Antenna device and wireless communication device including the same

Abstract

A dual-band supported antenna device capable of communicating at a first frequency in a specified frequency band and communicating at a second frequency in a frequency band higher than the specified frequency band includes: a ground conductor; a folded antenna conductor including a first linear portion and a second linear portion facing each other at intervals by folding; an LC resonance circuit provided in the folded antenna conductor, the LC resonance circuit passing the first frequency and attenuating the second frequency; and a feeding point provided between the ground conductor and the folded antenna conductor. A narrow gap portion with a distance smaller than that of other portions is provided between the first linear portion and the second linear portion of the folded antenna conductor.

Description

Technical Field

[0001] The present invention relates to an antenna device and a wireless communication device including the antenna device. Background Art

[0002] For example, Patent Document 1 discloses a so-called dual-band supported dipole antenna that can communicate at a frequency of a specified low frequency band and a frequency of a specified high frequency band. To support dual bands, a LC parallel circuit that allows the frequency of the low frequency band to pass through but attenuates the frequency of the high frequency band is disposed on the antenna conductor as a band-stop filter.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: U.S. Patent Application Publication No. 2005 / 0280579 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] In addition, as a miniaturized antenna, for example, a folded antenna such as a folded dipole antenna is known. An antenna that supports dual bands can also be miniaturized. However, sometimes the antenna efficiency in the high frequency band decreases due to the folding.

[0008] Therefore, an object of the present invention is to suppress a decrease in antenna efficiency in a high frequency band in an antenna device that supports dual bands and includes a folded antenna conductor.

[0009] Means for Solving the Problems

[0010] To solve the above technical problems, according to one aspect of the present invention, there is provided an antenna device, which is a dual-band supported antenna device capable of communicating at a first frequency of a specified frequency band and a second frequency of a frequency band higher than the specified frequency band, the antenna device including:

[0011] A ground conductor;

[0012] A folded antenna conductor including a first linear portion and a second linear portion that face each other with a space therebetween by folding;

[0013] An LC resonance circuit disposed on the folded antenna conductor, the LC resonance circuit allowing the first frequency to pass through and attenuating the second frequency; and

[0014] A feeding point disposed between the ground conductor and the folded antenna conductor,

[0015] Among them, a narrow gap portion with a distance smaller than that of other portions is provided between the first linear portion and the second linear portion of the folded antenna conductor.

[0016] In addition, according to another aspect of the present invention, there is provided an antenna device, which is a dual-band supported antenna device capable of communicating at a first frequency in a specified frequency band and communicating at a second frequency in a frequency band higher than the specified frequency band. The antenna device includes:

[0017] A ground conductor;

[0018] A folded antenna conductor including a first linear portion and a second linear portion that face each other with a space therebetween through folding;

[0019] An LC resonance circuit provided in the folded antenna conductor, the LC resonance circuit attenuating the first frequency and passing the second frequency; and

[0020] A feeding point provided between the ground conductor and the folded antenna conductor,

[0021] wherein, a narrow gap portion with an interval smaller than that of other portions is provided between the first linear portion and the second linear portion of the folded antenna conductor,

[0022] The LC resonance circuit is provided in the narrow gap portion.

[0023] Moreover, according to a different aspect of the present invention, there is provided a wireless communication device including:

[0024] The above-described antenna device; and

[0025] A feeding circuit that feeds power to the feeding point of the antenna device.

[0026] Effects of the Invention

[0027] According to the present invention, it is possible to suppress a decrease in antenna efficiency in a high-frequency band in a dual-band supported antenna device having a folded antenna conductor. Description of the Drawings

[0028] Figure 1 It is a partial top view of a wireless communication device including the antenna device according to Embodiment 1 of the present invention.

[0029] Figure 2 It is a diagram showing the frequency characteristics of the return loss of the antenna device according to Embodiment 1 and the antenna device of the comparative example.

[0030] Figure 3 It is a diagram showing the antenna efficiency in the high-frequency band of the antenna device according to Embodiment 1 and the antenna device of the comparative example.

[0031] Figure 4 It is a diagram showing the relationship between the frequency characteristics of the return loss of the antenna device according to Embodiment 1 and the antenna device of the comparative example and the width of the branch portion.

[0032] Figure 5 It is a diagram showing the relationship between the frequency characteristics of the return loss of the antenna device according to Embodiment 1 and the antenna device of the comparative example and the position of the branch portion.

