Information
-
Patent Grant
-
6229485
-
Patent Number
6,229,485
-
Date Filed
Monday, August 9, 199925 years ago
-
Date Issued
Tuesday, May 8, 200123 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Le; Hoanganh
- Alemu; Ephrem
Agents
-
CPC
-
US Classifications
Field of Search
US
- 343 700 MS
- 343 846
- 343 847
- 343 829
- 343 702
-
International Classifications
-
Abstract
An antenna device includes a flat ground conductor; a first flat radiation conductor disposed against the flat ground conductor interposing a first dielectric layer; a first short-circuit conductor connecting an end of the first flat radiation conductor and the flat ground conductor; a second flat radiation conductor disposed partly against an opposite side of the first flat radiation conductor with its other side facing the ground conductor interposing a second dielectric layer; a second short-circuit conductor connecting an end of the second flat radiation conductor and the flat ground conductor; and a supply point disposed on the first flat radiation conductor. With this structure, the first flat radiation conductor and the second flat radiation conductor are disposed partly against each other, which enables more size reduction than that of conventional antennas operating at the same resonant frequency.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an antenna device, and more particularly, is suitably applied to a portable telephone which is reduced in size.
2. Description of the Related Art
In small portable radio apparatus such as portable telephones, terminal units for personal handyphone system (PHS), or the like, a reduction in size, thickness and weight has been promoted with recent rapid development of such apparatuses. Correspondingly, antennas associated therewith are also required to have a reduced size, thickness and weight as well as higher performance.
An example of an antenna equipped in such a small portable radio apparatus is a micro-strip antenna (hereinafter referred to as the “MS antenna”). Further, commonly known as antennas, which are further reduced in size than the MS antennas, are a single-side short-circuited MS antenna having a short-circuit surface for short-circuiting a zero-potential surface at the center of a radiation conductor to a ground conductor, a laminar inverted-F antenna having a further reduced width of its short-circuit surface, and so on.
For example, as illustrated in
FIGS. 1A and 1B
, a conventional MS antenna
1
comprises a ground conductor
2
disposed on one side of a dielectric substrate
3
having a height h, and a rectangular radiation conductor
4
(length a×width b) formed on the other side of the substrate
3
using an etching technique or the like.
This MS antenna
1
is provided with a power supply point
5
at a predetermined position on the radiation conductor
4
so that the input impedance thereof is equal to the characteristic impedance of a power supply system. The MS antenna
1
operates as an antenna with power supplied thereto through the power supply point
5
.
As illustrated in
FIGS. 2A and 2B
, a single-side short-circuited MS antenna
6
comprises a short-circuit conductor
10
having a width Ws
1
identical to the width b of a radiation conductor
8
and a height h, disposed between the radiation conductor
8
and a ground conductor
7
, so as to short-circuit a zero-potential surface of the radiation conductor
8
to the ground conductor
7
. The zero-potential surface, at which an electric field is at “0,” is at a position corresponding to one half a/2 of the length a of the radiation conductor
4
in the normal MS antenna
1
.
With this structure, the single-side short-circuited MS antenna
6
only requires the radiation conductor
8
having a length dimension approximately one half of the length dimension of the radiation conductor
4
of the MS antenna
1
and still operates as an antenna at the same resonant frequency as the MS antenna
1
.
Further, as illustrated in
FIGS. 3A and 3B
, a laminar inverted-F antenna
10
is composed of a rectangular radiation conductor
12
(length c×width d) and a ground conductor
11
which are short-circuited by a laminar inverted-F short-circuit conductor
14
having a width Ws
2
smaller than the width Ws
1
of the short-circuit conductor
10
of the single-side short-circuited MS antenna
6
.
The laminar inverted-F antenna
10
can reduce the resonant frequency fr by virtue of the laminar inverted-F short-circuit conductor
14
having the width Ws
2
chosen to be smaller than the width Ws
1
of the short-circuit conductor
8
of the single-side short-circuited MS antenna
6
, and can further reduce the resonant frequency fr by virtue of the power supply point
5
defined at a position offset from the center line of the radiation conductor
12
by an offset amount Wx
2
, as compared with the power supply point
5
defined at the center of the radiation conductor
12
.
As mentioned above, since the laminar inverted-F antenna
10
is designed to reduce the resonant frequency fr more than the MS antenna
1
, it can be configured using the radiation conductor
12
(length c×width d) smaller than the radiation conductor
4
(length a×width b), when it is operated at the same frequency as the MS antenna
1
.
The single-side short-circuited MS antenna
6
and the laminar inverted-F antenna
10
, configured as described above, are required to be further reduced in size in response to the demand for increasingly smaller portable telephones in recent years.
SUMMARY OF THE INVENTION
In view of the foregoing, an object of this invention is to provide an antenna device which is capable of realizing a further reduction in size and weight.
