JP2001358515A - Chip type antenna element and antenna device as well as communication apparatus mounting the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a chip type antenna in size and enhance performance thereof and to provide an antenna device for raising a mounting density of circuit boards and a communication apparatus for mounting the same. SOLUTION: In the chip type antenna comprising microstrip conductors arranged on an insulating base having at least an end face, ground electrodes are provided at both ends of the base, one side of a radiation electrode provided on an upper surface is formed in an open end against the ground electrodes via gaps, the radiating electrode extended from the other grounding electrode toward the open end while continuously and/or stepwisely narrowing a width is formed, and a power supply electrode is provided at a side on its midway. Thus, wide band characteristics are obtained, and a directivity can be remarkably improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip-type antenna element, an antenna device using the same, and a communication device equipped with the chip-type antenna element. The present invention relates to a chip antenna element (hereinafter, may be simply referred to as an antenna element) suitable for a radio wave communication device.

[0002]

2. Description of the Related Art In a microwave radio communication device, especially a portable communication device such as a mobile phone, a monopole antenna, a microstrip antenna, or the like is generally used as an antenna element in order to reduce the size and height. Of these, the structure and principle of microstrip antennas, which have been increasingly used in recent years, are described in detail in the Antenna Engineering Handbook (pp. 109-111, Ohmsha, edited by the Institute of Electronics, Information and Communication Engineers).

At present, there is known a microstrip antenna element which is practically used, in which a radiation electrode is formed on the upper surface of a rectangular parallelepiped dielectric and power is supplied from the lower surface as described in Japanese Patent Application Laid-Open No. 10-209740. Have been. FIG. 16 shows the schematic configuration. When operating as an antenna, the antenna element 100 is arranged on a printed circuit board (not shown) on which the ground conductor 96 is arranged as shown in the figure, and power is supplied from the lower surface side by the power supply line 94. At the open end of the radiating electrode 90, lines of electric force are generated between the ground conductors 96 as shown in the figure, and a magnetic current is generated in the vertical direction of the radiating electrode, so that radio waves are efficiently radiated into space. That is, the length D of one side of the radiation electrode is usually selected to be about 1/4 wavelength, and at the time of resonance, a magnetic current is generated in a direction perpendicular to the radiation electrode. It occurs in orthogonal directions. Although various shapes such as a circular or pentagonal shape have been proposed as the shape of the radiation electrode 90 in addition to the rectangular electrode, a vertically or horizontally symmetrical one is mainly used.

It is necessary and sufficient conditions that an antenna used in a portable communication device has a small size, a low profile, a high radiation efficiency, and no directivity. In order to reduce the size and height of the antenna element, the above-described antenna element has a configuration in which a radiation electrode is disposed on or inside an insulating substrate. This is because the current flowing through the radiation electrode is affected by the adjacent insulating substrate and shortens its wavelength (wavelength shortening effect). Even if the radiation electrode is shortened, the same radiation efficiency can be obtained. Can be used. If the relative permittivity of the insulating substrate is εr, the resonance frequency is f ₀ , and the speed of light is c, the required antenna length d is approximately expressed as d = c / (2f ₀ √εr) (1) You.

As can be easily understood from the above equation, the antenna element having a microstrip structure has a propagation frequency (=
If f ₀ ) is constant, d, that is, the antenna element length can be shortened as εr of the insulating substrate increases. In other words, by using a substrate having a high relative dielectric constant,
It is possible to manufacture a low-profile microstrip antenna element with the same performance. In particular, a low-profile antenna device is indispensable for a mobile phone or the like, and development of an unprecedented small and high-performance antenna element is desired.

As an antenna system other than the microstrip antenna applied to a portable communication device, there is an inverted-F monopole antenna. This inverted-F type monopole antenna is a type in which a linear conductor short-circuited to a ground conductor plate is bent in the middle to form a radiation electrode, and a feeding terminal is connected between the ground conductor plate and the radiation electrode. . Since the radiation electrode only needs to be about 1/4 wavelength, it can be regarded as an antenna system developed in the conductor width direction as compared with the microstrip antenna element cited above.

[0007]

The above-mentioned conventional microstrip antenna has the following problems in reducing the size and height. That is, when the relative permittivity εr of the insulating substrate is increased with respect to a predetermined propagation frequency f ₀ , when the radiation electrode is shortened, the resonance characteristics are sharpened, and the band is narrowed to operate only in a narrow frequency range. This is not preferable as an antenna of a mobile phone or the like, but means a limitation on a frequency band usable for communication. Therefore, in developing a practical antenna, first, it is necessary to satisfy wideband characteristics. In particular, in a multi-frequency antenna using two or more frequencies, this narrowing phenomenon is a serious problem, and has exceeded the range controlled by only the physical properties of the insulating base.

