JP2008028856A - Antenna device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna device which is easily manufactured with ease, copes with two frequencies, is broadband and downsized, and has stable characteristics. <P>SOLUTION: The antenna device comprising a folded dipole antenna forming a loop which is compliant with two frequencies, is integrally provided with: a first element in which an arrangement configuration of a flat element to a plane is approximately rectangular; a second element placed parallel to the first element, in which an arrangement configuration to the flat element is approximately rectangular; and rising wires making the first and the second elements conductive in which the first element is provided with feeding points on an approximately central part of one long side of the approximately rectangular shape with a certain space from each other. The rising wires are formed on an opposite long side to the feeding points with a certain space from each other, each of the rising wires is placed with a certain space in an approximately central part of one long side of the second element parallel to the opposing long side of the first element, and the flat element, the feeding points or a pair of auxiliary antennas made conductive by the rising wires, are symmetrically located on the feeding points. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a built-in antenna used in a small wireless communication device such as a portable terminal.

  Until now, the mainstream antenna for wireless portable devices has been a combination of a rod-shaped antenna that can be pulled out of the housing and a built-in antenna housed inside the device. The bar antenna is not only cumbersome for the user but also restricts the design in the device design. Therefore, in recent years, there is a trend to use only the built-in antenna without using the bar antenna.

  On the other hand, another requirement for antennas of wireless portable devices is to increase the frequency. For example, the frequency band of mobile phones has been expanded not only in Japan but worldwide, and many communication systems are employed in each of the 800 MHz to 900 MHz band and the 1.7 GHz to 2.1 GHz band. In addition, in the wireless LAN application, frequencies of 2.4 GHz to 2.5 GHz band and 4.9 GHz to 5.7 GHz band are allocated, which is higher than about twice the low frequency band as with mobile phones. A frequency band is assigned.

  Therefore, the requirement for the antenna device of the wireless portable device is that it is built-in type, can support all the required frequency bands, that is, multiple frequency bands, and has a wide band characteristic. If an antenna device having these preferable characteristics can be realized, it can be developed for various uses.

  Conventionally, even if it is a broadband antenna, the ratio band is about several percent at most with respect to the center frequency. Also, since the efficiency of such a small antenna is roughly proportional to its volume, it has been difficult to achieve good characteristics in the frequency band with a small internal antenna.

  A lot of research has been done, but the actual situation is that the development of antennas with good characteristics that can be used in actual machines has not been achieved. For example, as a small-sized, wide-band, high-gain antenna device that has a wide band even when mounted close to the base plate of a wireless device, and has a relatively high efficiency, a rectangular with a ratio of short side to long side of 10 or more The loop antenna has an outer perimeter which is substantially the same as one wavelength at the operating frequency, and is arranged in parallel to and close to the radio equipment base plate at a sufficiently small interval compared to the wavelength, and further has a short side. Folded so as to be close to the power supply unit side (see Patent Document 1).

  As a portable terminal built-in antenna capable of impedance matching over a wide band, strip length 1 having a parallel line of about ½ wavelength short-circuited at both ends, strip interval d, left and right strip widths W1, W2, strip width of short-circuited portion Double-folding of antenna length a, height h of vertical part, and spacing s of folding part after bending the part from about 1/8 wavelength left and right of the feeding point of the folded dipole antenna of W3 vertically and horizontally symmetrically An antenna system having a structure is formed, and the antenna element is arranged close to the tip of a conductor plate having the same width as the antenna length a, and a parallel feeding line is connected to the feeding point of the antenna element to constitute an antenna system. In order to match the input impedance of this antenna element and the characteristic impedance of the balanced feeder, It adjusts the spacing s and the left and right strip width (W1 / W2) (see Patent Document 2).

