JP2000332521A - Antenna element and radio communication device using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To actualize reduction, high radiation efficiency, and radiation gain characteristic by arranging a 1st spiral radiation electrode on an insulating substrate and providing a 2nd radiation electrode between a feed electrode and the 1st radiation electrode. SOLUTION: The 1st spiral radiation electrode 2 is arranged on the external surface of the insulating substrate 1, the 2nd radiation electrode 3 is provided at least on the top surface of the insulating substrate 1, and the feed electrode 4 is provided on the end surface. The feed electrode 4 and 2nd radiation electrode 3 are connected, but the 1st radiation electrode 2 has a gap (c) with the 2nd radiation electrode. The insulating substrate 1 is preferably a dielectric material such as dielectric ceramic, low-loss glass epoxy, and 'Teflon (R)'. The radiation electrode 2, radiation electrode 3, and feed electrode 4 are formed by properly selecting a method out of printing, vapor deposition, and plating. As electrode materials, a metal material with low electric resistance such as Au, Pt, Ag, and Cu or alloy consisting principally of them is usable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna element, and more particularly to a small antenna element used for a microwave radio communication device such as a mobile phone and a wireless LAN (local area network).

[0002]

2. Description of the Related Art In microwave radio communication equipment, especially mobile communication equipment such as mobile phones, a monopole antenna is used as an antenna element, and a radiation electrode is spirally arranged on the surface of a base made of a dielectric material in order to reduce the size and weight. Such a helical antenna is generally used. These antennas are described in detail in the Antenna Engineering Handbook (edited by the Institute of Electronics, Information and Communication Engineers, pages 50 to 59, published by Ohmsha).

[0003] As a helical antenna element that is put into practical use, an element in which a helical conductive wire is wound around an insulator to form a radiation electrode is known. For example, FIG. 12 shows a schematic structure of a helical antenna element in which electrodes are formed by thick film printing. The radiation electrode 2 and the power supply electrode 4 provided on the outer surface of the insulating substrate 1 are formed by applying and firing a conductive paste. On the other hand, the laminated helical antenna described in Japanese Patent Application Laid-Open No. 9-51221 is an antenna element having a chip structure manufactured by applying a lamination technology, in which a conductor pattern arranged between insulating layers is internally connected to form a coiled radiation electrode. Is what you get. In terms of structure, the radiation electrode is in a buried state that is not exposed on the surface of the insulator.

In FIG. 12, the wavelength of the current flowing through the radiation electrode 2 on the insulating substrate 1 is reduced in proportion to the relative dielectric constant of the insulating substrate 1 (wavelength shortening effect). Even if the line length is shortened, the same antenna characteristics can be obtained. Therefore, the helical antenna in which the radiation electrode is arranged on the surface of the insulating substrate or in the insulating material is a small antenna utilizing this wavelength shortening effect. Furthermore, in comparison with the monopole antenna, the helical antenna can substantially shorten the antenna length by the spiral radiation electrode structure in combination with the wavelength shortening effect, and can manufacture an antenna element having a low height. At present, a helical antenna is one of the antennas frequently used in the field of wireless communication devices such as mobile phones.

[0005]

However, when the helical antenna is reduced in size according to the prior art, there are the following problems. That is, when the dielectric constant of the insulating substrate is increased, the radiation resistance is reduced, and the radiation efficiency and the gain of the antenna are reduced, so that a practical antenna element cannot be obtained. In addition, even if the current at the antenna feed point is increased to compensate for the shortage of radiated power due to the decrease in radiation resistance, it will contribute to the increase of electromagnetic waves radiated in the air, simply increasing the loss of the transmission circuit. Did not. Thus, the prior art which impairs the essential antenna characteristics is not suitable for downsizing the helical antenna.

Further, when the helical antenna is incorporated into a portable communication device and actually operated, a current due to electromagnetic waves radiated from the antenna is induced in a conductor portion of a housing of the communication device or a circuit board, and this conductor portion is apparently observed. Operates as part of the upper antenna. The characteristics of the helical antenna are susceptible to the surroundings such as the conductors and the shape and layout of the housing and circuit board, or the environment in which the communication equipment is used. For this reason, impedance mismatch at the antenna feed point and variations in radiation directivity occur. For example, stable communication performance cannot be obtained.
There was an implementation problem.

