U.S. patent application number 09/834806 was filed with the patent office on 2001-09-06 for portable telephone.
This patent application is currently assigned to Kyocera Corporation. Invention is credited to Nakada, Shinichi, Tsumuraya, Mamoru.
Application Number | 20010019963 09/834806 |
Document ID | / |
Family ID | 17767046 |
Filed Date | 2001-09-06 |
United States Patent
Application |
20010019963 |
Kind Code |
A1 |
Nakada, Shinichi ; et
al. |
September 6, 2001 |
Portable telephone
Abstract
A digital portable radio having a plane antenna, which minimizes
the area of a board occupied by a built-in antenna without
deteriorating gain. More specifically, a built-in antenna radiation
element having a conductor capable of being electrically connected
to a power feed circuit provided on the circuit substrate is fixed
on the internal wall of the casing. A built-in antenna which
accomplishes high gain and occupies a small area is obtained.
Further, the antenna radiation element is formed from a metal plate
and has a branch where one end of a longer radiation element formed
from a thin metal plate is connected to one end of a shorter
radiation element, and the other end of each of the radiation
elements is open. Further, gap is formed by bringing the open end
of the longer radiation element in close proximity to the open end
of the shorter radiation element. Impedance matching is
accomplished by utilization of coupling capacitance developed in
the gap. The antenna radiation element becomes a quarter .lambda.
non-grounding multiple resonance built-in antenna by feeding of
power to the branch. This antenna is fitted on the internal wall of
the casing of the portable radio.
Inventors: |
Nakada, Shinichi; (Kanagawa,
JP) ; Tsumuraya, Mamoru; (Kanagawa, JP) |
Correspondence
Address: |
HOGAN & HARTSON L.L.P.
500 S. GRAND AVENUE
SUITE 1900
LOS ANGELES
CA
90071-2611
US
|
Assignee: |
Kyocera Corporation
|
Family ID: |
17767046 |
Appl. No.: |
09/834806 |
Filed: |
April 12, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09834806 |
Apr 12, 2001 |
|
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|
09040863 |
Mar 18, 1998 |
|
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|
6243592 |
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Current U.S.
Class: |
455/575.7 ;
455/572 |
Current CPC
Class: |
H01Q 9/42 20130101; H01Q
1/243 20130101; H01Q 1/36 20130101; H04B 1/3833 20130101; H01Q
5/371 20150115 |
Class at
Publication: |
455/550 ;
455/572 |
International
Class: |
H04M 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 23, 1997 |
JP |
HEI.9-291295 |
Claims
What is claimed is:
1. A portable radio comprising: a case; an antenna radiation
element formed from a thin metal plate, said antenna radiation
element being mounted on the internal wall of said case; a circuit
board on which a circuit is provided, said circuit board being
attached to said case; and a power feed terminal which establishes
an electrical connection between said antenna radiation element and
said circuit provided on the circuit board.
2. A portable radio as claimed in claim 1, wherein the power feed
terminal is fixed on the circuit board in advance, and the power
feed terminal is brought into forced contact with the antenna
radiation element mounted on the internal wall of the case when the
circuit board is attached to the case.
3. A portable radio as claimed in claim 1, wherein the power feed
terminal is integrally formed with the antenna radiation element
beforehand, and the power feed terminal is brought into forced
contact with a power feed land formed on the circuit substrate.
4. A portable radio as claimed in claim 1, wherein a positioning
protuberance is provided on the internal wall surface of the casing
to fix the antenna radiation element on the internal wall of the
casing, and positioning holes used for receiving the protuberance
are formed in the antenna radiation element.
5. A portable radio as claimed in claim 1, wherein said antenna
radiation element which includes a branch where one end of a longer
radiation element is connected to one end of a shorter radiation
element, and the other ends of the longer and shorter radiation
elements which are open ends and are positioned in close proximity
to each other so as to form gap between them, and wherein impedance
matching is accomplished by means of the coupling capacitance
developed in the gap, and power is fed to the branch.
