[0001] The present invention relates to an antenna device for use in a mobile communication
apparatus such as a portable telephone.
[0002] As an antenna for use in conventional mobile communication apparatuses, a circuit
board surface mount type antenna (hereinafter referred to as "surface mount type antenna")
is proposed in the specification of Japanese Patent Application No. 6-81652 (unpublished)
which is related to commonly assigned US-A-5,510,802 issued April 23, 1996. Fig. 7
shows this surface mount type antenna, and Figs. 8 to 11 show an example of the surface
mount type antenna in which an antenna switch circuit is mounted as an antenna circuit.
[0003] Referring to Fig. 7, a member 1 is a dielectric substrate in the form of a rectangular
prism made of, for example, a ceramic or resin, and a pair of grounding electrodes
2 are formed on opposite side surfaces of the dielectric substrate 1 corresponding
to the longer sides of the two major surfaces of the dielectric substrate 1 while
connection electrodes 3a, 3b, and 3c are formed on the other opposite side surfaces
corresponding to the shorter sides. A member 4 is a metallic chassis made of, for
example, copper or a copper alloy and having, as viewed in a cross section, the shape
of a rectangle open at one side. The metallic chassis 4 has a rectangular flat radiating
portion 5, and two fixing portions 6 and 7 bent downwardly and perpendicularly from
shorter-side opposite ends of the radiating portion 5. A current supply terminal 8
and a grounding terminal 9 are formed integrally on the extreme end of the fixing
portion 6. The fixing portion 6 is reduced in length relative to the fixing portion
7 to form the current supply terminal 8 and the grounding terminal 9. The overall
length of the fixing portion 6, including the length of the current supply terminal
8 and the grounding terminal 9, and the overall length of the fixing portion 7 are
respectively set so as to be larger than the thickness of the dielectric substrate
1.
[0004] The dielectric substrate 1 is inserted into the metallic chassis 4 with the shorter-side
side surfaces of the dielectric substrate 1 brought into contact with inner surfaces
of the fixing portions 6 and 7 of the metallic chassis 4. At this time, a vacant space
10 is formed between the radiating portion 5 of the metallic chassis 4 and the obverse
surface of the dielectric substrate 1 due to the difference between the values of
the thickness of the dielectric substrate 1 and the length of the fixing portion 6
including the current supply terminal 8 and the grounding terminal 9 and the fixing
portion 7. The connection terminal 3a of the dielectric substrate 1 is soldered to
the fixing portion 7 of the metallic chassis 4. Also, the connection terminals 3b
and 3c of the dielectric substrate 1 are respectively soldered to the current supply
terminal 8 and the grounding terminal 9 of the metallic chassis 4. Thus, a surface
mount type antenna 13 is constructed.
[0005] A main circuit board 15 has, on its obverse surface, a micro-strip line 16 for supplying
an antenna current, connected to an antenna circuit, e.g., an antenna switch circuit
(not shown), and grounding electrodes 17a insulated from the micro-strip line 16.
Also, a grounding electrode 17b is formed generally over the entire reverse surface
of the main circuit board 15.
[0006] The surface mount type antenna 13 is placed on the obverse surface of the main circuit
board 15, the current supply terminal 8 and the micro-strip line 16 are soldered to
each other, and the pair of grounding electrodes 2 and the grounding electrode 9 are
soldered to the grounding electrodes 17a on the obverse surface of the main circuit
board 15. The surface mount type antenna 13 is thus mounted on the main circuit board
15 in a surface mount manner. Electric waves are transmitted or received through the
radiating portion 5 of the metallic chassis 4.
[0007] Referring then to Figs. 8 and 9, a member 21 is a multilayer dielectric substrate
in the form of a rectangular prism made of, for example, a ceramic or a resin. A transmission
input portion TX, a receiving output portion RX, control input portions VC1 and VC2
of an antenna switch circuit and a plurality of grounding electrodes 22 are formed
as external electrodes on opposite side surfaces of the dielectric substrate 21 corresponding
to the longer sides of the two major surfaces of the dielectric substrate 21 while
connection electrodes 23a, 23b, and 23c are formed on the other opposite side surfaces
corresponding to the shorter sides. As circuits elements, a strip line 24a and capacitors
24b are formed in the dielectric substrate 21 while diodes 24c and printed resistors
24d are mounted on the obverse surface of the dielectric substrate 21, thus forming
an antenna switch circuit 24. An antenna output portion 24e of the antenna switch
circuit 24 in the dielectric substrate 21 is connected to the connection electrode
23b on the side surface, and the circuit elements are connected to each other by internal
electrodes or via holes.
