JP2005175846A - Antenna apparatus and communication equipment equipped with it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna assembly which is used for a wide band radio system and can be reduced in size, and communication equipment comprising the same. <P>SOLUTION: There are provided a base board 11, a main plate 12 provided on the surface of the base board 11, a feeder line 13 arranged on the surface of the base board 11 away from a conductor film 12, and an antenna element 14 connected electrically to the feeder line 13. The antenna element 14 comprises a band conductor 22 provided with a first conductor 31 which extends in one direction from a start 22A to a tip, and a second conductor 33 which is folded back toward the start 22A from the tip through a bending part 32 and reaches an end 22B. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a broadband antenna device used in a wireless communication system such as a cellular phone and a communication device including the same.

Conventionally, as an antenna device of a wireless communication device using a plurality of bands, such as a mobile phone, Bluetooth (registered trademark), wireless LAN, UWB (Ultra Wide Band), etc. A multi-element antenna, a composite antenna, or the like using these antenna elements is used. In addition, an antenna device has been proposed that has a broadband by providing a parasitic element (see, for example, Patent Document 1).
Japanese Patent Laying-Open No. 2003-309417 (FIG. 1)

  However, the following problems remain in the prior art. That is, in the former antenna device, an antenna element is required as the number of frequency bands to be transmitted / received increases, and in the latter antenna device, a parasitic element is added to realize a wide band, There is a problem that the antenna device becomes large.

  The present invention has been made in view of the above-described problems. For example, the present invention provides an antenna device that can be miniaturized and used in a very broadband wireless system such as UWB, and a communication device including the antenna device. Objective.

  The present invention employs the following configuration in order to solve the above problems. That is, the antenna device of the present invention includes a first conductor portion extending in one direction from the start end portion to the tip end portion, and a second conductor extending from the tip end portion through the bent portion toward the start end portion and reaching the end portion. It has a strip | belt-shaped conductor provided with a conductor part, and is provided in the ground-plate edge part.

  In the antenna device of the present invention, it is preferable that the sum of the lengths of the first conductor portion, the bent portion, and the second conductor portion is an integral multiple of 1/4 of the wavelength λ at the lowest usable frequency.

According to the antenna device of the present invention, the antenna element is folded back in the direction of the starting end portion from the leading end portion via the first conductor portion extending in one direction from the starting end portion to the leading end portion, and then into the terminal end portion. By having the strip-shaped conductor including the second conductor portion to reach, it can be considered as being divided into the anti-phase mode and the in-phase mode like a so-called folded dipole antenna.
That is, in the in-phase mode, since the high-frequency current flowing through the strip conductor is in phase with the first conductor portion and the second conductor portion, parallel resonance does not occur between the first conductor portion and the second conductor portion. For this reason, since the return loss does not become 0 dB in the input characteristics, the antenna characteristics are wide. Accordingly, since the antenna element can have a wide antenna characteristic without using another element, a small antenna device can be obtained.
Further, in the anti-phase mode, the high-frequency current flowing through the strip conductor is in anti-phase between the first conductor part and the second conductor part, so that parallel resonance occurs, and the return loss characteristic in the input characteristic deteriorates toward 0 dB. . As a result, a band causing radio wave interference can be avoided.

In the antenna device of the present invention, the antenna element has a plate-like element body formed of a composite material having a dielectric material, a magnetic material, or both, and the first conductor portion is formed of the element body. Preferably, it is formed on one surface, the bent portion is formed on a side end surface of the element body, and the second conductor portion is formed on the other surface of the element body.
According to the antenna device of the present invention, the antenna element has a plate-like element body made of a composite material having both a dielectric material, a magnetic material, or both, and a strip conductor is formed on the surface of the element body. Thus, the physical length can be shortened without changing the electrical length of the antenna element. Therefore, the antenna device can be reduced in size.
Also, by appropriately adjusting the relative permittivity and / or relative permeability of the element body, the impedance between the first conductor portion and the second conductor portion changes, and parallel resonance occurs, resulting in a return loss. The frequency approaching 0 dB can be adjusted. Therefore, it is possible to adjust a band in which transmission / reception is not performed by the antenna device.

In the antenna device of the present invention, it is preferable that end portions in the width direction of the first conductor portion and the second conductor portion are connected by a short-circuit conductor.
According to the antenna device according to the present invention, the ends of the first conductor portion and the second conductor portion in the width direction are connected by the short-circuit conductor, so that there are a plurality of high-frequency current paths flowing through the antenna element. Thereby, since there are a plurality of resonance frequencies determined by the respective path lengths, it is possible to widen the antenna characteristics.

