JP2003124727A - Dielectric antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a miniaturized dielectric antenna which can be used while being packaged on a circuit board and further has a wide available frequency bandwidth. SOLUTION: By constituting a dielectric antenna 10 in which an antenna element 13 composed of band-like conductors 13a-13j is provided on the surface of an insulated plate-like substrate 11b composed of dielectric ceramic materials, the rear end of the antenna element 13 is connected to an external terminal 12a for power feeding and the top end of the antenna element 13 is branched, the dielectric antenna can be miniaturized. By branching the top end of the antenna element 13, electrostatic capacitance is generated between each of branched conductors and a ground conductor around them. In the antenna element, a head capacity type antenna is formed by this electrostatic capacitance and the length of the antenna element is shortened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric antenna used in a mobile phone or a mobile radio communication device, and more particularly to a dielectric antenna capable of improving the mounting density on a circuit board.

[0002]

2. Description of the Related Art In recent years, with the spread of portable telephones and portable wireless communication devices, reduction in size and weight has been required. Although miniaturization of various electronic components such as semiconductor integrated circuits is rapidly progressing, antennas are obstacles to miniaturization of wireless communication devices. As is well known, the antenna is the entrance / exit of electromagnetic waves, and unless it resonates at the frequency used, the efficiency is extremely reduced. In the case of an ordinary dipole antenna, it is very difficult to miniaturize it because it requires a half wavelength of the used frequency. For this reason, various measures for miniaturizing the antenna have been proposed.

For example, in the antenna disclosed in Japanese Unexamined Patent Application Publication No. 10-13135, the antenna element is folded back so as to be substantially parallel to each other along the lengthwise direction, thereby reducing the size of the antenna and providing two frequencies. It is configured to resonate with the band.

Further, in the antenna disclosed in Japanese Patent Laid-Open No. 10-229304, by forming an antenna element on the surface of a dielectric substrate, further miniaturization can be achieved and the antenna can be easily mounted on a circuit board for use. I am devising so that I can do it.

[0005]

However, it is desired to increase and diversify the functions of portable telephones and portable wireless communication devices, and in order to realize this, the number of parts is often increased. Therefore, in order to reduce the size of the device, it is necessary to further reduce the size of the electronic component, especially the size of the antenna.

Further, since a portable telephone uses a wide frequency band of an ultra high frequency band, an antenna having a wide usable frequency band is required.

In view of the above problems, an object of the present invention is to provide a small dielectric antenna that can be mounted on a circuit board and used, and further, a small dielectric antenna having a wide usable frequency bandwidth. Is to provide.

[0008]

In order to achieve the above object, the present invention provides an antenna element made of a band-shaped conductor provided on the surface of a flat plate-shaped insulator made of a dielectric material, and an antenna element after the antenna element. The size of the dielectric antenna is reduced by constructing a dielectric antenna including an external power feeding terminal connected to an end of the antenna element and having a branched end portion of the antenna element.

By branching the tip of the antenna element, a capacitance is generated between the branched conductors and the surrounding ground conductor, and the capacitance causes the antenna element to be of the head capacity type. An antenna is constructed and the length of the antenna element is reduced.

By arranging at least two of the branched branches at the tip of the antenna element in parallel with each other, the traveling directions of the high-frequency currents flowing through the antenna element are the same, and electromagnetic waves are generated from these high-frequency currents. Improved the radiation efficiency of.

Further, a known inverted F-type antenna is formed by connecting a predetermined position on the rear end side of the antenna element to a grounding external terminal via a strip conductor.

Further, two antenna elements are provided, and the rear ends of each antenna element are both connected to the feeding external terminal to increase efficiency, and the resonance frequencies of the two antenna elements are mutually different. The usable frequency bandwidth is expanded by setting the length of each antenna element so that the frequencies are different.

Further, each of the two antenna elements is provided on a surface of a different flat plate-shaped insulator, and these two flat plate-shaped insulators are stacked to reduce the size.

Further, the antenna element is folded back into a rectangular wave shape to reduce the size.

By stacking another flat plate insulator on the surface of the flat plate insulator so as to sandwich the conductor, it is possible to prevent the conductor from being exposed to the outside and increase the strength. planned.

[0016]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing a dielectric antenna according to the first embodiment of the present invention, and FIGS. 2 and 3 are plan views showing an antenna element. In the first embodiment, an example of a 2.4 GHz band dielectric antenna currently used for mobile communication will be described.

