Communications: radio wave antennas – Antennas – With radio cabinet
Reexamination Certificate
2002-07-05
2004-01-27
Le, Hoanganh (Department: 2821)
Communications: radio wave antennas
Antennas
With radio cabinet
C343S7000MS
Reexamination Certificate
active
06683575
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2001-205239, filed Jul. 5, 2001; and No. 2001-371772, filed Dec. 5, 2001 the entire contents of both of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an antenna apparatus used as antenna mounted on a surface of a vehicle or used as a built-in antenna for a portable telephone or the like.
2. Description of the Related Art
The antenna of a portable telephone suffers a changeable frequency characteristic depending on the proximity of the user's body or the like. To mitigate the change, the antenna of a portable telephone must be broadband.
An antenna shown in
FIG. 1
is a conventional antenna. The antenna is a built-in antenna which is set on one surface, i.e., ground plane
100
of a square internal housing
101
made of a ground conductor (ground plane) inside an external housing made of an insulator such as a plastic in a wireless communication device. This antenna is constituted by a planar inverted-F antenna made up of a first and second planar antenna elements
104
and
105
, and a third planar antenna element
106
interposed between the ground plane
100
and the second planar antenna element
105
. The second planar antenna element
105
is connected to a feed line
103
at a node
111
, whereas the third planar antenna element
106
is connected to the feed line
103
at a node
112
.
A radio circuit
113
is connected to the feed point
102
and transmits and receives a radio wave via the first, second, and third planar antenna elements
104
,
105
, and
106
.
The antenna shown in
FIG. 1
serves as a broadband antenna by adding the third planar antenna element
106
to the planar inverted-F antenna. This antenna, which occupies a wide area in mounting and is difficult to design, was reported by the present inventor (No. 675) in the 1986 IEICE National General Conference in Japan.
In recent years, terminals such as for wireless communication devices are being downsized for progressing its portability. Demands have arisen for a small structure in which an antenna as shown in
FIG. 1
is mounted on a circuit board and parts are mounted immediately below a planar antenna element. However, the antenna shown in
FIG. 1
has two, third and second, planar antenna elements, which poses limitations on downsizing of parts mounted on the circuit board
100
.
The antenna shown in
FIG. 1
requires a long time for design. This antenna comprises the first, second, and third planar antenna elements
104
,
105
, and
106
. The widths and heights of the first, second, and third planar antenna elements
104
,
105
, and
106
, and their area which is the product of the widths and heights are included in parameters which determine the frequency characteristic of the antenna. Correlation parameters between the first, second, and third planar antenna elements
104
,
105
, and
106
cannot be ignored. A model to be input to an electromagnetic simulation is difficult to formulate. For an experimental approach, many parameters must be taken into consideration. It takes a long time to optimize the dimension values of the structure. Since the design guideline values of the antenna have not been determined, desired broadband characteristics are very difficult to obtain. As described above, in a conventional broadband planar inverted-F antenna as shown in
FIG. 1
, an unnecessary mounting area and design difficulty are left unsolved.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide an antenna apparatus which is easy to design and ensures a wide part mounting area.
According to an aspect of the present invention, there is provided an antenna apparatus comprising a feed point, a first linear antenna element, a second linear antenna element, a third linear antenna element, a fourth linear antenna element, and a connection element, wherein one end of the first linear antenna element is connected to the feed point, one end of the second linear antenna element is connected to the other end of the first linear antenna element, one end of the third linear antenna element is connected to the other end of the first linear antenna element, one end of the fourth linear antenna element is connected to the other end of the second linear antenna element, the connection element connects the other end of the second linear antenna element and a ground terminal, the third and fourth linear antenna elements are arranged parallel to each other, a sum of lengths of the first, second, and fourth linear antenna elements is ¼ a wavelength corresponding to a series-resonance frequency of the first, second, and fourth linear antenna elements, a sum of lengths of the second, third, and fourth linear antenna elements is ½ a wavelength corresponding to a parallel-resonance frequency of the second, third, and fourth linear antenna elements, a sum of lengths of the first and third linear antenna elements is ¼ a wavelength corresponding to a parallel-resonance frequency of the first and third linear antenna elements, and the parallel-resonance frequency is higher than a frequency of the series-resonance frequency of the first, second, and fourth linear antenna elements and lower than the series-resonance frequency of the first and third linear antenna elements.
According to another aspect of the present invention, there is provided an antenna apparatus comprising a feed point, a first linear antenna element, a second linear antenna element, a third linear antenna element, and a connection element, wherein one end of the first linear antenna element is connected to the feed point, one end of the second linear antenna element is connected to the other end of the first linear antenna element, one end of the third linear antenna element is connected to the other end of the first linear antenna element, the connection element which connects the other end of the first linear antenna element and a ground terminal, a sum of lengths of the first and third linear antenna elements is ¼ a wavelength corresponding to the series-resonance frequency of the first and third linear antenna elements, a sum of lengths of the second and third linear antenna elements is ½ a wavelength corresponding to the parallel-resonance frequency of the second and third linear antenna elements, a sum of lengths of the first and second linear antenna elements is ¼ a wavelength corresponding to a series-resonance frequency of the first and second linear antenna elements, and the parallel-resonance frequency is higher than a frequency of the series-resonance frequency of the first and third linear antenna elements and lower than the series-resonance frequency of the first and second linear antenna elements.
According to another aspect of the present invention, there is provided an antenna apparatus comprising a feed point, a first linear antenna element, a second linear antenna element, a third linear antenna element, and a connection element, wherein one end of the first linear antenna element is connected to the feed point, one end of the second linear antenna element is connected to the other end of the first linear antenna element, one end of the third linear antenna element is connected to the other end of the second linear antenna element, the connection element which connects the other end of the second linear antenna element and a ground terminal, a sum of lengths of the first, second, and third linear antenna elements is ¼ a wavelength corresponding to the series-resonance frequency of the first, second, and third linear antenna elements, a sum of lengths of the second and third linear antenna elements is ½ a wavelength corresponding to the parallel-resonance frequency of the second and third linear antenna elements, a sum of lengths of the first linear antenna elements is ¼ a wavelength corresponding to the series-r
Ito Takayoshi
Murakami Yasushi
Sekine Syuichi
Shoki Hiroki
Kabushiki Kaisha Toshiba
Le Hoang-anh
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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