Wireless communication device

Abstract

A wireless communication device according to the present invention comprises: a base material that has a circumferential surface; an antenna conductor that has first and second ends and is provided to the base material so as to extend along the circumferential surface; and an RFIC chip that is provided to the base material and performs wireless communication using the antenna conductor. The first end and the second end of the antenna conductor face each other with a gap therebetween in the circumferential direction of the circumferential surface. The antenna conductor has a slit that begins from the first end and extends circumferentially toward the second end.

Description

wireless communication devices

[0001] The present disclosure relates to wireless communication devices.

[0002] For example, Patent Document 1 discloses a band-shaped wireless communication device equipped with a dipole antenna. In the wireless communication device described in Patent Document 1, dipole antennas are provided on a band-shaped sheet member, and extend from an RFIC chip provided in the center portion of the band-shaped sheet member in the longitudinal direction toward each of the outer edges of the sheet member in the longitudinal direction.

[0003] WO 2023 / 276583

[0004] Recently, there has been a demand for wireless communication devices that can communicate wirelessly over a substantially uniform communication distance in any direction (360 degrees). To address this, it has been considered to deform the strip-shaped wireless communication device equipped with the dipole antenna described in Patent Document 1 into a cylindrical shape. However, when the wireless communication device described in Patent Document 1 is deformed into a cylindrical shape, the two ends of the dipole antenna, which are the maximum voltage points, come closer to each other, generating a large capacitance between the ends. Therefore, when the wireless communication device described in Patent Document 1 is deformed into a cylindrical shape, the communication distance becomes extremely short compared to before the device is deformed into a cylindrical shape, meaning that wireless communication over a practical communication distance becomes impossible.

[0005] Therefore, an object of the present disclosure is to enable a wireless communication device to perform wireless communication over a substantially uniform communication distance in any direction of 360 degrees.

[0006] In order to solve the above technical problems, according to one aspect of the present disclosure, there is provided a wireless communication device comprising: a substrate having a circumferential surface; an antenna conductor having first and second ends and provided on the substrate so as to extend along the circumferential surface; and an RFIC chip provided on the substrate and performing wireless communication using the antenna conductor, wherein the first end and the second end of the antenna conductor face each other with a gap therebetween in the circumferential direction of the circumferential surface, and the antenna conductor has a slit that starts at the first end and extends in the circumferential direction toward the second end.

[0007] According to the present disclosure, a wireless communication device can perform wireless communication with a substantially uniform communication distance in any direction of 360 degrees.

[0008] 1. Perspective view of a wireless communication device according to a first embodiment of the present disclosure. 2. Perspective view of the wireless communication device according to the first embodiment, seen from a different viewpoint. 3. Perspective view of a base module in the wireless communication device according to the first embodiment. 4. Top view of the base module in the wireless communication device according to the first embodiment. 5. Perspective view of an RFIC module. 6. Top view of the RFIC module. 7. Exploded perspective view of the RFIC module. 8. Diagram showing the relationship between communication direction and communication distance in a wireless communication device. 9. Perspective view of a base module in a wireless communication device of a comparative example. 10. Perspective view of a base module in a wireless communication device according to a second embodiment. 11. Perspective view of a base module in a wireless communication device according to a third embodiment. 12. Perspective view of a base module in a wireless communication device according to a fourth embodiment. 13. Perspective view of a wireless communication device according to a fifth embodiment. 14. Top view of the base module in a wireless communication device according to the fifth embodiment. 15. Perspective view of a wireless communication device according to a sixth embodiment. 16. Top view of the base module in a wireless communication device according to the sixth embodiment.

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0010] 1 and 2 are perspective views of a wireless communication device according to a first embodiment of the present disclosure, viewed from different directions.

[0011] As shown in FIGS. 1 and 2 , a wireless communication device 10 according to the first embodiment is cylindrical. Specifically, the wireless communication device 10 includes a cylindrical substrate 12 having a circumferential surface 12 a, an antenna conductor 14 provided on the substrate 12, and an RFIC (Radio Frequency Integrated Circuit) chip 16 provided on the substrate 12 and performing wireless communication using the antenna conductor 14. The cylindrical substrate 12 is, for example, a cylindrical cap having an opening 12 b at one end. Note that arrow R in FIGS. 1 and 2 indicates the circumferential direction of the circumferential surface 12 a of the substrate 12. Furthermore, axis C is the central axis of the cylindrical substrate 12.

[0012] In this embodiment 1, the wireless communication device 10 is manufactured by deforming a strip-shaped base module 20 including an antenna conductor 14 and an RFIC chip 16 into a cylindrical shape and attaching the cylindrical base module 20 to a substrate 12.

