JP4948373B2 - antenna - Google Patents

Description

  The present invention relates to an antenna built in a portable terminal or the like, and more particularly, to a multi-frequency antenna having a small size and wideband characteristics.

  With the spread of terminal devices such as mobile phones and the sophistication of their functions, the antenna built into the terminal devices has a multi-frequency sharing characteristic that can handle multiple frequencies as well as further miniaturization. Things are sought. For example, in mobile phone applications, in addition to the conventional function addition, international roaming, etc., the frequency band to be used is steadily expanding, such as shifting to the third generation or coexistence. That is, there is a demand for a conventional multi-frequency antenna that has a very wide frequency band. As a conventional antenna for widening a use frequency band, 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 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. In addition, there is a problem that it is difficult to obtain multi-frequency shared characteristics that can be used in two or more frequency bands at the same time. Furthermore, since the two elements are arranged on the same plane, the area of the element tends to increase. In consideration of the size of the added element (expansion of the element area) and the obtained effect (expansion of band) in order to increase the bandwidth, there is a problem that the effect of increasing the bandwidth is not so great.

  Therefore, the present invention has been made to solve the above problems, and can sufficiently excite a low frequency band by a very small excitation element compared to the wavelength, and in the high frequency band as compared with the case of direct power feeding, An object of the present invention is to provide an antenna for multi-frequency use with a significantly widened bandwidth.

A first aspect of the antenna of the present invention is an antenna that can handle two or more frequency bands, an excitation element connected to a feeding point, and an excited element connected to a ground point and having a branch point. The driven element is wired in a direction different from the first radiating conductor from the branch point, and at least the entire length of the driven element is greater than that of the first radiating conductor. A long second radiating conductor, and at least the first radiating conductor is disposed in close proximity to and substantially parallel to the excitation element to form a first capacitive coupling portion, and the excited element is the first radiating conductor. The first radiating conductor has a folded portion that is turned back by 180 °, and the total length of the first radiating conductor is longer than the total length of the excitation element .

  Another aspect of the antenna of the present invention is characterized in that the feeding point and the grounding point are arranged close to each other, and the excitation element and the first radiation conductor are wired in substantially the same direction. To do.

  In another aspect of the antenna of the present invention, the first radiating conductor and the second radiating conductor are wired in opposite directions at or near the branch point, and the second radiating conductor is folded 180 degrees. It has at least two folded portions and is wired so as to surround the outer periphery of the first capacitive coupling portion.

  Another aspect of the antenna of the present invention is characterized in that the first radiating conductor and the second radiating conductor each have a second capacitive coupling portion arranged in close proximity to each other in parallel. To do.

  Another aspect of the antenna of the present invention is characterized in that the excitation element and the excited element are disposed on a dielectric surface or inside.

  Another aspect of the antenna of the present invention is characterized in that a portion forming the first capacitive coupling portion is disposed on or in the first dielectric surface.

  According to another aspect of the antenna of the present invention, the portion that forms the first capacitive coupling portion is disposed on or inside the first dielectric surface, and the portion that forms the second capacitive coupling portion is the first It is characterized in that it is arranged on the surface of or inside the two dielectrics.

  Another aspect of the antenna of the present invention is characterized in that in the second radiating conductor, a portion excluding the second capacitive coupling portion is disposed on or in the third dielectric surface.

  Another aspect of the antenna of the present invention is characterized in that a relative dielectric constant of the first dielectric is higher than that of the second dielectric and the third dielectric.

  According to the present invention, a sufficient frequency can be obtained by a very small excitation element in comparison with a wavelength in a low frequency band, and a wide band can be obtained in a high frequency band compared with direct feeding. Can be provided.

  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.

(First embodiment)
FIG. 1 shows a plan view of an antenna according to a first embodiment of the present invention. The antenna 100 of the present embodiment is an antenna that can handle two or more frequency bands, and includes an excitation element 110 and an excited element 111. The excited element 111 includes a branch point 111a, a first radiating conductor 120, and A second radiation conductor 130.

  The excitation element 110 is connected to the feeding point 101, and the excited element 111 is connected to the ground point 102. Furthermore, both the first radiation conductor 120 and the second radiation conductor 130 are connected to the branch point 111a. The feeding point 101 and the grounding point 102 are arranged in close proximity.