In the figure, 10 is a dielectric antenna, which has a laminated element body 11 in which insulating flat plate-like substrates (hereinafter, simply referred to as substrates) 11a, 11b, 11c made of a dielectric ceramic material are laminated. External terminal 12 on one side
a and 12b are provided. In addition, the intermediate substrate 11
Conductors that form the antenna element 13 are provided on the upper surfaces of the substrate 11b and the lower substrate 11c. Also, the substrate 1
A plurality of dummy electrodes are formed on the back surface of 1c so as to be stably soldered and fixed when mounted on the circuit board 1.

The size of the laminated body 11 is such that the length L is 7
mm, the width W is 3 mm, and the thickness D is 1 mm. Further, in FIG. 2, the dimensional ratio of each portion is drawn to be equal to the dimensional ratio of the actual product.

The antenna element 13 formed on the upper surface of the substrate 11b is composed of strip-shaped conductors 13a to 13k, is an antenna element generally called an inverted F-type antenna, and its resonance frequency is set to 2.45 GHz, for example. , The feeding point impedance is set to, for example, about 50Ω. The conductors 13b to 13d are connected to the other end of the conductor 13a, one end of which is connected to the external terminal 12a serving as a feeding point, so as to intersect at right angles to the right 90 degrees in the order described.

Further, one ends of two strip-shaped conductors 13e and 13f are connected to the other end of the conductor 13d and intersect at right angles.

Further, one end of a conductor 13h provided on the lower layer substrate 11c is connected to the other end of the conductor 13e through a conductor 13g provided on a side surface of the laminated body 11, and further the conductor 13h. To the other end of the conductor 13i
The conductor 13f is connected so as to intersect with h at a right angle.
Is extended in the same direction as.

Here, the conductors 13f and 13i are arranged in parallel with each other, and the distance between them is set to 0.6 mm. The widths of the conductors 13f and 13i are both set to 0.2 mm, and the length of the conductor 13f is 2.4 m.
m, and the length of the conductor 13i is set to 2.6 mm. The width and length of the conductor 13e are set to 0.2 mm.

Further, at a position at a predetermined distance from one end side (feeding point) of the conductor 13a, one end of the strip-shaped conductor 13j is connected to the conductor 13a, and the conductor 13j is perpendicular to the conductor 13a. It is located in. Furthermore, the other end of the conductor 13j is connected to an external terminal 12b for grounding via a conductor 13k connected at a right angle to the conductor 13j.

In use, the dielectric antenna 10 is mounted on the circuit board 1, the feeding external terminal 12a is connected to the feeding land 2, and the connecting land 3a of the ground conductor 3 formed on the circuit board 1 is connected. An external terminal 12b for grounding is connected to.

The dielectric antenna 10 having the above structure is
Since the tip of the antenna element 13 is branched into two, one branch 13f and the other branch 13e, 1
Capacitance is generated between 3g, 13h, and 13i and the surrounding ground conductor, and this capacitance forms the antenna element 13 as a head capacity type antenna. As a result, the length of the antenna element 13 that resonates at 2.45 GHz is shortened.

Further, the conductors 13f and 13i of the antenna element 13 are arranged in parallel with each other, and the high-frequency currents flowing through these conductors 13f and 13i are directed in the same direction. The efficiency of radiation of electromagnetic waves from the electric current can be increased.

The VSWR of the dielectric antenna 10 is
This is shown in FIG. With the VSWR characteristics shown in FIG.
VSWR becomes 2 or less at 2.38 to 2.48 GHz,
At 2.44 GHz, the VSWR shows a low and favorable value of 1.0. As described above, according to the dielectric antenna 10 of the present embodiment, it is possible to obtain a small VSWR that is excellent in the frequency band to be used.

Incidentally, the dielectric antenna 10 of the first embodiment.
Changes the length or width of the branch conductors 13e, 13f, 13h, 13i, or the conductors 13j and 13a.
The resonance frequency and the impedance of the feeding point can be changed by changing the connection position with.

5 to 7 show comparative examples of the first embodiment. The dielectric antenna 20 of this comparative example is an antenna that resonates at 2.45 GHz similarly to the dielectric antenna 10, and differs from the dielectric antenna 10 in that the tip of the antenna element 23 is not branched.

In the case of the antenna element 23 whose tip portion is not branched like the dielectric antenna 20 of this comparative example, the size of the laminated body 21 is such that the length L is 8 mm, the width W is 3 mm, and the thickness D is. The size is 1 mm, which is larger than that of the dielectric antenna 10 of the first embodiment.