[0033] Figure 6 It is a partial top view of a wireless communication device including the antenna device according to Embodiment 2 of the present invention.

[0034] Figure 7 It is a partial top view of a wireless communication device including the antenna device according to Embodiment 3 of the present invention.

[0035] Figure 8 It is a partial top view of a wireless communication device including the antenna device according to Embodiment 4 of the present invention.

[0036] Figure 9 It is a partial top view of a wireless communication device including the antenna device according to Embodiment 5 of the present invention.

[0037] Figure 10 It is a diagram showing the frequency characteristics of the return loss of the antenna device according to Embodiment 5. Detailed Embodiments

[0038] An antenna device according to one aspect of the present invention is a dual-band antenna device capable of communicating at a first frequency in a specified frequency band and a second frequency in a frequency band higher than the specified frequency band, the antenna device having: a ground conductor; a folded antenna conductor including a first linear portion and a second linear portion facing each other at intervals by folding; an LC resonance circuit provided in the folded antenna conductor, the LC resonance circuit passing the first frequency and attenuating the second frequency; and a feeding point provided between the ground conductor and the folded antenna conductor, wherein a narrow gap portion having a distance smaller than other portions is provided between the first linear portion and the second linear portion of the folded antenna conductor.

[0039] According to such an aspect, it is possible to suppress a decrease in antenna efficiency in a high-frequency band in a dual-band antenna device including a folded antenna conductor.

[0040] For example, it may also be that when the first linear portion and the second linear portion extend parallel to each other, one of the first linear portion and the second linear portion includes a branch portion that extends toward the other of the first linear portion and the second linear portion and forms the narrow gap portion therebetween.

[0041] For example, preferably, the distance between the first linear portion and the second linear portion is greater than the line width of the first linear portion and the line width of the second linear portion.

[0042] For example, it may also be that the folded antenna conductor includes a floating island portion provided between the first linear portion and the second linear portion, and the narrow gap portion includes a first narrow gap portion formed between the floating island portion and the first linear portion and a second narrow gap portion formed between the floating island portion and the second linear portion.

[0043] For example, it may also be that the antenna device further includes a capacitor chip provided in the narrow gap portion, and the capacitor chip connects the first linear portion and the second linear portion.

[0044] For example, it may also be that the LC resonance circuit includes a capacitor chip and an inductor chip arranged in parallel.

[0045] For example, it may also be that the folded antenna conductor is a folded dipole antenna.

[0046] For example, it may also be that the first frequency is a frequency in the 2.4 GHz band and the second frequency is a frequency in the 5 GHz band.

[0047] An antenna device according to another aspect of the present invention is a dual-band supported antenna device capable of communicating at a first frequency in a specified frequency band and a second frequency in a frequency band higher than the specified frequency band. The antenna device includes: a ground conductor; a folded antenna conductor including a first linear portion and a second linear portion that face each other at intervals by folding; an LC resonance circuit provided in the folded antenna conductor, the LC resonance circuit attenuating the first frequency and passing the second frequency; and a feeding point provided between the ground conductor and the folded antenna conductor. Among them, a narrow gap portion with a smaller interval than other portions is provided between the first linear portion and the second linear portion of the folded antenna conductor, and the LC resonance circuit is provided in the narrow gap portion.

[0048] According to such an aspect, it is possible to suppress a decrease in antenna efficiency in a high frequency band in a dual-band supported antenna device including a folded antenna conductor.

[0049] The wireless communication device in different embodiments of the present invention includes the antenna device and a feeding circuit for feeding a feeding point of the antenna device.

[0050] According to such an embodiment, it is possible to suppress a decrease in antenna efficiency in a high-frequency band in a wireless communication device having a folded antenna conductor and supporting dual bands.

[0051] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0052] (Embodiment 1)

[0053] Figure 1 FIG. is a partial top view of a wireless communication device including the antenna device according to Embodiment 1 of the present invention. In addition, the X-Y-Z orthogonal coordinate system shown in the figure is used to easily understand the present invention and does not limit the invention.