6. A plane antenna comprising: an antenna radiation element which
includes a branch where one end of a longer radiation element is
connected to one end of a shorter radiation element, and the other
ends of the longer and shorter radiation elements which are open
ends and are positioned in close proximity to each other so as to
form gap between them, wherein impedance matching is accomplished
by means of the coupling capacitance developed in the gap, and
power is fed to the branch.
7. A plane antenna as claimed in claim 6, wherein said antenna
radiation element is located on an internal wall of a casing, and a
circuit board which is located within the casing and has power feed
means and the ground, wherein the power feed means feeds power to
the branch to thereby produce multiple resonance between the branch
and the ground.
8. A plane antenna as claimed in claim 7, wherein said power feed
means is made of elastic member and is brought into contact with
the branch.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a portable radio, such as
primarily a digital portable telephone having a built-in plane
antenna, and more particularly to the space-saving structure of the
built-in antenna. Further, the invention relates to a plane antenna
which is mainly used in a digital portable radio (a portable
telephone).
[0002] A plane antenna has been widely used as a built-in antenna
of a digital portable telephone because of its advantages of
compactness and high gain. The built-in antenna of the portable
telephone is directly mounted on a circuit substrate.
[0003] In recent years, a portable telephone market has spread into
wide use, and the portable telephone is miniaturized so as to
sufficiently fit in a pocket. The portable telephone tends to be
miniaturized further. In conjunction of miniaturization of the
portable telephone, there is also a demand for a reduction in the
space occupied by the built-in antenna attached to the portable
telephone.
[0004] However, if the size of the portable telephone is reduced
further, it becomes difficult to ensure space for the built-in
antenna. This is because as the size of the case is reduced, a
circuit originally made up of a plurality of circuit boards is
constituted of only one board. In addition, the circuit board
itself becomes more compact. For these reasons, the electronic
components are mounted on the circuit board in high density.
Accordingly, the space required to mount the built-in antenna on
the board is reduced, the antenna must be formed in small size. In
general, a small-sized antenna entails the deterioration of gain,
which in turn may result in a drop in the performance of the
portable telephone. However, if an attempt is made to increase the
size of the built-in antenna, it becomes impossible to store an
electronic circuit in the case.
[0005] Aside from the foregoing problem, there is a lot of talk
about the problem related to a line. More specifically, the
frequency of utilization of a line is increased in proportion to an
increase in the number of portable telephones, and traffic becomes
nearly full. The number of circuit lines is increased by
utilization of a frequency range of the analog portable telephone
as measures against the increase in the traffic. However, this
method requires two receiving ranges. It is impossible to provide
an existing built-in antenna having a narrow range with the
sensitivity which covers two ranges. Therefore, there is needed an
antenna which produces two resonance ranges (or multiple resonance)
and has sensitivity over two ranges.
SUMMARY OF THE INVENTION
[0006] To solve the foregoing problem and to minimize the area
occupied by a board of a built-in antenna without deterioration of
a gain, a radiation element of a built-in antenna is mounted on an
internal wall of a case, and a conductor is provided which is
capable of electrically connecting the radiation element to a power
feed circuit provided on the board, thereby providing a built-in
antenna which achieves high gain and requires the space occupied by
the circuit board.
[0007] To ensure sensitivity over to receiving ranges, an antenna
radiation element is provided with a branch where one end of a
longer radiation element is connected to one end of a shorter
radiation element. The other ends of the longer and shorter
radiation elements are open ends and are positioned in close
proximity to each other so as to form gap between them. Impedance
matching is accomplished by means of the mutual coupling
capacitance developed in the gap, and power is fed to the
branch.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a side cross-sectional view showing a portable
radio according to a first embodiment of the present invention;
[0009] FIG. 2 is a side cross-sectional view showing a portable
radio according to a second embodiment of the present
invention.
[0010] FIG. 3 is a front view showing an antenna radiation element
according to the third embodiment of the present invention; and
[0011] FIGS. 4A to 4C are plots showing the characteristics of the
antenna according to present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0012] Embodiments of the present invention will be described
herein below.
