Filter device

Abstract

The present invention relates to a filter device. Compared with an existing filter device having the same coupling amount, the filter device can be miniaturized. The filter device (1) comprises a substrate (11), a plurality of strip conductors (12a1 to 12a5) and a ground conductor layer (13), wherein a first recess (recesses 11a1 and 11a2) whose surface is covered by the ground conductor layer (13) is formed in an area opposite to each area between the strip conductors (between 12a1 and 12a2 and between 12a2 and 12a3).

Description

Technical Field

[0001] The present invention relates to filter devices. Background Art

[0002] In Patent Document 1 Figure 3 as well as Figure 4 As a conventional example, a microstrip filter device (a resonant circuit device in Patent Document 1) is illustrated, which includes: a dielectric substrate (a dielectric substrate 1 in Patent Document 1); a plurality of strip conductors (resonant conductors 3 to 7 in Patent Document 1) provided on a first main surface of the substrate and in which adjacent strip conductors are electromagnetically coupled to each other; and a ground conductor layer (a ground conductor 2 in Patent Document 1) provided on a second main surface of the substrate. In addition, each of the plurality of strip conductors functions as a resonator.

[0003] Patent Document 1: Japanese Patent Publication No. 9-139605

[0004] Furthermore, in Patent Document 1 Figure 1 FIG. 1 shows a substrate that is not aligned with the plurality of strip conductors (in the patent document 1) when viewed from above. Figure 1 In the embodiment, each overlapping region of the resonant conductors 5 and 6 is provided with a recess having an opening on the first main surface (in the patent document 1 Figure 1 In the embodiment of the present invention, the filter device is a filter device with grooves 11). According to this structure, since the relative dielectric constant of the air filled in the recess is less than the relative dielectric constant of the dielectric constituting the substrate, the electromagnetic coupling generated between adjacent strip conductors can be weakened. Therefore, when the filter device is designed so that the size of the coupling generated between adjacent strip conductors is the same as that of the existing filter device, the intervals between adjacent strip conductors can be narrowed, so the filter device can be miniaturized. However, in such a filter device, further miniaturization is required. Summary of the invention

[0005] One embodiment of the present invention has been made in view of the above-mentioned problems, and an object of the present invention is to reduce the size of a filter device compared with a conventional filter device.

[0006] A filter device according to a first embodiment of the present invention comprises: a dielectric substrate including a first main surface and a second main surface facing each other; a plurality of strip conductors provided on the first main surface side, wherein adjacent strip conductors are electromagnetically coupled to each other; and a ground conductor layer provided at least on the second main surface side, wherein each region between adjacent strip conductors on the first main surface is defined as an intermediate region, and one or more first recesses whose surfaces are covered by the ground conductor layer are formed in regions on the second main surface facing each of the intermediate regions.

[0007] The filter device according to one embodiment of the present invention can be miniaturized. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 (a) is a top view of a filter device according to a first embodiment of the present invention. (b) and (c) are cross-sectional views of the filter device shown in (a).

[0009] Figure 2 yes Figure 1 FIG. 4 is a cross-sectional view of a first modified example of the filter device shown in FIG.

[0010] Figure 3 (a) and (b) are Figure 1 1 and 2 are a plan view and a cross-sectional view of a second modified example of the filter device shown.

[0011] Figure 4 yes Figure 1 A cross-sectional view of a third modified example of the filter device shown.

[0012] Figure 5 (a) is a plan view of a filter device according to a second embodiment of the present invention. (b) and (c) are cross-sectional views of the filter device shown in (a).

[0013] Figure 6 yes Figure 5 FIG. 4 is a cross-sectional view of a first modified example of the filter device shown in FIG.

[0014] Figure 7 (a) Yes Figure 5 (b) and (c) are cross-sectional views of the filter device shown in (a).

[0015] Figure 8 yes Figure 7 An enlarged plan view of one end portion of a strip conductor included in a modification of the filter device shown.

[0016] Fig. 9 (a) is a plan view showing the structure of a first embodiment of the present invention, (b) is a plan view showing the structure of a second embodiment of the present invention, and (c) is a plan view showing the structure of a second comparative example.

[0017] Fig.10 (a) is a graph showing the transmission characteristics of the structures of the first to third examples of the present invention, and (b) is a graph showing the transmission characteristics of the structures of the first and second comparative examples. DETAILED DESCRIPTION

[0018] The filter device of one embodiment of the present invention functions as a bandpass filter, which allows high-frequency signals belonging to a specified passband among high-frequency signals whose frequencies belong to a frequency band called millimeter waves or microwaves to pass, and cuts off other high-frequency signals. In the first embodiment and the second embodiment described below, the case where the center frequency of the passband is included in the 25GHz band is described. However, the center frequency and bandwidth of the passband are not limited and can be appropriately designed according to the purpose of the filter device.