[0013] Fig. 3 is a perspective view of the base module. Fig. 4 is a top view of the base module. Note that the X-Y-Z Cartesian coordinate system in the figures is intended to facilitate understanding of the present disclosure and does not limit the present disclosure. The X-axis direction indicates the longitudinal direction of the base module, the Y-axis direction indicates the lateral direction (width direction), and the Z-axis direction indicates the thickness direction.

[0014] As shown in FIGS. 3 and 4, the base module 20 has a strip-shaped sheet member 22 , an antenna conductor 14 provided on the sheet member 22 , and an RFIC chip 16 provided on the sheet member 22 .

[0015] In the first embodiment, the sheet member 22 of the base module 20 is rectangular and made of a resin such as PPS, PET, or PP. As shown in FIGS. 1 and 2 , the sheet member 22 is provided on the substrate 12 in a cylindrically deformed state. Specifically, the cylindrical sheet member 22 is provided on the substrate 12 so that its longitudinal direction (X-axis direction) is substantially parallel to the circumferential direction R of the circumferential surface 12 a of the substrate 12 and its width direction (Y-axis direction) is substantially parallel to the central axis C of the substrate 12. For example, the sheet member 22 is attached to the outer or inner surface of the cylindrical substrate 12. Alternatively, the sheet member 22, while still in a cylindrical shape, may be insert-molded into the substrate 12.

[0016] In the present embodiment, the antenna conductor 14 on the sheet member 22 is a rectangular conductor pattern made of a conductive material such as aluminum. The antenna conductor 14 extends in the longitudinal direction (X-axis direction) of the sheet member 22 and has a first end 14 a and a second end 14 b.

[0017] 1 and 2, when the cylindrically deformed sheet member 22 is provided on the substrate 12, the antenna conductor 14 extends along the circumferential surface 12a of the substrate 12. For example, the antenna conductor 14 extends in the circumferential direction R by an extension length equal to or greater than three-quarters of the circumferential length of the circumferential surface 12a. Also, as shown in Fig. 2, the first end 14a and the second end 14b of the antenna conductor 14 face each other in the circumferential direction R of the circumferential surface 12a with a distance D therebetween. Details of the distance D will be described later.

[0018] 3 and 4, the antenna conductor 14 has a slit 14c. In this specification, the term "slit" refers to a cutout portion that starts from the outer peripheral edge of the antenna conductor 14, extends substantially in the longitudinal direction (X-axis direction) of the antenna conductor 14 (i.e., the circumferential direction R of the circumferential surface 12a of the substrate 12), and has an end that is not connected to the outer peripheral edge (the end is located inside the outer peripheral edge).

[0019] 3 and 4 , the slit 14c is formed in the antenna conductor 14 so as to start from the first end 14a of the antenna conductor 14 and extend in the longitudinal direction (X-axis direction) (i.e., the circumferential direction R of the circumferential surface 12a of the substrate 12) toward the second end 14b. Specifically, in the case of the first embodiment, since the antenna conductor 14 is rectangular, the first and second ends 14a, 14b thereof each include first and second edges 14d, 14e extending in a direction intersecting the circumferential direction R of the circumferential surface 12a of the substrate 12 (i.e., the width direction (Y-axis direction) of the base module 20). The slit 14c starts from the first edge 14d at the first end 14a, extends in the longitudinal direction toward the second edge 14e at the second end 14b, and terminates near the second edge 14e.

[0020] In the first embodiment, the slits 14c extend in a meandering shape with a substantially constant width. The reason why the slits 14c extend in a meandering shape will be described later.

[0021] In the first embodiment, the antenna conductor 14 is magnetically coupled to the RFIC chip 16. For this reason, the RFIC chip 16 is modularized.

[0022] Fig. 5 is a perspective view of the RFIC module, Fig. 6 is a top view of the RFIC module, and Fig. 7 is an exploded perspective view of the RFIC module.

[0023] 5 to 7 , in the first embodiment, the RFIC chip 16 is modularized. That is, the RFIC chip 16 is incorporated into an RFIC module 30. The RFIC module 30 has a sheet member 32, the RFIC chip 16 provided on the sheet member 32, and a coil conductor 34 electrically connected to the RFIC chip 16.

[0024] The sheet member 32 has a rectangular shape and is made of an insulating material. The sheet member 32 has a first surface 32a and a second surface 32b opposite to the first surface 32a.

[0025] The RFIC chip 16 has first and second terminals 16 a and 16 b that are electrically connected to the coil conductor 34 .