Further, VS of the dielectric antenna 20 of the comparative example is compared.
In the WR characteristics, as shown in FIG. 7, the frequency band in which VSWR is 2 or less is narrowed to 2.40 to 2.48 GHz, and the minimum value VSWR is 1.2.

As a result, the miniaturization of the dielectric antenna 10 of the first embodiment and good VSWR characteristics can be clearly understood.

Next, a second embodiment of the present invention will be described.

The second embodiment is similar to the first embodiment,
This is an example of a dielectric antenna for the 2.4 GHz band currently used in a mobile phone, and by adopting an array type having two antenna elements, it is possible to achieve a higher VSWR than the dielectric antenna 10 of the first embodiment. It is an expansion of a good frequency bandwidth.

FIG. 8 is a perspective view showing a dielectric antenna according to the third embodiment, FIG. 9 is a plan view of a first antenna element, and FIG. 10 is a plan view of a second antenna element.

In the figure, reference numeral 30 denotes a dielectric antenna, which has a laminated body 31 in which insulating flat plate-like substrates (hereinafter simply referred to as substrates) 31a, 31b, 31c made of a dielectric ceramic material are laminated. External terminal 32 on one side
a and 32b are provided. Also, the intermediate substrate 31
Conductors forming the antenna elements 33 and 34 are provided on the respective upper surfaces of the substrate b and the substrate 31c below it. Further, a plurality of dummy electrodes are formed on the back surface of the lowermost substrate 31c so as to be stably soldered and fixed when mounted on the circuit board 1.

Regarding the size of the laminated body 31, the length L1 is 10 mm, the width W is 3 mm, and the thickness D is 1 mm. Further, in FIGS. 9 and 10, the dimensional ratio of each part is drawn to be equal to the dimensional ratio of the actual product.

The antenna element 33 formed on the upper surface of the substrate 31b is composed of strip-shaped conductors 33a to 33t, is an element generally called an inverted F-type antenna, and has a resonance frequency set to 2.4 GHz, for example. The feeding point impedance is set to about 100Ω, for example. At the other end of the conductor 33a, one end of which is connected to the external terminal 32b serving as a power feeding point, conductors 33b to 33i are folded back and connected so as to meander in the order described, thereby forming a rectangular wave shape. Further, at the tip of the conductor 33i, the conductor 33
j and 33k are connected so as to branch in different directions. The conductor 33k extends in a direction orthogonal to the conductor 33i, and the conductor 33l is attached to the tip of the conductor 33k.
Are connected so that they are orthogonal to each other. Also, the conductor 33j
The conductor 33 provided on the side surface of the laminated body 31
m is connected and is connected to the conductor 33n provided on the substrate 31c through the conductor 33m. The other end of the conductor 33n is connected to one end of a conductor 33o arranged parallel to the conductor 33k so as to be orthogonal to each other. Further, the conductor 33o is connected to the other end of the conductor 33o.
It is arranged so that one ends of p are orthogonal to each other.

Also, the conductors 33a, 33c, 33
e, 33g, 33i, 33l, and 33p are arranged in parallel with each other, and the distance between the conductor 33l and the conductor 33p, which is a branched branch at the tip of the antenna element 33, is 0.55 mm.
And the distance between the conductor 33i and the conductor 33p is set to 0.6 mm. In addition, the conductors 33l, 3
The widths of 3p are both set to 0.2 mm, the length of the conductor 33l is set to 2.4 mm, and the length of the conductor 33p is set to 2.2 mm.

Further, with the conductor 33a as a boundary, the conductor 33
b-33p on the side opposite to the side where the conductors 33q-
33t is provided, and one end of the conductor 33q has a conductor 33a.
Is connected to the middle portion in the longitudinal direction at a right angle. Further, one end of the conductor 33r is connected to the other end of the conductor 33q at a right angle, one end of the conductor 33s is connected to the other end of the conductor 33r at a right angle, and the other end of the conductor 33s is connected via the conductor 33t. Is connected to an external terminal 32a which serves as a ground terminal.

The antenna element 34 formed on the upper surface of the substrate 31c is composed of strip-shaped conductors 34a to 34i, the resonance frequency is set to 2.5 GHz, and the feeding point impedance is set to about 100Ω, for example. At the other end of the conductor 34a, one end of which is connected to the external terminal 32b serving as a power feeding point, conductors 34b to 34f are folded back and connected so as to meander in the order of description to form a rectangular wave shape.

Further, the conductor 3 is attached to the tip of the conductor 34f.
4g and 34h are connected so as to branch in different directions, and a conductor 34i is connected to the tip of the conductor 34h at a right angle.