[0054] As Figure 1 shown, the wireless communication device 50 including the antenna device 10 according to Embodiment 1 is used in a manner of being mounted on an electronic device capable of wireless communication. In addition, the antenna device 10 is a dual-band antenna device capable of communicating at a first frequency in a specified frequency band and a second frequency in a frequency band higher than the specified frequency band. In the case of Embodiment 1, the first frequency is a frequency in the 2.4 GHz band (for example, 2.4 GHz to 2.484 GHz), and the second frequency is a frequency in the 5 GHz band (for example, 5.15 GHz to 5.85 GHz).

[0055] As Figure 1 shown, in the case of Embodiment 1, the antenna device 10 has a ground conductor 12 provided on a base substrate 52 of the wireless communication device 50 and a folded antenna conductor 14 provided on the base substrate 52 and connected to the ground conductor 12. In addition, the antenna device 10 has an LC resonance circuit 16 provided on the folded antenna conductor 14 and a feeding point 18 provided between the ground conductor 12 and the folded antenna conductor 14. In addition, a feeding circuit (not shown) provided in the wireless communication device 50 is connected to the feeding point 18. The antenna device 10 is fed from the feeding circuit via the feeding point 18.

[0056] In the case of Embodiment 1, the ground conductor 12 of the antenna device 10 is a conductor pattern such as copper formed on a base substrate 52 made of an insulating material.

[0057] In the case of Embodiment 1, the folded antenna conductor 14 of the antenna device 10 is a so-called folded dipole antenna and is a conductor pattern such as copper formed on the base substrate 52.

[0058] Specifically, the folded antenna conductor 14 is composed of a first element portion and a second element portion 20, 22 having a left-right symmetric (Y-axis symmetric) structure, a non-feed line portion 24, and a feed line portion 26 that connect them to the ground conductor 12.

[0059] In the folded antenna conductor 14, the first element portion 20 is connected to one end 12a (one end in the Y-axis direction) of the ground conductor 12 via the non-feed line portion 24. In addition, the first element portion 20 includes a first linear portion 20a and a second linear portion 20b that face each other at intervals through folding.

[0060] Specifically, the first element portion 20 of the folded antenna conductor 14 extends outward (in the negative X-axis direction) from the non-feed line portion 24, and then changes its direction by 180 degrees, that is, folds and extends inward (in the positive X-axis direction). As a result, the first element portion 20 includes a first linear portion 20a and a second linear portion 20b that face each other at intervals.

[0061] In addition, in the case of the first embodiment 1, in the first element portion 20, the first linear portion 20a and the second linear portion 20b extend parallel to each other at a distance D1 and parallel to one end 12a of the ground conductor 12. Preferably, the distance D1 is greater than the width W1 of the first linear portion 20a and the width W2 of the second linear portion 20b. In contrast, when the distance D1 is less than the widths W1, W2, the flow of the current flowing through the second linear portion 20b in the opposite direction is obstructed due to the magnetic field generated by the current flowing through the first linear portion 20a.

[0062] In addition, the second linear portion 20b of the first element portion 20 has an open end 20c. The electrical length of the first element portion 20 from the non-feed line portion 24 to the open end 20c is substantially 1 / 4 of the wavelength of the first frequency.

[0063] In the folded antenna conductor 14, the second element portion 22 is connected to one end 12a of the ground conductor 12 via the feed line portion 26. In addition, the second element portion 22 includes a first linear portion 22a and a second linear portion 22b that face each other at intervals through folding.

[0064] Specifically, the second element portion 22 of the folded antenna conductor 14 extends outward (in the positive X-axis direction) from the feed line portion 26, then changes its direction by 180 degrees, that is, folds and extends inward (in the negative X-axis direction), and then terminates. As a result, the second element portion 22 includes a first linear portion 22a and a second linear portion 22b that face each other at intervals.

[0065] In addition, in the case of the present Embodiment 1, in the second element portion 22, the first linear portion 22a and the second linear portion 22b extend parallel to each other with a distance D1 therebetween and parallel to one end 12a of the ground conductor 12. Preferably, the distance D1 is greater than the width W1 of the first linear portion 22a and the width W2 of the second linear portion.

[0066] Further, the second linear portion 22b of the second element portion 22 has an open end 22c. The electrical length from the feed line portion 26 to the open end 22c of the second element portion 22 is a length that is 1 / 4 of the wavelength of the first frequency.

[0067] Moreover, the first linear portion 20a of the first element portion 20 and the first linear portion 22a of the second element portion 22 are located on the same straight line, and the second linear portion 20b of the first element portion 20 and the second linear portion 22b of the second element portion 22 are located on the same straight line.