  The first radiating conductor 120 and the second radiating conductor 130 are wired in different directions immediately after branching so as not to affect each other, and are preferably wired in opposite directions.

  The first radiating conductor 120 has one folded portion 121 that is folded by 180 °, and a part of the conductor piece (first portion) 122 (in this embodiment, the front end side of the first radiating conductor 120) is excited. The elements 110 are arranged close to each other in parallel. Thus, in order to be able to arrange the excitation element 110 in parallel with the conductor piece 122 of the first radiation conductor 120, the excitation element 110 may be bent and arranged as necessary. (In FIG. 1, it is bent 90 degrees from the feeding point 101).

  The second radiating conductor 130 has two folded portions 131 and 132 that are folded back by 180 °, and a part of the conductor piece (third part) 133 is another part of the first radiating conductor 120. The conductor piece (second portion) 123 is arranged in close proximity to each other. The second radiating conductor 130 is formed of a conductor longer than the first radiating conductor 120, and is disposed so as to surround a portion constituted by the first radiating conductor 120 and the excitation element 110.

When the excitation element 110 and the first portion (return path) 122 of the first radiating conductor 120 are arranged close to each other, the first capacitive coupling portion 120a is formed therebetween, and when the excitation element 110 is excited. The first radiation conductor 120 is excited by capacitive coupling.
By forming the first capacitive coupling portion in this way, not only resonance is obtained in the frequency band corresponding to the length of the first radiation conductor, but also the band over a wide region on the high frequency side from the resonance frequency. It becomes possible to enlarge.
Furthermore, it is possible to obtain a plurality of bands by changing the positional relationship of the proximity arrangement.

Next, by arranging the second portion 123 of the first radiating conductor 120 and the third portion 133 of the second radiating conductor 130 in close proximity, the second capacitive coupling portion 130a is formed therebetween. When the first radiation conductor 120 is excited, the second radiation conductor 130 is excited by capacitive coupling.
By forming the second capacitive coupling portion in this way, the second radiating conductor 130 can obtain resonance at a lower frequency side, and in the first frequency band according to the capacitance to be formed. It is also possible to change the input impedance.

In order to further increase the bandwidth, it is desirable that the first radiating conductor 120, which is a radiating conductor, be formed shorter than the second radiating conductor 130.
The first radiation so that resonance is obtained at the lowest frequency of the second frequency band when the low frequency side use frequency band is the first frequency band and the high frequency side use frequency band is the second frequency band. The length of the conductor 120 is suitably set, and the length of the second radiation conductor 130 is suitably set so that resonance is obtained in the first frequency band.

  In the antenna 100 of the present embodiment configured as described above, the first radiating conductor 120 that is not directly connected to the feed point is excited by capacitive coupling with the excitation element 110 and is not connected directly to the feed point. The second radiating conductor 130 is excited by capacitive coupling with the first radiating conductor 120, and operates as a high frequency band radiating conductor, a low frequency band radiating conductor, and a high frequency band radiating conductor, respectively.

  The band characteristics of the antenna 100 of this embodiment will be described using the Smith chart shown in FIG. FIG. 2 shows the reflection coefficient of the antenna 100 on the Smith chart. Here, the first frequency band on the low frequency side is a band centered at about 0.9 GHz, and the second frequency band on the high frequency side is a wide band of about 2 GHz or more.

  As shown in FIG. 2, the antenna 100 of this embodiment has a suitable reflection characteristic at about 0.9 GHz in the first frequency band, and the second radiation conductor 130 for the low frequency band is sufficiently excited. I understand that. In addition, in the second frequency band of about 2 GHz or more, frequency trajectories are concentrated in a region having a low reflection coefficient over a very wide frequency range of about 2 GHz to 3.6 GHz, and a good wideband characteristic is obtained. It turns out that it is obtained.

  As described above, according to the antenna 100 of the present embodiment, capacitive coupling between the excitation element 110 and the first radiation conductor 120 and between the first radiation conductor 120 and the second radiation conductor 130 are performed. Capacitive coupling enables a wide band on the high-frequency side compared to direct feed, and multi-frequency sharing that can provide sufficient excitation even in the low-frequency band despite the use of minute excitation elements. An antenna can be provided.

