JP2009076961A - Antenna apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna apparatus which is operative in a plurality frequency bands. <P>SOLUTION: The antenna apparatus 101 includes: a ground conductor; a first antenna element 201 in an inverted L shape which operates at resonance frequencies of a basic mode and a higher-order mode; a feeding point 50 provided between the ground conductor and first antenna element 201; a second antenna element 202 which has one end coupled to a shorter side of the first antenna element 201 and forms an inverted L shape between the second antenna element 202 and feeding point 50; and a third antenna element 203 which has one end coupled to the shorter side of the first antenna element 201 and forms an inverted L shape between the second antenna element 202 and feeding point 50. The second antenna element 202 has two switches 301 and 302 to change the antenna length and is prevented from affecting the first antenna element 201 as the switches are turned on and off, so that the antenna apparatus 101 can operate with the plurality of frequency bands. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an antenna device, and more particularly to a broadband tunable antenna for a mobile terminal that can operate in a plurality of different frequency bands.

  In recent years, wireless communication systems have been used for various purposes, and wireless communication terminals are often equipped with a plurality of wireless communication systems. It is desirable to apply a small antenna capable of operating in a plurality of frequency bands to such a wireless communication terminal. Therefore, development of such an antenna device is underway.

  Examples of antennas that operate in a plurality of different frequency bands include tunable antennas described in Patent Documents 1 to 3. The planar inverted-F antenna described in Patent Document 1 can variably use a plurality of frequency bands by switching a plurality of external lines with a switch and connecting to the antenna. In addition, the antenna described in Patent Document 2 can variably use a plurality of frequency bands by switching a short-circuit portion of one element of the inverted F antenna and a short-circuit portion of the other element with a switch.

In the antenna described in Patent Document 3, a variable impedance circuit is provided on the antenna conductor, and the current flowing through the ground plane is changed by changing the impedance to switch the radiation pattern and the resonance frequency.
US Patent Publication No. US2003 / 0142022 US Patent Publication No. US2004 / 0075611 JP 2006-5756 A

According to conventional tunable antennas as described in Patent Documents 1 to 3, use in a plurality of frequency bands is possible.
However, in the case of an antenna that changes the frequency band to be used by switching the external line with a switch, it is necessary to provide an external line and a switch according to the number of frequency bands. It will increase in size.

  In addition, in the case of an antenna configured to switch the short-circuit portion, the connection between the end of the antenna element corresponding to the operating frequency band and the ground plane is switched by a switch. This makes it difficult to increase the complexity of the structure and the size of the antenna.

  Furthermore, in the case of an antenna configuration in which a variable impedance circuit is provided on a T-shaped antenna conductor, if the number of frequency bands to be used increases, a plurality of switches are required on the antenna conductor. Will lead to an increase in size.

  Therefore, in view of these problems, the present invention is an antenna that can operate in a plurality of frequency bands from a frequency band corresponding to each mode of a wireless communication system, that is, from a low frequency band such as a GSM band to a high frequency such as a UMTS band. An object is to provide an apparatus.

  In order to achieve the above object, an antenna device provided by the present invention includes a ground conductor, a relatively short first side, and a relatively long second side, and operates at a resonance frequency of a fundamental mode and a higher mode. A first L-shaped first antenna element, a feeding point provided between the ground conductor and the first side of the first antenna element, and one end coupled to the first side of the first antenna element are connected to the first side. And a second antenna element that forms an inverted L shape between the antenna element and the feeding point. The second antenna element includes a first switch that can selectively change the antenna length of the second antenna element, and a second switch that selectively connects the feeding point and the second antenna element. . This antenna device operates in different frequency bands according to opening and closing of the first and second switches.

  The antenna device further includes third to nth antenna elements having one end coupled to the first side of the first antenna element and forming an inverted L shape between the second antenna element and the feeding point. Also good.

  Further, the antenna device further provided by the present invention includes an earthed conductor, a relatively short first side, and a relatively long second side, and an inverted L shape that operates at a resonance frequency of a fundamental mode and a higher mode. The first antenna element, a feeding point provided between the ground conductor and the first antenna element, and one end coupled to the first side of the first antenna element, the first antenna element and the feeding point, And a second antenna element that forms an inverted L shape. The second antenna element includes a first switch that selectively connects only one of the first and second antenna elements to the feeding point and does not connect the other to the coupling portion with the first side of the first antenna. Have. The first antenna element has a second switch that selectively changes the antenna length of the first antenna element. This antenna device operates in different frequency bands according to opening and closing of the first and second switches.

  The antenna device further includes third to nth antenna elements that are coupled at one end to the first side of the first antenna element and form an inverted L shape between the second antenna element and the feeding point. Good.

  Further, in these antenna devices, each antenna element may be formed on the surface of a rectangular parallelepiped dielectric to constitute the antenna device in three dimensions. Each antenna element may be bent.

  According to the present invention, it is possible to realize a small antenna device having multiband characteristics that operate variably in a plurality of frequency bands used in a wireless communication system.