  As a built-in antenna for mobile terminals, which is a balanced feed antenna that maintains the self-balanced effect by fixing the strip width to the same level and can perform impedance matching over a wide band, a parallel line of about ½ wavelength with both ends short-circuited is used. Folded from left to right about 1/8 wavelength of the feeding point of the folded dipole antenna with strip length 1, strip interval d, left and right strip widths W1, W2, and strip width W3 of the short circuit part vertically and horizontally symmetrically Thus, an antenna having a double folded structure having an antenna length a, a height h of the vertical portion, and an interval s of the bent portions is formed, and this antenna element is disposed close to the tip of a conductor plate having the same width as the antenna length a. The antenna system is configured by connecting a balanced or unbalanced feed line to the feed point of this antenna element, and the input impedance of this antenna element In order to match the characteristic impedance of the balanced or unbalanced feed line, the strip width ratio (W1 / W2) of the antenna element is fixed to 1 to maintain the self-balancing action, while the interval s between the bent portions and the vertical portion In addition to the height h, the one in which the strip width W3 of the short-circuit portion and the left and right strip widths W1 = W2 are adjusted (refer to Patent Document 3) has been proposed.

  On the other hand, by constructing an antenna device by adding another antenna element sharing the feeding portion to the folded monopole antenna with the opposite side of the feeding end grounded, a closed loop is formed to reduce impedance and reduce proximity to the substrate. There is a proposal of an antenna device that can suppress the influence and can increase the number of frequencies while maintaining a simple configuration (see Patent Document 4).

JP2002-43826 JP 2004-228917 A JP2004-228918 JP-A-2005-203878

  As described above, the antennas of Patent Documents 1 to 3 have advantages such as being less affected by the ground plane (GND) and taking advantage of the advantage of the dipole antenna, and have the effect of widening the bandwidth. The antenna has two double folded structures bent vertically and horizontally at symmetrical positions on the left and right ends of the feeding point of the dipole antenna.

  However, these conventional antennas have the following drawbacks in common. First, the manufacturing process is complicated due to the double folded structure at two locations. Second, the correspondence between the two frequencies is not considered. Thirdly, the design is made under the condition that only the metal plate is used. In other words, the design is in a state of floating in the air. Fourth, in order to stabilize the structure, when a dielectric material such as plastic is inserted and fixed in the folded hollow portion of these antennas, the broadband characteristics realized by the balance of multi-mode resonance are destroyed. In other words, the antenna changes to an antenna having three resonance points apart. In short, the present invention proposes an antenna that does not have a dielectric and is ideal under the ideal conditions for electromagnetic waves, and has a problem in practical use.

  In addition, the conventional antenna of Patent Document 4 is similar in terms of a folded antenna and is advantageous for miniaturization because it is a monopole antenna, but it is necessary to combine a large number of elements for widening the bandwidth. In addition, there is a drawback that the characteristics of the antenna are easily affected by the ground plane (GND).

  The present invention solves the drawbacks of these conventional antennas, and is an antenna based on a folded dipole formed on a dielectric material such as plastic, which is easy to manufacture, has two frequencies, has a wider bandwidth, and is smaller. It is an object of the present invention to obtain an antenna device that is possible and has stable characteristics. As a result, it can be mounted on a small portable device such as a mobile phone, and can achieve two frequencies and a broad band.

  In particular, when a mobile phone is actually used for communication, it is mostly used in a state inclined with respect to a vertical line or a vertical line, and the angle is not constant. For this reason, it is most important for the antenna to efficiently radiate wireless power in space, and the radiation polarization characteristics from the antenna tend not to be so important. For this reason, the characteristic evaluation of a single antenna should be considered with an emphasis on reflection loss. As other characteristics, since the mobile phone is often used while being held close to the head by hand, there is a tendency that the antenna characteristics do not change due to the influence of the hand or body.

