Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
1999-04-27
2001-01-23
Le, Hoanganh (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S702000, C343S873000
Reexamination Certificate
active
06177908
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a surface-mounting type antenna, an antenna device, and a communication device including the antenna device. More particularly, the present invention relates to a surface-mounting type antenna, an antenna device, and a communication device including the antenna device which are to be used for mobile communication, etc.
2. Description of the Related Art
While the reduction in size and weight of mobile communication devices, particularly portable telephones in recent years is in progress, as for the antennas mounted on them the further reduction in size and weight, and increase in gain have been required.
In
FIGS. 9 and 10
, a conventional surface-mounting type antenna and an antenna device including the antenna device are shown respectively. The structure of the surface-mounting type antenna
30
in
FIG. 9
is shown in Japanese Unexamined Patent Publication No. 10-13139.
In
FIG. 9
, the surface-mounting type antenna
10
is composed of some electrodes disposed on the surface of a base member
11
in the form of a rectangular solid made of a dielectric substance such as ceramics, resin, etc. as one insulating material. First, on the nearly whole surface of a first major surface
11
a
of the base member
11
the grounding electrode
12
is disposed. Further, on a second major surface
11
b
of the base member
11
a strip-like radiation electrode
13
is disposed along the long side of the base member
11
. At a first end of the radiation electrode
13
an open-ended terminal
13
a
is provided, and ta second end is connected to a grounding electrode through a connecting electrode
14
disposed on an side surface
11
c
of the base member
11
. Further, on the second major surface
11
b
of the base member
11
a power-supply electrode
15
located close to the open-ended terminal
13
a
of the radiation electrode
13
is disposed, and the power-supply electrode
15
is connected to a power-supply terminal
16
disposed over an side surface
11
d
to the first major surface
11
a
of the base member
11
.
Here, when the surface-mounting type antenna
10
is mounted on a circuit board (not illustrated) because a power-supply terminal
16
is connected to a power-supply line on the side of the circuit board by soldering, etc., it is called the terminal in order to distinguish that from other electrodes. Hereinafter, when an electrode is described as a terminal, the electrode for connection to a circuit board is meant. However, there are cases in which electrodes and terminals are integrated, and then a part of the electrodes may be used as a terminal.
Next, in the antenna device
1
shown in
FIG. 10
, the surface-mounting type antenna
10
is mounted on the circuit-board grounding electrode
3
in the vicinity of a corner portion of the circuit board
2
. The grounding electrode
12
and power-supply terminal
16
of the surface-mounting type antenna
10
are connected to the circuit-board grounding electrode
3
and power-supply line
4
disposed on the circuit board
2
by soldering, etc. respectively.
Here, in
FIG. 11
, an equivalent circuit of the antenna device
1
in
FIG. 10
is shown. In
FIG. 11
, a capacitor CO represents capacitance produced between the power-supply electrode
15
and the grounding electrode
12
and circuit-board grounding electrode
3
, a capacitor C
1
capacitance between the power-supply electrode
15
and the open-ended terminal
13
a
of the radiation electrode
13
, a capacitor C
2
capacitance between the radiation electrode
13
and the grounding electrode
12
and circuit-board grounding electrode
3
, conductance G a radiation resistor of the surface-mounting type antenna
10
, and an inductance L
1
and resistor R
1
an inductance component and resistance component of the radiation electrode
13
respectively. Further, mark S represents a signal source. The inductance L and resistor R
1
are connected in series, and one end of such is connected to the signal source S through the capacitor C
1
and the other end is grounded. The connecting portion between the inductance L
1
and capacitor C
1
is grounded through the capacitor C
2
and through the conductance G respectively. More, the connecting portion between the capacitor C
1
and signal source S is grounded through the capacitor C
0
. And the resonance frequency of the antenna device
1
is determined mainly by the inductance L
1
and capacitor C
2
.
Further, in
FIGS. 12 and 13
, another conventional surface-mounting type antenna and antenna device including the antenna device are shown. In
FIG. 13
, to the same or equivalent portions as in
FIG. 10
, the same reference numerals are given and their explanation is omitted. The structure of the surface-mounting type antenna
20
in
FIG. 12
is shown in Japanese Unexamined Patent Publication No. 10-13139.
In
FIG. 12
, the surface-mounting type antenna
30
is composed of some electrodes disposed on the surface of a base member
31
in the form of a rectangular solid made up of a dielectric substance such as ceramics, resin, etc. as one insulating material. First of all, a strip-like radiation electrode
32
is disposed along the long side of the side surface
31
c
and over the second major surface
31
b
of the base member
31
. A first end of the radiation electrode
32
is served as an open-ended terminal on the second major surface
31
b
of the base member
31
, and a second end is connected to the grounding terminal
33
disposed on the first major surface
31
a
of the base member
31
. Further, a power-supply electrode
34
is disposed on the second major surface
31
b
of the base member
31
, and the power-supply electrode
34
is connected to a power-supply terminal
35
disposed over the side surface
31
d
to the first major surface
31
a
of the base member
31
. In the same way, on the second major surface
31
b
of the base member
31
, a grounding electrode
36
is disposed in the vicinity of the open-ended terminal
32
a
of the radiation electrode
32
, and the grounding electrode
36
is connected to a grounding terminal
37
disposed over the side surface
31
d
to the first major surface
31
a
of the base member
31
.
Next, in an antenna device
20
shown in
FIG. 13
, the surface-mounting type antenna
30
is mounted in an area
2
a
having no electrode disposed in the vicinity of a corner portion of the circuit board
2
. The grounding terminals
33
and
37
and power-supply terminal
35
of the surface-mounting type antenna
30
are connected to the circuit-board grounding electrode
3
and power-supply line
4
respectively by soldering, etc.
Further, in an equivalent circuit of the antenna device
20
, the capacitor C
2
mainly represents a capacitance produced between the open-ended terminal
32
a
and the grounding electrode
36
, grounding terminal
37
, and circuit-board grounding electrodes of the radiation electrode
32
, and the equivalent circuit is basically the same as in FIG.
11
. Accordingly, here the explanation is omitted.
In order to realize the reduction in size of a communication device equipped with a surface-mounting type antenna, it is necessary to reduce the space occupied by the antenna device on the circuit board, and as a method for the reduction, the reduction in size of the surface-mounting type antenna itself is one choice to be considered.
In the surface-mounting type antennas shown in
FIGS. 9 and 12
, if the base member is simply made small, the length of the radiation electrode is reduced and as a result the inductance L
1
of the radiation electrode is also reduced. Because of this, in order to realize the same inductance L
1
on the equivalent circuit as before, it is necessary to make the radiation electrode thin or have the radiation electrode formed in a meandering way. However, in that case, there is a problem that the resistance component R
1
of the radiation electrode is increased and the antenna gain is reduced. To the contrary, it may be considered that the increase of capaci
Kawahata Kazunari
Nagumo Shoji
Okada Ken
Yuasa Atsuyuki
Le Hoang-anh
Murata Manufacturing Co. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
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