The foregoing object and other objects of the invention have been achieved by the provision of an antenna device which comprises a flat ground conductor; a first flat radiation conductor disposed against the flat ground conductor interposing a first dielectric layer; a first short-circuit conductor connecting an end of the first flat radiation conductor and the flat ground conductor; a second flat radiation conductor disposed partly against an opposite side of the first flat radiation conductor to its other side facing the ground conductor interposing a second dielectric layer; a second short-circuit conductor connecting an end of the second flat radiation conductor and the flat ground conductor; and a supply point disposed on the first flat radiation conductor.
With the structure as above, the first flat radiation conductor and the second flat radiation conductor are disposed partly against each other, which enables more size reduction than that of conventional antennas in operating at the same resonant frequency with a conventional antenna.
The nature, principle and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings in which like parts are designated by like reference numerals or characters.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
FIGS. 1A and 1B
are a top plan view and a cross-sectional view illustrating the structure of a conventional MS antenna;
FIGS. 2A and 2B
are a top plan view and a cross-sectional view illustrating the structure of a conventional single-side short-circuited MS antenna;
FIGS. 3A and 3B
are a top plan view and a cross-sectional view illustrating the structure of a conventional laminar inverted-F antenna;
FIG. 4
is a block diagram illustrating the configuration of a portable radio apparatus according to a first embodiment of the present invention;
FIGS. 5A and 5B
are a top plan view and a cross-sectional view illustrating the structure of a laminar inverted-F antenna according to the first embodiment of the present invention;
FIG. 6
is a graph showing the relationship between the dimensions of an upper ground conductor of the laminar inverted-F antenna according to the first embodiment of the present invention and the resonant frequency;
FIG. 7
is a characteristic curve showing the resonant frequency of the laminar inverted-F antenna according to the first embodiment of the present invention;
FIGS. 8A and 8B
are a top plan view and a cross-sectional view illustrating the structure of a laminar inverted-F antenna according to a second embodiment of the present invention;
FIGS. 9A and 9B
are a top plan view and a cross-sectional view illustrating the structure of a laminar inverted-F antenna according to a third embodiment of the present invention;
FIGS. 10A and 10B
are a top plan view and a cross-sectional view illustrating the structure of a single-side short-circuited MS antenna according to a fourth embodiment of the present invention;
FIGS. 11A and 11B
are a top plan view and a cross-sectional view illustrating the structure of a single-side short-circuited MS antenna according to a fifth embodiment of the present invention;
FIGS. 12A and 12B
are a top plan view and a cross-sectional view illustrating the structure of a single-side short-circuited MS antenna according to a sixth embodiment of the present invention;
FIGS. 13A and 13B
are a top plan view and a cross-sectional view illustrating the structure of a laminar inverted-F antenna according to another embodiment of the present invention; and
FIGS. 14A and 14B
are a top plan view and a cross-sectional view illustrating the structure of a single-side short-circuited MS antenna according to another embodiment of the present invention.
DETAILED DESCRIPTION OF THE EMBODIMENT
Preferred embodiment of this present invention will be described with reference to the accompanying drawings:
(1) First Embodiment
In
FIG. 4
, a portable radio apparatus, generally designated by
20
, sends a voice signal S
21
collected through a microphone
21
to an encoder circuit
22
upon transmission. The encoder circuit
22
encodes the voice signal S
21
to generate audio data S
22
which is sent to a modulator circuit
23
. The modulator circuit
23
performs predetermined modulation processing based on the audio data S
22
to generate a modulation signal S
23
which is sent to a transmitter circuit
24
.
The transmitter circuit
24
digital-to-analog converts the modulation signal S
23
to generate an analog signal which is then frequency converted to generate a transmission signal S
25
. The transmission signal S
25
is amplified to a predetermined power level, and transmitted through a power supply line
25
and an external antenna
26
which comprises, for instance, an externally attached whip antenna.
Upon reception, the portable radio apparatus
20
receives a reception signal S
27
through the external antenna
26
and a planar antenna
27
, and sends the reception signal S
27
to a receiver circuit
27
through the power supply line
25
and a power supply line
28
. The receiver circuit
29
amplifies the reception signal S
29
to a predetermined power level, and then frequency converts the amplified signal to extract a baseband signal. Subsequently, the receiver circuit
29
analog-to-digital converts the baseband signal to a digital signal to generate a received data S
29
which is sent to a demodulator circuit
30
.
The demodulator circuit
30
performs predetermined demodulation processing on the received data S
29
to generate a demodulated signal S
30
which is sent to a decoder circuit
31
. The decoder circuit
31
decodes the demodulated signal S
30
to generate an analog signal, thus recovering a voice signal S
31
identical to an original voice signal
21
which is outputted through a speaker
32
as a voice.