[0008] A member 26 is a metallic chassis made of, for example, copper or a copper alloy
and having, as viewed in a cross section, the shape of a rectangle open at one side.
The metallic chassis 26 has a rectangular flat radiating portion 27, and two fixing
portions 28 and 29 bent downwardly and perpendicularly from shorter-side opposite
ends of the radiating portion 27. A current supply terminal 30 and a grounding terminal
31 are formed integrally on the extreme end of the fixing portion 28. The fixing portion
28 is reduced in length relative to the fixing portion 29 to form the current supply
terminal 30 and the grounding terminal 31. The overall length of the fixing portion
28, including the length of the current supply terminal 30 and the grounding terminal
31, and the overall length of the fixing portion 29 are respectively set so as to
be larger than the thickness of the dielectric substrate 21.
[0009] The dielectric substrate 21 is inserted into the metallic chassis 26 with the shorter-side
side surfaces of the dielectric substrate 21 brought into contact with inner surfaces
of the fixing portions 28 and 29 of the metallic chassis 26. At this time, a vacant
space 32 is formed between the radiating portion 27 of the metallic chassis 26 and
the obverse surface of the dielectric substrate 21 due to the difference between the
values of the thickness of the dielectric substrate 21 and the length of the fixing
portion 28 including the current supply terminal 30 and the grounding terminal 31
and the fixing portion 29. The connection terminal 23a of the dielectric substrate
21 is soldered to the fixing portion 29 of the metallic chassis 26. Also, the connection
terminals 23b and 23c of the dielectric substrate 21 are respectively soldered to
the current supply terminal 30 and the grounding terminal 31 of the metallic chassis
26. Thus, a surface mount type antenna 35 is constructed.
[0010] Connection electrodes 37, 38, 39, and 40 and grounding electrodes 41a insulated from
the connection electrodes 37 to 40 are formed on the obverse surface of a main circuit
board 36. A grounding electrode 41b are formed on the entire reverse surface of the
main circuit board 36.
[0011] The surface mount type antenna 35 is placed on the obverse surface of the main circuit
board 36, and the transmission input portion TX, the receiving output portion RX and
the control input portions VC1 and VC2 are respectively soldered to the connection
electrodes 37 to 40 while the grounding electrodes 22 and the grounding terminal 31
are soldered to the grounding electrodes 41a. The surface mount type antenna 35 is
thus mounted on the main circuit board 36 in a surface mount manner. Electric waves
are transmitted or received through the radiating portion 27 of the metallic chassis
26.
[0012] Fig. 10 shows a well-known circuit as an example of the antenna switch circuit 24,
and Fig. 11 is a block diagram of the antenna 35. An antenna circuit such as a low-pass
filter or a band-pass filter may be mounted as well as the antenna circuit 24 shown
in Fig. 10.
[0013] A dielectric-loaded monopole antenna capable of being mounted on a circuit board
in a surface mount manner is also proposed by the assignee of the present invention
in the specification of Japanese Patent Application No. 6-034759 (unpublished) which
is related to commonly assigned US-A-5,581,226 issued December 3, 1996. Fig. 12 shows
this dielectric-loaded monopole antenna. A member 71 shown in Fig. 12 is a dielectric
substrate generally in the form of a rectangular prism. A generally cylindrical through
hole 72 is formed in the dielectric substrate 71 so as to be open in opposite side
surfaces of the same. A radiating electrode 73 made of, for example, copper is formed
on the internal surface of the through hole 72. A current supply terminal 74 electrically
connected to the radiating electrode 73 is continuously formed from one of the side
surfaces in which the through hole 72 is open to the reverse surface of the dielectric
substrate 71. Grounding terminals 75a and 75b are formed on the opposite sides of
the current supply terminal 74. A grounding terminal 75c is formed on the other side
surface in which the through hole 72 is open. Thus, a dielectric-loaded monopole antenna
76 is constructed.
[0014] A main circuit board 77 has, on its obverse surface, a micro-strip line 78 for supplying
an antenna current, which is a transmission line connected to an antenna circuit,
e.g., an antenna switch circuit (not shown), and grounding electrodes 79a insulated
from the micro-strip line 78. Also, a grounding electrode 79b is formed generally
over the entire reverse surface of the main circuit board 77.
