JP5617593B2 - Antenna device - Google Patents

Description

  The present invention relates to a microstrip antenna device that transmits and receives circularly polarized waves and radio waves different from the circularly polarized waves.

  As an antenna device that transmits and receives radio waves belonging to a plurality of frequency bands, there is a microstrip antenna device including a dielectric substrate on which an antenna electrode having a predetermined shape is formed, a so-called patch antenna device. In order to transmit / receive radio waves of different frequency bands, a patch antenna device having a plurality of antenna electrodes has been proposed.

  FIG. 13 of Patent Document 1 discloses a three-resonance antenna device that transmits and receives radio waves having three different frequencies. In this antenna device, a rectangular first patch antenna electrode is formed on a dielectric block. A square opening is formed at the center of the first patch antenna electrode. The portion of the opening where the antenna electrode is not formed functions as a slot antenna. A rectangular second patch antenna electrode is formed inside the opening. In order to make these antenna electrodes function, each antenna electrode is electrically connected to the feeding electrode. The first patch antenna electrode, the second patch antenna electrode, and the slot antenna operate at different frequencies.

  Patent Document 1 describes that a degenerate separation element is formed by cutting out a corner portion of a rectangular patch antenna electrode as shown in FIG. With this degenerate separation element, the resonance frequency along one direction of the antenna electrode and the resonance frequency in the direction orthogonal to the one direction are shifted, so that the antenna device can transmit and receive circularly polarized waves.

  Patent Document 2 discloses an antenna device including a dielectric plate on which rectangular planar radiation electrodes are formed. The planar radiation electrode has a first resonance frequency corresponding to the length in the long side direction and a second resonance frequency corresponding to the length in the short side direction. The antenna device can transmit and receive circularly polarized waves by combining two different resonance frequencies.

  Patent Document 3 discloses a microstrip antenna device including a dielectric substrate on which a rectangular first radiation electrode and an annular second radiation electrode disposed outside the first radiation electrode are formed. ing.

  The first radiation electrode is connected to the power supply electrode. Then, by appropriately selecting the distance between the first radiating conductor and the second radiating conductor, the second radiating electrode is excited along with the excitation of the first radiating electrode. This describes that it is not necessary to supply power directly to the second radiation conductor.

JP 2003-069339 A JP 2002-198725 A JP 2004-104302 A

  In the antenna device described in Patent Document 2, circularly polarized waves are transmitted and received by a rectangular radiation electrode. Since the length in the long side direction and the length in the short side direction of the rectangular electrode define the resonance frequency, it is desirable that the radiation electrode has a shape as designed. However, in the manufacturing process, it is difficult to manufacture the radiation electrode without variations in shape, and variations in the shape occur. Due to the variation in shape, there is a problem that the resonance frequency characteristics change and the circular polarization characteristics of the transmitted and received radio waves become unstable.

  In addition, as in Patent Documents 1 to 3, in an antenna device having a plurality of electrodes, the frequency characteristics and polarization characteristics of radio waves transmitted and received by the first electrode are the second values close to the first electrode. May be affected by electrode shape and placement. This is because the first electrode and the second electrode are electromagnetically coupled when the first electrode and the second electrode are close to each other. When variations occur in the shape and arrangement of the second electrode and the distance between the first electrode and the second electrode deviates from a value designed in advance, the strength of electromagnetic coupling changes. Due to this change in coupling strength, the frequency characteristics and polarization characteristics of radio waves transmitted and received by both electrodes may become unstable.

  In particular, as in the antenna device described in Patent Document 3, when the second radiation electrode is not connected to the feeding electrode and is excited by excitation of the first radiation electrode, the second radiation electrode is the second radiation electrode. It is necessary to be close to one radiation electrode. For this reason, the problem of instability of frequency characteristics and polarization characteristics may occur more remarkably.

  An object of the present invention is to provide an antenna device that can solve or alleviate any one of the above problems. An example of the object is to provide an antenna device that can reduce instability of circular polarization characteristics as much as possible even if there is a slight shift in the shape and arrangement of electrodes.

An antenna device according to one embodiment of the present invention includes a dielectric substrate, an annular first electrode portion that is provided on one surface of the dielectric substrate, and has a rectangular opening at a center portion thereof, and an opening of the first electrode portion. And a second electrode portion disposed at a distance from the first electrode portion. The first electrode portion extends longer in the second direction perpendicular to the first direction than in the first direction. The first electrode portion and the second electrode portion are excited to radiate radio waves. The interval between the first electrode portion and the second electrode portion in the first direction is any than the interval between the first electrode portion and the second electrode portion in the second direction. Is also big.

