JP2009055374A - Antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna suited to a mobile terminal, a radio LAN and the like. <P>SOLUTION: A radiating element 1 having such a shape that a mid portion of a strip conductor element is bent, and a rectangular ground plate 2 are arranged on a coplanar plane. Here, a path length of a center line of the radiating element 1 is set to about λ/4 (λ: central wavelength) at a use central frequency. A feed point F is located between the radiating element 1 and a short side of the ground plate 2, and the feed point F is set to within a range between a neighborhood of 1/2 of a length of the short side and another end of the short side on the basis of one end of the short side of the ground plate 2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an antenna that is optimal as an antenna for a wireless LAN or the like.

  Some antennas have reverse L, reverse F, and reverse FL radiating elements. The height of these radiating elements is kept low.

Technologies relating to the reduction of the height of the antenna are disclosed in, for example, Patent Documents 1, 2, 3 and Non-Patent Documents 1, 2, 3 and the like.
JP 2000-188506 A JP 2002-185238 A JP 2004-32242 A "Antenna and radio wave propagation" (p.130-131) Kyoritsu Publishing "An Inverted FL Antenna for Dual-Frequency Operation" IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 53, NO. 8, AUGUST 2005 "Broadband of inverted L antenna using ground plane" 2006 IEICE Communication Society Conference

The antenna disclosed in Patent Document 1 has a structure in which a reactance element and a linear conductor pattern for feeding and radiating are mounted on a printed circuit board. The antenna disclosed in Patent Document 2 has a structure in which a high-frequency radiating conductor and a low-frequency radiating conductor are arranged floating on a ground. The plate-like antenna disclosed in Patent Document 3 is electromagnetically coupled to the inverted L-type antenna and operates as a parasitic element.

  Non-Patent Document 1 discloses a basic form of an inverted L-type monopole antenna. Non-Patent Document 2 discloses an antenna for two-frequency band operation using a ground plate. Non-Patent Document 3 discloses an antenna that operates in one frequency band using a ground plate.

  Since the antenna disclosed in Patent Document 1 uses a coil or the like as a reactance element, there is a limit to keeping the height low.

  The antenna disclosed in Patent Document 2 has a structure in which a high frequency radiating conductor and a low frequency radiating conductor are arranged in a floating state. For this reason, it is necessary to support these conductors on the ground, which not only complicates the structure but also increases the dimension in the height direction.

  Since the antenna disclosed in Patent Document 3 uses a parasitic element, there is a problem that the dimension in the height direction increases.

  Non-Patent Document 1 describes that the ground plate is infinite. If the ground plate is infinitely large, it cannot be incorporated into a mobile terminal housing or a wireless LAN housing that is required to be downsized. In order to set the ground plate to a finite structure, it is necessary to technically analyze the relationship between the inverted L-type antenna and the ground plate. Further, since Non-Patent Document 1 does not intend to evaluate antenna characteristics, there are many problems to be solved for practical use.

  Considering the antenna of the two frequency band operation disclosed in Non-Patent Document 2, since the parasitic structure is adopted, the structure becomes complicated, and there is room for further improvement. In Non-Patent Document 3, a square conductor plate is used as a ground plate. However, further miniaturization is required for incorporation into a mobile terminal.

  An object of the present invention is to provide an antenna suitable for a mobile terminal or a wireless LAN.

In this antenna, a radiating element having a bent shape in the middle of a strip conductor element and a rectangular ground plate are installed on the same plane, and the length of the radiating element is about λ / 4 (λ; Wavelength), a feeding point is positioned between the radiating element and the short side of the ground plate, and the feeding point is set to 1 of the length of the short side with respect to one end of the short side of the ground plate. / 2 and the other end of the short side are installed in the range.

  According to the present invention, an antenna suitable for a mobile terminal or a wireless LAN can be provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  In the antenna according to the embodiment of the present invention, as shown in FIGS. 1, 3 and 4, the basic configuration of the antenna is a radiating element 1 having a shape in which a strip conductor element is bent, and a rectangular ground plate. It consists of two. At this time, the radiating element 1 and the ground plate 2 are installed on the same surface.

  The radiating element 1 is set to a length of about λ / 4 (λ: center wavelength) at the use center frequency. In this case, the length of the radiating element 1 is the length (center line length) measured along the center of the line. About λ / 4 means that values around λ / 4 are included.

