1 |
| 6339402 |
Mckivergan |
Jan 2002 |
B1 |
Foreign Referenced Citations (2)
| Number |
Date |
Country |
| 5-029821 |
Feb 1993 |
JP |
| 2000-040908 |
Feb 2000 |
JP |
