Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
2000-11-21
2001-10-09
Phan, Tho G (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S702000
Reexamination Certificate
active
06300909
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an antenna unit in which double resonance is realized by using two antennas and in which it is possible to simultaneously change both frequencies. The present invention also relates to a communication device using the antenna unit.
2. Description of the Related Art
Among conventional antenna units, the antenna unit which has been disclosed in Japanese Unexamined Patent Application Publication No. 11-136025 (Japanese Patent Application No. 10-204902) is taken as an example and described with reference to FIG.
8
.
In the drawing, an antenna unit
101
is shown. The unit
101
includes a switch
109
is coupled to an antenna
100
. The antenna
100
comprises a grounding electrode
103
, a radiation electrode
104
, a feeding electrode
106
, and a control electrode
108
provided on the surface of a basic body
102
made of a dielectric material. One end of the radiation electrode
104
is open circuited. Furthermore, the feeding electrode
106
is formed so as to be close to the open end of the radiation electrode
104
and is connected to a signal source
110
. Furthermore, one end of the switch
109
is connected to the control electrode
108
and the other end is grounded.
In the antenna unit
101
thus constructed, the radiation electrode
104
resonates as a microstrip antenna having a line length of &lgr;/4 where &lgr; is the wavelength and functions as an antenna when part of the resonance power is radiated into space.
It is possible to change frequencies using the switch
109
. That is, when the switch
109
is on, capacitance generated between the open end of the radiation electrode
104
and the control electrode
108
is connected so as to be in parallel with capacitance between the open end of the radiation electrode
104
and the grounding electrode
103
. On the other hand, when the switch is off, capacitance is not generated between the open end of the radiation electrode
104
and the control electrode
108
. Therefore, when the switch
109
is on, the frequency becomes relatively low, and when the switch is off, the frequency becomes relatively high.
However, in the conventional antenna unit
101
, frequencies of the single antenna unit
100
are to be switched over and it is difficult to realize broader bandwidth.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an antenna unit in which it is possible to realize broader bandwidth by establishing double resonance using two antennas and by switching over each frequency into another, and to provide a communication device using the antenna unit.
In order to attain the above-mentioned objects, an antenna unit according to the present invention comprises a basic body; a grounding electrode provided on one main surface of the basic body; a first radiation electrode, having an open end at one end thereof, comprising a first antenna and provided on the other main surface of the basic body; a second radiation electrode, having an open end at one end thereof, comprising a second antenna and provided on the other main surface of the basic body; a first connecting electrode provided on an end surface of the basic body for connecting the first radiation electrode to the grounding electrode; a second connecting electrode provided on the end surface of the basic body for connecting the second radiation electrode to the grounding electrode; a feeding electrode provided on the basic body for transmitting a signal to at least one of the first radiation electrode and the second radiation electrode; and a control electrode provided so as to be close to each of the open ends of the basic body for providing coupling between the open end of the first radiation electrode and the control electrode and between the open end of the second radiation electrode and the control electrode.
Furthermore, in an antenna unit according to the present invention, the first antenna and the second antenna have different resonance frequencies from each other.
Furthermore, in an antenna unit according to the present invention, the control electrode is formed on a surface different from the surface where the first connecting electrode and the second connecting electrode are formed.
Furthermore, in an antenna unit according to the present invention, the basic body is made of a dielectric material or a magnetic material of a nearly rectangular solid.
Furthermore, in an antenna unit according to the present invention, a slit which is oblique to each side of the other main surface of the basic body is formed on the other main surface of the basic body, and the first radiation electrode and the second radiation electrode are disposed so as to face each other across the slit.
Furthermore, in an antenna unit according to the present invention, the slit is formed so that the width at the side of one end is narrower than the width at the side of the other end.
Furthermore, in an antenna unit according to the present invention, the feeding electrode is disposed on an end surface of the basic body so as to be close to the first radiation electrode or the second radiation electrode via a gap.
Furthermore, in an antenna unit according to the present invention, the feeding electrode is integrally formed on the end surface of the basic body where the first connecting electrode or the second connecting electrode is provided, so as to be continuous with the first connecting electrode or the second connecting electrode.
Furthermore, in an antenna unit according to the present invention, the first radiation electrode and the second radiation electrode are disposed on the other main surface of the basic body so that the first radiation electrode and the second radiation electrode sandwich the feeding electrode, and the first radiation electrode, the second radiation electrode, and the feeding electrode are disposed so that their longitudinal directions are parallel to each other.
Furthermore, a communication device according to the present invention comprises an antenna unit having the above-mentioned construction.
In an antenna unit according to the present invention, double resonance is realized by using two antennas, and, by turning on and off a switch connected to a control electrode, coupling capacitances to determine the degree of frequency change of both resonance frequencies are increased or decreased and thus the frequencies can be changed. Therefore, it is possible to realize a much broader bandwidth when compared with the case where the frequencies of a single antenna are changed.
Furthermore, by providing a plurality of control electrodes and switches respectively connected thereto, and by turning on and off each of the switches, it is possible to establish a much broader bandwidth.
Furthermore, in a communication device according to the present invention, because an antenna unit where frequencies can be changed is provided, it is possible to establish a broader bandwidth.
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: 5861854 (1999-01-01), Kawahata et al.
patent: 5867126 (1999-02-01), Kawahata et al.
patent: 5903240 (1999-05-01), Kawahata et al.
patent: 6100849 (2000-08-01), Tsubaki et al.
patent: 6140968 (2000-10-01), Kawahata et al.
patent: 6177908 (2001-01-01), Kawahata et al.
patent: 11136025 (1999-05-01), None
Kawahata Kazunari
Tsubaki Nobuhito
Murata Manufacturing Co. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
Phan Tho G
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