In the antenna device of the present invention, it is preferable that a start end portion of the first conductor portion and a terminal end portion of the second conductor portion are connected by a short-circuit conductor.
According to the antenna device according to the present invention, the common mode can be made dominant by connecting the starting end portion of the first conductor portion and the terminal end portion of the second conductor portion by the short-circuit conductor. Therefore, a wider band antenna characteristic can be obtained.

Moreover, it is preferable that the antenna device of the present invention further includes capacitive coupling adjusting means for adjusting capacitive coupling between the terminal end of the strip conductor and the starting end.
According to the antenna device of the present invention, the antenna characteristics can be widened by adjusting the degree of capacitive coupling between the terminal portion of the second conductor and the conductor film by the capacitive coupling adjusting means.

In the antenna device of the present invention, it is preferable that the antenna element or the feed line includes an impedance adjusting unit that adjusts an input impedance.
According to the antenna device of the present invention, the input impedance of the antenna device can be adjusted by the impedance adjusting means, and matching with the impedance can be achieved. Therefore, radio waves can be transmitted and received efficiently.

In the antenna device of the present invention, it is preferable that the impedance adjusting means is a conductor film formed on the antenna element or a slot formed on a feed line.
According to the antenna device of the present invention, by providing a slot in the conductor film or the feed line, the path length of the current flowing through the conductor film or the feed line is adjusted, and the input impedance of the antenna device is adjusted.

In the antenna device of the present invention, it is preferable that the impedance adjusting unit has an open stub connected to a conductor film or a feed line formed on the antenna element.
According to the antenna device according to the present invention, the input impedance of the antenna device is matched by the open stub connected to the conductor film or the feed line.

In the antenna device of the present invention, it is preferable that the impedance adjusting means has a short stub connected to the ground plane from a conductor film or a feed line formed on the antenna element.
According to the antenna device of the present invention, the input impedance of the antenna device is matched by the short stub connected to the conductor film or the feed line.

In the antenna device of the present invention, it is preferable that the impedance adjusting means is a conductor film or a feed line formed on the antenna element having a taper shape or a step shape.
According to the antenna device according to the present invention, the input impedance of the antenna device is matched by having the conductor film or the feed line have a taper shape or a step shape.

In the antenna device of the present invention, it is preferable that the impedance adjusting unit adjusts a width of a part or all of a conductor film or a feed line formed on the antenna element.
According to the antenna device of the present invention, the input impedance of the antenna device is adjusted by increasing or decreasing the width of the conductor film or the feed line.

A communication device according to the present invention includes the antenna device.
According to the communication device according to the present invention, since the antenna device is provided, the communication device can be a small communication device.

According to the antenna device of the present invention, the first conductor portion extending in one direction from the start end portion to the tip end portion, and the second conductor reaching from the tip end portion through the bent portion toward the start end portion and reaching the end portion. Since the antenna element has a strip-shaped conductor including a conductor portion, for example, wideband antenna characteristics can be obtained without combining with other elements such as a parasitic element, and the antenna device can be downsized.
In addition, according to the communication device of the present invention, since the antenna device according to the present invention is provided, the communication device can be reduced in size.

Hereinafter, a first embodiment of a communication device equipped with an antenna device according to the present invention will be described with reference to FIGS. 1 to 3.
An antenna device 1 according to the present embodiment is used in a wireless communication system such as a mobile phone, Bluetooth (registered trademark), wireless LAN, UWB, and the like, and is an antenna device used in a wireless television 2, for example.

As shown in FIG. 1A, the wireless television 2 includes a television body 3 and a UWB module 4 in which the antenna device 1 is built.
As shown in FIG. 1B, the UWB module 4 includes an antenna device 1, a shield case 5 in which a high-frequency circuit is built, and a connection connector 6 that is connected to the television body 3.

  As shown in FIGS. 2 and 3, the antenna device 1 includes a substrate 11 made of an insulating material such as a resin, a ground plate 12 provided on the surface of the substrate 11, and an edge of the ground plate 12 on the surface of the substrate 11. A feeding line 13 formed near the center of 12A and connected to a high-frequency circuit (not shown) of the wireless device and an antenna element 14 provided on the surface of the substrate 11 are provided.