  According to the present invention, even if a slight shift occurs in the shape and arrangement of the first electrode part and the second electrode part, the circular polarization characteristics of radio waves transmitted and received by the first electrode part are unstable. Can be reduced as much as possible.

It is a schematic plan view which shows the antenna structure of the antenna device of 1st Embodiment. It is a schematic plan view which shows the antenna structure of 1st Embodiment when it sees from the opposite side to FIG. FIG. 3 is a schematic cross-sectional view of an antenna structure taken along the line 3A-3A in FIGS. 1 and 2. FIG. 4 is a schematic cross-sectional view of the antenna structure taken along line 4A-4A in FIGS. 1 and 2. It is a schematic plan view which shows an example of the antenna structure of 2nd Embodiment. It is a schematic plan view which shows another example of the antenna structure of 2nd Embodiment. It is a schematic plan view which shows the antenna structure of 3rd Embodiment. It is a schematic sectional drawing of the antenna structure along the 8A-8A line | wire of FIG. It is a schematic plan view which shows an example of the antenna structure of 4th Embodiment. It is a schematic plan view which shows another example of the antenna structure of 4th Embodiment. It is a schematic plan view which shows the antenna structure of 5th Embodiment. It is a schematic sectional drawing of the antenna structure along the 12A-12A line of FIG. It is a schematic plan view which shows the antenna structure of 6th Embodiment. It is a schematic sectional drawing of the antenna structure along the 14A-14A line | wire of FIG.

  Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment]
FIG. 1 is a schematic plan view showing an antenna structure of the antenna device according to the first embodiment of the present invention. FIG. 2 is a schematic plan view showing the antenna structure when viewed from the side opposite to FIG. 3 is a schematic cross-sectional view of the antenna structure along line 3A-3A in FIGS. 1 and 2, and FIG. 4 is a schematic cross-sectional view of the antenna structure along line 4A-4A in FIGS. is there.

  The antenna device 10 includes a dielectric substrate 11 provided with a first electrode portion 12, a second electrode portion 14, and a feed line 15. The first electrode portion 12 is provided on one surface of the dielectric substrate 11. The first electrode portion 12 has a rectangular ring shape having a rectangular opening 13 at the center. In this specification, a rectangle includes a rectangle and a square.

  The second electrode portion 14 is disposed in the opening 13 of the first electrode portion 12 with a gap from the first electrode portion 12. The second electrode portion 12 is a rectangle in which each side is arranged along the side forming the opening 13.

  In the example shown in FIGS. 1 to 4, the feed line 15 is provided on the surface of the dielectric substrate 11 opposite to the surface on which the first electrode portion 12 and the second electrode portion 14 are provided. . The first electrode portion 12 is electrically connected to the feed line 15 via a through conductor 17 that penetrates the dielectric substrate 11.

  The feeder line 15 of the antenna device 10 is connected to an external circuit (not shown). When a signal voltage is applied to the first electrode unit 12 from an external circuit via the feed line 15, the first electrode unit 12 is excited and has a first frequency according to the shape of the first electrode unit 12. Radio waves are emitted. On the other hand, when radio waves having the first frequency arrive at the first electrode unit 12, the first electrode unit 12 is excited, and a signal current flows from the first electrode unit 12 through the feeder line 15 to the external circuit. .

  In the present embodiment, the first electrode portion 12 has a rectangular shape, and has a high first resonance frequency corresponding to the length in the short side direction (first direction) T1 and the long side direction (second side). And a low second resonance frequency corresponding to the length of T2. By appropriately designing the position of the through conductor 17 and coupling these resonance frequencies, the first electrode unit 12 can transmit and receive circularly polarized waves.

  It is preferable that the second electrode unit 14 is not connected to the power supply line 15 and is configured to be excited according to the excitation of the first electrode unit 12. That is, the second electrode portion 14 is disposed so as to be electromagnetically coupled to the first electrode portion 12. Instead of this, the second electrode portion 14 may be directly connected to the feed line.