[0026] In the first embodiment, the RFIC chip 16 is provided on a first surface 32a of the sheet member 32. Specifically, first, a first land conductor 36 electrically connected to one end of the coil conductor 34 and a second land conductor 38 electrically connected to the other end of the coil conductor 34 are provided on the first surface 32a of the sheet member 32. These first and second land conductors 36, 38 are, for example, conductor patterns.

[0027] A first terminal 16a of the RFIC chip 16 is fixed and electrically connected to a first land conductor 36 via, for example, a solder material. A second terminal 16b of the RFIC chip 16 is fixed and electrically connected to a second land conductor 38 via, for example, a solder material.

[0028] The coil conductor 34 is magnetically coupled to the antenna conductor 14 of the base module 20 .

[0029] In the first embodiment, the coil conductor 34 includes a first spiral conductor 40 provided on the first surface 32a of the sheet member 32 and a second spiral conductor 42 provided on the second surface 32b of the sheet member 32. In a plan view of the sheet member 32 (viewed in the Z-axis direction), the first spiral conductor 40 and the second spiral conductor 42 partially overlap each other. These first and second spiral conductors 40, 42 are, for example, conductor patterns.

[0030] In addition, in the case of this embodiment 1, the coil conductor 34 includes an interlayer connecting conductor 44 such as a through-hole conductor that penetrates the sheet member 32 in the thickness direction (Z-axis direction) and electrically connects one end 40a of the first spiral conductor 40 and one end 42a of the second spiral conductor 42.

[0031] As shown in FIG. 6, in a plan view of the sheet member 32 (viewed in the Z-axis direction), the RFIC chip 16, a first land conductor 36, and a second land conductor 38 are arranged within the opening 34a of the coil conductor 34.

[0032] A first connecting conductor 46 is provided on the first surface 32a of the sheet member 32 to electrically connect the other end 40b of the first spiral conductor 40 of the coil conductor 34 to the first land conductor 36. The first connecting conductor 46 is, for example, a conductor pattern.

[0033] A second connecting conductor 48 is provided on the second surface 32b of the sheet member 32 to electrically connect the other end 42b of the second spiral conductor 42 of the coil conductor 34 to the second land conductor 38. The second connecting conductor 48 is, for example, a conductor pattern. The second connecting conductor 48 is electrically connected to the second land conductor 38 via an interlayer connecting conductor 50, such as a through-hole conductor, that penetrates the sheet member 32.

[0034] 3 and 4, the antenna conductor 14 has an opening 14f to magnetically couple with the coil conductor 34 in the RFIC module 30. In the first embodiment, the RFIC module 30 is attached to the portion of the sheet member 22 exposed by the opening 14f of the antenna conductor 14, for example, with an insulating adhesive. The opening 14f is formed in the antenna conductor 14 with a size and shape that surrounds the rectangular sheet member 32 of the RFIC module 30 with a gap therebetween. In other words, the opening edge that defines the opening 14f surrounds the coil conductor 34 of the RFIC module 30 with a gap therebetween.

[0035] In this wireless communication device 10 (i.e., base module 20), when a signal (radio wave) is received, a current flows in the antenna conductor 14. The current flowing along the edge of the opening 14f generates a magnetic field that passes through the opening 14f. This magnetic field generates a current in the coil conductor 34 of the RFIC module 30. The RFIC chip 16 is activated by the current supply, and supplies the coil conductor 34 with a current corresponding to a transmission signal in response to the received signal. In response to this current supply, the coil conductor 34 generates a magnetic field corresponding to the transmission signal. This magnetic field causes a current corresponding to the transmission signal to flow in the antenna conductor 14, and the antenna conductor 14 emits a transmission signal (radio wave) in response to the received signal.

[0036] 1 and 2, in the first embodiment, the antenna conductor 14 extends along the circumferential surface 12a of the substrate 12. As a result, the wireless communication device 10 can communicate wirelessly over a substantially uniform communication distance in any normal direction of the circumferential surface 12a.

[0037] Fig. 8 is a diagram showing the relationship between the communication direction and communication distance of a wireless communication device. Fig. 8 shows the communication direction and communication distance when viewed from the extension direction of the central axis C of the cylindrical substrate 12. The direction of an angle of zero in Fig. 8 is the direction in which the RFIC module 30 is present.

[0038] 8, the communication distance is slightly shorter in the angular direction (0 degrees) where the RFIC module 30 is present and in the opposite angular direction (180 degrees) than in other angular directions, but there is no angular direction where the communication distance is extremely short. Therefore, the wireless communication device 10 according to the first embodiment can perform wireless communication over a substantially uniform communication distance in any normal direction of the circumferential surface 12a of the substrate 12. The reason for this will be explained with reference to a comparative example.