  In this specification, the term “corresponding to two frequencies” means that the characteristics are good in two frequency bands that are distant from each other. For example, in a mobile phone, the 800 MHz to 900 MHz band is changed to one frequency band, 1.7 GHz to The 2.1 GHz band is defined as one frequency band. The wide band preferably means that all frequencies are covered in both bands. In the following, for convenience of explanation, a mobile phone antenna will be mainly described. However, it can be used for a wireless mobile device other than a mobile phone.

  The antenna device according to the invention described in claim 1 is an antenna device comprising a folded dipole antenna for two frequencies in which an antenna element connected to a pair of feeding points forms a loop from one to the other feeding point, The antenna element is composed of a flat element having a predetermined width, the first antenna element having a substantially rectangular arrangement shape with respect to the plane of the flat element, and the flat element provided in parallel to the first antenna element. The antenna element is integrally provided with a second antenna element whose arrangement shape with respect to the plane is substantially rectangular, and a pair of rising conductors having a predetermined width for conducting the first antenna element and the second antenna element. The pair of feeding points are spaced apart at a substantially central portion of one long side of a substantially rectangular shape. The pair of rising conducting wires is formed with a gap on the opposing long sides facing the pair of feeding points, and each of the pair of rising conducting wires is parallel to the opposing long side of the first antenna element. Two antenna elements are electrically connected to a substantially central portion of one long side with a gap therebetween, and are electrically connected to the first antenna element and the second antenna element, the pair of feeding points, or the pair of rising conductors. The pair of auxiliary antenna elements are arranged in a symmetrical shape when viewed from the pair of feeding points.

  An antenna device according to a second aspect of the present invention is characterized in that the pair of auxiliary antenna elements are arranged in substantially the same plane as the first antenna element or the second antenna element according to the first aspect. It is what is arranged.

  According to a third aspect of the present invention, there is provided an antenna device according to the first aspect, wherein a dielectric having a predetermined dielectric constant is disposed between the first antenna element and the second antenna element according to the first or second aspect. A dielectric is disposed in contact with or including substantially the same surface on which the auxiliary antenna element is disposed.

  According to a fourth aspect of the present invention, there is provided an antenna device according to the first aspect of the present invention. Each antenna element is arranged.

  According to a fifth aspect of the present invention, there is provided an antenna device according to the first aspect, wherein a dielectric having a predetermined dielectric constant is disposed between the first antenna element and the second antenna element according to the first or fourth aspect. The pair of auxiliary antenna elements is disposed on a surface substantially orthogonal to the surface on which the antenna element and the second antenna element are disposed, and the dielectric includes or is in contact with the surface on which each of the pair of auxiliary antenna elements is disposed. It is what is arranged.

  The antenna device according to the invention described in claim 6 is characterized in that the lengths of the long sides of the first antenna element and the second antenna element according to any one of claims 1 to 5 are different. To do.

  The antenna device according to the invention described in claim 7 is the width of the long side flat element of the first antenna element and the second antenna element according to any one of claims 1 to 6, and the first antenna. The width of the flat element on the short side of the element and the second antenna element is different.

  According to the present invention, the vertical / horizontal double folded structure is at a position facing the feeding point and, in some cases, a position where the pair of auxiliary antenna elements are electrically connected. Even if printing is performed on a printed circuit board), antenna elements are formed by press molding and molding is performed by insert molding. In addition, since a dielectric is provided, the dielectric can be used as a structural base, and a small antenna that can be easily manufactured, structurally stable, and can be stored inside a portable device can be provided.

  The present invention can realize an antenna apparatus having two frequency bands that are separated from each other and a sufficient band that is practically required. Further, regarding the feeding method, the loop antenna has a self-balancing action as a balanced antenna, and has a feature that a current flowing through the ground plane is small even when unbalanced feeding is performed. The antenna of the present invention also has this feature. . This shows an excellent feature that there is little change in the characteristics of the antenna device due to the influence of the difference in the shape of the ground plane.

