JP2002271129A - Antenna element and communications equipment using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antenna element to be used for the communications equipment of a traveling object, capable of improving the radiating efficiency and realizing band widening, regardless of the shape of the circuit board conductor by setting excitation at the antenna as being concluded, and to provide communications equipment which uses the antenna element. SOLUTION: This antenna element is provided with two similar radiating conductors extended to symmetric directions from a certain position on the surface of a board constituted of dielectric, and the edge of one radiating conductor near the other radiating conductor is formed as a power feeding edge. The edge of the other radiating conductor near one radiating conductor is formed as a ground edge, and the other edges of the both radiating conductors are formed as open edges. Then, a power feeding conductor connected to the power feeding edge and a ground conductor connected to the ground edge are arranged adjacently on the board, and the impedance of the ground conductor is matched with the input impedance of the power feeding conductor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-mounted antenna element used for mobile communication equipment and the like, and a communication device using the same.

[0002]

2. Description of the Related Art A linear antenna element, particularly a λ / 2 antenna element which resonates at λ / 2 of a used frequency, is often used as an antenna element of a mobile communication device.
However, an antenna element composed of a λ / 4 radiation conductor has been used for downsizing the antenna. However, when a λ / 4 monopole antenna is used, there is a problem that an induced current of the antenna affects a radiation pattern. For example, when an induced current flows through a housing that electromagnetically shields a circuit of a communication device, radiation characteristics may be disturbed. Japanese Patent Application Laid-Open No. Hei 5-327527 proposes that a concave portion is provided at a position corresponding to [lambda] / 4 of the working frequency from the antenna feed point to offset the effect of the induced current flowing through the housing. In addition, λ /
It has been proposed to provide a stub 4 to cancel the induced current. However, these means are contradictory to miniaturization.

[0003] Therefore, there is a demand for a surface mount type in which an antenna element of a λ / 4 radiation conductor is provided on the surface of a chip-shaped base, and the base can be provided on a circuit board.

[0004]

However, when a λ / 4 antenna element emits a radio wave, a larger induced current is induced in a circuit board conductor than in a λ / 2 antenna element. Since the induced current induced in the circuit board conductor affects the directivity and resonance frequency of the antenna, there has been a problem that the directivity and resonance frequency of the antenna change depending on the size of the circuit board.

Accordingly, an object of the present invention is to provide an antenna element capable of improving radiation efficiency and realizing a wide band irrespective of the shape of the circuit board conductor, assuming that the excitation in the antenna section is completed.

Another object of the present invention is to provide a communication device equipped with these antenna elements, for example, a communication device mounted as a Bluetooth antenna on a mobile phone, a headphone, a personal computer, a notebook personal computer, a digital camera, or the like. And

In the present invention, the similar λ / 4 radiation conductor is
Another object of the present invention is to provide an antenna element which uses a plurality of antenna elements to achieve impedance matching therebetween, and which can enhance the resonance in the antenna section, and a communication device using the same.

[0008]

An antenna element according to the present invention has two similar radiating conductors provided substantially symmetrically on the surface of a base made of a dielectric material, and one radiating conductor is connected to the other radiating conductor. The near end is a feeding end, the other end of the radiating conductor close to the one radiating conductor is a grounding end, and the other end of both radiating conductors is an open end. Since the two similar radiation conductors are provided symmetrically, the main polarization directions are aligned. In the above, the open end of at least one of the two radiating conductors can be capacitively coupled to the ground conductor via an interval. At this time, a ground conductor that is capacitively coupled to the open end of the radiation conductor via an interval can be provided on the end surface of the base on which the radiation conductor is provided.

In the antenna element according to the present invention, another radiating conductor symmetrically similar to the radiating conductor is provided to match the two radiating conductors, and to facilitate matching between the feeding end and the grounding end of the two radiating conductors. Therefore, the resonance at the antenna part becomes stronger,
The induced current is positively generated in the radiation conductor on the ground side, and radiation characteristics are improved.