The portable radio apparatus
20
, when in use, transmits a transmission signal S
24
and receives a reception signal S
27
with the external antenna
26
for both transmission and reception, which is drawn out from a housing
33
for use and otherwise can be retracted inside the housing
33
. The portable radio apparatus
20
also receives the reception signal S
27
through the planar antenna
27
, implemented by the laminar inverted-F antenna
27
dedicated to reception which is always accommodated within the housing
33
. In this way, the portable radio apparatus
20
conducts diversity reception, during reception, to improve the reception performance. In this embodiment, the structure of the laminar inverted-F antenna
27
, constituting the planar antenna
27
, will be described in detail.
In
FIGS. 5A and 5B
, where parts corresponding to those in
FIGS. 3A and 3B
are designated with the same reference numerals, a laminar inverted-F antenna according to the present invention, generally designated by
27
. Which comprises a radiation conductor
52
having a length (e-L) and a width f, a ground conductor
51
, and a laminar inverted-F short-circuit conductor
14
which short-circuits the ground conductor
51
and the radiation conductor
52
having a width Ws
2
and a height h, these to form a normal laminar inverted-F antenna. An upper ground conductor
53
disposed at a position spaced from the radiation conductor
52
by a height h and having a length g and a width f, is short-circuited to the ground conductor
51
by a side ground conductor
54
having a width f, which is disposed on an open end side on which the laminar inverted-F short-circuit conductor
14
is not disposed.
With the foregoing structure, the laminar inverted-F antenna
27
is designed to act as a first antenna with a lower dielectric layer
56
formed of an air layer between the radiation conductor
52
and the ground conductor
51
, as well as to act as a second antenna with an upper dielectric layer
55
formed of an air layer between the radiation conductor
52
and the upper ground conductor
53
.
The laminar inverted-F antenna
27
also has a power supply point
5
defined at a position spaced by a distance l from an end of the upper ground conductor
53
overlying the radiation conductor
52
, and offset from the center line of the radiation conductor
52
by an offset amount Wx
2
, so that the input impedance of the radiation conductor
52
is equal to the characteristic impedance of a power supply system, thus achieving the impedance matching.
With the foregoing structure, the laminar inverted-F antenna device
27
has a first area S
1
on one side of the radiation conductor
52
which acts as a first antenna in combination of the ground conductor
51
short-circuited by the laminar inverted-F short-circuit conductor
14
, and an additional second area S
2
on the other side of the radiation conductor
52
which acts as a second antenna in combination of the upper ground conductor
53
short-circuited by the side ground conductor
54
. Thus, the laminar inverted-F antenna device
27
has an increased area (S
1
+S
2
), as a whole, for the radiation conductor
52
, which acts as the overall antenna, resulting in a correspondingly increased capacitance to further reduce the resonant frequency fr.
Actually, in the laminar inverted-F antenna
27
, when the length (e-L) of the radiation conductor
52
is reduced while the distance L from the end of the radiation conductor
52
to the side ground conductor
54
is extended, the second area S
2
is reduced, resulting in a correspondingly reduced capacitance to increase the resonant frequency fr. Conversely, when the length (e-L) of the radiation conductor
52
is extended while the distance L is reduced, the second area S
2
is increased, resulting in a correspondingly increased capacitance to reduce the resonant frequency fr.
Also, in the laminar inverted-F antenna
27
, when the length g of the upper ground conductor
53
is reduced while the distance l from the end of the upper ground conductor
53
to the power supply point
5
is extended, the second area S
2
is reduced, resulting in a correspondingly reduced capacitance to increase the resonant frequency fr. Conversely, when the length g of the upper ground conductor
53
is extended while the distance l from the end of the upper ground conductor
53
to the power supply point
5
is reduced, the second area S
2
is increased, resulting in a correspondingly increased capacitance to reduce the resonant frequency fr.
Actually, as shown in
FIG. 6
, it can be seen that in the laminar inverted-F antenna
27
, as the length g of the upper ground conductor
5
is longer, the distance l from the end of the upper ground conductor
53
to the power supply point
5
is more reduced to cause an increase in the second area S
2
, resulting in a correspondingly increased capacitance to reduce the resonant frequency fr.
As described above, the laminar inverted-F antenna
27
can provide a desired resonant frequency by changing the length g of the upper ground conductor
53
and the length (e-L) of the radiation conductor
52
to adjust the area of the radiation conductor
52
which acts as the first and second antennas.
More specifically, as can be seen from the result of an experiment shown in
FIG. 7
, the resonant frequency resulting from the use of the laminar inverted-F antenna
27
according to the present invention is at approximately 790 MHz, whereas the resonant frequency resulting from the use of the conventional laminar inverted-F antenna
10
is at approximately 960 MHz. The resonant frequency is significantly reduced by approximately 170 MHz.
