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Mobile Phone Patent Abstract
A mobile phone antenna has: a first conductive radiation element
that is formed in a sheet metal conductor and resonates at a predetermined
resonance frequency; a second conductive radiation element that
is formed in the sheet metal conductor and resonates at the predetermined
resonance frequency; and a ground that is connected through a conductive
ground connector with the second conductive radiation element. The
ground is placed such that the ground is not opposed to the first
and second conductive radiation elements.
Mobile Phone Patent Claims
What is claimed is:
1. A mobile phone antenna, comprising: a first conductive radiation
element that is formed in a sheet metal conductor and resonates
at a predetermined resonance frequency; a second conductive radiation
element that is formed in the sheet metal conductor and resonates
at the predetermined resonance frequency; and a ground that is connected
through a conductive ground connector with said second conductive
radiation element; wherein said ground is placed such that said
ground is not opposed to said first and second conductive radiation
elements, and wherein said second conductive radiation element functions
as a ground, wherein said ground includes: a first ground that is
connected through said conductive ground connector with said second
conductive radiation element; and a second ground that is connected
through a conductive inter-ground connector with said first ground,
said second ground being capable of rotating in the range of a predetermined
angle from a position that said second ground faces in parallel
to said first ground, wherein said conductive inter-ground connector
is positioned under said second conductive radiation element when
said second ground rotates by said predetermined angle, wherein
said conductive inter-around connector has a first bend portion
at a first end thereof, a straight middle portion, and a second
bend portion at a second end thereof, and wherein the first bend
portion is directly connected to said first around and said second
bend portion is directly connected to said second ground.
2. The mobile phone antenna according to claim 1, further comprising
a third conductive radiation element, wherein said first conductive
radiation element resonates at a first resonance frequency and said
third conductive radiation element resonates at a second resonance
frequency.
3. The mobile phone antenna according to claim 2, wherein said
third conductive radiation element is disposed at right angle to
a surface in which said first and second conductive radiation elements
are formed.
4. The mobile phone antenna according to claim 3, wherein the third
conductive radiation element has an L-shape that is inverted with
respect to said first conductive radiation element that also has
an L-shape.
5. The mobile phone antenna according to claim 2, wherein said
second conductive radiation element includes: a first coupling adjuster
that extends parallel to said first conductive radiation element
while having a first clearance with said first conductive radiation
element; and a second coupling adjuster that extends parallel to
said third radiation element while having a second clearance with
said third conductive radiation element; and said first and second
coupling adjusters have a length, a width and said first and second
clearances to be adjusted such that said mobile phone antenna has
a predetermined resonance frequency and bandwidth.
6. The mobile phone antenna according to claim 5, wherein said
first and second clearances are set 2 mm or less.
7. The mobile phone antenna according to claim 1, wherein said
second conductive radiation element includes a coupling adjuster
that extends parallel to said first conductive radiation element
while having a predetermined clearance with said first conductive
radiation element; said coupling adjuster has a length, a width
and said clearance to be adjusted such that said mobile phone antenna
has a predetermined resonance frequency and bandwidth.
8. The mobile phone antenna according to claim 7, wherein said
clearance is set 2 mm or less.
9. The mobile phone antenna according to claim 1, wherein the first
ground is a board ground and the second ground is an LCD ground.
10. A mobile phone antenna for folding type mobile phone with a
pair of housings foldable, comprising: a first ground that is installed
in one of said pair of housings; a second ground that is installed
in the other of said pair of housings, said second ground being
connected through a conductive inter-ground connector with said
first ground; first and second conductive radiation elements that
are disposed at a position where said first and second conductive
radiation elements are not opposed to said first and second ground,
said first and second conductive radiation element resonating at
a predetermined resonance frequency; and a conductive ground connector
that electrically connects said first ground with said second conductive
radiation element, wherein said second conductive radiation element
functions as a ground, wherein said second ground is capable of
rotating in the range of a predetermined angle from a position that
said second ground in parallel to said first ground, wherein said
conductive inter-ground connector is positioned under said second
conductive radiation element when said second ground rotates by
said predetermined angle, wherein said conductive inter-ground connector
has a first bend portion at a first end thereof, a straight middle
portion, and a second bend portion at a second end thereof, and
wherein said first bend portion is directly connected to said first
ground and said second bend portion is directly connected to said
second ground.