[0039] FIG. 9 is a perspective view of a base module in a wireless communication device of the comparative example.

[0040] 9 , similarly to the first embodiment, the base module 120 of the comparative example includes a belt-shaped sheet member 122, an antenna conductor 114 provided on the sheet member 122, and an RFIC chip 16 that is provided on the sheet member 122 and performs wireless communication using the antenna conductor 114. In the case of the base module 120 of the comparative example, the antenna conductor 114 is a dipole antenna that extends from the RFIC chip 16 provided in the central portion of the belt-shaped sheet member 122 in the longitudinal direction (X-axis direction) toward each of the outer ends of the sheet member 122 in the longitudinal direction.

[0041] 9, when a radio wave is received, a current flows from the first end 114a to the second end 114b of the dipole antenna conductor 114, or vice versa. That is, the first end 114a and the second end 114b are the maximum voltage points.

[0042] When the base module 120 of this comparative example is cylindrically shaped so that the first end 114a and the second end 114b face each other with a gap between them, a large capacitance is generated between the first end 114a and the second end 114b. For example, if the potential of the first end 114a is +V and the potential of the second end 114b is −V, a potential difference of Δ2V is generated between these ends 114a and 114b, creating a large capacitance between them. As a result, the current flowing through the antenna conductor 114 is consumed by the capacitance, and the communication distance of the antenna conductor 114 is drastically reduced compared to before it was cylindrically shaped.

[0043] In contrast, in the first embodiment, as shown in FIG. 4 , the first end 14a of the antenna conductor 14 is separated into two portions 14g and 14h by a slit 14c. When such an antenna conductor 14 receives radio waves, current flows from one portion 14g at the first end 14a to the other portion 14h, or vice versa. Specifically, the current flows from one portion 14g along the slit 14c toward the second end 14b, turns back at the second end 14b, and then flows from the second end 14b along the slit 14c toward the other portion 14h. In other words, currents flow in opposite directions in the opposite sides of the antenna conductor 14, facing each other across the slit 14c. Furthermore, the portions 14g and 14h at the first end 14a are the maximum voltage points.

[0044] When the base module 20 of the first embodiment is cylindrically shaped and the first end 14a and the second end 14b are spaced apart and face each other, no large capacitance is generated between them, unlike the comparative example. For example, if the potential of one portion of the first end 14a is +V and the potential of the other portion is −V, the potential of the second end 14b becomes approximately zero. As a result, the potential difference between the first end 14a and the second end 14b, which face each other and are spaced apart, becomes ΔV. As a result, a smaller capacitance is generated between the first end 14a and the second end 14b of the antenna conductor 14 than in the comparative example. As a result, the communication distance of the antenna conductor 114 according to the first embodiment is not significantly reduced compared to before it was cylindrically shaped, and is substantially uniform in both normal directions of the circumferential surface 12a of the substrate 12.

[0045] A capacitance also occurs between the opposite ends of the antenna conductor 14 that face each other across the slit 14c. However, this capacitance is for achieving impedance matching between the antenna conductor 14 and the RFIC chip 16, i.e., for adjusting the resonant frequency to the communication frequency. For this impedance matching, the extension length of the slit 14c is adjusted to a predetermined extension length that corresponds to the resonant frequency. By making the slit 14c of the predetermined extension length meandering, the size of the antenna conductor 14, i.e., the size of the base module 20, is made more compact than when it is linear.

[0046] 2, by making the base module 20 cylindrical, it is preferable that the distance D between the first end 14a and the second end 14b, which face each other in the circumferential direction R, be larger than the width W of the slit 14c. On the other hand, if the distance D is smaller than the width W, it will affect the impedance matching between the antenna conductor 14 and the RFIC chip 16, causing a change in the resonant frequency. In other words, the capacitance between the first end 14a and the second end 14b, as well as the capacitance between the opposite sides of the antenna conductor 14 facing each other across the slit 14c, plays a major role in impedance matching.

[0047] According to the first embodiment as described above, the wireless communication device 10 can perform wireless communication over a substantially uniform communication distance in any direction of 360 degrees.

[0048] (Embodiment 2) Embodiment 2 is an improved version of the above-described embodiment 1. Therefore, the following description of embodiment 2 will focus on the differences from embodiment 1. Note that components that are substantially the same as those of the wireless communication device 10 according to embodiment 1 are denoted by the same reference numerals.

[0049] FIG. 10 is a perspective view of a base module in a wireless communication device according to the second embodiment.