  The ground plate 2 is set to have a rectangular finite structure. The feeding point F is positioned between the radiating element 1 and the short side 2 a of the ground plate 2. The feeding point F is in the range between about 1/2 of the length of the short side 2a and the other end (right end) of the short side 2a with respect to one end (left end) of the short side 2a of the ground plate 2. In this case, “near ½” means that a value in the vicinity of ½ is included.

  In the embodiment of the present invention, the radiating element 1 uses either a square C structure that operates in one frequency band or an F type structure that operates in two frequencies. The radiating element 1 having an F-type structure that operates in two frequency bands operates in a low frequency band and a high frequency band.

  In the radiating element 1 shown in FIG. 1A, a part of the radiating element 1 exists along the short side 2a and the long side 2b of the ground plate 2, and has a square C structure. In the radiating element 1 shown in FIG. 1B, a part of the radiating element 1 exists along the long side 2 b of the ground plate 2 and has a square C structure.

  In the radiating element 1 shown in FIGS. 3 and 4, a part of the radiating element 1 exists along the short side 2a and the long side 2b of the ground plate 2, and has an F-type structure.

  The operation when the antenna according to the embodiment of the present invention shown in FIGS. 1, 3, and 4 is used as a transmission antenna will be described.

  When power is supplied between the square C-structure radiating element 1 or the F-type radiating element 1 and the ground plate 2, a potential difference is generated between the radiating element 1 and the ground plate 2. Flowing.

  In the square C structure radiating element 1 shown in FIG. 1, a current flows through the radiating element 1 in one frequency band. In the F-type structure radiating element 1 shown in FIGS. 3 and 4, different currents branch to the left and right around the feeding point F in two different frequency bands. At that time, due to the effect of the ground plate 2 having a finite structure, current efficiently flows into the square C-structure radiating element 1 in FIG. 1 and the F-type structure radiating element 1 in FIGS.

  When the current flows through the square C-structure radiating element 1 in FIG. 1, an electromagnetic wave is transmitted from the square C-structure radiating element 1 over one frequency band. Similarly, when a current flows through the F-type structure radiating element 1 of FIGS. 3 and 4, electromagnetic waves are transmitted from the F-type structure radiating element 1 over two different frequency bands.

  Next, the operation when the antenna according to the embodiment of the present invention shown in FIGS. 1, 3, and 4 is used as a receiving antenna will be described.

  When the received wave arrives at the square C structure radiating element 1 in FIG. 1, a current flows through the square C structure radiating element 1 due to the received wave. Similarly, when a received wave arrives at the F-type structure radiating element 1 of FIGS. 3 and 4, a current flows through the F-type structure radiating element 1 of FIGS. 3 and 4. At the time of reception, due to the effect of the ground plate 2 having a finite structure, current flows efficiently to the square C structure radiating element 1 in FIG. 1 and the F type structure radiating element 1 in FIGS. 3 and 4. However, in the square C structure radiating element 1, a current flows strongly over one frequency band. Further, in the F-type structure radiating element 1, a current flows strongly over two frequency bands.

  As described above, in the embodiment of the present invention, the radiating element can maintain a length of about λ / 4 at the use center frequency, and the feed point F is short with respect to one end of the short side of the ground plate. Since it is installed in the range between about ½ of the side length and the other end of the short side, it can operate at a low standing wave ratio.

  Further, since the radiating element and the ground plate are installed on the same surface, the entire antenna becomes a card type, and the circuit element can be easily incorporated on the ground plate. That is, the antenna of the embodiment of the present invention can be easily mounted on a mobile terminal or a wireless LAN device that is required to be downsized.

Since a part of the radiating element exists along the short side and the long side of the ground plate, it is also advantageous that the area occupied by the antenna can be reduced.
(Embodiment 1)

  Next, Embodiment 1 in which the radiating element is operated over one frequency band (this is referred to as “one frequency band operation”) will be described.

In FIG. 1A, a square C structure radiating element operating in one frequency band is used. Shank 1a (of the length _{L 1)} in the narrow side 2a of the ground plate 2 (the length _{L x)} located near one half of the length of, fed from point F. Point F is called a feeding point. Some 1b of the strip conductors constituting a square C structure (part of the length L ₂₎ is a short side 2a and the long side 2b of the ground plate 2 (the length L _y) are present along the said. The center line length from the feed point F to the end of the strip conductor (whose width is W) has a length of about λ / 4 at the used center frequency.