[0010] In the antenna element, it is preferable that an impedance adjusting conductor is provided between a ground conductor connected to the ground terminal and the ground terminal. In this case, the impedance can be matched by making the length of the ground conductor longer than the power supply conductor and using that portion as an impedance adjustment conductor, or providing an impedance adjustment conductor extending from the ground end of the radiation conductor on the base. it can. In the present invention,
Since the impedances of the feed end and the ground end are matched together with the radiation impedances of the two radiation conductors, a wider band is achieved.

In the antenna element of the present invention, the two similar radiating conductors may have a meandering shape or a helical shape, and the two radiating conductors are rotationally symmetric about a certain point on the surface of the base. It is preferred that It is considered that by using two rotationally symmetric radiation conductors, the ground conductor becomes longer, and its impedance matches well with the input impedance.

In the antenna element of the present invention, it is preferable that the two radiating conductors are thicker than a conductor at an end that is closer to an end and a conductor that is closer to an end.

Further, according to the present invention, an antenna element in which another radiating conductor is embedded by stacking another dielectric layer on any of the above-described antenna elements can be obtained. Also,
Two sets of antenna elements in which two similar radiating conductors as described above are provided symmetrically with the main polarization directions aligned are formed such that they are superimposed such that their main polarization directions are orthogonal or arranged in a plane. Antenna element.

A communication device according to the present invention has one of the above-described antenna elements mounted on a circuit board, and a circuit board exposed portion is provided on a surface of the circuit board on which the antenna element is mounted. The antenna element is attached to an exposed portion of a circuit board.

A communication device according to the present invention has an antenna element mounted on a circuit board having a circuit board exposed portion on the surface, wherein the antenna element is formed on one surface of a rectangular parallelepiped base made of a dielectric material. On at least two surfaces, there are two similar radiating conductors provided substantially symmetrically, and one radiating conductor has
The other radiation conductor has a feeding end at an end near the other radiation conductor, the other radiation conductor has a ground end at an end near the one radiation conductor, and both radiation conductors have an open end at the other end, and An impedance adjustment conductor is provided between a ground conductor connected to the end and the ground end, and a base surface having no two radiation conductors is mounted on an exposed surface of the circuit board.

In the communication device according to the present invention, the antenna element has a ground conductor capacitively coupled to the open end on the end face of the base body adjacent to the surface of the base body on which the radiation conductor is provided. Can be.

In the communication device of the present invention, the ground conductor of the antenna element may be attached to a floating electrode provided on the exposed surface of the circuit board.

In the communication device of the present invention, the two similar radiating conductors of the antenna element may have a meandering or helical shape, and the two radiating conductors are preferably rotationally symmetric.

Further, in the communication device of the present invention, it is preferable that the folded portion of the radiation conductor of the antenna element is provided so as to be gradually separated from the exposed portion of the circuit board from the feed end and the ground end to the open end.

In the communication device of the present invention, the radiation conductor of the antenna element is separated from the circuit board, so that the influence of grounding can be eliminated.

In the communication device of the present invention, a module substrate in which any of the above-described antenna elements is incorporated in a multilayer ceramic substrate and integrated can be used as a circuit substrate.

In the antenna element and the communication device using the same according to the present invention, the radiation conductor is preferably a λ / 4 radiation conductor. Here, “λ / 4 radiation conductor” means a radiation conductor that resonates at λ / 4 of the working frequency. In the embodiment described below, a λ / 4 radiation conductor will be described.

[0023]

FIG. 1A is a perspective view showing an antenna element 1 according to a first embodiment of the present invention. In this figure, λ / 4 similar to the upper surface 11 of a rectangular parallelepiped base 10 made of a dielectric material is shown.
The radiating conductors 20 and 30 are provided symmetrically with respect to the center plane 12 shown by a two-dot chain line. Although the radiation conductors 20 and 30 are shown as segments in the drawings, they are actually preferably formed continuously by printing.