Embodiment 1
[0013] FIG. 1 is a side cross-sectional view showing a case of a
portable radio according to the present invention. In FIG. 1, a
portion of the case located in an upper area of the drawing sheet
designates the back of the case, whereas a portion of the case
located in a lower area of the drawing sheet designates the front
of the case. Reference numeral 1 designates a plastic rear case
which constitutes the back of the case; and 2 designates a front
case which constitutes the front of the case. Reference numeral 3
designates a plane antenna radiation element made of thin metal
plate. Reference 4 designates a power feed terminal; 5 a contact; 6
a circuit board; 7 an LCD; 8 a shield case used for the purpose of
electromagnetic shielding; 9 an RF circuit; 10 an extendable
transmit/receive antenna capable of being housed or extended; 11 a
protuberance used for the purpose of positioning the antenna
radiation element 3; 12 a double-sided table used for fixing the
antenna element 3 on the internal wall of the rear case 1; 13
designates a power feed land; 14 a digital circuit component; and
15 a replaceable battery.
[0014] The antenna element 3 is formed from a thin metal plate
(having a thickness of about 0.1 mm) composed of phosphor bronze.
The antenna element 3 is a radiation element having a
quarter-wavelength electrical length such as that causes the
antenna to resonate in a receiving area so as to be able to receive
an electronic wave transmitted from a base station, thereby
constituting a quarter .lambda. (wavelength) non-contact antenna.
Several holes are formed in the antenna radiation element 3, and
the positioning protuberance 11 of the rear case 1 is fitted into
one of the holes at the time of assembly of a radio, thereby
positioning the antenna element 3.
[0015] The somewhat large power feed land 13 formed on the circuit
board 6 is connected to a receiving circuit (not shown) via an
unillustrated power feed circuit and an unillustrated matching
circuit. The power feed terminal section 4 is made of electrically
conductive material and is soldered to the power feed land 13. The
contact 5 comes into an appropriate position of the antenna
radiation element 3 under pressure, thereby maintaining conduction
of electricity. The reason for this is that the rear case 1 is
assembled or disconnected from the portable radio without
difficulties.
[0016] With the foregoing construction, the antenna radiation
element 3 mounted on the internal wall of the rear case 1 produces
resonance with respect to a ground (or an internal layer) of the
circuit board 6 positioned below the antenna radiation element 3.
The electric power thus received enters the receiving circuit via
the power feed terminal 4, the power feed land 13, and the power
feed line.
[0017] As can be seen from the foregoing description, the antenna
radiation element 3 is not directly positioned on the circuit board
6 and is fixedly fitted on the internal wall of the rear case 1
within the area occupied by the built-in antenna made up of the
antenna radiation element 3 positioned above the circuit board 6.
Therefore, only the power feed terminal 4 of the circuit board 6 is
associated with the built-in antenna, and hence the area of the
circuit board 6 occupied by the built-in antenna is considerably
reduced. Eventually, the space of the circuit board 6 is
correspondingly increased. So long as a component has a small
height such as a digital circuit component 14, any component can be
positioned on the circuit board 6 immediately below the antenna
radiation element 3.
[0018] Since the antenna radiation element 3 uses the internal wall
of the rear case 1, the element is not subjected to space limits.
Because of this, the antenna radiation element 3 can be formed into
a big size, thereby resulting in an increase in gain.
[0019] Even in the following respects, the increase in the size of
the antenna radiation element 3 exerts a good influence on an
increase in gain. There is a tendency for gain to increase as the
distance between the ground and the radiation element is increased.
Since the present invention eliminates a gap between the antenna
radiation element 3 and the rear case 2, the distance between the
circuit substrate 6 (ground) and the antenna radiation element 3
becomes the maximum height which the portable radio can accomplish,
thereby enabling a significant increase in gain. Further, since the
antenna radiation element 3 is formed from a thin metal plate in
the present invention, the gain is prevented from being
deteriorated by a dielectric loss.
[0020] Further, since the antenna radiation element 3 is formed
from a metal plate, the outer shape of the antenna radiation
element 3 can be accurately formed, enabling prevention of
irregularities in the outer shape.
