Communications: radio wave antennas – Antennas – With radio cabinet
Reexamination Certificate
2001-12-28
2004-09-07
Chen, Shih-Chao (Department: 2821)
Communications: radio wave antennas
Antennas
With radio cabinet
C343S7000MS, C343S860000, C343S893000
Reexamination Certificate
active
06788259
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-000203, filed Jan. 4, 2001, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an antenna structure and a mobile terminal having the particular antenna structure, particularly, to an antenna structure adapted for use in, for example, a cellular, mobile or PHS (Personal Handy-Phone System) phone or terminal.
2. Description of the Related Art
Mobile phones or terminals are generally provided in general with an antenna, for receiving a high frequency signal from a radio station and for transmission a high frequency signal to the radio station. The antenna employs, in general, an antenna structure constructed to enable extension and retraction of antenna, and is capable of receiving a high frequency signal in the retracted state.
In the antenna structure, a helical first antenna section having a first contact point section is arranged in the mobile terminal body, and a second antenna section having a second contact point section, connected to the first antenna in the longitudinal direction, is housed extensible in the mobile terminal body. When the second antenna section is housed in the mobile terminal body, the helical section alone of the first antenna protrudes from the mobile terminal body, and the first contact point section of the first antenna is connected to the power supply section, with the result that power is supplied to the first antenna section. Also, when the second antenna section is extended from within the mobile terminal body, the second contact point section of the second antenna section is connected to the second contact point section, with the result that power is supplied to the second antenna section. It follows that a high frequency signal can be transmitted and received between the mobile terminal and the radio station whether the antenna is extended or retracted.
As such an antenna, use is made of a monopole antenna having a length of &lgr;/4, 3&lgr;/8 and 5&lgr;/8, where &lgr; represents the wavelength of the high frequency signal that is transmitted or received.
On the other hand, proposed as an antenna satisfying the demands in recent years for the broad band width and for high gain is a so-called “self-resonant” type antenna, of a length &lgr;/2. This type of antenna has a radiation directivity equal to that of a &lgr;/2 dipole antenna, non-directive and a high gain characteristic in a horizontal plane. Thus, the self-resonant type can be applied to a so-called “viewer type” mobile terminal on which a large liquid crystal screen is mounted so as to make it possible for the user to transmit and receive data, such as character data, still and moving image data, while observing the liquid crystal screen.
Also, in the self-resonant type antenna, it is impossible to directly connect the power supply point of the antenna to a radio frequency circuit section so as to supply a power to the antenna, because the self-resonant type antenna has high impedance at the bottom end thereof. Thus, the antenna is preferably coupled to the radio frequency circuit section via a matching circuit of weak magnetic field coupling type to reduce the Q factor and to increase the bandwidth. The antenna is more preferably coupled to the radio frequency circuit via a matching circuit of &lgr;/2 capacitive-coupling type, which has a line of &lgr;/4. This self-resonant type antenna can realize a characteristics having two resonant points and a more broader bandwidth, which is referred to herein after as a &lgr;/2 capacitive-coupling antenna.
As a retractable antenna, there is known a bottom helical structure in which a helical antenna as the first antenna is fixed in the housing of the mobile terminal, when the extensible antenna as the second antenna is pulled up from the housing.
A &lgr;/2 capacitive-coupling antenna having the bottom helical structure is disclosed in U.S. Pat. No. 5,717,409, issued Feb. 10, 1998, Garner et al, which has a configuration as shown in FIG.
1
. In the mobile terminal shown in
FIG. 1
, a radio transmission section
3
is arranged within a terminal body
2
. An antenna cap
5
C is erected on the terminal body
2
, and an antenna element
5
D constituting an antenna in the retracted state is spirally arranged in the axial direction of the antenna within the antenna cap
5
C. Also, a cylindrical frame
5
F having a spiral matching circuit element
5
E formed on the circumferential wall is coaxially arranged within the antenna element
5
D.
An extensible antenna
5
G (movable in the direction denoted by the arrows A and B) when extended, is capable of being housed in the cylindrical frame
5
F with a sleeve
5
H interposed therebetween. If the antenna
5
G is extended from the housing or terminal body
2
, the antenna
5
G is capacitively coupled with the matching circuit element
5
E via a capacitive coupling section
5
I of the sleeve
5
H. Also, if the antenna
5
G is housed in the terminal body
2
, the antenna element
5
D, not the antenna
5
G is capacitively coupled with the matching circuit element
5
E.
In the &lgr;/2 capacitive coupling antenna, however, it is necessary to coaxially mount the antenna element
5
D and the matching circuit element
5
E, leading to the problem that the construction of the antenna is rendered highly complex.
As described above, the construction of the conventional antenna is highly complex.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide an antenna structure simple in structure and capable of increasing the bandwidth and increasing the gain, and to provide a mobile terminal equipped with the particular antenna structure.
According to a first aspect of the present invention, there is provided an antenna structure arranged in a mobile terminal having a body including a holding section configured to hold an antenna structure and a mobile terminal circuit section housed in the body, comprising:
a flexible substrate mounted within the holding section;
a meander-shaped antenna pattern formed on the flexible substrate;
a matching circuit element configured to substantially match the impedances of the antenna pattern and a mobile terminal section; and
a capacitive coupling element configured to achieve a capacitive coupling between the antenna pattern and the matching circuit.
According to a second aspect of the present invention, there is provided an antenna structure arranged in a mobile terminal having a body including a holding section configured to hold an antenna structure and a mobile terminal circuit section housed in the body, comprising:
a first antenna element extending substantially linearly;
an antenna support mechanism configured to support the first antenna element, arranged within an antenna holding section, and to permit the first antenna element to be withdrawn from a body of a mobile terminal and to be brought back into the body so as to be housed in the body;
a flexible substrate mounted within the holding section and arranged around the first antenna element withdrawn from the body;
a second antenna pattern formed bent on the flexible substrate;
a matching circuit configured to permit the impedance of the first antenna element to be matched with the impedance of the radio transmission section of the second antenna pattern; and
a capacitive coupling element configured to permit the first antenna element and the second antenna pattern to be coupled with the matching circuit by a capacitive coupling.
According to a third aspect of the present invention, there is provided a mobile terminal, comprising:
a first antenna element extending substantially linearly and having an antenna axis;
a body including a housing section for housing the first antenna element;
an antenna support mechanism configured to support the first antenna element, housed in the housing section, and to permit the first antenna element to be withd
Amano Takashi
Chiba Norimichi
Iwasaki Hisao
Suzuki Hiromichi
Chen Shih-Chao
Kabushiki Kaisha Toshiba
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