Multilayered substrate

Abstract

As viewed in a Z-axis negative direction, a ground conductor layer non-formation region in which one or more first ground conductor layers are not provided is present in a radiation conductor layer region in which a radiation conductor layer is provided. As viewed in the Z-axis negative direction, a signal conductor layer has an overlap section overlapping with the ground conductor layer non-formation region. Aside from the radiation conductor layer, no conductor that covers the entire ground conductor layer non-formation region is present on the Z-axis positive side of the signal conductor layer in the ground conductor layer non-formation region. A first branch conductor layer and a second branch conductor layer are provided to a layered body, and are electrically connected to the signal conductor layer. As viewed in the Z-axis negative direction, there is an imaginary line that passes through the overlap section, and with regard to which the first branch conductor layer and the second branch conductor layer demonstrate line symmetry.

Description

multilayer board

[0001] The present invention relates to a multilayer substrate.

[0002] A microstrip antenna described in Patent Document 1 is known as an invention relating to a conventional multilayer substrate. The microstrip antenna includes a ground conductor, a center conductor, and a radiation conductor. The center conductor is located below the ground conductor. The radiation conductor is located above the ground conductor. A slot is formed in the ground conductor. When viewed from below, the slot overlaps with the radiation conductor and the center conductor. This allows the radiation conductor to be electromagnetically coupled to the ground conductor.

[0003] Japanese Patent Application Laid-Open No. 2000-261235

[0004] However, in the microstrip antenna described in Patent Document 1, there is a demand for easily adjusting the input impedance of the antenna. To achieve this, it is considered to add a matching circuit to the microstrip antenna. However, when a matching circuit is added to the microstrip antenna, it may become difficult to maintain the symmetry of the radiation characteristics and reception characteristics of the microstrip antenna.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a multilayer substrate that can easily adjust the input impedance to a radiating conductor layer and can suppress deterioration in the symmetry of the radiation characteristics and reception characteristics of the radiating conductor layer.

[0006] a signal conductor layer provided on the laminate; a first branched conductor layer and a second branched conductor layer; the laminate has a structure in which a plurality of insulating layers are stacked along a Z-axis; the radiation conductor layer is provided on the laminate; the one or more first ground conductor layers are provided on the laminate, and overlap with the radiation conductor layer when viewed in the negative direction of the Z-axis, and are located on the negative side of the Z-axis relative to the radiation conductor layer; the signal conductor layer is provided on the laminate, and overlaps with the radiation conductor layer and the one or more first ground conductor layers when viewed in the negative direction of the Z-axis, and is located on the negative side of the Z-axis relative to the radiation conductor layer and the one or more first ground conductor layers, and is not electrically connected to the radiation conductor layer; and a ground conductor layer non-forming region in which the one or more first ground conductor layers are not provided exists in a radiation conductor layer region in which the radiation conductor layer is provided, when viewed in the negative direction of the Z-axis; When viewed in the negative direction of the Z axis, the signal conductor layer has an overlapping portion that overlaps with the ground conductor layer non-formed region, and in the ground conductor layer non-formed region, there is no conductor other than the radiation conductor layer that covers the entire ground conductor layer non-formed region on the positive side of the Z axis from the signal conductor layer, and the first branch conductor layer and the second branch conductor layer are provided in the laminate and are electrically connected to the signal conductor layer, and when viewed in the negative direction of the Z axis, there is an imaginary line that passes through the overlapping portion and is line-symmetrical between the first branch conductor layer and the second branch conductor layer.

[0007] The multilayer substrate according to the present invention makes it possible to easily adjust the input impedance to the radiating conductor layer in the band of high-frequency signals transmitted and received by the radiating conductor layer, and also to suppress deterioration in the symmetry of the radiation characteristics and reception characteristics of the radiating conductor layer.

[0008] Fig. 1 is an exploded perspective view of multilayer substrate 10. Fig. 2 is a top view of multilayer substrate 10. Fig. 3 is a cross-sectional view of multilayer substrate 10. Fig. 4 is an exploded perspective view of multilayer substrate 10a. Fig. 5 is an exploded perspective view of multilayer substrate 10b. Fig. 6 is a cross-sectional view of multilayer substrate 10c. Fig. 7 is an exploded perspective view of multilayer substrate 10d.

[0009] (Embodiment) [Structure of Multilayer Substrate] The structure of a multilayer substrate 10 according to an embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is an exploded perspective view of the multilayer substrate 10. Fig. 2 is a top view of the multilayer substrate 10. Fig. 3 is a cross-sectional view of the multilayer substrate 10. Fig. 3 is a cross-sectional view taken along line A-A in Fig. 2.