[0021] The positioning protuberance 11 is formed on the rear case 1
as means for positioning the antenna radiation element 3 on the
rear case 1 in the previous embodiment, and the holes corresponding
to the positioning protuberance 11 are formed in the antenna
radiation element 3 in order to position the antenna radiation
element. However, the positioning means is not limited to the
foregoing holes and the protuberance. Guide means, such as lines or
grooves, may be formed in the rear case 1 so as to correspond to
the outer shape of the antenna radiation element 3.
[0022] Further, the power feed terminal 4 may be a conductor of any
shape, so long as the terminal may electrically connect the antenna
radiation element 3 to the power feed land 13. The power feed
terminal 14 may be formed into a spring or a leaf.
[0023] Finally, because the antenna radiation element 3 is formed
from a light-weight thin metal plate, the antenna radiation element
3 is bonded to the internal wall of the rear case 1 by means of the
double-sided tape 12 in the previous embodiment. However, the
fixing means is not limited to the double-sided tape. The antenna
radiation element 3 may be bonded to the internal wall by means of
an adhesive. Alternatively, the positioning protuberance 11 may be
thermally fused and pushed to thereby extend the size of the
protuberance, whereby the antenna radiation element 3 may be fixed
by the protuberance.
[0024] In an example in which the present embodiment is applied to
a digital portable telephone which operates in a band of 800 MHz,
the area of the circuit board 6 occupied by the power feed terminal
4 measures 5.times.4 mm (length and width) and is considerably
smaller than that required by a conventional portable telephone.
Since the antenna radiation element itself utilizes the internal
wall of the rear case, the antenna radiation element can be formed
to a size of 24 mm.times.24 mm.times.7 mm (length x width x height
from the ground). In contrast with the conventional antenna
radiation element having a limited size, the antenna radiation
element can be formed in large size.
Embodiment 2
[0025] FIG. 2 shows a second embodiment of the present invention.
The elements which are the same as those of the first embodiment
will be assigned the same reference numerals, and their
explanations will be omitted. As is obvious from FIG. 2, the
portable radio according to the second embodiment is different from
that according to the first embodiment in the structure of the
power feed terminal 4. However, the portable radio according to the
second embodiment achieves high gain, as does the portable radio
according to the first embodiment. In the case of the portable
radio according to the first embodiment shown in FIG. 1, in
consideration of mass production of the portable radio, a retaining
tool is required to retain the power feed terminal 4 in such a way
that the power feed terminal 4 can come into contact with the
antenna radiation element 3 at the time of assembly of the portable
radio. As a matter of course, such a retaining tool occupies a
slight area of the circuit board 6.
[0026] To solve this problem, in the second embodiment, a portion
of the thin metal plate forming the antenna radiation element 3 is
bent, so that the power feed terminal 4 is integrally formed. The
tip end of the power feed terminal 4 is further bent so as to form
the contact 5. When the circuit board 6 is attached to the rear
case 1 at the time of assembly of a radio, the contact 5
resiliently comes into contact with the power feed land 13 of the
circuit board 6 under pressure and is electrically connected to the
circuit on the circuit board 6.
[0027] As mentioned previously, it is only essential that the power
feed terminal 4 be formed by processing a thin metal plate. If a
portion of the antenna radiation element 3 formed from a thin plane
metal plate is bent so as to form the power feed terminal 4, the
power feed terminal 4 can be formed integrally with the antenna
radiation element 3. With such a construction, both the antenna
radiation element and the power feed terminal can be formed from
the same material. Since it is only add a bending operation to the
manufacture of the antenna radiation element, the superior
productivity of the portable radio can be achieved. The power feed
terminal 4 may be formed into any shape, so long as the electrical
connection between the antenna radiation element 3 and the power
feed land 13 is maintained when the rear case 1 is mounted on the
circuit board 6.
[0028] The antenna radiation element 3 can be soldered integrally
to the power feed terminal 4. The power feed terminal 4 may be
formed from a conductor of any shape, such as a spring or a leaf
spring, so long as the antenna radiation element 3 can be
electrically connected to the power feed land 12.