  In the present embodiment, the second electrode unit 14 is rectangular, and can transmit and receive radio waves different from the operating frequency and polarization characteristics of the radio waves transmitted and received by the first electrode unit 12. Therefore, the antenna device 10 has a two-resonance antenna structure that operates not only at the operating frequency of the first electrode unit 12 but also at the resonant frequency of the second electrode unit 14.

  As shown in FIG. 1, the intervals N1 and N2 between the first electrode portion 12 and the second electrode portion 14 in the short side direction T1 of the first electrode portion 12 are both in the long side direction T2. It is larger than both of the distances M1 and M2 between the first electrode part 12 and the second electrode part 14. Note that the interval N1 and the interval N2 may be the same size or different sizes. Further, the interval M1 and the interval M2 may be the same size or different sizes.

  According to this configuration, the second electrode unit 14 is electromagnetically strongly coupled to the first electrode unit 12 via the intervals M1 and M2 in the long side direction T2. On the other hand, the strength of electromagnetic coupling along the short side direction T1 is small. Therefore, even if the shape and arrangement of the second electrode portion 14 vary and the intervals N1 and N2 in the short side direction T1 of the first electrode portion slightly change, the short side direction T1 of the first electrode portion 12 changes. The influence on the first resonance frequency is small.

  Here, when variation occurs in the shape of the first electrode portion 12, the first resonance frequency based on the length along the short side direction T1 and the second resonance frequency based on the length along the long side direction T2 are used. The resonance frequency changes and deviates from the design value. When the lengths of the first electrode portion 12 in the short side direction T1 and the long side direction T2 are shifted from the design value by the same level, the ratio of the amount of shift with respect to the design value in the short side direction T1 is the long side direction T2. It is larger than the ratio of the amount of deviation to the design value. Therefore, the resonance frequency of the first electrode portion 12 is more strongly affected by the variation in the shape in the short side direction T1 than in the long side direction T2. Such variation in shape is difficult to eliminate in the manufacturing process.

  Therefore, in order to stabilize the circularly polarized wave characteristic of the radio wave transmitted and received by the first electrode unit 12, the first electrode unit 12 is caused by factors other than the variation in the shape of the first electrode unit 12. The variation in the first resonance frequency in the short side direction T1 may be reduced as much as possible.

  According to the antenna device 10 of the present embodiment, as described above, the intervals N1 and N2 in the short side direction T1 are both larger than the intervals M1 and M2 in the long side direction T2, so that the second electrode unit Variations in the first resonance frequency in the short-side direction T1 of the first electrode portion 12 due to variations in the shape and arrangement of 14 are suppressed. Therefore, even if a slight deviation occurs in the shape and arrangement of the first electrode portion 12 and the second electrode portion 14, variations in the first and second resonance frequencies of the first electrode portion 12 are reduced as much as possible. can do. Thereby, instability of the circular polarization characteristic of the radio wave transmitted and received by the first electrode unit 12 is suppressed.

  The antenna device 10 is preferably configured such that the second electrode portion 14 is excited in accordance with the excitation of the first electrode portion 12. In this case, it is necessary to maintain any one of the intervals N1, N2, M1, and M2 between the first electrode portion 12 and the second electrode portion 14 at a small value. In the present embodiment, since the intervals M1 and M2 in the long side direction T2 are maintained at a small value, the second electrode unit 14 can be sufficiently excited by the first electrode unit 12.

  From the results of numerical analysis, the intervals N1 and N2 in the short side direction T1 are preferably at least twice as large as the intervals M1 and M2 in the long side direction T2, and are in the range of 3 times or more and 4 times or less. Is more preferable.

  Further, the second electrode portion 14 may be connected to the ground electrode portion 16 via a through conductor 18 that penetrates the dielectric substrate 11. In this case, the second electrode unit 14 operates at ¼ wavelength resonance.

  Since the second electrode portion 14 is smaller than the first electrode portion 12, it is usually difficult to operate at a frequency lower than the resonance frequency of the first electrode portion 12. However, by operating the second electrode unit 14 at ¼ wavelength resonance, the resonance frequency of the second electrode unit 14 can be made lower than the operation frequency of the circular polarization of the first electrode unit 12. become.

  In general, an electrode portion having a low resonance frequency may be strongly electromagnetically coupled to another antenna. However, in the antenna device of this embodiment, as described above, the electromagnetic coupling between the first electrode portion 12 and the second electrode portion 14 affects the circular polarization characteristics of the first electrode portion 12. There is an advantage that it has a configuration that is difficult to exert.

