JP2005269301A - Built-in antenna and electronic equipment having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a built-in thin type antenna adaptable to wide dual bands without increasing the occupied area of the antenna. <P>SOLUTION: A first and second antenna elements 1, 2 have lengths corresponding to about 1/4 wavelengths of the center frequencies of a first and second frequency bands, respectively. The first (second) antenna element 1 (2) has a horizontal part 1a (2a) and a vertical part 1b (2b) and is laid so as to superpose the horizontal part 1a of the first antenna element 1 on the horizontal part 2b of the second antenna element 2. The horizontal parts 1a, 2a are formed on a plane orthogonal to a plane having a conductor pattern 7 formed thereon. The horizontal part 1a of the first antenna element 1 has hanging parts 1c extending to the second antenna element 2 at its both sides within the range of superposing on the horizontal part 2a of the second antenna element 2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an antenna used for an electronic device such as a mobile communication device, and more particularly to a built-in antenna corresponding to a dual band and an electronic device using the same.

  In recent years, with the rapid spread of mobile communication devices, as typified by mobile phones, there is a tendency for one communication system to have a shortage of lines, so two types of wireless communication systems can be used in one terminal. Dual band support is progressing. In addition, as a countermeasure against damage due to design or dropping, antennas are being built in. Conventional dual-band built-in antennas are known in which each antenna is formed to extend in the same plane so that the coupling between the two antennas is lowered and each antenna can be adjusted independently. (For example, see Patent Documents 1 and 2). FIG. 8 is a perspective view of the built-in antenna proposed in Patent Document 1. In FIG. As shown in FIG. 8, the first antenna element 101 and the second antenna element 102 are formed in the antenna arrangement region 103 parallel to the ground 106 so as to be separated from each other. Power is supplied from 105. FIG. 9 is a perspective view of the built-in antenna proposed in Patent Document 2. As shown in FIG. 9, the first antenna element 201 and the second antenna element 202 are attached to the PCB 205 via the dielectric substrate 203 and connected to the feeder line 204. A matching bridge 207 is connected between the connection point and the grounding post. In these built-in antennas, the size of each antenna element is determined by the frequency band used. In these conventional examples, the structure arranged so as to extend away from the position near the feeding point can perform impedance adjustment in each frequency band independently, so workability for adjustment of element length, etc. However, since the antenna elements are arranged in a direction in which they are separated from each other, an arrangement space corresponding to the antenna elements is required. Further, in order to improve the performance of the antenna itself, it is necessary to increase the distance between the antenna element and the ground. As a result, there is a problem that the thickness of a terminal (electronic device) incorporating these antennas increases.

As a conventional technique for improving antenna performance other than the above, there is a method using a parasitic element (for example, see Patent Document 3). FIG. 10 is a perspective view of the built-in antenna proposed in Patent Document 3. As shown in FIG. As shown in FIG. 10, the first antenna element 301 includes a first radiating conductor element 301a, a second radiating conductor element 301b, a feeding line 304 connected to the feeding point 305, and a short-circuit terminal 307 connected to the ground 306. The second antenna element 302 that is not directly connected to the first antenna element 301 and the ground 306 is disposed in parallel with the first antenna element 301 and the ground 306. Capacitance is generated between each of the first and second antenna elements 301 and 302 and the ground 306, and electromagnetic coupling between the first antenna element 301 and the second antenna element 302 is used. By doing so, it is said that a wide band, high sensitivity, and miniaturization can be achieved. However, in the configuration of this conventional example, an antenna element (radiating conductor element) and a parasitic element (second antenna element) are required for one desired frequency band, so a space for arranging these elements is necessary. Thus, there is a problem that the area occupied by the antenna increases.
JP 2002-185238 A Japanese translation of PCT publication No. 2002-520935 JP 2002-330023 A