11. The mobile phone antenna according to claim 10, wherein said
conductive ground connector has a first bend portion at a first
end thereof, a straight middle portion, and a second bend portion
at a second end thereof, and wherein the first bend portion is directly
connected to said first ground and said second bend portion is directly
connected to said second ground.
Mobile Phone Patent Description
The present application is based on Japanese patent application
No.2002-262928, the entire contents of which are incorporated herein
by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a mobile phone antenna and, particularly,
to a mobile phone antenna that the bandwidth can be broadened without
raising the position of an antenna element and that can prevent
displacement in resonance frequency in a folding type mobile phone
where the position of a board ground is shifted when folded.
2. Description of the Related Art
Mobile phones and PHS (personal handyphone system) phones are provided
with a telescoping whip antenna and a built-in planar antenna so
as to facilitate the receiving and transmitting with the base station.
The planar antenna used is generally inverted F antenna that has
a miniaturized size, a simplified structure and broad bandwidth
characteristics.
FIG. 1 is a perspective view showing a conventional inverted F
antenna for mobile phone. The inverted F antenna 100 for mobile
phone is provided with a ground plane 101 as a printed circuit board
which is installed in the housing of mobile phone, and the ground
plane 101 is composed of interconnection pattern and metal conductors.
Above the ground plane 101, there is provided a planar antenna radiation
element 102 of metal plate. Further, a ground connector 103 and
a feed point 104 are provided to connect the ground plane 101 with
the antenna radiation element 102.
However, in the convention inverted F antenna, it is necessary
to raise, by a certain height, the antenna element 102 from the
ground plane 101 since the bandwidth narrows according as the antenna
element 102 comes closer to the ground plane 101. Furthermore, since
the inverted F antenna is apt to be affected by the ground of printed
circuit board (board ground), there occurs a displacement in resonance
frequency when the position of board ground varies as the upper
and lower housings are opened or closed that are equipped with a
folding type mobile phone.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a mobile phone antenna
that the bandwidth can be broadened without raising the position
of antenna element and that can prevent displacement in resonance
frequency in a folding type mobile phone where the position of board
ground is sifted when folded.
According to one aspect of the invention, a mobile phone antenna,
comprises:
a first conductive radiation element that is formed in a sheet
metal conductor and resonates at a predetermined resonance frequency;
a second conductive radiation element that is formed in the sheet
metal conductor and resonates at the predetermined resonance frequency;
a ground that is connected through a conductive ground connector
with the second conductive radiation element;
wherein the ground is placed such that the ground is not opposed
to the first and second conductive radiation elements.
According to another aspect of the invention, a mobile phone antenna
for folding type mobile phone with a pair of housings foldable,
comprises:
a first ground that is installed in one of the pair of housings;
a second ground that is installed in the other of the pair of housings,
the second ground being connected through a conductive inter-ground
connector with the first ground;
first and second conductive radiation elements that are disposed
at a position where the first and second conductive radiation elements
are not opposed to the first and second ground, the first and second
conductive radiation element resonating at a predetermined resonance
frequency; and
a conductive ground connector that electrically connects the first
ground with the second conductive radiation element.
In the mobile phone antenna according to the invention, the second
conductive radiation element functions as a ground and, therefore,
it is not necessary for a ground such as printed circuit board and
electronic parts to be placed under or near the conductive radiation
element (antenna element). Namely, it is not necessary to raise
the conductive radiation element from the ground. Hence, the antenna
can offer a broadened bandwidth and prevent displacement in resonance
frequency.