The antenna element 14 includes a base body 21 that is formed of a dielectric material such as alumina and has a rectangular parallelepiped shape, and a band-shaped conductor 22 that is formed in a U shape on the surface of the base body 21.
The strip-shaped conductor 22 has a first conductor portion 31 extending in one direction from the start end portion 22A toward the tip end portion, and a second conductor portion 33 folded back in the direction of the start end portion 22A from the tip end portion via the bent portion 32. It is arranged in. In addition, the sum of the lengths of the first conductor portion 31, the bent portion 32, and the second conductor portion 33 is an integral multiple of ¼ of the wavelength λ at the use minimum frequency described later.
Further, the start end portion 22A of the first conductor portion 31 is electrically connected to the feed line 13, and the end portion 22B of the second conductor portion 33 is an open end.
The antenna element 14 is disposed on the surface of the substrate 11 so that the longitudinal direction thereof is perpendicular to the end side 12A of the ground plane 12.
The input impedance of the antenna device 1 is matched by the feed line 13.

Next, the operation of the antenna device 1 will be described with reference to FIG. In this figure, the symbol RF indicates a high frequency circuit.
The operation mode of the antenna device 1 operates by a combination of the in-phase mode and the anti-phase mode, similar to a so-called folded monopole antenna that folds current in the first conductor portion 31 and the second conductor portion 33 of the antenna element 14. ing.
In the in-phase mode, the high-frequency current flowing on the first conductor portion 31 and the high-frequency current flowing on the second conductor portion 33 are in phase, so that parallel resonance does not occur, thereby reducing return loss in input characteristics. In the anti-phase mode, the high-frequency current flowing on the first conductor portion 31 and the high-frequency current flowing on the second conductor portion 33 are in reverse phase, so that parallel resonance occurs, thereby causing a return loss characteristic in the input characteristics. There is a frequency that approaches 0 dB.
Note that the input impedance of the antenna device 1 is substantially determined in the common mode.

Here, the base plate 12 having a length in the X-axis direction of 25 mm and a length in the Y-axis direction of 43 mm, a length in the X-axis direction of 2.2 mm, a length in the Y-axis direction of 13.5 mm, and the Z-axis FIG. 5 shows the frequency characteristics of the return loss at a frequency of 1.0 GHz to 12.0 GHz of the antenna device 1 configured using the element body 21 made of alumina ceramic having a length in the direction of 1.6 mm. Moreover, the radiation characteristics in frequency 1.9 GHz and 3 GHz of XY plane shown in FIG. 2 are shown to FIG. 6 (a) and FIG.6 (b), respectively.
From FIG. 5, VSWR (Voltage Standing Wave Ratio: voltage standing wave) is used over the lowest usable frequencies of 3.8 GHz to 5.8 GHz, 6.3 GHz to 7.5 GHz, 8.3 GHz to 9.8 GHz, 10.2 GHz or more. Ratio) is 3 or less, that is, the return loss is −6.02 dB or less.

Next, transmission / reception of radio waves in the antenna device 1 of the present embodiment will be described.
In the antenna device 1 having the above configuration, a high-frequency signal having an antenna operating frequency transmitted from the high-frequency circuit to the feed line 13 is transmitted as a radio wave from the terminal end portion 22B of the strip conductor 22. In addition, a radio wave having a frequency that matches the antenna operating frequency is received by the strip conductor 22 and transmitted from the feeder line 13 to the high frequency circuit as a high frequency signal.
At this time, since the antenna element 14 matches the input impedance of the antenna device 1 and the impedance of the feeder line 13, radio waves are transmitted and received with reduced power loss.

In the antenna device 1 configured as described above, the antenna element 14 is formed by the strip-shaped conductor 22 disposed so that the first conductor portion 31 and the second conductor portion 33 face each other. Broadband antenna characteristics can be obtained without using elements. Therefore, the antenna device 1 can be downsized.
Further, the electric length of the antenna element is not changed by forming the strip conductor 22 on the surface of the element body 21 formed of a dielectric material composed of ceramics, resin, etc., a magnetic material, or a composite material having both. In addition, the physical length can be shortened, and the antenna element 14 can be further downsized. Moreover, the impedance between conductors changes by adjusting the relative permittivity or the relative permeability of the material to be used, and the parallel resonance frequency can be adjusted. Thereby, the band which is not transmitted / received by an antenna apparatus can be adjusted.