[0010] In this specification, directions are defined as follows: The direction in which the insulator layers 16a to 16f are arranged in this order is defined as the downward direction. The downward direction coincides with the negative direction of the Z axis. When viewed from below, two sides of the laminate 15 extend along the front-rear axis. The front-rear axis coincides with the Y axis. The remaining two sides of the laminate 15 extend along the left-right axis. The left-right axis coincides with the X axis. The up-down axis (Z axis), front-rear axis (Y axis), and left-right axis (X axis) are perpendicular to one another. Note that the up-down axis, front-rear axis, and left-right axis in this embodiment do not necessarily coincide with the up-down axis, front-rear axis, and left-right axis when the multilayer substrate 10 is in use.

[0011] First, the structure of a multilayer substrate 10 will be described with reference to Figures 1 to 3. The multilayer substrate 10 is an antenna module built into an electronic device such as a wireless communication terminal. As shown in Figure 1, the multilayer substrate 10 includes a laminate 15, a radiation conductor layer 17, a signal conductor layer 18, a first ground conductor layer 20, a second ground conductor layer 22, an external electrode 28, an annular ground conductor layer 30, and interlayer connection conductors v1 to v3.

[0012] The laminate 15 has a plate shape. When viewed from below, the laminate 15 has a rectangular shape. The laminate 15 has a structure in which the insulator layers 16a to 16f are stacked along the vertical axis (Z axis). The insulator layers 16a to 16f are arranged in this order from below. The insulator layers 16a to 16f are fused together with adjacent layers. The material of the insulator layers 16a to 16f is a thermoplastic resin. The thermoplastic resin is, for example, a liquid crystal polymer.

[0013] The radiating conductor layer 17 is provided on the laminate 15. In this embodiment, the radiating conductor layer 17 is located on the upper main surface of the laminate 15. Therefore, the radiating conductor layer 17 is located on the upper main surface of the insulator layer 16a. The radiating conductor layer 17 has a rectangular shape when viewed from below. The radiating conductor layer 17 may also have a square shape when viewed from below. When viewed from below, two sides of the radiating conductor layer 17 extend along the front-to-back axis. The remaining two sides of the radiating conductor layer 17 extend along the left-to-right axis.

[0014] The first ground conductor layer 20 is provided on the laminate 15. In this embodiment, the first ground conductor layer 20 is located on the upper main surface of the insulator layer 16d. As a result, the first ground conductor layer 20 is located below (on the negative side of the Z axis) the radiation conductor layer 17. The first ground conductor layer 20 covers most of the upper main surface of the insulator layer 16d. As a result, the first ground conductor layer 20 overlaps with the radiation conductor layer 17 when viewed from below. The first ground conductor layer 20 as described above is connected to the ground potential.

[0015] The signal conductor layer 18 is provided on the laminate 15. In this embodiment, the signal conductor layer 18 is located on the upper main surface of the insulator layer 16e. Therefore, the signal conductor layer 18 is located below (on the negative side of the Z axis) the radiating conductor layer 17 and the first ground conductor layer 20. Furthermore, when viewed from the downward direction (the negative direction of the Z axis), the signal conductor layer 18 overlaps with the radiating conductor layer 17 and the first ground conductor layer 20. However, the signal conductor layer 18 is not electrically connected to the radiating conductor layer 17 and the first ground conductor layer 20. The signal conductor layer 18 has a linear shape extending along the left-right axis (X axis). As a result, the signal conductor layer 18 has a left end (first end) and a right end. A high-frequency signal is transmitted through the signal conductor layer 18 as described above.

[0016] The second ground conductor layer 22 is provided on the laminate 15. In this embodiment, the second ground conductor layer 22 is located on the lower main surface of the insulator layer 16f. As a result, the second ground conductor layer 22 is located below the signal conductor layer 18 (on the negative side of the Z axis). The second ground conductor layer 22 covers most of the lower main surface of the insulator layer 16f. As a result, the second ground conductor layer 22 overlaps with the radiation conductor layer 17 and the signal conductor layer 18 when viewed from below. The second ground conductor layer 22 as described above is connected to the ground potential.

[0017] The signal conductor layer 18, the first ground conductor layer 20, and the second ground conductor layer 22 as described above have a stripline structure.

[0018] The external electrode 28 is provided on the laminate 15. In this embodiment, the external electrode 28 is located on the lower main surface of the insulator layer 16f. However, the external electrode 28 is not in contact with the second ground conductor layer 22. The external electrode 28 has a rectangular shape when viewed from below. When viewed from below, the external electrode 28 overlaps with the right end of the signal conductor layer 18. The external electrode 28 is connected to an electrode on the circuit board by soldering.

[0019] The annular ground conductor layer 30 is provided on the laminate 15. In this embodiment, the annular ground conductor layer 30 is located on the upper main surface of the insulator layer 16e. The annular ground conductor layer 30 has a rectangular ring shape when viewed from below. The signal conductor layer 18 is located within a region surrounded by the annular ground conductor layer 30 when viewed from below. The annular ground conductor layer 30 is connected to a ground potential.