[0015] The dielectric-loaded monopole antenna 76 is placed on the obverse surface of the
main circuit board 77, the current supply terminal 74 and the micro-strip line 78
are soldered to each other, and the grounding terminals 75a, 75b and 75c are soldered
to the grounding electrodes 79a on the obverse surface of the main circuit board 77.
The dielectric-loaded monopole antenna 76 is thus mounted on the main circuit board
77 in a surface mount manner. Electric waves are transmitted or received through the
radiating electrode 73.
[0016] The transmission output from the antenna circuit, e.g., an antenna switch circuit
when the antenna is removed is regulated by the Wireless Telegraphy Act. Therefore,
there is a need to accurately measure the value of the output.
[0017] The above-described surface mount type antenna 13 is mounted on the main circuit
board 15 in a surface mount manner by soldering the current supply terminal 8, the
grounding electrodes 2 and the grounding terminal 9. Therefore, it is difficult to
dismount the surface mount type antenna 13, once the antenna 13 is mounted on the
main circuit board 15. On the other hand, after the surface mount type antenna 13
has been mounted on the surface of the main circuit board 15, the transmission output
of the antenna switch circuit is loaded with the impedance of the surface mount type
antenna 13, because the current supply terminal 8 is connected to an antenna switch
circuit (not shown) through the micro-strip line 16. In such a situation, the transmission
output of the antenna switch circuit cannot be accurately measured.
[0018] The surface mount type antenna 35 is mounted on the main circuit board 36 by soldering
the transmission input portion TX, the receiving output portion RX, the control input
portions VC1 and VC2, the grounding electrode 22 and grounding terminal 31. Therefore,
it is difficult to dismount the antenna 35 once the antenna 35 is mounted on the main
circuit board 36. After the surface mount type antenna 35 has been mounted on the
surface of the main circuit board 36, the transmission output of the antenna switch
circuit 24 is loaded with the impedance of the surface mount type antenna 35, because
the current supply terminal 30 is connected to the antenna output portion 24e of the
antenna switch circuit 24. As a result, the transmission output of the antenna switch
circuit 24 cannot be accurately measured.
[0019] Further, the dielectric-loaded monopole antenna 76 is mounted on the main circuit
board 77 in a surface mount manner by soldering the current supply terminal 74 and
the grounding terminals 75a, 75b and 75c. Therefore, it is difficult to dismount the
antenna 76 once the antenna 76 is mounted on the main circuit board 77. After the
dielectric-loaded monopole antenna 76 has been mounted on the surface of the main
circuit board 77, the transmission output of an antenna switch circuit (not shown)
is loaded with the impedance of dielectric-loaded monopole antenna 76, because the
current supply terminal 74 is connected to the antenna switch circuit through the
micro-strip line 78. As a result, the transmission output of the antenna switch circuit
cannot be accurately measured.
[0020] Therefore, an electrical or mechanical switch for a change to a transmission output
measuring terminal is required to accurately measure the transmission output of the
antenna circuit, i.e., an antenna switch circuit or the like. If such a switch is
provided, the manufacturing cost is increased.
[0021] It is the object of present invention to provide an antenna device designed so that
the transmission output of an antenna circuit when the antenna device is removed,
regulated by the Wireless Telegraphy Act, can be measured easily and accurately without
using any electrical or mechanical switch for a change to a transmission output measuring
terminal, even after the antenna device has been mounted to a main circuit board.
[0022] This object is achieved by a surface mount type antenna device according to claim
1.
[0023] To achieve the above-described object, according to one aspect of the present invention,
there is provided an antenna device comprising a current supply element, and a radiating
element provided in combination with the current supply element and separable from
the current supply element, wherein a transmission output measuring terminal is connected
to the current supply element through a capacitor.
[0024] In the above-described antenna device, according to another aspect of the invention,
the radiating element is accommodated in a gap formed between a main circuit board
on which the current supply element is mounted and an outer case in which the main
circuit board is accommodated, one major surface of the radiating element facing the
current supply element.
[0025] In the above-described antenna device, according to still another aspect of the invention,
the current supply element is connected to a first transmission line which is formed
on the main circuit board to supply an antenna current, and a multilayer chip capacitor
and the transmission output measuring terminal are connected to the first transmission
line.