Since two λ / 4 radiation conductors are provided symmetrically with respect to the plane, the main polarization directions of the radiated radio waves are aligned. An end of the left λ / 4 radiation conductor 20 close to the right λ / 4 radiation conductor 30 is a feeding end 21, which is provided on the front surface 13 of the base 10, and the feeding end 21 is a high-frequency signal source 41. Is connected to the power supply conductor 40 connected to the power supply conductor 40. Λ / on the right
The four radiation conductors 30 have an end near the left λ / 4 radiation conductor 20 as a ground end 31, and the ground end is also provided on the front surface 13. The ground end 31 is connected to the ground conductor 50 and is grounded. I have. The other ends of the λ / 4 radiation conductors 20 and 30 are open ends 22 and 32.

In order to better understand the structure of the antenna element 1, a bottom perspective view of the antenna element 1 shown in FIG.
1B and FIG. 1C is a perspective view of the back side surface 14 of FIG. As can be seen from FIGS. 1A to 1C, the antenna element 1 has the λ / 4 radiation conductor provided only on the upper surface 11, and the power supply end 21 and the ground end 31 are provided close to each other and only on the front surface 13 of the hand. ing. No conductor is provided on the bottom surface 15 and the back side surface 14. The bottom surface 15 having no conductor can be attached to the exposed surface of the circuit board of the communication device. Normally, conductors are provided on the circuit board, but the exposed surface of the circuit board refers to the portion where the circuit conductor is not provided, but it is necessary to connect it to the conductor end of the antenna element. A conductor or the like is a portion that can be provided.

Although the λ / 4 radiation conductor shown in the figure has a meandering shape, it may be helical or straight. The size of the base 10 can be reduced by making it meander-shaped or helical.

According to the configuration of the antenna element 1 described above, since the feed conductor 40 and the ground conductor 50 are provided close to each other, the capacity between the feed conductor and the ground conductor increases. Further, since the open ends 22 and 32 of the λ / 4 radiation conductor are separated, the interaction between them is small, and the antenna element 1 can be represented by an equivalent circuit shown in FIG.

In FIG. 2A, L20 and L30 are inductances of the λ / 4 radiation conductors 20 and 30, respectively, L40 and L30.
L50 is the inductance of the feed conductor 40 and the ground conductor 50, respectively, and C1 and C2 are the capacitance between both λ / 4 radiation conductors and the capacitance between the feed conductor and the ground conductor. Also, R2
0 and R30 indicate the radiation resistance of each λ / 4 radiation conductor. Since both λ / 4 radiation conductors are provided symmetrically, impedance matching between them can be achieved. Feeding end 2
1 and the ground end 31 are provided close to each other on the same substrate surface, so that the capacitances C1 and C2 are increased. By adjusting these positions, good matching of both λ / 4 radiation conductors can be obtained.

Since matching can be easily achieved, when a radio wave is radiated from one λ / 4 radiating conductor, the resonance of both λ / 4 radiating conductors is strengthened, and the other λ / 4 radiating conductor is also induced. Generates current. Therefore, the influence on the circuit on the circuit board is small, and the change in the resonance frequency and the change in the directivity pattern can be reduced.

In FIG. 2A, R0 is a feed end 21 (FIG.
The input impedance to point A in (A) is generally about 5
There is 0Ω. In order to attach an impedance substantially equivalent to the input impedance to the ground conductor 50, FIG.
As shown in the bottom perspective view of (B ′), the ground end 31 is extended, and the impedance adjustment conductor 51 is inserted between the ground end 31 and the ground conductor 50. As a result, an equivalent circuit having an impedance R 'at point B as shown in FIG.
Good impedance matching can be obtained so as to be Ω, and a wider band can be achieved.

FIG. 3 shows the antenna element 2 of the second embodiment. FIG. 3A is a perspective view showing a point 12 a extending from the upper surface 11 of the rectangular parallelepiped base body 10 made of a dielectric material to the inner side surface 14.
Λ / 4 radiation conductor 20 similar to rotational symmetry about the center
a, 30a are provided. The λ / 4 radiation conductor is provided over two adjacent surfaces, but in a state where these two base surfaces are expanded, the two λ / 4 radiation conductors have rotational symmetry about the point 12a. Has become. FIG. 3 (B)
3A is a bottom perspective view in which the bottom surface 15 in FIG. 3A is up and the back side 14 is in the foreground. In FIG. 3C, the top surface 11 is in the top but the back side 14 is in the foreground. FIG. 3A, the right λ of the λ / 4 radiation conductor 20a on the left side.
The end near the / 4 radiation conductor 30a is provided on the front surface 13 of the base 10 as a power supply end 21a, and is connected to the power supply conductor 40. The right λ / 4 radiation conductor 30a is provided on the bottom surface 15 of the base 10 with an end near the left λ / 4 radiation conductor 20a as a ground end 31a.
Grounded.