To solve the above technical problem, a method of increasing the radiation efficiency and gain by extending the line length of the radiation electrode from about 1/4 wavelength to about 1/2 wavelength of the radiated electromagnetic wave has been conventionally adopted. Was. However, the disadvantage of this method is that the impedance on the power supply side of the radiation electrode increases and causes a mismatch with the impedance on the transmission circuit side, so that an impedance matching circuit needs to be inserted. Insertion of the impedance matching circuit at the antenna feeding point causes the transmission circuit to be complicated and the circuit scale to be increased. Further, considering that the length of the antenna element is long, this technique is not suitable for miniaturizing communication devices including the antenna.

The present invention has been embodied on the basis of a technical idea conceived in order to solve the above-mentioned problems of the prior art, and it has been considered that miniaturization of the antenna and improvement of the characteristics cannot be achieved at the same time. I was However, the embodiment of the present invention provides an antenna element having a high radiation efficiency and a high radiation gain characteristic while reducing the size of the antenna.

[0009]

According to a first aspect of the present invention, a spiral first radiating electrode is provided on an insulating substrate, and a second radiating electrode is further provided between a feeding electrode and the first radiating electrode. It is an antenna element of a structure. Conventionally, the power supply electrode is directly connected to the spiral radiation electrode. However, the present invention has conceived a configuration in which a second radiation electrode is newly installed in order to separate the spiral first radiation electrode from the feed electrode or the ground conductor. The inventors have found that the radiation efficiency and directivity can be greatly improved by separating the first radiation electrode from the power supply electrode, and completed the invention. Arranging the first radiation electrode at a required distance from the power supply electrode means isolating the first radiation electrode from a conductor arranged near the radiation electrode such as a ground conductor. It is specified. This is the gist of the present invention, and there is no known document that discloses such a technique.

Now, a preferred range as a separation distance between the first radiation electrode and the feeding electrode will be described. First, the physical meaning of the separation distance is considered as follows. That is, a sufficient effect cannot be obtained in a short distance region, and when the optimum length is exceeded, not only does the antenna performance deteriorate,
This leads to an increase in the size of the antenna element, and the effect of the invention cannot be obtained. In the study of the separation distance, the range was specified in advance by simulation, and further verified by experiment. First, a simulation calculation model will be described.

In FIG. 8, the antenna element 10 is arranged on the surface of the circuit board 5. The antenna element 10 includes an insulating substrate 1 and a first radiation electrode 2 spirally arranged.
And the second radiation electrode 3, and the microstrip line 7 is a power supply line for supplying a signal to the second radiation electrode 3. As shown in the figure, a ground conductor 8 is provided on the back surface of the circuit board 5 at a position indicated by oblique lines. The physical properties used in the simulation, the dimensions of each part, and the like were used in accordance with actual values, and boundary conditions and the like were set so as to be as close to the real thing as possible.

Next, simulation results will be described. 9, the horizontal axis represents the line length L of the second radiation electrode, which is the length described in FIG. The return loss (indicated by a black circle) on the vertical axis is a parameter indicating the degree of the reflected wave from the antenna, and a performance of -10 dB or less is a practical reference. The return loss characteristic shown in FIG. 8 becomes a characteristic curve that decreases to the right as L increases, and the return loss can be reduced to −10 dB or less from around 3 mm. On the other hand, the antenna gain characteristic (○) has a tendency opposite to the return loss characteristic, and becomes a characteristic curve that rises to the right as L increases, and the antenna gain improves as L increases. 0 to
The characteristic improvement is remarkable up to around 1.5 mm, and after passing this point, it reaches the saturation region via the proportional region. Therefore, it is sufficient that L is about 1.5 mm or more,
It is necessary to consider the trade-off with miniaturization.

The simulation results described above are shown in FIG.
A qualitative explanation will be given using an equivalent circuit of 0. This equivalent circuit
Then, R is the radiation resistance, C_SIs the first radiation electrode and the ground conductor
The parasitic capacitance between the first and second radiation electrodes
Inductance is L ₁, L₂And Show
So, R, C_SAnd L₁, L₂Are connected in parallel
It can be regarded as continued. In addition, the transmission circuit
Voltage source e is L₁, L₂Is inserted in series. In an equivalent circuit
Is the power of the electromagnetic wave radiated from the antenna into space, R
The product of the square of the flowing current Ir and R, that is, (Ir)²By R
Is displayed. The higher this value, the higher the radiation efficiency
It is an antenna.