In the configuration in which the first and second antenna elements shown in FIG. 8 and FIG. 9 are arranged so as to be separated from each other, the planar shape of the built-in antenna corresponding to the dual band is increased, and as shown in FIG. In the configuration in which the parasitic element is disposed between the antenna element and the ground, the occupied area of the antenna increases, and thus there is a problem that the size of the electronic device incorporating the antenna increases.
Furthermore, in the conventional built-in antenna corresponding to an inverted L shape or inverted F shape dual band, the main portion (horizontal portion) of the antenna element is arranged in parallel with the ground. Since the vertical direction is the thickness direction of the electronic device housing, it has been difficult to reduce the thickness of the electronic device. Here, in order to improve the characteristics of the antenna element, it is necessary to increase the distance between the antenna element and the ground by a certain distance or more, which makes it difficult to make the electronic device thinner.
An object of the present invention is to solve the above-described problems of the prior art, and an object of the present invention is to provide a thin and wide band built-in dual-band antenna without increasing the area occupied by the antenna. .

  In order to achieve the above object, according to the present invention, there is provided a dual-band built-in antenna corresponding to the first frequency band and the second frequency band, the first frequency band and the second frequency band. Each of the first and second antenna elements each having a plate-like shape and having a horizontal portion and a vertical portion, and a ground. The antenna element and the second antenna element are arranged such that the horizontal portion of the first antenna element is placed on the upper side and the horizontal portion of the second antenna element is placed on the lower side. A built-in antenna is provided.

Preferably, the second frequency band is higher than the first frequency band. For example, the center frequency of the second frequency band is set to be twice or more the center frequency of the first frequency band.
Preferably, the horizontal portion of the first antenna element has a hanging portion bent in a direction approaching the second antenna element on both sides within a range facing the horizontal portion of the second antenna element. ing.
Preferably, the ground includes a conductor pattern formed on the substrate, and the plane on which the conductor pattern is formed is orthogonal to the plane on which the horizontal portions of the first and second antenna elements are formed. doing.

Since the built-in antenna of the present invention is formed by stacking the first and second antenna elements, the arrangement space can be reduced as compared with the case where both are arranged apart on a plane.
In addition, since the first antenna element is provided with a hanging portion directed toward the second antenna element, the first antenna element acts in the same manner as the parasitic element in the operation in the second frequency band. Thus, there is no need to newly provide a parasitic element, and the antenna performance can be improved without increasing the area occupied by the antenna.

When the center frequency of the second frequency band is about twice or more than the center frequency of the first frequency band, the resonance frequency substantially depends on the length of the first antenna element in the operation in the first frequency band. However, since the influence of the second antenna element is almost eliminated, the first element length is first adjusted and fixed, and then the length of the second antenna element and the distance from the first element are adjusted. By adopting the above, it is possible to easily adjust the antenna input impedance characteristics in the first frequency band and the second frequency band.
Furthermore, by arranging the conductor pattern as the ground so as to be orthogonal to the horizontal portion of the antenna element, the height direction of the antenna can be set to the length direction of the electronic device, and the electronic device can be thinned. .

Next, embodiments of the present invention will be described in detail with reference to the drawings.
[First embodiment]
FIG. 1 is a perspective view showing a built-in antenna according to a first embodiment of the present invention. As shown in the figure, the built-in antenna of this embodiment includes a first antenna element 1 and a second antenna element 2 having a plate-like shape and an inverted L shape, and a ground formed on a substrate 6. And a conductive pattern 7. The first antenna element 1 and the second antenna element 2 have a length corresponding to about ¼ wavelength of the center frequency of each of the first frequency band and the second frequency band. The first antenna element 1 has a horizontal portion 1a and a vertical portion 1b, and the second antenna element 2 has a horizontal portion 2a and a vertical portion 2b. The horizontal portion 1a of the first antenna element 1 is arranged on the horizontal portion 2a. The plane on which the horizontal portion 1a of the first antenna element 1 is formed and the plane on which the horizontal portion 2a of the second antenna element 2 is formed are orthogonal to the plane on which the conductor pattern 7 is formed. . The horizontal portion 1a of the first antenna element 1 is provided with a hanging portion 1c extending in the direction of the second antenna element 2 on both sides in a range overlapping the horizontal portion 2a of the second antenna element 2. The first antenna element 1 and the second antenna element 2 are connected in common and are fed from a feeding point 5 via a feeding line 4. The first and second antenna elements are arranged such that the antenna element width is in the thickness direction of the electronic device.