The other ends of the λ / 4 radiation conductors 20a and 30a are open ends 22a and 32a. The feeding end 21a is provided on the front surface 13 of the hand, and the grounding end 31a is provided on a surface different from the bottom surface 15, but conductors near the center of symmetry of the λ / 4 radiation conductors 20a and 30a are provided close to each other. Since the power supply conductor 40 and the ground conductor 50 are relatively close to each other, the capacitance is large and matching can be achieved. It will be understood that this embodiment also has the equivalent circuit shown in FIG. In this example, the conductor extending from the radiation conductor 30a to the ground end is long, and the impedance adjustment conductor is inserted, so that good impedance matching can be obtained.

The λ / 4 radiation conductors 20a and 30a have a meandering shape and are thicker than the conductors at the ends where the conductor at the center is farther away. Since the current amplitude at the feeding end is large in the λ / 4 radiation conductor and the current amplitude is small at the open end, the loss of the conductor can be reduced by increasing the thickness of the radiation conductor where the current amplitude is large.

FIG. 4 is a perspective view of the third embodiment.
FIG. 4A shows an example in which the antenna element 2 a is mounted on a circuit board 80. The surface of the circuit board 80 is provided with a circuit board exposed portion where the base of the substrate is exposed and the ground electrode is not provided, and the surface of the portion where the antenna element is mounted is shown in an enlarged scale in FIG. And the power supply conductor 40,
A ground conductor 50 and fixed floating electrodes 85 and 85 'are provided. The power supply conductor 40 is supplied with power from the printed wiring on the back surface of the circuit board, and the ground conductor 50 is connected to the board ground plane. The antenna element 2a is almost the same as the antenna element 2 of the second embodiment, except that FIGS.
As shown in (E), the floating electrode 8 of the circuit board 80 is formed.
Additional electrodes 61,6 for soldering to 5,85 '
2 is provided. Note that FIG.
Is a perspective view of the antenna element 2a, and FIG. 4E is a bottom perspective view thereof. The antenna element 2a has a grounded end 31a folded back on the front surface 13, a feeding end 21a, and a grounding conductor 50 and a feeding conductor 40 attached to the circuit board 80, respectively.
Are soldered and additional electrodes 61, 6
Since the antenna element 2a is soldered to the floating electrodes 85 and 85 ', the antenna element 2a is firmly attached to the circuit board 80. Even if the antenna element is used for a communication device such as a mobile communication device, it is possible to prevent the antenna element from being loosened or falling off during handling.

FIG. 4C shows a modification of a part of the circuit board shown in an enlarged view in FIG. 4B. FIG.
4C, the ground conductor 50 'is connected to the ground conductor 5 in FIG.
0, the inner side surface 1 of the antenna element 2a
It reaches up to 4. Since the tip of the ground conductor 50 'can be soldered to the λ / 4 radiation conductor 30a on the back side, the base 10 of the antenna element 2a is
And the rear side surface 14 can be mounted on the substrate 80 to improve the vibration resistance. Further, the elongated ground conductor 50 '
Work as an impedance adjusting conductor so that good matching with the power supply side can be obtained.

As is clear from FIG. 4A, the antenna element 2a has a surface having no two λ / 4 radiation conductors, that is, the bottom surface 15 is attached to the exposed surface of the circuit board 80, and the two The upper surface 11 and the rear surface 14 having the / 4 radiation conductor are separated from the circuit conductor of the circuit board 80. When the λ / 4 radiation conductor is separated from the circuit conductor and far from the ground, the influence of the ground is eliminated, and the radiation efficiency is improved.

