Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
2002-04-25
2004-03-02
Wong, Dong (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S702000, C343S848000
Reexamination Certificate
active
06700543
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 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 line 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 line 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 line formed in a spiral shape, while an antenna element called a meander antenna has a conductive line in a meandering shape. While these antennas do not achieve a reduction in the total length of the conductive line, the overall shape can be substantially reduced.
There is also an antenna element called a dielectric antenna which has a conductive line formed on the surface of a dielectric material to reduce the length of the conductive line. Since the wavelength of a radio wave is reduced within a member having a high dielectric constant or permeability, the formation of the conductive line 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 line to reduce the length of the conductive line. It should be understood that a variety of foregoing techniques may be combined to create, for example, an antenna element which has a conductive line formed in a helical shape or in a meander shape on the surface of a dielectric material.
In another technique, a ground electrode is connected to a conductive line of an antenna element by a short pin to generate a current through the short pin in opposite phase to that in the conductive line in an opposite direction. Since the opposite phase current generated in the opposite direction in this manner can be regarded as an in-phase current generated in the same direction, a radiation resistance of the antenna element can be increased as a result.
A variety of techniques as described above permit an improvement in the performance of antenna elements without uselessly increasing the size thereof. However, in the helical antenna and meander antenna, a long conductive line is bent to reduce the area occupied thereby, so that adjacent portions of the conductive line 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 line 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
FIGS. 1 and 2
, the antenna element disclosed in the above-cited 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, and conductive line
102
formed of a printed wire on a front surface and a bottom surface of device substrate
101
. Conductive line
102
is comprised of power supply conductor
103
, first conductor
104
, short-circuit conductor
105
, and second conductor
106
, each of which is linearly formed in succession.
More specifically, power supply conductor
103
of conductive line
102
comprises a linear portion formed from the bottom surface to the front surface of device substrate
101
, while first conductor
104
comprises a linear portion formed from an upper end which is a 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 which is a 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 which is a terminate end of short-circuit conductor
105
and bent at a right angle to the left in the figure, and positioned in parallel to first conductor
104
.
Then, antenna apparatus
200
using antenna element
100
as described above comprises a circuit board
201
made of glass epoxy resin, ethylene tetrafluoride or the like, as illustrated in
FIG. 2. A
copper foil is adhered in a lower half and the like of a front surface of circuit board
201
to form a ground electrode
202
.
Ground electrode
202
is partially formed with a recess in which power supply electrode
204
is formed for power supply circuit
203
(for example, a coaxial cable) which serves as a power supply means. Then, antenna element
100
is mounted on an upper half of the front surface of circuit board
201
on which ground electrode
202
is not formed. Power supply conductor
103
is connected to power supply electrode
204
.
In antenna element
100
of the structure as described above, conductive line
102
can be reduced in length since first conductor
104
and second conductor
106
, positioned in parallel to each other, act as a loaded inductance. In addition, since conductive line
102
is generally bent in an inverted C-shape, the overall shape can be reduced in size.
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 to 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 a high gain, high efficiency and wide band.
In antenna element
100
, since short-circuit conductor
105
mainly transmits and receives radio waves, the transmission/reception have a directivity in the horizontal direction in the figure orthogonal to the longitudinal direction of the short-circuit conductor
105
. For this reason, if a conductor such as ground electrode
202
is positioned in a direction orthogonal to short-circuit conductor
105
, the conductor will impede the transmission/reception of radio waves through short-circuit conductor
105
.
To solve the foregoing problem, it is contemplated to avoid forming ground electrode
202
and the like in the direction orthogonal to short-circuit conductor
105
. However, this solution would cause a reduction in the area of ground electrode
202
available for mounting circuit parts (not shown). In other words, it is necessary to minimize an antenna mounting area on which ground electrode
202
is not formed in order to maximize an area available for mounting circuit parts.
SUMMARY OF THE INVENTION
It is an object
Ikeda Masashi
Konishi Takayoshi
Minegishi Kazuo
Chen Shih-Chao
NEC Tokin Corporation
Wong Dong
Young & Thompson
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