Multilayer substrate and antenna device

Abstract

A transmission line unit (2) of this multilayer substrate (101A) constitutes a strip line having an upper ground conductor (21), a lower ground conductor (22), and a signal line conductor (23). An antenna unit (1) has: a signal line conductor interlayer connection conductor (33) that electrically connects a radiation conductor (11) to the signal line conductor (23); and ground conductor interlayer connection conductors (31, 32) that electrically connect an upper surface annular ground conductor (12) to the lower ground conductor (22) and the upper ground conductor (21) of the transmission line unit (2). When viewed in the layering direction of a plurality of base materials, the entire surface of the radiation conductor (11) overlaps the lower ground conductor (22), and an end (21e) of the upper ground conductor (21) overlaps the signal line conductor (23) inside of an annular shape formed by the upper surface annular ground conductor (12) and is arranged at a position not overlapping the radiation conductor (11).

Description

Multilayer substrate and antenna device

[0001] The present invention relates to a multilayer substrate and an antenna device including the multilayer substrate.

[0002] Known inventions relating to a multilayer substrate constituting an antenna device or an antenna device constituted by a multilayer substrate include the antenna element described in Patent Document 1. Patent Document 1 discloses an antenna element constituted by a laminate including an insulator layer having a first ground conductor formed over almost the entire surface, an insulator layer having a radiating element formed in the center and a second ground conductor formed around the periphery, a plurality of insulators each having a ground conductor formed around the periphery, and an insulator layer having a lead conductor, the laminate including an interlayer connection conductor that electrically connects the tip of the lead conductor to the radiating conductor.

[0003] International Publication No. 2023 / 021929

[0004] A device in which an antenna section and a transmission line section are laminated as disclosed in Patent Document 1 can be used as a flexible lead device with an antenna, so that a highly stable antenna section can be constructed and it can be easily incorporated into a small electronic device.

[0005] However, because most of the radiating conductor overlaps with the upper ground conductor, this method cannot be applied to a multilayer substrate in which the transmission line section has a stripline structure and the lower ground conductor also serves as part of the antenna section, or to an antenna device including such a multilayer substrate. For example, if the transmission line section has a stripline structure, it is not possible to generate appropriate capacitive properties between the lower ground conductor and the radiating element to achieve radiation characteristics at a desired frequency.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a multilayer substrate in which a transmission line section has a stripline structure and its lower ground conductor also serves as part of an antenna section, and an antenna device including such a multilayer substrate.

[0007] (1) As an example of a multilayer substrate according to the present disclosure, there is provided an antenna unit including a plurality of laminated substrates, each of which includes a substrate having a radiation conductor and a substrate having an annular ground conductor surrounding the radiation conductor in a ring shape; and a transmission line unit for transmitting signals related to the antenna unit, wherein the transmission line unit forms a stripline having an upper ground conductor close to the antenna unit, a lower ground conductor distant from the antenna unit, and a signal line conductor disposed between the upper ground conductor and the lower ground conductor, and the antenna unit includes a signal line conductor inter-layer connection conductor for electrically connecting the radiation conductor to the signal line conductor, and a ground conductor inter-layer connection conductor for electrically connecting the annular ground conductor to the lower ground conductor and the upper ground conductor of the transmission line unit, wherein, as viewed in the stacking direction of the plurality of substrates, an entire surface of the radiation conductor overlaps the lower ground conductor, and, as viewed in the stacking direction of the plurality of substrates, an end of the upper ground conductor is disposed inside the ring formed by the annular ground conductor at a position that overlaps the signal line conductor but does not overlap the radiation conductor.

[0008] (2) An antenna device as an example of the present disclosure includes the multilayer substrate and is connected to a communication circuit.

[0009] According to the multilayer board of the present invention, a multilayer board can be configured in which the transmission line section has a stripline structure and the lower ground conductor also serves as part of the antenna section, and an antenna device including the multilayer board can be obtained.

[0010] FIGS. 1A and 1B are diagrams showing the structure of a multilayer substrate 101A constituting an antenna device according to a first embodiment. FIG. 2 is a longitudinal cross-sectional view of a multilayer substrate 101B constituting the first embodiment. FIG. 3A is a cross-sectional view of an antenna device using a multilayer substrate 102A constituting a third embodiment. FIG. 3B is a cross-sectional view of an antenna device using a multilayer substrate 102B constituting a third embodiment. FIG. 4A is a plan view of a multilayer substrate 103A, and FIG. 4B is a longitudinal cross-sectional view taken along line B-B in FIG. 4A. FIG. 5A is a longitudinal cross-sectional view taken along line Cs1-Cs1 in FIG. 4A, and FIG. 5B is a longitudinal cross-sectional view taken along line Cs2-Cs2 in FIG. 4A. FIG. 6 is a plan view of a multilayer substrate 103B constituting a third embodiment. FIGS. 7A and 7B are diagrams showing the structure of a multilayer substrate 104 constituting an antenna device according to a fourth embodiment. FIGS. 8A and 8B are diagrams showing the structure of a multilayer substrate 105 constituting an antenna device according to a fifth embodiment. 9(A), 9(B), and 9(C) are diagrams showing the structure of a multilayer substrate 106 constituting an antenna device according to a sixth embodiment. FIG. 10 is a plan view showing the structure of a multilayer substrate 107 constituting an antenna device according to a seventh embodiment. FIG. 11(A) is a plan view of a multilayer substrate 108 used as an antenna device according to an eighth embodiment, and FIG. 11(B) is a longitudinal cross-sectional view taken along line B-B in FIG. 11(A). FIG. 12(A) is a plan view of a multilayer substrate 109 used as an antenna device according to a ninth embodiment, and FIG. 12(B) is a longitudinal cross-sectional view taken along line B-B in FIG. 12(A). FIG. 13 is a block diagram showing the main configuration of an antenna device according to a tenth embodiment.