[0029] In one example in which the second embodiment is applied to
a digital portable telephone which operates in a band of 800 MHz,
only the power feed land 13 occupies the area measuring 6.times.3
mm (length x width) on the circuit substrate 6 of the built-in
antenna. No other constituent elements associated with the antenna
radiation element 3 are disposed on the circuit board 6, thereby
minimizing the occupied area of the circuit board. In comparison
with the area occupied by the power feed land 13 in the first
embodiment, the area occupied by the same can be reduced further in
the second embodiment.
[0030] As mentioned previously, only the power feed land occupies a
part of the area of the circuit board, and the need to place other
constituent elements associated with the built-in antenna on the
circuit board 6 is completely eliminated, thereby effectively
reducing the size of the portable radio having a built-in
antenna.
[0031] As mentioned previously, according to the present invention,
it is possible to implement a built-in antenna which occupies a
smaller area of the circuit board of the portable radio and
achieves high gain. Further, a built-in antenna is positioned on
the internal wall of the casing of the radio, and other components
can be arranged on the circuit board in the space of the circuit
board formed immediately below the built-in antenna. As a result,
the size of the circuit board; namely, the size of the portable
radio, can be readily reduced.
Embodiment 3
[0032] With regard to a plane antenna housed in a casing of a
portable radio, there is formed a quarter .lambda. non-grounding
multiple resonance antenna comprising an antenna radiation element;
a branch where one end of a longer radiation element and one end of
a shorter radiation element are connected together; the other ends
of the longer and shorter radiation elements which are formed into
open ends and are brought into close proximity to each other so as
to form a gap; and coupling capacitance which develops in the gap
and is used for impedance matching. Power is fed to the branch.
Such an antenna radiation element is positioned on the internal
wall of the casing of the portable radio, and the branch of the
antenna radiation element is electrically connected to the power
feed circuit provided on the circuit board within the casing. A
ground is formed as power feed means in the circuit board within
the casing. Power is fed to the branch by the power feed means, so
that the antenna radiation element produces multiple resonance
between the branch and the ground of the circuit board. Further,
the power feed means has resilience and comes into elastic contact
with the branch. In order to place the antenna radiation element in
a predetermined position on the internal wall of the casing,
antenna positioning means is provided in a predetermined location
on the internal wall of the casing. A protuberance is used as
antenna positioning means, and in such a case a hole is formed in
the antenna radiation element.
[0033] FIG. 3 is a front view showing the antenna radiation element
3 mounted on the rear case 1, which has a branched shape and is
made of a thin metal plate. Reference numeral 17 designates a
longer radiation element section; 18, a shorter radiation element
section; 16, a branch formed by connection of the radiation
elements 17 and 18; and 19, a gap as a result of the open ends of
the radiation elements 17, 18 coming in proximity to each
other.
[0034] The antenna radiation element 3 is formed from a thin metal
plate (having a thickness of about 0.1 mm) composed of phosphor
bronze. The antenna radiation element 3 comprises a longer
radiation element 17 having a length to produce resonance in a
lower frequency range of two receiving ranges and a short radiation
element 18 having a length to produce resonance in a higher
frequency range. One end of each of the radiation elements 17, 18
is connected to the branch 16, and the other end of each of the
radiation elements is open. The antenna radiation element 3 as a
whole has a branched shape, and a plurality of small holes are
formed in the antenna radiation element 3 so as to fittingly
receive the positioning plastic protuberances 11 formed on the rear
case for the purpose of positioning. As a result of power being fed
to the branch 16, the antenna radiation element is capable of
producing multiple resonance in two receiving ranges so as to be
able to receive two different waves transmitted from the base
station.
[0035] The somewhat large power feed land 13 formed on the circuit
board 6 is connected to a receiving circuit (not shown) via a power
feed circuit (not shown) and an unillustrated matching circuit. The
power feed terminal section 4 is made of electrically conductive
material and is soldered to the power feed land 13. The contact 5
comes into an appropriate position of the antenna radiation element
3 under pressure, thereby maintaining conduction of electricity.
