Communications: radio wave antennas – Antennas – With radio cabinet
Reexamination Certificate
1999-12-22
2001-03-13
Ho, Tan (Department: 2821)
Communications: radio wave antennas
Antennas
With radio cabinet
C343S803000, C343S895000
Reexamination Certificate
active
06201503
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an antenna for radio device projecting outwardly from the case of a mobile telephone or the like, and a radio device using the antenna.
2. Description of the Related Art
In order to receive call-up signals, a mobile telephone and the like needs an antenna device which operates as an antenna at all times. On the other hand, it is not desirable for a long antenna to be projecting from the case at all times, since it renders the telephone less easily portable. Accordingly, various types of antenna devices have been proposed in which call-up signals are received by an antenna element having a relatively short physical length and projecting outwardly from the case at all times, a longer rod-like antenna element being extracted during communication to achieve high-gain reception and transmission. The present applicants have already disclosed an example of such an antenna device in Japan Patent Application 1996-266656.
The technology proposed in Japan Patent Application 1996-266656 will be explained simply with reference to FIG.
14
and FIG.
15
.
FIG. 14
is a circuit diagram showing the antenna for radio device described above in an extracted state.
FIG. 15
is a vertical cross-sectional view of the extracted antenna for radio device shown in FIG.
14
.
In
FIG. 15
, a mounting metal part
12
comprises a conductive metal and is securely screwed to a case
10
of a radio device. A through hole
12
a
is provided in the mounting metal part
12
. In addition, a substantially cylindrical core
14
of insulating resin is provided coaxially to the mounting metal part
12
and extends outwardly therefrom. A first antenna element
16
is wrapped around the outer face of the core
14
so as to be substantially cylindrical. Furthermore, a cover
18
comprising insulating resin covers the first antenna element
16
, and the bottom end of the cover
18
is secured to the mounting metal part
12
. A hole
18
a
is coaxially provided in the cover
18
, and a ring groove for clipping
18
b
is provided in the inner wall of the hole
18
a.
The through hole
12
a
of the mounting metal part
12
, the substantially cylindrical core
14
, and the hole
18
a
of the cover
18
are provided around a single axis. Furthermore, a rod-like second antenna element
22
has a rod-like insulating member
20
on its tip, and is provided so as to be capable of moving freely in the same axial direction as the above. The outer face and base and the like of the second antenna element
22
are all covered by an insulating tube or the like. Furthermore, an axis-encircling groove for clipping
20
a
is provided in the tip of the rod-like insulating member
20
, and a button
20
b
for restricting the movement of the second antenna element
22
in the storage direction is provided on the tip thereof. Furthermore, an axis-encircling groove for clipping
22
a
is provided in the insulator covering the base portion of the second antenna element
22
. A step
22
b
is provided at the bottom of the second antenna element
22
to restrict its movement in the extraction direction. Furthermore, a ring for clipping
24
comprises a ring-shaped insulating resin having a cutaway portion, and is inserted into the ring groove for clipping
18
b
in the cover
18
. When the antenna is stored, the ring for clipping
24
meshes with the groove for clipping
20
a
of the rod-like insulating member
20
, thereby holding the antenna in the stored state. When the antenna is extracted, the ring for clipping
24
meshes with the groove for clipping
22
a
in the second antenna element
22
, thereby holding the antenna in the extracted state.
As shown in
FIG. 14
, the first antenna element
16
comprises a zigzag portion
16
a
extending in the axial direction, and a folded portion
16
b
extending in the peripheral direction. The first antenna element
16
is wound cylindrically around the core
14
, and the base of the folded portion
16
a
is conductively connected to the mounting metal part
12
by soldering.
A feeding metal part
26
comprises a conductive metal, and engages with the mounting metal part
12
screwed to the case
10
. Further, the feeding metal part
26
is conductively connected via a cable
28
to an antenna input/output terminal
29
of a radio circuit
29
.
According to the above constitution, when the antenna is extracted as shown in
FIG. 14
, the axial direction tip of the first antenna element
16
is connected at high frequency to the base of the second antenna element
22
by the coupling of a floating capacitance Ci, whereby the first and second antenna elements
16
and
22
function as a single antenna. Furthermore, when the antenna is stored (the diagram does not show this state), the second antenna element
22
is inside the case
10
and consequently is not connected at high frequency to the first antenna element
16
, whereby only the first antenna element
16
functions as an antenna.
Accordingly, the antenna can be stored when the mobile telephone or the like is being carried, and is able to receive call-up signals using only the first antenna element
16
. On the other hand, during communication, the second antenna element
22
is extracted, whereby the first and second antenna elements
16
and
22
enable the antenna to receive and transmit with high gain.
The previously proposed antenna for radio device described above is conveniently portable, and has high antenna gain during communication. However, when the second antenna element
22
is extracted, its base is coupled to the axial direction tip of the first antenna element
16
by the floating capacitance Ci, and this floating capacitance Ci is not always constant. During manufacturing, adjustment of the band of resonant frequencies at which the first and second antenna elements
16
and
22
function as a single antenna is complex.
Furthermore, when the second antenna element
22
is extracted, its base is capacitance-coupled to multiple axial direction tip portions of the folded portion
16
b
which extends in the peripheral direction of the first antenna element
16
. Multiple closed loops are formed by the floating capacitances between these axial direction tip portions, and the partial impedance of the folded portion
16
b
. These multiple closed loops have a detrimental effect of lowering the antenna gain. There is a further problem, in that the resonant frequencies of the closed loops are not constant.
SUMMARY OF THE INVENTION
The present invention has been devised in order to solve the problems of the previously proposed antenna for radio device, and aims to provide an antenna for radio device and a radio device using the antenna wherein, when the base of the extracted second antenna element is conductively connected to the axial direction tip of the first antenna element, antenna characteristics are stable and antenna gain is high.
In order to achieve the above objects, the antenna for radio device of the present invention comprises a mounting metal part having a through hole therein and being attached to a case of a radio device; a first antenna element provided to this mounting metal part cylindrically around the same axis as the through hole and projecting to the outside of the case; conductive tongues projecting from a plurality of places on the first antenna element; a rod-like second antenna element having a rod-like insulating member at its tip portion, capable of moving freely in the axial direction of the through hole and the cylindrical first antenna element; the plurality of conductive tongues conductively connecting to a base portion of the second antenna element, and to each other, when the second antenna element is extracted, and the plurality of conductive tongues clasping either side of the rod-like insulating member and connecting nonconductively to each other when the second antenna element is stored.
In an alternative arrangement of the present invention, the first antenna element may comprise a zigzag portion or a folded port
Dickstein , Shapiro, Morin & Oshinsky, LLP
Ho Tan
Kabushiki Kaisha Yokowo
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