[0014] Now, the line length L of the second radiation electrode is long is that away from the first radiation electrode 2 is grounded conductors 8 As is apparent from FIG. 8, reduced C _S in the equivalent circuit was considered to be L ₂ is increased in the opposite. As a result, the ratio of current shunted to the parallel circuit of the R and C _S is changed. In other words, decreases the current Ic flowing through the C _S, Ir increases conversely. However, there are some reduction of Ir by the current suppressing effect due to an increase of L _2, for better incremental increases, leading to improvement of the antenna gain increases the radiated power. On the other hand, return loss is considered as follows. Line length L and the inductance L ₂ of the second radiation electrode for a proportional relationship, L ₂ larger the L becomes longer increases. Therefore, the increase in L ₂ is that the impedance is large, it is the effect of suppressing the reflections from the antenna, matching return loss characteristics shown in FIG.

The second invention is an antenna element characterized in that the first radiation electrode and the second radiation electrode are electrostatically coupled. That is, the first radiation electrode and the second radiation electrode are not physically connected, but are electrically connected in an electric circuit. In order to realize the electrostatic coupling effect, a capacitor is formed between the first radiating electrode and the second radiating electrode, and specifically, it is obtained by arranging the respective electrodes adjacently or facing each other. Furthermore, the capacitance required for electrostatic coupling can be obtained by appropriately selecting the gap between the first radiation electrode and the second radiation electrode, the material of the insulator, and the like. In the present invention, it is assumed that the radiation electrode is formed on the insulator surface. Therefore, a configuration in which the first radiation electrode and the second radiation electrode are arranged adjacent to each other will be described in the embodiment. Since a capacitor may be formed between the second radiation electrodes, not only two-dimensional but also three-dimensional electrode arrangement is possible. In the present invention, the method of forming the capacitor between the electrodes does not impose any restrictions or regulations, but utilizes the electrostatic coupling action between the first radiation electrode and the second radiation electrode. In some embodiments,
It can be said that this is an implementation of the present invention.

Forming a capacitor between the first radiation electrode and the second radiation electrode is equivalent to the equivalent capacitor C _1-2.
Can be regarded as being inserted in series into L ₁ and L ₂ . This relationship is shown in the equivalent circuit of FIG. The difference from the equivalent circuit of FIG. 10 is that C _1-2 is inserted in series with L ₁ , L ₂ and e. _C1-2 indicates a capacitor formed between the first and second radiation electrodes, and its capacitance is variable. Since C _1-2 is connected in series with L ₁ and L ₂ , C 1
Reactance by _1-2 can be suppressed or canceled increment of reactance by L _2, suppressing an increase in impedance. This suppression effect contributes to the improvement of the antenna characteristics. Further, if the adjustment range of _C1-2 is expanded, an impedance matching function can be obtained, so that there is no need to provide a special matching circuit, and this configuration is effective for saving space. The present invention in which the impedance matching circuit is built in the antenna element has a novel configuration that is not disclosed in the related art.

Further, the second radiating electrode of the present invention may have any one of a linear shape, a broken shape, and a spiral shape, or may have a combined shape. First
Considering that the separation of the radiation electrode and the feeding electrode is the gist of the present invention, the above selection can be easily understood. Further, the insulating substrate on which the electrodes are formed is preferably rectangular or columnar. The characteristics are not affected by the shape, but the dimensional ratio described below is a problem. Therefore, the shape of the insulating substrate is an optional design item that can be determined in consideration of advantages in manufacturing. For example, when a substantially cylindrical substrate is used as the insulating substrate, a plane parallel to the central axis is formed on the cylindrical surface. A preferable dimensional ratio of the insulating substrate is 0.8 ≦ W / W if the width W, the height h, and the length 1 are given.
h ≦ 1.2.

Next, the electrodes will be described. First, there is a desirable range for the line widths of the first radiation electrode and the second radiation electrode. That is, assuming that the width of the first radiation electrode is a and the width of the second radiation electrode is b, the ratio b / a is 1.5 to 20. Further, the capacitance C _1-2 generated between the first radiation electrode and the second radiation electrode is approximately expressed by the following equation.