BRIEF DESCRIPTION OF THE DRAWINGS
The preferred embodiments according to the invention will be explained
below referring to the drawings, wherein:
FIG. 1 is a perspective view showing the conventional inverted
F antenna for mobile phone;
FIG. 2A is a perspective view showing a mobile phone antenna in
a first preferred embodiment according to the invention;
FIG. 2B is a side view illustrating the opened state of a LCD ground
23 in FIG. 2A;
FIG. 2C is a plain view showing the main part of the mobile phone
antenna in FIG. 2A;
FIG. 3 is a side view showing the schematic composition of a folding
type mobile phone installing the mobile phone antenna of the first
embodiment;
FIG. 4A is a perspective view showing a mobile phone antenna in
a second preferred embodiment according to the invention;
FIG. 4B is a plain view showing the main part of the mobile phone
antenna in FIG. 4A;
FIG. 5 is a perspective view showing a mobile phone antenna in
a third preferred embodiment according to the invention;
FIG. 6 is a graph showing return loss comparison between the mobile
phone antenna of the third embodiment and a comparative example
(conventional inverted F dual antenna in FIG. 1);
FIG. 7 is a perspective view showing a radiation element in a fourth
preferred embodiment according to the invention; and
FIG. 8 is a perspective view showing a mobile phone antenna in
a fifth preferred embodiment according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 2A is a perspective view showing a mobile phone antenna in
the first preferred embodiment according to the invention. FIG.
2B is a side view illustrating the opened state of a LCD ground
23 in FIG. 2A. FIG. 2C is a plain view showing the main part of
the mobile phone antenna in FIG. 2A.
As shown in FIG. 2A, the mobile phone antenna includes a radiation
element 10 that resonates at a predetermined frequency, a board
ground 32, and a LCD ground 23. The radiation element 10 is connected
through a ground connector 42 with the board ground 32. The board
ground 32 is connected through an inter-board ground connector 41
with LCD ground 23 such that the LCD ground 23 can be opened (FIG.
2B). The radiation element 10 is provided with a strip-shaped feed
member 43 that is disposed adjacent to the ground connector 42 and
suspends vertically from radiation element 10. A feed point 44 lies
between the lower end of the feed member 43 and the board ground
32.
The radiation element 10 is, as shown in FIG. 2C, composed of:
a first radiation element 11 which is, as a whole, U-shaped and
strip part at one end of which forms main part; a coupling adjuster
12 that is placed adjacent to the first radiation element 11 and
extends from the opposite direction to the first radiation element
11; a strip-shaped second radiation element 13 that is connected
with the first radiation element 11 and the coupling adjuster 12,
wherein there is provided a cutting region 10a between the first
radiation element 11 and the coupling adjuster 12 to form a planar
antenna.
The inter-board ground connector 41 is of a material that can endure
a number of folding cycles since it is subject to a stress in opening
and closing of the LCD ground 23 when it is applied to a folding
type mobile phone. The inter-board ground connector 41 connects
the board ground 32 and the LCD ground 23 on the second radiation
element 13 side. This reduces an influence caused by ground in opening
and closing.
The ground connector 42 is, as shown in FIG. 2A, L-shaped and connected
with one end of the second radiation element 13, and its one end
(lower end) is connected with a corner of the board ground 32.
The radiation element 10 has, by itself, a function needed to operate
as antenna by the first and second radiation elements 11, 13 and
the coupling adjuster 12 as shown in FIG. 2A. Therefore, it is not
necessary to provide the board ground 32 and the LCD ground 23 under
the antenna. Thus, the radiation element 10 can be in such a state
that it floats, in relation to high frequency, from the board ground
32, LCD ground 23 and the other ground (external ground etc.). In
other words, it can be in a state of being not connected in relation
to high frequency. "state of being not connected in relation
to high frequency" means that the radiation element 10 does
not have a conduction portion to be always at the same potential
as ground. Namely, when the mobile phone antenna 1 is installed
in a mobile phone, the radiation element 10 is electrically connected
with a high-frequency circuit (e.g., receive and transmit circuit)
of the mobile phone only through the interconnection through the
feed member 43 with feed point 44 and through the ground connector
42 with the board ground 32. The radiation element 10 does not contact
the other ground and is not connected directly with that, so that
it lies independently.
