Multifrequency inverted F-type antenna

Details Multifrequency inverted F-type antenna Multifrequency inverted F-type antenna

1999-07-29

2001-02-27

Ho, Tan (Department: 2821)

Communications: radio wave antennas

Antennas

Microstrip

C343S767000

Reexamination Certificate

active

06195048

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a multifrequency inverted F-type antenna used as an internal antenna of small, thin radio communication terminals such as, chiefly, portable telephones, and more particularly, it relates to a multifrequency inverted F-type antenna capable of receiving radio waves in multiple frequency bands without increasing its size.
BACKGROUND ART
In general, inverted F-type antennas have excellent characteristics as internal antennas of small, thin radio terminals typified by portable telephones.
FIG. 21
is a perspective view showing the typical construction of a conventional inverted F-type antenna.
Referring to
FIG. 21
, in the inverted F-type antenna
210
, an emission conductor
212
is arranged opposite a ground conductor
211
, the emission conductor
212
being connected to the ground conductor
2112
through a ground conductor
213
.
Also, a feeding point
212
a
is provided on emission conductor
212
, and power is supplied to the feeding point
212
a
by means of a coaxial feeding line
214
from power feeding source
215
through a hole
211
a provided in ground conductor
211
.
As is known, assuming that the length of emission conductor
212
is L
1
as shown in
FIG. 21
, the inverted F-type antenna
210
resonates with the frequency at which the length L
1
is about &lgr;/4 (where &lgr; is the wavelength).
However, with radio terminals of this type, it is demanded that the inverted F-type antenna should be capable of receiving two or more different frequency bands together in order for example to be capable of being employed in two or more systems.
The constructions shown in
FIG. 22
or
FIG. 23
are known as conventional constructions whereby it is made possible to receive two or more different frequency bands together, using an inverted F-type antenna.
FIG. 22
is a perspective view showing a conventional multifrequency inverted F-type antenna that is capable of receiving two or more different frequency bands together.
Referring to
FIG. 22
, in the multifrequency inverted F-type antenna
220
, two emission conductors
222
-
1
and
222
-
2
of different size are arranged in parallel with respect to ground conductor
221
; these two emission conductors
222
-
1
and
222
-
2
are connected to ground conductor
221
through respective ground conductors
223
-
1
and
223
-
2
; power is supplied to feeding point
222
-
1
a on emission conductor
222
-
1
from power feeding source
225
-
1
by coaxial feeding line
224
-
1
and power is supplied to feeding point
222
-
2
a
on emission conductor
222
-
2
from power feeding source
225
-
2
by coaxial feeding line
224
-
2
.
Specifically, in the multifrequency inverted F-type antenna
220
shown in
FIG. 22
, an arrangement is adopted whereby two single-frequency inverted F-type antennas that resonate in respectively different frequency bands are arranged adjacently; as a result, there is the problem that the installation area becomes large in order to permit the arrangement of these two single-frequency inverted F-type antennas.
FIG. 23
is a perspective view showing another conventional multifrequency inverted F-type antenna which is capable of receiving two or more different frequency bands at once.
Referring to
FIG. 23
, in the multifrequency inverted F-type antenna
230
, two emission conductors
232
-
1
and
232
-
2
of different size are arranged in stacked fashion relative to ground conductor
231
, these two emission conductors
232
-
1
and
232
-
2
being connected to ground conductor
231
through respective ground conductors
233
-
1
,
233
-
2
; feeding point
232
-
1
a on emission conductor
232
-
1
is supplied with power from power feeding source
235
-
1
by coaxial feeding line
234
-
1
, while feeding point
232
-
2
a
on emission conductor
232
-
2
is supplied with power from power feeding source
235
-
2
by means of coaxial feeding line
234
-
2
.
Specifically, with the construction shown in
FIG. 23
, two single-frequency inverted F-type antennas that resonate in respectively different frequency bands are arranged in stacked fashion; as a result, there is the problem that the installation volume becomes large owing to the increased height of the installation region in order to provide for the stacked arrangement of these two single-frequency inverted F-type antennas.
Thus, there was the problem that, with a conventional multifrequency inverted F-type antenna arranged to be capable of receiving simultaneously two or more different frequency bands, there was the problem that the installation area or installation volume became larger than that of a conventional single-frequency inverted F-type antenna, thereby presenting an obstacle to reducing the size and thickness of a radio terminal accommodating such a multifrequency inverted F-type antenna.
DISCLOSURE OF THE INVENTION
Accordingly, an object of the present invention is to provide a multifrequency inverted F-type antenna whereby radio waves of multiple frequency bands can be received without increase in size.
In order to achieve this object, the invention according to claim
1
is a multifrequency inverted F-type antenna comprising: a ground conductor; a short-circuit plate planted in the ground conductor; a first emission conductor arranged facing the short-circuit plate, having a cut-out part in its interior, and whose one end is connected to the short-circuit plate; and a second emission conductor arranged facing the short-circuit plate and formed within the cutout part of the first emission conductor.
Also, in the invention according to claim
2
, in the invention of claim
1
, the first emission conductor comprises a feeding point connection part whereby connection of the feeding point is effected, between the cut-out part and the short-circuit plate.
Also, in the invention according to claim
3
, in the invention of claim
1
, the second emission conductor is formed integrally with the first emission conductor.
Also, in the invention according to claim
4
, in the invention of claim
1
, the second emission conductor has a single projection and operates in two frequency bands dependent on the shape of the first emission conductor and the shape of the second emission conductor.
Also, in the invention according to claim
5
, in the invention of claim
4
, the first spacing between the first emission conductor and the ground conductor and the second spacing between the second emission conductor and the ground conductor are set to respectively different distances.
Also, in the invention according to claim
6
, in the invention of claim
4
, dielectric elements are arranged between at least one of either the first emission conductor and the ground conductor or the second emission conductor and the ground conductor, the first dielectric constant between the first emission conductor and the ground conductor and the second dielectric constant between the second emission conductor and the ground conductor being different.
Also, in the invention according to claim
7
, in the invention of claim
1
, the second emission conductor has a plurality of projections and operates in a plurality of frequency bands dependent on the shape of the first emission conductor and the shape of the second emission conductor.
Also, in the invention according to claim
8
, in the invention of claim
7
, the first spacing between the first emission conductor and the ground conductor and a plurality of second spacings between the projections of the second emission conductor and the ground conductor are set to respectively different distances.
Also, in the invention according to claim
9
, in the invention of claim
7
, a dielectric element is arranged in at least one of the spacings between the first emission conductor and the ground conductor and between the projections of the second emission conductor and the ground conductor, and the first dielectric constant between the first emission conductor and the ground conductor and the second dielectric constant between the projections of the second emission conductor and the

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