  The antenna element is a thin plate-like conductor in which a conductive metal such as gold, nickel, etc. is applied to a conductive metal such as copper, copper alloy, and stainless steel, and is insert-molded into an inverted L-shaped resin block 3 Have Or the structure which formed the electroconductive pattern which printed the electroconductive coating material on the surface of the resin block 3 may be sufficient. Alternatively, a metal thin film such as copper or nickel may be formed on the surface of the resin block 3 by sputtering or vapor deposition, and a plating layer such as gold or nickel may be formed thereon.

Next, the operation of the dual-band built-in antenna configured as described above will be described. When operating in the first frequency band, the resonance current is distributed mainly on the first antenna element, the resonance frequency is determined approximately by the length of the first antenna element, and the frequency band is determined by the first antenna element. Determined by width and degree of electromagnetic coupling with ground. Therefore, by increasing the width of the first antenna element by making the maximum use of the thickness of the electronic device, the inductance component is reduced and the frequency band is expanded.
When operating in the second frequency band, the resonance current is distributed on the second antenna element, and an induced current for the resonance current is generated on the first antenna element. The resonance frequency is determined by the length of the second antenna element and the distance between the first antenna element and the second antenna element, and the frequency band is the electromagnetic coupling with the width of the second antenna element and the ground, It is determined by the distance between the first antenna element and the second antenna element. Similarly to the operation in the first frequency band, by increasing the width of the second antenna element to the maximum, the inductance component is reduced and the frequency band can be expanded. Furthermore, by reducing the distance between the first antenna element and the second antenna element, the degree of electromagnetic coupling between the two increases, and the first antenna element acts in the same way as a parasitic element, so the frequency band is expanded. Is possible.
In addition, the relationship between the first frequency band and the second frequency band is, for example, GSM (global system for mobile communication) (880 MHz to 960 MHz) and DCS (digital cellular system) (1710 MHz to 1880 MHz), or GSM and PCS ( personal communication service) (1850MHz to 1990MHz), that is, when the center frequency of the second frequency band is about twice or more than the center frequency of the first frequency band The second antenna element length is about ½ or less of the first antenna element length, and in the operation in the first frequency band, the resonant current is distributed on the first antenna element, and the second antenna element Almost no distribution above. For this reason, since adjustment of each antenna element length can be performed independently, workability | operativity improves. Note that the frequency band applied in the first frequency band and the second frequency band is not limited to the above, and the center frequency of the second frequency band is approximately twice the center frequency of the first frequency band, Alternatively, any combination may be used as long as it is more than that.

[Second Embodiment]
FIG. 2A is a perspective view showing a built-in antenna according to the second embodiment of the present invention. In the figure, parts that are the same as those of the first embodiment shown in FIG. 1 are given the same reference numerals, and redundant descriptions are omitted. The difference from the first embodiment shown in FIG. 1 of the present embodiment is that the shape of the horizontal portion 1 a of the first antenna element 1 is opposed to the horizontal portion 2 a of the second antenna element 2. It is the point made thin in the part which is not.
In operation in the first frequency band, by narrowing the tip of the first antenna element, it is possible to weaken electromagnetic coupling with the ground and expand the frequency band. By narrowing the tip, the inductance component of the first antenna element increases and acts in a direction that hinders the expansion of the frequency band of the antenna, but this effect is small because the resonance current at the tip of the element is small.
In addition, as for the shape which narrows the front-end | tip part of the horizontal part 1a, as shown to FIG. It is good also as a shape made thin.

[Third Embodiment]
FIG. 3A is a perspective view showing a main part of the built-in antenna according to the third embodiment of the present invention. In the figure, the portion below the feeder line is omitted. The difference of the present embodiment from the first embodiment shown in FIG. 1 is that the shape of the horizontal portion of the first antenna element 1 is curved. According to the present embodiment, the space in the housing can be utilized to the maximum when installed in a housing having a curved surface due to the design.
The shape of the resin block 3 is such that the entire surface other than the bottom surface is a curved surface as shown in FIG. 3B, or a partially curved surface as shown in FIG. 3C. May be.