[0026] In the above-described antenna device, according to a further aspect of the invention,
the current supply element is formed by inserting a dielectric substrate into a metallic
chassis, and an incorporated capacitor connected to the transmission output measuring
terminal is formed in the dielectric substrate by providing a first capacitor electrode
connected to the first transmission line and a second capacitor electrode connected
to a second transmission line for transmission output measurement formed on the main
circuit board.
[0027] In the above-described antenna device, according to still a further aspect of the
invention, a space is provided between the metallic chassis and the dielectric substrate.
[0028] In the above-described arrangement, the current supply element is mounted on the
main circuit board with the radiating element accommodated in the gap formed between
the main circuit board and the outer case in which the main circuit board is accommodated.
Therefore, it is possible to easily separate the radiating element from the current
supply element by removing the outer case from the main circuit board, even after
the current supply element has been mounted on the main circuit board.
[0029] The transmission output measuring terminal is connected to the current supply element
through the multilayer chip capacitor or the incorporated capacitor. Accordingly,
the capacitance of the multilayer chip capacitor or the incorporated capacitor is
added to the transmission output from the current supply element at the transmission
output measuring terminal. The influence of the inductance of the current supply element
upon the measured value of the transmission output from the current supply element
at the transmission output terminal can be canceled by the capacitance of the multilayer
chip capacitor or the incorporated capacitor connected to the current supply element.
Consequently, the transmission output of the antenna circuit can be measured accurately
by removing the influence of the inductance of the current supply element.
[0030] According to the above-described arrangement, even after the current supply element
has been mounted on the main circuit board, the radiating element can be removed to
accurately measure the transmission output of the antenna circuit as the transmission
output measured when the antenna device is removed as prescribed in the Wireless Telegraphy
Act.
[0031] Also, the need for an electrical or mechanical switch for a change to a transmission
output measuring terminal, required to measure the transmission output in the conventional
art, is eliminated to reduce the total manufacturing cost.
Figs. 1(A) through 1(C) are a perspective view, a front view and a side view, respectively,
of an antenna device in accordance with a first embodiment of the present invention
seen through a case;
Fig. 2 is a perspective view of a current supply element in the antenna device of
the first embodiment;
Fig. 3 is a block diagram showing connections in the antenna device of the first embodiment;
Figs. 4(A) through 4(C) are a perspective view, a front view and a side view, respectively,
of an antenna device in accordance with a second embodiment of the present invention
seen through a case;
Fig. 5 is a perspective view of a current supply element in the antenna device of
the second embodiment;
Fig. 6 is a block diagram showing connections in the antenna device of the second
embodiment;
Fig. 7 is a perspective view of a surface mount type antenna proposed in the specification
of Japanese Patent Application No. 6-81652;
Fig. 8 is a perspective view of a surface mount type antenna proposed in the specification
of Japanese Patent Application No. 6-81652 incorporating an antenna switch circuit;
Fig. 9 is a cross-sectional view of Fig. 8;
Fig. 10 is a circuit diagram of an antenna switch circuit;
Fig. 11 is a block diagram of the antenna shown in Fig. 8; and
Fig. 12 is a perspective view of a dielectric-loaded monopole antenna proposed in
the specification of Japanese Patent Application No. 6-034759.
[0032] Preferred embodiments of the present invention will be described below with reference
to the accompanying drawings.
[0033] Figs. 1 and 2 show an antenna device 51a and a current supply element 52 in accordance
with a first embodiment of the present invention. The antenna device 51a is incorporated
in a portable telephone 61. Figs. 1(A), 1(B), and 1(C) are a perspective view, a front
view and a side view, respectively, of the antenna device seen through a case, and
Fig. 2 is a perspective view of the current supply element 52.
[0034] Referring to Figs. 1 and 2, the antenna device 51a has the current supply element
52 and a radiating element 56a, and is mounted on a main circuit board 53a with the
current supply element 52 placed on a major surface of the main circuit board 53a.
The current supply element 52 is connected to a first micro-strip line 66, which is
a first transmission line formed on the main circuit board 53a to supply an antenna
current. The radiating element 56a is accommodated in a vacant space formed between
the main circuit board 53a and an outer case 55 in which the main circuit board 53a
is accommodated. The current supply element 52 is grounded to a grounding electrode
67a formed on the main circuit board 53a and insulated from the first micro-strip
line 66 while the radiating element 56a is grounded to the outer case 55. One major
surface of the radiating element 56a is opposed to and maintained in contact with
the current supply element 52.