[0068] In addition, in the case of the present Embodiment 1, the feeding point 18 is provided between the ground conductor 12 and the folded antenna conductor 14. In the case of the present Embodiment 1, the feeding point 18 is provided at the connecting portion between the ground conductor 12 and the feed line portion 26.

[0069] LC resonance circuits 16 are respectively provided in the first element portion 20 and the second element portion 22 of the folded antenna conductor 14. In the case of the present Embodiment 1, the LC resonance circuit 16 includes a capacitor chip 28 having a prescribed capacitance and an inductor chip 30 that is arranged in parallel with the capacitor chip 28 and has a prescribed inductance.

[0070] The LC resonance circuit 16 is an LC parallel circuit that allows a first frequency in a relatively low prescribed frequency band to pass through but attenuates a second frequency in a frequency band that is relatively high compared to the prescribed frequency band, that is, resonates at the second frequency. Further, the LC resonance circuit 16 is provided at a position on the first element portion 20 that is at a distance of 1 / 4 of the wavelength of the second frequency away from the non-feed line portion 24, and at a position on the second element portion 22 that is at the same distance away from the feed line portion 26.

[0071] According to such an antenna device 10, the first element portion 20 and the second element portion 22 of the folded antenna conductor 14 function as dipole antennas. In addition, since the first element portion 20 and the second element portion 22 are folded, the antenna device 10 (i.e., the wireless communication device 50) is miniaturized compared to the case where it extends along a straight line without being folded.

[0072] Moreover, when communicating at the first frequency in a relatively low specified frequency band, current flows through the entire first element portion 20 and the second element portion 22. On the other hand, when communicating at the second frequency in a frequency band relatively higher than the specified frequency band, current flows through the portion of the first element portion 20 between the non-feed line portion 24 and the LC resonance circuit 16, and the portion of the second element portion 22 between the feed line portion 26 and the LC resonance circuit 16. That is, the LC resonance circuit 16 functions as a band-stop filter for the second frequency. Thus, the antenna device 10 functions as a dual-band antenna capable of communicating at the first frequency and the second frequency.

[0073] However, the inventors have found that in such an antenna device 10, it is possible for the antenna efficiency of the second frequency in the relatively high frequency band to decrease. In addition, the inventors have determined the cause and found the following structure for countermeasures.

[0074] As Figure 1 shown, in order to suppress the decrease in the antenna efficiency of the second frequency in the relatively high frequency band, a narrow gap portion 20d having a distance D2 smaller than the distance D1 of other portions is provided between the first linear portion 20a and the second linear portion 20b of the first element portion 20 of the folded antenna conductor 14. Similarly, a narrow gap portion 22d having a distance D2 smaller than the distance D1 of other portions is provided between the first linear portion 22a and the second linear portion 22b of the second element portion 22.

[0075] In the case of the first embodiment 1, the first linear portion 20a of the first element portion 20 is provided with a branch portion 20e that extends toward the second linear portion 20b to form a narrow gap portion 20d therebetween. Similarly, the first linear portion 22a of the second element portion 22 is provided with a branch portion 22e that extends toward the second linear portion 22b to form a narrow gap portion 22d therebetween.

[0076] As Figure 1 shown, according to such a branch portion 20e, a capacitor C1 is formed between the branch portion 20e of the first linear portion 20a of the first element portion 20 and the second linear portion 20b. Similarly, according to the branch portion 22e, a capacitor C1 is formed between the branch portion 20e of the first linear portion 22a of the second element portion 22 and the second linear portion 22b.

[0077] The effects brought about by providing such narrow gap portions 20d and 22d will be described.

[0078] Figure 2 is a diagram showing the frequency characteristics of the return loss of the antenna device according to the first embodiment and the antenna device of the comparative example. Figure 3It is a diagram showing the antenna efficiency in the high-frequency band of the antenna device according to Embodiment 1 and the antenna device of the comparative example, respectively.

