Communications: radio wave antennas – Antennas – Spiral or helical type
Reexamination Certificate
2001-08-28
2002-12-17
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
Spiral or helical type
C343S702000
Reexamination Certificate
active
06496159
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a digital radio receiver for receiving a radio wave from an artificial satellite (which may be called a “satellite wave”) or a radio wave from a ground station (which may be called a “ground wave”) to listen to digital radio broadcasting and, in particular, to an antenna for use in the digital radio receiver as well as a method of producing the antenna.
In recent years, a digital radio receiver for receiving a satellite wave from an artificial satellite or a ground wave from a ground station to listen to digital radio broadcasting has been developed and is put into practical use in the United States of America. The digital radio receiver is mounted on a mobile station such as a vehicle and is adapted to receive a radio wave having a frequency of about 2.3 GHz to listen to the digital radio broadcasting. In other words, the digital radio receiver is a radio receiver capable of listening to mobile broadcasting. It is noted here that the ground wave is a radio wave obtained by slightly shifting the frequency of the satellite wave after it is received by the ground station.
In order to receive the radio wave having the frequency of about 2.3 GHz, it is necessary to mount an antenna at a position outside the vehicle. Such antenna may have various structures but a stick type is generally used rather than a planar type (flat type). As well known, an electromagnetic wave emitted into a free space is a transversal wave having an electric field and a magnetic field vibrating in a plane perpendicular to a propagating direction of the wave. The electric field and the magnetic field are variable in intensity within the above-mentioned plane. Such electromagnetic wave in which the direction of the electric field is not random but constant or varied in some regular way is referred to as a polarized wave. The satellite wave is a circular polarized wave exhibiting circular polarization while the ground wave is a linear polarized wave exhibiting linear polarization.
Hereinafter, description will mainly be made of an antenna for receiving the satellite wave. As one of stick-type antennas, a helical antenna is known. The helical antenna comprises a hollow or solid cylindrical member and a conductor wire wound around the cylindrical member in a helical fashion and can efficiently receive the above-mentioned circular polarized wave. Therefore, the helical antenna is exclusively or mainly used to receive the satellite wave.
An existing helical antenna is produced by preparing a cylindrical member or a pole, forming an antenna pattern on a flexible substrate to obtain a patterned film, and winding the patterned film on the cylindrical member or the pole.
However, the helical antenna comprising the patterned film wound around the cylindrical member or the pole is complicated in structure, resulting in a bar to reduction in cost.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to provide a helical antenna which is further simplified in structure and is reduced in cost.
It is another object of this invention to provide a method of producing the above-mentioned helical antenna.
Other objects of the present invention will become clear as the description proceeds.
According to the present invention, there is provided a helical antenna comprising a cylindrical member having a peripheral surface and a helical conductor attached to said peripheral surface and extending along said peripheral surface to make a helical fashion.
According to the present invention, there is provided a method of producing the helical antenna. The method comprises the steps of preparing the cylindrical member, forming a mask layer on the peripheral surface of the cylindrical member with a helical gap left in the mask layer, attaching metal particles onto the mask layer and onto the peripheral surface through the helical gap, and detaching the mask layer from the peripheral surface with the metal particles left as the helical conductor on the outer peripheral surface.
According to the present invention, there is provided a method of producing the helical antenna. The method comprises the steps of preparing the cylindrical member, forming a conductor layer on the peripheral surface of the cylindrical member, forming a mask layer on the conductor layer with a helical gap left in the mask layer, forming a metal plating layer on the conductor layer through the helical gap, and removing, with the metal particles left as the helical conductor on the outer peripheral surface, from the peripheral surface the mask layer and a masked part of the conductor layer which is covered with the mask layer.
REFERENCES:
patent: 6094179 (2000-07-01), Davidson
patent: 6285340 (2001-09-01), Park et al.
Clinger James
Frishauf Holtz Goodman & Chick P.C.
Mitsumi Electric Co. Ltd.
Wong Don
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