[0050] 10 , a base module 220 in a wireless communication device according to the second embodiment, which is deformed into a cylindrical shape so as to fit along the circumferential surface of a cylindrical substrate, has a rectangular antenna conductor 214 extending in the longitudinal direction (X-axis direction) of the base module 220. The antenna conductor 214 includes a meandering slit 214c that starts from a first end 214a and extends toward a second end 214b.

[0051] Specifically, the first end 214a and the second end 214b of the antenna conductor 214 include first and second edges 214d, 214e that extend in a direction intersecting the circumferential direction of the circumferential surface of the substrate (i.e., the width direction (Y-axis direction) of the base module 220). The antenna conductor 214 also includes two side edges 214j, 214k that extend from both ends of the first edge 214d in the circumferential direction (i.e., the longitudinal direction (X-axis direction) of the base module 220) and connect to both ends of the second edge 214e. The slit 214c starts from a portion of one side edge 214j of the first end 214a near the first edge 214d and extends in the circumferential direction toward the second end 214b.

[0052] Like the wireless communication device 10 according to the first embodiment, the wireless communication device according to the second embodiment can also perform wireless communication over a substantially uniform communication distance in any direction of 360 degrees.

[0053] (Embodiment 3) In the case of the above-described embodiment 1, as shown in Figures 3 and 4, the RFIC chip 16 (i.e., the RFIC module 30) is disposed near the center of the slit 14c of the antenna conductor 14. In contrast, in the case of embodiment 3, the RFIC chip is disposed within the end of the slit. Therefore, embodiment 3 will be described focusing on this difference. Note that components that are substantially the same as the components of the wireless communication device 10 according to embodiment 1 are assigned the same reference numerals.

[0054] FIG. 11 is a perspective view of a base module in a wireless communication device according to the third embodiment.

[0055] 11 , a base module 320 in a wireless communication device according to the third embodiment, which is deformed into a cylindrical shape so as to fit along the circumferential surface of a cylindrical substrate, has an antenna conductor 314 extending in the longitudinal direction (X-axis direction) of the base module 320. The antenna conductor 314 includes a meandering slit 314c that starts from a first end 314a and extends toward a second end 314b.

[0056] The RFIC module 30 including the RFIC chip is disposed within the end of the slit 314c located at the second end 314b, so that the coil conductor (see FIG. 5) within the RFIC module 30 is magnetically coupled with the portion of the antenna conductor 314 surrounding the end of the slit 314c.

[0057] Like the wireless communication device 10 according to the first embodiment, the wireless communication device according to the third embodiment can also perform wireless communication over a substantially uniform communication distance in any direction of 360 degrees.

[0058] (Embodiment 4) In the case of the above-described embodiment 1, as shown in Fig. 4, the slit 14c of the antenna conductor 14 starts from the first end 14a and extends toward the second end 14b without making a U-turn. In contrast, the slit in embodiment 4 makes a U-turn. Therefore, embodiment 4 will be described focusing on this difference. Note that components that are substantially the same as the components of the wireless communication device 10 according to embodiment 1 are assigned the same reference numerals.

[0059] FIG. 12 is a perspective view of a base module in a wireless communication device according to the fourth embodiment.

[0060] As shown in FIG. 12 , a base module 420 in a wireless communication device according to the fourth embodiment is deformed into a cylindrical shape so as to fit along the circumferential surface of a cylindrical substrate. The base module 420 has an antenna conductor 414 extending in the longitudinal direction (X-axis direction) of the base module 420. The antenna conductor 414 includes a slit 414c that starts at a first end 414a and extends toward a second end 414b. The slit 414c also makes a U-turn at the second end 414b and extends back to the first end 414a. The slit 414c terminates midway toward the first end 414a. That is, the slit 414c is roughly “J” shaped. Furthermore, in the case of the fourth embodiment, the width of the slit 414c gradually decreases toward the end.

[0061] The RFIC module 30 including the RFIC chip is disposed within the end of the slit 414c, so that the coil conductor (see FIG. 5) within the RFIC module 30 is magnetically coupled with the portion of the antenna conductor 414 surrounding the end of the slit 414c.

[0062] Like the wireless communication device 10 according to the first embodiment, the wireless communication device according to the fourth embodiment can also perform wireless communication over a substantially uniform communication distance in any direction of 360 degrees.

[0063] 2 , in the case of the first embodiment described above, by making the base module 20 cylindrical, the distance D between the first end 14 a and the second end 14 b that face each other in the circumferential direction R is set to a size that prevents a large capacitance from forming between them. However, as the distance D increases, the communication distance of the wireless communication device 10 decreases in the normal direction of the portion of the sheet member 22 located between the first end 14 a and the second end 14 b compared to other directions, and eventually a null point occurs, where communication is impossible. The wireless communication device according to the fifth embodiment has a structure that suppresses the occurrence of such a null point.