  Furthermore, by using a pair of auxiliary antenna elements, the antenna can be selected by selecting a shape that operates in a band that requires a wide band characteristic and a connection position to the antenna elements 1 and 2, the rising conductor, or the feeder line. The band with good characteristics of the device can be widened.

  In the antenna of the folded dipole antenna of Patent Documents 1 to 3, the antenna has various electromagnetic field distributions between the front and back elements, and several resonances can be achieved by optimizing the antenna shape and element dimensions. It is shown that the points gather around a certain frequency, and as a result, the antenna characteristic becomes a wide band.

  However, these studies have been made on folded antennas in the air, and were conducted under conditions where no dielectric was present. For example, when an antenna element is arranged on the surface of a substrate material such as a printed circuit board, the substrate material has a relative dielectric constant larger than 1, and the electromagnetic field distribution of each resonance mode indicating the resonance point is greatly different. As a result of the influence of the relative permittivity of the material being different, the characteristics change to an antenna having several resonance points. As a result, the original broadband characteristic of the folded antenna is destroyed.

  In addition, it is necessary to have a stable structure that is fixed to a dielectric material such as plastic in order to be mounted as a single component of a small portable device and to perform good operation even under vibrations or shocks. The above research results still have problems.

  Therefore, in the antenna device of the present invention, the antenna element is constituted by a flat element having a predetermined width, and the arrangement shape of the flat element with respect to the plane is substantially rectangular, and the first antenna element includes A second antenna element provided in parallel to the flat element and having a substantially rectangular arrangement with respect to the plane of the flat element, and a pair of rising edges having a predetermined height for conducting the first antenna element and the second antenna element. The first antenna element is formed with the pair of rising conductors spaced on opposite long sides facing the pair of feeding points, and each of the pair of rising conductors is opposed to the first antenna element. The second antenna element parallel to the side is electrically connected to the substantially central part of the long side of the second antenna element with a gap therebetween. The auxiliary antenna elements are symmetrical with respect to the first antenna element and the second antenna element, or the pair of feeding points or the pair of auxiliary antennas connected to the pair of rising conductors as viewed from the pair of feeding points. Are arranged. For this reason, the vertical / horizontal double folded structure is only at the position facing the feeding point and, in some cases, at the position where the pair of auxiliary antennas are conducted, and is formed by plastic molding even when printed on the printed circuit board. Even so, the manufacturing is easy and the cost can be reduced.

  In the present invention, starting from one feeding point of the first antenna element, the other feeding of the first antenna element is passed through one rising conductor of the opposing first antenna element, the second antenna element, and the other rising conductor. By setting the length of the path to the point (that is, the entire circumference) to a length that resonates at a substantially lower frequency, the antenna can be operated in the frequency band. Further, by adopting a vertical and horizontal double folding structure, the electromagnetic field distribution changes, and the antenna can be operated in a band of other frequencies.

  Furthermore, in the present invention, by appropriately arranging the pair of auxiliary antenna elements, the frequency band at a low frequency (first resonance frequency) or a subsequent high frequency (second resonance frequency) can be further widened. Note that the basic structure of the antenna device of the present invention is a modification of a kind of folded dipole antenna, but it can be said to be a modification of a loop antenna because of its structure.

  In the present invention, the first antenna element and the second antenna element folded in the vertical and horizontal directions are arranged by disposing a dielectric having a predetermined dielectric constant between the first antenna element and the second antenna element. By appropriately determining the relative permittivity of the substrate material of the printed circuit board and the conductor width so that the current distribution flowing through the two antenna elements and the pair of auxiliary antennas is appropriately distributed, wideband characteristics in at least two frequency bands can be obtained. realizable.

  In other words, in the present invention, by arranging at least a dielectric material different from air between the first antenna element and the second antenna element, the mode of the resonance point of each resonance frequency is different. Due to the difference in distribution, the frequency fluctuation of the low frequency (first resonance frequency) and the subsequent high frequency (second resonance frequency) are not the same. By appropriately selecting the dielectric constant and thickness of the dielectric, the shape of each element, etc. so that the fluctuations overlap each other well, the bandwidth can be broadened at at least two frequencies. Further, by appropriately arranging the pair of auxiliary antennas, the low frequency band or the high frequency band can be further widened.