Preferred embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a configuration of an antenna device according to a first embodiment of the present invention. In this embodiment, the antenna device 101 is a feeding point that feeds power to the first antenna element 201, the second antenna element 202, the third antenna element 203, and the ground conductor (not shown), each of which has an inverted L shape. 50. The second antenna element 202 and the third antenna element 203 have one end coupled to a relatively short side of the first antenna element 201 to form an inverted L shape.

  The first antenna element 201 operates at two resonance frequencies, a fundamental mode and a higher order mode. The second antenna element 202 includes a first switch 301 that selectively changes the antenna length of the second antenna element 202, and a second switch 302 that selectively connects the second antenna element 202 to the feeding point 50. Have.

  FIG. 2 shows a specific example of the antenna device 101, which is miniaturized by bending the first antenna element 201 and the second antenna element 202 into a three-dimensional configuration. In the antenna device 101, for example, the first antenna element 201 is bent at four locations, but has an inverted L shape as a whole. As shown in the figure, a feeding point 50 is provided between the antenna element and the ground conductor 40. In FIG. 2, the first switch 301 and the second switch 302 are shown as gaps, but a semiconductor switch, FET, or the like is actually applied to this portion to enable on / off.

  FIGS. 3A, 3B, and 3C show examples of the frequency characteristics of the VSWR according to ON / OFF of the first switch 301 and the second switch 302 in the antenna device 101, that is, the closed state or the open state. Has been. Here, the characteristic impedance is 50Ω. 3A shows a case where both the first switch 301 and the second switch 302 are in an on state. FIG. 3B shows a case where the first switch 301 is in an off state and the second switch 302 is in an on state. FIG. 3C shows the case where both the first switch 301 and the second switch 302 are in the OFF state. In each figure, the resonance frequency band in which each mode operates is shown along with the mode names of various communication systems. It is shown as a band.

  The inverted L-shaped antenna disposed on the ground conductor operates at a frequency at which the antenna length is 1 / 4λ. In the antenna device 101 shown in FIG. 1, when both the first switch 301 and the second switch 302 are in the on state, the first antenna element 201 has a resonance frequency of approximately 900 MHz in the fundamental mode and approximately 2.7 GHz in the higher-order mode. Works with. The second antenna element 202 operates at approximately 1.8 GHz, and the third antenna element 203 operates at approximately 3.5 GHz (FIG. 3A).

  When the first antenna element 201 operates in the higher-order mode in the antenna device 101, if the second second antenna element 202 is connected, a shift occurs in the resonance frequency of the first antenna element 201 from around 2.7 GHz. Come off. In order to prevent this, the antenna device 101 disconnects the second antenna element by turning off the second switch 302, and maintains the resonance of the first antenna element 201 in the vicinity of 2.7 GHz (FIG. 3C).

  In order to make the antenna capable of supporting a wider frequency band, the antenna device 101 can operate at both the resonance frequency of the first antenna element 201 near 2.7 GHz and the resonance frequency of the second antenna element 202 near 1.8 GHz. Is desirable. Therefore, in the present embodiment, the second antenna element 202 is not affected when the first antenna element 201 operates in the higher-order mode by switching the second switch 302.

  On the other hand, the first switch 301 is provided to change the antenna length of the second antenna element 202. In other words, the resonance frequency of the second antenna element 202 is finely adjusted by opening and closing the first switch 301 (FIG. 3B).

  Referring to FIGS. 3A, 3B, and 3C, the antenna apparatus 101 according to the present embodiment is configured such that the GSM850, GSM900, DCS, PCS, UMTS2000, UMTS2600, It can be seen that operation is possible at all resonance frequencies of m-WiMAX. That is, it can be seen that all the frequency bands used in the current mobile phone can be covered by one antenna device 101.

Next, an antenna device according to a second embodiment of the present invention will be described.
FIG. 4 is a diagram showing a configuration of an antenna device according to the second embodiment of the present invention. Similar to the antenna device 101 in the first embodiment, the antenna device 102 includes an inverted L-shaped first antenna element 211, second antenna element 212, third antenna element 213, and grounding (not shown). And a feeding point 50 for feeding power to the conductor. The second antenna element 212 and the third antenna element 213 are connected to the relatively short side of the first antenna element 211 at one end to form an inverted L shape.

  The first antenna element 211 operates at the resonance frequency of the fundamental mode and the higher order mode. In addition, the second antenna element 212 selectively connects only one of the first antenna element 211 and the second antenna element 212 by being connected to either the first antenna element 211 or the second antenna element 212. An SPDT switch 311 connected to the point 50 is included. The first antenna element 211 has a switch 312 that selectively changes the antenna length of the first antenna element 211 by turning on / off.

  FIG. 5 is a diagram illustrating an example in which such an antenna device 102 is configured in a three-dimensional manner. Similar to the first embodiment, also in this embodiment, the antenna device 102 is three-dimensionalized and miniaturized by bending the antenna element, and a feeding point 50 is provided between the antenna conductor and the ground conductor 40. ing. Further, a semiconductor switch, an FET, or the like is applied to the SPDT switch 311 and the switch 312 that are illustrated with a gap.