[0011] Hereinafter, several specific examples will be given with reference to the drawings to illustrate multiple embodiments for carrying out the present invention. The same reference numerals are used for the same parts in each drawing. For ease of explanation and understanding of the main points, the embodiments are shown divided into multiple embodiments for convenience of explanation, but partial substitution or combination of the configurations shown in different embodiments is possible. From the second embodiment onwards, a description of matters common to the first embodiment will be omitted, and only the differences will be described. In particular, similar effects resulting from similar configurations will not be mentioned in each embodiment.

[0012] 1(A) and 1(B) are diagrams showing the structure of a multilayer substrate constituting an antenna device according to a first embodiment. Fig. 1(A) is a plan view of the multilayer substrate, and Fig. 1(B) is a longitudinal cross-sectional view taken along the line B-B in Fig. 1(A). In Fig. 1(A) and Fig. 1(B), X, Y, and Z are symbols representing three orthogonal axial directions.

[0013] The multilayer substrate 101A has an antenna section 1 and a transmission line section 2. The antenna section 1 and the transmission line section 2 are each a laminate of multiple dielectric substrates on which various conductor patterns are formed. In Fig. 1(B), the layers of each substrate are not shown, and the entire laminate is shown as a single unit.

[0014] In the multilayer substrate 101A of this embodiment, the antenna unit 1 is soldered to the transmission line portion 2, thereby forming an antenna device including the transmission line portion 2 and the antenna portion 1.

[0015] The antenna unit 1 includes a substrate having a radiation conductor 11 provided on its upper surface and a substrate having an upper-surface annular ground conductor 12 that annularly surrounds the radiation conductor 11. Antenna unit-side ground terminals 61 and 62 and an antenna unit-side signal line terminal 63 are formed on the lower surface of the antenna unit 1. The various conductors and terminals are, for example, patterned copper foil.

[0016] The transmission line section 2 is a transmission line section that transmits signals related to the antenna section 1. This transmission line section 2 forms a stripline having an upper ground conductor 21 close to the antenna section 1, a lower ground conductor 22 distant from the antenna section 1, and a signal line conductor 23 disposed between the upper ground conductor 21 and the lower ground conductor 22. A transmission line section-side ground conductor inter-layer connection conductor 52 and a transmission line section-side signal line conductor inter-layer connection conductor 53 are formed on the transmission line section 2. In addition, a signal line conductor terminal 43 and a ground conductor terminal 42 are formed on the top surface of the transmission line section 2. The various conductors and terminals are, for example, patterned copper foil.

[0017] The antenna unit side ground terminal 61 of the antenna unit 1 is soldered to the upper ground conductor 21 via solder So, the antenna unit side ground terminal 62 is soldered to the ground conductor terminal 42 via solder So, and the antenna unit side signal line terminal 63 is soldered to the signal line conductor terminal 43 via solder So.

[0018] The antenna unit 1 has a signal line conductor inter-layer connection conductor 33 that electrically connects the radiation conductor 11 to the signal line conductor 23. The antenna unit 1 also has a ground conductor inter-layer connection conductor 31 that electrically connects the top surface annular ground conductor 12 to the upper ground conductor 21 of the transmission line unit 2. The antenna unit 1 also has a ground conductor inter-layer connection conductor 32 that electrically connects the top surface annular ground conductor 12 to the lower ground conductor 22 of the transmission line unit 2. These inter-layer connection conductors are inter-layer connection conductors.

[0019] When viewed in the stacking direction (Z direction) of the multiple base materials, the entire surface of the radiating conductor 11 overlaps the lower ground conductor 22. This structure forms an appropriate capacitance component (capacitance C1 shown in FIG. 1B ) between the lower ground conductor 22 and the radiating conductor 11.

[0020] In order to generate a small capacitance component between the radiating conductor 11 and the ground conductor to satisfy the radiation characteristics in the desired frequency band, it is generally necessary to increase the thickness of the antenna unit 1. However, in this embodiment, the distance between the radiating conductor 11 and the lower ground conductor 22 can be easily increased, so that the thickness of the antenna unit 1 can be reduced.

[0021] As shown in FIG. 1A , an end 21 e of the upper ground conductor 21 protrudes into the top-surface annular ground conductor 12 when viewed in the stacking direction (Z direction) of the multiple base materials.