[0019]

(Equation 1)

Here, in the above equation, ε is the effective permittivity around the radiation electrode made of the material constituting the insulating substrate. As can be easily understood from this equation, to increase _C1-2 , it is possible to increase the line width b or reduce the inter-electrode distance c. However, it is necessary to increase the precision of forming c required in the manufacturing process as c becomes narrower. Therefore, it is more advantageous to select the line width b instead. Further, the line width b of the second radiation electrode is preferably formed wider than the line width a of the first radiation electrode.
/ A is preferably set to 1.5 to 20. When the ratio b / a is less than 1.5, it is not sufficient to reduce the inductance L2 of the _second radiation electrode. On the other hand, when the ratio b / a exceeds 20, the insulating substrate becomes large. It is.

As described above, since the first radiation electrode is substantially extended by the addition of the second radiation electrode, the radiation resistance of the antenna element of the present invention can be increased, Even when the element is downsized, a decrease in radiation efficiency or gain can be suppressed. Further, since the first radiation electrode and the second radiation electrode are electrically coupled via the capacitance, the capacitance and the inductance of the radiation electrode are connected in series in an equivalent circuit, and As a result, the inductance component generated by the second radiation electrode is canceled, so that the impedance mismatch at the antenna feeding point is eliminated, and an antenna element with a small reflection loss at the feeding point can be obtained. In addition, the present invention is applied to a wireless communication device such as a mobile phone which operates effectively by using any of the above-described antenna elements.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The antenna element according to the present invention will be described in detail below. FIG. 1 is a perspective view of an antenna element according to the present invention. The antenna element 10 includes the insulating substrate 1
A first radiating electrode 2 provided on the outer surface of the substrate, a second radiating electrode 3 provided on at least the upper surface of the insulating substrate 1, and a feed electrode 4 provided on the end face. As shown in the drawing, the feed electrode 4 and the second radiation electrode 3 are connected, but the first radiation electrode 2 is arranged at a distance of c from the second radiation electrode. FIG. 11 shows this state as an equivalent circuit. However, the case where the first radiation electrode and the second radiation electrode in FIG. 10 are physically connected is also an embodiment of the present invention. .

The insulating substrate to be used is made of barium titanate, calcium titanate, calcium zirconate, lead titanate, lead zirconate titanate in consideration of the characteristics of the antenna.
Dielectric ceramics such as alumina and low-loss dielectric materials such as glass epoxy and Teflon are suitable. But,
As long as the material has a frequency band up to 1 GHz, a soft magnetic material having a relative permeability of less than 10 such as NiZn ferrite can be used.

The radiating electrode and the feeding electrode are printed,
It is formed by appropriately selecting from a method such as vapor deposition or plating. As the electrode material, a metal material having low electric resistance such as Au, Pt, Ag, Cu, or an alloy containing these as a main component can be used. Further, as for the connection between the electrodes, electrodes are formed inside the insulating substrate by a lamination technique used for manufacturing a chip capacitor or the like, and electrically connected by at least one or more conductor lines formed on the outer surface of the insulating substrate. The connection can simplify the configuration.

FIG. 2 shows a circuit board on which the antenna element is mounted. Since the transmission power from the first and second radiation electrodes is absorbed by the ground conductor 8 of the circuit board 5, the radiation efficiency, the reduction of the gain, or the disturbance of the radiation directivity are eliminated.
In this structure, a microstrip line 7 is provided on a circuit board 5 on which an antenna element is fixed, and a ground conductor 8 is provided on a part of the back surface. When an antenna is provided separately from the main circuit board and connected by a coaxial line, in order to make the radiation directivity in a plane orthogonal to the longitudinal direction of the antenna element as uniform as possible, as shown in FIG. The antenna element is arranged on the central axis of the circuit board 5 and the pattern of the ground conductor 8 is provided so as to be symmetrical with respect to the central axis of the circuit board 5.