[0020] The interlayer connection conductor v1 electrically connects the signal conductor layer 18 and the external electrode 28. The interlayer connection conductor v1 penetrates the insulator layers 16e and 16f along the up-down axis. The upper end of the interlayer connection conductor v1 contacts the right end of the signal conductor layer 18. The lower end of the interlayer connection conductor v1 contacts the external electrode 28.

[0021] The interlayer connection conductors v2 and v3 electrically connect the first ground conductor layer 20, the second ground conductor layer 22, and the annular ground conductor layer 30. The interlayer connection conductors v2 and v3 penetrate the insulator layers 16d to 16f along the up-down axis. The upper ends of the interlayer connection conductors v2 and v3 contact the first ground conductor layer 20. The lower ends of the interlayer connection conductors v2 and v3 contact the second ground conductor layer 22. The middle portions of the interlayer connection conductors v2 and v3 contact the annular ground conductor layer 30.

[0022] As shown in FIG. 2 , the area where the radiation conductor layer 17 is provided is defined as the radiation conductor layer area A1 when viewed downward (negative direction of the Z axis). When viewed downward (negative direction of the Z axis), the radiation conductor layer area A1 includes a ground conductor layer-free area A0 where the first ground conductor layer 20 is not provided. When viewed downward (negative direction of the Z axis), the ground conductor layer-free area A0 is surrounded by the first ground conductor layer 20. Specifically, when viewed downward (negative direction of the Z axis), the ground conductor layer-free area A0 has a rectangular shape. Two long sides of the ground conductor layer-free area A0 extend in the front-rear direction. Two short sides of the ground conductor layer-free area A0 extend in the left-right direction. The length of the ground conductor layer-free area A0 along the front-rear axis (Y axis) is equal to or less than one-quarter of the wavelength of the high-frequency signal transmitted through the signal conductor layer 18. This prevents unwanted resonance and reduces noise in the ground conductor layer-free area A0.

[0023] The ground conductor layer-free area A0 intersects with the signal conductor layer 18 when viewed downward. In this embodiment, the ground conductor layer-free area A0 is perpendicular to the signal conductor layer 18 when viewed downward. As a result, the signal conductor layer 18 overlaps with the ground conductor layer-free area A0 when viewed downward (negative direction of the Z axis). That is, when viewed downward (negative direction of the Z axis), the signal conductor layer 18 has an overlapping portion P that overlaps with the ground conductor layer-free area A0. When viewed downward (negative direction of the Z axis), the length L1 of the signal conductor layer 18 between the left end (first end) of the signal conductor layer 18 and the overlapping portion P is equal to or less than ¼ of the wavelength of the high-frequency signal transmitted through the signal conductor layer 18. This prevents unwanted resonance from occurring in the signal conductor layer 18 between the left end of the signal conductor layer 18 and the overlapping portion P, thereby suppressing noise generation.

[0024] When viewed downward (negative direction of the Z axis), the signal conductor layer 18 overlaps with the radiating conductor layer 17 in the ground conductor layer-free area A0. That is, when viewed downward, the overlapping portion P overlaps with the radiating conductor layer 17. As shown in FIG. 3 , in the ground conductor layer-free area A0, the radiating conductor layer 17 is the only conductor that covers the entire ground conductor layer-free area A0 above the signal conductor layer 18 (positive side of the Z axis). This results in electromagnetic field coupling between the signal conductor layer 18 and the radiating conductor layer 17. In this embodiment, the signal conductor layer 18 and the radiating conductor layer 17 are primarily magnetically coupled. As a result, a high-frequency signal transmitted through the signal conductor layer 18 is transmitted to the radiating conductor layer 17 by an electromagnetic field via the ground conductor layer-free area A0. A standing wave of the high-frequency signal is then generated in the radiating conductor layer 17. The radiating conductor layer 17 radiates the electromagnetic wave of the high-frequency signal upward. Using a similar principle, the radiating conductor layer 17 receives the electromagnetic wave of the high-frequency signal.

[0025] The multilayer substrate 10 further includes a first branched conductor layer 24 and a second branched conductor layer 26. The first branched conductor layer 24 and the second branched conductor layer 26 are provided in the laminate 15. In this embodiment, the first branched conductor layer 24 and the second branched conductor layer 26 are located on the upper main surface of the insulator layer 16e. The first branched conductor layer 24 and the second branched conductor layer 26 have an L-shape when viewed from below. More specifically, the first branched conductor layer 24 includes a first portion 24a and a second portion 24b. The first portion 24a extends in the front-rear direction. The rear end of the first portion 24a is connected to the connection point P0 of the signal conductor layer 18. The connection point P0 is located between the left and right ends of the signal conductor layer 18. In this embodiment, the length L2 of the transmission path of the high-frequency signal from the overlapping portion P to the connection point P0 is shorter than half the wavelength of the high-frequency signal. That is, the length L2 of the transmission path of the high-frequency signal from the overlapping portion P to the first branched conductor layer 24 is shorter than half the wavelength of the high-frequency signal. The second portion 24b extends in the left-right direction. The right end of the second portion 24b is connected to the front end of the first portion 24a. As a result, the first branched conductor layer 24 is electrically connected to the signal conductor layer 18. The length of the first branched conductor layer 24 is equal to or less than half the wavelength of the high-frequency signal transmitted through the signal conductor layer 18. The first branched conductor layer 24 as described above functions as an open stub.