  Further, when the resonance frequency of the second electrode portion 14 is lower than the operating frequency of the first electrode portion 12, the size of the antenna device 10 is determined by the size of the first electrode portion 12 arranged on the outside. Is done. As described above, since the size of the antenna device, more specifically, the dielectric substrate 11, is determined by the electrode unit 12 having a high operating frequency, there is an advantage that the size of the entire antenna device 10 can be reduced. is there.

  In the example shown in FIGS. 1 to 4, the first electrode portion 12 is connected to the feed line 15, and the second electrode portion 14 is electromagnetically coupled to the first electrode portion 12. Instead, the second electrode portion 14 is connected to the feed line, and the first electrode portion 14 is electromagnetically coupled to the second electrode portion 14 and excited by the second electrode portion. It may be a configuration. However, in this case, it is necessary to design the positional relationship between both electrode portions 12 and 14 very strictly. This is because, in order to transmit and receive circularly polarized waves, the first electrode portion 12 needs to be appropriately electromagnetically coupled to the second electrode portion 14 in both the short side direction T1 and the long side direction T2. Because.

  Therefore, from the viewpoint of expanding the options of the spacings N1, N2, M1, and M2 between the electrode portions 12 and 14, the first electrode portion 12 is connected to the feed line 15, and the second electrode portion 14 is A configuration in which the first electrode portion 12 is excited is preferable.

[Second Embodiment]
FIG. 5 is a schematic plan view showing an example of the antenna device of the second embodiment, and FIG. 6 is a schematic plan view showing another example of the antenna device of the second embodiment. 5 and 6, the same components as those in FIGS. 1 to 4 are denoted by the same reference numerals. The structure of the plane opposite to the plane shown in FIG. 5 and FIG. 6 is the same as that shown in FIG.

  In the antenna devices 20a and 20b of the second embodiment, the shapes of the second electrode portions 24a and 24b are different from those of the first embodiment. Specifically, in the antenna device 20a shown in FIG. 5, the second electrode portion 24a is an open annular linear antenna. In the antenna device 20b shown in FIG. 6, the second electrode portion 24b is a spiral linear antenna.

  As shown in FIGS. 5 and 6, at least the outermost sides of the second electrode portions 24 a and 24 b extend along the sides forming the openings 13. The intervals N1, N2, M1, and M2 between the first electrode unit 12 and the second electrode units 24a and 24b are set in the same manner as in the antenna device of the first embodiment. In the antenna device according to the first embodiment, the size of the second electrode portion 14 depends on the size of the opening 13 of the first electrode portion 12 and the distances M1, M2, N1, and N2 between the electrode portions 12 and 14. Limited (see FIG. 1). As a result, the resonance frequency of the second electrode portion 14 is also limited.

  In the antenna devices 20a and 20b of the second embodiment, the second electrode portions 24a and 24b are linear antennas. Accordingly, the lengths of the second electrode portions 24a and 24b are increased, and the resonance frequency of the second electrode portions 24a and 24b can be further reduced. Thereby, the resonance frequency of the second electrode portions 24a and 24b can be made lower than the operating frequency of the first electrode portion 12.

  One end of each of the linear antennas 24a and 24b is preferably electrically connected to the ground electrode via the through conductor 18, and the other end is preferably an open end. Furthermore, since the electric field concentrates in the vicinity of the open ends of the linear antennas 24a and 24b, it is preferable to arrange the open ends in part or inside the second electrode portions 24a and 24b. Thereby, unnecessary electromagnetic coupling between the first electrode portion 12 and the second electrode portions 24a and 24b is suppressed, and the circular polarization characteristics of the first electrode portion 12 can be stabilized. it can.

[Third Embodiment]
FIG. 7 is a schematic plan view showing the antenna device 30 according to the third embodiment. FIG. 7 shows a surface of the dielectric substrate 11 opposite to the surface on which the first and second electrode portions are provided. In FIG. 7, the first electrode portion 12 is indicated by a broken line for reference. FIG. 8 is a schematic cross-sectional view of the antenna device 30 taken along line 8A-8A in FIG. 7 and 8, the same components as those in FIG. 1 are denoted by the same reference numerals.