In general, assuming that the bandwidth of the resonance characteristic is BW and the quality of the antenna at resonance is Q value, the resonance frequency f ₀ , BW
And Q have the following relationship. BW = f ₀ / Q (2) On the other hand, it is known that the height h of the microstrip antenna coincides with the thickness of the insulating substrate, and when expressed in relation to Q, Q∝εr / h (3) I have.

From the above equation, it can be explained that the use of an insulating substrate having a high relative dielectric constant εr results in an increase in the Q value and consequently a reduction in the bandwidth BW. On the other hand, if a tall antenna is used, Q is reduced, but the antenna cannot be reduced in size and height. In short, the miniaturization and height reduction of the antenna and the performance are in a trade-off relationship with each other, and it has been considered very difficult to satisfy both at the same time.

On the other hand, as a technique for miniaturizing a microstrip antenna, a method is known in which a radiation electrode is divided into two parts at a central portion and one end is short-circuited. This method is described in detail in New Antenna Engineering (pp.109-112 by Hiroyuki Arai, published by Sogo Denshi Shuppan). In this configuration, a linear radiation electrode is divided into halves at the center, and one end thereof and the ground conductor plate are electrically short-circuited. Since the length of one side of the radiation electrode is about 1/4 of the resonance wavelength, the size can be reduced by about 50% as compared with the related art. Japanese Patent Application Laid-Open No. H11-251816 describes that the bandwidth can be increased by providing the radiation electrode along the edge of the base or by wrapping around the adjacent surface. .

However, when this microstrip antenna element is incorporated in a portable communication device, a current is induced in a conductor portion of a housing or a circuit board disposed in the vicinity thereof mainly by a radio wave radiated from an end of a radiation electrode, The conductor part apparently acts as an antenna. In this type of antenna, the characteristics tend to fluctuate depending on the mounting state and the environment, resulting in impedance mismatch at the feeding point or fluctuation of the radiation directivity, and there is a mounting problem.

Further, since high-frequency electromagnetic waves are radiated from the end of the radiation electrode, the influence is exerted on electronic circuit components arranged in the vicinity, and deterioration of communication performance such as generation of noise, malfunction or abnormal oscillation is a problem. there were. The countermeasure that has been taken in the past was to place peripheral circuit components away from the antenna element.However, this method does not increase the mounting density around the antenna, and poses a major obstacle to miniaturization of communication equipment. Had become.

Accordingly, the present invention provides an antenna element capable of securing a Q value, increasing gain, and broadening a bandwidth without increasing the length and height of the antenna element, and mounting the antenna element on a circuit board. It is an object of the present invention to provide an antenna device having a small space and an increased mounting density without adversely affecting peripheral circuit components, and a communication device such as a portable information terminal equipped with the antenna device.

[0014]

As described above, it is necessary to simultaneously reduce the size and height of the antenna element and increase the bandwidth.
In the prior art, the application limit was exceeded. However, the present inventor has returned to the basic principle of the conventional antenna configuration,
As a result of deeply studying the operation using simulations and other details, it is possible to equivalently generate a plurality of resonance circuits in the antenna element by selecting the shape of the radiation electrode and the ground electrode. It is known that by selecting this, high gain radiation directivity and unnecessary electric field radiation can be blocked, and that by taking into account the mounting configuration on the ground conductor, the occupied area can be reduced and better characteristics can be obtained. did. With these, we realized that it is possible to obtain a compact, low profile, high gain, and broadband characteristics.
The present invention has been completed.

That is, the present invention relates to a chip antenna element having a radiation electrode in which a microstrip conductor is provided on an insulating base, a ground electrode, and a feed electrode, wherein at least one side of the radiation electrode provided on at least one surface has A chip-type antenna element having an open end, facing the ground electrode via a gap, and the other side located on the side opposite to the open end is grounded, and the radiation electrode is provided with a bandwidth control means. is there. As the bandwidth control means, there is a means provided so as to extend while narrowing the width of the radiation electrode continuously and / or stepwise toward the gap, which has a parallel multiple resonance function. It would be good if there was.

The present invention is also directed to a chip antenna element having a radiation electrode having a microstrip conductor disposed on an insulating base, a ground electrode, and a feed electrode, wherein at least one side of the radiation electrode provided on at least one surface has A ground electrode that faces the open end, covers one end face via a gap, extends at least to the ground plane, and continuously or capacitively couples the other end face to the other side of the radiation electrode. This is a chip type antenna element provided with a ground electrode extending at least to a ground plane.

The chip antenna element of the present invention has a radiation electrode having a microstrip conductor provided on an insulating base, a ground electrode, and a power supply electrode, and is provided on at least one surface, and one side is not open. A radiating electrode that extends while narrowing its width continuously and / or stepwise toward the open end, opposes the open end via a gap, and covers one end face and the four faces around it; The first provided
And a second ground electrode provided continuously or capacitively coupled to the other side of the radiation electrode so as to cover the other end face and the four faces around the other end face.