[0064] Fig. 13 is a perspective view of a wireless communication device according to embodiment 5. Fig. 14 is a top view of a base module in the wireless communication device according to embodiment 5.

[0065] As shown in Figures 13 and 14, the base module 520 of the wireless communication device 510 according to the fifth embodiment has a strip-shaped sheet member 522, an antenna conductor 514 provided on the sheet member 522, and an RFIC module 30 provided on the sheet member 522.

[0066] The antenna conductor 514 extends in the longitudinal direction (X-axis direction) of the sheet member 522 and has a first end 514a and a second end 514b. As shown in Fig. 13 , when the cylindrically deformed sheet member 522 is provided on the base material 512, the first end 514a and the second end 514b face each other with a gap in between in the circumferential direction R.

[0067] The antenna conductor 514 also has a slit 514c formed to extend from the first end 514a toward the second end 514b in the longitudinal direction (X-axis direction) (i.e., the circumferential direction R of the circumferential surface 512a of the base material 512). A portion of the slit 514c is enlarged, and the RFIC module 30 is disposed in the enlarged portion.

[0068] Furthermore, the first end 514a and the second end 514b of the antenna conductor 514 each include a first and a second edge 514d, 514e. In the case of the fifth embodiment, the first and the second edge 514d, 514e each have a shape different from the linear first and second edges 14d, 14e of the antenna conductor 14 of the first embodiment shown in FIGS. 2 and 4 . Specifically, the first and the second edges 514d, 514e of the antenna conductor 514 in the fifth embodiment are not linear, but have portions that approach each other in the circumferential direction R at an interval of a distance D2, and portions that are separated from each other in the circumferential direction R at an interval of a distance D1 that is larger than the distance D2. This allows the first and the second end 514a, 514b to approach each other in the circumferential direction R to an extent that the occurrence of null points can be suppressed. The increase in capacitance between the first and second ends 514 a, 514 b due to this proximity is suppressed because the lengths (lengths in the width direction (Y-axis direction) of the base module 520) of the portions (both side portions in the case of the fifth embodiment) that are close to each other and face each other with a distance D2 between them are short. In other words, even if the first and second ends 514 a, 514 b are close enough to prevent the occurrence of null points, portions (central portions in the case of the fifth embodiment) of each end are separated from each other by a distance D1, thereby suppressing the capacitance between the first and second ends 514 a, 514 b (compared to when the first and second edges 514 d, 514 e are straight).

[0069] In the fifth embodiment, the first edge 514d of the first end 514a and the second edge 514e of the second end 514b of the antenna conductor 514 are both concave when viewed in the thickness direction (Z-axis direction) of the base module 520, as shown in FIG. 14 . However, the shapes of the first and second edges 514d, 514e are not limited to being concave. For example, one of the first and second edges 514d, 514e may be linear and the other may be convex.

[0070] Furthermore, in the case of the fifth embodiment, as shown in Fig. 14, the end of the slit 514c on the first end 514a side of the antenna conductor 514 branches into two. One of the slit branches, a first slit branch 514i, is connected to the edge 514d. The other, a second slit branch 514j, terminates at a predetermined length without being connected to the outer peripheral edge of the antenna conductor 514. The role of this second slit branch 514j will be described.

[0071] As shown in FIG. 14 , the first end 514a of the antenna conductor 514 is separated into two portions 514g and 514h by a slit 514c. When the wireless communication device 510 transmits or receives radio waves, current flows from one portion 514g along the slit 514c toward the second end 514b, turns back at the second end 514b, and flows from the second end 514b along the slit 514c toward the other portion 514h. The second slit branch 514j serves to equalize the first electrical length between the one portion 514g and the second end 514b at the first end 514a and the second electrical length between the other portion 514h and the second end 514b at the first end 514a. That is, the second electrical length is adjusted by adjusting the length of the second slit branch 514j, thereby bringing the second electrical length closer to the first electrical length. In the fifth embodiment, the length of the second slit branch 514j is adjusted to a predetermined length, thereby making the first electrical length and the second electrical length substantially equal, thereby making the communication distance on one side of the extending direction of the central axis C of the cylindrical base material 512 of the wireless communication device 510 substantially equal to the communication distance on the other side.

[0072] (Embodiment 6) The wireless communication device according to this embodiment 6 is a modified example of the wireless communication device according to the above-mentioned embodiment 5, and is configured so that the communication distance is even more equal in any direction within 360 degrees when viewed in the direction in which the central axis of the wireless communication device extends.

[0073] Fig. 15 is a perspective view of a wireless communication device according to embodiment 6. Fig. 16 is a top view of a base module in the wireless communication device according to embodiment 6.