[0026] The second branched conductor layer 26 includes a first portion 26a and a second portion 26b. The first portion 26a extends in the front-rear direction. The front end of the first portion 26a is connected to the connection point P0 of the signal conductor layer 18. In this embodiment, the length L2 of the transmission path of the high-frequency signal from the overlapping portion P to the connection point P0 is shorter than half the wavelength of the high-frequency signal. That is, the length L2 of the transmission path of the high-frequency signal from the overlapping portion P to the second branched conductor layer 26 is shorter than half the wavelength of the high-frequency signal. The second portion 26b extends in the left-right direction. The right end of the second portion 26b is connected to the rear end of the first portion 26a. As a result, the second branched conductor layer 26 is electrically connected to the signal conductor layer 18. The length of the second branched conductor layer 26 is equal to or shorter than half the wavelength of the high-frequency signal transmitted through the signal conductor layer 18. The second branched conductor layer 26 as described above functions as an open stub.

[0027] Here, the length of the first portion 24a is equal to the length of the first portion 26a. The length of the second portion 24b is equal to the length of the second portion 26b. As a result, when viewed in the downward direction (negative direction of the Z axis), there is an imaginary line L that passes through the overlapping portion P and on which the first branched conductor layer 24 and the second branched conductor layer 26 are line-symmetric. In this embodiment, the imaginary line L extends along the left-right axis. Therefore, when viewed in the downward direction, the signal conductor layer 18 overlaps with the imaginary line L over its entire length. When viewed in the downward direction, the signal conductor layer 18 has a shape that is line-symmetric with respect to the imaginary line L.

[0028] Furthermore, when viewed downward (in the negative direction of the Z axis), the radiation conductor layer 17 has a shape that is line-symmetric with respect to the imaginary line L. Furthermore, when viewed downward (in the negative direction of the Z axis), the ground conductor layer-free area A0 extends along the front-rear axis. As a result, when viewed downward (in the negative direction of the Z axis), the ground conductor layer-free area A0 extends along an axis that is perpendicular to the imaginary line L. The ground conductor layer-free area A0 has a structure that is line-symmetric with respect to the imaginary line L.

[0029] The radiation conductor layer 17, the signal conductor layer 18, the first ground conductor layer 20, the second ground conductor layer 22, the first branch conductor layer 24, the second branch conductor layer 26, the external electrode 28, and the annular ground conductor layer 30 are formed by patterning metal foil attached to the upper or lower principal surfaces of the insulator layers 16 a, 16 d to 16 f. The metal foil is, for example, copper foil.

[0030] The interlayer connection conductors v1 to v3 are formed by filling conductive paste into through holes that penetrate the insulating layers 16d to 16f along the vertical axis, and solidifying the conductive paste by heat treatment and pressure treatment.

[0031] [Effect] According to the multilayer substrate 10, the input impedance to the radiating conductor layer 17 can be easily adjusted. More specifically, in the multilayer substrate 10, the first branched conductor layer 24 and the second branched conductor layer 26 are electrically connected to the signal conductor layer 18. This allows the first branched conductor layer 24 and the second branched conductor layer 26 to function as a matching circuit by adjusting the shapes of the first branched conductor layer 24 and the second branched conductor layer 26. As a result, the input impedance to the radiating conductor layer 17 can be easily adjusted.

[0032] The multilayer substrate 10 can suppress a decrease in the symmetry of the radiation characteristics of the radiating conductor layer 17. More specifically, when the first branched conductor layer 24 and the second branched conductor layer 26 are provided on the multilayer substrate 10, the radiation characteristics of the radiating conductor layer 17 are affected by the first branched conductor layer 24 and the second branched conductor layer 26. Therefore, when viewed downward, there is an imaginary line L that passes through the overlapping portion P and on which the first branched conductor layer 24 and the second branched conductor layer 26 are line-symmetric. That is, the first branched conductor layer 24 and the second branched conductor layer 26 are line-symmetric. As a result, the influence of the first branched conductor layer 24 on the front half of the radiation pattern of the radiating conductor layer 17 and the influence of the second branched conductor layer 26 on the rear half of the radiation pattern of the radiating conductor layer 17 are closer to each other. As a result, the multilayer substrate 10 can suppress a decrease in the symmetry of the radiation characteristics of the radiating conductor layer 17. For the same reason, the multilayer substrate 10 can prevent the symmetry of the reception characteristics of the radiation conductor layer 17 from being reduced.