In the present invention, the power supply electrode may be provided in a contact or non-contact manner at a location where a predetermined impedance is obtained between the open end of the radiation electrode and the second ground electrode. Further, by connecting one of the ground electrodes arranged at both ends in the longitudinal direction so as to sandwich the radiation electrode to the radiation electrode, the intensity of the radiation electric field in the longitudinal direction of the radiation electrode is weakened, and conversely, It is desirable to have a directionally enhanced radiation electrode. When the width of the open end of one side of the radiation electrode is S and the width of the other side is W, W
/ S is desirably in the range of 2 to 5, and it is more preferable that the radiation electrode is disposed over the adjacent side surface of the insulating base.

The present invention also relates to an antenna device in which the above-mentioned chip-type antenna element is mounted on a circuit board. Specifically, the gap direction between the open end of the radiation electrode and the ground electrode is parallel to the ground conductor of the circuit board. And an arrangement in which the gap between the radiation electrodes is kept away from the ground conductor. Further, the feed electrode of the above-mentioned chip type antenna element is provided so as to be deviated toward the open end side with respect to the center of the base, and the ground electrodes at both ends are connected to a ground conductor portion provided left and right apart from the ground conductor of the circuit board. Thus, the antenna device is arranged such that the longitudinal direction is arranged side by side with the ground conductor and is arranged in parallel, and power is supplied to the feed electrode from a feed line provided between the protruding ground conductors. Also, the present invention
A communication device equipped with any of the above-described antenna devices, for example, a communication device mounted on a mobile phone, a headphone, a personal computer, a notebook PC, a digital camera, or the like as a Bluetooth antenna.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration and operation of the present invention will be described below in detail. FIG. 1 illustrates the principle of the present invention. FIG. 1A shows a case where an antenna element is formed on a flat plate.
(B) is a perspective view in the case of a chip type. However, in the present invention, even a flat antenna element as shown in FIG. If the antenna element of the present invention is simplified by first taking a conventional inverted-F antenna as an example as shown in (a), the radiation electrode 13 does not have a shape in which the conductor width is reduced toward the open end (gap). , A part of the ground conductor 31 is extended near the open end, and the other side 1
5 can be described as a configuration grounded to a ground conductor. A more specific embodiment is shown in FIG. That is,
The antenna element 10 has a substantially rectangular parallelepiped insulating base 11.
Ground electrodes 15 and 17 covering the end portions are disposed on both end surfaces of
The radiation electrode 13 is provided in the center of the upper surface, and power is supplied from the power supply electrode 14 on the side to the middle of the radiation electrode.
One side of the radiation electrode 13 has an open end and no ground electrode 1
7, a gap portion 12 is formed, and one other side is integrally connected to the ground electrode 15. Here, the most different point from the conventional antenna element is that the radiation electrode is formed to have a substantially trapezoidal shape and extend while reducing the width toward the gap. Ground electrodes are provided at both ends of the insulating base, and both ground electrodes are not electrically connected. The longitudinal direction is parallel to the ground conductor (not shown) of the circuit board (this is referred to as “parallel” in the present invention). The gap part is arranged so as to be farthest from the ground conductor. It is. Next, the operation, operation, and the like of each item will be described in detail.

First, regarding the shape of the radiation electrode, the length of the electrode in the direction perpendicular to the flow of the high-frequency current, that is, the width of the electrode was not fixed, but was gradually reduced as approaching the gap 12 side. Generally, the power supply electrode 1
The high-frequency current supplied via 4 causes resonance at a frequency determined by the capacitance of the capacitor formed between the inductance of the radiation electrode and the ground, and is radiated to the space as electromagnetic energy. At this time, a current distribution mode is set in which the ground electrode 15 and the gap 12 are nodes and antinodes. If the width of the radiation electrode is constant, there is only one current distribution mode.
However, a plurality of resonance circuits are equivalently formed in the element because the width of the radiation electrode disposed between the ground electrodes is not constant and each electrode arrangement is illustrated. In addition, a plurality of resonance frequencies of each resonance circuit are present in a very close relationship in terms of configuration, and have a broadband resonance characteristic when viewed macroscopically. This indicates a decrease in the Q value.

The physical meaning of the above-mentioned phenomenon will be examined. FIG. 2A shows an equivalent circuit of the antenna element of FIG. The power supply 19 is connected to the radiation electrode 13 via the inductance Li and the capacitor Ci by the power supply electrode or the like.
To supply current. The supplied power is radiation resistance at resonance.
Consumed in space at r. This consumed power is radiated into space as electromagnetic waves. In the equivalent circuit,
The portion surrounded by a broken line on the right side of the power supply 19 is related to the portion 13-1 by the radiation electrode, and the left side is related to the portion of the ground electrode 17 including the gap portion 12. The capacitance between the radiation electrode 13 and the ground electrode 17 is Cg. Displayed in the equivalent circuit.