[0074] As shown in Figures 15 and 16, the base module 620 of the wireless communication device 610 according to the sixth embodiment has a strip-shaped sheet member 622, an antenna conductor 614 provided on the sheet member 622, and an RFIC module 30 provided on the sheet member 622.

[0075] The antenna conductor 614 extends in the longitudinal direction (X-axis direction) of the sheet member 622 and has a first end 614a and a second end 614b. As shown in Fig. 15 , when the cylindrically deformed sheet member 622 is provided on the base material 612, the first end 614a and the second end 614b face each other with a gap in between in the circumferential direction R.

[0076] The antenna conductor 614 also has a meandering slit 614c formed to extend from the first end 614a to the second end 614b in the longitudinal direction (X-axis direction) (i.e., the circumferential direction R of the circumferential surface 612a of the substrate 612). A portion of the slit 614c is enlarged, and the RFIC module 30 is disposed in the enlarged portion.

[0077] In the sixth embodiment, unlike the fifth embodiment, the base module 620 has a sub-antenna conductor 652. As shown in Fig. 16 , the sub-antenna conductor 652 extends in the longitudinal direction (X-axis direction) of the sheet member 622 along the antenna conductor 614. The sub-antenna conductor 652 starts to extend from a first end 614a of the antenna conductor 614 and extends in a direction (X-axis direction) toward a second end 614b of the antenna conductor 614. In the sixth embodiment, the antenna conductor 614 and the sub-antenna conductor 652 are integrated as a single conductor pattern.

[0078] Such a sub-antenna conductor 652 substantially eliminates the directivity of the communication distance of the wireless communication device 610 when viewed in the extending direction of the central axis C. In other words, when viewed in the extending direction of the central axis C, the communication distance is substantially the same in any direction within 360 degrees.

[0079] 15 and 16 , in a wireless communication device 610 according to the sixth embodiment, two sub-antenna conductors 652 are provided on a sheet member 622 so as to sandwich an antenna conductor 614 therebetween. However, only one of the sub-antenna conductors 652 may be provided.

[0080] Although the present disclosure has been described above with reference to a number of embodiments, the present disclosure is not limited thereto. For example, in the first embodiment, the sheet member 32 of the RFIC module 30 and the sheet member 22 of the base module 20 are separate. However, the RFIC module 30 and the base module 20 may be integrated by providing coil conductors 34 or the like on the front and rear surfaces of the sheet member 22 and mounting the RFIC chip 16 thereon.

[0081] In the first embodiment described above, as shown in FIGS. 3 and 4 , the antenna conductor 14 and the RFIC chip 16 are magnetically coupled via the coil conductor 34. However, the embodiments of the present disclosure are not limited to this. For example, the RFIC chip may be provided so as to straddle the slit in the antenna conductor, or an extraction electrode portion may be formed in the slit electrode of the antenna conductor and the RFIC chip may be provided on the slit electrode. Specifically, first and second terminals of the RFIC chip are fixed to both sides of the slit or to the ends of the extraction electrode, respectively, via solder or the like. This directly connects the RFIC chip and the antenna conductor.

[0082] For impedance matching, the RFIC chip and the antenna conductor may be connected via a coil conductor (inductance). For example, an RFIC module is created that includes an RFIC chip, a first coil conductor having one end connected to a first terminal of the RFIC chip and the other end connected to the antenna conductor, and a second coil conductor having one end connected to a second terminal of the RFIC chip and the other end connected to the antenna conductor. The RFIC module is then mounted on the antenna conductor so as to straddle the slit. This allows for a smaller base module than when the RFIC chip and the antenna conductor are directly connected without a coil conductor (inductance). If a coil conductor is not used, the antenna conductor must be enlarged (i.e., the antenna length must be increased) to match the impedance between the RFIC chip and the antenna conductor.

[0083] That is, various aspects of the present disclosure are as follows.

[0084] A first aspect is a wireless communication device having: a substrate having a circumferential surface; an antenna conductor having first and second ends and provided on the substrate so as to extend along the circumferential surface; and an RFIC chip provided on the substrate and performing wireless communication using the antenna conductor, wherein the first end and the second end of the antenna conductor face each other with a gap between them in the circumferential direction of the circumferential surface, and the antenna conductor has a slit that starts at the first end and extends in the circumferential direction toward the second end.

[0085] A second aspect is the wireless communication device of the first aspect, wherein the first end of the antenna conductor includes a first edge extending in a direction intersecting the circumferential direction, and the slit starts from the first edge at the first end and extends in the circumferential direction toward the second end.

