Communications: radio wave antennas – Antennas – With radio cabinet
Reexamination Certificate
2002-06-28
2004-08-03
Wimer, Michael C. (Department: 2821)
Communications: radio wave antennas
Antennas
With radio cabinet
C343S7000MS
Reexamination Certificate
active
06771223
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an antenna device and portable equipment, and more particularly, to an antenna device and portable equipment capable of reducing a size and weight thereof.
BACKGROUND ART
In recent years, a portable telephone has been widely spread. In mobile communication to use this portable telephone or the like, transmission waves are subjected to multi-reflection or scattering caused by buildings or the like present between a portable telephone as a mobile station and a base station. For this reason, polarization fluctuation of radio waves and others occur, resulting in level fluctuation of a received signal in a portable telephone and in turn, in deterioration in communication quality. In order to alleviate such deterioration in communication quality, there has been employed the diversity reception in which radio waves are received using two antennae and received signals through the antennae are synthesized or one thereof at a higher level is selected, thereby alleviating an influence of level fluctuation on a received signal.
FIG. 14
is a view showing a conventional portable telephone in a simplified manner. Description will be given of the conventional portable telephone with reference to FIG.
14
.
Referring to
FIG. 14
, a portable telephone
101
adopts a so-called space diversity reception scheme as a measure to alleviate the deterioration in communication quality, including: two antennae of a whip antenna
150
; and a built-in antenna
151
such as a flat plate antenna mounted inside a case of portable telephone
101
.
In portable telephone
101
shown in
FIG. 14
, since antenna
150
and built-in antenna
151
for transmitting/receiving radio waves in the same band are installed adjacent to each other, a problem has been arisen that antenna
150
and built-in antenna
151
are electromagnetically coupled with each other to deteriorate an efficiency of the antenna.
Furthermore, as another type of the diversity reception, there has also been known a so-called polarization diversity reception scheme using a patch antenna.
FIGS. 15 and 16
are model diagrams each showing an antenna device adopting a polarization diversity reception scheme.
Referring to
FIG. 15
, a patch antenna
152
is mounted on a board
103
. Feed points
105
a
and
105
b
connected to a feed source are provided on adjacent sides of the periphery of patch antenna
152
. By switching between feed points
105
a
and
105
b
, a plane of polarization of the patch antenna can be changed over from one of two directions indicated by two arrow marks
153
and
154
to the other. Moreover, as shown in
FIG. 16
, in the patch antenna
152
, by switching between ground points
114
a
and
114
b
instead of feed points, switching between planes of polarization can also be realized. Referring to
FIG. 16
, ground points
114
a
and
114
b
grounding patch antenna
152
to the board are provided on adjacent side of a periphery of patch antenna
152
. Furthermore, a feed point
105
connected to a feed source is provided on patch antenna
152
.
Since such a patch antenna has a large antenna size, however, it, as was in the prior art, has been hard to be applied to portable equipment such as a portable telephone requiring reduction in size and weight.
As described above, in portable equipment such as a portable telephone requiring reduction in size and weight, it has been hard to suppress deterioration in communication quality without reducing an efficiency of an antenna.
The present invention has been made in order to solve such a problem and it is an object of the present invention to provide an antenna device and portable equipment capable of reducing a size and weight thereof and preventing deterioration in communication quality to be otherwise caused by polarization fluctuation of a radio wave and others without decreasing an antenna efficiency.
DISCLOSURE OF THE INVENTION
An antenna device in a first aspect of the present invention includes: a conductive board having one end portion and the other end portion opposite the one end portion; a flat plate antenna; first current direction change means; and second current direction change means. The flat plate antenna is mounted on the board with a dielectric interposing therebetween and when feeding a current thereto to excite, a current also flows in the board. The first current direction change means changes a direction of the current flowing in the board to a first direction when exciting said antenna and located on the one end portion of the board. The second current direction change means changes a direction of the current flowing in the board to a second direction different from the first direction when exciting the antenna and located on the other end portion of the board.
With such a construction adopted, directions of a strength of a radio wave radiated from the antenna device including the antenna and the board can be changed therebetween in respective cases where a direction of a current flowing in the board is the first direction and where a direction of a current flowing in the board is the second direction. That is, the directivity of the antenna can be changed. Here, the first direction is, for example, a direction along a diagonal line extending from the one end portion of the board to the opposite corner of the board and the second direction is exemplified as a direction along a diagonal line extending from the other end portion of the board to the opposite corner of the board. Furthermore, since a direction of the current flowing in the board is different according to the first direction or the second direction, a main polarization direction of the antenna device in each of the respective cases is different from that in the other cases. That is, by changing a direction of current flowing in the board from the first direction to the second direction and vice versa, directivity and a polarization direction of the antenna device can be changed. Therefore, an antenna device can be realized that operates as if it had two antennae different in directivity and polarization from each other using one antenna. As a result, the diversity reception can be implemented using one antenna. Accordingly, since no necessity arises for two antennas, which was required in a conventional practice, thereby preventing from occurrence of a problem of electromagnetic coupling between two antennas.
Furthermore, since functions of two antennas are realized with one antenna, a size and weight of an antenna device can be reduced compared with those in a case where two separate antennas are installed.
In the antenna device according to the above first aspect, the antenna may be installed so as to extend from a position on the one end portion of the board to a position on the other end portion of the board. The first current direction change means may include first feed means, which is connected to one portion of the antenna located on the one end portion of the board, for exciting the antenna and first feed control means for controlling feed of a current to the antenna from the first feed means. The second current direction change means may include second feed means, which is connected to another portion of the antenna located on the other end portion of the board, for exciting the antenna and second feed control means for controlling feed of a current to the antenna from the second feed means.
In this case, by switching between the first and second feed means using the first and second feed control means, a position of a feed point of the antenna can be changed over from a position in the one portion of the antenna to a position in the second portion of the antenna. By switching between positions of feed points in this way, a direction of the current flowing in the board can be easily changed over from the first direction to the second direction and vice versa. As a result, since an antenna device can be realized that operates as if it had two antennas different in directivity and polarization from each other using one antenna, the diver
Fukasawa Toru
Imanishi Yasuhito
Ohmine Hiroyuki
Shoji Hideaki
Mitsubishi Denki & Kabushiki Kaisha
Wimer Michael C.
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