[0033] (First Modification) A multilayer substrate 10a according to a first modification will be described below with reference to the drawings. Fig. 4 is an exploded perspective view of the multilayer substrate 10a.

[0034] The multilayer substrate 10a differs from the multilayer substrate 10 in that the signal conductor layer 18, the first branched conductor layer 24, and the second branched conductor layer 26 are located on different insulator layers. More specifically, the signal conductor layer 18 is located on the upper main surface of the insulator layer 16e. The first branched conductor layer 24 and the second branched conductor layer 26 are located on the upper main surface of the insulator layer 16g. The insulator layer 16g is located between the insulator layers 16e and 16f. As a result, the first branched conductor layer 24 and the second branched conductor layer 26 are located below the signal conductor layer 18 (on the negative side of the Z axis).

[0035] The interlayer connection conductor v1 electrically connects the signal conductor layer 18, the first branch conductor layer 24, the second branch conductor layer 26, and the external electrode 28. The interlayer connection conductor v1 penetrates the insulator layers 16e, 16g, and 16f along the up-down axis. The upper end of the interlayer connection conductor v1 contacts the right end of the signal conductor layer 18. The lower end of the interlayer connection conductor v1 contacts the external electrode 28. The middle portion of the interlayer connection conductor v1 contacts the first branch conductor layer 24 and the second branch conductor layer 26. The rest of the structure of the multilayer substrate 10a is the same as that of the multilayer substrate 10, so a description thereof will be omitted. The multilayer substrate 10a can achieve the same effects as the multilayer substrate 10.

[0036] In the multilayer substrate 10a, the first branched conductor layer 24 and the second branched conductor layer 26 are located below (on the negative side of the Z axis) the signal conductor layer 18. This positions the first branched conductor layer 24 and the second branched conductor layer 26 away from the radiating conductor layer 17. As a result, the radiation characteristics of the radiating conductor layer 17 are less likely to be affected by the first branched conductor layer 24 and the second branched conductor layer 26.

[0037] Second Modification A multilayer substrate 10b according to a second modification will now be described with reference to the drawings. Fig. 5 is an exploded perspective view of the multilayer substrate 10b.

[0038] The multilayer substrate 10b differs from the multilayer substrate 10 in that it further includes annular ground conductor layers 32, 34, and 36. The annular ground conductor layers 32, 34, and 36 are provided on the laminate 15. In this embodiment, the annular ground conductor layer 32 is located on the upper main surface of the insulator layer 16a. The annular ground conductor layer 34 is located on the upper main surface of the insulator layer 16b. The annular ground conductor layer 36 is located on the upper main surface of the insulator layer 16c. The annular ground conductor layers 32, 34, and 36 have a rectangular ring shape when viewed from below. The radiation conductor layer 17, the signal conductor layer 18, the first branch conductor layer 24, and the second branch conductor layer 26 are located within an area surrounded by the annular ground conductor layers 32, 34, and 36 when viewed from below.

[0039] The interlayer connection conductors v2 and v3 electrically connect the first ground conductor layer 20, the second ground conductor layer 22, and the annular ground conductor layers 30, 32, 34, and 36. This connects the annular ground conductor layers 32, 34, and 36 to the ground potential. The other structure of the multilayer substrate 10b is the same as that of the multilayer substrate 10, and therefore a description thereof will be omitted. The multilayer substrate 10b can achieve the same effects as the multilayer substrate 10.

[0040] In the multilayer substrate 10b, the radiating conductor layer 17, the signal conductor layer 18, the first branch conductor layer 24, and the second branch conductor layer 26 are located within an area surrounded by the annular ground conductor layers 32, 34, and 36 when viewed from below. This prevents noise from entering the multilayer substrate 10b and also prevents noise from radiating forward, backward, leftward, and rightward from the multilayer substrate 10b. Furthermore, the radiating conductor layer 17, the signal conductor layer 18, the first branch conductor layer 24, and the second branch conductor layer 26 are prevented from forming capacitance with the surrounding conductors of the multilayer substrate 10b. Furthermore, the electromagnetic field radiating from the ground conductor layer-free area A0 is prevented from spreading in the left-right direction, allowing power to be efficiently input to the radiating conductor layer 17.

[0041] (Third Modification) A multilayer substrate 10c according to a third modification will now be described with reference to the drawings. Fig. 6 is a cross-sectional view of the multilayer substrate 10c.

[0042] The multilayer substrate 10c differs from the multilayer substrate 10 in that the laminate 15 is curved. More specifically, the laminate 15 has, when viewed downward (in the negative direction of the Z axis), a first section A11 in which the radiating conductor layer 17 is provided, and second sections A12a and A12b in which the radiating conductor layer 17 is not provided, when viewed downward (in the negative direction of the Z axis). The vertical thickness of a portion of the second section A12b is smaller than the vertical thickness of the first section A11. The second section A12b of the laminate 15 has a curved portion when viewed forward (in a direction perpendicular to the Z axis). The rest of the structure of the multilayer substrate 10c is the same as that of the multilayer substrate 10, so a description thereof will be omitted. The multilayer substrate 10c can achieve the same effects as the multilayer substrate 10.