  As the dielectric of the present invention, selecting a relative dielectric constant of 2 to 5 possessed by a practical plastic is suitable for manufacturing at a low cost. Preferred embodiments include those in which the dielectric is made of a printed circuit board and those in which the dielectric is made of insert molding resin.

  When a printed circuit board is used as the dielectric, the first antenna element, the second antenna element, and the pair of auxiliary antenna elements can be easily manufactured by printing on the surface of the printed circuit board. Further, the conductor pattern may be formed by a method such as etching removal, plating, spray coating or the like of the flat element.

  Also, if the dielectric is to be mounted after the first antenna element and the second antenna element are formed, these elements should be formed by removing parts other than each element by die-cutting molding or the like. It can also be formed by connecting flat conductors. In any case, the smaller the number of vertical and horizontal folded portions, the easier manufacturing and the advantage of being suitable for mass production. For example, the first antenna element and the second antenna element are individually punched and molded to remove unnecessary portions, and the two are integrated with the rising conductor, or the first antenna element, the second antenna element, the rising conductor, and the auxiliary The antenna element and the antenna element can be mass-produced by forming by punching and then bending and forming a dielectric between the elements by insert molding or the like. In any case, since there are few vertical and horizontal folded portions, there is an advantage that manufacture is easy.

  Further, in the present invention, by disposing a dielectric different from air between the first antenna element and the second antenna element, a plurality of resonance modes are collected, and the electromagnetic field distribution of each mode is obtained. From the difference, the high frequency (second resonance frequency) after the low frequency (first resonance frequency) is used to indicate a different variation, so that at least two bands are widened. As for the dielectric disposed between the first antenna element and the second antenna element, a part of the dielectric may be missing or a part may be missing. By adopting such a structure, it can be effectively used as an intermediate value (effective dielectric constant) between the dielectric constant of the dielectric and air. This may be a structure that can realize the necessary multi-frequency with air having a dielectric constant of 1 and a dielectric other than 1.

  At least the first antenna element and the second antenna element of the folded dipole antenna that does not have a pair of auxiliary antenna elements, which are the basis of the antenna device of the present invention, and the width and length of each flat element are different. It was confirmed whether it was possible to broaden simultaneously in two frequency bands. As a result, as a preferable aspect, the length and width of the long sides of the first antenna element and the second antenna element are made different, or the flat antenna elements of the long sides of the first antenna element and the second antenna element are different. By making the width and the width of the short side flat element of the first antenna element different from the width of the first antenna element, resonance occurs at a plurality of separated frequencies, and resonance occurs at each frequency. It was found that an antenna having a broadband characteristic can be obtained.

  The width of the flat antenna element need not be constant over the entire length of the long side or the short side, and the width may be changed in the middle of the length of each side. However, it is desirable to make the shape substantially symmetric when viewed from each feeding point, since the current flowing through the ground plane is reduced, and the antenna characteristics are less affected by the ground plane shape and the like.

Embodiments of the present invention will be described below with reference to the drawings.
Example 1
FIG. 1 is an explanatory view showing a plan configuration of an embodiment of the present invention. FIG. 2 is an explanatory diagram showing the rear surface of FIG. 1 in a perspective view from the front surface. In the antenna device 10 shown in the figure, the configuration of the antenna element as created using the printed board 30 will be described. As shown in FIGS. 1 and 2, the terminals 21 and 22 indicate the connection state between the antenna device 10 and the circuit board 20, starting from a feeding point 11 from the circuit board 20, passing through the strip-shaped conductor 12, and passing through as a rising conductor. It passes through the holes 13 and 14 to reach the strip-shaped conductor 15 on the back surface, returns to the surface again through the through-holes 16 and 17 as rising conductors, and returns to another feeding point 19 through the strip-shaped conductor 18. The components described above constitute a so-called “folded dipole antenna”. That is, the front side strip conductors 12 and 18 are considered as the first antenna element, and the back side strip conductor 15 is considered as the second antenna element.