On the other hand, FIG.
The equivalent circuit shown in FIG. In this case, the radiation electrode can be simply replaced with the inductance L and the capacitor C. On the other hand, in the case of the present invention having a non-uniform width, it is necessary to treat it as a distributed constant in consideration of the operation by the radiation electrode. For this reason, it can be considered that an appropriate division is made and the corresponding inductance and capacitor are connected. Therefore, the equivalent circuit including the radiation electrode 13 has a plurality of inductances Lr
It makes the most sense to display as a ladder type circuit with 1, Lr2, Lr3 and capacitors Cr1, Cr2. In the circuit shown in the figure, three or more resonance circuits are formed. However, due to the configuration, the resonance frequencies appear to be very close to each other, so that the resonance appears to occur continuously. Becomes the spread characteristic.

Although the radiation electrode in the above-described example is assumed to be trapezoidal, it is not limited to a trapezoid as apparent from the gist of the invention, and various shapes can be considered. The gist of the present invention is to distribute inductance with respect to a microstrip conductor of equal width.
That is, a plurality of resonance circuits are formed by the distributed inductance and the capacitance, that is, a function of a parallel multiple resonance circuit is provided. In other words, the width of the radiation electrode changes with respect to the current flowing toward the ground electrode having the gap. If the width of the radiation electrode changes continuously and / or stepwise, the present invention will be described. It is clear that the effect of the above can be enjoyed. FIG. 15 shows another embodiment of the radiation electrode shape. However, it is not limited to this.

Next, the dimensions and shape of the above-mentioned radiation electrode will be described. FIG. 3 shows a radiation electrode 1 as a typical example of the present invention.
3 is a trapezoidal shape. Here, the other side (wide portion) connected to the ground electrode 17 is defined as W, and is inclined appropriately by the length of D from here toward the distal end, and the open end of the distal end (narrow portion).
Is S. FIGS. 4, 5, and 6 show the results of examining suitable ranges for the dimensions of each part shown in the drawings. In the characteristic curve of FIG. 4, the horizontal axis represents the conductor shape ratio W / S, and the vertical axis represents the resonance frequency f ₀ . f ₀ tends to be saturated when W / S is about 4 or more. This is because, when S becomes equal to or less than a predetermined value, the resonance frequency becomes higher, and the practical range is deviated. Further, the characteristic curve of FIG. 5 shows the characteristic of the relative bandwidth with respect to W / S. From this characteristic curve, the fractional band value (BW / f ₀ ) tends to be saturated when W / S is about 3 or more, and the object of the present invention can be sufficiently achieved if it is within 3.5%. The characteristic curve in FIG. 6 shows the Q value on the vertical axis, and shows the change in the Q value with respect to W / S. From this characteristic curve, it can be seen that the W / S is large, that is, the Q value decreases as the tip becomes thinner, and a wider band is achieved, and the W / S satisfying the Q value ≦ 29 is 3 or more. From the above examination results, the W / S is preferably in the range of 2 to 5 in view of the margin.

Next, the arrangement of the ground electrodes will be described. In addition to the microstrip antenna, when the antenna radiates radio waves, electromagnetic energy is radiated into space by an electromagnetic field formed between the radiation electrode and the ground conductor. Therefore, on the opposite side of the ground electrode which is at the same potential as the ground conductor, the electromagnetic field is very weak, so that the radiation energy is considerably small. By utilizing this effect, an electronic circuit element or the like can be mounted close to the antenna element. In other words, by actively utilizing the shielding effect in consideration of the arrangement of the ground electrode, it is possible to eliminate the influence of the housing, the conductor of the wiring board, and the like, and to prevent the malfunction of the circuit components, thereby stabilizing the characteristics and improving the characteristics. Improved reliability is obtained. This concept is the second and third feature points of the present invention. FIG. 7 shows a typical configuration as an antenna device.

As shown in FIG. 7, the antenna element 10 is connected to the ground plane (ground conductor) 55 of the substrate so as to
Place on top. The radiation electrode 13 is a ground electrode 15 at both left and right ends.
And 17 and the ground plane (ground conductor) 55 on the lower surface, and the open surface is in three directions of the upper surface and the two side surfaces. Therefore, the radiation electric field intensity in the length direction of the radiation electrode is weakened, and conversely, the directivity is enhanced in the vertical direction, and the gain is improved. On the other hand, since the effect of electromagnetic waves in the length direction of the radiation electrode is reduced due to the shielding effect of the ground electrodes 15 and 17, there is no problem even if the components 51, 52, etc. are placed on the side surface of the base, and the degree of freedom of mounting layout is improved. The density can be increased to save space.

