Antenna substrate, antenna, and electronic device

Abstract

In the present invention, a radiation conductor RE is formed on the upper surface of an antenna substrate 101, and a power supply electrode FP1, a first ground conductor GC11, and a second ground conductor GC12 are formed on the lower surface of the antenna substrate 101. A second ground connection conductor GC12C for connecting the second ground conductor GC12 and a ground part GP of the radiation conductor RE is formed in the antenna substrate 101. Furthermore, a power supply electrode connection conductor FPC for connecting the power supply electrode FP1 and a power supply point FP of the radiation conductor RE is formed in the antenna substrate 101. The first ground conductor GC11 faces the radiation conductor RE. The first ground conductor GC11 and the second ground conductor GC12 are separated on the lower surface of the antenna substrate 101.

Description

Antenna substrate, antenna and electronic device

[0001] The present invention relates to an antenna substrate used in an antenna, an antenna using the substrate, and an electronic device equipped with the antenna.

[0002] Patent Document 1 discloses an antenna circuit in which a part of a conductor surface serving as a radiating conductor arranged parallel to a ground conductor surface is connected to the ground conductor surface and a high-frequency signal is fed to another part of the ground conductor surface, and in which one end of the radiating conductor is folded back toward the ground conductor surface and the feeding part.

[0003] In this way, an antenna in which one end of the conductor surface that serves as the radiation conductor is folded back toward the ground conductor surface has a large capacity in the gap between the folded part and the ground conductor surface, making it possible to construct an antenna that is small overall.

[0004] Japanese Unexamined Patent Publication No. 4-183101

[0005] In an antenna in which one end of the radiating conductor is folded back toward the ground conductor surface, the end of the radiating conductor where the electric field is concentrated, i.e., the folded electrode, is close to the ground conductor. This reduces the effective thickness (height) of the antenna substrate. This narrows the frequency band in which the desired antenna characteristics (reflection loss and radiation efficiency) can be obtained.

[0006] Therefore, an object of the present invention is to provide an antenna substrate that can be used to construct an antenna that is small overall while ensuring a frequency band that provides desired antenna characteristics, an antenna that includes this antenna substrate, and an electronic device that includes the antenna substrate.

[0007] (a) An antenna as an example of the present disclosure is an antenna substrate including an insulator and a conductor each forming a layer, and mounted on a mounting board; a radiation conductor formed on the antenna substrate using the conductor; a feeding electrode, a first ground conductor, and a second ground conductor each made of the conductor for mounting are formed on a bottom surface of the antenna substrate, which is the mounting surface for the mounting board; a second ground connection conductor is formed inside the antenna substrate, having a first end connected to a ground point of the radiation conductor and a second end connected to the second ground conductor; a feeding electrode connection conductor is formed inside the antenna substrate, having a first end connected to the radiation conductor and a second end connected to the feeding electrode; the feeding electrode is an electrode conducting to the feeding point of the radiation conductor; the second ground conductor is an electrode conducting to the ground portion of the radiation conductor; and there is no conduction between the first and second ground conductors.

[0008] (b) An electronic device as an example of the present disclosure includes the antenna and another substrate on which the antenna is mounted.

[0009] According to the present invention, an antenna substrate capable of forming an antenna that can ensure a frequency band in which desired antenna characteristics can be obtained while being made small overall, an antenna including this antenna substrate, and an electronic device including the antenna substrate are obtained.

[0010] FIG. 1A is a cross-sectional view of the antenna substrate 101. FIG. 1B is a cross-sectional view of a mounting substrate 201 on which the antenna substrate 101 is mounted. FIG. 1C is a cross-sectional view of an antenna 301 configured by mounting the antenna substrate 101 on the mounting substrate 201. FIG. 2A is a plan view of the antenna substrate 101. FIG. 2B is a plan view of the mounting substrate 201 on which the antenna substrate 101 is mounted. FIG. 2C is a plan view of the antenna 301 configured by mounting the antenna substrate 101 on the mounting substrate 201. FIG. 3 is a diagram showing the path of a current flowing through the short-circuit element of the antenna and the electric field generated between the vicinity of the open end of the radiation conductor RE and the antenna substrate-side first ground conductor GC11. FIG. 4 is a cross-sectional view of an antenna 302 configured by mounting the antenna substrate 102 on the mounting substrate 201 according to the second embodiment. FIG. 5 is a cross-sectional view of an antenna 303 according to the third embodiment. FIG. 6 is a cross-sectional view of an antenna 304 according to the fourth embodiment. Fig. 7(A) is a cross-sectional view of an antenna 305A according to a fifth embodiment, and Fig. 7(B) is a cross-sectional view of another antenna 305B according to the fifth embodiment. Fig. 8 is a cross-sectional view of an antenna 306 according to a sixth embodiment. Fig. 9(A) is a plan view of an antenna substrate 107. Fig. 9(B) is a plan view of a mounting substrate 207 on which the antenna substrate 107 is mounted. Fig. 9(C) is a cross-sectional view of an antenna 307 configured by mounting the antenna substrate 107 on the mounting substrate 207. Fig. 10 is a plan view of an antenna 308 according to an eighth embodiment. Fig. 11 is a cross-sectional view of an electronic device 509 according to a ninth embodiment.

