Communications: radio wave antennas – Antennas – With radio cabinet
Reexamination Certificate
2002-09-17
2004-04-27
Wilmer, Michael C. (Department: 2821)
Communications: radio wave antennas
Antennas
With radio cabinet
C343S826000
Reexamination Certificate
active
06727858
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Detailed Description of the Invention
The present invention relates to a circularly polarized wave antenna for use in communication between a stationary satellite and a movable body.
2. Description of the Prior Art
Since in a system for communicating with the stationary satellite or receiving satellite broadcasting in a movable body such as an automobile, a circularly polarized wave is mainly used, there is desired a small-sized circularly polarized wave antenna through which an excellent circularly polarized wave can be obtained within a wide range of angle of elevation.
FIG. 6
shows a conventional example of this sort of circularly polarized wave antenna, and
FIG. 6A
is a perspective view showing a circularly polarized wave antenna; and
FIG. 6B
is a side view showing the circularly polarized wave antenna. This circularly polarized wave antenna
101
is composed of a ground plate
102
and four conductors
103
. These conductors
103
are obtained by extending a central conductor of a coaxial cable
104
. Also, an outer conductor of the coaxial cable
104
is soldered to the ground plate
102
at a soldered point
105
as shown. Accordingly, each conductor
103
is fixed onto the ground plate
102
like a cantilever. Also, each conductor
103
is arranged on the ground plate
102
at regular intervals d, and inclines at a predetermined angle &agr; in the same direction respectively.
In the circularly polarized wave antenna
101
constituted as described above, electric power is fed to those four conductors
103
in phase to create a phase difference of 90° in space, whereby the main beam faces a certain angle of elevation, a circularly polarized wave can be emitted in that direction, and further a pattern of a conical surface at the angle of elevation becomes non-directional. In other words, the directivity of the circularly polarized wave antenna
101
becomes as shown in
FIG. 7
even if viewed from any of the azimuth angle directions, and if the stationary satellite
107
is positioned on an extension line of an oblique line
106
, the directivity of the circularly polarized wave antenna
101
can always be directed toward the stationary satellite
107
in whichever direction the movable body equipped with the circularly polarized wave antenna
101
may advance. In this case, when the target angle of elevation is within, for example, a range of 30° to 60°, if an angle of inclination a of the conductor
103
is set to about 45°, the length L of the conductor
103
is set to about 0.65 &lgr;
0
, an interval d between two conductors
103
in opposite to each other is set to about 0.33 &lgr;
0
, then the optimum directivity to the angle of elevation can be obtained (where &lgr;
0
is free space wave length of the radio wave for use)
Since the above-described conventional circularly polarized wave antenna
101
has been constructed such that four conductors
103
which have been inclined by about 45° are arranged on the ground plate
102
at a regular interval d so as to feed electric power to each conductor
103
in phase, there is no need for any automatic phase shifter and the like on feeding electric power and there is an advantage that the structure can be simplified. However, the structure is not without its problems. More specifically, since four conductors
103
(about 0.65 &lgr;
0
in length) inclined by about 45° are arranged at a regular interval d (about 0.33 &lgr;
0
), the overall dimension of the circularly polarized wave antenna
101
becomes 0.33 &lgr;
0
×0.33 &lgr;
0
×0.46 &lgr;
0
, when the frequency for use is, for example, 2.3 GHz (&lgr;
0
=130 mm), becomes as large as up to about 43×43×60 (mm), and miniaturization as a vehicle-mounted antenna cannot be realized. Also, since each conductor
103
is only fixed onto the ground plate
102
in a cantilever shape and has low mechanical strength, there is a problem that the interval between each conductor
103
fluctuates because of vibration of the automobile to deteriorate the antenna characteristics or great stress is applied to a soldered point
105
of an outer conductor of the coaxial cable
104
to cause a poor connection.
SUMMARY OF THE INVENTION
The present invention has been achieved in views of the prior art as such, and is aimed to provide a circularly polarized wave antenna at low prices which is suitable for miniaturization and is also resistant to vibrations.
As solution means for achieving the above-described object, there is provided a circularly polarized wave antenna, according to the present invention, having four flat plate-shaped dielectrics having the substantially same thickness vertically provided on a printed substrate and arranged in a square-cylinder shape as a whole, and four radiation conductors provided on each outer wall surface of these flat plate-shaped dielectrics inclined in a fixed direction, characterized in that the structure is arranged such that a lower end of each of the above-described radiation conductors is electrically connected to the printed substrate and such that electric power is fed to these four radiation conductors in phase.
In a circularly polarized wave antenna constructed as described above, since there are provided radiation conductors on each outer wall surface of four flat plate-shaped dielectrics arranged in a square cylinder shape, a mechanical orthogonal relationship of each radiation conductor is retained so that not only deterioration in the antenna characteristics and the poor connection resulting from external vibrations can be reduced but also the required length of the radiation conductor becomes short by a shortened wavelength due to the flat plate-shaped dielectric having high specific inductive capacity, and as a result, substantial miniaturization can be realized. Also, since the flat plate-shaped dielectric is not likely to unevenly contract in a calcination process during manufacture, it is also easy to perform fine adjustment of the plate thickness and the like by polishing after the calcination, it becomes easy to prevent variations in the antenna characteristics resulting from dimensional error or the like. Further, since it is easy to print the radiation conductor on a flat surface which serves as the outer wall surface of the flat plate-shaped dielectric, not only is it possible to easily form a desired radiation conductor by raising the printing precision but also it is possible to collectively print and form the radiation conductor on a multiplicity of flat plate-shaped dielectrics having the substantially same thickness. Therefore, the printing cost can be significantly reduced.
Also, if, in the above-described structure, of a pair of flat plate-shaped dielectrics adjacent substantially at right angles, a protrusion for protruding from the side of one flat plate-shaped dielectric by a portion corresponding to the plate thickness is fitted into a recess obtained by cutting a portion corresponding to the plate thickness in the side of the other flat plate-shaped dielectric, it will be possible to combine four flat plate-shaped dielectrics having the same width dimension in a square-cylinder shape at a layout of a substantial square. Therefore, it becomes easier to design and perform an assembly operation.
Further, if, in the above-described structure, those four flat plate-shaped dielectrics are all of the same shape, the manufacturing cost can also be significantly reduced. In this case, if an upper half of one side and a lower half of the other side of the flat plate-shaped dielectric are cut by a portion corresponding to the plate thickness along the direction of the width, it is possible to adopt a structure preferable in design in which a protrusion of one flat plate-shaped dielectric adjacent substantially at right angles is fitted into a recess in the other flat plate-shaped dielectric whereby four flat plate-shaped dielectrics are combined in a square-cylinder shape in a layout of a square as well as it is possible to remarkably enhance the dimensional precisi
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Wilmer Michael C.
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