As shown in FIG. 8, according to the present invention, when the antenna element 10 is placed on the ground plane (ground conductor) 55 on the module substrate 50, the open end of the radiation electrode is grounded with respect to the ground conductor. The gap directions (indicated by arrows) between the electrodes 17 are arranged substantially in parallel, that is, side by side. Further, at this time, ground electrodes 15 and 17 at both ends are placed on a ground conductor portion 550 projecting away from the ground conductor 55 to the left and right, and the antenna element is adjacent to the ground conductor so that the radiation electrode and the electric field radiation area of the gap portion 12 are formed. It was arranged to be farthest from the ground conductor 55. Here, the electrical interaction with the substrate includes a phenomenon in which a resonance current of the antenna generates a mirror image current on the substrate. If the mirror image current and the current on the substrate side have opposite phases, electromagnetic radiation from the antenna may be hindered, resulting in a decrease in gain or a shift in resonance frequency. At this point, the arrangement shown in the drawing allows the radiation electrode and the gap portion where the resonance current flows most strongly on the antenna base to be arranged at the position farthest from the ground conductor, and the electric field can be induced at a position away from the ground conductor. As a result, the mirror image current can be reduced as much as possible, and the mirror image current to the substrate can be reduced because most of the back surface of the antenna base has no ground electrode.

Conventionally, the antenna element is often arranged perpendicular to the ground conductor in view of the above problem. In such a case, it goes without saying that the dead space increases and the degree of freedom in design is low. The reason why they are arranged in parallel as in the present invention is to actively bring out the above-mentioned shape effect of the radiation electrode and also to increase the action of a capacitor formed between the radiation electrode and the ground plane. The above description can be easily understood with reference to FIGS. 7 and 8 in which the directions of the radiation electrode 13 and the gap portion 12 are substantially parallel to the ground conductor 55.
Therefore, in the case of the present invention in which the radiating electrodes are arranged in parallel with the ground conductor, and in comparison with the prior art in which the radiating electrodes are arranged vertically,
The capacitor action between the ground conductors is much stronger in the present invention,
Unprecedented effects can be achieved.

Next, regarding the radiation directivity of this antenna element, first, an electric field is radiated between the radiation electrode 13 and the ground electrode 17 via the gap portion 12 in the longitudinal direction of the antenna base. An electric field can also be generated in the direction between the gap and the substrate, which is perpendicular to the gap. Therefore, this antenna device generates electric fields in two orthogonal directions, so that when mounted on each communication device, omnidirectional directivity can be exhibited and communication can be performed stably and reliably regardless of posture.

[0031]

Embodiments of the present invention will be described below in detail with reference to the drawings. First, FIGS. 9A, 9B, and 9C show the dimensions (length L, width W) and bandwidth (B) of the insulating base of the antenna element.
W) and the relative dielectric constant (εr) and the bandwidth. Since the bandwidth varies depending on the dimensions and the material of the element substrate as described above, the relation between the element dimensions and the bandwidth and the relation between the element material and the bandwidth as shown in FIG. The present invention can be implemented. Here, as a result of the study using FIG. 9 on the premise that a bandwidth of 100 MHz is obtained, a rectangular solid (1
5mm x 3mm x 3mm) dielectric ceramic with relative permittivity ε
r = 8, an Al ₂ O ₃ material was used. The electrodes were made of an Ag electrode material, and provided on the surface of the insulating base 11 at the positions and shapes as shown in FIG. At this time, the radiation electrode 13 was substantially trapezoidal, and the ratio of the upper base S to the lower base W was 1: 3. In addition, a gap (exposed portion of the insulating base) 12 having a length of 1 mm was provided between the open end of the radiation electrode 13 and the ground electrode 17.
The other end (lower bottom W side) of the radiation electrode 13 is provided by continuously connecting the ground electrode 15 here. The power supply electrode 14 is provided on the side of the base body from the center to the gap side. Note that the antenna element having the above-described dimensions has a propagation frequency of 2.4 to
2.5 GHz, bandwidth 100 MHz, bandwidth ratio 3.5%,
It is designed for a mobile phone or a wireless LAN that satisfies performances such as a gain of 0 dBi or more and a voltage standing wave ratio (VSWR) of 3 or less and requires omnidirectionality in a specific plane.

The above embodiment is an example, and the dimensions and configuration can be appropriately selected depending on design conditions and the like. For example, the substantially rectangular parallelepiped dielectric substrate may be cylindrical, and the material may be a magnetic substrate, a resin substrate, or a laminated substrate thereof. The shape of the radiation electrode and the width dimension between the open end and the ground end can also be changed outside the range of 2 to 5. Also, it is effective to trim the gap and the radiation electrode to increase the bandwidth and adjust the frequency. At this time, the inclined surface near the open end of the radiation electrode forms a parallel part, and this parallel part is trimmed. This will make the matching work easier. It is necessary that the open end of the radiation electrode is opposed to the ground electrode via a gap, but the other side does not necessarily have to form the ground electrode continuously. What is necessary is just to be able to ground. In addition, it can be said that the ground electrode only needs to cover its end face at least for the purpose of suppressing the emission of the electric field from the end face of the base body and be connected to the ground plane to be grounded. However, in order to surely obtain the effect, it is desirable to form the base end so as to cover the end face and the four faces around the end face as shown in the figure. Further, the power supply electrode may be provided around the end surface or the upper surface of the base around the radiation electrode, and may be in contact or non-contact. However,
It is not provided facing the open end of the radiation electrode.