[0022] Furthermore, the end 21e of the upper ground conductor 21 is positioned inside the ring-shaped portion formed by the top-surface annular ground conductor 12 so as to overlap the signal line conductor 23 but not the radiation conductor 11. In other words, the end 21e of the upper ground conductor 21 is positioned between the inner periphery 12i of the top-surface annular ground conductor 12 and the outer periphery 11o of the radiation conductor 11. This structure reduces unnecessary capacitance (capacitance C2 shown in FIG. 1B ) generated between the upper ground conductor 21 and the radiation conductor 11. This structure reduces the capacitance C2 generated between the upper ground conductor 21 and the radiation conductor 11 without increasing the thickness of the antenna unit 1.

[0023] 1B, the end 21e of the upper ground conductor 21 protrudes further toward the signal line conductor inter-layer connection conductor 33 than the end of the antenna unit-side ground terminal 61 formed on the underside of the antenna unit 1. This also suppresses unwanted coupling between the signal line conductor 23 and the ground conductor inter-layer connection conductor 31 or the antenna unit-side ground terminal 61.

[0024] According to this embodiment, a multilayer substrate can be configured in which the transmission line section 2 has a stripline structure and the lower ground conductor 22 also serves as part of the antenna section, and an antenna device including this multilayer substrate can be obtained.

[0025] Furthermore, by setting the dimensions and structure of the upper ground conductor 21 as described above, an appropriate capacitance component is generated between the radiation conductor 11 and each ground conductor, which eliminates the need to increase the thickness of the antenna unit 1. In other words, the antenna unit 1 can be made thinner.

[0026] Next, a multilayer substrate and an antenna device in which both an antenna section and a transmission line section are laminated and integrated will be exemplified.

[0027] 2 is a vertical cross-sectional view of the multilayer substrate 101B according to the first preferred embodiment, the cross-sectional position of which corresponds to FIG.

[0028] The multilayer substrate 101B has an antenna section 1 and a transmission line section 2, and is a laminate of a plurality of dielectric substrates on which various conductor patterns are formed.

[0029] The antenna unit 1 includes a base material having a radiation conductor 11 provided on its upper surface, and a base material having an annular ground conductor that surrounds the radiation conductor 11 in an annular shape.

[0030] The transmission line section 2 is a transmission line section that transmits signals related to the antenna section 1. This transmission line section 2 forms a stripline that has an upper ground conductor 21 close to the antenna section 1, a lower ground conductor 22 distant from the antenna section 1, and a signal line conductor 23 disposed between the upper ground conductor 21 and the lower ground conductor 22. In addition, the transmission line section 2 is formed with a transmission line section-side ground conductor inter-layer connection conductor 52 and a transmission line section-side signal line conductor inter-layer connection conductor 53.

[0031] The antenna unit 1 has a signal line conductor inter-layer connection conductor 33 that electrically connects the radiation conductor 11 to the signal line conductor 23. In addition, the multiple ground conductors 13 and the ground conductor inter-layer connection conductors 31, 32 that electrically connect these conductors in the stacking direction form an annular ground conductor.

[0032] In the examples shown in FIGS. 1A and 1B , the ground conductor 13 and the ground conductor inter-layer connection conductors 31 and 32 form an annular ground conductor. However, as disclosed in Patent Document 1, when the annular ground conductor is formed across multiple layers (by these multiple layers), the ground conductor 13 and the ground conductor inter-layer connection conductors 31 and 32 correspond to part of the “annular ground conductor” of the present invention.

[0033] As shown by the double-headed arrow in FIG. 2 , the end 21 e of the upper ground conductor 21 protrudes toward the signal line conductor inter-layer connection conductor 33 beyond the inside of the ring formed by the antenna-side ground conductor 13 and the ground conductor inter-layer connection conductors 31 and 32 formed below the antenna unit 1.

[0034] The multilayer substrate 101B also provides the same effects as the multilayer substrate 101A.

[0035] Second Embodiment In the second embodiment, a multilayer substrate and an antenna device are illustrated in which an antenna section and a transmission line section are formed using a laminate of base materials on which conductors are formed in which the positions of interlayer connection conductors are irregular when viewed from the stacking direction.

[0036] Fig. 3A is a cross-sectional view of an antenna device using a multilayer substrate 102A according to the third embodiment, and Fig. 3B is a cross-sectional view of an antenna device using a multilayer substrate 102B according to the third embodiment.

[0037] The multilayer substrates 102A and 102B have an antenna section 1 and a transmission line section 2, and are made up of a laminate of a plurality of dielectric substrates on which various conductor patterns are formed.

[0038] The antenna section 1 of the multilayer substrates 102A and 102B includes a base material having a radiating conductor 11 provided on its upper surface, and a base material having a ground conductor 13 and ground conductor inter-layer connection conductors 31 and 32 that surround the radiating conductor 11 in a ring shape.

[0039] The transmission line section 2 is a transmission line section that transmits signals related to the antenna section 1. This transmission line section 2 forms a stripline having an upper ground conductor 21 close to the antenna section 1, a lower ground conductor 22 distant from the antenna section 1, and a signal line conductor 23 disposed between the upper ground conductor 21 and the lower ground conductor 22. In addition, the transmission line section 2 is formed with a transmission line section-side ground conductor inter-layer connection conductor 52 and a transmission line section-side signal line conductor inter-layer connection conductor 53, which are formed by inter-layer connection conductors.