  6A and 6B are examples of the frequency characteristics of VSWR corresponding to the states of the SPDT switch 311 and the switch 312 in the antenna apparatus 102. FIG. Similar to the first embodiment, the characteristic impedance is 50Ω, and FIG. 6A shows an SPDT switch when the SPDT switch 311 is connected to the first port P1 and the switch 312 is on. A case where 311 is connected to the second port P2 and the switch 312 is in the OFF state is shown. Similar to FIGS. 3A, 3B, and 3C, in FIGS. 6A and 6B, the mode name of the communication system and the resonance frequency band in which each mode operates are shown in a band shape. The resonance frequency of each antenna element is the same as that in the first embodiment.

  The most significant difference between the antenna device 101 according to the first embodiment and the antenna device 102 according to the second embodiment is the position where the switch is provided and the operation thereof. In the antenna device 102, an SPDT switch 311 is used, which is provided at a position where only one of the first antenna element 211 and the second antenna element 212 is connected to the feeding point 50. Therefore, when the SPDT switch 311 is connected to the first port P1 and the switch 312 is on, the antenna device 102 operates in the higher order mode without the influence of the second antenna element 212 on the first antenna element 211. (FIG. 6A).

  On the other hand, when the SPDT switch 311 is connected to the second port P2, the operating frequency of the second antenna element 312 changes due to resonance due to the conductor length of the first antenna element 211. To prevent this, when connecting the SPDT switch 311 to the second port P2, the switch 312 is turned off, the conductor length of the first antenna element 211 is shortened, and the resonance frequency of the first antenna element 211 is set to a high frequency. The band is moved (FIG. 6B).

  As described above, according to the present invention, a small antenna device having multiband characteristics can be realized by combining inverted L-shaped antennas and switching the switches arranged on the antenna elements.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to this and can be implemented in various other forms. For example, in the case of an antenna device having a three-dimensional configuration as shown in FIGS. 2 and 5, if each antenna element is formed on the outer surface of a dielectric material such as polycarbonate molded into a rectangular parallelepiped shape, the antenna is reduced in size due to the wavelength shortening effect. Can be In addition, the number of resonance frequency bands can be increased by increasing the number of antenna elements.

The figure which shows the antenna apparatus by the 1st Embodiment of this invention. 1 is a perspective view of an antenna device according to a first embodiment of the present invention. FIG. 6 is a diagram illustrating an example of frequency characteristics of the antenna device according to the first embodiment of the present invention (part 1); FIG. 6 is a diagram illustrating an example of frequency characteristics of the antenna device according to the first embodiment (No. 2). FIG. 3 is a diagram illustrating an example of frequency characteristics of the antenna device according to the first embodiment of the present invention (part 3); The figure which shows the antenna apparatus by the 2nd Embodiment of this invention. The perspective view of the antenna device by the 2nd Embodiment of this invention. The figure which shows an example of the frequency characteristic of the antenna device by the 2nd Embodiment of this invention.

Explanation of symbols

101, 102 Antenna device 201, 211 First antenna element 202, 212 Second antenna element 203, 213 Third antenna element 301 First switch 302 Second switch 311 SPDT switch 312 Switch 40 Ground conductor 50 Feed point

Claims (6)

A ground conductor;
An inverted L-shaped first antenna element composed of a relatively short first side and a relatively long second side and operating at a resonance frequency of a fundamental mode and a higher-order mode;
A feeding point provided between the ground conductor and the first side of the first antenna element;
A second antenna element having one end coupled to the first side of the first antenna element and forming an inverted L shape between the first antenna element and the feed point;
With
The second antenna element is
A first switch capable of selectively changing the antenna length of the second antenna element;
A second switch for selectively connecting the feeding point and the second antenna element;
Have
An antenna device that operates in different frequency bands according to opening and closing of the first and second switches.   And further comprising third to nth antenna elements having one end coupled to the first side of the first antenna element and forming an inverted L shape between the second antenna element and the feeding point. The antenna device according to claim 1. A ground conductor;
An inverted L-shaped first antenna element composed of a relatively short first side and a relatively long second piece and operating at a resonance frequency of a fundamental mode and a higher-order mode;
A feeding point provided between the ground conductor and the first antenna element;
A second antenna element having one end coupled to the first side of the first antenna element and forming an inverted L shape between the first antenna element and the feed point;
With
In the second antenna element, only one of the first and second antenna elements is selectively connected to a feeding point at the coupling portion with the first side of the first antenna, and the other is Having a first switch not connected,
The first antenna element has a second switch for selectively changing the antenna length of the first antenna element;
An antenna device that operates in different frequency bands according to opening and closing of the first and second switches.   And further comprising third to nth antenna elements having one end coupled to the first side of the first antenna element and forming an inverted L shape between the second antenna element and the feeding point. The antenna device according to claim 3.   5. The antenna device according to claim 1, wherein each of the antenna elements is formed on an outer surface of a rectangular parallelepiped dielectric to configure the antenna device in a three-dimensional manner.   The antenna apparatus according to claim 1, wherein each antenna element is bent.

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