The antenna element was manufactured using the following steps. First, a block of dielectric ceramics is prepared by firing, and a plurality of rectangular parallelepiped chips having appropriate dimensions are cut out from the block and ground to predetermined dimensions. Thereafter, a row was formed by arranging a plurality of the dielectric chips, and an Ag electrode was formed on these surfaces in a predetermined shape and position by screen printing. Next, after drying these chips, end electrodes were printed and formed, and an electrode element was completed through an electrode baking process.

FIG. 10 shows a prototype antenna element and its evaluation method. The micro antenna element 10 is disposed on the circuit board 71 substantially in parallel with the end of the ground conductor 73, and the inclination of the radiation electrode and the gap portion 12 are set apart from the ground conductor. In this configuration, power is supplied from the power supply 19 via a power supply line 75 located therebetween.
The radiation electrode 13 is connected to the other side (wide portion) 16 on the side of the ground electrode 15.
, From which an inclined surface extending continuously while reducing the width is formed to form an open end (narrow portion) 18. And
The gap portion 12 is provided between the open end (narrow portion) 18 and the ground electrode 17. The feed electrode 14 is provided so as to be closer to the gap portion 12 than the center in the longitudinal direction of the radiation electrode, so that the antenna element itself is also provided to be biased with respect to the ground conductor. Although the ground electrode 15 and the radiation electrode 13 are shown as separate bodies, they are integrally formed. However, this may be separate and have a gap.

The evaluation items of the characteristics include a voltage standing wave ratio (VSWR), directivity, and gain characteristics. VSWR
In the measurement, a network analyzer was connected to the power supply terminal, and the impedance viewed from the terminal side was measured. When measuring the gain, the radiated power from the antenna under test was received by the receiving reference antenna in the anechoic chamber, and evaluated as a ratio to the reference antenna. Regarding the directivity, the antenna element under test was mounted on a rotary table, and while rotating, the intensity of the radiated electric field was measured for the gain at each rotation angle in the same procedure as the gain measurement. FIG.
At 0, the position of the power supply electrode 14 is biased toward the open end in the middle of the radiation electrode. In contrast, the center, ground electrode 1
An antenna element under test different from the case on the 6 side was similarly prototyped, and similar measurements were performed.

FIGS. 11 to 13 show directional characteristics when the antenna element under test of FIG. 10 is rotated about the X, Y and Z axes. As can be seen from the results shown in the figure, the gain was almost close to a circle for all three axes, and omnidirectional characteristics without directivity were obtained.
However, a slight decrease in gain was observed in the longitudinal direction of the antenna element having the ground electrode. The reason for this is that the intensity of the electric field radiated in the direction of the ground electrode was weakened, and the result proved the features of the antenna according to the present invention. FIG. 14 shows bandwidth characteristics. A remarkable improvement was observed as compared with the conventional case, and the bandwidth when the voltage standing wave ratio VSWR was 3 could be made 100 MHz as intended. In addition, with respect to the antenna element in which the position of the feed electrode was changed, the bandwidth was inferior to those of FIGS. 11 to 14, and the influence of the position of the feed electrode and the position of the antenna element on the ground conductor was confirmed. The power supply electrode supplies power in the middle of the radiation electrode. However, in the case of non-contact, matching can be performed by the capacitance of the capacitor, so that the power supply electrode can be arranged near an open end having high impedance. On the other hand, when it comes into contact with the radiation electrode, since there is only the inductance, matching is difficult, and it is unavoidable to dispose it on the wide portion side where the impedance is low. From these facts, it is desirable that the power supply electrode be located on the narrow portion side in the case of non-contact and on the wide portion side in the case of contact.

Next, another embodiment of the present invention will be described with reference to FIGS.
It is shown in FIG. First, FIG. 15 shows a top perspective view (a) of the antenna element, a top perspective view (b) of the opposite side, and a perspective view (c) of the bottom side. In this example, the radiation electrode 131 is provided not only on the upper surface but also on the adjacent side surface. With such a configuration, the radiation electrode can be substantially widened, and the radiation gain in the circumferential direction can be improved, and the size and height can be further reduced. Further, when the thickness of the base is further reduced (for example, 2 mm or less), the emission electrode on the side surface may not form an inclination, but the emission electrode on the upper surface functions as it is, so there is no problem in characteristics. Further, a radiation electrode can be extended on the lower surface side of the insulating base. (C) As is clear from the figure, the ground electrodes 15 and 17 are provided only at both ends, and both are not electrically connected. The example of FIG. 16 is a perspective view similar to FIG. 15, but this antenna element is of a direct power supply type in which a power supply electrode 142 is connected to a trapezoidal radiation electrode 132. Further, a conductor 150 is arranged on the lower surface, and is configured to conduct with the ground electrode.