In the antenna device 1 according to the first embodiment described above, the antenna element 14 is arranged on the surface of the substrate 11 at a position perpendicular to the end 12 </ b> A of the ground plane 12, but the strip conductor 22 is not electrically connected to the ground plane 12. For example, as shown in FIGS. 7A and 7B, the antenna element 14 may be arranged perpendicular to the ground plane 12.
Moreover, as shown in FIG.7 (c) and FIG.7 (d), the antenna element 14 may be distribute | arranged with an angle with respect to the plane containing the ground plane 12. FIG. Moreover, as shown in FIG.7 (e) or FIG.7 (f), you may distribute | arrange at the angle which is not at right angles with respect to the edge 12A of the ground plane 12 in the plane containing the ground plane 12. FIG.

Next, a second embodiment will be described with reference to FIGS. In the following description, the same reference numerals are given to the components described in the above embodiment, and the description thereof is omitted.
The difference between the second embodiment and the first embodiment is that, in the antenna device 1 in the first embodiment, the first conductor portion 31 and the second conductor portion 33 are electrically connected at one place. However, in the antenna device 50 according to the second embodiment, one end of the first conductor portion 31 of the antenna element 51 and one end of the second conductor portion 33 are connected by the short-circuit conductor 52, and further, the first conductor portion 31 and the first conductor portion 31 are connected to each other. The two conductor portions 33 are connected at equal intervals between the end portions in the width direction by the short-circuit conductor 52.

  That is, the strip-shaped conductor 22 is formed on the surface of the element body 21, and the start end portion 22 </ b> A of the first conductor portion 31 and the end portion 22 </ b> B of the second conductor portion 33 are connected to the surface facing the bent portion 32. A short-circuit conductor 52 is formed. A plurality of short-circuit conductors 52 are formed on the side surfaces of the element body 21 to connect the widthwise ends of the first conductor portion 31 and the second conductor portion 33 at a predetermined interval.

Here, the base plate 12 having a length in the X-axis direction of 25 mm and a length in the Y-axis direction of 43 mm, a length in the X-axis direction of 2.2 mm, a length in the Y-axis direction of 13.5 mm, and the Z-axis The element body 21 made of alumina ceramic having a length in the direction of 1.6 mm is used, and the distance between the end portions in the width direction of the first conductor portion 31 and the second conductor portion 33 is 0.4 mm between the short-circuit conductors 52. FIG. 10 shows the return loss characteristics at a frequency of 1.0 GHz to 12.0 GHz of the antenna device 50 that is configured by connecting nine locations.
From FIG. 10, the VSWR is 3 or less, that is, the return loss is −6.02 dB or less over 3.1 GHz to 7.7 GHz and 8.3 GHz or more.

The antenna device 50 configured as described above has the same operations and effects as the antenna device 1 in the first embodiment, but the start end portion 22A of the first conductor portion 31 and the end portion 22B of the second conductor portion 33 Are connected by the short-circuit conductor 52, so that only the common mode is obtained. Therefore, the antenna characteristics can be made wider.
Further, by connecting the sides of the first conductor portion 31 and the second conductor portion 33 by the short-circuit conductor 52, there are a plurality of paths through which the high-frequency current flows, and a plurality of resonance frequencies determined by the respective path lengths. By being present, the antenna characteristics can be made wider.

In the antenna device 50 according to the second embodiment described above, the first conductor portion 31 and the second conductor portion 33 are electrically connected by the short-circuit conductor 52, but there are a plurality of paths of the high-frequency current flowing through the antenna element 51. For example, as shown in FIG. 11A, even if the short-circuit conductor 52 that connects the first conductor portion 31 and the second conductor portion 33 is arranged at non-equal intervals, as shown in FIG. Good.
Further, as shown in FIG. 11B, a plurality of short-circuit conductors 52 connecting the first conductor portion 31 and the second conductor portion 33 are respectively provided between the first conductor portion 31 and the second conductor portion 33. It may be an antenna element 62 provided with a plate-like conductor 61 to be connected.
Moreover, as shown in FIG.11 (c), the antenna element 63 by which the short circuit conductor 52 which connects the 1st conductor part 31 and the 2nd conductor part 33 was distribute | arranged to mesh shape may be sufficient.
Further, as shown in FIG. 11 (d), an antenna element 64 in which the end portions of the first conductor portion 31 and the second conductor portion 33 are all connected by the connecting conductor 52 may be used.
Further, as shown in FIG. 11E, an antenna element 65 in which all sides of the first conductor portion 31 and the second conductor portion 33 are connected by a connection conductor 52 may be used.
Further, as shown in FIG. 11 (f), an antenna element 66 in which the start end portion 22 </ b> A of the first conductor portion 31 and the end portion 22 </ b> B of the second conductor portion 33 are connected by a short-circuit conductor 52 may be used.
In an antenna device having any of these antenna elements, there are a plurality of resonance frequencies determined by the respective path lengths of the high-frequency current flowing through the antenna elements, and a wide band can be realized.