The reason for this is that the rear case 1 is assembled or
disconnected from the portable radio without difficulties. In
short, the rear case 1 having the antenna radiation element 3
mounted thereon is attached to the front case 2 having the circuit
substrate 6 mounted thereon at the time of assembly. The contact 5
of the power feed terminal 4 mounted on the internal circuit board
6 comes into resilient contact with the branch 16 of the antenna
radiation element 3.
[0036] With the foregoing construction, multiple resonance arises
between the antenna radiation element 3 mounted on the internal
wall of the rear case 1 by the double-sided tape 12 produces
multiple resonance and the ground (or an internal layer) of the
circuit board 6 positioned below the antenna radiation element 3.
The electric power thus received enters the receiving circuit from
the antenna element 3 via the power feed terminal 4, the power feed
land 13, and the power feed line. The coupling capacitance is
controlled by adjusting the width of the gap developed when the
open end of the longer radiation element 17 is brought into close
proximity to the open end of the shorter radiation element, thereby
achieving optimum impedance matching. As can be seen from the
foregoing description, the multiple resonance built-in antenna
according to the present invention can be implemented by a simple
configuration in which power is fed to the antenna radiation
element 3, which is formed from a thin metal plate into a branched
shape, via the branch 16. Therefore, the antenna can be switched to
a singular resonance type antenna to a multiple resonance antenna
by changing merely the shape of the metal plate. Further, the
antenna is of non-grounding type, and therefore the need for
grounding is eliminated. Accordingly, the power-feed structure can
be simplified. As a result, the cost of the portable radio is
reduced, and the mass-productivity of the same is improved.
[0037] The antenna radiation element 3 is not provided on the
circuit board 6 and is fitted on the internal wall of the rear case
1. Consequently, only the power feed terminal is provided on the
circuit board 6, and the need of grounding is eliminated.
Therefore, the area of the board occupied by the built-in antenna
is minimized, and the space of the board is increased
correspondingly. A component, such as a digital circuit component
14, can be placed on the board immediately below the antenna
radiation element 3, so long as the component has a small
height.
[0038] The antenna radiation element 3 utilizes the internal wall
of the rear case 1, and circuit components do not limit the space
for the antenna radiation element 3. The radiation element can be
formed into large size, thereby resulting in an increase in
gain.
[0039] In a portable telephone which is made compact more and more,
when the long radiation element 17 and the short radiation element
18 are mounted on the internal wall of the rear case of the
portable telephone, the radiation elements are positioned close to
each other, resulting in noticeable mutual coupling capacitance.
The present invention actively utilizes this coupling capacitance.
Even if the radiation elements come into close proximity to each
other, impedance matching can be ensured by adjusting the gap to an
appropriate value.
[0040] The power feed terminal 4 may be a conductor of any shape,
so long as the terminal may electrically connect the antenna
radiation element 3 to the power feed land 13. The power feed
terminal 14 may be formed into a spring or a leaf.
[0041] In an example in which the present embodiment is applied to
a digital portable telephone which operates in a band of 800 MHz,
there are two receiving ranges; namely, a band ranging from 810 to
830 MHz and a band ranging from 870 to 885 MHz. Since the antenna
radiation element utilizes the internal wall of the rear case, the
antenna radiation element can be formed to a size of 24 mm.times.30
mm.times.7 mm (length x width x height from the ground). The area
of the circuit board 6 occupied by the power feed terminal 4
measures 5.times.4 mm (length and width) and is considerably
smaller than that required by a conventional portable telephone.
Further, FIG. 4A shows the characteristics of impedance matching
obtained when the open end of the longer radiation element and a
short radiation element is optimized. If the gap is reduced, the
state of match is changed to such as that shown in FIG. 4B. In
contrast, if the gap is increased, the state of match is changed to
such as that shown in FIG. 4C.
[0042] The present invention can implement multiple resonance and
space saving suitable for a portable radio.
* * * * *