  FIG. 1B similarly uses the square C-structure radiating element 1 operating in one frequency band. However, the shaft portion 1 a is at the right end of the short side 2 a of the ground plate 2, and power is supplied from the point F. A part 1 b of the strip conductor constituting the square C structure is present along the long side 2 b of the ground plate 2.

  In the following, the position of the feeding point F of the antenna according to the first embodiment and the finite structure of the ground plate 2 will be examined technically.

Since the frequency band of digital terrestrial television broadcasting is set in the range of 470 MHz to 770 MHz, the center frequency is set to 620 MHz (the wavelength λ at this time is 484 mm, which is called the center wavelength). The voltage standing wave ratio (VSWR) value was measured from 470 MHz to 770 MHz each time the feeding point F was moved with reference to one end of the short side 2 a of the ground plate 2 (one end in FIG. 1 is the left end). At this time, the suitability of the position of the feeding point F was examined on the condition that the value was 6 or less (reference condition). At that time, the feeding point F was compared with a conventional inverted L antenna set at one end (left end) of the short side 2a of the ground plate 2 shown in FIG. In FIG. 2A, the horizontal axis represents the frequency, the vertical axis represents the VSWR value, and the frequency band of 470 MHz to 770 MHz is indicated by double arrows f _L and f _H.

In FIG. 1A, the length of the shaft portion 1a of the square C-structure radiating element 1 is L ₁ = 0.05λ, and the lengths of the strip conductor portions 1b and 1c are L ₂ = 0.15λ and L ₃ = 0.10λ, and the strip conductor width was set to W = 0.02λ. In FIG. 1B, L ₁ = 0.05λ, L ₂ = 0.07λ, L ₃ = 0.20λ, and W = 0.02λ. In the conventional inverted L antenna shown in FIG. 2B, L ₁ = 0.05λ, L ₂ = 0.25λ, and W = 0.02λ. These Figure 1 (a), FIG. 1 (b), the and in FIG. 2 (b), _{L 1} is a same length. In FIGS. 1A and 1B, the outer peripheral lengths (L ₁ + L ₂ + L ₃ ) of the strip conductors of the square C-structure radiating element 1 are 0.3λ and 0.32λ, respectively. The center line length is about λ / 4 at the used center frequency (620 MHz). Also in FIG. 2B, the strip conductor central line length is about λ / 4. However, λ means 484 mm.

In FIG. 1A, FIG. 1B, and FIG. 2B, the ground plate 2 is formed in a rectangular shape, the length of the long side 2b is L _y = 0.41λ, and the length of the short side 2a. of the set _L x = _0.21λ, and set the outer peripheral length of the ground plate 2 to _2L y _{+ 2L} x = _1.24λ.

  In the case of FIG. 2B as a comparison object, the VSWR value is 6 or less in the frequency range of 470 MHz to 747 MHz as indicated by the line connecting x in FIG. If it exceeds, the standard condition is not satisfied.

1 (a) is an example in which installed near 1/2 of the short side length L _x position of the ground plate 2 of the feed point F. In FIG. 2A, the VSWR value is 6 or less in the frequency range of 470 MHz to 770 MHz, as indicated by the line connecting the circles. That is, the standard condition is satisfied.

  FIG. 1B is an example in which the position of the feeding point F is installed at the right end of the short side of the ground plate 2. In FIG. 2A, the VSWR value is 6 or less in the frequency range of 470 MHz to 770 MHz, as indicated by the line connecting ●. That is, the standard condition is satisfied.

  Therefore, as a conclusion regarding the first embodiment, the feeding point F has a length of the short side 2a with reference to one end of the short side 2a of the ground plate 2 as shown in FIGS. 1 (a) and 1 (b). It was obtained that it should be set in a range between about 1/2 (FIG. 1A) and the other end of the short side 2a (right end: FIG. 1B).

Next, the feeding point F is set to the other end (right end) of the short side 2a of the ground plate 2 shown in FIG. 1B, and the outer peripheral length (2L _x + 2L _y ) of the ground plate 2 is changed. The VSWR value was investigated and the range of the outer peripheral length of the ground plate 2 was specified.