[0035] To protect the main circuit board 53a, shield covers 54a and 54b are attached to
the two surfaces of the main circuit board 53a over the entire areas thereof excepting
the area where the current supply element 52 is placed.
[0036] The current supply element 52 is formed of a metallic chassis 54 made of, for example,
copper or a copper alloy and has, as viewed in a cross section, the shape of a rectangle
open at one side. The metallic chassis 54 has a rectangular flat opposed portion 52a
opposed to the major surface of the radiating element 56a in parallel with the same,
and two leg portions 52b and 52c bent downwardly and perpendicularly from shorter-side
opposite ends of the opposed portion 52a. A current supply terminal 52d is formed
integrally on the extreme end of the leg portion 52b while a grounding terminal 52e
is formed integrally on the extreme end of the leg portion 52c.
[0037] A grounding electrode 67b is formed generally over the entire reverse surface of
the main circuit board 53a. The first micro-strip line 66 is connected to, for example,
an antenna switch circuit (not shown).
[0038] To mount the metallic chassis 54 in a surface mount manner, the metallic chassis
54 is placed on the obverse surface of the main circuit board 53a, the current supply
terminal 52d and the first micro-strip line 66 are soldered to each other, and the
grounding terminal 52e and the grounding electrode 67a are soldered to each other.
[0039] A multilayer chip capacitor 68 is also mounted in a surface mount manner by being
placed on the obverse surface of the main circuit board 53a, with external electrodes
68a and 68b of the multilayer chip capacitor 68 soldered respectively to the first
micro-strip line 66 and a second micro-stripline 66c which server as a transmission
output measuring terminal. Thus, the transmission output measuring terminal (not shown)
of the antenna switch circuit is connected to the current supply terminal 52d and
to the first micro-strip line 66 through the multilayer chip capacitor 68. The current
supply element 52 is thus constructed.
[0040] In this embodiment, the current supply element 52 and the radiating element 56a are
maintained in contact with each other. Alternatively, the current supply element 52
and the radiating element 56a may be separated with a spacing such as to be electromagnetically
connected to each other.
[0041] The shape of the current supply element 52 is not limited to that shown in Fig. 2,
and the current supply element 52 may have any other shape as long as at least one
current supply terminal 52d and at least one grounding terminal 52e are provided and
a transmitted electric wave output can be supplied to the radiating element 56a electrically
or electromagnetically. For example, the current supply element 52 may be formed of
a metallic block. The positional relationship between the current supply terminal
52d and the grounding terminal 52e is not limited to that shown in Fig. 2. For example,
the current supply terminal 52d and the grounding terminal 52e may be respectively
formed on the longer sides of the current supply element 52.
[0042] In this embodiment, a micro-strip line is used as a transmission line. However, a
coplanar line may alternatively be used.
[0043] Fig. 3 is a block diagram showing connections of the antenna device 51a. As shown
in Fig. 3, the current supply element 52 and the radiating element 56a in contact
with each other are electrically connected, and a transmitted electric wave output
from the current supply element 52 is radiated through the radiating element 56a.
The above-mentioned transmission output measuring terminal 66c connected to the current
supply element 52 via the capacitor 68. C1 represents a stray capacity of the radiating
element 56a.
[0044] The thus-constructed antenna device 51a is mounted by attaching the current supply
element 52 to the main circuit board 53a and accommodating the radiating element 56a
in the gap formed between the main circuit board 53a and the outer case 55. Therefore,
the radiating element 56a can easily be separated from the current supply element
52 by removing the outer case 55 from the main circuit board 53a, even after the current
supply element 52 has been mounted on the main circuit board 53a.
[0045] The above-mentioned transmission output measuring terminal 66c is connected to the
current supply element 52 through the multilayer chip capacitor 68, and the capacitance
of the multilayer chip capacitor 68 is therefore added to the transmission output
from the current supply element 52 at the transmission output measuring terminal.
That is, the capacitance of the multilayer chip capacitor 68 connected to the current
supply element 52 can be used to cancel the influence of an inductance of the current
supply element 52 upon the measured value of the transmission output from the current
supply element 52 at the transmission output measuring terminal. It is therefore possible
to accurately measure the transmission output of the antenna switch circuit by canceling
the influence of the inductance of the current supply element 52.