With the foregoing structure, the laminar inverted-F antenna
27
according to the present invention employs a double-layer structure which includes a first antenna formed of a combination of the radiation conductor
52
and the ground conductor
51
short-circuited by the laminar inverted-F short-circuit conductor
14
, and a second antenna formed of a combination of the radiation conductor
52
and the upper ground conductor
53
short-circuited by the side ground conductor
54
. Thus, the first area S
1
on the one side of the radiation conductor
52
acting as the first antenna and the second area S
2
on the other side of the radiation conductor
52
acting as the second antenna are added to increase the area of the radiation conductor
52
acting as the overall antenna, so that the capacitance of the antenna can be increased as a whole. Consequently, the laminar inverted-F antenna
27
can reduce the resonant frequency fr without causing increased dimensions (length e×width f), as compared with the dimensions (length c×width d) of the conventional laminar inverted-F antenna
10
.
Thus, the laminar inverted-F antenna
27
can further reduce the overall size thereof by an amount corresponding to a reduction in the resonant frequency fr, when operated at the same frequency as the conventional laminar inverted-F antenna
10
, thereby making it possible to reduce the area of the antenna equipped in the portable radio apparatus
20
and hence the entire size of the portable radio apparatus
20
.
In addition, since the laminar inverted-F antenna
27
employs the upper dielectric layer
55
and the lower dielectric layer
56
formed of air layers, the laminar inverted-F antenna
27
can be reduced in weight as compared with the conventional laminar inverted-F antenna
10
which employs the dielectric substrate
3
.
According to the foregoing structure, the laminar inverted-F antenna
27
in the first embodiment employs the double-layer structure which includes the first antenna formed of a combination of the radiation conductor
52
and the ground conductor
51
short-circuited by the laminar inverted-F short-circuit conductor
14
, and the second antenna formed of a combination of the radiation conductor
52
and the upper ground conductor
53
short-circuited by the side ground conductor
54
, thereby making it possible to further reduce the resonant frequency fr and the size of the overall antenna.
(2) Second Embodiment
Since a second embodiment has the same circuit configuration as the first embodiment except for a circuit associated with a laminar inverted-F antenna
60
, later described, which is employed instead of the laminar inverted-F antenna
27
of the portable radio apparatus
20
(FIG.
4
), description will be made herein only on the structure of the laminar inverted-F antenna
60
.
In
FIGS. 8A and 8B
, where parts corresponding to those in
FIGS. 5A and 5B
are designated with the same reference numerals, the laminar inverted-F antenna
60
comprises a side ground conductor
61
disposed on the side of an upper ground conductor
53
orthogonal to an open end side, on which a laminar inverted-F short-circuit conductor
14
is not disposed, so as to short-circuit the upper ground conductor
53
to a ground conductor
51
in place of the side ground conductor
54
of the laminar inverted-F antenna
27
in the first embodiment. In addition, a radiation conductor
62
has a width f′, and is spaced apart from the side ground conductor
61
by a distance L′ to avoid short-circuiting.
Again, in the laminar inverted-F antenna
60
, the upper ground conductor
53
and the ground conductor
51
are short-circuited by the side ground conductor
61
in a manner similar to the laminar inverted-F antenna
27
, so that a first antenna can be formed of a combination of the radiation conductor
62
and the ground conductor
51
short-circuited by the laminar inverted-F short-circuit conductor
14
, and a second antenna can be formed of a combination of the radiation conductor
62
and the upper ground conductor
53
short-circuited by the side ground conductor
61
.
In the foregoing structure, the first area S
1
on one side of the radiation conductor
62
acting as the first antenna and the second area S
2
on the other side of the radiation conductor
62
acting as the second antenna are added to increase the area of the radiation conductor
62
acting as the overall antenna, so that the capacitance of the antenna device can be increased. Consequently, the laminar inverted-F antenna
60
can reduce the resonant frequency fr without causing increased dimensions (length e×width f) as compared with the dimensions (length c×width d) of the conventional laminar inverted-F antenna
10
.
Thus, the laminar inverted-F antenna
60
can further reduce the overall size thereof by an amount corresponding to a reduction in the resonant frequency fr, when operated at the same frequency as the conventional laminar inverted-F antenna
10
, thereby making it possible to reduce the area of the antenna equipped in the portable radio apparatus
20
and hence the entire size of the portable radio apparatus
20
.
In addition, since the laminar inverted-F antenna
60
employs an upper dielectric layer
55
and a lower dielectric layer
56
formed of air layers, the laminar inverted-F antenna
60
can be reduced in weight as compared with the conventional laminar inverted-F antenna
10
which employs the dielectric substrate
3
.