In the first embodiment, the radiation element 10 is provided with
the coupling adjuster 12 and, therefore, the resonance frequency
(.apprxeq..lambda./4) and bandwidth of antenna 1 can be adjusted
to a desired value by changing a clearance (t) between the first
radiation element 11 and the coupling adjuster 12 and a length (L)
of the coupling adjuster 12. Meanwhile, clearance (t) is preferably
2 mm or less. The radiation element 10, ground connector 42 and
feed member 43 may be integrally manufactured by punching or etching.
Thereby, the number of parts can be reduced.
FIG. 3 is a side view showing the schematic composition of a folding
type mobile phone installing the mobile phone antenna of this embodiment.
The folding type mobile phone includes a speaker (not shown), an
upper housing 20 on which a liquid crystal display (LCD) is mounted,
and a lower housing 30 that has an operation part with numeral keys
and cursor keys, a microphone, earphone jack, charging terminal
etc. The upper housing 20 is engaged rotatably around a hinge 40
with the lower housing 30. The mobile phone antenna 1 is installed
in the upper housing 20 and the lower housing 30.
The upper housing 20 houses the LCD 21, a printed circuit board
22 mounted on the back side of LCD 21, and the LCD ground 23 provided
on the back side of the printed circuit board 22.
The lower housing 30 houses a printed circuit board 31 with the
board ground 32. The upper housing 20 can have an angle from zero
in shut state to about 150 in opened state with reference to the
lower housing 30 around the hinge 40. Although the radiation element
10 is electrically connected with the lower housing 30, they are
not integrated mechanically and therefore they are movable to each
other.
FIG. 4A is a perspective view showing a mobile phone antenna in
the second preferred embodiment according to the invention. FIG.
4B is a plain view showing the main part of the mobile phone antenna
in FIG. 4A.
The mobile phone antenna 1 of the second embodiment is applied
to a folding type mobile phone as that in the first embodiment.
As shown in FIG. 4B, in the second embodiment, a third radiation
element 14 is added as comparing to the mobile phone antenna 1 of
the first embodiment. The other components are the same as those
of the first embodiment.
The L-shaped third radiation element 14 is disposed such that it
protrudes inside the first radiation element 11 near the feed point.
Thus, the third radiation element 14 is, as shown in FIG. 4A, on
the same plane as the first radiation element 11, coupling adjuster
12 and second radiation element 13.
In the mobile phone antenna 1 of the second embodiment, a first
resonance frequency is determined by the first and second radiation
elements 11, 13 and a second resonance frequency is determined by
the second and third radiation elements 13, 14. Therefore, it is
made to be multiband as compared to the mobile phone antenna of
the first embodiment. Also, it can offer a broadened band like that
of the first embodiment, and it can prevent displacement in resonance
frequency due to opening and closing of the housing.
FIG. 5 is a perspective view showing a mobile phone antenna in
the third preferred embodiment according to the invention.
The mobile phone antenna 1 of the third embodiment is applied to
a folding type mobile phone as that in the first embodiment. As
shown in FIG. 5, in the third embodiment, the third radiation element
14 of the second embodiment is folded at right angles to the other
parts and the feed member 43 thereof is omitted. The other components
are the same as those of the second embodiment.
In the mobile phone antenna 1 of the second embodiment, electromagnetic
waves can be radiated from the side. Also, it can be multiband and
miniaturized while offering a broadened band, and it can prevent
displacement in resonance frequency due to opening and closing of
the housing.
FIG. 6 is a graph showing return loss comparison between the mobile
phone antenna of the third embodiment and a comparative example
(conventional inverted F dual antenna in FIG. 1). In FIG. 6, A represents
characteristics of the comparative example, B represents characteristics
of the mobile phone antenna of the third embodiment in the opened
state of folding type mobile phone, and C represents characteristics
of the mobile phone antenna of the third embodiment in the closed
state of folding type mobile phone.