[0043] Furthermore, in the multilayer substrate 10c, the vertical thickness of a portion of the second section A12b is smaller than the vertical thickness of the first section A11. This makes it easier to bend the second section A12b of the laminate 15 when viewed forward (in a direction perpendicular to the Z axis). Furthermore, the first section A11 and the second section A12b include insulator layers 16d to 16f. This prevents a connection of the signal conductor layer 18 between the first section A11 and the second section A12b. As a result, loss in the signal conductor layer 18 is suppressed.

[0044] (Fourth Modification) A multilayer substrate 10d according to a fourth modification will now be described with reference to the drawings. Fig. 7 is an exploded perspective view of the multilayer substrate 10d.

[0045] The multilayer substrate 10d differs from the multilayer substrate 10 in that the materials of the insulator layers 16a-16c are different from the materials of the insulator layers 16d-16f. The dielectric constants of the insulator layers 16a-16c are higher than the dielectric constants of the insulator layers 16d-16f. The rest of the structure of the multilayer substrate 10d is the same as that of the multilayer substrate 10, so a description thereof will be omitted. The multilayer substrate 10d can achieve the same effects as the multilayer substrate 10.

[0046] In the multilayer substrate 10d, the dielectric constant of the insulator layers 16a to 16c is higher than that of the insulator layers 16d to 16f, which causes a wavelength shortening effect in the radiating conductor layer 17. As a result, the radiating conductor layer 17 can be made smaller.

[0047] Other Embodiments The multilayer substrate according to the present invention is not limited to the multilayer substrates 10, 10a to 10d, and can be modified within the scope of the invention. The structures of the multilayer substrates 10, 10a to 10d may be combined arbitrarily.

[0048] The number of first ground conductor layers is not limited to one. The number of first ground conductor layers may be one or more. When the number of first ground conductor layers is two, a ground conductor layer-free area A0 is formed between the two first ground conductor layers. In this case, the ground conductor layer-free area A0 is not surrounded by the first ground conductor layers. For example, when viewed from below, no first ground conductor layers are present in front of or behind the ground conductor layer-free area A0.

[0049] The dielectric constant of the insulator layers 16a to 16c may be equal to or less than the dielectric constant of the insulator layers 16d to 16f, which reduces the capacitance between the radiation conductor layer 17 and the first ground conductor layer 20. As a result, the gain of the multilayer board is improved.

[0050] The second ground conductor layer 22, the external electrode 28, and the annular ground conductor layers 30, 32, 34, and 36 are not essential components.

[0051] The dielectric constant of the insulator layers 16 a to 16 c may be lower than the dielectric constant of the insulator layers 16 d to 16 f. In this case, the distance between the radiation conductor layer 17 and the first ground conductor layer 20 is shortened, and the thickness of the multilayer substrate 10 in the vertical direction is reduced.

[0052] The first branched conductor layer 24 and the second branched conductor layer 26 may be located above the signal conductor layer 18 .

[0053] The first branched conductor layer 24 and the second branched conductor layer 26 may be located to the left of the ground conductor layer non-forming area A0. That is, the connection point P0 may be located between the left end of the signal conductor layer 18 and the overlapping portion P.

[0054] The first branch conductor layer 24 and the second branch conductor layer 26 may be short stubs instead of open stubs. In this case, the first branch conductor layer 24 and the second branch conductor layer 26 are connected to, for example, the annular ground conductor layer 32.

[0055] The length L2 of the transmission path of the high frequency signal from the overlapping portion P to the first branched conductor layer 24 and the second branched conductor layer 26 may be longer than half the wavelength of the high frequency signal.

[0056] It should be noted that the radiation conductor layer 17 does not have to have a shape that is line-symmetrical with respect to the imaginary line L when viewed from below.

[0057] It should be noted that the signal conductor layer 18 does not have to have a shape that is line-symmetrical with respect to the imaginary line L when viewed from below.

[0058] The ground conductor layer-free area A0 does not necessarily extend along an axis perpendicular to the imaginary line L when viewed from below.

[0059] In addition, the length L1 of the signal conductor layer 18 between the left end of the signal conductor layer 18 and the overlapping portion P when viewed downward may be longer than half the wavelength of the high-frequency signal transmitted through the signal conductor layer 18.

[0060] The length of the ground conductor layer-free area A0 along the front-rear axis may be longer than half the wavelength of the high-frequency signal transmitted through the signal conductor layer 18.

[0061] The multilayer substrate 10, 10a to 10d may further include one or more branch conductor layers. The one or more branch conductor layers do not have to have a shape that is line-symmetrical with respect to the imaginary line L when viewed downward. However, the length of the transmission path from the first branch conductor layer 24 to the overlapping portion P and the length of the transmission path from the second branch conductor layer 26 to the overlapping portion P are shorter than the length of the transmission path from one or more branch conductor layers to the overlapping portion P.