[0086] A third aspect is the wireless communication device of the second aspect, wherein the second end of the antenna conductor includes a second edge extending in a direction intersecting the circumferential direction, and the first edge of the first end and the second edge of the second end each have a portion that is close to each other in the circumferential direction and a portion that is far from each other in the circumferential direction.

[0087] A fourth aspect is the wireless communication device of the second aspect, wherein the slit branches into a first slit branch and a second slit branch at the first end, the first slit branch connects to the first edge at the first end, and the second slit branch terminates at a predetermined length.

[0088] A fifth aspect is a wireless communication device of the first aspect, in which the first end of the antenna conductor includes a first edge extending in a direction intersecting the circumferential direction and two side edges extending in the circumferential direction from both ends of the first edge, and the slit starts from a portion of one of the side edges at the first end near the first edge and extends in the circumferential direction toward the second end.

[0089] A sixth aspect is a wireless communication device according to any one of the first to fifth aspects, wherein the circumferential distance between the first end and the second end is greater than the width of the slit at the first end.

[0090] A seventh aspect is the wireless communication device of any one of the first to sixth aspects, wherein the antenna conductor extends in the circumferential direction with an extension length that is ¾ or more of the circumferential length of the circumferential surface.

[0091] An eighth aspect is the wireless communication device according to any one of the first to seventh aspects, wherein the slit is meandering.

[0092] A ninth aspect is a wireless communication device according to any one of the first to eighth aspects, which has an RFIC module including the RFIC chip and a coil conductor electrically connected to the RFIC chip, wherein the antenna conductor has an opening that communicates with the slit and is defined by an opening edge that surrounds the coil conductor of the RFIC module at a distance, and wherein the coil conductor and the opening edge of the opening in the antenna conductor are magnetically coupled.

[0093] A tenth aspect is a wireless communication device according to any one of the first to ninth aspects, further comprising a strip-shaped sheet member on which the antenna conductor and the RFIC chip are provided, the sheet member being provided on the substrate in a cylindrically deformed state.

Claims

1. A wireless communication device comprising: a substrate having a circumferential surface; an antenna conductor having first and second ends and provided on the substrate so as to extend along the circumferential surface; and an RFIC chip provided on the substrate and performing wireless communication using the antenna conductor, wherein the first end and the second end of the antenna conductor face each other with a gap in between in the circumferential direction of the circumferential surface, and the antenna conductor has a slit that starts at the first end and extends in the circumferential direction toward the second end.

2. The wireless communication device of claim 1, wherein the first end of the antenna conductor includes a first edge extending in a direction intersecting the circumferential direction, and the slit begins at the first edge at the first end and extends in the circumferential direction toward the second end.

3. The wireless communication device of claim 2, wherein the second end of the antenna conductor includes a second edge extending in a direction intersecting the circumferential direction, and the first edge of the first end and the second edge of the second end each have a portion that is close to each other in the circumferential direction and a portion that is far from each other in the circumferential direction.

4. The wireless communication device of claim 2, wherein the slit branches into a first slit branch and a second slit branch at the first end, the first slit branch connects to the first edge at the first end, and the second slit branch terminates at a predetermined length.

5. A wireless communication device as described in claim 1, wherein the first end of the antenna conductor includes a first edge extending in a direction intersecting the circumferential direction and two side edges extending in the circumferential direction from both ends of the first edge, and the slit starts at a portion of one of the side edges at the first end near the first edge and extends in the circumferential direction toward the second end.

6. A wireless communication device as claimed in any one of claims 1 to 5, further comprising a sub-antenna conductor beginning to extend from the first end of the antenna conductor and extending along the antenna conductor in a direction toward the second end.

7. A wireless communication device according to any one of claims 1 to 6, wherein the circumferential spacing between the first end and the second end is greater than the width of the slit at the first end.

8. A wireless communication device according to any one of claims 1 to 7, wherein the antenna conductor extends in the circumferential direction for an extension length that is 3 / 4 or more of the circumferential length of the circumferential surface.

9. A wireless communication device according to any one of claims 1 to 8, wherein the slit is meandering.

10. A wireless communication device according to any one of claims 1 to 9, comprising an RFIC module including the RFIC chip and a coil conductor electrically connected to the RFIC chip, the antenna conductor communicating with the slit and having an opening defined by an opening edge surrounding the coil conductor of the RFIC module at a distance, and the coil conductor and the opening edge of the opening in the antenna conductor are magnetically coupled.

11. A wireless communication device according to any one of claims 1 to 10, further comprising a strip-shaped sheet member on which the antenna conductor and the RFIC chip are provided, the sheet member being provided on the substrate in a cylindrically deformed state.

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