Communications: radio wave antennas – Antennas – Spiral or helical type
Reexamination Certificate
1999-06-09
2001-09-04
Ho, Tan (Department: 2821)
Communications: radio wave antennas
Antennas
Spiral or helical type
C343S702000, C343S901000
Reexamination Certificate
active
06285340
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an antenna, and more particularly, to an antenna for use in a portable telephone such as a cellular phone and a manufacturing method thereof.
2. Description of the Related Art
Portable phones are getting smaller in size due to the developments in battery technology and the integration of internal circuits thereof into chips. In addition, antennas employed in the portable phones are getting smaller along with the main body of the phones. Although the antenna of the portable phone is getting smaller, it is necessary that it still exhibit enough sensitivity to operate properly. In order to minimize its size while maintaining the sensitivity thereof, the antenna assembly for the portable phone typically employs a helical antenna incorporated with a whip antenna.
FIGS. 1 and 2
illustrate an example of a conventional antenna assembly which employs a helical antenna and a whip antenna, in an extended position and a retracted position, respectively. In the antenna assembly of
FIGS. 1 and 2
, the helical antenna includes a helical element
10
, a first metal fitting
12
, a second metal fitting
14
, and a first antenna cover
16
. The helical element
10
is usually made of an elastic metal and has an electrical length of &lgr;/4. The first metal fitting
12
has an aperture passing through its center vertically and is threaded on its outer surface. The second metal fitting
14
provides an electrical connection between the helical element
10
and the first metal fitting
12
. The first antenna cover
16
encloses the helical element
10
to prevent the performance of the helical element
10
from being deteriorated due to deformation, damage, or oxidation thereof caused by external contact or impact. Meanwhile, the whip antenna includes an antenna rod
20
, a second cover
22
, and a conductive stopper
24
. The antenna rod
20
has an electrical length of &lgr;4 and operates as a monopole antenna. The second cover
22
, which is made of a nonconductive plastic material, encloses the antenna rod
20
to protect it from external contact. The stopper
24
is attached to the bottom end of the antenna rod
20
. In
FIGS. 1 and 2
, reference numeral
36
denotes a housing body of a portable phone.
In such an antenna assembly, the whip antenna is installed capable of upward and downward movement. When a user extends the whip antenna by pulling a knob
26
installed at the upper end thereof as show in
FIG. 1
, the power from a signal processing circuit
30
inside the phone is provided to the antenna rod
20
via an antenna clip
32
, a housing fitting
34
, and the stopper
24
, and simultaneously to the helical element
10
via the first metal fitting
12
and the second metal fitting
14
. In this operation mode, the whip antenna mainly operates as a monopole antenna, and the helical antenna operates as an accessory of the whip antenna. Meanwhile, when the antenna is retracted into the housing body as shown in
FIG. 2
, power from the signal processing circuit
30
is provided only to the helical element
10
since the stopper
24
is separated from the housing fitting
34
and the second metal fitting
12
. Therefore, only the helical antenna receives or transmits signals.
Typically, the helical element of the antenna assembly described above is manufactured by winding an elastic metal wire over a dielectric such as polyvinyl chloride (PVC). However, this method of manufacture is quite costly because the elastic metal for the helical element is expensive as compared with a common material such as copper. Meanwhile, a metal wire used for the helical element is required to be highly oxidation-resistant so that the helical element is resistant from oxidization inside the antenna cover. To solve the oxidation problem, the outer surface of the metal wire may be coated with a plastic or a polymer. However, an accurate coating of the outer surface of the metal wire requires several additional processing steps. These additional processing steps significantly decrease the efficiency of mass-production of the antenna. Furthermore, the conventional helical antenna may be deformed or lose a required antenna characteristics when it experiences a strong impact even though it is protected by the antenna cover.
SUMMARY OF THE INVENTION
To solve the above problems, one object of the present invention is to provide a helical antenna with a structure simple enough to increase the efficiency of mass-production thereof. Another object of the present invention is to provide a conductor made of a cheap conducting material in order to reduce the manufacturing cost, and to significantly reduce the size of the antenna while maintaining the performance thereof.
Another object of the present invention is to provide a method of manufacturing a helical antenna having characteristics described above, which is appropriate for mass-production of the antenna.
According to an aspect of the present invention to achieve one of the above objects, a helical antenna comprises a dielectric core, a conductive strip, a feeding conductor, and an external circuit. The dielectric core has a substantially cylindrical shape with an outer circumferential surface on which a spiral groove is formed. The conductive strip is deposited on the spiral groove of the dielectric core. The feeding conductor is placed under the dielectric core and provides an electrical connection between the conductive strip and an external circuit. The antenna cover encloses the dielectric core and the feeding conductor.
According to another aspect of the present invention to achieve one of the above objects, a dual band helical antenna operable at two different frequencies comprises a first and second dielectric cores, a first and a second conductive strips, a feeding conductor, and an antenna cover. The first dielectric core has a substantially cylindrical shape with an outer circumferential surface on which a first spiral groove is formed. The first conductive strip is deposited on the first spiral groove and has a length of one-fourth of a first wavelength. The second dielectric core is positioned under the first dielectric core and has a substantially cylindrical shape with an outer circumferential surface on which a second spiral groove is formed. The second conductive strip is deposited on the second spiral groove of the second dielectric core and electrically connected to the first conductive strip, and has a length of one-fourth of a second wavelength. The feeding conductor is placed under the second dielectric core to provide an electrical connection between the second conductive strip and an external circuit. The antenna cover encloses the first and the second dielectric cores and the feeding conductor.
In a method of manufacturing a helical antenna to achieve another one of the above objects, a dielectric core having a substantially circular shape is provided, and a spiral groove is formed on an outer circumferential surface of the dielectric core. A conductive strip is deposited along the spiral groove of the dielectric core. A feeding conductor is provided so as to be electrically connected to the conductive strip at one end of the dielectric core. Finally, an antenna cover is enclosed cover over the dielectric core and the feeding conductor.
The helical antenna according to the present invention has a simple structure that can be easily reproduced. This simple structure is suitable for mass-production, thus the manufacturing cost thereof can be reduced. Additionally, the simple structure consistent with the present invention allows for the use of copper as a conductor in a helical antenna. Copper is cheaper than conventional materials used as a conductor in the helical element, thus the manufacturing cost can be reduced further. Also, the stability of the antenna is improved since the helical antenna is implemented by a conductive strip formed onto a dielectric which rarely is affected by an external touch or impact to be deformed or oxidized. Furthermore,
Koo Ki Duk
Lee Kyu Bok
Park Duck Jae
Sung Jae Suk
Yun Jong Cheol
Ace Technology
Chen Shih-Chao
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Ho Tan
LandOfFree
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