[0062] Each of the first branched conductor layer 24 and the second branched conductor layer 26 may have a straight line shape or a curved shape when viewed downward.

[0063] The multilayer substrate 10, 10a to 10d may further include a third branched conductor layer and a fourth branched conductor layer that are symmetrical with respect to the imaginary line L.

[0064] The first branched conductor layer 24 and the second branched conductor layer 26 do not have to overlap with the radiating conductor layer 17 when viewed from below. Therefore, the entire first branched conductor layer 24 and the entire second branched conductor layer 26 may overlap with the radiating conductor layer 17 when viewed from below, or a portion of the first branched conductor layer 24 and a portion of the second branched conductor layer 26 may overlap with the radiating conductor layer 17 when viewed from below.

[0065] The present invention has the following structure.

[0066] (1) A multilayer substrate includes a laminate, a radiation conductor layer, one or more first ground conductor layers, a signal conductor layer, a first branch conductor layer, and a second branch conductor layer, wherein the laminate has a structure in which a plurality of insulator layers are stacked along a Z axis, the radiation conductor layer is provided on the laminate, the one or more first ground conductor layers are provided on the laminate, and are overlapped with the radiation conductor layer when viewed in the negative direction of the Z axis, and are located on the negative side of the Z axis with respect to the radiation conductor layer, the signal conductor layer is provided on the laminate, and is overlapped with the radiation conductor layer and the one or more first ground conductor layers when viewed in the negative direction of the Z axis, and is located on the negative side of the Z axis with respect to the radiation conductor layer and the one or more first ground conductor layers, and is not electrically connected to the radiation conductor layer, and when viewed in the negative direction of the Z axis, a ground conductor layer non-forming region in which the one or more first ground conductor layers are not provided exists in a radiation conductor layer region in which the radiation conductor layer is provided, a multilayer board, wherein, when viewed in the negative direction of the Z axis, the signal conductor layer has an overlapping portion that overlaps with the ground conductor layer-free region; in the ground conductor layer-free region, on the positive side of the Z axis from the signal conductor layer, there is no conductor other than the radiation conductor layer that covers the entire ground conductor layer-free region; the first branch conductor layer and the second branch conductor layer are provided on the laminate and are electrically connected to the signal conductor layer; and when viewed in the negative direction of the Z axis, there is an imaginary line that passes through the overlapping portion and is line-symmetrical between the first branch conductor layer and the second branch conductor layer.

[0067] (2) The multilayer substrate according to (1), wherein the first branched conductor layer and the second branched conductor layer are located on the negative side of the Z axis relative to the signal conductor layer.

[0068] (3) The multilayer substrate according to (1) or (2), wherein the length of a transmission path of a high-frequency signal from the overlapping portion to the first branched conductor layer and the second branched conductor layer is shorter than half the wavelength of the high-frequency signal.

[0069] (4) The multilayer substrate according to any one of (1) to (3), wherein the radiation conductor layer has a shape that is line-symmetric with respect to the imaginary line when viewed in the negative direction of the Z axis.

[0070] (5) The multilayer substrate according to any one of (1) to (4), wherein the ground conductor layer-free area extends along an axis perpendicular to the imaginary line when viewed in the negative direction of the Z axis.

[0071] (6) The multilayer substrate according to any one of (1) to (5), wherein the signal conductor layer has a first end, and the length of the signal conductor layer between the first end and the overlapping portion, as viewed in the negative direction of the Z axis, is equal to or less than half the wavelength of a high-frequency signal transmitted through the signal conductor layer.

[0072] (7) The multilayer substrate according to any one of (1) to (6), further comprising a second ground conductor layer, the second ground conductor layer being provided on the laminate, overlapping the radiation conductor layer when viewed in the negative direction of the Z axis, and being located on the negative side of the Z axis with respect to the signal conductor layer.

[0073] (8) A multilayer substrate according to any one of (1) to (7), wherein the laminate has a first section in which the radiating conductor layer is provided when viewed in the negative direction of the Z axis, and a second section in which the radiating conductor layer is not provided when viewed in the negative direction of the Z axis, and the second section of the laminate has a curved portion when viewed in a direction perpendicular to the Z axis.

[0074] (9) The multilayer board according to any one of (1) to (8), wherein the signal conductor layer extends along an X-axis, a Y-axis is perpendicular to the X-axis and the Z-axis, and the length of the ground conductor layer-free region in the direction along the Y-axis is equal to or less than half the wavelength of a high-frequency signal transmitted through the signal conductor layer.

[0075] (10) The multilayer substrate according to any one of (1) to (9), wherein the signal conductor layer extends along an X-axis, a Y-axis is orthogonal to the X-axis and the Z-axis, and the ground conductor layer-free region is surrounded by the first ground conductor layer when viewed in the negative direction of the Z-axis.