[Fourth Embodiment]
FIG. 4 is a perspective view showing a built-in antenna according to a fourth embodiment of the present invention. In the figure, illustration of the substrate and the conductor pattern is omitted. The difference of the present embodiment from the first embodiment shown in FIG. 1 is that the vertical portion 2 b of the second antenna element 2 is shared with the vertical portion 1 b of the first antenna element 1. It is a point. According to the present embodiment, the structure can be simplified, so that a product can be provided at a lower cost.

[Fifth Embodiment]
FIG. 5A is a perspective view showing a built-in antenna according to the fifth embodiment of the present invention. In the figure, parts that are the same as those of the first embodiment shown in FIG. 1 are given the same reference numerals, and redundant descriptions are omitted. The present embodiment is different from the first embodiment shown in FIG. 1 in that a long and narrow slit 8 is inserted in the conductor pattern 7. That is, in the present embodiment, the slit 8 is on the side of the conductor pattern 7 facing the horizontal portion of the antenna element and on the side where the distance from the feeding point 5 to the corner of the conductor pattern 7 is short. It is put.
Normally, in the case of a mobile communication device using an inverted L-type built-in antenna, radiation from the current on the long side of the ground increases, but as shown in FIG. If there is a node 9 in the current, the radiation in that direction is weakened. On the other hand, in the present embodiment, a slit is provided, and the length of the antenna current is changed by changing the length of the ground circumference. It is possible to improve the radiation pattern on the side where the node of the antenna current was present (FIG. 5C). At this time, the movement destination of the current node is preferably a position where the contribution to the radiation is small, and is preferably on the ground side facing the antenna element in which the current that contributes little to the radiation is distributed. Therefore, it is preferable to place the slit on the ground side facing the antenna element, and to move the current node on this side. In particular, in the present embodiment, when the ground long side has a length of ¼ wavelength to ½ wavelength, a current node exists on the ground long side near the feeding point. In order to move to the opposite ground side, the slit is preferably arranged on the side where the distance from the feeding point to the corner of the ground is short.

  6 (a) and 6 (b) show the operation of the second frequency band when there is no slit, respectively, on the ground side facing the antenna element, and when the ground is viewed from the position of the feeding point. The calculation example of the radiation pattern Eθ when the slit is arranged on the side where the distance to the corner is short is shown. By arranging the slit and adjusting it to an appropriate slit length, radiation in the direction mainly surrounded by the dotted line in the figure is improved.

[Sixth Embodiment]
FIG. 7 is a perspective view showing a built-in antenna according to a sixth embodiment of the present invention. In the figure, parts that are the same as those of the first embodiment shown in FIG. 1 are given the same reference numerals, and redundant descriptions are omitted. In the built-in antenna of the first embodiment, the ground is the conductor pattern 7 formed on the substrate 6, whereas in the present embodiment, the ground is a metal box-shaped metal casing. 10, a conductor pattern 7 formed on the substrate 6 disposed inside the metal housing 10, and a conductive contact 11, and the metal housing 10 and the conductor pattern 7 of the substrate. Are electrically connected by a contact 11 near the feeding point 5.
In the configuration of the present embodiment, the metal casing 10 is used and connected to the ground pattern (7) of the substrate in the vicinity of the feeding point 5, so that the antenna current flowing to the ground starts from the contact and the conductor of the substrate. The current is divided into the pattern 7 and the metal casing 10. As a result, generation of an induced current on the metal casing is prevented, unnecessary resonance caused by this can be suppressed, and the metal casing can be used as a radiating element. The structure of the contactor is a structure having both conductivity and elasticity, such as a leaf spring structure, a spring pin structure, a gasket structure, and the like. Any structure that can provide mechanically stable contact may be used. The contact may be configured as a separate body from the conductor pattern and the metal housing, but may be fixed to either one. Further, the conductor pattern and the metal casing may be connected by a lead wire using a braided wire or the like instead of the contact.

