JP2009124582A - Antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna which attains band widening so as to be available in frequency bands over a wide range. <P>SOLUTION: An antenna 100 includes a power feeding element 110 connected to a feeding point 101 and a radiation conductor 120 connected to a grounding point 102, wherein the radiation conductor 120 is folded at 180° at a folding part 123 and includes a first conductor side 121 and a second conductor side 122. The power feeding element 110 is disposed in such a way that its length is approximately equal to that of the first conductor side 121 and the second conductor side 122 and a tripartite distance becomes approximately equal. When the power feeding element 110 is excited, the first conductor side 121 and the second conductor side 122 are excited, and a band widened characteristic of the antenna 100 is easily achieved by triple resonance overlapping resonance therebetween. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a small antenna built in a portable terminal or the like, and more particularly to an antenna having a broadband characteristic.

  Along with the widespread use of terminal devices such as mobile phones and sophistication of their functions, the antennas built into the terminal devices have a wide band characteristic capable of supporting a wide range of frequencies as well as further miniaturization. Is required. For example, a terminal equipped with a digital television or the like is required to have a broadband characteristic of about 50% in a specific band. As an antenna having broadband characteristics, for example, an antenna described in Patent Document 1 is known.

  A perspective view of the antenna described in Patent Document 1 is shown in FIG. An antenna 900 shown in the figure has a ground electrode 902 formed on one main surface of a base body 901 made of a rectangular parallelepiped insulator, and is disposed opposite to the other main surface via a slit s1 provided obliquely. First and second radiation electrodes 903 and 904 are formed.

  The first radiating electrode 903 has an end close to one end of the slit s1 connected to the ground electrode 902 via the first connecting electrode 905, and connected to the first connecting electrode 905 of the first radiating electrode 903. A feeding electrode 907 is disposed at an end portion separated from the end portion via a gap g2. In addition, the second radiation electrode 904 is connected to the ground electrode 902 through the second connection electrode 906 at an end portion that is spaced apart from one end of the slit s1.

In the antenna 900 configured as described above, the first radiating electrode 903 is resonated by capacitive coupling with the feeding electrode 907, and the second radiating electrode 904 is resonated with the first connecting electrode 905 and the second connecting electrode 906. Can resonate via magnetic field coupling between the two. By obtaining the double resonance as described above, the antenna 900 can be widened in a predetermined frequency band.
JP 2000-151258 A

  However, the conventional antenna described in Patent Document 1 has the following problems. The antenna 900 of Patent Document 1 can be widened to some extent by double resonance, but it is difficult to realize a sufficient wide band. Moreover, since the two elements are arranged on the same plane, the area of the element tends to increase. Considering the size of the element added for widening the band (enhancement of the element area) and the obtained effect (band expansion), there is a problem that the effect of widening the band is not so great.

  Accordingly, the present invention has been made to solve the above-described problem, and an object of the present invention is to provide an antenna having a wide band so that excitation can be performed in a wide frequency band in a use frequency band.

  A first aspect of the antenna of the present invention is an antenna capable of supporting a wide band, and is parallel to a feed element connected to a feed point and one end connected to a ground point and folded at 180 degrees by at least one folded portion. The radiation conductor and the feed element are arranged in parallel and close to each other, and the total length of the radiation conductor is longer than the total length of the feed element.

  Another aspect of the antenna of the present invention is characterized in that the length of the radiation conductor is determined in accordance with a predetermined resonance frequency.

  Another aspect of the antenna of the present invention is characterized in that the radiating conductor is folded at a position that is substantially half the total length.

  Another aspect of the antenna of the present invention is characterized in that each conductor side of the folded radiation conductor and the feeding element have substantially the same length.

  In another aspect of the antenna of the present invention, the distance between the conductor sides of the folded radiation conductor and the distance between each of the conductor sides and the feed element are all substantially equal. Features.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the antenna by which the broadband was achieved so that it could be used in the frequency band of a wide range in a use frequency band.

  An antenna according to a preferred embodiment of the present invention will be described in detail with reference to the drawings. In addition, about each structural part which has the same function, the same code | symbol is attached | subjected and shown for simplification of illustration and description.

  An antenna according to an embodiment of the present invention will be described in detail with reference to FIG. FIG. 1A shows a schematic diagram of the antenna 100 of the present embodiment, and FIG. 1B shows a cross-sectional view along the A-A ′ plane in FIG. The antenna 100 according to this embodiment includes a feeding element 110 connected to a feeding point 101 and a radiation conductor 120 connected to a ground point 102.

  As shown in FIG. 1A, the radiating conductor 120 is folded back 180 degrees by a folded portion 123 to form a first conductor piece 121 and a second conductor side 122. The first conductor piece 121 and the second conductor piece 122 are arranged so as to be in parallel with each other in proximity to each other. In the present embodiment, the first conductor side 121 and the second conductor side 122 are folded back so that their lengths are substantially equal.