FIG. 5 is a perspective view of a circuit board 80a to which the antenna element 2a according to another embodiment is attached. In this example, λ / is parallel to the longitudinal direction of the circuit board 80a.
Four radiation conductors are attached so as to face. Other points are the same as those shown in FIG.

FIG. 6 shows the circuit board 80b and the antenna element 2b.
2 is a developed perspective view before assembling. The antenna element 2b is basically the same as the antenna element 2a,
The open ends 22a and 32a of the two λ / 4 radiation conductors are respectively provided on the end faces 16 and 17 via the gaps 23b and 33b.
4b and 34b are provided and are capacitively coupled to the ground conductor. Since the large capacity is provided at the open end of the λ / 4 radiation conductor, the radiation conductor can be shortened. Further, the floating electrodes 85, 8 of FIG.
Ground electrodes 85b and 85b 'are provided instead of 5', and the ground conductors 24b and 34b of the antenna element 2b can be soldered to the ground electrodes 85b and 85b ', respectively, further improving the vibration resistance. I do.

FIG. 7 is a perspective view of still another embodiment, in which FIG. 7A shows the antenna element 3 mounted on a circuit board 80, and FIG. FIG.

The λ / 4 radiation conductors 20c, 30 of this embodiment
c is the top surface 11 and the back surface 1 of the rectangular parallelepiped base made of a dielectric material.
Only 4 are provided in a meandering manner. In addition, the ridge line 1 of the base 10 at a position away from the exposed portion of the circuit board 80
8 (ridge line between the upper surface 11 and the back side surface 14)
Four radiating conductors are arranged, and the folded portion of the λ / 4 radiating conductor is located away from the ridge at the feeding end and the ground end of each λ / 4 radiating conductor, and the ridge is formed at the other end of the λ / 4 radiating conductor. It is provided so as to approach. That is, the folded portion of the radiation conductor is provided so as to gradually separate from the exposed surface of the circuit board as going from the feeding end and the ground end to the open end of each radiation conductor. This is to improve the radiation efficiency by moving the antenna tip, which is most affected by the ground, away from the ground.

A modification of the antenna element of the present invention is shown in FIGS.
0 is shown. The antenna element 4 shown in FIG. 8 is obtained by forming the antenna element 1 shown in FIG. 1 on a rectangular parallelepiped base 10 made of a dielectric,
0 ′ are superposed, and two dielectric substrates 10,
A λ / 4 radiation conductor is embedded between 10 ′. By embedding the antenna element between the dielectrics as described above, the electrical length of the radiation conductor can be shortened, and the antenna can be downsized.

The antenna element 5 shown in FIG. 9 has two λ / 4 radiation conductors 20b and 30b symmetrically provided on the surface of a rectangular parallelepiped base 10a made of a dielectric material with the main polarization directions aligned. 5 ′ and an antenna element 5 ″ in which two λ / 4 radiation conductors 20b ′ and 30b ′ are symmetrically provided on the surface of a similar base 10a ′ with their main polarization directions aligned. The antenna element 5 "is formed so as to be superposed in a multilayer substrate such that the main polarization directions are orthogonal to each other. FIG.
The arrows in (A) and (B) are the main polarization directions of the respective antenna elements 5 'and 5 ". Fig. 9 (C) in which these are superimposed is shown in a transmission diagram. By using orthogonal antenna elements, both vertical and horizontal polarized waves can be efficiently received, so that efficient communication can be performed regardless of the direction of the device used. The two antenna elements 5 'and 5 "may be arranged side by side.

FIG. 10 shows a multi-layer ceramic substrate 90 in which an antenna element (for example, antenna element 4 shown in FIG. 8) is integrated. The multilayer ceramic substrate 90 is a module substrate, on which a chip component 91 such as a bypass capacitor, an RF-IC 92, and the like are attached, and a balun and a filter can be configured by a multilayer conductor. Since the multilayer ceramic substrate 90 and the antenna element 4 can be manufactured collectively, the manufacturing cost can be reduced, and the positional accuracy of the antenna can be improved, so that the frequency variation due to the mounting variation can be reduced.