[0079] In Figure 2 and Figure 3 the antenna device of the comparative example is substantially the same as the device obtained by removing the branch portions 20e and 22e from the antenna device 10 according to the present Embodiment 1. In addition, the width W1 of the first linear portions 20a and 22a and the width W2 of the second linear portions 20b and 22b are 1 mm, and the width W3 of the branch portions 20e and 22e is 1.5 mm. In addition, the length of the first linear portions 20a and 22a is 26.5 mm, and the length of the second linear portions 20b and 22b is 6 mm. And, the distance D1 between the first linear portions 20a and 22a and the second linear portions 20b and 22b is 3 mm, and the distance D2 of the narrow gap portions 20d and 22d is 0.5 mm. Moreover, the capacitance of the capacitance chip 28 of the LC resonance circuit 16 is 0.3 pF, and the inductance of the inductance chip 30 is 2.8 nH.

[0080] As Figure 2 shown, by providing the branch portions 20e and 22e, a frequency shift to the lower frequency side occurs at a frequency between the low-frequency band (2.4 GHz band) and the high-frequency band (5 GHz band) (the portion surrounded by the dotted circle). Specifically, regarding the harmonic of the first frequency (about 2.4 GHz) in the low-frequency band that interferes with the fundamental wave (about 5.7 GHz) of the second frequency in the high-frequency band in the antenna device of the comparative example without the branch portions 20e and 22e, it shifts to the lower frequency side by providing the branch portions 20e and 22e. Thus, as Figure 3 shown, the antenna efficiency in the high-frequency band, particularly in the region on the low-frequency side within the high-frequency band, is improved. As a result, high antenna efficiency is obtained over the entire high-frequency band.

[0081] In addition, the degree of shift of the harmonic of the first frequency can be adjusted by changing the width W3 and position of the branch portions 20e and 22e.

[0082] Figure 4 It is a diagram showing the relationship between the frequency characteristics of the return loss of the antenna device according to Embodiment 1 and the antenna device of the comparative example, respectively, and the width of the branch portion. In addition, Figure 5 It is a diagram showing the relationship between the frequency characteristics of the return loss of the antenna device according to Embodiment 1 and the antenna device of the comparative example, respectively, and the position of the branch portion.

[0083] As Figure 4 shown in Examples 1 to 3 of Figure 5As shown in Embodiment 1 and Embodiment 4, by moving the branch portions 20e and 22e outward by, for example, 2 mm (by moving away from the non-feed line portion 24 and the feed line portion 26), the harmonics of the first frequency also shift to the lower frequency side.

[0084] Therefore, as Figure 4 and Figure 5 shown, by appropriately changing the widths W3 and positions of the branch portions 20e and 22e, the degree of shift of the harmonics of the first frequency can be adjusted as desired. As a result, the interference between the harmonics of the first frequency and the fundamental wave of the second frequency can be further suppressed.

[0085] According to the first embodiment as described above, in the antenna device 10 supporting dual bands having the folded antenna conductor 14, a decrease in antenna efficiency in the high frequency band can be suppressed.

[0086] In addition, in the case of the first embodiment, as Figure 1 shown, the branch portions 20e and 22e extend from the first linear portions 20a and 22a to form narrow gap portions 20d and 22d between the second linear portions 20b and 22b. Alternatively, the branch portion may extend from the second linear portion to form a narrow gap portion between the first linear portion.

[0087] (Embodiment 2)

[0088] The second embodiment is a modified version of the first embodiment described above. Therefore, the second embodiment will be described centering on aspects different from the first embodiment described above. In addition, the constituent elements of the second embodiment that are substantially the same as those of the first embodiment described above are denoted by the same reference numerals.

[0089] Figure 6 is a partial top view of a wireless communication device including the antenna device according to the second embodiment of the present invention.

[0090] As Figure 6 shown, the antenna device 110 according to the second embodiment is provided in the wireless communication device 150. The folded antenna conductor 114 of the antenna device 110 includes a first element portion 120 and a second element portion 122. The first element portion 120 includes a first linear portion 120a and a second linear portion 120b that face each other with a space therebetween by folding, and the second element portion 122 includes a first linear portion 122a and a second linear portion 122b that face each other with a space therebetween by folding.

[0091] Between the first linear portion 120a and the second linear portion 120b of the first element portion 120, a narrow gap portion 120d having a distance smaller than that of other portions is provided. Similarly, between the first linear portion 122a and the second linear portion 122b of the second element portion 122, a narrow gap portion 122d having a distance smaller than that of other portions is provided.

[0092] Different from the above-described Embodiment 1, in the case of this Embodiment 2, the narrow gap portions 120d and 122d are not formed by branch portions extending from the first linear portions 120a and 122a.