(Second Embodiment)
An antenna according to the second embodiment of the present invention is shown in FIG. FIG. 3 shows a perspective view of the antenna 200 of the present embodiment. The antenna 200 of the present embodiment is also an antenna that can handle two or more frequency bands, and includes an excitation element 210 and an excited element 211, and the excited element 211 includes a first radiation conductor 220 and a second radiation. And a conductor 230.

  The excitation element 210 is connected to a feeding point (not shown), the excited element is connected to a ground point, and a first radiating conductor 220 and a second radiating conductor 230 are configured from the branch point 211a. Also in this embodiment, the first radiating conductor 220 and the second radiating conductor 230 are wired in different directions after branching.

  The first radiation conductor 220 has one folded portion 221 that is folded by 180 °, and a part of the conductor piece (first portion) 222 is disposed in parallel and close to the excitation element 210. Further, the second radiation conductor 230 has two folded portions 231 and 232 that are folded back by 180 °, and a part of the conductor piece (third part) 233 is another part of the first radiation conductor 220. The conductor piece (second portion) 223 is disposed close to and parallel to the longitudinal direction.

  By configuring as described above, the antenna 200 of the present embodiment also forms the first capacitive coupling portion 220a and the second capacitive coupling portion 230a. The first radiating conductor 220 that is not directly connected to the feeding point is excited by capacitive coupling with the excitation element 210, and the second radiating conductor 230 that is also not directly connected to the feeding point is the first radiating conductor 220. Are operated as a high-frequency band radiation conductor, a low-frequency band radiation conductor, and a high-frequency band radiation conductor, respectively.

  The antenna 200 of the present embodiment has the same configuration as the antenna 100 of the first embodiment, and in addition, the excitation element 210 and the first radiating conductor 220 are placed on the first dielectric 241. The second radiating conductor 230 is mounted on the second dielectric 242. A first dielectric 241 having a relatively high dielectric constant is used, and a second dielectric 242 having a relatively low dielectric constant is used.

  By using the first dielectric 241 and the second dielectric 242 described above, the capacitive coupling in the first capacitive coupling unit 220a and the second capacitive coupling unit 230a can be enhanced, respectively. At the same time, the capacitive coupling portion 220a can be greatly reduced in size.

  As an example of the characteristics of the antenna 200 of the present embodiment, VSWR characteristics are shown in FIG. In the figure, for comparison, the VSWR of a conventional antenna 800 that performs direct power feeding is also shown. A perspective view of a conventional antenna 800 is shown in FIG. In the antenna 800, the first radiating conductor 820 and the second radiating conductor 830 are both connected to a feeding point and a grounding point (not shown) via a feeding line 801 and a grounding line 802, and have an inverted F antenna structure. ing.

  In FIG. 4, the VSWR of the antenna 200 of this embodiment is indicated by reference numeral 10, and the VSWR of the conventional antenna 800 is indicated by reference numeral 11. In the figure, comparing the VSWR 10 of the antenna 200 of the present embodiment and the VSWR 11 of the conventional antenna 800, it is shown that the same bandwidth is secured in the low frequency band. On the other hand, in the high frequency band, the antenna 200 of the present embodiment has a significantly wider band. That is, the antenna 200 of the present embodiment has a suitable VSWR characteristic in a wide band from about 2 GHz to at least 3.6 GHz. On the other hand, the conventional antenna 800 only has the required reflection characteristics in a narrow frequency band corresponding to a specific resonance mode.

  By the way, in the antenna 200 of this embodiment, the excitation element 210 and the first radiation conductor 220 are placed on the first dielectric 241, and the second radiation conductor 230 is placed on the second dielectric 242. It was placed. In this embodiment, it is also possible to arrange the excitation element 210 and the excited element 211 so as to be included in a dielectric. An example in which the excitation element 210 and the driven element 211 are included in a dielectric is shown in FIG.

  In the antenna 200 ′ shown in FIG. 6, the excitation element 210 and the first radiating conductor 220 are included in the first dielectric 241, and the second radiating conductor 230 is included in the second dielectric 242. Thereby, the capacitive coupling in the first capacitive coupling unit 220a and the second capacitive coupling unit 230a can be enhanced, and the antenna 200 'can be downsized.