[0011] Hereinafter, several specific examples will be given with reference to the drawings to illustrate several embodiments for carrying out the present invention. The same reference numerals are used for the same parts in each drawing. To facilitate explanation and understanding of the main points, the embodiments for carrying out the present invention are shown divided into several embodiments for the sake of convenience. However, partial omission, substitution, or combination of the configurations shown in different embodiments is possible. From the second embodiment onwards, descriptions 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] First Embodiment In a first embodiment, the structures of an antenna substrate and an antenna will be illustrated with reference to FIGS. 1(A), 1(B), 1(C), 2(A), 2(B), 2(C), and 3.

[0013] Fig. 1A is a cross-sectional view of an antenna substrate 101. Fig. 1B is a cross-sectional view of a mounting substrate 201 on which the antenna substrate 101 is mounted. Fig. 1C is a cross-sectional view of an antenna 301 configured by mounting the antenna substrate 101 on the mounting substrate 201.

[0014] The antenna substrate 101 has an upper surface and a lower surface. Similarly, the mounting substrate 201 has an upper surface and a lower surface. Here, the "upper surface" refers to the XY outer surface at the top in the Z direction, and the "lower surface" refers to the XY outer surface at the bottom in the Z direction.

[0015] Fig. 2A is a plan view of the antenna substrate 101. Fig. 2B is a plan view of a mounting substrate 201 on which the antenna substrate 101 is mounted. Fig. 2C is a plan view of an antenna 301 configured by mounting the antenna substrate 101 on the mounting substrate 201.

[0016] The antenna substrate 101 shown in Figures 1A and 2A is a laminate including an antenna substrate resin layer 10 and a conductor, and is an antenna substrate to be mounted on a mounting substrate 201. The antenna substrate resin layer 10 corresponds to the "insulator" of the present invention in the antenna substrate. A radiation conductor RE made of a conductor is formed on the upper surface of this antenna substrate 101.

[0017] An antenna substrate side feeding electrode FP1, an antenna substrate side first ground conductor GC11, and an antenna substrate side second ground conductor GC12, each made of a conductor and intended for mounting, are formed on the underside of the antenna substrate 101, which is the mounting surface for the mounting board 201.

[0018] Inside the antenna substrate 101, an antenna substrate side second ground connection conductor GC12C is formed, the first end of which is connected to the ground portion GP of the radiation conductor RE and the second end of which is connected to the antenna substrate side second ground conductor GC12.

[0019] The antenna substrate-side second ground connecting conductors GC12C are preferably arranged in the Y direction at intervals of less than half the wavelength at the antenna's resonant frequency, because the arrangement of these antenna substrate-side second ground connecting conductors GC12C does not substantially function as an open end.

[0020] Inside the antenna substrate 101, a feeding electrode connecting conductor FPC is formed, the first end of which is connected to the radiation conductor RE and the second end of which is connected to the antenna substrate side feeding electrode FP1.

[0021] Both the antenna substrate second ground connection conductor GC12C and the feed electrode connection conductor FPC are formed of a plurality of conductive foils 4 and a plurality of interlayer connection conductors 5.

[0022] The antenna substrate-side feeding electrode FP1 is an electrode that is electrically connected to the feeding point FP of the radiation conductor RE. The antenna substrate-side first ground conductor GC11 is an electrode that faces the radiation conductor. The antenna substrate-side second ground conductor GC12 is an electrode that is electrically connected to the ground portion GP of the radiation conductor RE via the antenna substrate-side second ground connecting conductor GC12C.

[0023] The antenna substrate-side first ground conductor GC11 and the antenna substrate-side second ground conductor GC12 are separated on the bottom surface of the antenna substrate 101. That is, there is no electrical continuity between the antenna substrate-side first ground conductor GC11 and the antenna substrate-side second ground conductor GC12.

[0024] 1B and 2B are laminated bodies including a mounting substrate resin layer 20 and a conductor, which form a layer. The mounting substrate resin layer 20 corresponds to the "insulator" of the mounting substrate according to the present invention.

[0025] A mounting-board-side first ground conductor GC21 that is electrically connected to the antenna-substrate-side first ground conductor GC11 is formed on the upper surface of the mounting substrate 201. A mounting-board-side second ground conductor GC22 that is electrically connected to the antenna-substrate-side second ground conductor GC12 is also formed on the upper surface of the mounting substrate 201. Furthermore, a mounting-board-side feeding electrode FP2 that is electrically connected to the antenna-substrate-side feeding electrode FP1 is also formed on the upper surface of the mounting substrate 201.

[0026] A ground conductor layer GC2 is formed on the lower surface of the mounting substrate 201. A second ground connection conductor GC22C is formed inside the mounting substrate 201 to electrically connect the mounting substrate second ground conductor GC22 to the ground conductor layer GC2.

[0027] A first ground connection conductor that provides electrical continuity between the mounting-board first ground conductor GC21 and the mounting-board second ground conductor GC22 is formed on the mounting board 201. Although not shown in Figures 1B and 2B, for example, an interlayer connection conductor that provides electrical continuity between the mounting-board first ground conductor GC21 and the ground conductor layer GC2 is formed on the mounting board resin layer 20. This interlayer connection conductor corresponds to the "ground connection conductor" according to the present invention.