[0076] 10, 10a to 10d: Multilayer substrate 15: Laminate 16a to 16g: Insulator layer 17: Radiating conductor layer 18: Signal conductor layer 20: First ground conductor layer 22: Second ground conductor layer 24: First branch conductor layer 24a, 26a: First portion 24b, 26b: Second portion 26: Second branch conductor layer 28: External electrodes 30, 32, 34, 36: Ring-shaped ground conductor layer A0: Ground conductor layer-free region A1: Radiating conductor layer region A11: First section A12a, A12b: Second section L: Virtual line P: Overlapping portion P0: Connection point v1 to v3: Interlayer connection conductors

Claims

1. The multilayer substrate includes a laminate, a radiation conductor layer, one or more first ground conductor layers, a signal conductor layer, a first branch conductor layer, and a second branch conductor layer, wherein the laminate has a structure in which a plurality of insulator layers are laminated along the Z-axis, the radiation conductor layer is provided on the laminate, the one or more first ground conductor layers are provided on the laminate, and when viewed in the negative direction of the Z-axis, overlap the radiation conductor layer and are located on the negative side of the Z-axis with respect to the radiation conductor layer, the signal conductor layer is provided on the laminate, and when viewed in the negative direction of the Z-axis, overlaps the radiation conductor layer and the one or more first ground conductor layers and is located on the negative side of the Z-axis with respect to the radiation conductor layer and the one or more first ground conductor layers, and is not electrically connected to the radiation conductor layer, when viewed in the negative direction of the Z-axis, in the radiation conductor layer region where the radiation conductor layer is provided, there is a ground conductor layer non-formation region where the one or more first ground conductor layers are not provided, when viewed in the negative direction of the Z-axis, the signal conductor layer has an overlapping portion that overlaps the ground conductor layer non-formation region, in the ground conductor layer non-formation region, on the positive side of the Z-axis with respect to the signal conductor layer, there is no conductor other than the radiation conductor layer that covers the entire ground conductor layer non-formation region, the first branch conductor layer and the second branch conductor layer are provided on the laminate and are electrically connected to the signal conductor layer, when viewed in the negative direction of the Z-axis, there is a virtual line passing through the overlapping portion and with respect to which the first branch conductor layer and the second branch conductor layer are line-symmetric, the signal conductor layer has a connection location where the first branch conductor layer and the second branch conductor layer are connected, when viewed in the negative direction of the Z-axis, the connection location does not overlap the ground conductor layer non-formation region, A multilayer substrate.

2. The first branch conductor layer and the second branch conductor layer are located on the negative side of the Z-axis with respect to the signal conductor layer, The multilayer substrate according to Claim 1.

3. The length of the transmission path of the high-frequency signal from the overlapping portion to the first branch conductor layer and the second branch conductor layer is shorter than half of the wavelength of the high-frequency signal, The multilayer substrate according to Claim 1 or Claim 2.

4. when viewed in the negative direction of the Z-axis, the radiation conductor layer has a shape that is line-symmetric with respect to the virtual line, The multilayer substrate according to claim 1 or claim 2.

5. When viewed in the negative direction of the Z-axis, the non-formation region of the ground conductor layer extends along an axis orthogonal to the virtual line. The multilayer substrate according to claim 1 or claim 2.

6. The signal conductor layer has a first end. When viewed in the negative direction of the Z-axis, the length of the signal conductor layer between the first end and the overlapping portion is equal to or less than half of the wavelength of the high-frequency signal transmitted through the signal conductor layer. The multilayer substrate according to claim 1 or claim 2.

7. The multilayer substrate further includes a second ground conductor layer. The second ground conductor layer is provided in the laminate, and when viewed in the negative direction of the Z-axis, it overlaps with the radiation conductor layer and is located on the negative side of the Z-axis with respect to the signal conductor layer. The multilayer substrate according to claim 1 or claim 2.

8. The laminate has a first section where the radiation conductor layer is provided when viewed in the negative direction of the Z-axis, and a second section where the radiation conductor layer is not provided when viewed in the negative direction of the Z-axis. The second section of the laminate has a bent portion when viewed in a direction orthogonal to the Z-axis. The multilayer substrate according to claim 1 or claim 2.

9. The signal conductor layer extends along the X-axis. The Y-axis is orthogonal to the X-axis and the Z-axis. The length of the non-formation region of the ground conductor layer along the Y-axis is equal to or less than half of the wavelength of the high-frequency signal transmitted through the signal conductor layer. The multilayer substrate according to claim 1 or claim 2.

10. The signal conductor layer extends along the X-axis. The Y-axis is orthogonal to the X-axis and the Z-axis. The non-formation region of the ground conductor layer is surrounded by the first ground conductor layer when viewed in the negative direction of the Z-axis. The multilayer substrate according to claim 1 or claim 2.