  In the above description, the first dielectric 241 having a relatively high dielectric constant and the second dielectric 242 having a relatively low dielectric constant are used. However, the present invention is not limited thereto. The first capacitive coupling portion 220a is placed or included on the first dielectric, the second capacitive coupling portion 230a is placed or contained on the second dielectric, and the second radiation conductor second The portion excluding the capacitive coupling portion 230a may be placed on or included in the third dielectric. In this case, it is preferable to use a material having a relative dielectric constant of the first dielectric higher than that of the second dielectric and the third dielectric. In addition, the relative dielectric constant of the second dielectric is preferably higher than the relative dielectric constant of the third dielectric.

  In still another embodiment, the excitation element 210, the first radiating conductor 220, and the second radiating conductor 230 may be configured to all be placed on the same dielectric.

  As described above, also in the antennas 200 and 200 ′ of this embodiment, the capacitive coupling between the excitation element 210 and the first radiating conductor 220 and the first radiating conductor 220 and the second radiating conductor 230 are the same. Due to the capacitive coupling between them, it is possible to provide a wideband antenna capable of exciting in a wide frequency band in the high frequency band and providing a multi-frequency antenna capable of obtaining sufficient excitation in the low frequency band.

  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.

1 is a plan view of an antenna according to a first embodiment of the present invention. It is a Smith chart which shows the band characteristic of the antenna of 1st Embodiment. It is a perspective view of the antenna which concerns on the 2nd Embodiment of this invention. It is a figure which shows the VSWR characteristic of the antenna of 2nd Embodiment. It is a perspective view of the conventional antenna. It is a perspective view which shows another Example of the antenna which concerns on 2nd Embodiment. It is a perspective view of the conventional antenna.

Explanation of symbols

100, 200, 200 ', 800, 900 Antenna 101 Feeding point 102 Grounding point 110, 210 Exciting element 111, 211 Excited element 111a, 211a Branch point 122, 222 First part 123, 223 Second part 133, 233 Third portions 121, 131, 132, 221, 231, 232 Folded portions 120, 220 First radiation conductors 120a, 220a First capacitive coupling portions 130, 230 Second radiation conductors 130a, 230a Second capacitive coupling Part 241 First dielectric 242 Second dielectric 801 Feed line 802 Ground line 901 First element 901
902 second element 902
903 Folding part 904 Power feeding part 905 Grounding part

Claims (9)

An antenna that can handle two or more frequency bands,
An excitation element connected to the feed point;
An excited element connected to a ground point and having a branch point;
The excited element is wired with a first radiating conductor connected to the branch point in a direction different from the first radiating conductor from the branch point, and has at least a total length longer than that of the first radiating conductor. Two radiating conductors,
At least the first radiation conductor is disposed close to and substantially parallel to the excitation element to form a first capacitive coupling portion, and the excited element is excited via the first capacitive coupling portion ;
The first radiating conductor has a folded portion that turns back 180 °, and the total length of the first radiating conductor is longer than the total length of the excitation element;
An antenna characterized by that. The feeding point and the grounding point are arranged close to each other,
The antenna according to claim 1 , wherein the excitation element and the first radiation conductor are wired in substantially the same direction. The first radiation conductor and the second radiation conductor are wired in opposite directions at or near the branch point,
Said second radiation conductor has at least two folded portions folded back 180 degrees, claim 1 or 2, characterized in that it is wired so as to surround the outer periphery of said first capacitive coupling portion The antenna according to item 1. Said first radiating conductor and said second radiating conductor, antenna according to claim 1 to 3, characterized in that it has a second capacitive coupling portion disposed proximate substantially parallel to each other . The antenna according to any one of claims 1 to 4 , wherein the excitation element and the excited element are disposed on a dielectric surface or inside. It said first portions to form a capacitive coupling portion, the first antenna according to any one of claims 1 to 4 that is characterized in that the dielectric is disposed surface or inside. A portion forming the first capacitive coupling portion is disposed on or in the first dielectric surface;
5. The antenna according to claim 4 , wherein a portion forming the second capacitive coupling portion is disposed on or in the second dielectric surface. 8. The antenna according to claim 7 , wherein a portion of the second radiation conductor excluding the second capacitive coupling portion is disposed on the third dielectric surface or inside. The antenna according to claim 8 , wherein a relative dielectric constant of the first dielectric is higher than that of the second dielectric and the third dielectric.

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