[0040] The antenna unit 1 has a signal line conductor inter-layer connection conductor 33 that electrically connects the radiation conductor 11 to the signal line conductor 23. The antenna unit 1 also has an annular ground conductor including a ground conductor 13 and ground conductor inter-layer connection conductors 31 and 32. The signal line conductor inter-layer connection conductor 33, the ground conductor inter-layer connection conductor 31, and the ground conductor inter-layer connection conductor 32 are laminated bodies of a conductive foil such as copper foil and an inter-layer connection conductor.

[0041] The above-mentioned interlayer connection conductors are formed by, for example, solidifying a conductive paste.

[0042] In the multilayer boards 102A and 102B of this embodiment, as in the first embodiment, when viewed in the stacking direction (Z direction) of the multiple base materials, the end 21 e of the upper ground conductor 21 is arranged inside the annular ground conductor including the ground conductor 13 and the ground conductor inter-layer connecting conductors 31 and 32 at a position that overlaps with the signal line conductor 23 but does not overlap with the radiation conductor 11.

[0043] As shown in the second embodiment, if the positions of the interlayer connection conductors are dispersed when viewed in the stacking direction (Z direction) of multiple substrates, damage to the interlayer connection conductors due to bending stress of the transmission line portion 2 can be made less likely.

[0044] In the multilayer substrate 102A shown in Fig. 3(A), the ground conductor inter-layer connection conductor 31 is connected to the upper ground conductor 21 via an inter-layer connection conductor, whereas in the multilayer substrate 102B shown in Fig. 3(B), there is no inter-layer connection conductor between the ground conductor inter-layer connection conductor 31 and the upper ground conductor 21. Stress concentrates at the boundary between the antenna unit 1 and the transmission line unit 2, but the structure of the multilayer substrate 102B shown in Fig. 3(B) can prevent cracks at the stress concentration area by eliminating the inter-layer connection conductor at the stress concentration area. Furthermore, by eliminating the inter-layer connection conductor, unwanted resonance can be prevented by extending the upper ground conductor 21, even if a potential difference occurs between the ground conductor 13 and the ground conductor inter-layer connection conductor 31.

[0045] Third Embodiment In a third embodiment, a multilayer substrate having an upper ground conductor with a different shape from the multilayer substrates exemplified so far will be described.

[0046] Figures 4(A), 4(B), 5(A), and 5(B) are diagrams showing the structure of a multilayer substrate 103A constituting an antenna device according to a third embodiment. Figure 4(A) is a plan view of the multilayer substrate 103A, and Figure 4(B) is a longitudinal cross-sectional view taken along line B-B in Figure 4(A). Figure 5(A) is a longitudinal cross-sectional view taken along line Cs1-Cs1 in Figure 4(A), and Figure 5(B) is a longitudinal cross-sectional view taken along line Cs2-Cs2 in Figure 4(A). In Figures 4(A), 4(B), 5(A), and 5(B), X, Y, and Z are symbols representing three orthogonal axial directions.

[0047] 1A and 1B according to the first embodiment, the multilayer substrate 103A has a different shape of the upper ground conductor 21. In the multilayer substrate 103A according to the third embodiment, when viewed in the stacking direction (Z direction) of the multiple base materials, the width of the upper ground conductor 21 located inside the ring-shaped top-surface annular ground conductor 12 is smaller than the width of the upper ground conductor 21 located outside the top-surface annular ground conductor 12.

[0048] In FIG. 4A , the width Wd of the upper ground conductor 21 located inside the ring-shaped portion formed by the top-surface annular ground conductor 12 is smaller than the width Wb of the upper ground conductor 21 located outside the top-surface annular ground conductor 12. In the multilayer substrate 101A shown in FIG. 1A , the width of the upper ground conductor 21 is the same as the outer width of the top-surface annular ground conductor 12. However, in the example shown in FIG. 4A , the width Wb of the upper ground conductor 21 located outside the top-surface annular ground conductor 12 is smaller than the outer width Wos of the top-surface annular ground conductor 12. Also, as shown in FIGS. 5A and 5B , the width of the lower ground conductor 22 is equal to the width Wos of the upper ground conductor 21. That is, the width of the lower ground conductor 22 located outside the top-surface annular ground conductor 12 is also smaller than the outer width Wos of the top-surface annular ground conductor 12. However, the shape of the lower ground conductor 22 is the same as the outer shape of the top-surface annular ground conductor 12 when viewed in the stacking direction (Z direction) of the multiple substrates. In the example shown in FIGS. 5A and 5B, the antenna section 1 is soldered to the transmission line section 2 at three locations.

[0049] 4(A), 4(B), 5(A), and 5(B) show examples in which the antenna section 1 is soldered to the transmission line section 2, but this embodiment can also be similarly applied to the case in which the transmission line section 2 and the antenna section 1 are configured as an integral laminate, as shown in FIG.