[0019] [First embodiment]

[0020] Reference Figure 1 A filter device 1 according to a first embodiment of the present invention will be described. Figure 1 (a) is a top view of the filter device 1 . Figure 1 (b) and (c) are cross-sectional views of the filter device 1 . Figure 1 (b) is along Figure 1 A cross-sectional view of the cross section taken along the line AA′ shown in (a), Figure 1 (c) is along Figure 1 A cross-sectional view of a cross section taken along line BB′ shown in (a).

[0021] <Structure of filter device>

[0022] like Figure 1 As shown in (a) to (c) of FIG. 8 , the filter device 1 includes a substrate 11 , a conductor pattern 12 , and a ground conductor layer 13 .

[0023] (Substrate)

[0024] The substrate 11 is a dielectric plate-shaped member including a main surface 111 and a main surface 112 facing each other. The main surface 111 is an example of the first main surface described in the claims. The main surface 112 is an example of the second main surface described in the claims.

[0025] In this embodiment, the substrate 11 is made of quartz. However, the dielectric material constituting the substrate 11 is not limited to quartz, and can be appropriately selected. Examples of the dielectric material include semiconductors represented by glass, ceramics, silicon, GaAs, etc. other than quartz, and resins.

[0026] In the present embodiment, the shape of the substrate 11 is a rectangle when the main surface 111 is observed from the direction along the normal line of the main surface 111. However, the shape of the substrate 11 is not limited to a rectangle and can be appropriately determined. In addition, the situation where the main surface 111 is observed from the direction along the normal line of the main surface 111 is referred to as a top view below.

[0027] In this embodiment, the conductor pattern 12 described later is provided on the main surface 111, and the recessed portions 11a1 to 11a2 described later and the ground conductor layer 13 are provided on the main surface 112. However, the conductor pattern 12 may be provided indirectly on the main surface 111 side of the substrate 11, and the ground conductor layer 13 may be provided indirectly on the main surface 112 side of the substrate 11. For example, another layer with low conductivity (for example, a dielectric layer) is interposed between at least one of the main surface 111 and the conductor pattern 12 and between the main surface 112 and the ground conductor layer 13. In addition, the conductor posts 11b1 to 11b3 described later are provided inside the substrate 11.

[0028] (Conductor pattern)

[0029] The conductor pattern 12 provided on the main surface 111 is obtained by forming a conductor film pattern into a predetermined shape. In the present embodiment, the conductor pattern 12 is made of copper. However, the conductor constituting the conductor pattern 12 is not limited to copper and can be appropriately selected. The conductor pattern 12 includes strip conductors 12a1 to 12a3, a coplanar line 12b, and a coplanar line 12c. In addition, in the present embodiment, although the conductor pattern 12 is composed of three strip conductors 12a1 to 12a3, the number of strip conductors constituting the conductor pattern 12 is not limited to three. The number of strip conductors of the conductor pattern 12 only needs to be at least a plurality, and five can be cited as an example other than three.

[0030] like Figure 1 As shown in (a), each of the strip conductors 12a1 to 12a3 has a rectangular shape. Hereinafter, the direction in which each strip conductor 12ai (i is an integer greater than 1 and less than 3) extends (i.e., the direction along the long side of each strip conductor 12ai) is referred to as the length direction. In addition, the direction intersecting the length direction (i.e., the direction along the short side of each strip conductor 12ai) is referred to as the width direction. In each strip conductor 12ai, the length when measured along the length direction is referred to as the length, and the length when measured along the width direction is referred to as the width.

[0031] Each strip conductor 12ai is arranged so that its long sides are parallel. In addition, each strip conductor 12ai is arranged so that the interval between adjacent strip conductors becomes a predetermined value. Each strip conductor 12ai arranged in this way is electromagnetically coupled with the adjacent strip conductor. The interval between adjacent strip conductors is appropriately adjusted so that the coupling amount between adjacent strip conductors becomes a desired size.

[0032] When viewed along the length direction of each strip conductor 12ai, the length of each strip conductor 12ai can be appropriately determined according to the center frequency of the passband and the relative dielectric constant of the substrate 11. In the present embodiment, the length of each strip conductor 12ai is determined so that the frequency becomes 1 / 4 of the effective wavelength of the electromagnetic wave as the above-mentioned center frequency. However, the length of each strip conductor 12ai is not limited to 1 / 4 of the above-mentioned effective wavelength, and may be an integral multiple of 1 / 4.