According to the foregoing structure, the laminar inverted-F antenna
60
in the second embodiment employs the double-layer structure which includes the first antenna formed of a combination of the radiation conductor
62
and the ground conductor
51
short-circuited by the laminar inverted-F short-circuit conductor
14
, and the second antenna formed of a combination of the radiation conductor
62
and the upper ground conductor
53
short-circuited by the side ground conductor
61
, thereby making it possible to further reduce the resonant frequency fr and the size of the overall antenna.
(3) Third Embodiment
Since a third embodiment has the same circuit configuration as the first embodiment except for a circuit associated with a laminar inverted-F antenna
70
, later described, which is employed instead of the laminar inverted-F antenna
27
of the portable radio apparatus
20
(FIG.
4
), description will be made herein only on the structure of the laminar inverted-F antenna
70
.
In
FIGS. 9A and 9B
, where parts corresponding to those in
FIGS. 8A and 8B
are designated with the same reference numerals, the laminar inverted-F antenna
70
comprises both the side ground conductor
54
of the laminar inverted-F antenna
27
in the first embodiment, and the side ground conductor
61
of the laminar inverted-F antenna
60
in the second embodiment.
Again, in the laminar inverted-F antenna
70
, an upper ground conductor
53
and a ground conductor
51
are short-circuited by the side ground conductors
54
,
61
in a manner similar to the laminar inverted-F antennas
27
,
60
, so that a first antenna can be formed of a combination of a radiation conductor
62
and the ground conductor
51
short-circuited by the laminar inverted-F short-circuit conductor
14
, and a second antenna can be formed of a combination of the radiation conductor
62
and the upper ground conductor
53
short-circuited by the side ground conductors
54
,
61
.
In the foregoing structure, the laminar inverted-F antenna
70
is such that a first area S
1
on one side of the radiation conductor
62
acting as the first antenna and a second area S
2
on the other side of the radiation conductor
62
acting as the second antenna are added to increase the area of the radiation conductor
62
acting as the overall antenna, so that the capacitance of the antenna can be increased as a whole. Consequently, the laminar inverted-F antenna
70
can reduce the resonant frequency fr without causing increased dimensions (length e×width f), as compared with the dimensions (length c×width d) of the conventional laminar inverted-F antenna
10
.
Thus, the laminar inverted-F antenna
70
can further reduce the overall size thereof by an amount corresponding to a reduction in the resonant frequency fr, when operated at the same frequency as the conventional laminar inverted-F antenna
10
, thereby making it possible to reduce the area of the antenna equipped in the portable radio apparatus
20
and hence the entire size of the portable radio apparatus
20
.
In addition, since the laminar inverted-F antenna
70
employs an upper dielectric layer
55
and a lower dielectric layer
56
formed of air layers, the laminar inverted-F antenna
70
can be reduced in weight as compared with the conventional laminar inverted-F antenna
10
which employs the dielectric substrate
3
.
According to the foregoing structure, the laminar inverted-F antenna
70
in the third embodiment employs the double-layer structure which includes the first antenna formed of a combination of the radiation conductor
62
and the ground conductor
51
short-circuited by the laminar inverted-F short-circuit conductor
14
, and the second antenna formed of a combination of the radiation conductor
62
and the upper ground conductor
53
short-circuited by the side ground conductors
54
,
61
, thereby making it possible to further reduce the resonant frequency fr and the size of the overall antenna.
(4) Fourth Embodiment
Since a fourth embodiment has the same circuit configuration as the first embodiment except for a circuit associated with a single-side short-circuited MS antenna
80
, later described, which is employed instead of the laminar inverted-F antenna
27
of the portable radio apparatus
20
(FIG.
4
), description will be made herein only on the structure of the single-side short-circuited MS antenna
80
.
In
FIGS. 10A and 10B
, where parts corresponding to those in
FIGS. 2A and 2B
are designated with the same reference numerals, the single-side short-circuited MS antenna
80
comprises a radiation conductor
82
having a length (e-L) and a width f, and a ground conductor
81
, short-circuited by a short-circuit conductor
10
having a width f and a height h to form a normal single-side short-circuited antenna. The antenna
80
also comprises an upper ground conductor
83
disposed at a position spaced from the radiation conductor
82
by a height h and having a length g and a width f, which is short-circuited to the ground conductor
81
by a side ground conductor
84
having a width f, which is disposed on an open end side on which the short-circuit conductor
10
is not disposed.
With the foregoing structure, the single-side short-circuited MS antenna
80
is designed to operate as a first antenna with a lower dielectric layer
86
formed of an air layer between the radiation conductor
82
and the ground conductor
81
, as well as to operate as a second antenna with an upper dielectric layer
85
formed of an air layer between the radiation conductor
82
and the upper ground conductor
83
.