  In the antenna device 30 of the third embodiment, the ground electrode 36 has the first electrode portion 12 and the second electrode portion except for the linear portion 36 a drawn from the through conductor 18 connected to the second electrode portion 14. It arrange | positions so that it may not overlap with the electrode part 14 of this. That is, the ground electrode 36 excluding the linear portion 36 a does not face the first electrode portion 12 and the second electrode portion 14 with the dielectric substrate 11 interposed therebetween. Other configurations are the same as those of the antenna device 10 of the first embodiment.

  In the antenna device 10 of the first embodiment, the electromagnetic field generated between the first electrode portion 12 and the ground electrode 36 and between the second electrode portion 14 and the ground electrode 36 is confined between these electrodes. It is done. On the other hand, according to the antenna device 30 of the third embodiment, since the ground electrode 36 does not face the first electrode portion 12 and the second electrode portion 14, the electromagnetic field generated in this region is released. . Therefore, the power of the radio wave radiated from the antenna device 30 is increased, and the radiation efficiency of the antenna device 30 is improved.

[Fourth Embodiment]
FIG. 9 is a schematic plan view showing an example of the antenna device 40a of the fourth embodiment, and FIG. 10 is a schematic plan view showing another example of the antenna device 40b of the fourth embodiment. 9 and 10, the same components as those in FIG. 1 are denoted by the same reference numerals. In the antenna devices 40a and 40b of the fourth embodiment, the shapes of the first electrode portions 42a and 42b are different from those of the first embodiment. Since other configurations are the same as those of the antenna device 10 of the first embodiment, the description thereof is omitted.

  In FIG. 9, the 1st electrode part 42a has the rectangular opening 13 in the center part similarly to 1st Embodiment. The outer periphery of the first electrode portion 42a is substantially rectangular. More specifically, the first electrode portion 42a has a rectangular annular shape in which a degenerate separation element including a cutout portion 49a is formed on the outer periphery.

  In FIG. 10, the 1st electrode part 42b has the rectangular opening 13 similarly to 1st Embodiment. The outer periphery of the first electrode portion 42b is substantially rectangular. More specifically, the first electrode portion 42b has a rectangular annular shape in which a degenerate separation element including an extension portion 49b is formed on the outer periphery.

  That is, the antenna devices 40a and 40b of the fourth embodiment have degenerate separation elements formed by extending or cutting out a part of the rectangular first electrode portion. With the degeneracy separation element, the resonance frequency in the short side direction T1 and the resonance frequency in the long side direction T2 of the first electrode portions 42a and 42b can be easily finely adjusted. Thereby, the circular polarization characteristic of the radio wave transmitted and received by the first electrode portions 42a and 42b can be improved.

  In this manner, the first electrode portions 42a and 42b may have a shape deformed from a rectangular ring shape as long as the circular polarization characteristics are not deteriorated. That is, the first electrode portions 42a and 42b have a shape extending longer in the second direction T2 orthogonal to the first direction T1 than in the first direction T1 so that at least circularly polarized waves can be transmitted and received. have. Even in this case, the intervals M1, M2, N1, and N2 between the first electrode portions 42a and 42b and the second electrode portion 14 are set in the same manner as in the first embodiment.

[Fifth Embodiment]
FIG. 11 is a schematic plan view showing the antenna device 50 of the fifth embodiment. FIG. 12 is a schematic cross-sectional view of the antenna device 50 taken along the line 12A-12A in FIG. 11 and 12, the same components as those in FIG. 1 are denoted by the same reference numerals.

  In the antenna device 50 according to the fifth embodiment, the shape and arrangement of the first electrode portion 12 and the second electrode portion 14 are the same as those in the first embodiment. The first electrode portion 12 is connected to the feed line 15 through the through conductor 17.

  The second electrode portion 14 is electrically connected to the wiring 58 through the through conductor 18. The wiring 58 is not directly connected to the ground electrode 16 but is electrically connected to the ground electrode 16 via the reactance element 59. That is, the reactance element 59 is provided in the middle of an electrical path connecting the second electrode portion 14 and the ground electrode 16.

  According to the antenna device 50 of the fifth embodiment, the resonance frequency of the second electrode unit 14 can be controlled by the reactance element 59. Thereby, the choice of the resonant frequency of the 2nd electrode part 14 can be expanded, and it is also possible to operate the 2nd electrode part 14 in a still lower frequency band. In addition, the reactance element 59 can improve the matching of the resonance frequency as viewed from the feeder line 15.

  As the reactance element 59, a capacitor, an inductance element, or a composite circuit element thereof can be used.