  As a result of the investigation, it was concluded that the outer peripheral length of the ground plate 2 should be set to 1.18λ to 1.31λ (λ: center wavelength).

  As described above, according to the first embodiment of the present invention, not only the effect of the basic configuration described above can be obtained, but also the feed point F is set to the short side length with respect to one end of the short side of the ground plate 2. By setting the range between about ½ of the length and the other end of the short side, terrestrial digital television broadcasting can be received efficiently.

  Furthermore, since the outer peripheral length of the ground plate is set to a finite structure in the range of 1.18λ to 1.31λ, the antenna can be easily incorporated into a miniaturized casing of the mobile terminal. At this time, due to the effect of the finite ground plate, a current can be efficiently passed to the square C-structure radiation element.

In addition, you may comprise an antenna as a structure which made the square C structure radiation | emission element 1 in Fig.1 (a) and FIG.1 (b) into a meander.
(Embodiment 2)

  Next, an example in which the radiating element 1 is configured as a two-frequency band operation suitable for incorporation into a wireless LAN will be described as a second embodiment. Here, the two-frequency band operation means that the antenna is operated in two different frequency bands.

In FIG. 3, the F-type structure radiating element 1 operating in two frequency bands is used. In the F-type structure radiating element 1 in FIG. 3, the shaft portion 1 a (its length is L ₁ ) is in the vicinity of ½ of the length of the short side 2 a (its length is L _x ) of the ground plate 2. Power is supplied from F. Point F is called the feeding point. A part 1b of the strip conductor (whose width is W) is along the short side 2a of the ground plate 2, and a part 1c of the conductor (the length is L ₄ ) is the long side 2b (the length is L _y ).

  Similarly, FIG. 4 also uses the F-type structure radiating element 1 operating in two frequency bands. In this case, the shaft portion 1 a is at the right end of the short side 2 a of the ground plate 2, and power is supplied from the point F. Point F is called a feeding point. A part 1b of the strip conductor is present along the short side 2a of the ground plate 2, and a part 1c of the conductor is present along the long side 2b.

  In the antenna according to the second embodiment, the optimum position of the feeding point F was examined, and further, the technical examination was performed on the finite structure of the ground plate 2.

Since the frequency band of the wireless LAN is set as two frequency bands of 2.45 GHz and 5.2 GHz, 2.45 GHz (the wavelength λ _{L at} this time is 122 mm) and 5.2 GHz (the wavelength at this time) λ _H is 58 mm) as the center frequency of each frequency band. The VSWR value was measured each time the feeding point F was moved with reference to one end (the left end in the figure) of the short side 2a of the ground plate 2. At this time, the suitability of the position of the feeding point F was examined on the condition that the value is 3 or less (two frequency conditions). In FIG. 5, the horizontal axis represents frequency and the vertical axis represents VSWR value.

In FIG. 3, the length of the shaft portion 1a operating in both the low frequency band and the high frequency band related to the two frequency band operation is L ₁ = 5 mm. The outer peripheral length of the conductor operating mainly in the high frequency band is L ₁ + L ₂ = 15 mm, and the outer peripheral length of the conductor operating mainly in the low frequency band is L ₁ + L ₃ + L ₄ = 30 mm. The strip line width of the radiating element 1 was set to W = 2 mm. In FIG. 4, the length of the shaft portion 1 a that operates in both the low frequency band and the high frequency band regarding the two frequency band operation is L ₁ = 5 mm. The outer peripheral length of the conductor operating mainly in the high frequency band is L ₁ + L ₂ = 15 mm, and the outer peripheral length of the conductor operating mainly in the low frequency band is L ₁ + L ₃ + L ₄ = 30 mm. The strip line width of the radiating element 1 was set to W = 2 mm. The outer peripheral length L ₁ + L ₂ and the outer peripheral length L ₁ + L ₃ + L ₄ are the same in FIGS. At the low band center frequency of 2.45 GHz, the outer peripheral length L ₁ + L ₃ + L ₄ is about λ _L / 4. However, λ _L = 122 mm. Even at the high-frequency center frequency of 5.2 GHz, the outer peripheral length L ₁ + L ₂ is about λ _H / 4. However, λ _H = 58 mm. Since the strip width W is narrow, the center line length is also about a quarter of the wavelength in the two frequency bands.