  In this embodiment, the auxiliary antenna element 1 is further connected to the feeding point 11, which is further conducted through the through holes 5 and 6 to the auxiliary antenna element 2 on the back surface. Similarly, the auxiliary antenna element 3 is connected to the feeding point 19, which is electrically connected to the auxiliary antenna element 4 through the through holes 7 and 8.

  FIG. 3 is developed to make the structure of the conductor part of the other elements, etc. except the auxiliary antenna elements 1, 2, 3, 4 and the through holes 5, 6, 7, 8 of FIGS. FIG. FIG. 4 is an actual measurement diagram of the reflection characteristics of the antenna device shown in FIGS. Here, with the dimensions shown in FIG. 3, W1 = 1 mm, W2 = 2.5 mm, W3 = 1 mm, W4 = 2 mm, a = 30 mm, a ′ = 39 mm, b = 10 mm, b ′ = 8 mm, h = 1.6 mm.

  The lengths of the auxiliary antenna elements 1 and 2 and the other auxiliary antenna elements 3 and 4 are set to be approximately ½ wavelength in the first frequency band. A substrate having a relative dielectric constant of 4.5 and a thickness of 1.6 mm is disposed between the first antenna element and the second antenna element. As shown in FIG. 4, in the low frequency band (first frequency band), the ratio band having a reflection loss of 10 dB or more is 23% and in the second frequency band is 36%.

  FIG. 5 is an actual measurement diagram of the reflection characteristics when the auxiliary antenna elements 1, 2, 3, 4 and the through holes 5, 6, 7, 8 are removed from the antenna apparatus of the first embodiment whose characteristics are shown in FIG. is there. In the reflection characteristic of the antenna device in this case, the reflection loss is 5 dB at the center frequency in the first frequency band, and the specific bandwidth of the reflection loss of 10 dB or more is 36% in the second frequency band.

  As can be seen from this example, the antenna device of the present invention has a stable structure and exhibits good reflection loss characteristics.

Example 2
FIG. 6 is a top view of another embodiment of the present invention. As shown in FIG. 6, there is no portion corresponding to the auxiliary antenna elements 2 and 4 and the through holes 5, 6, 7 and 8 of the first embodiment. That is, the auxiliary antenna element is arranged only on the surface of FIG. Specifically, the antenna device 60 in the figure will be described as being created using the printed circuit board 80 as in the first embodiment.

  As shown in the figure, terminals 71 and 72 indicate a connection state between the antenna device 60 and the circuit board 70, start from a feeding point 61 from the circuit board 70, pass through a strip-shaped conductor 62, pass through a through hole 63, and the first embodiment. In the same manner as described above, a strip-shaped conductor (not shown) on the back surface is reached, returns to the surface again through the through hole 67, and returns to the other feeding point 69 through the strip-shaped conductor 68.

  In the present embodiment, a pair of auxiliary antenna elements 51, 52 are connected to the strip-shaped conductors 62, 68 at symmetrical positions viewed from the feeding point 69. The pair of auxiliary antenna elements 51 and 52 are bent on the printed circuit board 80 and are arranged symmetrically.

  FIG. 7 is an actual measurement diagram of the reflection characteristics of the antenna device. In this example, in the low frequency band (first frequency band), the specific bandwidth with a reflection loss of 10 dB or more is 12%, and in the second frequency band, the specific bandwidth with a reflection loss of 10 dB or more is 28%. .