[0028] A signal line conductor SL is formed inside the mounting substrate 201. A first end of the signal line conductor SL is connected to the mounting substrate-side feeding electrode FP2 via an interlayer connection conductor, and a second end of the signal line conductor SL is connected to the signal terminal electrode SE via an interlayer connection conductor.

[0029] A stripline is formed by the signal line conductor SL, the mounting-board first ground conductor GC21, the ground conductor layer GC2, and the mounting-board resin layer 20. The signal terminal electrode SE is used for inputting and / or outputting an antenna signal.

[0030] In the first embodiment, the mounting board first ground conductor GC21 is also formed inside the mounting board 201 .

[0031] The antenna substrate resin layer 10 and the mounting substrate resin layer 20 are, for example, sheets of liquid crystal polymer resin or polyimide. Each electrode and conductor layer is, for example, Cu foil, Ag foil, Au foil, etc., and is attached to one side of the resin layer before lamination to create a multilayer substrate.

[0032] 1C and 2C , the antenna-substrate-side first ground conductor GC11 is electrically and mechanically joined via a conductive bonding material BM to the mounting-substrate-side first ground conductor GC21 of the mounting substrate 201. Also, the antenna-substrate-side feeding electrode FP1 is electrically and mechanically joined via a conductive bonding material BM to the mounting-substrate-side feeding electrode FP2 of the mounting substrate 201. The conductive bonding material BM is, for example, a heat-melting metal material such as solder.

[0033] In the state shown in FIGS. 1C and 2C, the ground portion GP of the radiation conductor RE is electrically connected to the ground conductor layer GC2 via the antenna substrate-side second ground connecting conductor GC12C, the antenna substrate-side second ground conductor GC12, the conductive bonding material BM, the mounting substrate-side second ground conductor GC22, and the second ground connecting conductor GC22C.

[0034] In the state shown in FIGS. 1C and 2C, the antenna 301 functions as a planar inverted-F antenna (PIFA).

[0035] The resonant frequency of the antenna 301 according to this embodiment is, for example, in the 40 GHz band or the 27 GHz band, although it goes without saying that the present invention is not limited to these frequency bands.

[0036] The thickness of the mounting substrate 201 is thinner than the thickness of the antenna substrate 101. Since the mounting substrate 201 has a larger plane area than the antenna substrate 101, the mounting substrate 201 being thinner than the antenna substrate 101 can be made flexible (bendable).

[0037] When viewed in the stacking direction (Z direction) of the mounting board 201 and the antenna board 101, the mounting board first ground conductor GC21 includes the outer periphery of the radiation conductor RE of the antenna board and overlaps with substantially the entire radiation conductor RE of the antenna board 101. Since the mounting board first ground conductor GC21 with respect to the radiation conductor RE affects the radiation efficiency of the antenna, this structure achieves high radiation efficiency.

[0038] FIG. 3 shows the path of the current flowing through the short-circuit element of the planar inverted-F antenna, and the electric field generated between the vicinity of the open end of the radiation conductor RE and the antenna substrate-side first ground conductor GC11.

[0039] 3 indicates that the long, L-shaped arrow is regarded as the path length (effective antenna length) from the ground conductor layer GC2 to the open end of the radiation conductor RE. Since the antenna-substrate-side first ground conductor GC11 and the antenna-substrate-side second ground conductor GC12 are separated on the underside of the antenna substrate, the second ground connection conductor GC22C formed on the mounting board 201 acts as a part of the short-circuit element.

[0040] According to this embodiment, a planar inverted-F antenna having a long effective antenna length can be configured even when a thin antenna substrate 101 is used. This allows the capacitance generated intensively between the vicinity of the open end of the radiation conductor RE and the antenna substrate-side first ground conductor GC11 to be kept low while maintaining a small overall size. This broadens the frequency band with a low S11 parameter, thereby broadening the frequency band with low reflection loss due to impedance mismatch with the feed circuit. Furthermore, even when a thin antenna substrate 101 is used, the distance between the vicinity of the open end of the radiation conductor RE and the antenna substrate-side first ground conductor GC11 can be increased, ensuring the desired radiation efficiency over a wide frequency band.

[0041] Second Embodiment In a second embodiment, an antenna substrate and an antenna in which one end of a radiation conductor is folded back toward the ground conductor surface will be exemplified.

[0042] FIG. 4 is a cross-sectional view of an antenna 302 configured by mounting an antenna substrate 102 on a mounting substrate 201 according to the second embodiment.

[0043] An antenna substrate side feeding electrode FP1, an antenna substrate side first ground conductor GC11, and an antenna substrate side second ground conductor GC12, each made of a conductor, are formed on the underside of the antenna substrate 102, which is the mounting surface for the mounting board 201.

[0044] The mounting board 201 is provided with a first ground connection conductor that electrically connects the mounting board first ground conductor GC21 and the mounting board second ground conductor GC22.

[0045] Inside the antenna substrate 102, an antenna substrate side second ground connection conductor GC12C is formed, the first end of which is connected to the ground portion GP of the radiation conductor RE and the second end of which is connected to the antenna substrate side second ground conductor GC12.