The conductors 34b to 34g are arranged on the side where the conductors 33o to 33r constituting the antenna element 33 are arranged, and the conductors 34a and 34g are arranged.
c, 34e, 34g, 34i are arranged in parallel with each other.

Further, the distance between the conductor 34g and the conductor 34i, which are branched branches at the tip of the antenna element 34, is set to 0.5 mm, and the distance between the conductor 34g and the conductor 34e is set to 0.65 mm. Has been done. The widths of the conductors 3g and 34i are both set to 0.2 mm, and the lengths of the conductors 34g and 34i are both set to 2.4 mm.

An open stub 35 made of a rectangular conductor is provided on the opposite side of the conductor 34a, and one end of the open stub 35 is connected to the middle portion of the conductor 34a at a right angle. There is. The open stub 35 has a length Lst of 2.75 mm and a width Wst of 0.3.
mm, the distance L3 between the connection position of the open stub 35 and the conductor 34a and the feeding point (external terminal 32b) is set to 0.9 mm, and the antenna element 33 and a plurality of antenna elements 33 are sandwiched across the substrate 31b. It is arranged so as to be capacitively coupled at some points.

Further, the impedance of the feeding point of the dielectric antenna 30 is generally the same as the above, since the feeding points of the two antenna elements 33 and 34 are connected to the same external terminal 32b, so that the high frequency input / output of the high frequency transmitting / receiving circuit is generally accepted. It becomes 50Ω which is set to the output impedance.

In use, the dielectric antenna 30 is mounted on the circuit board 1, and the grounding external terminal 32a is connected to the connection land 3a of the grounding conductor 3 formed on the circuit board 1 to supply external power. The terminal 32b is connected to the power feeding land 2.

In the dielectric antenna 30 having the above structure, the tip of the antenna element 33 is divided into two as described above.
Since it is branched into two, electrostatic capacitance is generated between the branched branch composed of the conductors 33k and 33l and the branched branch composed of the conductors 33j and 33m to 33p and the surrounding ground conductor, and this electrostatic capacity is generated. Accordingly, the antenna element 33 constitutes a head capacity type antenna. As a result, 2.
The length of the antenna element 33 that resonates at 4 GHz is shortened. Further, the conductor 3 of the antenna element 33
3l and the conductor 33p are arranged in parallel with each other, and the traveling directions of the high-frequency currents flowing through the conductors 33l and 33p are the same, so that the radiation efficiency of electromagnetic waves from these high-frequency currents is increased in the antenna element 33. Can be increased.

Further, since the tip end portion of the antenna element 34 is branched into two, an electrostatic capacitance is generated between the conductors 34g and 34i and the surrounding ground conductor, and this electrostatic capacitance causes the antenna element Reference numeral 33 constitutes a head capacity type antenna. By this, 2.5GH
The length of the antenna element 34 resonating in z is reduced. Further, the conductor 34g and the conductor 34i of the antenna element 34 are arranged in parallel to each other, and the traveling directions of the high-frequency currents flowing through these conductors 34g and 34i are the same. The radiation efficiency of electromagnetic waves from the high frequency current can be increased.

Since the dielectric antenna 30 is provided with the open stub 35, when the dielectric antenna 30 is mounted on the circuit board 1, the distance L2 from the ground conductor 3 formed on the circuit board 1 is reduced. It can be shorter than before. In the dielectric antenna 30 of the present embodiment, good characteristics could be obtained even if the distance L2 between the dielectric antenna 30 and the ground conductor 3 was set to 1 mm.

That is, the open stub 35 is the substrate 31b.
Since the antenna element 33 is disposed so as to be capacitively coupled at a plurality of positions with the antenna element 33 interposed therebetween,
3 and the open stub 35 are capacitively coupled, and the inductance component of the open stub 35 is connected in parallel to a part of the antenna element 33.
The length of the antenna element 33 is further shortened.

The VSWR of the dielectric antenna 30 is shown in FIG.
As shown in, the VSWRs of the individual antenna elements 33 and 34 are combined. Therefore, as compared with the case where the individual antenna elements 33 and 34 are used alone, the frequency bandwidth exhibiting a low VSWR is widened, and the antenna can be used in a wide band. In the VSWR characteristics shown in FIG. 11, VSWR is 3 or less at 2.15 to 2.66 GHz and VSWR is 1.4 and 2.48 GH at 2.25 GHz.
In z, VSWR shows a low and favorable value of 1.1. Thus, according to the dielectric antenna 30 of the present embodiment, as shown by the characteristic curve, it is possible to expand the usable bandwidth in the target frequency band.