Experiment An antenna element 2 shown in FIG. 3 was manufactured, and its reflection loss and voltage standing wave ratio (VSWR) were measured. Relative permittivity εr
: 40, tan δ: 3.0m width using a dielectric material of 0.0002
m, a length of 13.4 mm, and a thickness of 1.5 mm. As shown in an exploded view of FIG.
a and 30a. The width of each conductor is 0.40m from outside
m, 0.45 mm, 0.50 mm, 0.55 mm,.
60 mm, 0.65 mm, 0.70 mm, the height of the folded portion (width in the vertical direction in the drawing) is 0.40 mm from the outside,
0.45mm, 0.50mm, 0.55mm, 0.60
mm and 0.65 mm. 0.4 mm gap width between conductors, 0.9 m center spacing between λ / 4 radiation conductors
m. The antenna element 2 was mounted at a distance of 3 mm from the ground exposed on the circuit board. Meander-shaped λ / 4
The characteristics were measured in the case where the two radiation conductors 20a and 30a were rotationally symmetric about the point 12a, and in the case where the two radiation conductors were plane symmetric about the cutting plane passing through 12a.

FIG. 12 shows the frequency characteristics of the reflection loss, and FIG. 13 shows the frequency characteristics of the voltage standing wave ratio (VSWR). As is clear from these graphs, in the vicinity of 2.44 GHz, the antenna element of the present invention has a frequency band in which the return loss is −6 dB or less (VSWR 3% or less) at 155 MHz.
As described above, the band is further widened to 368 MHz in the rotationally symmetric λ / 4 radiation conductor. In addition, the rotationally symmetric λ /
In the case of four radiation conductors, the reflection loss is −9.54 dB or less (VS
(WR 2% or less) is 226 MHz.

[0046]

As described above in detail, the antenna element in which the radiating conductors are symmetrically arranged as in the present invention has a small size, good matching, radiation efficiency can be improved, and a wide band can be realized.

[Brief description of the drawings]

1 (A), 1 (B), 1 (B '), and 1 (C) are perspective views of an antenna element according to a first embodiment of the present invention.

FIGS. 2A and 2B are equivalent circuits of the antenna element of the present invention.

FIGS. 3A, 3B, and 3C are perspective views of an antenna element according to a second embodiment of the present invention.

4A is a perspective view of an antenna element according to a third embodiment of the present invention mounted on a circuit board, FIG. 4B is a partially enlarged perspective view of the circuit board, and FIG. (D) and (E) are perspective views of an antenna element according to a third embodiment of the present invention.

FIG. 5 is a perspective view of an antenna element according to another embodiment mounted on a circuit board.

FIG. 6 is an exploded perspective view before the antenna element is mounted on the circuit board.

FIGS. 7A and 7B are perspective views of an antenna element according to still another embodiment of the present invention.

FIG. 8 is a transparent perspective view showing a modification of the antenna element of the present invention.

FIG. 9 is another modification of the antenna element of the present invention;
(A) and (B) are plan views of the antenna element of each layer.
(C) is an overlapped transmission plan view.

FIG. 10 is a perspective view of still another modification of the antenna element of the present invention.

FIG. 11 is a developed view of an antenna element structure used for an experiment in the present invention.

FIG. 12 is a graph showing frequency characteristics of reflection loss of the antenna element of the present invention.

FIG. 13 is a graph showing a frequency characteristic of a voltage standing wave ratio of the antenna element of the present invention.

[Explanation of symbols]

1,2,2a, 2b, 3,4,5,5 ', 5 "Antenna element 10,10', 10a, 10a 'Base 11 Top surface 12 Center surface 12a Point 13 Hand front surface 14 Back surface 15 Bottom surface 16,17 End surface 18 Ridges 20, 20a, 20b, 20b ', 20c, 30, 30
a, 30b, 30b ', 30c
λ / 4 radiation conductor 21, 21a Feed end 31, 31a Ground end 22, 22a, 32, 32a Open end 23b, 33b Interval 24b, 34b, 50, 50 'Ground conductor 40 Feed conductor 41 High frequency signal source 51 Impedance adjusting conductor 61 , 62 electrode 80, 80a, 80b circuit board 85b, 85b 'ground electrode 85, 85' floating electrode 90 multilayer ceramic substrate 91 chip component 92 RF-IC