[0046] Inside the antenna substrate 102, a feeding electrode connecting conductor FPC is formed, the first end of which is connected to the radiation conductor RE and the second end of which is connected to the antenna substrate side feeding electrode FP1.

[0047] Furthermore, radiation conductors RE21 and RE22 are formed inside the antenna substrate 102. These radiation conductors RE21 and RE22 are folded back portions of the radiation conductor. That is, the radiation conductors RE21 and RE22 fold back the vicinity of the open end of the radiation conductor.

[0048] The other configuration is the same as that of the antenna 301 shown in FIG. 1C in the first embodiment.

[0049] The three thick arrows shown in FIG. 4 indicate the electric field generated between the vicinity of the open ends of the radiation conductors (RE1, RE21, RE22) and the antenna substrate first ground conductor GC11.

[0050] In this way, by forming a folded portion in the radiation conductor, when the end of the folded portion where the electric field concentrates and the first ground conductor GC11 on the antenna substrate side are brought into close proximity, the frequency band in which a predetermined radiation efficiency is maintained generally becomes narrower. However, as in the example shown in FIG. 3 , in the short-circuit element for forming an inverted-F antenna, the effective antenna length from the ground conductor layer GC2 to the open ends of the radiation conductors (RE1, RE21, RE22) can be increased, and therefore the frequency band in which a predetermined low reflection loss and a predetermined high radiation efficiency can be ensured can be expanded.

[0051] Third Embodiment In a third embodiment, an antenna having a mounting board structure different from those in the first and second embodiments will be illustrated.

[0052] 5 is a cross-sectional view of an antenna 303 according to the third embodiment. The mounting substrate 203 is composed of a base substrate 203B that serves as the base of the mounting substrate, and an interposer substrate 203A mounted on top of the base substrate 203B. The antenna substrate 101 is mounted on the top surface of the interposer substrate 203A.

[0053] The configuration of the base substrate 203B is similar to that of the mounting substrate 201 shown in the first and second embodiments. The configuration of the antenna substrate 101 is similar to that of the antenna substrate 101 shown in the first embodiment.

[0054] The interposer substrate 203A includes conductive members that relay the mounting substrate-side power supply electrode FP2, the mounting substrate-side first ground conductor GC21, and the mounting substrate-side second ground conductor GC22, which are formed on the upper surface of the base substrate 203B, to the antenna substrate-side power supply electrode FP1, the antenna substrate-side first ground conductor GC11, and the antenna substrate-side second ground conductor GC12, which are formed on the lower surface of the antenna substrate 101, respectively.

[0055] In the example shown in FIG. 5, the electrodes and conductor layers on the upper and lower surfaces of interposer substrate 203A are arranged at the same pitch, but the electrodes and conductor layers on the upper and lower surfaces of interposer substrate 203A may be arranged at different pitches.

[0056] In this way, the mounting substrate 203 may be provided with an interposer substrate 203A. According to the third embodiment, the length of the path of the current flowing through the short-circuit element of the planar inverted-F antenna, as indicated by the arrow in Fig. 3, can be made longer, thereby effectively widening the frequency band with low reflection loss and the frequency band with high radiation efficiency.

[0057] Fourth Embodiment In a fourth embodiment, an antenna structure having a mounting substrate with a different shape from those of the embodiments shown so far will be illustrated.

[0058] 6 is a cross-sectional view of an antenna 304 according to the fourth embodiment. The basic configuration of the mounting substrate 204 is similar to that of the mounting substrate 201 shown in the first and second embodiments. The configuration of the antenna substrate 101 is similar to that of the antenna substrate 101 shown in the first embodiment.

[0059] In this antenna 304, the mounting substrate 204 has a bent portion BD. That is, the mounting substrate 204 is flexible and is bent at the bent portion BD. In this example, the entire substrate is bent by 90 degrees.

[0060] According to the fourth embodiment, the angle of the antenna substrate 101 can be tilted by bending the mounting substrate 204, which increases the degree of freedom in setting the antenna directivity. Furthermore, when this antenna 304 is incorporated into the housing of an electronic device, it can be incorporated by inserting it into a gap within the housing.

[0061] Fifth Embodiment In a fifth embodiment, an antenna structure having a mounting substrate with a different shape from those of the embodiments shown so far will be illustrated.

[0062] FIG. 7A is a cross-sectional view of an antenna 305A according to the fifth embodiment, and FIG. 7B is a cross-sectional view of another antenna 305B according to the fifth embodiment.

[0063] 7A , a mounting-board-side first ground conductor GC21 that is electrically connected to the antenna-board-side first ground conductor GC11 is formed on the upper surface of the mounting board 205A. A mounting-board-side second ground conductor GC22 that is electrically connected to the antenna-board-side second ground conductor GC12 is also formed on the upper surface of the mounting board 205A. Furthermore, a mounting-board-side feeding electrode FP2 that is electrically connected to the antenna-board-side feeding electrode FP1 is also formed on the upper surface of the mounting board 205A.

[0064] A ground conductor layer GC2 is formed on the bottom surface of the mounting board 205A. A second ground connection conductor GC22C is formed inside the mounting board 205A to electrically connect the mounting board second ground conductor GC22 and the ground conductor layer GC2.

[0065] The mounting board 205A is provided with a first ground connection conductor that electrically connects the mounting board first ground conductor GC21 and the mounting board second ground conductor GC22.