[0050] Fig. 6 is a plan view of a multilayer substrate 103B according to a third preferred embodiment. In the multilayer substrate 103A shown in Figs. 4A, 4B, 5A, and 5B, the width Wd of the upper ground conductor 21 located inside the ring-shaped portion formed by the top-surface annular ground conductor 12 is constant throughout the ring-shaped portion. However, in the example shown in Fig. 6, the width (width in the Y direction) of the upper ground conductor 21 located inside the ring-shaped portion formed by the top-surface annular ground conductor 12 tapers in the X direction. In the example shown in Fig. 6, the width Wd is trapezoidal.

[0051] According to the third embodiment, the upper ground conductor 21 extends to the minimum necessary width within the annular ground conductor, which reduces unnecessary coupling between the upper ground conductor 21 and the radiating conductor 11 (capacitance C2 shown in FIG. 1B ).

[0052] Fourth Embodiment In a fourth embodiment, a multilayer substrate having an upper ground conductor with a different shape from the multilayer substrates exemplified so far will be described.

[0053] 7A and 7B are diagrams showing the structure of a multilayer substrate 104 constituting an antenna device according to the fourth embodiment. Fig. 7A is a plan view of the multilayer substrate 104, and Fig. 7B is a longitudinal cross-sectional view taken along the line B-B in Fig. 7A.

[0054] 1A and 1B according to the first embodiment, the multilayer substrate 104 is different from the multilayer substrate 101A shown in Fig. 1A and 1B in particular in the shape of the signal line conductor 23. In the multilayer substrate 104 according to the fourth embodiment, when viewed in the stacking direction (Z direction), the line width (width in the Y direction) of a region with a length Le at the tip of the signal line conductor 23 is narrower than the main portion overlapping with the upper ground conductor 21.

[0055] According to this embodiment, it is possible to reduce unwanted coupling between the top-surface annular ground conductor 12 and the signal line conductor 23. Furthermore, by setting the width of the signal line conductor 23 facing the upper ground conductor 21 in the transmission line portion 2 to a specified value, it is possible to set the transmission line portion 2 to a desired characteristic impedance, and by reducing the line width of the signal line conductor 23 within the top-surface annular ground conductor 12, it is also possible to achieve impedance matching at the tip of the signal line conductor 23.

[0056] Fifth Embodiment In a fifth embodiment, a multilayer substrate having an upper ground conductor and a signal line conductor with different shapes from those of the multilayer substrates exemplified so far will be described.

[0057] 8A and 8B are diagrams showing the structure of a multilayer substrate 105 constituting an antenna device according to the fifth embodiment. Fig. 8A is a plan view of the multilayer substrate 105, and Fig. 8B is a longitudinal cross-sectional view taken along the line B-B in Fig. 8A.

[0058] 1A and 1B according to the first embodiment, the multilayer substrate 105 differs in the shapes of the upper ground conductor 21 and the signal line conductor 23. In the multilayer substrate 105 according to the fifth embodiment, when viewed in the stacking direction (Z direction), the middle portion of the signal line conductor 23 has a portion inside the ring shape formed by the top-surface ring-shaped ground conductor 12, and the line width (width in the Y direction) of the signal line conductor 23 that overlaps the upper ground conductor 21 is narrower than the line width of the signal line conductor 23 that does not overlap the upper ground conductor 21.

[0059] In the example shown in FIG. 8A , the middle portion of the signal line conductor 23 (the portion Lm shown in FIG. 8A ) is thinner than the central portion of the top-surface annular ground conductor 12 .

[0060] According to this embodiment, when viewed in the stacking direction (Z direction), the width of the portion of the upper ground conductor 21 facing the signal line conductor 23 is narrow in the narrowed portion of the signal line conductor 23, which makes it possible to reduce unwanted coupling between the radiation conductor 11 and the upper ground conductor 21. Furthermore, by changing the width of the upper ground conductor 21 in the narrowed portion of the signal line conductor 23, it is also possible to match the impedance between the transmission line unit 2 and the antenna unit 1.

[0061] Sixth Embodiment In a sixth embodiment, a multilayer substrate and an antenna device including a plurality of radiation electrodes applicable to different frequency bands will be exemplified.

[0062] Figures 9(A), 9(B), and 9(C) are diagrams showing the structure of a multilayer substrate 106 constituting an antenna device according to the sixth embodiment. Figure 9(A) is a plan view of the multilayer substrate, Figure 9(B) is a longitudinal cross-sectional view taken along the line B1-B1 in Figure 9(A), and Figure 9(C) is a longitudinal cross-sectional view taken along the line B2-B2 in Figure 9(A).

[0063] The multilayer substrate 106 has an antenna section 1 and a transmission line section 2. The antenna section 1 and the transmission line section 2 are each a laminate of a plurality of dielectric substrates on which various conductor patterns are formed.

