Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
2000-03-15
2001-04-24
Phan, Tho (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S787000, C343S873000, C343S895000
Reexamination Certificate
active
06222489
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to antenna devices and chip antennas. In particular, the present invention relates to an antenna device used for mobile communication, cellular communication, local area networks (LAN), television, radio, etc. Further, the present invention makes use of a chip antenna of small size, itself a monopole antenna, which, together with a ground part, functions like a dipole antenna, even though it is of small size.
2. Description of the Related Art
FIG. 3
shows a prior art monopole antenna
50
. The monopole antenna
50
has a conductor
51
, one end
52
of the conductor
51
being a feeding point and the other end
53
being a free end in the air (dielectric constant &egr;=1 and relative permeability &mgr;=1).
Because the conductor of the antenna is present in the air in linear antennas, such as the prior monopole antenna
50
, the size of the antenna conductor becomes larger. For example, when the wavelength in the vacuum is &lgr;
0
in the monopole antenna
50
, the length of the conductor
51
must be &lgr;
0/
4. Thus, such an antenna cannot be readily used for mobile communication or the like which requires a compact antenna.
Conventionally, as a small-sized antenna to be used in a radio equipment, an inverted F-type antenna is known. One example of an inverted F-type antenna is explained in reference to FIG.
11
. The inverted F-type antenna
50
is composed of a printed-circuit board
52
which is made of a glass-filled epoxy resin of a relative dielectric constant of 4 to 5 and on a surface of which a ground electrode
51
connected to the ground electric potential is provided, and a radiator plate
53
which is made of a metal plate arranged in parallel with the printed circuit board
52
and above the printed-circuit board
52
. The radiator plate
53
fulfills the function of radiating a radio wave, and its length is &lgr;/4 (&lgr;: wavelength of the radio wave). On the side edge of the radiator plate
53
, a short pin
54
extended toward the printed-circuit board
52
is integrally provided with the radiator plate
53
. The short pin
54
is electrically connected to the ground electrode
51
on the printed-circuit board
52
. That is, the radiator plate
53
is short-circuited to the ground electrode
51
through the short pin
54
. On the printed-circuit board
52
, a coaxial cable connection portion
52
a
is provided, and to the coaxial cable connection portion
52
a
a coaxial cable, a connector, etc. (not illustrated) through which a load dispatching to the radiator plate
53
takes place, are connected through a connection terminal
53
a
led out from the radiator plate
53
.
However, in the above described inverted F-type antenna, there were cases, in which in order to realize a small-sized antenna, a dielectric substance is inserted between the ground electrode on the printed-circuit board and the radiator plate, and the wavelength shortening effect of the dielectric substance is used. In these cases there is a problem that the antenna gain is decreased because of the effect of the dielectric substance.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an antenna device which can be used for mobile communication, having small size and high gain.
In accordance with the present invention, an antenna device is provided comprising an antenna unit including a basic body comprising at least one of dielectric ceramic and magnetic ceramic, at least one conductor disposed at least one of inside and on a surface of the basic body, and a feeding electrode for applying a voltage to the conductor, disposed on the surface of the basic body, a mounting board on which said antenna unit is mounted, a ground part in association with said mounting board and adapted to resonate with said antenna unit; and a length in the polarization direction of a radio wave of said ground part being about &lgr;/4 or more, where &lgr; is a wavelength of the radio wave, said basic body comprising; a first generally planar sheet having a plurality of spaced, first conductors formed on one major surface thereof, a second generally planar sheet having a plurality of spaced second conductors formed on one major surface thereof, said first and second generally planar sheets being laminated together to form an elongated structure wherein respective pairs of said first and second conductors are coupled to one another to form respective spiral loops of a spiral antenna so that a central axis of said spiral antenna extends generally parallel to a longitudinal direction of said elongated structure, each of said sheets being formed of a material having a relative permeability of 1<&mgr;<7 or a dielectric constant &egr; of 1<&egr;<130; and a feeding terminal coupled to one end of said spiral antenna so that said antenna unit forms a mono-pole antenna, said antenna unit and said ground part together functioning as a dipole antenna.
The at least one conductor comprises a metal mainly containing any one of copper, nickel, silver, palladium, platinum, or gold.
The antenna unit in accordance with an embodiment of the present invention has a wavelength shortening effect because the base member is formed of either a material having a dielectric constant &egr; of 1<&egr;<130 or a material having a relative permeability &mgr; of 1<&mgr;<7.
Further, the antenna unit in accordance with another embodiment of the present invention enables monolithic sintering of the conductive pattern composed of a base member and a conductor, because the conductive pattern is formed of a metal mainly containing any one of copper(Cu), nickel (Ni), silver (Ag), palladium (Pd), platinum (Pt), or gold (Ag).
In the above described antenna device, the ground part may comprise at least one of a ground electrode disposed on the mounting board and a ground portion of a high-frequency circuit portion mounted on the mounting board together with the antenna unit.
According to the above described structure and arrangement, because the antenna device comprises an antenna unit and a ground part resonant with the antenna unit having &lgr;/4 as the length in the polarization direction of a radio wave, the antenna unit is able to function as one pole of a dipole antenna and the ground part resonant with the antenna unit is able to function as the other pole of the dipole antenna. Therefore, at a resonant point, the antenna unit and ground part are able to act as a pair of antennas like a dipole antenna. As the result, an antenna device having as high a gain like a dipole antenna is made available although the antenna device is small-sized.
Further, a radio equipment mounted with such a small-sized antenna device having a high gain is also able to be made of small size and of a high gain.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.
REFERENCES:
patent: 4728962 (1988-03-01), Kitsuda et al.
patent: 5861852 (1999-01-01), Asakura et al.
patent: 5973651 (1999-10-01), Suesada et al.
patent: 5977927 (1999-11-01), Mandai et al.
patent: 6052096 (2000-04-01), Tsuru et al.
Asakura Kenji
Kanba Seiji
Mandai Harufumi
Shiroki Koji
Tsuru Teruhisa
Murata Manufacturing Co. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
Phan Tho
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