[0066] A signal line conductor SL is formed inside the mounting substrate 205A. A first end of the signal line conductor SL is connected to the mounting substrate-side feeding electrode FP2 via an interlayer connection conductor, and a second end of the signal line conductor SL is connected to the signal terminal electrode SE via an interlayer connection conductor.

[0067] 1C , the mounting-board-side second ground conductor GC22 extends along the upper surface of the mounting board 205A. Therefore, the path electrically connecting the ground portion GP of the radiation conductor RE to the ground conductor layer GC2 via the antenna-board-side second ground connecting conductor GC12C, the antenna-board-side second ground conductor GC12, the conductive bonding material BM, the mounting-board-side second ground conductor GC22, and the second ground connecting conductor GC22C is longer by the extension amount of the mounting-board-side second ground conductor GC22. The other configuration of the mounting board 205A is similar to that of the mounting board 201 shown in FIG. 1B.

[0068] 7B , a mounting-board-side first ground conductor GC21 that is electrically connected to the antenna-substrate-side first ground conductor GC11 is formed on the upper surface of the mounting board 205B. A mounting-board-side second ground conductor GC22A that is electrically connected to the antenna-substrate-side second ground conductor GC12 is also formed on the upper surface of the mounting board 205B. A mounting-board-side feeding electrode FP2 that is electrically connected to the antenna-substrate-side feeding electrode FP1 is also formed on the upper surface of the mounting board 205B.

[0069] A ground conductor layer GC2 is formed on the bottom surface of the mounting board 205B. A second ground connection conductor GC22B that is electrically connected to the mounting board second ground conductor GC22A is formed inside the mounting board 205B.

[0070] Furthermore, inside the mounting board 205B, a second ground connection conductor GC22C is formed to electrically connect the second ground connection conductor GC22B and the ground conductor layer GC2.

[0071] The mounting board 205B is formed with a second ground connecting conductor GC22B extending in the layer direction, and therefore the path electrically connecting the ground portion GP of the radiation conductor RE to the ground conductor layer GC2 is longer by the extension amount of the second ground connecting conductor GC22B. The other configurations of the mounting board 205B are similar to those of the mounting board 201 shown in FIG.

[0072] In the examples shown in FIGS. 7A and 7B, the second ground connection conductor extends in the X direction on the top surface of the mounting substrate 205A or on an inner layer of the mounting substrate 205B, but this extension direction may also be in the Y direction or another direction along the X-Y plane.

[0073] According to the fifth embodiment, the path length of the short-circuit element for forming an inverted-F antenna can be increased not only in the thickness direction (Z direction) of the mounting substrate but also in the surface direction or layer direction (direction along the X-Y plane) of the mounting substrate, thereby effectively widening the frequency band with low reflection loss and widening the frequency band with high radiation efficiency.

[0074] Sixth Embodiment In a sixth embodiment, an antenna characterized by the width of a second ground connection conductor that is a part of a short-circuit element for an inverted-F antenna will be exemplified.

[0075] 8 is a cross-sectional view of an antenna 306 according to a sixth embodiment. An antenna substrate-side feeding electrode FP1, an antenna substrate-side first ground conductor GC11, and an antenna substrate-side second ground conductor GC12 are formed on the underside of an antenna substrate 106. An antenna substrate-side second ground connecting conductor GC12C is formed inside the antenna substrate 106. The first end is connected to the ground portion GP of the radiation conductor RE and the second end is connected to the antenna substrate-side second ground conductor GC12. Also formed inside the antenna substrate 106 is a feeding electrode connecting conductor FPC. The first end is connected to the radiation conductor RE and the second end is connected to the antenna substrate-side feeding electrode FP1.

[0076] A mounting-board-side first ground conductor GC21 that is electrically connected to the antenna-substrate-side first ground conductor GC11 is formed on the upper surface of the mounting substrate 206. A mounting-board-side second ground conductor GC22 that is electrically connected to the antenna-substrate-side second ground conductor GC12 is also formed on the upper surface of the mounting substrate 206. Furthermore, a mounting-board-side feeding electrode FP2 that is electrically connected to the antenna-substrate-side feeding electrode FP1 is also formed on the upper surface of the mounting substrate 206.

[0077] A ground conductor layer GC2 is formed on the underside of the mounting board 206. A second ground connection conductor GC22C is formed inside the mounting board resin layer of the mounting board 206, providing electrical continuity between the mounting board second ground conductor GC22 and the ground conductor layer GC2. Furthermore, a first ground connection conductor GC21C is formed inside the mounting board resin layer of the mounting board 206, providing electrical continuity between the mounting board first ground conductor GC21 and the ground conductor layer GC2. This first ground connection conductor GC21C corresponds to the "ground connection conductor" according to the present invention.

[0078] A signal line conductor SL is formed inside the mounting substrate 206. A first end of the signal line conductor SL is connected to the mounting substrate-side feeding electrode FP2 via an interlayer connection conductor, and a second end of the signal line conductor SL is connected to the signal terminal electrode SE via an interlayer connection conductor.