[Sixth Embodiment]
FIG. 13 is a schematic plan view showing the antenna device of the sixth embodiment. FIG. 14 is a schematic cross-sectional view of the antenna device along the line 14A-14A in FIG. 13 and 14, the same components as those in FIG. 1 are denoted by the same reference numerals.

  Similar to the antenna device of the first embodiment, the antenna device 60 of the sixth embodiment includes the first electrode unit 12 and the second electrode unit 14. Since the configurations of the first electrode portion 12 and the second electrode portion 14 are the same as those in the first embodiment, the description thereof is omitted.

  The antenna device 60 includes a third electrode portion 69 outside the first electrode portion 12. A second feed line 65 is formed on the surface of the dielectric substrate 11 opposite to the surface on which the electrode portions 12, 14, 69 are formed. The third electrode portion 69 is electrically connected to the feed line 65 through the through conductor 67.

  According to the antenna device 60 of the sixth embodiment, not only the circularly polarized wave having the operating frequency defined by the first electrode unit 12 and the radio wave having the resonant frequency defined by the second electrode unit 14, The three electrode portions 69 can transmit and receive radio waves even at another resonance frequency.

  The third electrode portion 69 is preferably annular so as to surround the first electrode portion 12 from the viewpoint of reducing the size of the dielectric substrate 11 as much as possible. However, the third electrode portion 69 is not limited to this shape.

  Although the preferred embodiments of the present invention have been presented and described in detail above, the present invention is not limited to the above-described embodiments, and it is understood that various changes and modifications can be made without departing from the gist. I want to be.

  For example, an antenna device that arbitrarily combines the features described in the above embodiments is also included in the scope of the present invention.

10, 20a, 20b, 30, 40a, 40b, 50, 60 Antenna device 11 Dielectric substrate 12, 42a, 42b First electrode part 13 Opening 14, 24a, 24b Second electrode part 15, 65 Feed line 16, 36 Ground electrodes 17, 18, and 67 Through conductor 36a Linear portion 49a Notch portion 49b Extension portion 58 Wire 59 Reactance element 65 Second feed line 69 Third electrode portion T1 Short side direction (first direction)
T2 Long side direction (second direction)
N1, N2 First direction spacing M1, M2 Second direction spacing

Claims (10)

A dielectric substrate;
A first electrode portion provided on one surface of the dielectric substrate and extending longer in a second direction perpendicular to the first direction than the first direction, and having a rectangular opening at the center An annular first electrode portion;
An antenna device comprising: a second electrode portion disposed inside the opening of the first electrode portion and spaced apart from the first electrode portion;
The first electrode part and the second electrode part are excited to emit radio waves,
The interval between the first electrode portion and the second electrode portion in the first direction is the same between the first electrode portion and the second electrode portion in the second direction. An antenna device that is larger than any spacing between.   2. The antenna device according to claim 1, wherein the interval in the first direction is in a range of 3 to 4 times the interval in the second direction. A feed line provided on the surface of the dielectric substrate opposite to the first electrode portion and the second electrode portion;
The first electrode portion is electrically connected to the feed line via a through conductor penetrating the dielectric substrate, and the second electrode portion is excited in response to excitation of the first electrode portion. The antenna device according to claim 1 or 2, wherein A ground electrode provided on a surface of the dielectric substrate opposite to the first electrode portion and the second electrode portion;
4. The antenna device according to claim 1, wherein the second electrode portion is electrically connected to the ground electrode through a through conductor penetrating the dielectric substrate. 5.   The ground electrode is disposed so as not to overlap the first electrode portion and the second electrode portion except for a linear portion drawn from the through conductor connected to the second electrode portion. The antenna device according to claim 4.   The antenna device according to claim 4 or 5, wherein a reactance element is provided in the middle of an electrical path connecting the second electrode portion and the ground electrode.   The antenna device according to claim 1, wherein the first electrode portion has a rectangular ring shape having the opening.   The antenna device according to any one of claims 1 to 6, wherein the first electrode portion has a rectangular annular shape in which a degenerate separation element including a cutout portion or an extension portion is formed on an outer periphery.   The antenna device according to claim 7 or 8, wherein the second electrode part has a rectangular shape in which each side is arranged along a side forming the opening of the first electrode part.   The antenna device according to claim 7 or 8, wherein the second electrode portion is an open annular or spiral linear antenna having at least an outermost side extending along a side forming the opening.

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