Although the example of FIG. 17 shows only one perspective view,
A gap is provided between the radiation electrode 133 and the ground electrode 15 on the other side to perform capacitive coupling. The same applies to the following examples, but in this example, trapezoidal radiation electrodes are provided over two surfaces, one end is provided with a ground electrode 17 covering the end via the gap portion 12, and the other end is provided with the end. The configuration in which the covering ground electrodes 15 are provided is the same, and the operation and effect of the present invention described above can be similarly enjoyed. In particular, in this embodiment, the gap between the radiation electrode and the ground electrode (gap)
Are provided at two places, the electric field generated in this gap is radiated over a wide range, so that the Q value is reduced and a wider band can be expected. The example shown in FIG. 18 has a configuration in which the radiation electrode 134 and the ground electrode 15 are partially connected. The base portion of the base 161 is also provided with a trimming element, so that the resonance frequency can be adjusted by changing the length of this portion or cutting it. In the example shown in FIG. 19, the radiation electrode 135 is formed in a meandering shape over two surfaces as shown. In this embodiment, since the resonance current flows through the meandering radiating electrode, the length of the meandering electrode is about 1 / the electric length.
Equivalent to 4. For this reason, there is an effect that the antenna dimensions can be further reduced by shortening the length of the radiation electrode.

FIG. 20 shows another embodiment of the shape of the radiation electrode. These examples are considered for the purpose of the present invention, and it is obvious from the figure that the width on the head side is smaller than that on the bottom side and that the requirements such as not having to be symmetrical are satisfied. It is. (G) ~
In the pattern examples up to (l), the state where the ground electrode is connected to or separated from the lower part of the radiation electrode is shown together, and the involvement with the ground electrode is also shown.

In the above-described embodiment, an insulating substrate made of ceramics is used as the dielectric. However, it may be made of a dielectric such as resin or a magnetic material which is an insulator. In the case of a resin or the like, a hole may be formed in the base, and a power supply point may be provided here. By mounting an antenna device in which the above-described antenna element is mounted on a circuit board in a wireless communication information terminal device such as a mobile phone, a communication device having omnidirectionality and good antenna characteristics such as gain and bandwidth can be obtained. . Further, the surface-mounted antenna device can be designed with a small occupation area and a high degree of freedom, and can contribute to a reduction in the size of communication equipment because of a space saving and an increase in mounting density. For example, in the antenna device on which the antenna element (15 mm × 3 mm × 3 mm) is mounted, the occupied area of the antenna element at the time of mounting is 50 mm ² or less,
Space saving of less than 1/2 compared with the antenna device of the conventional structure was achieved.

[0041]

As described above, according to the present invention,
A high-performance chip-type antenna element and antenna device having omnidirectionality (omnidirectionality), high gain over a wide band, and capable of miniaturization and reduction in height have been obtained. In addition, when this antenna element is mounted on a circuit board, the occupied area can be minimized and the mounting density can be improved, and when the antenna element is mounted on a communication device such as a portable wireless communication information terminal device, the device itself can be improved. In addition to contributing to miniaturization, stable communication performance can be achieved regardless of the position or orientation of the device.

[Brief description of the drawings]

FIGS. 1A and 1B are perspective views of an antenna element for explaining the principle of the present invention. FIG. 1A shows an example in which the antenna element is provided on a plane, and FIG.

FIG. 2A is an equivalent circuit diagram of the antenna element of FIG. 1,
(B) is an equivalent circuit diagram of a conventional antenna element.

FIG. 3 is a perspective view showing a configuration of a radiation electrode of a basic antenna element of the present invention.

FIG. 4 shows a ratio of a wide width W to a narrow width S of a radiation electrode according to the present invention.
Characteristic diagram showing the relation between W / S and the propagation frequency f _0.

FIG. 5 is a ratio of a wide width W to a narrow width S of a radiation electrode according to the present invention.
FIG. 4 is a characteristic diagram showing a relationship between W / S and a relative bandwidth BW / f ₀ .

FIG. 6 shows the ratio between the wide width W and the narrow width S of the radiation electrode in the present invention.
FIG. 4 is a characteristic diagram showing a relationship between W / S and a Q value.

FIG. 7 is a schematic mounting diagram showing an antenna device when the antenna element of the present invention is mounted on a circuit board.

FIG. 8 is a schematic mounting diagram of an antenna device showing an arrangement when the antenna element of the present invention is mounted on another circuit board.

9A and 9B are data of an insulating substrate to which the present invention is applied, wherein FIG. 9A shows the relationship between the substrate length and the bandwidth, FIG. 9B shows the relationship between the substrate width and the bandwidth, and FIG. 9C shows the permittivity of the substrate. FIG. 4 is a characteristic diagram illustrating a relationship between the bandwidth and the bandwidth.

FIG. 10 is a schematic view showing an example of an antenna element evaluation method according to the embodiment.

FIG. 11 shows directional characteristics with respect to the Z axis as a result of evaluating the antenna element of the example.