The single-side short-circuited MS antenna
80
also has a power supply point
5
defined at a position on the center line of the radiation conductor
82
spaced by a distance l from an end of the upper ground conductor
83
overlying the radiation conductor
82
, so that the input impedance of the radiation conductor
82
is equal to the characteristic impedance of a power supply system, thus achieving the impedance matching.
With the foregoing structure, the single-side short-circuited MS antenna
80
has a first area S
1
on one side of the radiation conductor
82
which acts as the first antenna in combination of the ground conductor
81
short-circuited by the short-circuit conductor
10
, and an additional second area S
2
on the other side of the radiation conductor
82
which acts as the second antenna in combination of the upper ground conductor
83
short-circuited by the side ground conductor
84
. Thus, the single-side short-circuited MS antenna
80
has an increased area (S
1
+S
2
), as a whole, for the radiation conductor
82
, which acts as the overall antenna, resulting in an increased capacitance to further reduce the resonant frequency fr.
Actually, in the single-side short-circuited MS antenna
80
, when the length (e-L) of the radiation conductor
82
is reduced while the distance L from the end of the radiation conductor
82
to the side ground conductor
84
is extended, the second area S
2
is reduced, resulting in a correspondingly reduced capacitance to increase the resonant frequency fr. Conversely, when the length (e-L) of the radiation conductor
82
is extended while the distance L is reduced, the second area S
2
is increased, resulting in a correspondingly increased capacitance to reduce the resonant frequency fr.
Also, in the single-side short-circuited MS antenna
80
, when the length g of the upper ground conductor
83
is reduced while the distance l from the end of the upper ground conductor
83
to the power supply point
5
is extended, the second area S
2
is reduced, resulting in a correspondingly reduced capacitance to increase the resonant frequency fr. Conversely, when the length g of the upper ground conductor
83
is extended while the distance l from the end of the upper ground conductor
83
to the power supply point
5
is reduced, the second area S
2
is increased, resulting in a correspondingly increased capacitance to reduce the resonant frequency fr.
As described above, the single-side short-circuited MS antenna
80
can provide a desired resonant frequency by changing the length g of the upper ground conductor
83
and the length (e-L) of the radiation conductor
82
to adjust the area of the radiation conductor
82
which acts as the first and second antennas.
With the foregoing structure, the single-side short-circuited MS antenna
80
according to the fourth embodiment employs a double-layer structure which includes the first antenna formed of a combination of the radiation conductor
82
and the ground conductor
81
short-circuited by the short-circuit conductor
10
, and the second antenna formed of a combination of the radiation conductor
82
and the upper ground conductor
83
short-circuited by the side ground conductor
84
. Thus, the first area S
1
on the one side of the radiation conductor
82
acting as the first antenna and the second area S
2
on the other side of the radiation conductor
82
acting as the second antenna are added to increase the area of the radiation conductor
82
acting as the overall antenna, so that the capacitance of the antenna can be increased as a whole. Consequently, the single-side short-circuited MS antenna
80
can reduce the resonant frequency fr without causing increased dimensions (length e×width f), as compared with those of the conventional single-side short-circuited MS antenna
6
.
Thus, the single-side short-circuited MS antenna
80
can further reduce the overall size thereof by an amount corresponding to a reduction in the resonant frequency fr, when operated at the same frequency as the conventional single-side short-circuited MS antenna
6
, thereby making it possible to reduce the area of the antenna equipped in the portable radio apparatus
20
and hence the entire size of the portable radio apparatus
20
.
In addition, since the single-side short-circuited MS antenna
80
employs the upper dielectric layer
85
and the lower dielectric layer
86
formed of air layers, the single-side short-circuited MS antenna
80
can be reduced in weight as compared with the conventional single-side short-circuited MS antenna
6
which employs the dielectric substrate
9
.
According to the foregoing structure, the single-side short-circuited MS antenna
80
in the fourth embodiment employs the double-layer structure which includes the first antenna formed of a combination of the radiation conductor
82
and the ground conductor
81
short-circuited by the short-circuit conductor
10
, and the second antenna formed of a combination of the radiation conductor
82
and the upper ground conductor
83
short-circuited by the side ground conductor
84
, thereby making it possible to further reduce the resonant frequency fr and the size of the overall antenna.
(5) Fifth Embodiment
Since a fifth embodiment has the same circuit configuration as the first embodiment except for a circuit associated with a single-side short-circuited MS antenna
90
, later described, which is employed instead of the single-side short-circuited MS antenna
80
of the portable radio apparatus
20
(FIG.
4
), description will be made herein only on the structure of the single-side short-circuited MS antenna
90
.