[0026]

(Example 1) In FIG. 1, a powder of a dielectric material composed of calcium zirconate was subjected to pressure molding and sintering, followed by cutting to obtain a width of 3 mm, a height of 3 mm and a length of 1 mm.
A 5 mm rectangular parallelepiped insulating substrate 1 was produced. Using a paste material mainly composed of Ag, a spiral conductive pattern of approximately three turns was printed on the outer surface of the insulating substrate to form a first radiation electrode. Further, a linear second radiation electrode was printed. During this manufacturing process, the first radiation electrode and the second radiation electrode are adjusted so as to have a gap (distance between the radiation electrodes) having a width c = 0.5 mm between the first radiation electrode and the second radiation electrode. Consideration was made so that specified electrostatic capacitance coupling with the electrodes could be achieved.

Further, in order to connect the second radiation electrode and the power supply electrode, an Ag paste was used. After the printing of these electrodes was completed, the electrode was subjected to a baking process at 850 ° C. to bake on an insulating substrate. The obtained antenna element is 2.5 GH
An antenna element for a z-band wireless LAN. When the dimensions of each part after baking are measured, the line width a of the first radiation electrode
Has a thickness of 0.5 mm and a thickness of 10 μm. On the other hand, the line width b of the second radiation electrode was processed to 3 mm, 9 mm in length, and 10 μm in thickness.

The antenna element thus manufactured is
25mm wide and 30m long mainly composed of glass epoxy
It was mounted on a circuit board for evaluation having a thickness of 1 mm and a thickness of 1 mm. A coaxial terminal is provided at one end of this substrate, and this terminal and a feed electrode of the antenna element are formed on a circuit board for evaluation.
m) was fixed by soldering.

After soldering the feeding electrode of the prototyped antenna element to the evaluation circuit board, the end of the radiating electrode was trimmed to 50Ω while measuring the impedance Z _O at the feeding point of the antenna. Tweaked the distance. As a result of making Z _O approximately equal to 50Ω, the propagation center frequency becomes 2.5 GHz, and the voltage standing wave ratio (VSWR)
Under the condition (2), a frequency bandwidth of 100 MHz was obtained.

The antenna element for the prototype wireless LAN is VS
2.48 under the condition that WR (standing voltage wave ratio) is 2 or less
A frequency bandwidth of 4 GHz ± 13 MHz is required,
The antenna element according to the present invention has a sufficient frequency bandwidth characteristic. In addition, during Z _O adjustment, as the gap between the first radiation electrode and the second radiation electrode increases, the capacitance formed between the two electrodes decreases, so that the propagation frequency of the antenna element increases. The frequency variation was 1/10 or less of the required frequency bandwidth for the wireless LAN, and it was proved that there was sufficient margin, and the influence of the adjustment was negligible.

As a comparative example, a helical antenna element having a conventional configuration shown in FIG. 12 was manufactured. This antenna element uses the same dielectric material as in the first embodiment, and has the same dimensions and the same manufacturing method. The characteristics of the prototype antenna element described above were evaluated. The measurement items are radiation gain and radiation directivity in an anechoic chamber. First, the radiation gain is measured by measuring the radiation power from a test antenna element when a signal of 2.5 GHz is supplied to the antenna element via a coaxial cable connected to a signal generator on an evaluation circuit board on which the antenna element is mounted.
Antenna power was received by a horn antenna provided 3 m away from the antenna under test, and input to a spectrum analyzer via a coaxial cable. Next, a half-wavelength dipole antenna with a known gain characteristic (propagation frequency 2.5 GHz,
(Antenna length 60mm)
The radiation gain was determined from a relative comparison with the received power of the antenna element under test.

The radiation directivity measures the received power while fixing the antenna element to be tested on a rotating table when measuring the radiation gain, and rotating the table and the antenna element from an angle of 0 ° to 360 ° in a horizontal plane. In this way, the gain distribution in the horizontal plane was measured. FIG. 7 shows a comparison of the directional characteristics of the antenna element according to the present invention and the conventional antenna element.
This measurement result is expressed as a relative gain (unit: dBd) when the antenna gain is compared with a half-wavelength dipole antenna (maximum gain: 2.15 dBi). From the measurement results, the maximum value of the radiation gain of the antenna element of the present invention is +
It is understood that the average value is improved by 2 dB and the average value is increased by +6 dB, and the same gain can be obtained as compared with the half-wave dipole antenna. In addition, the directivity variation in the horizontal plane was reduced as compared with the conventional antenna element, and a performance almost close to non-directionality was obtained.