[0064] In the present embodiment, the multilayer substrate 106 constitutes an antenna device including the transmission line portion 2 and the antenna portion 1 by soldering the antenna portion 1 to the transmission line portion 2. In the first embodiment, the antenna device is constituted with a single radiation conductor 11, but in the sixth embodiment, the antenna device is constituted with an upper-surface annular ground conductor 12 having two annular ground conductors, and two radiation conductors 11A and 11B. When viewed in the stacking direction (Z direction), the radiation conductor 11A is small and the radiation conductor 11B is large. The frequency band of the antenna constituted by the antenna portion 1 including the radiation conductor 11A and the lower ground conductor 22 is, for example, the 5 GHz band, and the frequency band of the antenna constituted by the antenna portion 1 including the radiation conductor 11B and the lower ground conductor 22 is, for example, the 2.4 GHz band.

[0065] 9B and 9C , when viewed in the stacking direction (Z direction) of the multiple substrates, the end 21Ae of the upper ground conductor 21A is located inside the first ring-shaped portion formed by the top-surface annular ground conductor 12 so as to overlap the signal line conductor 23A but not the radiation conductor 11A. The end 21Be of the upper ground conductor 21B is located inside the second ring-shaped portion formed by the top-surface annular ground conductor 12 so as to overlap the signal line conductor 23B but not the radiation conductor 11B.

[0066] In this way, when antennas operating in different frequency bands are combined, the protrusion length of the upper ground conductor 21B toward the inside of the annular ground conductor (in this example, the top-surface annular ground conductor 12) of the antenna operating in the lower frequency band is relatively short due to the positional relationship of the feed point to the radiating element when viewed in the stacking direction. The lower the frequency, the less likely coupling between the signal line and the annular ground conductor occurs, so the protrusion length can be short. By shortening the protrusion length in this way, unnecessary capacitive coupling between the protrusion of the upper ground conductor 21B and the radiating conductor 11B can be suppressed.

[0067] Seventh Embodiment In a seventh embodiment, a multilayer substrate and an antenna device in which a plurality of transmission line portions are connected to a single antenna portion will be exemplified.

[0068] FIG. 10 is a plan view showing the structure of a multilayer substrate 107 that constitutes an antenna device according to the seventh embodiment.

[0069] The multilayer substrate 107 has an antenna portion 1 and transmission line portions 2A and 2B. The antenna portion 1 and the transmission line portions 2A and 2B are each a laminate of a plurality of dielectric substrates on which various conductor patterns are formed.

[0070] In this embodiment, two transmission line portions 2A and 2B are provided for a single antenna portion 1, and the signal lines of the two transmission line portions 2A and 2B are connected to a plurality of feeding points of a radiation conductor 11, respectively.

[0071] 10 , when viewed in the stacking direction of the multiple substrates, the end 21Ae of the upper ground conductor 21A is located inside the ring-shaped portion formed by the top-surface annular ground conductor 12 so as to overlap the signal line conductor 23A but not the radiation conductor 11. In other words, the end 21Ae of the upper ground conductor 21A is located between the inner periphery 12i of the top-surface annular ground conductor 12 and the outer periphery 11o of the radiation conductor 11. Similarly, the end 21Be of the upper ground conductor 21B is located between the inner periphery 12i of the top-surface annular ground conductor 12 and the outer periphery 11o of the radiation conductor 11.

[0072] In this embodiment, since the feeding point for the radiation conductor 11 can be selected, it can also be used as an antenna for orthogonal polarization or circular polarization.

[0073] As exemplified in this embodiment, the structures shown in the first to sixth embodiments can also be applied to an antenna device that has a single radiation conductor 11 and a single top-surface annular ground conductor 12, but also has multiple signal line conductors.

[0074] Eighth Embodiment In the eighth embodiment, an antenna device including a parasitic element will be exemplified.

[0075] FIG. 11A is a plan view of a multilayer substrate 108 used as an antenna device according to the eighth embodiment, and FIG. 11B is a longitudinal cross-sectional view taken along the line BB in FIG. 11A.

[0076] In this embodiment, a parasitic element 11P is arranged around the radiating element (feed element) 11. Also, in the multilayer substrate 108 of this embodiment, the radiating conductor 11 is structured to be fed at two feeding points, similar to the example shown in FIG.

[0077] 11 , when viewed in the stacking direction (Z direction) of the multiple substrates, the end 21Ae of the upper ground conductor 21A is positioned inside the annular shape formed by the top-surface annular ground conductor 12 so as to overlap the signal line conductor 23A but not the parasitic element 11P. That is, the end 21Ae of the upper ground conductor 21A is positioned between the inner periphery of the top-surface annular ground conductor 12 and the parasitic element 11P. Similarly, the end 21Be of the upper ground conductor 21B is positioned inside the annular shape formed by the top-surface annular ground conductor 12 so as to overlap the signal line conductor 23B but not the parasitic element 11P. That is, the end 21Be of the upper ground conductor 21B is positioned between the inner periphery of the top-surface annular ground conductor 12 and the parasitic element 11P.

[0078] This structure provides the same effects as those shown in the first embodiment, etc. Furthermore, according to this embodiment, by arranging the parasitic elements 11P around the radiation conductor 11, the resonant frequency of these elements can be increased, thereby widening the bandwidth.

[0079] Ninth Embodiment In the ninth embodiment, an antenna device including a parasitic element different from the example shown in the eighth embodiment will be illustrated.