In
FIGS. 11A and 11B
, where parts corresponding to those in
FIGS. 10A and 10B
are designated with the same reference numerals, the single-side short-circuited MS antenna
90
comprises a side ground conductor
91
disposed on a side of an upper ground conductor
83
orthogonal to an open end side, on which a short-circuit conductor
10
is not disposed, so as to short-circuit the upper ground conductor
83
and a ground conductor
81
, instead of the side ground conductor
84
of the single-side short-circuited MS antenna
80
in the fourth embodiment. In addition, a radiation conductor
92
has a width f′ and is spaced apart from a side ground conductor
91
by a distance L′ to avoid short-circuiting.
Again, in the single-side short-circuited MS antenna
90
, the upper ground conductor
83
and the ground conductor
81
are short-circuited by the side ground conductor
91
in a manner similar to the single-side short-circuited MS antenna
80
, so that a first antenna can be formed of a combination of the radiation conductor
92
and the ground conductor
81
short-circuited by the short-circuit conductor
10
, and a second antenna can be formed of a combination of the radiation conductor
92
and the upper ground conductor
83
short-circuited by the side ground conductor
91
.
In the foregoing structure, the single-side short-circuited MS antenna
90
is such that a first area S
1
on one side of the radiation conductor
92
acting as the first antenna and a second area S
2
on the other side of the radiation conductor
92
acting as the second antenna are added to increase the area of the radiation conductor
92
acting as the overall antenna, so that the capacitance of the antenna can be increased as a whole. Consequently, the single-side short-circuited MS antenna
90
can reduce the resonant frequency fr without causing increased dimensions (length e×width f), as compared with those of the conventional single-side short-circuited MS antenna
6
.
Thus, the single-side short-circuited MS antenna
90
can further reduce the overall size thereof by an amount corresponding to a reduction in the resonant frequency fr, when operated at the same frequency as the conventional single-side short-circuited MS antenna
6
, thereby making it possible to reduce the area of the antenna equipped in the portable radio apparatus
20
and hence the entire size of the portable radio apparatus
20
.
In addition, since the single-side short-circuited MS antenna
90
employs an upper dielectric layer
85
and a lower dielectric layer
86
formed of air layers, the single-side short-circuited MS antenna
90
can be reduced in weight as compared with the conventional single-side short-circuited MS antenna
6
which employs the dielectric substrate
9
.
According to the foregoing structure, the single-side short-circuited MS antenna
90
in the fifth embodiment employs the double-layer structure which includes the first antenna formed of a combination of the radiation conductor
92
and the ground conductor
81
short-circuited by the short-circuit conductor
10
, and the second antenna formed of a combination of the radiation conductor
92
and the upper ground conductor
83
short-circuited by the side ground conductor
91
, thereby making it possible to further reduce the resonant frequency fr and the size of the overall antenna.
(6) Sixth Embodiment
Since a sixth embodiment has the same circuit configuration as the first embodiment except for a circuit associated with a single-side short-circuited MS antenna
100
, later described, which is employed instead of the single-side short-circuited MS antenna
80
of the portable radio apparatus
20
(FIG.
4
), description will be made herein only on the structure of the single-side short-circuited MS antenna
100
.
In
FIGS. 12A and 12B
, where parts corresponding to those in
FIGS. 11A and 11B
are designated the same reference numerals, the single-side short-circuited MS antenna
100
comprises both the side ground conductor
84
of the single-side short-circuited MS antenna
80
in the fourth embodiment, and the side ground conductor
91
of the single-side short-circuited MS antenna
90
in the fifth embodiment.
Again, in the single-side short-circuited MS antenna
100
, an upper ground conductor
83
and a ground conductor
81
are short-circuited by the side ground conductors
84
,
91
in a manner similar to the single-side short-circuited MS antennas
80
,
90
, so that a first antenna can be formed of a combination of a radiation conductor
92
and the ground conductor
81
short-circuited by a short-circuit conductor
10
, and a second antenna can be formed of a combination of the radiation conductor
92
and the upper ground conductor
83
short-circuited by the side ground conductors
84
,
91
.
In the foregoing structure, the single-side short-circuited MS antenna
100
is such that a first area S
1
on one side of the radiation conductor
92
acting as the first antenna and a second area S
2
on the other side of the radiation conductor
92
acting as the second antenna are added to increase the area of the radiation conductor
92
acting as the overall antenna, so that the capacitance of the antenna can be increased as a whole. Consequently, the single-side short-circuited MS antenna
100
can reduce the resonant frequency fr without causing increased dimensions (length e×width f), as compared with those of the conventional single-side short-circuited MS antenna
6
.
Thus, the single-side short-circuited MS antenna
100
can further reduce the overall size thereof by an amount corresponding to a reduction in the resonant frequency fr, when operated at the same frequency as the conventional single-side short-circuited MS antenna
6
, thereby making it possible to reduce the area of the antenna equipped in the portable radio apparatus
20
and hence the entire size of the portable radio apparatus
20
.