Embodiment 2 As another embodiment of the present invention, an antenna element shown in FIG. In this antenna element, the second radiation electrode 3 is formed in a zigzag shape, and the effect of the shape of the second radiation electrode is examined. The material and electrode dimensions of the insulating substrate are exactly the same as those of the first embodiment, and the line width b is 1 mm, the total length of the central part is 15 mm, and the thickness is 10 μm for the second radiation electrode 2. When the same characteristic evaluation as in Example 1 was performed, characteristics were obtained at which no significant difference from Example 1 was recognized, and it is considered that the influence of the shape of the second radiation electrode can be ignored.

(Embodiment 3) The prototype antenna element described above was mounted on a wireless communication apparatus, and the communication range was measured. As described above, it has been confirmed that the antenna element according to the present invention improves the antenna gain, increases the communication range by approximately 1.2 times compared to the conventional antenna element, and can significantly reduce the data transmission error at the same distance. did. Similar results were obtained for the antenna elements shown in FIGS. 5 and 6, thus confirming the effectiveness of the present invention.

[0035]

As is apparent from the above description, the present invention can reduce the size of the antenna element, and can suppress a decrease in gain and a variation in directivity due to the reduction in size. Further, it is possible to provide an antenna element having a high frequency band and a small frequency fluctuation. In addition, when the antenna element according to the present invention is incorporated in a wireless communication device, additional effects of improving the reliability of the communication device, such as increasing the communication range and reducing transmission errors, can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view of an antenna element according to one embodiment of the present invention.

FIG. 2 is a circuit board on which an antenna element is mounted.

FIG. 3 is a layout view in which the antenna element according to the present invention is mounted on a circuit board.

FIG. 4 is a perspective view of an antenna element according to another embodiment of the present invention.

FIG. 5 is a perspective view of an antenna element according to another embodiment of the present invention.

FIG. 6 is a perspective view of an antenna element according to another embodiment of the present invention.

FIG. 7 shows radiation directivity characteristics of the present invention and a conventional helical antenna.

FIG. 8 is a calculation model for simulation.

FIG. 9 shows return loss and gain characteristics of an antenna with respect to the length of a radiation electrode line according to the present invention.

FIG. 10 is an equivalent circuit diagram of the first invention.

FIG. 11 is an equivalent circuit diagram of the second invention.

FIG. 12 is a perspective view of a conventional helical antenna.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 1st radiation electrode, 3 2nd radiation electrode, 4 feed electrode, 5 circuit board, 6 feed point, 7 microstrip line, 8 ground conductor, 10 antenna element.

Claims (12)

[Claims] 1. An antenna element in which a radiation electrode and a feed electrode are disposed on an insulating substrate, wherein the radiation electrode electrically connects the spiral first radiation electrode and the first radiation electrode and the feed electrode. An antenna element comprising a second radiation electrode having a function of connecting. 2. The antenna element according to claim 1, wherein the first radiating electrode and the second radiating electrode are arranged adjacent to each other so as to be capable of electrostatic coupling. 3. The method according to claim 1, wherein
The antenna element according to claim 2, wherein the second radiation electrode has a function of separating the first radiation electrode from a feed electrode. 4. The antenna element according to claim 1, wherein said insulating substrate is provided with impedance matching means. 5. The antenna element according to claim 1, wherein a part or all of the second radiation electrode is linear, zigzag, or spiral. 6. The structure according to claim 1, wherein the width of the insulating substrate is W and the height is h, 0.8 ≦ W /
An antenna element having a cross section of h ≦ 1.2. 7. The antenna element according to claim 1, wherein the insulating substrate is formed in a columnar shape, and has at least one surface parallel to a central axis. 8. The antenna element according to claim 1, wherein the first and second radiation electrodes are partially or entirely covered with an insulator. 9. The method according to claim 1, wherein the width of the first radiation electrode is a and the width of the second radiation electrode is b, b / a is selected from 1.5 to 20. An antenna element characterized by the above-mentioned. 10. The method according to claim 1, wherein
An antenna element, wherein the first and second radiation electrodes are formed to have the same width except for at least a portion that capacitively couples. 11. An antenna element having a radiation electrode and a feed electrode disposed on an insulating substrate, wherein the radiation electrode is formed at least in a spiral shape and is separated from and connected to a ground conductor by a required length. Antenna element. 12. A wireless communication device using the antenna element according to claim 1.