[0079] Unlike the example shown in FIG. 1B etc., the second ground connecting conductor GC22C that is electrically connected to the antenna substrate side second ground connecting conductor GC12 is configured as a connecting conductor that is thinner than the antenna substrate side second ground connecting conductor GC12C.

[0080] According to the sixth embodiment, the inductance component of the path of the short-circuiting element for forming an inverted-F antenna can be increased on the mounting board 206 side. As a result, even if the thickness of the mounting board 206 is thin, that is, even if the second ground connection conductor GC22C is short, the effective length of the short-circuiting element is increased, enabling further miniaturization of the antenna board 106. Furthermore, because the mounting board 206 can also be made thinner, the overall size of the antenna 306 can be reduced.

[0081] Seventh Embodiment In the seventh embodiment, an antenna characterized by the configuration of a second ground connection conductor that is a part of a short-circuit element for an inverted-F antenna will be exemplified.

[0082] Fig. 9A is a plan view of the antenna substrate 107. Fig. 9B is a plan view of a mounting substrate 207 on which the antenna substrate 107 is mounted. Fig. 9C is a cross-sectional view of an antenna 307 configured by mounting the antenna substrate 107 on the mounting substrate 207.

[0083] As shown in Figures 9(A) and 9(C), the configuration of the antenna substrate 107 is the same as that of the antenna substrate 106 shown in Figure 8. Furthermore, as shown in Figures 9(B) and 9(C), the second ground connecting conductor GC22C that is electrically connected to the antenna substrate-side second ground conductor GC12 is composed of a plurality of connecting conductors that are distributed. In the example shown in Figures 9(B) and 9(C), a total of eight second ground connecting conductors GC22C are formed distributed in the X and Y directions. The other configurations of the mounting substrate 207 are the same as those of the mounting substrate 206 shown in Figure 8.

[0084] According to the seventh embodiment, multiple second ground connecting conductors GC22C are arranged at a narrow pitch, which reduces the resistance of the current path of the shorting element. This reduces transmission loss and improves antenna characteristics. Because the current density of the second ground connecting conductor GC22C, which is part of the shorting element for the inverted-F antenna, is higher than the current density of the first ground connecting conductor GC21C, it is preferable that the arrangement pitch of the second ground connecting conductors GC22C be narrower than the arrangement pitch of the first ground connecting conductors GC21C. This allows more second ground connecting conductors GC22C to be provided.

[0085] Eighth Embodiment In the eighth embodiment, an arrayed antenna will be exemplified.

[0086] 10 is a plan view of an antenna 308 according to the eighth embodiment. The antenna substrate 101 has a plurality of radiation conductors RE arranged along the X direction. The configuration of each antenna substrate 101 is the same as that shown in the first embodiment.

[0087] A signal line conductor, one end of which is electrically connected to the signal terminal electrode SE, is formed within the mounting substrate 208. A conductor pattern is formed on the mounting substrate 208 so that power is fed from this signal line conductor to the feeding point FP of each antenna substrate 101.

[0088] The arrangement pitch of each radiation conductor RE is λ / 2 or close to λ / 2, where λ represents the wavelength at the resonant frequency of each antenna.

[0089] By arranging the radiation conductors RE of each antenna at such a pitch, grating lobes can be suppressed, and by controlling the phase with a phase shifter, the beam scanning angle can be expanded to 90 degrees.

[0090] Ninth Embodiment In the ninth embodiment, an electronic device will be exemplified.

[0091] Fig. 11 is a cross-sectional view of an electronic device 509 according to the ninth embodiment. This electronic device 509 includes the antenna shown in each of the previous embodiments and another substrate on which the antenna is mounted. In Fig. 11, the electronic device 509 includes an antenna 301 and another substrate 401. The antenna 301 is the antenna shown in the first embodiment.

[0092] 11, the other substrate 401 includes parallel ground conductors GC41 and GC42 and a signal line conductor SL1 sandwiched between the ground conductors GC41 and GC42. A stripline is formed by the ground conductors GC41 and GC42, the signal line conductor SL1, and a resin layer between the ground conductors GC41 and GC42 and the signal line conductor SL1.

[0093] The mounting-substrate-side first ground conductor GC21 of the antenna 301 is connected to the ground conductor GC42 of the other substrate 401 via a conductive bonding material such as solder. Also, the signal terminal electrode SE of the antenna 301 is connected to the signal line conductor SL1 of the other substrate 401 via a conductive bonding material such as solder.

[0094] The other board 401 is configured with a circuit that uses the antenna 301. Alternatively, the other board 401 simply functions as a signal cable.

[0095] Various embodiments of the present invention have been presented so far, but these are all examples and are not intended to limit the scope of the present invention. Various omissions, substitutions, and modifications can be made to the embodiments of the present invention without departing from the spirit of the invention. Embodiments with such omissions, substitutions, and modifications are included within the scope and spirit of the present invention, and are also included in the scope of the invention and its equivalents as set forth in the claims of this application.

[0096] For example, in each embodiment, an example has been shown in which the mounting-board-side first ground conductor GC21 is also formed on an inner layer of the mounting board, but the mounting-board-side first ground conductor GC21 may be formed only on the top surface of the mounting board or in the vicinity thereof.