Next, a third embodiment will be described with reference to FIG. In the following description, the same reference numerals are given to the components described in the above embodiment, and the description thereof is omitted.
The difference between the third embodiment and the first embodiment is that in the antenna device 70 according to the third embodiment, the second conductor portion 33 of the antenna element 71 is connected to the start end portion 22A of the first conductor portion 31 and the second conductor portion 33. A slit 72 is provided as a capacitive coupling adjusting means for adjusting capacitive coupling with the terminal end portion 22 </ b> B of the two-conductor portion 33.

  The antenna device 70 configured as described above has the same operation and effect as the antenna device 1 in the first embodiment, but the first conductor is provided by providing the slit 72 in the second conductor portion 63 of the antenna element 71. The degree of capacitive coupling between the start end portion 22A of the portion 31 and the end portion 22B of the second conductor portion 33 is adjusted, and the antenna characteristics of the antenna device 70 can be made wider.

In the antenna device 70 according to the third embodiment described above, the slit 72 is provided in the second conductor portion 33 as the capacitive coupling adjusting means. For example, as shown in FIG. 13A, the second conductor portion 33 is provided. An antenna element 82 having a gap 71 formed on the end portion 22B side thereof may be used.
Further, as shown in FIG. 13B, an antenna element 84 in which a plate-like conductor 83 that widens an open end is formed at the terminal end portion 22 </ b> B of the second conductor portion 33 may be used.
Further, as shown in FIG. 13C, a plate-like conductor 85 that is perpendicular to the second conductor portion 33 and is disposed toward the first conductor portion 31 is formed at the terminal end portion 22 </ b> B of the second conductor portion 33. The antenna element 86 may be used.
In any of these antenna devices, the degree of capacitive coupling between the terminal end portion 22B of the second conductor portion 33 and the ground plane 12 is adjusted in the same manner as described above.

Next, a fourth embodiment will be described with reference to FIG. In the following description, the same reference numerals are given to the components described in the above embodiment, and the description thereof is omitted.
The difference between the fourth embodiment and the first embodiment is that in the antenna device 90 according to the fourth embodiment, a slot 91 is formed in the feed line 13 as impedance adjusting means for adjusting the input impedance in the feed line 13. It is a point.

  The antenna device 90 configured as described above has the same operations and effects as the antenna device 1 in the first embodiment, but the input impedance of the feed line changes due to the slot 91 formed in the feed line 13. Therefore, by adjusting the shape of the slot 91, the input impedance in the feed line 13 can be easily adjusted.

In the antenna device 90 according to the fourth embodiment described above, the slot 91 is formed in the feed line 13 as impedance adjusting means. For example, as shown in FIG. 15A, an open stub 101 is provided in the feed line 13. The antenna device 102 may be formed.
Further, as shown in FIG. 15B, an antenna device 104 in which a short stub 103 is formed on the feed line 13 may be used.
Further, as shown in FIG. 15C, an antenna device 105 in which the feed line 13 has a tapered shape whose width gradually decreases from the antenna element 14 may be used.
Further, as shown in FIG. 15B, an antenna device 106 in which the feed line 13 has a shape whose width decreases from the antenna element 14 stepwise may be used.
Further, these impedance adjusting means may be provided on a conductor film formed on the antenna element 14.
In any of these antenna elements, the input impedance can be adjusted in the same manner as described above.

In addition, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention.
For example, in the above-described embodiment, the bent portion has a planar shape, but is not limited thereto, and may have a curved surface shape.
Moreover, although the ground plane 12 was provided in the surface of the board | substrate 11, it is not restricted to this, You may provide in the middle of the back surface of the board | substrate 11, or front and back.
Moreover, although the alumina which is a dielectric material was used for the element | base_body 14, it is not restricted to this, Materials, such as a magnetic body material, a composite material, and a styrene foam, may be sufficient.