  The power feeding element 110 is disposed in parallel with the first conductor piece 121 and the second conductor piece 122, and the distance between the two is shortened. The length of the feeding element 110 is configured to be shorter than the length of the radiation conductor 120, that is, the total length of the first conductor side 121, the second conductor side 122, and the folded portion 123. The

  In the present embodiment, the length of the power feeding element 110 is set to be approximately equal to the length of each of the first conductor piece 121 and the second conductor piece 122. As a result, the radiation conductor 120 has a length about twice that of the feed element 110. The length of the radiation conductor 120 is determined corresponding to a predetermined resonance frequency.

  In the cross-sectional view shown in FIG. 1B, cross sections of the first conductor piece 121 and the second conductor piece 122 of the radiating conductor 120 and the feeding element 110 are shown, and their relative positional relationships are shown. Is shown. As shown in the figure, in this embodiment, the first conductor piece 121, the second conductor piece 122, and the feeding element 110 are arranged so that the distances between them are substantially equal. Depending on the case, the distance can be approximately 1/100 wavelength or less with respect to the wavelength corresponding to the use center frequency.

  In the antenna 100 of the present embodiment configured as described above, when the feed element 110 connected to the feed point 101 is excited, the radiating element 120 is excited by electromagnetic coupling with the feed element 110. At this time, the radiating conductor 120 resonates in the lowest frequency region, the feeding element 110 itself resonates in the higher frequency region, and harmonics are excited on the radiating conductor 120 in the higher frequency region. The

  Normally, even when a sufficient distance can be ensured between the feeding element and the parasitic element, even if the structure operates normally, a plurality of resonance modes can be obtained when they are arranged close to each other, but each mode is switched. In the frequency, a mode for canceling the current is interposed between the elements. For this reason, even if it seems to be a wide band at first glance, a region where the radiation efficiency is extremely reduced is formed in the frequency band where the mode is switched. However, in this embodiment, since each resonance mode continuously changes on the frequency axis, a very wide band resonance characteristic obtained by superimposing three resonances can be obtained, and at the same time, the element sides are arranged close to each other. It becomes possible to do.

  In the antenna 100 according to the present embodiment having a wide band as described above, the impedance adjustment of the system is performed between, for example, the first conductor side 121, the second conductor side 122, and the feeding element 110 that are arranged close to each other. This can be done by adjusting the distance. Further, it is possible to adjust the impedance of the system by arranging the feeding point 101 and the grounding point 102 at close positions.

  The broadband characteristics of the antenna 100 of this embodiment will be described with reference to FIG. FIG. 2 shows an example of the VSWR characteristic of the antenna 100 with respect to the frequency. In the antenna 100 of this embodiment, the length of the radiation conductor 120 is determined so that resonance on the low frequency side can be obtained in the 1.0 GHz band (hereinafter referred to as the first resonance frequency band). That is, the total length is determined so that the resonance that occurs over the entire length of the radiation conductor 120 is in the first resonance frequency band. Further, the VSWR is rapidly increased on the low frequency side from the first resonance frequency, and the antenna 100 is not radiated on the low frequency side.

  On the other hand, on the high frequency side, resonance is obtained in a 1.9 GHz band (hereinafter referred to as a second resonance frequency band) which is a higher mode of the radiation conductor 120. The VSWR is rapidly increased on the higher frequency side than the second resonance frequency band of the higher-order mode, and the antenna 100 is not radiated on the higher frequency side.

  Between the first resonance frequency band and the second resonance frequency band, the resonance in the first resonance frequency band is continuously changed from the resonance in the first resonance frequency band through the resonance of the radiation conductor 120. Transition. As a result, resonance is obtained even between the first resonance frequency band and the second resonance frequency band, and a suitable VSWR characteristic is obtained.

  In the antenna 100 of this embodiment, the resonance frequency of the higher-order mode in the radiation conductor 120 is changed by adjusting the distance between the first conductor side 121 and the second conductor side 122 of the feed element 110 and the radiation conductor 120. it can. As a result, the broadband characteristic described with reference to the VSWR characteristic of FIG. 2 is achieved. In the embodiment shown in FIG. 2, a broadband characteristic with a specific band of about 60% is achieved.

  One embodiment of the antenna of the present invention is shown in FIG. Similar to the antenna 100 of the above-described embodiment, the antenna 200 of the present example includes a feeding element 210 connected to the feeding point 201 and a radiation conductor 220 connected to the ground point 202. The feed element 210 and the radiation conductor 220 drawn from the feed point 201 and the grounding point 202 are bent by approximately 90 degrees in a direction parallel to the end side 203a of the ground plane 203 at a position away from the ground plane 203 by a predetermined distance. .

  The radiating conductor 220 is folded 180 degrees at the folded portion 223 to form a first conductor side 221 and a second conductor side 222. The first conductor side 221 and the second conductor side 222 are folded back so that their lengths are substantially equal, and are arranged so that they are close to each other and parallel to each other.

