Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
2000-03-21
2001-07-17
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S702000
Reexamination Certificate
active
06262683
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to circularly polarized wave antennas for transmitting/receiving circularly polarized radio waves and wireless apparatus using the same.
2. Description of the Related Art
In
FIG. 12A
, an example of a conventional circularly polarized wave antenna included in a wireless apparatus is schematically shown. In
FIG. 12B
, a sectional view taken along the line a—a of
FIG. 12A
is shown. A circularly polarized wave antenna
1
shown in
FIGS. 12A and 12B
includes a dielectric member
2
of a rectangular prism shape. On the top surface of the dielectric member
2
, a circular radiative electrode
3
is formed. Also, the dielectric member
2
is provided with through holes from the top surface to the bottom surface. Feed pins P are inserted into the through holes. The feed pins P are formed such that electrical power is supplied thereto from the outside. When electrical power is supplied from the outside to the radiative electrode
3
through the feed pins P, the radiative electrode
3
is excited in, for example, two directions, i.e., the a—a axis direction and the b—b axis direction (specifically, the direction intersecting the a—a axis direction at an angle of 45°), as shown in FIG.
12
A.
The circularly polarized wave antenna
1
shown in
FIGS. 12A and 12B
can transmit/receive circularly polarized radio waves by exciting the radiative electrode
3
, as described above.
With the construction shown in
FIGS. 12A and 12B
, when the relative dielectric constant of the dielectric member
2
is increased so as to miniaturize the circularly polarized wave antenna
1
, and therefore the dielectric member
2
, the axial ratio deteriorates when the circularly polarized wave antenna
1
is operated in a higher mode.
As described above, the circularly polarized wave antenna
1
is structured such that the radiative electrode
3
is excited in two directions meeting at a 45° angle. As shown in
FIGS. 12A and 12B
, when the radiative electrode
3
is formed on the top surface of the rectangular-prism dielectric member
2
, for example, a spacing d
1
in the a—a axis direction between an outer peripheral edge of the dielectric member
2
and an edge of the radiative electrode
3
is greater than a spacing d
2
in the b—b axis direction between an outer peripheral edge of the dielectric member
2
and an edge of the radiative electrode
3
. Hence, the spacing between the outer peripheral edge of the dielectric member
2
and the edge of the radiative electrode
3
is different for each excitation direction of the radiative electrode
3
. As described above, when the relative dielectric constant of the dielectric member
2
is high, the difference in the spacing causes differences in edge effects, thus failing to match the resonant frequencies of the two excitation directions in the radiative electrode
3
. As a result, a problem arises in that the axial ratio deteriorates when the circularly polarized wave antenna
1
is operated in a higher mode.
The circularly polarized wave antenna shown in
FIGS. 12A and 12B
is structured such that electrical power is supplied to the discharge electrode
3
using the feed pins P so as to excite the discharge electrode
3
. When the feed pins P are used in this manner, it is difficult to match the resonant frequencies of the two excitation directions in the radiative electrode
3
.
In addition, the circularly polarized wave antenna shown in
FIGS. 12A and 12B
has problems as described below. A circuit board on which the circularly polarized wave antenna
1
is to be mounted is provided with a circuit section for driving the circularly polarized wave antenna
1
. In order to miniaturize the circuit board, the circuit section is occasionally disposed on the surface opposite to the surface on which the circularly polarized wave antenna
1
is to be mounted. In the circularly polarized wave antenna
1
shown in
FIGS. 12A and 12B
, the feed pins P are disposed near the center of the dielectric member
2
. As described above, when the circuit section is provided on the opposite side of the circuit board, it is difficult to satisfactorily provide a conductive connection between the feed pins P of the circularly polarized wave antenna
1
and the circuit section. Also, patterning of the circuit section is difficult.
SUMMARY OF THE INVENTION
To overcome the above described problems, preferred embodiments of the present invention provide a circularly polarized wave antenna capable of operating in a higher mode and a wireless apparatus comprising the same.
One preferred embodiment of the present invention provides a circularly polarized wave antenna for transmitting/receiving circularly polarized radio waves by a radiative electrode disposed on a dielectric member, wherein the dielectric member is substantially cylindrical; the radiative electrode has a substantially circular shape, which is similar to the shape of a top surface of the dielectric member, and is disposed on the top surface of the dielectric member; a spacing between an outer peripheral edge of the top surface of the dielectric member and an edge of the radiative electrode is formed so as to be substantially the same around the entirety of the outer peripheral edge of the dielectric member; the circularly polarized wave antenna excites a higher mode; and
a feed electrode, which supplies electrical power to the radiative electrode by capacitive coupling, is disposed on a side of said dielectric member.
In the above described circularly polarized wave antenna, a feed-electrode-disposing region on the side of the dielectric member may be formed to be planar; and the feed electrodes may be disposed on the plane.
In the above described circularly polarized wave antenna, the edge of the radiative electrode may be disposed inside the outer peripheral edge of the top surface of the dielectric member; and the feed electrodes may be disposed in a region between the outer peripheral edge of the dielectric member and the edge of the radiative electrode on the top surface of the dielectric member while being separated from the radiative electrode.
According to the above described structure and arrangement, a dielectric member is substantially cylindrical, and a substantially-circular radiative electrode, which is similar to a top surface of the dielectric member, is disposed on the top surface of the dielectric member. Therefore, the spacing between an outer peripheral edge of the top surface of the dielectric member and an edge of the radiative electrode is substantially the same around the entire periphery. When the circularly polarized wave antenna is operated in a higher mode, differences in edge effects are prevented from occurring, and the resonant frequencies of two excitation directions in the radiative electrode are thereby matched. Therefore, circularly polarized radio waves in a higher mode are ensured to be transmitted/received by the radiative electrode. Furthermore, the axial ratio in a higher mode is improved, and a bandwidth in the higher mode is sufficiently broadened.
In a circularly polarized wave antenna in which feed electrodes are disposed on a side or a top surface of the substantially-cylindrical dielectric member, trimming of the feed electrodes is easy. Thus, shifting in the resonant frequencies of the excitation in the radiative electrode, which results from print quality of the feed electrodes, can be easily adjusted by trimming the feed electrodes. In particular, when the feed electrodes are formed on the top surface of the dielectric member, the feed electrodes can be trimmed in an easier manner. As described above, since the trimming of the feed electrodes is easily performed, the resonant frequencies of the two excitation directions in the radiative electrode can be matched more accurately. Thus, a sensitive circularly polarized wave antenna can be provided.
In a circularly polarized wave antenna in which a feed-electrode-disposing region on the side of the dielectric member is made planar and th
Itoh Shigekazu
Kawahata Kazunari
Clinger James
Murata Manufacturing Co. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
Wong Don
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