[0080] FIG. 12A is a plan view of a multilayer substrate 109 used as an antenna device according to the ninth embodiment, and FIG. 12B is a longitudinal sectional view taken along line BB in FIG. 12A.

[0081] In this embodiment, the radiating conductor (feed element) 11 is provided inside the antenna portion substrate laminate 10, and a parasitic element 11P, which has a relatively larger area than the radiating conductor 11, is arranged on the surface side of the radiating conductor 11. Also, in the multilayer substrate 109 of this embodiment, the radiating conductor 11 is structured to be fed at two feed points, similar to the examples shown in Figures 10 and 11. As shown in Figure 12(B) , there is capacitive coupling between the radiating conductor 11 and the parasitic element 11P.

[0082] 12 , when viewed in the stacking direction (Z direction) of the multiple substrates, the end 21Ae of the upper ground conductor 21A is positioned inside the annular shape formed by the top-surface annular ground conductor 12 so as to overlap the signal line conductor 23A but not the parasitic element 11P. That is, the end 21Ae of the upper ground conductor 21A is positioned between the inner periphery of the top-surface annular ground conductor 12 and the parasitic element 11P. Similarly, the end 21Be of the upper ground conductor 21B is positioned inside the annular shape formed by the top-surface annular ground conductor 12 so as to overlap the signal line conductor 23B but not the parasitic element 11P. That is, the end 21Be of the upper ground conductor 21B is positioned between the inner periphery of the top-surface annular ground conductor 12 and the parasitic element 11P.

[0083] This structure provides the same effects as those shown in the first embodiment, etc. Furthermore, according to this embodiment, by arranging the parasitic elements 11P that are capacitively coupled to the radiation conductor 11, the resonant frequency of these elements can be increased, thereby widening the bandwidth.

[0084] Tenth Embodiment In a tenth embodiment, an antenna device according to the present invention will be illustrated.

[0085] 13 is a block diagram showing the main components of an antenna device according to this embodiment. This antenna device 201 is composed of a transmission / reception circuit and an antenna. The transmission line and antenna are formed from a multilayer substrate according to the present invention, and are formed from the multilayer substrates shown in each of the first to ninth embodiments. The transmission / reception circuit handles high-frequency signals in the 1 GHz to 1 THz band, for example.

[0086] Finally, the present invention is not limited to the above-described embodiments. Those skilled in the art can make appropriate modifications and variations. The scope of the present invention is defined not by the above-described embodiments but by the claims. Furthermore, the scope of the present invention includes modifications and variations from the embodiments within the scope of the claims and their equivalents.

[0087] The multilayer substrate and antenna device of the present invention may be provided in the following forms.

[0088] <1> A multilayer substrate comprising: an antenna unit formed by stacking a plurality of substrates, the plurality of substrates including a substrate having a radiation conductor provided thereon and a substrate having an annular ground conductor provided annularly surrounding the radiation conductor; and a transmission line unit for transmitting signals related to the antenna unit, wherein the transmission line unit forms a stripline having an upper ground conductor close to the antenna unit, a lower ground conductor distant from the antenna unit, and a signal line conductor arranged between the upper ground conductor and the lower ground conductor, the antenna unit having a signal line conductor inter-layer connection conductor for electrically connecting the radiation conductor to the signal line conductor, and a ground conductor inter-layer connection conductor for electrically connecting the annular ground conductor to the lower ground conductor and the upper ground conductor of the transmission line unit, wherein an entire surface of the radiation conductor overlaps the lower ground conductor as viewed in a stacking direction of the plurality of substrates, and an end of the upper ground conductor is arranged inside the ring formed by the annular ground conductor at a position that overlaps the signal line conductor but does not overlap the radiation conductor as viewed in the stacking direction.

[0089] <2> The multilayer board according to <1>, wherein the ground conductor inter-layer connection conductor, which electrically connects the annular ground conductor to the upper ground conductor of the transmission line portion, is not present at a cross-sectional position along the signal line conductor.

[0090] <3> The multilayer substrate according to <1> or <2>, wherein, when viewed in the stacking direction, the width of the upper ground conductor located inside a ring formed by the annular ground conductor has a portion that is narrower than the width of the upper ground conductor located outside the annular ground conductor.

[0091] <4> The multilayer substrate according to any one of <1> to <3>, wherein, when viewed in the stacking direction, the signal line conductor that does not overlap the upper ground conductor inside the ring-shaped ground conductor has a line width that is narrower than the line width of the signal line conductor that overlaps the upper ground conductor.

[0092] <5> The multilayer board according to any one of <1> to <4>, wherein, inside a ring formed by the annular ground conductor, a line width of the signal line conductor that overlaps the upper ground conductor has a portion that is narrower than a line width of the signal line conductor that does not overlap the upper ground conductor, as viewed in the stacking direction.

[0093] <6> The multilayer substrate according to any one of <1> to <5>, wherein the antenna unit is made up of a plurality of antenna units formed on a predetermined base material among the plurality of base materials and used at different frequencies, the transmission line unit is made up of the transmission line unit provided for each of the plurality of antenna units, and a protrusion length of the upper ground conductor toward an inner side of the annular ground conductor is greater for the antenna units for a higher frequency band than for the antenna units for a lower frequency band, as viewed in the stacking direction.