[0046] By using the above-described means and by removing the radiating element 56a, the
transmission output of the antenna switch circuit when the antenna device 51a is removed,
regulated by the Wireless Telegraphy Act, can be measured easily and accurately even
after the current supply element 52 has been mounted on the main circuit board 53a.
Therefore, transmission output level checking at the time of forwarding can be performed
easily.
[0047] Also, there is no need for an electrical or mechanical switch for a change to a transmission
output measuring terminal, required to measure the transmission output. The manufacturing
cost of the portable telephone can therefore be reduced.
[0048] Figs. 4 and 5 show an antenna device 51b and a current supply element 52z in accordance
with a second embodiment of the present invention. The components identical or corresponding
to those shown in Figs. 1 and 2 are indicated by the same reference characters and
the description for them will not be repeated. The antenna device 51b is incorporated
in a portable telephone 61. Figs. 4(A), 4(B), and 4(C) are a perspective view, a front
view and a side view, respectively, of the antenna device 51b seen through a case.
Fig. 5 is a perspective view of the current supply element 52z.
[0049] Referring to Figs. 4 and 5, the current supply element 52z of the antenna device
51b is placed on a major surface of a main circuit board 53a to be connected to a
first micro-strip line 66a, which is first transmission line for supplying an antenna
current, and to a second micro-strip line 66b, which is a second transmission line
for measuring a transmission output. The current supply element 52z is also connected
to a grounding electrode 67a. One major surface of a radiating element 56a is opposed
to the current supply element 52z and maintained in contact with the same.
[0050] The first and second micro-strip lines 66a and 66b are formed on the main circuit
board 53a. The second micro-strip line 66b is insulated from the first micro-strip
line 66a and the grounding electrode 67a, and serves as the transmission output measuring
terminal (not shown).
[0051] A member 81 is a dielectric substrate in the form of a rectangular prism made of,
for example, a ceramic or a resin. A transmission output measuring electrode 82 is
formed on one of longer-side side surfaces of the dielectric substrate 81 while connection
electrodes 83a and 83b are formed on shorter-side side surfaces of the dielectric
substrate 81. A first capacitor electrode 85a connected to the connection electrode
83a and a second capacitor electrode 85b connected to the transmission output measuring
electrode 82 are provided in the dielectric substrate 81, thereby forming an incorporated
capacitor 85.
[0052] A member 84 is a metallic chassis made of, for example, copper or a copper alloy
and having, as viewed in a cross section, the shape of a rectangle open at one side.
The metallic chassis 84 has a current supply terminal 52d and a grounding terminal
52e formed through a length corresponding to the thickness of the dielectric substrate
81. The lengths of leg portions 52b and 52c, including the lengths of the current
supply terminal 52d and the grounding terminal 52e, respectively, are set so as to
be larger than the thickness of the dielectric substrate 81.
[0053] The dielectric substrate 81 is inserted into the metallic chassis 84. At this time,
shorter-side side surfaces of the dielectric substrate 81 are brought into contact
with inner surfaces of the current supply terminal 52d and the grounding terminal
52e of the metallic chassis 84, and a space 90 is formed between an opposed portion
52a of the metallic chassis 84 and the obverse surface of the dielectric substrate
81 due to the difference between the thickness of the dielectric substrate 81 and
the lengths of the leg portions 52b and 52c including the current supply terminal
52d and the grounding terminal 52e. The connection electrode 83a of the dielectric
substrate 81 and the current supply terminal 52d of the metallic chassis 84 are soldered
to each other while the connection electrode 83b of the dielectric substrate 81 and
the grounding terminal 52e of the metallic chassis 84 are soldered to each other.
[0054] The metallic chassis 84 in which the dielectric substrate 81 is inserted is mounted
on the main circuit board 53a in a surface mount manner by being placed on the obverse
surface of the main circuit board 53a, with the current supply terminal 52d, the grounding
terminal 52e and the transmission output measuring electrode 82 soldered to the first
micro-strip line 66a, the grounding electrode 67a and the second micro-strip line
66b, respectively. The current supply element 52z is thus constructed.
