Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
1999-08-09
2001-05-08
Le, Hoanganh (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S846000
Reexamination Certificate
active
06229485
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an antenna device, and more particularly, is suitably applied to a portable telephone which is reduced in size.
2. Description of the Related Art
In small portable radio apparatus such as portable telephones, terminal units for personal handyphone system (PHS), or the like, a reduction in size, thickness and weight has been promoted with recent rapid development of such apparatuses. Correspondingly, antennas associated therewith are also required to have a reduced size, thickness and weight as well as higher performance.
An example of an antenna equipped in such a small portable radio apparatus is a micro-strip antenna (hereinafter referred to as the “MS antenna”). Further, commonly known as antennas, which are further reduced in size than the MS antennas, are a single-side short-circuited MS antenna having a short-circuit surface for short-circuiting a zero-potential surface at the center of a radiation conductor to a ground conductor, a laminar inverted-F antenna having a further reduced width of its short-circuit surface, and so on.
For example, as illustrated in
FIGS. 1A and 1B
, a conventional MS antenna
1
comprises a ground conductor
2
disposed on one side of a dielectric substrate
3
having a height h, and a rectangular radiation conductor
4
(length a×width b) formed on the other side of the substrate
3
using an etching technique or the like.
This MS antenna
1
is provided with a power supply point
5
at a predetermined position on the radiation conductor
4
so that the input impedance thereof is equal to the characteristic impedance of a power supply system. The MS antenna
1
operates as an antenna with power supplied thereto through the power supply point
5
.
As illustrated in
FIGS. 2A and 2B
, a single-side short-circuited MS antenna
6
comprises a short-circuit conductor
10
having a width Ws
1
identical to the width b of a radiation conductor
8
and a height h, disposed between the radiation conductor
8
and a ground conductor
7
, so as to short-circuit a zero-potential surface of the radiation conductor
8
to the ground conductor
7
. The zero-potential surface, at which an electric field is at “0,” is at a position corresponding to one half a/2 of the length a of the radiation conductor
4
in the normal MS antenna
1
.
With this structure, the single-side short-circuited MS antenna
6
only requires the radiation conductor
8
having a length dimension approximately one half of the length dimension of the radiation conductor
4
of the MS antenna
1
and still operates as an antenna at the same resonant frequency as the MS antenna
1
.
Further, as illustrated in
FIGS. 3A and 3B
, a laminar inverted-F antenna
10
is composed of a rectangular radiation conductor
12
(length c×width d) and a ground conductor
11
which are short-circuited by a laminar inverted-F short-circuit conductor
14
having a width Ws
2
smaller than the width Ws
1
of the short-circuit conductor
10
of the single-side short-circuited MS antenna
6
.
The laminar inverted-F antenna
10
can reduce the resonant frequency fr by virtue of the laminar inverted-F short-circuit conductor
14
having the width Ws
2
chosen to be smaller than the width Ws
1
of the short-circuit conductor
8
of the single-side short-circuited MS antenna
6
, and can further reduce the resonant frequency fr by virtue of the power supply point
5
defined at a position offset from the center line of the radiation conductor
12
by an offset amount Wx
2
, as compared with the power supply point
5
defined at the center of the radiation conductor
12
.
As mentioned above, since the laminar inverted-F antenna
10
is designed to reduce the resonant frequency fr more than the MS antenna
1
, it can be configured using the radiation conductor
12
(length c×width d) smaller than the radiation conductor
4
(length a×width b), when it is operated at the same frequency as the MS antenna
1
.
The single-side short-circuited MS antenna
6
and the laminar inverted-F antenna
10
, configured as described above, are required to be further reduced in size in response to the demand for increasingly smaller portable telephones in recent years.
SUMMARY OF THE INVENTION
In view of the foregoing, an object of this invention is to provide an antenna device which is capable of realizing a further reduction in size and weight.
The foregoing object and other objects of the invention have been achieved by the provision of an antenna device which comprises a flat ground conductor; a first flat radiation conductor disposed against the flat ground conductor interposing a first dielectric layer; a first short-circuit conductor connecting an end of the first flat radiation conductor and the flat ground conductor; a second flat radiation conductor disposed partly against an opposite side of the first flat radiation conductor to its other side facing the ground conductor interposing a second dielectric layer; a second short-circuit conductor connecting an end of the second flat radiation conductor and the flat ground conductor; and a supply point disposed on the first flat radiation conductor.
With the structure as above, the first flat radiation conductor and the second flat radiation conductor are disposed partly against each other, which enables more size reduction than that of conventional antennas in operating at the same resonant frequency with a conventional antenna.
The nature, principle and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings in which like parts are designated by like reference numerals or characters.
REFERENCES:
patent: 5041838 (1991-08-01), Limatainen et al.
patent: 5307075 (1994-04-01), Huynh
patent: 5801660 (1998-09-01), Ohtsuka et al.
patent: 6002367 (1999-12-01), Engblom et al.
Ito Hiroki
Saito Yuichiro
Sawamura Masatoshi
Alemu Ephrem
Le Hoang-anh
Maioli Jay H.
Sony Corporation
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