Therefore, the dielectric antenna 30 of the present embodiment.
By using the dielectric antenna 30 for the circuit board 1
When mounted on the circuit board, the distance L2 to the ground conductor 3 formed on the circuit board 1 can be made shorter than before, which greatly contributes to miniaturization and integration of a mobile phone or a mobile wireless communication device. You can contribute.

Further, similar to the first and second embodiments, the length Lst and width Wst of the open stub 35, the connection position of the open stub 35 and the conductor 34a, and the branching of the tip end portions of the antenna elements 33, 34. Conductors 33j-33
Lengths and areas of p, 34g, and 34i, and conductors 33q to 3 that connect the feeding point and the ground end of the antenna element 33.
The resonance frequency and the feed point impedance can be changed by changing any of the entire length or area of 3t.

The first to third embodiments are merely specific examples of the present invention, and the present invention is not limited to these embodiments.

[0057]

As described above, according to the dielectric antennas of claims 1 to 8 of the present invention, the length of the antenna element can be adjusted to the frequency of use by branching the tip of the antenna element. It becomes possible to resonate at the used frequency with a length shorter than the normal length determined by the wavelength,
Since a good VSWR characteristic can be obtained even with a small size, it can greatly contribute to downsizing and integration of a mobile phone or a mobile wireless communication device.

[Brief description of drawings]

FIG. 1 is a perspective view showing a dielectric antenna according to a first embodiment of the present invention.

FIG. 2 is a plan view showing an antenna element according to the first embodiment of the present invention.

FIG. 3 is a plan view showing an antenna element according to the first embodiment of the present invention.

FIG. 4 is a diagram showing VSWR characteristics according to the first embodiment of the present invention.

FIG. 5 is a perspective view showing a dielectric antenna as a comparative example with the first embodiment of the present invention.

FIG. 6 is a plan view showing an antenna element in a comparative example with the first embodiment of the present invention.

FIG. 7 shows VS in a comparative example with the first embodiment of the present invention.
Diagram showing WR characteristics

FIG. 8 is a perspective view showing a dielectric antenna according to a third embodiment of the present invention.

FIG. 9 is a plan view showing a first antenna element according to a third embodiment of the present invention.

FIG. 10 is a plan view showing a second antenna element according to the third embodiment of the present invention.

FIG. 11 is a diagram showing VSWR characteristics in the third embodiment of the present invention.

[Explanation of symbols]

1 ... Circuit board, 2 ... Power feeding land, 3 ... Ground conductor, 3a
... Ground land, 10,30 ... Dielectric antenna, 11,
31 ... Layered body, 11a, 11b, 31a, 31b, 3
1c ... substrate, 12a, 32a ... grounding external terminal, 12
b, 32b ... External terminal for feeding, 13 ... Antenna element, 13a-13k ... Conductor, 33 ... First antenna element, 34 ... Second antenna element, 33a-33t, 34a-34
i ... conductor, 35 ... open stub.

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) H01Q 21/30 H01Q 21/30

Claims (8)

[Claims] 1. An antenna element comprising: an antenna element made of a band-shaped conductor provided on a surface of a flat plate-shaped insulator made of a dielectric material; and an external power feeding terminal connected to a rear end of the antenna element. A dielectric antenna, characterized in that the tip of the is branched. 2. The dielectric antenna according to claim 1, wherein at least two of the branched branches at the tip of the antenna element are arranged in parallel with each other. 3. The antenna element has a grounding external terminal, and the antenna element has a strip-shaped conductor whose one end is connected to a predetermined position on the rear end side, and the other end of the strip-shaped conductor is connected to the grounding external terminal. The dielectric antenna according to claim 1, wherein the dielectric antenna is connected. 4. The dielectric antenna according to claim 1, wherein the two antenna elements are provided, and a rear end of each antenna element is connected to the feeding external terminal. 5. The dielectric antenna according to claim 4, wherein each of the two antenna elements is set to have a length that resonates at a frequency different from each other. 6. The two antenna elements are respectively provided on the surfaces of different flat plate insulators, and the two flat plate insulators are laminated.
The dielectric antenna according to. 7. The dielectric antenna according to claim 4, wherein the antenna element is arranged so as to be folded back into a rectangular wave shape. 8. The dielectric antenna according to claim 1, wherein another flat plate insulator is laminated on the surface of the flat plate insulator so as to sandwich the conductor.