BRIEF DESCRIPTION OF THE DRAWINGS The communication apparatus provided with the antenna device in 1st Embodiment concerning this invention is shown, (a) is a perspective view of a radio | wireless television, (b) is a perspective view of a UWB module. 1 is a perspective view showing an antenna device according to a first embodiment of the present invention. It is a front view which shows the antenna element in 1st Embodiment concerning this invention. It is a conceptual diagram which shows the operation mode of the antenna apparatus in 1st Embodiment concerning this invention. It is a graph which shows the wavelength characteristic of the input impedance of the antenna apparatus in 1st Embodiment concerning this invention. (A) of the antenna device in 1st Embodiment concerning this invention is a graph which shows a radiation pattern in 1.9 GHz, (b) is 3.0 GHz. The other form of the antenna device in 1st Embodiment concerning this invention is shown, (a)-(d) is a side view, (e) And (f) is a front view. It is a perspective view which shows the antenna apparatus in 2nd Embodiment concerning this invention. It is a front view which shows the antenna element in 2nd Embodiment concerning this invention. It is a graph which shows the wavelength characteristic of the input impedance of the antenna device in 2nd Embodiment concerning this invention. It is a figure which shows the other form of the antenna device in 2nd Embodiment concerning this invention. It is a perspective view which shows the antenna apparatus in 3rd Embodiment concerning this invention. It is a perspective view which shows the other form of the antenna device in 3rd Embodiment concerning this invention. It is a perspective view which shows the antenna apparatus in 4th Embodiment concerning this invention. It is a perspective view which shows the other form of the antenna device in 4th Embodiment concerning this invention.

Explanation of symbols

1, 50, 70, 90, 102, 104, 105, 106 Antenna device 4 UWB module (communication equipment)
DESCRIPTION OF SYMBOLS 11 Board | substrate 12 Ground plate 13 Feeding line 14, 60, 62, 63, 64, 65, 66 Antenna element 21 Element body 22 Strip | belt-shaped conductor 31 1st electroconductive part 32 Bending part 33 2nd electroconductive part 52 Short-circuit conductor 72 Slit (capacitive coupling) Adjustment means)
81 Gap (capacitive coupling adjustment means)
83, 85 Plate conductor (capacitive coupling adjustment means)
91 slots (impedance adjustment means)
101 Open stub (impedance adjustment means)
103 Short stub (impedance adjustment means)

Claims (12)

  A strip-shaped conductor having a first conductor portion extending in one direction from the start end portion to the tip end portion and a second conductor portion returning from the tip end portion through the bent portion toward the start end portion and reaching the end portion is provided. The antenna device is provided at an end portion of the ground plane.   2. The antenna device according to claim 1, wherein the sum of the lengths of the first conductor portion, the bent portion, and the second conductor portion is an integral multiple of ¼ of the wavelength λ at the lowest usable frequency. . The antenna element has a plate-like element formed of a composite material having both dielectric and magnetic materials, or both,
The first conductor portion is formed on one surface of the element body, the bent portion is formed on a side end surface of the element body, and the second conductor portion is formed on the other surface of the element body. The antenna device according to claim 1 or 2, wherein   4. The antenna device according to claim 1, wherein the first conductor portion and the second conductor portion are connected to each other in the width direction by a short-circuit conductor. 5.   5. The antenna device according to claim 1, wherein a start end portion of the first conductor portion and a terminal end portion of the second conductor portion are connected by a short-circuit conductor.   4. The antenna device according to claim 1, further comprising a capacitive coupling adjusting unit that adjusts capacitive coupling between a terminal end of the strip conductor and the starting end. 5.   The antenna device according to any one of claims 1 to 6, wherein the antenna element or the feed line includes impedance adjusting means for adjusting input impedance.   8. The antenna device according to claim 7, wherein the impedance adjusting means is a conductor film formed on the antenna element or a slot formed on a feed line.   8. The antenna device according to claim 7, wherein the impedance adjusting means includes a conductor film formed on the antenna element or an open stub connected to a feed line.   The antenna device according to claim 7, wherein the impedance adjusting means includes a short stub connected to the ground plane from a conductor film or a feed line formed on the antenna element.   The antenna device according to claim 7, wherein the impedance adjusting means is a conductor film or a feed line formed on the antenna element having a taper shape or a step shape. A communication device comprising the antenna device according to any one of claims 1 to 11.

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