  Although preferred embodiments have been described above, the present invention is not limited to these embodiments, and appropriate modifications can be made without departing from the scope of the present invention. For example, in the fifth and sixth embodiments, the slit and the metal casing are added to the built-in antenna of the first embodiment, but these may be added to the other embodiments. Good. In each embodiment, the long wavelength antenna element is disposed on the short wavelength antenna element. However, the short wavelength antenna element may be disposed on the upper side.

The perspective view which shows the internal antenna of the 1st Embodiment of this invention. The perspective view which shows the internal antenna of the 2nd Embodiment of this invention. The perspective view which shows the internal antenna of the 3rd Embodiment of this invention. The perspective view which shows the internal antenna of the 4th Embodiment of this invention. The perspective view which shows the internal antenna of the 5th Embodiment of this invention. The radiation pattern figure for demonstrating the effect of the 5th Embodiment of this invention. The perspective view which shows the internal antenna of the 6th Embodiment of this invention. The perspective view of a 1st prior art example. The perspective view of the 2nd prior art example. The perspective view of a 3rd prior art example.

Explanation of symbols

1, 101, 201, 301 First antenna element 1a, 2a Horizontal part 1b, 2b Vertical part 1c Hanging part 2, 102, 202, 302 Second antenna element 3 Resin block 4, 104, 204, 304 Feed line 5 , 105, 305 Feed point 6 Substrate 7 Conductor pattern 8 Slit 9 Node 10 Metal housing 11 Contactor 103 Antenna placement area 106, 306 Ground 203 Dielectric substrate 205 PCB
206 Grounding post 207 Matching bridge 301a First radiation conductor element 301b Second radiation conductor element 307 Short-circuit terminal

Claims (11)

A dual-band built-in antenna corresponding to the first frequency band and the second frequency band, which corresponds to about ¼ wavelength of the center frequency of each of the first frequency band and the second frequency band. First and second antenna elements each having a plate shape, each having a horizontal portion and a vertical portion, and a ground, the first antenna element and the second antenna element being a first antenna A built-in antenna characterized in that the horizontal portion of the element is placed on the upper side and the horizontal portion of the second antenna element is placed on the lower side, and is shared at a place serving as a feeding point. 2. The built-in antenna according to claim 1, wherein a center frequency of the second frequency band is about twice or more than a center frequency of the first frequency band. The horizontal portion of the first antenna element has a hanging portion bent in a direction approaching the second antenna element on both sides within a range facing the horizontal portion of the second antenna element. The built-in antenna according to claim 1 or 2. 2. The width of a portion of the horizontal portion of the first antenna element that is not opposed to the horizontal portion of the second antenna element is narrower than the width of the portion that is opposed. The built-in antenna according to any one of items 1 to 3. 5. The built-in antenna according to claim 1, wherein the horizontal portion of the first antenna element is formed in a curved shape having a center line in the longitudinal direction of the horizontal portion protruding. The ground includes a conductor pattern formed on the substrate, a plane on which the conductor pattern is formed, a plane on which the horizontal portion of the first antenna element is formed, and a horizontal portion of the second antenna element are formed. The built-in antenna according to claim 1, wherein the built-in antenna is orthogonal to the flat surface. The built-in antenna according to claim 6, wherein the conductor pattern has an elongated slit on a side facing the horizontal portion of the antenna element. The built-in antenna according to claim 7, wherein the slit is formed on a side where a distance to a corner of the conductor pattern is short when viewed from the position of the feeding point. The ground includes a conductor pattern formed on a substrate and a metal box-shaped metal housing that accommodates the substrate on which the conductor pattern is formed, and the conductor pattern and the metal housing are the feeding point. The built-in antenna according to claim 1, wherein the built-in antenna is electrically connected in the vicinity. The built-in antenna according to claim 9, wherein the conductor pattern and the metal casing are electrically connected by a contact. An electronic device having the built-in antenna according to claim 1.

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