[0093] Instead, the first element portion 120 of the folded antenna conductor 114 includes an island-like portion 120e provided between the first linear portion 120a and the second linear portion 120b, and the second element portion 122 includes an island-like portion 122e provided between the first linear portion 122a and the second linear portion 122b.

[0094] The island-like portions 120e and 122e are not continuous with the first linear portions 120a and 122a and the second linear portions 120b and 122b, respectively, but each have one end that forms narrow gap portions 120d and 122d (first narrow gap portions) between the first linear portions 120a and 122a and the other end that forms narrow gap portions 120d and 122d (second narrow gap portions) between the second linear portions 120b and 122b.

[0095] In the second embodiment as described above, similarly to the above-described Embodiment 1, it is also possible to suppress a decrease in antenna efficiency in a high-frequency band in the antenna device 110 that supports dual bands and includes the folded antenna conductor 114.

[0096] (Embodiment 3)

[0097] This Embodiment 3 is a modified version of the above-described Embodiment 1. Therefore, this Embodiment 3 will be described centering on aspects different from the above-described Embodiment 1. In addition, the same reference numerals are given to the constituent elements of this Embodiment 3 that are substantially the same as those of the above-described Embodiment 1.

[0098] Figure 7 It is a partial top view of a wireless communication device including the antenna device according to Embodiment 3 of the present invention.

[0099] As Figure 7As shown, the antenna device 210 according to Embodiment 3 is provided in a wireless communication device 250. The folded antenna conductor 214 of the antenna device 210 includes a first element portion 220 and a second element portion 222. The first element portion 220 includes a first linear portion 220a and a second linear portion 220b that face each other with a space therebetween by folding. The second element portion 222 includes a first linear portion 222a and a second linear portion 222b that face each other with a space therebetween by folding.

[0100] A narrow gap portion 220d having a distance smaller than that of other portions is provided between the first linear portion 220a and the second linear portion 220b of the first element portion 220. Similarly, a narrow gap portion 222d having a distance smaller than that of other portions is provided between the first linear portion 222a and the second linear portion 222b of the second element portion 222.

[0101] Different from the above-described Embodiment 1, in the case of Embodiment 3, the narrow gap portions 220d and 222d are not formed by branch portions extending from the first linear portions 220a and 222a. Further, different from the above-described Embodiment 2, the narrow gap portions 220d and 222d are not formed by floating island portions provided between the first linear portions 220a and 222a and the second linear portions 220b and 222b.

[0102] Instead, the second linear portions 220b and 222b extend in a direction inclined with respect to the extending direction (X-axis direction) of the first linear portions 220a and 222a such that the portions closer to the open ends 220c and 222c have a smaller distance from the first linear portions 220a and 222a. As a result, narrow gap portions 220d and 222d are formed between the open ends 220c and 222c and the first linear portions 220a and 222a.

[0103] In Embodiment 3 as described above, similarly to the above-described Embodiment 1, it is also possible to suppress a decrease in antenna efficiency in a high-frequency band in the antenna device 210 supporting dual bands having the folded antenna conductor 214.

[0104] (Embodiment 4)

[0105] Embodiment 4 is a modified form of the above-described Embodiment 1. Therefore, Embodiment 4 will be described centering on aspects different from the above-described Embodiment 1. In addition, the constituent elements of Embodiment 4 that are substantially the same as those of the above-described Embodiment 1 are denoted by the same reference numerals.

[0106] Figure 8 It is a partial top view of a wireless communication device including the antenna device according to Embodiment 4 of the present invention.

[0107] As Figure 8 shown, the antenna device 310 according to the fourth embodiment is provided in the wireless communication device 350. In addition, the antenna device 310 according to the fourth embodiment has the folded antenna conductor 14 of the antenna device 10 of the first embodiment described above. The difference is that capacitive chips 332 for connecting the first linear portions 20a, 22a and the second linear portions 20b, 22b are respectively provided in the narrow gap portions 20d of the first element portion 20 and the narrow gap portions 22d of the second element portion 22 of the folded antenna conductor 14.

[0108] By appropriately selecting the capacitance value of the capacitive chip 332, the capacitance C1 of the narrow gap portions 20d, 22d can be adjusted as desired and simply (for example, compared with the case of changing the shape of the folded antenna conductor 14). As a result, the degree of the shift of the harmonic of the first frequency can be adjusted as desired. As a result, the interference between the harmonic of the first frequency and the fundamental wave of the second frequency can be further suppressed.