3 and 4, the ground plate 2 is formed in a rectangular shape, the length of the long side 2b is set to L _y = 40 mm, the length of the short side 2a is set to L _x = 20 mm, and the ground plate 2 Was set to 2L _y + 2L _x = 120 mm. 3 and 4, the position of the feeding point F was changed along the short side 2a of the ground plate 2.

In FIG. 3, the feeding point F is set near ½ of the length of the short side 2 a of the ground plate 2.

  In FIG. 3, as indicated by a solid line in FIG. 5, the VSWR value is 3 or less around 2.45 GHz and around 5.2 GHz. In other words, it was proved that it was operating in the two frequency bands used in the wireless LAN, satisfying the two frequency standards.

  In FIG. 4, as indicated by a dotted line in FIG. 5, the VSWR value is 3 or less around 2.45 GHz and around 5.2 GHz. In other words, it was proved that it was operating in the two frequency bands used in the wireless LAN, satisfying the two frequency standards.

  From the above examination results, the range of the feeding point F is in the vicinity of ½ of the length of the short side 2a and the other end of the short side 2a (the left end in the figure) with reference to one end of the short side 2a of the ground plate 2 (left end in the figure) The conclusion was reached that it should be set within the range between the right end of the figure.

Next, the feed point F is set to the other end (right end in the figure) of the short side 2a of the ground plate 2 shown in FIG. 4, and the VSWR when the outer peripheral length (2L _y + 2L _x ) of the ground plate 2 is changed. The value was investigated and the range of the outer peripheral length of the ground plate 2 was specified.

As a result of the investigation, when the center wavelength of the low frequency band is λ _L (λ _L = 122 mm), the outer peripheral length (2L _x + 2L _y ) of the ground plate 2 is set in the range of 0.95λ _L to 1.05λ _L The conclusion was reached.

  Although the first and second embodiments are adapted to terrestrial digital reception and wireless LAN, respectively, the first and second embodiments can be adapted to other mobile terminals such as mobile phones by changing the wavelength. it can.

  According to the present invention, an antenna that can be incorporated into a mobile terminal, a wireless LAN, or the like can be provided.

(A) is the antenna which concerns on Embodiment 1 of this invention, Comprising: The top view which shows the example which set the feeding point to 1/2 of the length of a short side of a ground board, (b) is a plan view of the present invention. It is an antenna which concerns on Embodiment 1, Comprising: It is a top view which shows the example which set the feeding point to the other end of a ground-plate short side. (A) is the characteristic figure which shows the relationship between the VSWR value measured by changing a feeding point in Embodiment 1, and a frequency. (B) is a structural diagram of a conventional inverted L antenna. It is an antenna which concerns on Embodiment 2 of this invention, Comprising: It is a top view which shows the example which set the feeding point to 1/2 vicinity of the length of a short side of a ground board. It is an antenna which concerns on Embodiment 2 of this invention, Comprising: It is a top view which shows the example which set the feed point to the terminal of the short side of a ground board. In Embodiment 2, it is a characteristic view which shows the relationship between the VSWR value measured by changing a feeding point, and a frequency.

Explanation of symbols

1 Radiation element (square C-type radiation element, F-type radiation element)
2 Ground plate F Feeding point

Claims (5)

A radiating element having a shape bent in the middle of a strip conductor element and a rectangular ground plate are installed on the same plane,
The length of the radiating element is set to about λ / 4 (λ: center wavelength) at the used center frequency
A feeding point is located between the radiating element and the short side of the ground plate;
The antenna according to claim 1, wherein the feeding point is installed within a range between about one half of the short side and the other end of the short side with respect to one end of the short side of the ground plate. The antenna according to claim 1, wherein the radiating element has a square C structure that operates in one frequency band. The antenna according to claim 2, wherein an outer peripheral length of the ground plate is set in a range of 1.18λ to 1.31λ (λ: center wavelength). The antenna according to claim 1, wherein the radiating element has an F-type structure. 5. The antenna according to claim 4, wherein the outer peripheral length of the ground plate is set in a range of 0.95λ _L to 1.05λ _L when a low-frequency band center wavelength during two-frequency band operation is λ _L.

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