  The feed element 210 is formed to have substantially the same length as each of the first conductor side 221 and the second conductor side 222, and is disposed in close proximity to and parallel to the first conductor side 221 and the second conductor side 222. ing. The length of the radiation conductor 220 is determined corresponding to a predetermined resonance frequency. In this example, by setting the total length of the radiation conductor 220 to 46 mm, a wideband resonance frequency from 900 MHz to 2 GHz as shown in FIG. 2 could be realized.

  In the antenna 200 of this embodiment, in order to keep the distance between the three conductors of the feeding element 210, the first conductor side 221 and the second conductor side 222 constant, an element fixing base as shown in FIG. 230 is used. The element fixing base 230 fixes the feeding element 210 at the center and the radiation conductor 220 at the outer periphery thereof. In the present embodiment, the cross section (cross section viewed from the direction of arrow B) formed by the feeding element 210 and the radiation conductor 220 is 1.2 mm × 1.2 mm.

  Also in the antenna 200 of the present embodiment, when the feed element 210 connected to the feed point 201 is excited, the radiating element 220 is excited by electric field coupling and magnetic field coupling with the feed element 210. Thereby, three resonances are obtained between the feeding element 210 and the radiating element 220, and a triple resonance obtained by superimposing these three resonances is easily obtained. By such triple resonance, the broadband characteristics of the antenna 200 can be obtained.

  Another embodiment of the antenna of the present invention is shown in FIG. The antenna 300 of the present embodiment includes a feed element 310 connected to a feed point (not shown) and a radiation conductor 320 connected to a ground point (not shown). The radiation conductor 320 is folded back 180 degrees at the folded portion 323 to form a first conductor side 321 and a second conductor side 322. The first conductor side 321 and the second conductor side 322 are folded back so that their lengths are substantially equal, and are disposed so as to be parallel to each other.

  In this embodiment, a core wire of a coaxial cable is used as the feeding element 310. That is, the protective layer and the outer conductor of the coaxial cable are removed, and the dielectric 330 inside thereof and the core wire passing through the center thereof are used. The core wire is a feed element 310, and the radiation conductor 320 is disposed on the outer periphery of the dielectric 330.

  In the antenna 300 of this embodiment, in order to make the distance between the three conductors of the feeding element 310, the first conductor side 321, and the second conductor side 322 equal, Instead, a coaxial cable dielectric 330 is used. Thereby, the distance between the three conductors of the power feeding element 310, the first conductor side 321 and the second conductor side 322 can be kept parallel and constant.

  As described above, by using the coaxial cable core wire 310 and the dielectric 330 on the outer periphery thereof and disposing the radiation conductor 320 on the outer periphery of the dielectric 330, the broadband antenna 300 can be easily provided. By processing and using the coaxial cable, it is possible to easily realize a parallel and equal distance between the feeding element 310 and the conductor sides 321 and 322 of the radiation conductor 320. In any case, since the cross section of the antenna can be reduced in size, a configuration suitable for disposing in a limited gap in the housing in a small communication device such as a cellular phone can be obtained.

  Note that the description in this embodiment mode shows an example of the antenna according to the present invention, and the present invention is not limited to this. The detailed configuration and detailed operation of the antenna in this embodiment can be changed as appropriate without departing from the spirit of the present invention.

It is the plane schematic diagram and sectional drawing of the antenna which concern on embodiment of this invention. It is a figure which shows an example of the VSWR characteristic with respect to the frequency of the antenna of this embodiment. It is a perspective view which shows one Example of the antenna of this invention. It is a perspective view which shows an element fixing stand. It is a top view which shows another Example of the antenna of this invention. It is a perspective view of the conventional antenna.

Explanation of symbols

100, 200, 300, 900 Antenna 101, 201 Feed point 102, 202 Ground point 110, 210, 310 Feed element 120, 220, 320 Radiation conductor 121, 221, 321 First conductor side 122, 222, 322 Second Conductor sides 123, 223, 323 Folded portion 203 Base plate 230 Element fixing base 330 Dielectric 901 Base 902 Ground electrode 903 First radiation electrode 904 Second radiation electrode 905 First connection electrode 906 Second connection electrode 907 Feed electrode

Claims (5)

An antenna capable of supporting a wide band,
A feed element connected to the feed point;
A radiation conductor having one end connected to a ground point and folded 180 degrees at at least one folded portion and arranged in parallel, and
The antenna, wherein the radiating conductor and the feeding element are arranged close to each other in parallel, and an overall length of the radiating conductor is longer than an entire length of the feeding element. The antenna according to claim 1, wherein the length of the radiation conductor is determined in accordance with a predetermined resonance frequency. The antenna according to claim 1 or 2, wherein the radiating conductor is folded at a position that is approximately half the total length. The antenna according to any one of claims 1 to 3, wherein each conductor side of the folded radiation conductor and the feed element have substantially equal lengths. The distance between the conductor sides of the folded radiation conductor and the distance between each of the conductor sides and the power feeding element are all substantially equal to each other. The antenna according to claim 1.

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