[0109] In the fourth embodiment as described above, similarly to the first embodiment, it is also possible to suppress the decrease in the antenna efficiency in the high frequency band in the antenna device 310 that supports dual bands and includes the folded antenna conductor 14.

[0110] (Embodiment 5)

[0111] In the case of the first embodiment described above, the antenna device 10 has the LC resonance circuit 16 in order to function as an antenna device that supports dual bands. The LC resonance circuit 16 is an LC parallel circuit that allows the first frequency in a relatively low frequency band to pass through but attenuates the second frequency in a relatively high frequency band, that is, resonates at the second frequency. In contrast, the LC resonance circuit of the antenna device in the fifth embodiment performs a different operation. Therefore, the fifth embodiment will be described centering on aspects different from those of the first embodiment described above. In addition, the constituent elements of the fifth embodiment that are substantially the same as the constituent elements of the first embodiment described above are denoted by the same reference numerals.

[0112] Figure 9 is a partial top view of a wireless communication device including the antenna device according to the fifth embodiment of the present invention.

[0113] As Figure 9 shown, the antenna device 410 according to the fifth embodiment is provided in the wireless communication device 450. In addition, the antenna device 410 has a folded antenna conductor 414 including a first element portion 420 and a second element portion 422.

[0114] The first element portion 420 of the folded antenna conductor 414 includes a first linear portion 420a and a second linear portion 420b that face each other with a space therebetween by folding. Similarly, the second element portion 422 also includes a first linear portion 422a and a second linear portion 422b that face each other with a space therebetween by folding.

[0115] In addition, a narrow gap portion 420d having a smaller interval than other portions is provided between the first linear portion 420a and the second linear portion 420b of the first element portion 420. In the case of the fifth embodiment, the first linear portion 420a includes a branch portion 420e that extends toward the second linear portion 420b to form the narrow gap portion 420d therebetween.

[0116] Similarly, a narrow gap portion 422d having a smaller interval than other portions is provided between the first linear portion 422a and the second linear portion 422b of the second element portion 422. In the case of the fifth embodiment, the first linear portion 422a includes a branch portion 422e that extends toward the second linear portion 422b to form the narrow gap portion 422d therebetween.

[0117] In the case of the fifth embodiment, LC resonance circuits 434 are respectively provided in the narrow gap portion 420d of the first element portion 420 and the narrow gap portion 422d of the second element portion 422 to connect the first linear portion 420a and the second linear portion 420b and to connect the first linear portion 422a and the second linear portion 422b.

[0118] In addition, in the case of the fifth embodiment, the LC resonance circuit 434 includes a capacitor chip 436 having a predetermined capacitance and an inductor chip 438 that is arranged in parallel with the capacitor chip 436 and has a predetermined inductance.

[0119] Moreover, different from the LC resonance circuit 16 of the first embodiment described above, the LC resonance circuit 434 in the fifth embodiment allows a second frequency in a relatively high frequency band to pass through but attenuates a first frequency in a relatively low frequency band, that is, resonates at the first frequency. Further, the capacitance of the capacitor chip 436 of the LC resonance circuit 434 is 2.1 pF, and the inductance of the inductor chip 438 is 2.0 nH.

[0120] In the antenna device 410 according to the fifth embodiment, the same effects as those of the first embodiment described above can also be obtained.

[0121] Figure 10 It is a diagram showing the frequency characteristics of the return loss of the antenna device according to the fifth embodiment.

[0122] As Figure 10As shown, in the antenna device 410 according to the fifth embodiment, the harmonic (about 2.8 GHz) of the fundamental wave (about 2.4 GHz) of the first frequency in the low frequency band (2.4 GHz band) is far from the fundamental wave (about 5.5 GHz) of the second frequency in the high frequency band (5 GHz band). Thus, interference between the harmonic and the fundamental wave of the second frequency is suppressed. As a result, high antenna efficiency is obtained over the entire high frequency band.

[0123] In the fifth embodiment as described above, similar to the first embodiment, it is also possible to suppress a decrease in antenna efficiency in the high frequency band in the antenna device 410 that supports dual bands and includes the folded antenna conductor 414.

[0124] Multiple embodiments are listed above to illustrate the present invention, but the embodiments of the present invention are not limited to these.