  FIG. 8 is an actual measurement diagram of reflection characteristics when the auxiliary antenna elements 51 and 52 are removed from the antenna apparatus of FIG. In this case, the reflection loss is 7 dB in the first frequency band, and the frequency ratio bandwidth of the reflection loss of 10 dB or more is 27% in the second frequency band. As a result, a wide band characteristic is obtained in the first frequency band due to the effect of arranging the auxiliary antenna element. The lengths of the auxiliary antenna elements 51 and 52 are respectively the length from the feeding point to the front end of the auxiliary antenna element 51 via the belt-like lead wire (first antenna element) on the surface side in the first frequency band. The other auxiliary antenna element 52 has the same length.

  As can be seen from this example, the antenna device of the present invention has a stable structure and exhibits good reflection loss characteristics.

Example 3
FIG. 9 is a perspective view of still another embodiment of the present invention. As shown in the figure, in the antenna device of this example, the auxiliary antenna elements 51 and 52 of Example 2 are arranged in a U-shape, and the auxiliary antenna element is arranged only in one plane of the dielectric. . Specifically, the antenna device 90 shown in the figure will be described as being created using the printed circuit board 110 as in the first embodiment.

  As shown in the figure, the terminals 101 and 102 indicate a connection state between the antenna device 90 and the circuit board 100, start from a feeding point 91 from the circuit board 100, pass through a band-shaped conductor 92, pass through a through hole 93, and the first embodiment. In the same manner as described above, a strip-shaped conductor (not shown) on the back surface is reached, returns to the surface again through the through hole 97, and returns to the other feeding point 99 through the strip-shaped conductor 98 to constitute a “folded dipole antenna”.

  In the present embodiment, a pair of auxiliary antenna elements 81 and 82 are connected to the strip-shaped conductors 92 and 98 at symmetrical positions as viewed from the feeding point 99. The pair of auxiliary antenna elements 81 and 82 are arranged on auxiliary boards 83 and 84 that are bent with respect to the surface of the printed board 110 and arranged in a U-shape.

  FIG. 10 is an actual measurement diagram of the reflection characteristics of the antenna device of FIG. In this example, in this example, in the low frequency band (first frequency band), the specific bandwidth with a reflection loss of 10 dB or more is 15%, and in the second frequency band, the specific bandwidth with a reflection loss of 10 dB or more is 15%. FIG. 11 is an actual measurement diagram of reflection characteristics when the auxiliary antenna elements 1 and 3 are removed from the antenna apparatus of FIG. In this case, the reflection loss is 7 dB in the first frequency band, and the frequency ratio bandwidth of the reflection loss of 10 dB or more is 15% in the second frequency band. Even in this result, wide band characteristics are obtained in the first frequency band due to the effect of arranging the auxiliary antenna element. Note that the lengths of the auxiliary antenna elements 1 and 3 are approximately 1 / the length of the first frequency band from the feeding point to the tip of the auxiliary antenna element 1 or 3 via the first antenna element 10A. 4 wavelengths.

  Also in this embodiment, it can be seen that the antenna device of the present invention has a stable structure and exhibits good reflection loss characteristics.

  Further, although this embodiment shows an example using a U-shaped dielectric, the shape of the dielectric may be a so-called U-shaped or the like. That is, the antenna having such a shape can be realized, for example, in a shape along the outside of the case of the mobile phone, and can be arranged without occupying a large volume inside the case. This is also one of the features of the antenna device of the third embodiment.