[0097] In each embodiment, the radiating conductor RE is formed on the upper surface of the antenna substrate, but this radiating conductor RE does not have to be exposed. That is, the radiating conductor RE may be located near the upper surface of the antenna substrate. Furthermore, the radiating conductor RE may be formed inside (inner layer of) the antenna substrate.

[0098] In each embodiment, the ground conductor layer GC2 is formed on the lower surface of the mounting substrate, but this ground conductor layer GC2 does not have to be exposed. In other words, the ground conductor layer GC2 may be located near the lower surface of the mounting substrate.

[0099] In addition, in each embodiment, an example has been shown in which both the antenna substrate and the mounting substrate are laminated substrates including layered insulators and conductors, but one or both may have a structure other than a laminated substrate.

[0100] In addition, although the above-described embodiments show examples in which the top and bottom surfaces of the antenna substrate and the mounting substrate are exposed, a protective film may be provided on the top and / or bottom surfaces of the antenna substrate. Similarly, a protective film may be provided on the top and / or bottom surfaces of the mounting substrate. This protective film may be, for example, a solder resist film or a similar material. The protective film may also be made of epoxy resin, liquid crystal polymer resin, or polyimide.

[0101] In addition, in each embodiment, a single feed point FP is provided for one radiation conductor RE, but the number of feed points for one radiation conductor RE is not limited to one.

[0102] Furthermore, in each embodiment, an antenna including a rectangular radiation conductor RE has been shown, but the radiation conductor may be linear, square, circular, or any of these modified shapes.

[0103] In addition, in each embodiment, a planar inverted-F antenna (PIFA) having a planar radiating conductor RE is shown, but the radiating conductor is not limited to being planar, and may be linear, strip-shaped, or a modified shape thereof.

[0104] In addition, in each embodiment, an example has been shown in which all the insulator layers are insulator layers on which conductor patterns are formed, but an antenna substrate or a mounting substrate may be constructed in which multiple insulator layers, including an insulator layer on which no conductor patterns are formed, are stacked.

[0105] In each embodiment, a stripline is formed by arranging the signal line conductor SL and the ground conductors (GC21, GC2) at positions sandwiching the signal line conductor SL in the thickness direction (vertical direction), but a coplanar line may be formed by arranging the signal line conductor and the ground conductor on the same layer. Also, a microstripline may be formed by providing a ground conductor on only one side of the signal line conductor SL.

[0106] Furthermore, in each embodiment, a resin layer is exemplified as an insulator layer, but each insulator layer may be, for example, a ceramic layer (a layer formed by firing a ceramic green sheet).

[0107] The antenna substrate, antenna, and electronic device of the present invention may be configured in the following manner.

[0108] <1> An antenna substrate including an insulator and a conductor each forming a layer, and to be mounted on a mounting board, wherein a radiation conductor made of the conductor is formed on the antenna substrate, a feeding electrode, a first ground conductor, and a second ground conductor each made of the conductor for mounting are formed on a bottom surface of the antenna substrate which is a mounting surface for the mounting board, a second ground connection conductor is formed inside the antenna substrate, the first end of which is connected to a ground point of the radiation conductor and the second end of which is connected to the second ground conductor, a feeding electrode connection conductor is formed inside the antenna substrate, the first end of which is connected to the radiation conductor and the second end of which is connected to the feeding electrode, the feeding electrode is an electrode conducting to the feeding point of the radiation conductor, and the second ground conductor is an electrode conducting to the ground portion of the radiation conductor, and there is no conduction between the first ground conductor and the second ground conductor.

[0109] <2> The antenna substrate according to <1>, wherein the radiation conductor has a portion folded back from an upper surface of the antenna substrate or a portion near the upper surface to the lower surface.

[0110] <3> An antenna comprising: the antenna substrate according to <1> or <2>; and a mounting substrate on which the antenna substrate is mounted, wherein the mounting substrate includes an insulator and a conductor, each of which forms a layer; a mounting-board-side first ground conductor made of the conductor of the mounting substrate and conducting to the first ground conductor, formed on an upper surface of the mounting substrate; a mounting-board-side second ground conductor made of the conductor of the mounting substrate and conducting to the second ground conductor, formed on the upper surface of the mounting substrate; a mounting-board-side feeding electrode made of the conductor of the mounting substrate and conducting to the feeding electrode, formed on the upper surface of the mounting substrate; a ground conductor layer made of the conductor of the mounting substrate, formed on the mounting substrate; and a ground connection conductor, which provides electrical continuity between the mounting-board-side first ground conductor and the ground conductor layer, formed on the mounting substrate.

[0111] <4> The antenna according to <3>, wherein the thickness of the mounting substrate is thinner than the thickness of the antenna substrate.

[0112] <5> The antenna according to <3> or <4>, wherein the mounting substrate has a bent portion.

[0113] <6> The antenna according to any one of <3> to <5>, wherein, when viewed in a stacking direction of the mounting board and the antenna board, the mounting board-side first ground conductor includes an outer periphery of the radiation conductor of the antenna board and overlaps with substantially the entire radiation conductor of the antenna board.

[0114] <7> The antenna according to any one of <3> to <6>, wherein the mounting substrate includes a base substrate and an interposer substrate mounted on the base substrate, and the antenna substrate is mounted on the interposer substrate.