[0125] For example, in the case of the first embodiment and the fifth embodiment described above, the LC resonance circuits 16 and 434 include a capacitor chip and an inductor chip arranged in parallel. Thus, the antenna device is miniaturized. However, the structure of the LC resonance circuit is not limited to this. For example, a capacitor element composed of a pair of parallel conductor patterns and an inductor element composed of a meandering conductor pattern can also be used to form the LC resonance circuit on the substrate.

[0126] In addition, for example, in the case of the first to fifth embodiments described above, the folded antenna conductor is a folded dipole antenna. However, the antenna conductor according to the embodiments of the present invention is not limited to this. The folded antenna conductor can also be other folded linear antennas, such as a folded monopole antenna, a folded inverted F antenna, etc.

[0127] Multiple embodiments are listed above to illustrate the present invention, but it is obvious to those skilled in the art that at least one other embodiment can be used as a whole or partially combined with a certain embodiment as a further embodiment of the present invention.

[0128] Industrial Applicability

[0129] The present invention can be applied to an antenna device that supports dual bands and includes a linear antenna conductor.

Claims

1. An antenna device is a dual-band supported antenna device capable of communicating at a first frequency in a specified frequency band and a second frequency in a frequency band higher than the specified frequency band. The antenna device includes: A ground conductor; A folded antenna conductor including a first linear portion and a second linear portion spaced apart from each other by folding and facing each other; An LC resonance circuit provided in the folded antenna conductor, the LC resonance circuit passing the first frequency and attenuating the second frequency; And A feeding point provided between the ground conductor and the folded antenna conductor, wherein a narrow gap portion is provided between the first linear portion and the second linear portion of the folded antenna conductor, and a distance at the narrow gap portion between the first linear portion and the second linear portion is smaller than a distance at other portions except the narrow gap portion between the first linear portion and the second linear portion, The folded antenna conductor includes a floating island portion provided between the first linear portion and the second linear portion, The narrow gap portion includes a first narrow gap portion formed between the floating island portion and the first linear portion and a second narrow gap portion formed between the floating island portion and the second linear portion.

2. The antenna device according to claim 1, characterized in that The first linear portion and the second linear portion extend parallel to each other, One of the first linear portion and the second linear portion includes a branch portion that extends toward the other of the first linear portion and the second linear portion and forms the narrow gap portion therebetween.

3. The antenna device according to claim 2, characterized in that A distance between the first linear portion and the second linear portion is greater than a line width of the first linear portion and a line width of the second linear portion.

4. The antenna device according to any one of claims 1 to 3, characterized in that It further has a capacitor chip provided in the narrow gap portion, and the capacitor chip connects the first linear portion and the second linear portion.

5. The antenna device according to any one of claims 1 to 3, characterized in that The LC resonance circuit includes a capacitor chip and an inductor chip arranged in parallel.

6. The antenna device according to any one of claims 1 to 3, characterized in that The folded antenna conductor is a folded dipole antenna.

7. The antenna device according to any one of claims 1 to 3, characterized in that The first frequency is a frequency in the 2.4 GHz frequency band, The second frequency is a frequency in the 5 GHz frequency band.

8. An antenna device is a dual-band supported antenna device capable of communicating at a first frequency in a specified frequency band and a second frequency in a frequency band higher than the specified frequency band. The antenna device includes: A ground conductor; A folded antenna conductor including a first linear portion and a second linear portion spaced apart from each other by folding and facing each other; An LC resonance circuit provided in the folded antenna conductor, the LC resonance circuit attenuating the first frequency and passing the second frequency; And A feeding point, which is arranged between the grounding conductor and the folded antenna conductor, wherein a narrow gap portion is arranged between the first linear portion and the second linear portion of the folded antenna conductor, and the interval between the first linear portion and the second linear portion at the narrow gap portion is smaller than the interval between the first linear portion and the second linear portion at other portions except the narrow gap portion, the LC resonant circuit is arranged at the narrow gap portion, the folded antenna conductor includes a floating island portion arranged between the first linear portion and the second linear portion, the narrow gap portion includes a first narrow gap portion formed between the floating island portion and the first linear portion and a second narrow gap portion formed between the floating island portion and the second linear portion.

9. A wireless communication device, comprising: the antenna device according to any one of claims 1 to 8; and a feeding circuit, which feeds power to the feeding point of the antenna device.

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