Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
2003-06-18
2004-10-19
Wimer, Michael C. (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S702000, C343S895000
Reexamination Certificate
active
06806832
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a compact surface-mount type antenna and an antenna apparatus for use in mobile communication equipment such as a cellular phone.
2. Description of the Related Art
In keeping with rapid advancement of down-sized mobile communication equipment such as a cellular phone, miniaturization has been underway in an antenna which constitutes such equipment. Thus, for example, a surface-mount type antenna has hitherto been developed. Now, a conventional surface-mount type antenna and an antenna apparatus incorporating it will be described with reference to a perspective view shown in FIG.
8
.
In
FIG. 8
, reference numeral
50
denotes a surface-mount type antenna. This surface-mount type antenna
50
is mounted on a mounting substrate
56
, thus constituting an antenna apparatus
61
. In the surface-mount type antenna
50
shown in
FIG. 8
, reference numeral
51
denotes a substantially prismatic base body; reference numeral
52
denotes a feeding terminal; reference numeral
53
denotes a ground terminal; and reference numeral
54
denotes a radiating electrode. Moreover, in the mounting substrate
56
, reference numeral
57
denotes a substrate; reference numeral
58
denotes a feeding electrode; reference numeral
59
denotes a ground electrode; and reference numeral
60
denotes a ground conductor layer.
In the conventional surface-mount type antenna
50
, the feeding terminal
52
and the ground terminal
53
are formed on a side surface of the base body
51
. The radiating electrode
54
, which is routed as a slim conductor pattern, is configured as follows. At first it extends upwardly from the ground terminal
53
on the side surface, and is then substantially U-shaped, as viewed plane-wise, on a top surface of the base body
51
so as to take substantially the form of a loop, and eventually returns to the side surface once again to extend downwardly toward the feeding terminal
52
. Moreover, the radiating electrode
54
has a gap
55
formed in a certain position thereof close to the feeding terminal
52
. Thereby, the capacitance of the radiating electrode
54
can be so adjusted that impedance matching is achieved between the radiating electrode
54
and the feeding electrode
58
(feeding line) of the mounting substrate
56
.
On the other hand, in the mounting substrate
56
, on a surface of the substrate
57
are formed the feeding electrode
58
, the ground electrode
59
, and the ground conductor layer
60
. The ground conductor layer
60
is arranged on one side of the ground electrode
59
so as to be connected thereto.
Then, the surface-mount type antenna
50
is mounted, with the feeding terminal
52
connected to the feeding electrode
58
and the ground terminal
53
connected to the ground electrode
59
, on the surface of the mounting substrate
56
, thus constituting the antenna apparatus
61
.
In the conventional surface-mount type antenna
50
, however, since the radiating electrode
54
is made short, there is a tendency of an operating frequency to increase. To decrease the operating frequency, the base body
51
needs to have a higher dielectric constant, or the radiating electrode
54
needs to be slimmed down.
However, an increase in the dielectric constant of the base body
51
gives rise to a problem of the antenna characteristics being abruptly changed to narrow-band characteristics. On the other hand, slimming of the radiating electrode
54
gives rise to a problem of great radiation loss.
Moreover, by adjusting a size of the gap
55
which is formed in the radiating electrode
54
to achieve impedance matching between the radiating electrode
54
and the feeding electrode
58
, the impedance of the radiating electrode
54
can be changed. In this case, however, a resonant frequency of the antenna varies with the change of the impedance. This makes it difficult to attain the desired antenna characteristics as designed.
SUMMARY OF THE INVENTION
The invention has been devised in view of the above-described problems with the conventional art, and accordingly its object is to provide a surface-mount type antenna and an antenna apparatus capable of attaining satisfactory antenna characteristics with stability, of enhancing radiation efficiency, and of achieving miniaturization.
The invention provides a surface-mount type antenna comprising:
a base body made of a dielectric or magnetic material having a substantially rectangular solid shape;
a feeding terminal formed at one end of one side surface of the base body;
a ground terminal formed at another end of the one side surface of the base body;
a radiating electrode which has its one end connected to the ground terminal, the radiating electrode being disposed helically across the surfaces of the base body in such a way that it extends from the one side surface, across one principal surface, another side surface which is opposite to the one side surface, and another principal surface which is opposite to the one principal surface, and then returns to the one side surface and further extends, through the one principal surface, toward the one end of the one side surface; and
a wide-area portion,
wherein another end of the radiating electrode extends from the one principal surface, through the other side surface, toward the other principal surface, so as to form the wide-area portion facing the feeding terminal.
According to the invention, the radiating electrode is disposed helically across the surfaces of the base body in such a way that it extends from the one side surface, across the one principal surface, the other side surface, and the other principal surface, and then returns to the one side surface and further extends, through the one principal surface, toward the one end of the one side surface, and further the other feeding-terminal-side end of the radiating electrode extends across the surfaces of the base body, i.e., extends from the one principal surface, through the other side surface, toward the other principal surface, so as to form the wide-area portion facing the feeding terminal. With this configuration, the radiating electrode can be made longer, and also the wide-area portion of the radiating electrode can be electro magnetically coupled to the feeding terminal through an electric capacitance generated therebetween. Moreover, at the time of mounting on the mounting substrate, since a large capacitance can be created between the wide-area portion of the radiating electrode and the ground conductor layer of the mounting substrate, the resonant frequency of the radiating electrode can be decreased. This makes it possible to achieve miniaturization of the antenna without increasing the dielectric constant of the base body and without excessively slenderizing the radiating electrode.
Further, according to the invention, the impedance matching between the radiating electrode and the feeding electrode (feeding line) of the mounting substrate on which the radiating electrode is mounted can be achieved by adjusting the capacitance between the radiating electrode and the feeding terminal. The capacitance adjustment can be made by adjusting the configuration and/or area of the wide-area portion of the radiating electrode. Meanwhile, a dominant factor in the magnitude of the resonant frequency of the antenna is the capacitance between the radiating electrode and the ground conductor layer of the mounting substrate. Hence, variation in the resonant frequency resulting from the impedance adjustment by means of the wide-area portion can be minimized. As a result, it is possible to obtain a compact surface-mount type antenna that provides higher radiation efficiency and stable antenna characteristics.
In the invention, it is preferable that a width of the wide-area portion is adjusted to be three to ten times that of a conductor portion of the radiating electrode having a helical conformation.
According to the invention, the capacitance between the wide-area portion and the feeding terminal or the ground conductor l
Ikuta Takanori
Murakawa Shunichi
Sato Akinori
Watada Kazuo
Hogan & Hartson LLP
Kyocera Corporation
Wimer Michael C.
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