[0055] Fig. 6 is a block diagram showing connections of the antenna device 51b. Components
identical or corresponding to those shown in Fig. 3 are indicated by the same reference
characters and the description for them will not be repeated. Referring to Fig. 6,
the current supply element 52z and the radiating element 56a in contact with each
other are electrically connected to each other, and a transmitted electric wave output
from the current supply element 52z is radiated through the radiating element 56a.
The above-mentioned transmitting output measuring terminal 66c is connected to the
current supply element 52z via the capacitor 85.
[0056] The thus-constructed current supply element 52z is mounted on the main circuit board
53a while the radiating element 56a is accommodated in the gap formed between the
main circuit board 53a and the outer case 55 in which the main circuit board 53a is
accommodated. Also, the transmission output measuring terminal is connected to the
current supply element 52z through the incorporated capacitor 85 provided in place
of the multilayer chip capacitor 68 in the current supply element 52 of the first
embodiment. Therefore, the same effect as that of the first embodiment can be obtained.
[0057] In the current supply element 52z, the dielectric substrate 81 is inserted in the
metallic chassis 84, so that the current supply element 52z has a large capacitance.
The resonance frequency of the antenna device 51b can be reduced thereby. The space
90 is provided between the opposed portion 52a of the metallic chassis 84 and the
obverse surface of the dielectric substrate 81, so that an eddy current in the grounding
surface, caused by a magnetic field generated around a high-frequency current flowing
through the opposed portion 52a, is limited, and so that the electric field caused
by the magnetic field cannot concentrate easily in the dielectric substrate 81. Therefore,
the efficiency at which the transmission output is transmitted to the radiating element
56a is further improved and the gain of the antenna device 51b is further increased.
Further, the impedance of the current supply element 52z can be adjusted at the time
of designing by setting the incorporated capacitor 85 in the dielectric substrate
81. Therefore, there is no need to select and adjust the capacitance of a capacitor
connected to the current supply element 52z when the current supply element 52z is
mounted on the main circuit board 53a. Also, it is possible to reduce the area on
the main circuit board 53a in which the current supply element 52z is mounted.
[0058] As described above, the antenna device of the present invention is mounted by placing
the current supply element on the main circuit board and by accommodating the radiating
element in the gap formed between the main circuit board and the outer case in which
the main circuit board is accommodated. Therefore, it is possible to easily separate
the radiating element from the current supply element by removing the outer case from
the main circuit board, even after the current supply element has been mounted on
the main circuit board.
[0059] Since the transmission output measuring terminal is connected to the current supply
element through the multilayer chip capacitor or the incorporated capacitor, the capacitance
of the capacitor is added to the transmission output from the current supply element
at the transmission output measuring terminal. The influence of the inductance of
the current supply element upon the measured value of the transmission output from
the current supply element at the transmission output terminal can be canceled by
the capacitance of the multilayer chip capacitor or incorporated capacitor connected
to the current supply element. Consequently, the transmission output of the antenna
circuit can be measured accurately by removing the influence of the inductance of
the current supply element.
[0060] According to the above-described arrangement, even after the current supply element
has been mounted on the main circuit board, the radiating element can be removed to
accurately measure the transmission output of the antenna circuit as the transmission
output measured when the antenna device is removed as prescribed in the Wireless Telegraphy
Act. Therefore, transmission output level checking at the time of forwarding can be
performed easily.
[0061] The need for an electrical or mechanical switch for a change to a transmission output
measuring terminal, required to measure the transmission output, is eliminated to
reduce the total manufacturing cost.
[0062] The dielectric substrate is inserted into the metallic chassis in the current supply
element to increase the capacitance of the current supply element. The resonance frequency
of the antenna device can be reduced thereby. A space is provided between the opposed
portion of the metallic chassis and the dielectric substrate, so that an eddy current
in the grounding surface, caused by a magnetic field generated around a high-frequency
current flowing through the opposed portion, is limited, and so that the electric
field caused by the magnetic field cannot concentrate easily in the dielectric substrate.
Therefore, the efficiency of transmission of the transmission output to the radiating
element is further improved and the gain of the antenna device is further increased.
Further, the impedance of the current supply element can be adjusted at the time of
designing by setting an incorporated capacitor in the dielectric substrate. Therefore,
there is no need to select and adjust the capacitance of a capacitor connected to
the current supply element when the current supply element is mounted on the main
circuit board. Further, it is possible to reduce the area on the main circuit board
in which the current supply element is mounted.