In addition, since the single-side short-circuited MS antenna
100
employs an upper dielectric layer
85
and a lower dielectric layer
86
formed of air layers, the single-side short-circuited MS antenna
100
can be reduced in weight as compared with the conventional single-side short-circuited MS antenna
6
which employs the dielectric substrate
9
.
According to the foregoing structure, the single-side short-circuited MS antenna
100
in the sixth embodiment employs the double-layer structure which includes the first antenna formed of a combination of the radiation conductor
92
and the ground conductor
81
short-circuited by the short-circuit conductor
10
, and the second antenna formed of a combination of the radiation conductor
92
and the upper ground conductor
83
short-circuited by the side ground conductors
84
,
91
, thereby making it possible to further reduce the resonant frequency fr and the size of the overall antenna.
(7) Other Embodiments
While the foregoing first to third embodiments have been described for the laminar inverted-F antennas
27
,
60
,
70
which have the upper dielectric layers
55
formed of air layers, the present invention is not limited to such particular dielectric layers as disclosed. Alternatively, as a laminar inverted-F antenna
110
illustrated in
FIGS. 13A and 13B
, a dielectric substrate
111
having a predetermined width Ws
3
and a height h and made, for example, of glass fiber can be used instead of the upper dielectric layer
55
. In this case, a variety of other materials can also be used for the dielectric substrate
111
other than glass fiber. In addition, the resonant frequency can be manipulated by adjusting the predetermined width Ws
3
of the dielectric substrate
111
.
Also, while the foregoing fourth to sixth embodiments have been described for the single-side short-circuited MS antennas
80
,
90
,
100
which have the upper dielectric layers
85
formed of air layers, the present invention is not limited to such particular dielectric layers as disclosed. Alternatively, as a single-side short-circuited MS antenna
120
illustrated in
FIGS. 14A and 14B
, a dielectric substrate
121
having a predetermined width Ws
4
and a height h and made, for example, of glass fiber can be used instead of the upper dielectric layer
85
. In this case, a variety of other materials can also be used for the dielectric substrate
121
other than glass fiber. In addition, the resonant frequency can be manipulated by adjusting the predetermined width Ws
4
of the dielectric substrate
121
.
Further, while the foregoing first to sixth embodiments have been described in connection with the structures in which the upper dielectric layer
55
and the lower dielectric layer
56
or the upper dielectric layer
85
and the lower dielectric layer
86
are formed as separated, the present invention is not limited to such a structure. Alternatively, the upper dielectric layer and the lower dielectric layer can be integrally formed.
Further, in the foregoing first to sixth embodiments, the upper ground conductor
53
or
83
and the ground conductor
51
or
81
are short-circuited by the side ground conductor
54
,
61
,
84
or
91
. The present invention, however, is not limited to such a structure, and in the alternative, the upper ground conductor and the ground conductor can be formed by bending an integrated conductor.
Further, in the foregoing first to sixth embodiments, the antenna device according to the present invention is applied to laminar inverted-F antennas and single-side short-circuited MS antennas. The present invention, however, is not limited to these particular types of antennas, but can be applied to a variety of other planar antennas which exhibit a varying resonant frequency depending on the area of a radiation conductor.
While there has been described in connection with the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be aimed, therefore, to cover in the appended claims all such changes and modifications as fall within the true spirit and scope of the invention.
Claims
- 1. An antenna device comprising:a first flat ground conductor; a flat radiation conductor having a side thereof disposed facing said first flat ground conductor interposing a first dielectric layer; a first short-circuit conductor connecting a first edge of said flat radiation conductor and said first flat ground conductor; a second flat ground conductor disposed facing and spaced apart from and partially overlapping another side of said flat radiation conductor opposite said side facing said first flat ground conductor and interposing a second dielectric layer between said flat radiation conductor and said second flat ground conductor; a second short-circuit conductor connecting said second flat ground conductor and said first flat ground conductor, wherein said second short-circuit conductor is disposed spaced apart a predetermined distance from a second edge opposite said first edge of said flat radiation conductor; and a power supply point disposed at a predetermined position on said flat radiation conductor.
- 2. The antenna device according to claim 1, whereinsaid power supply point and said first short-circuit conductor are formed so that said antenna device functions as a laminar inverted-F antenna.
- 3. The antenna device according to claim 1, whereinsaid power supply point and said first short-circuit conductor are formed so that said antenna device functions as a single side short-circuited micro-strip antenna.
- 4. The antenna device according to claim 1, wherein said first and second dielectric layers are respective air layers.
Priority Claims (1)
Number |
Date |
Country |
Kind |
10-226341 |
Aug 1998 |
JP |
|
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Kind |
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Limatainen et al. |
Aug 1991 |
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5307075 |
Huynh |
Apr 1994 |
|
5801660 |
Ohtsuka et al. |
Sep 1998 |
|
6002367 |
Engblom et al. |
Dec 1999 |
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