It is explanatory drawing which shows the planar structure of one Example of this invention. It is explanatory drawing which showed the back surface of FIG. 1 with the perspective view from the surface. It is explanatory drawing which prescribed | regulated the expansion | deployment structure and dimension of the antenna apparatus of FIG. FIG. 3 is a diagram of actual measurement of reflection characteristics of the antenna device illustrated in FIGS. 1 and 2. FIG. 2 is a diagram of actual measurement of reflection characteristics when an auxiliary antenna element and a through hole are removed from the antenna apparatus of the first embodiment illustrated in FIG. 1. It is a top view of another Example of this invention. FIG. 7 is a diagram of actual measurement of reflection characteristics of the antenna device of FIG. 6. FIG. 7 is an actual measurement diagram of reflection characteristics when an auxiliary antenna element is removed from the antenna device of FIG. 6. It is a perspective view of another Example of this invention. FIG. 10 is a diagram of actual measurement of reflection characteristics of the antenna device of FIG. 9. FIG. 10 is a diagram of actual measurement of reflection characteristics when auxiliary antenna elements 1 and 3 are removed from the antenna apparatus of FIG. 9.

Explanation of symbols

10: Antenna device,
11, 19 ... feeding point,
12, 18 ... strip-shaped conductor,
13, 14 ... Through hole,
15 ... strip-shaped conductor,
16, 17 ... through hole,
21, 22 ... terminals,
20 ... circuit board,
30 ... printed circuit board,
51, 52 ... auxiliary antenna element,
60. Antenna device,
61, 69 ... feeding point,
62, 68 ... strip-shaped conductor,
63 ... Through hole,
67 ... Through hole,
70 ... circuit board,
71, 72 ... terminals,
80 ... printed circuit board,
81, 82 ... auxiliary antenna element,
83, 84 ... auxiliary board,
90 ... antenna device,
91, 99 ... feeding point,
92, 98 ... strip-shaped conductor,
93 ... Through hole,
97 ... through hole,
100 ... circuit board,
101, 102 ... terminals,
110 ... printed circuit board,

Claims (7)

An antenna device comprising a folded dipole antenna for two frequencies in which an antenna element connected to a pair of feeding points forms a loop from one to the other feeding point,
The antenna element is composed of a flat element with a predetermined width,
A first antenna element having a substantially rectangular arrangement with respect to the plane of the flat element, and a second antenna element provided in parallel with the first antenna element and having a substantially rectangular arrangement with respect to the plane of the flat element And a pair of rising conductors having a predetermined width for conducting the first antenna element and the second antenna element,
In the antenna element, the pair of feeding points is formed with a gap in the substantially central part of one long side of a substantially rectangular shape,
The pair of rising conductors are formed at intervals on the opposing long sides facing the pair of feeding points,
Each of the pair of rising conducting wires is electrically connected with a gap to a substantially central portion of one long side of the second antenna element parallel to the opposing long side of the first antenna element,
A pair of auxiliary antenna elements connected to one of the first antenna element, the second antenna element, a pair of feeding points, or a pair of rising conductors are arranged in a symmetrical shape when viewed from the pair of feeding points. An antenna device characterized by being made.   The antenna device according to claim 1, wherein the pair of auxiliary antenna elements are arranged in substantially the same plane as the plane on which the first antenna element or the second antenna element is arranged.   A dielectric having a predetermined dielectric constant is disposed between the first antenna element and the second antenna element, and is further in contact with or including substantially the same plane on which the pair of auxiliary antenna elements are disposed. The antenna device according to claim 1 or 2, wherein the antenna device is arranged.   2. The antenna device according to claim 1, wherein the pair of auxiliary antenna elements are respectively disposed in a pair of surfaces substantially orthogonal to a surface on which the first antenna element or the second antenna element is disposed.   A dielectric having a predetermined dielectric constant is disposed between the first antenna element and the second antenna element, and the surface substantially orthogonal to the surface on which the first antenna element and the second antenna element are disposed, 5. The antenna device according to claim 1, wherein a pair of auxiliary antenna elements are disposed, and a dielectric is disposed in contact with or including a surface where each of the pair of auxiliary antenna elements is disposed.   The antenna device according to claim 1, wherein the first antenna element and the second antenna element have different long sides. The width of the long side flat element of the first antenna element and the second antenna element is different from the width of the short side flat element of the first antenna element and the second antenna element. The antenna device according to any one of 1 to 6.

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