[0115] <8> The antenna according to any one of <3> to <7>, wherein the mounting-board-side second ground conductor includes a wiring conductor extending in a layer direction of the insulator of the mounting board between the mounting-board-side second ground mounting electrode to which the second ground conductor of the antenna board is connected and the ground conductor layer.

[0116] <9> The antenna according to any one of <3> to <8>, wherein the second ground connection conductor is composed of a plurality of connection conductors arranged in a dispersed manner.

[0117] <10> The antenna according to any one of <3> to <9>, wherein the second ground connection conductor that is electrically connected to the second ground conductor is configured as a connection conductor that is thinner than the second ground connection conductor of the antenna substrate.

[0118] <11> An electronic device comprising the antenna according to any one of <3> to <10> and another substrate on which the antenna is mounted.

[0119] BD...bending portion BM...conductive bonding material FP...feed point FP1...antenna substrate side feed electrode FP2...mounting substrate side feed electrode FPC...feed electrode connecting conductor GC11...antenna substrate side first ground conductor (first ground conductor) GC12...antenna substrate side second ground conductor (second ground conductor) GC12C...antenna substrate side second ground connecting conductor (second ground connecting conductor) GC2...ground conductor layer GC21...mounting substrate side first ground conductor GC22, GC22A...mounting substrate side second ground conductor GC21C...first ground connecting conductor GC22C, GC22B...second ground connecting conductor GC41, GC42...ground conductor GP...ground portion RE, RE1, RE21, RE22...radiating conductor SE...signal terminal electrode SL, SL1...signal line conductor 4...conductor foil 5...Interlayer connection conductor 10...Antenna substrate resin layer 20...Mounting substrate resin layer 101, 102, 106, 107...Antenna substrate 201, 203...Mounting substrate 203A...Interposer substrate 203B...Base substrate 204, 205A, 205B, 206, 207, 208...Mounting substrate 301, 302, 303, 304, 305A, 305B, 306, 307...Antenna 308...Antenna 401...Another substrate 509...Electronic device

Claims

1. An antenna substrate comprising an insulator and a conductor each forming a layer, and to be mounted on a mounting board, wherein a radiation conductor made of the conductor is formed on the antenna substrate, a feeding electrode, a first ground conductor, and a second ground conductor each made of the conductor for mounting are formed on the underside of the antenna substrate, which is the mounting surface for the mounting board, a second ground connection conductor is formed inside the antenna substrate, the first end of which is connected to the ground point of the radiation conductor and the second end of which is connected to the second ground conductor, a feeding electrode connection conductor is formed inside the antenna substrate, the first end of which is connected to the radiation conductor and the second end of which is connected to the feeding electrode, the feeding electrode is an electrode conducting to the feeding point of the radiation conductor, and the second ground conductor is an electrode conducting to the ground part of the radiation conductor, and there is no conduction between the first and second ground conductors.

2. The antenna substrate according to claim 1, wherein the radiation conductor has a portion folded back from the upper surface of the antenna substrate or in the vicinity of the upper surface to the lower surface.

3. An antenna comprising: the antenna substrate according to claim 1 or 2; and a mounting substrate on which the antenna substrate is mounted, wherein the mounting substrate includes an insulator and a conductor, each of which forms a layer; a mounting substrate-side first ground conductor made of the conductor of the mounting substrate and conducting to the first ground conductor, formed on the upper surface of the mounting substrate; a mounting substrate-side second ground conductor made of the conductor of the mounting substrate and conducting to the second ground conductor, formed on the upper surface of the mounting substrate; a mounting substrate-side feeding electrode made of the conductor of the mounting substrate and conducting to the feeding electrode, formed on the upper surface of the mounting substrate; a ground conductor layer made of the conductor of the mounting substrate, formed on the mounting substrate; and a ground connection conductor formed on the mounting substrate, which provides electrical continuity between the mounting substrate-side first ground conductor and the ground conductor layer.

4. The antenna according to claim 3, wherein the thickness of the mounting substrate is thinner than the thickness of the antenna substrate.

5. The antenna according to claim 3 or 4, wherein the mounting substrate has a bent portion.

6. The antenna according to any one of claims 3 to 5, wherein, when viewed in the stacking direction of the mounting board and the antenna board, the mounting board-side first ground conductor includes an outer periphery of the radiation conductor of the antenna board and overlaps with substantially the entire radiation conductor of the antenna board.

7. An antenna according to any one of claims 3 to 6, wherein the mounting substrate comprises a base substrate and an interposer substrate mounted on the base substrate, and the antenna substrate is mounted on the interposer substrate.

8. An antenna according to any one of claims 3 to 7, wherein the mounting board side second ground conductor comprises a wiring conductor extending in the layer direction of the insulator of the mounting board between the mounting board side second ground mounting electrode to which the second ground conductor of the antenna board is connected and the ground conductor layer.

9. The antenna according to any one of claims 3 to 8, wherein the second ground connection conductor is composed of a plurality of connection conductors arranged in a dispersed manner.

10. The antenna according to any one of claims 3 to 9, wherein the second ground connection conductor that is electrically connected to the second ground conductor is made of a connection conductor that is thinner than the second ground connection conductor of the antenna substrate.

11. An electronic device comprising the antenna according to any one of claims 3 to 10 and another substrate on which the antenna is mounted.

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