Table 1 shows specific bandwidth comparison in VSWR=3. In Table
1, GSM stands for global system for mobile communication system
and 800 MHz band (870 to 960 MHz) is used in GSM band. DCS stands
for digital cellular system and 1.7 GHz band (1710 to 1880 MHz)
is used in DCS band.
TABLE 1 Specific bandwidth Specific bandwidth Characteristic (GSM
band) in VSWR = 3 (DCS band) in VSWR = 3 A 7.3% 10.2% B 10.6% 33.2%
C 10.2% 20.7%
As shown in FIG. 6 and Table 1, the mobile antenna (B, C) of the
third embodiment is enhanced by about 3% in specific bandwidth at
GSM band and by about 10 to 23% in specific bandwidth at DCS band
as compared to that of the conventional inverted F dual antenna
(A). Also, there occurs little displacement in resonance frequency
due to opening and closing of the hosing of mobile phone.
As described above, the mobile phone antenna of the third embodiment
can offer a broadened band both at GSM and DCS band and prevent
displacement in resonance frequency due to opening and closing of
the housing even when it is installed in a mobile phone.
FIG. 7 is a perspective view showing a radiation element in the
fourth preferred embodiment according to the invention. In the fourth
embodiment, it is intended to prevent displacement in resonance
frequency both at GSM band and DCS band. Thus, there is provided
a strip-shaped coupling adjuster 15, on the side face of the radiation
element 10, between the third radiation element 14 and coupling
adjuster 12 in the third embodiment in FIG. 5 and parallel to them.
The other components are the same as those of third embodiment.
The mobile phone antenna of the fourth embodiment can be integrally
manufactured by punching or etching, like the first embodiment.
Also, in this antenna, a first resonance frequency is determined
by the first and second radiation elements 11, 13 and a second resonance
frequency is determined by the second and third radiation elements
13, 14. The first and second resonance frequencies can be adjusted
by the length X1 of the coupling adjuster 12 on the top face, the
length X2 of the coupling adjuster 15 on the side face, the clearance
t1 between the first radiation element 11 and the coupling adjuster
12 on the top face and the clearance t2 between the third radiation
element 14 and the coupling adjuster 15 on the side face. Hence,
this can prevent displacement in DCS band and displacement in resonance
frequency both in GSM band and DCS band. Also, the bandwidth at
each wavelength band can be adjusted.
FIG. 8 is a perspective view showing a mobile phone antenna in
the fifth preferred embodiment according to the invention. The mobile
phone antenna of the fifth embodiment is applied to mobile phones
other than folding type mobile phone. It is composed such that the
LCD ground 23 and the inter-board ground connector 41 are omitted
from the mobile phone antenna of the third embodiment. The other
components are the same as those of the third embodiment.
In the fifth embodiment, the bandwidth of mobile phones other than
folding type mobile phone can be broadened.
Also, the mobile phone antenna in the first, second and third embodiment
can be applied to mobile phones other than folding type mobile phone
while removing the LCD ground 23 and the inter-board ground connector
41.
Although, in the first to fifth embodiments, the radiation element
10 is connected through the ground connector 42 to the board ground
32, the ground connector 42 may be connected to the LCD ground 23
or ground of the other electronic parts, mechanism parts (shielding
cover, frame etc.)
Although the mobile phone antennas in the first to fifth embodiments
are applied to mobile phone, they may be applied to PHS (personal
handyphone system) mobile phone and PDA (personal digital assistant).
Although, in the first to fourth embodiments, the ground includes
the LCD ground 23 and board ground 32, it may include one of them
or more than two.
Although the invention has been described with respect to the specific
embodiments for complete and clear disclosure, the appended claims
are not to be thus limited but are to be construed as embodying
all modifications and alternative constructions that may occur to
one skilled in the art which fairly fall within the basic teaching
herein set forth. |