[0094] <7> The multilayer board according to any one of <1> to <6>, wherein a single antenna unit includes a plurality of the transmission line units, signal lines of the plurality of transmission line units are connected to a plurality of feeding points of the radiation conductor, respectively, and an end of the upper ground conductor is arranged inside the annular ground conductor at a position that overlaps the signal line conductor but does not overlap the radiation conductor, as viewed in the stacking direction.

[0095] <8> The multilayer substrate according to any one of <1> to <7>, further comprising: a parasitic element formed on a substrate on which the radiating conductor is formed or on a substrate different from the substrate on which the radiating conductor is formed, wherein the parasitic element does not overlap the radiating conductor located inside the annular ground conductor when viewed in the stacking direction.

[0096] <9> An antenna device comprising the multilayer substrate according to any one of <1> to <8> and connected to a communication circuit.

[0097] DESCRIPTION OF SYMBOLS So...Solder 1...Antenna section 2...Transmission line section 2A, 2B...Transmission line section 10...Antenna section substrate laminate 11, 11A, 11B...Radiating conductor 11P...Passivation element 12...Upper surface annular ground conductor 13...Ground conductor 21, 21A, 21B...Upper ground conductor 21e...End of upper ground conductor 21Ae...End of upper ground conductor 21A 21Be...End of upper ground conductor 21B 22...Lower ground conductor 23, 23A, 23B...Signal line conductor 31, 32...Ground conductor inter-layer connection conductor 33...Signal line conductor inter-layer connection conductor 42...Ground conductor terminal 43...Signal line conductor terminal 52...Transmission line section side ground conductor inter-layer connection conductor 53...Transmission line section side signal line conductor inter-layer connection conductor 61, 62...Antenna section side ground terminal 63...Antenna section side signal line terminal 101A, 101B, 102A, 102B, 103A, 103B, 104, 105, 106, 107, 108, 109... multilayer substrate 201... antenna device

Claims

1. an antenna unit including a plurality of laminated substrates, each substrate including a substrate provided with a radiation conductor and a substrate provided with an annular ground conductor annularly surrounding the radiation conductor; and a transmission line unit for transmitting signals related to the antenna unit; the transmission line portion forms a stripline having an upper ground conductor close to the antenna portion, a lower ground conductor distant from the antenna portion, and a signal line conductor disposed between the upper ground conductor and the lower ground conductor; the antenna unit includes a signal line conductor inter-layer connection conductor that electrically connects the radiation conductor to the signal line conductor, and a ground conductor inter-layer connection conductor that electrically connects the annular ground conductor to the lower ground conductor and the upper ground conductor of the transmission line unit, When viewed in the stacking direction of the plurality of base materials, the entire surface of the radiation conductor overlaps the lower ground conductor, an end portion of the upper ground conductor is disposed inside the annular ground conductor in a position that overlaps the signal line conductor but does not overlap the radiation conductor, as viewed in the stacking direction. Multilayer board.

2. the ground conductor inter-layer connection conductor, which electrically connects the annular ground conductor to the upper ground conductor of the transmission line portion, is not present at a cross-sectional position along the signal line conductor; The multilayer substrate according to claim 1 .

3. When viewed in the stacking direction, the width of the upper ground conductor located inside the annular ground conductor has a narrower portion than the width of the upper ground conductor located outside the annular ground conductor. The multilayer substrate according to claim 1 or 2.

4. when viewed in the stacking direction, the signal line conductor that is located inside the annular ground conductor and does not overlap the upper ground conductor has a line width that is narrower than the line width of the signal line conductor that overlaps the upper ground conductor. The multilayer substrate according to claim 3 .

5. when viewed in the stacking direction, the signal line conductor has a portion inside the annular ground conductor where the signal line conductor overlaps the upper ground conductor and has a line width that is narrower than the line width of the signal line conductor that does not overlap the upper ground conductor. The multilayer substrate according to claim 3 .

6. the antenna unit is composed of a plurality of antenna units formed on a predetermined base material among the plurality of base materials and used at different frequencies, the transmission line section is configured by the transmission line section provided for each of the plurality of antenna sections, a protruding length of the upper ground conductor toward an inner side of the annular ground conductor in the stacking direction is greater in the antenna section for a higher frequency band than in the antenna section for a lower frequency band; The multilayer substrate according to claim 3 .

7. a single antenna portion has a plurality of transmission line portions; signal lines of the plurality of transmission line portions are connected to the plurality of feeding points of the radiation conductor, an end portion of the upper ground conductor is disposed inside the annular ground conductor at a position overlapping the signal line conductor but not overlapping the radiation conductor, as viewed in the stacking direction. The multilayer substrate according to claim 3 .

8. a parasitic element formed on a substrate on which the radiation conductor is formed or on a substrate different from the substrate on which the radiation conductor is formed, When viewed in the stacking direction, the parasitic element does not overlap the radiation conductor located inside the annular ground conductor. The multilayer substrate according to claim 3 .

9. An antenna device comprising the multilayer substrate according to claim 3 and connected to a communication circuit.