FIG. 12 shows directional characteristics with respect to the X axis as a result of evaluating the antenna element of the example.

FIG. 13 shows directional characteristics with respect to the Y-axis as a result of evaluating the antenna element of the example.

FIG. 14 shows a bandwidth characteristic as a result of evaluating the antenna element of the example.

FIG. 15 shows another embodiment according to the present invention, in which (a) is a top perspective view of an antenna element, (b) is a top perspective view of an opposite side,
(C) A perspective view of the lower surface side.

16A and 16B show still another embodiment according to the present invention, wherein FIG. 16A is a top perspective view of an antenna element, FIG. 16B is a top perspective view of the opposite side, and FIG.

FIG. 17 is a top perspective view of an antenna element according to another embodiment of the present invention.

FIG. 18 is a top perspective view of an antenna element according to another embodiment of the present invention.

FIG. 19 is a top perspective view of an antenna element according to another embodiment of the present invention.

FIG. 20 is a plan view showing another embodiment of the radiation electrode of the antenna element of the present invention.

FIG. 21 is a configuration diagram showing an example of a conventional microstrip antenna element.

[Explanation of symbols]

10: antenna element, 11: insulating base, 12: gap, 13, 131, 132, 133, 134, 135:
Radiation electrode, 14: feeding electrode, 15, 17: ground electrode, 1
6: other side (wide part), 18: open end (narrow part), 1
9: power supply, 31: ground conductor, 51, 52: circuit components, 5
5: ground plane (ground conductor), 71: circuit board, 73: ground conductor, 75: feed line, 90: radiation electrode, 92: ground electrode,
94, 142: feeding electrode, 96: ground conductor

Claims (13)

[Claims] 1. A chip antenna element having a radiation electrode in which a microstrip conductor is provided on an insulating base, a ground electrode, and a feed electrode, wherein one side of the radiation electrode provided on at least one surface is not an open end. A chip-type antenna element, wherein the other side opposite to the open end opposite to the ground electrode via the gap is grounded, and the radiation electrode is provided with bandwidth control means. . 2. The apparatus according to claim 1, wherein said bandwidth control means extends while narrowing a width of said radiation electrode continuously and / or stepwise toward said gap. 2. The chip antenna element according to 1. 3. A chip antenna element having a radiation electrode having a microstrip conductor disposed on an insulating substrate, a ground electrode, and a feed electrode, wherein at least one side of the radiation electrode provided on at least one surface is not an open end. , Facing this open end,
A ground electrode that covers one end face via a gap and extends to at least the ground plane, and a ground electrode that covers the other end face and extends at least to the ground plane by continuous or capacitive coupling on the other side of the radiation electrode is provided. A chip type antenna element characterized by the above-mentioned. 4. The chip antenna according to claim 3, wherein said radiation electrode is provided so as to extend while narrowing its width continuously and / or stepwise toward said gap. element. 5. A chip antenna element having a radiation electrode in which a microstrip conductor is disposed on an insulating base, a ground electrode, and a feed electrode, provided on at least one surface, one side of which is an open end, and whose width is reduced. A radiating electrode that extends while narrowing continuously and / or stepwise toward the open end, opposing the open end via a gap, and covering one end surface and four surfaces around it; A chip-type antenna comprising: a first ground electrode; and a second ground electrode provided continuously or capacitively coupled to the other side of the radiation electrode so as to cover the other end face and four surrounding areas. element. 6. A radiating electric field strength in a longitudinal direction of the radiation electrode is weakened by connecting one of ground electrodes arranged at both ends in a longitudinal direction so as to sandwich the radiation electrode to the radiation electrode, 6. The chip antenna element according to claim 1, wherein the radiation electrode has a reinforced vertical direction. 7. The chip type according to claim 1, wherein a power supply electrode is provided in a contact or non-contact manner at a location where a predetermined impedance is obtained on the ground side from the open end of the radiation electrode. Antenna element. 8. The W / S is set in a range of 2 to 5, where S is the width of the open end of one side of the radiation electrode and W is the width of the other side. The chip-type antenna element according to any one of the above. 9. The chip-type antenna element according to claim 1, wherein the radiation electrodes are arranged over adjacent side surfaces of the insulating base. 10. The chip antenna element according to claim 1, wherein a gap direction between an open end of said radiation electrode and a ground electrode is parallel to a ground conductor of a circuit board, and An antenna device, wherein a gap between the radiation electrodes is arranged to be away from a ground conductor. 11. The feed electrode of the chip-type antenna element according to any one of claims 1 to 9 is provided so as to be biased toward the open end with respect to the center of the base, and the ground electrodes at both ends are connected to the ground conductor of the circuit board. An antenna device wherein the longitudinal directions are arranged in parallel so as to be connected, and power is supplied to the power supply electrode from a power supply line provided between the ground conductors. 12. The antenna device according to claim 10, wherein the chip-type antenna element is arranged so as to be deviated from a ground conductor. 13. A communication device comprising the antenna device according to claim 10.