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Eriko Takeda 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd. (72) Hiroshi Aoyama 5200 Mikajiri, Kumagaya, Saitama Prefecture Within the Electronics Research Laboratory (72) Inventor Keiko Kikuchi 5200, Mitsugashiri, Kumagaya-shi, Saitama F-term within the Advanced Electronics Research Laboratory, Hitachi Metals, Ltd. FJ-term (Reference)

Claims (19)

[Claims] 1. A radiating conductor having two substantially similar radiating conductors provided substantially symmetrically on a surface of a base made of a dielectric material, one end of one radiating conductor close to the other radiating conductor being a feeding end, and the other radiating end being a radiation end. An antenna element, wherein an end of the conductor near the one radiation conductor is a ground end, and the other ends of both radiation conductors are open ends. 2. The antenna element according to claim 1, wherein an open end of at least one of the two radiation conductors is capacitively coupled to a ground conductor via a space. 3. A ground conductor, which is capacitively coupled to an open end of the radiation conductor via an interval on an end face of the base body adjacent to a surface on which the radiation conductor is provided. Antenna element. 4. The antenna element according to claim 1, wherein an impedance adjusting conductor is provided between a ground conductor connected to the ground terminal and the ground terminal. 5. The antenna element according to claim 1, wherein the two similar radiation conductors have a meandering shape or a helical shape. 6. The antenna element according to claim 5, wherein said two radiation conductors are rotationally symmetric. 7. The antenna element according to claim 1, wherein the two radiating conductors are thicker at ends closer to each other than ends distant from each other. 8. An antenna element, wherein another dielectric layer is laminated on the antenna element according to claim 1, and the two radiation conductors are embedded. 9. The two sets of antenna elements according to claim 1, wherein the two similar radiation conductors are provided symmetrically with the main polarization direction being aligned. An antenna element characterized by being formed in an overlapping manner. 10. The antenna element according to claim 1, wherein the radiation conductor is a λ / 4 radiation conductor. 11. A communication device having the antenna element according to claim 1 attached to a circuit board, wherein a circuit board exposed portion is provided on a surface of the circuit board to which the antenna element is attached, and A communication device comprising the antenna element mounted on an exposed portion. 12. A communication device in which an antenna element is mounted on a circuit board having a circuit board exposed portion on a surface, wherein the antenna element has one or at least two surfaces of a rectangular parallelepiped base made of a dielectric material. On the upper side, there are two similar radiating conductors provided substantially symmetrically, one radiating conductor has a feeding end at an end close to the other radiating conductor, and the other radiating conductor is close to the one radiating conductor. The radiating conductor has a grounded end, and both radiation conductors have an open end at the other end, and an impedance adjusting conductor is provided between the grounded end connected to the grounded end and the grounded end. A communication device, wherein a base surface having no surface is mounted on an exposed surface of a circuit board. 13. The antenna element according to claim 1, further comprising a ground conductor that is capacitively coupled to the open end via an interval on an end face of the base body adjacent to a surface of the base body on which the radiation conductor is provided. 13. The communication device according to claim 12, wherein 14. The communication device according to claim 12, wherein a ground conductor of the antenna element is attached to a floating electrode provided on the exposed portion of the circuit board. 15. The communication device according to claim 12, wherein the two similar radiation conductors of the antenna element have a meandering shape or a helical shape. 16. The communication device according to claim 15, wherein said two radiation conductors are rotationally symmetric. 17. The antenna device according to claim 17, wherein the folded portion of the radiation conductor of the antenna element is provided so as to gradually move away from the exposed portion of the circuit board on the board from the feed end and the ground end to the open end. Item 17. The communication device according to Item 15 or 16. 18. The communication device according to claim 11, wherein the circuit board is a module board in which an antenna element is integrated into a multilayer ceramic board. 19. The communication device according to claim 11, wherein said radiation conductor is a λ / 4 radiation conductor.