Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
2002-04-02
2004-03-02
Le, Hoanganh (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S702000, C343S873000
Reexamination Certificate
active
06700541
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an antenna element for use in reception or transmission of radio waves, and more particularly, to an antenna element which has conductors formed on its outer surfaces of a device substrate.
2. Description of the Related Art
At present, radio communication apparatuses called a mobile telephone and the like are pervasive in general users, and a reduction in size and weight is required for the radio communication apparatuses. The radio communication apparatus receives and transmits radio waves through an antenna element, where the total length of a conductive path is closely related to the wavelength of a radio wave transmitted or received thereby.
For this reason, since a simple reduction in the length of the conductive path causes a rise in the resonant frequency, difficulties are encountered in efficiently radio communicating a radio wave at a predetermined frequency. To address this problem, a variety of techniques have been devised for reducing the shape of an overall antenna element while maintaining a required resonant frequency.
For example, an antenna element called a helical antenna has a conductive path formed in a spiral shape, while an antenna element called a meander antenna has a conductive path in a meandering shape. While these antennas do not achieve a reduction in the total length of the conductive path, the overall shape can be substantially reduced.
There is also an antenna element called a dielectric antenna which has a conductive path formed on the surface of a dielectric material to reduce the length of the conductive path. Since the wavelength of a radio wave is reduced within a member having a high dielectric constant or permeability, the formation of the conductive path on or within a dielectric material or a magnetic material results in a reduction in the total length thereof.
Moreover, there is an antenna element called a loaded antenna which adds a reactance element, an inductance element or a capacitance element to a conductive path to reduce the length of the conductive path. It should be understood that a variety of foregoing techniques may be combined, for example, to create an antenna element which has a conductive path formed in a helical shape or in a meander shape on the surface of a dielectric material.
An antenna element can be made compact by a variety of techniques as described above. However, in the helical antenna and meander antenna, a long conductive path is bent to reduce the area occupied thereby, so that adjacent portions of the conductive path are electromagnetically coupled to cause an increase in surface current and high frequency loss.
To solve the problem as mentioned, the present inventor invented an antenna element which has a conductive path formed in a shape different from the helical shape or meander shape on the surface of a dielectric material, and filed the invention as Japanese Patent Application No. 2001-026002. This application discloses an antenna element which has a first conductor and a second conductor, parallel to each other, connected by a short-circuit conductor to form a loaded inductance.
Referring now to
FIG. 1
, the antenna element disclosed in the application will be described below in brief, as a related art which precedes the present invention and is not known. The antenna element described below was filed in Japan on Feb. 1, 2001 as Japanese Patent Application No. 2001-026002, and filed in the United States of America on Jan. 31, 2002 as U.S. Ser. No. 10/059423 by the present inventor. However, this application has not been opened in any country, so that this is not a prior art but merely a related art of the present invention.
Antenna element
100
in the aforementioned application has device substrate
101
made of a dielectric material in rectangular solid, and conductive path
102
formed of a printed wire on the front surface of device substrate
101
to implement a dielectric antenna as described above. Conductive path
102
is comprised of power supply conductor
103
, first conductor
104
, short-circuit conductor
105
, and second conductor
106
.
More specifically, power supply conductor
103
of conductive path
102
comprises a linear portion formed from the bottom surface to front surface of device substrate
101
, while first conductor
104
comprises a linear portion formed from an upper end or terminate end of power supply conductor
103
and bent at a right angle to the right in the figure.
Short-circuit conductor
105
comprises a linear portion formed from a right end or terminate end of first conductor
104
and bent upward at a right angle in the figure, i.e., in the opposite direction to power supply conductor
103
, while second conductor
106
comprises a linear portion formed from an upper end or terminate end of short-circuit conductor
105
and bent at a right angle to the left in the figure, and positioned in parallel with first conductor
104
.
In antenna element
100
of the structure as described, conductive path
102
can be reduced in length since first conductor
104
and second conductor
106
, positioned in parallel with each other, act as a loaded inductance. In addition, since conductive path
102
is generally bent in a U-shape (which has three straight lines forming two right angles), the overall shape can be made compact.
Unlike the meander antenna, helical antenna and the like, in spite of the reduction in size, first conductor
104
and second conductor
106
, positioned in parallel with each other, are sufficiently spaced away from each other, so that their electromagnetic coupling is reduced, thereby making it possible to realize radio communications with high gain, high efficiency and wide band.
Antenna element
100
of the structure described above presents a rise in the resonant frequency as the overall shape is simply reduced in shape, whereas the resonant frequency is reduced as the loaded inductance is increased. In other words, when the resonant frequency is maintained constant, an increase in the loaded inductance can result in a relative reduction in the size of the overall shape.
The loaded inductance of conductive path
102
in the aforementioned antenna element
100
may be increased by spacing first conductor
104
and second conductor
106
away from each other, reducing the width of conductive path
102
, extending the length of conductive path
102
such as first/second conductors
104
,
106
, and the like.
However, for spacing first conductor
104
and second conductor
106
away from each other, device substrate
101
must be extended, resulting in an increased size of the overall shape. The width of conductive path
102
has a lower limit determined by a thermal condition, and a reduction in the width of the conductive path
102
will cause a reduced bandwidth and an increased high frequency loss, so that the width of conductive path
102
cannot be reduced without prudence.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a antenna element which is made compact, and has a first conductor and a second conductor positioned in parallel with each other and connected through a short-circuit conductor.
The antenna element according to the present invention has a first conductor, a short-circuit conductor, a second conductor, and a device substrate. The device substrate is made of at least one of a dielectric material and a magnetic material, and is formed with the first conductor, short-circuit conductor and second conductor on its outer surface. The first conductor is made of a linear conductor supplied with electric power at a leading end thereof, while the short-circuit conductor is connected perpendicularly to a terminate end of the first conductor. The second conductor is connected at a right angle to a terminate end of the short-circuit conductor and positioned in parallel with the first conductor.
In a first aspect of the antenna element described above, an extended portion bent in a U-shape is formed in at least one of
Le Hoang-anh
NEC Microwave Tube, Ltd.
Young & Thompson
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