[0033] The coplanar line 12b is composed of a signal line 12b1 and ground conductor patterns 12b2 and 12b3. One end of the signal line 12b1 is electrically connected to one end of the strip conductor 12a1. The ground conductor patterns 12b2 and 12b3 are arranged to sandwich the signal line 12b1. The coplanar line 12b functions as an input / output port of the filter device 1.

[0034] The coplanar line 12c is composed of a signal line 12c1 and ground conductor patterns 12c2 and 12c3. One end of the signal line 12c1 is electrically connected to one end of the strip conductor 12a3. The ground conductor patterns 12c2 and 12c3 are arranged to sandwich the signal line 12c1. The coplanar line 12c functions as an input / output port of the filter device 1.

[0035] (concave)

[0036] In the main surface 111, each region between adjacent strip conductors is referred to as an intermediate region. Figure 1 As shown in (a), the filter device 1 has three strip conductors 12a1 to 12a3, so that the intermediate region exists between the strip conductor 12a1 and the strip conductor 12a2, and between the strip conductor 12a2 and the strip conductor 12a3. Each of the recesses 11a1 and 11a2 is a recess provided in an area opposite to each of the intermediate regions in the main surface 112. The recesses 11a1 and 11a2 are examples of first recesses. Each of the recesses 11a1 and 11a2 provided in this way is arranged between the adjacent strip conductors 12a1 and 12a2, and between the strip conductors 12a2 and 12a3 in a plan view (see Figure 1 (a)).

[0037] The bottom surface and side surfaces of the surfaces of the respective recessed portions 11aj (j is 1 or 2) are covered by a second grounding conductor layer 132 described later (see Figure 1 (b)).

[0038] In the present embodiment, when each recess 11aj is observed along the direction in which each strip conductor 12ai extends, that is, the length direction, both ends of the recess 11aj protrude more than both ends of the two strip conductors 12ai adjacent to the recess 11aj. For example, when the both ends of the recess 11a1 are observed along the length direction, they protrude more than both ends of either the strip conductor 12a1 or the strip conductor 12a2. However, the length of each recess 11aj may be equal to the length of each strip conductor 12ai, or may be shorter than the length of each strip conductor 12ai. When each recess 11aj is observed along the length direction, at least a portion of each recess 11aj may overlap at least a portion of the adjacent strip conductor 12ai.

[0039] In the present embodiment, the shape of each recess 11aj is a rectangular parallelepiped, but the shape of each recess 11aj is not limited to the rectangular parallelepiped, and can be appropriately determined.

[0040] In the present embodiment, the width of each recess 11aj is approximately the same as the width of each strip conductor 12ai. However, the width of each recess 11aj may be narrower than the width of each strip conductor 12ai or may be equal to the width of each strip conductor 12ai.

[0041] The recess 11aj forms an air layer, so it is difficult for electric lines to pass through compared to the substrate 11 made of dielectric. Providing the recess 11aj will reduce the thickness of the substrate 11 of this part, and reduce the electric lines between the strip conductors 12ai located on both sides of the recess 11aj. In other words, the coupling amount (coupling coefficient between resonators) between the strip conductors 12ai located on both sides of the recess 11aj is reduced. Therefore, in the case where the size of the coupling generated between adjacent strip conductors is designed to be the same as before, the interval between adjacent strip conductors can be narrowed. In other words, the size of the filter device 1 can be reduced.

[0042] Furthermore, the width and depth from the bottom surface of each recess 11 aj are appropriately adjusted so that the coupling amount between adjacent strip conductors 12 ai becomes a desired magnitude.

[0043] (Ground conductor layer)

[0044] The ground conductor layer 13 is at least provided on the main surface 112. Figure 1 As shown in (b), the ground conductor layer 13 includes a first ground conductor layer 131 and a second ground conductor layer 132. The first ground conductor layer 131 of the ground conductor layer 13 is a portion provided on the main surface 112, and the second ground conductor layer 132 is a portion covering the surface of each recess 11aj.

[0045] The ground conductor layer 13 is made of a conductor film. In the present embodiment, the ground conductor layer 13 is made of copper. However, the conductor of the ground conductor layer 13 is not limited to copper, and can be appropriately selected.

[0046] like Figure 1 As shown in (b), the first ground conductor layer 131 and the second ground conductor layer 132 are continuously formed and are also electrically connected. Therefore, the first ground conductor layer 131 and the second ground conductor layer 132 have the same potential.

[0047] (Conductor column)

[0048] Each of the conductor posts 11b1 to 11b3 corresponds to each of the strip conductors 12a1 to 12a3. Each conductor post 11bi (i is an integer greater than or equal to 1 and less than or equal to 3) corresponding to each strip conductor 12ai is provided in a region overlapping one end of each strip conductor 12ai when the main surface 111 is viewed from above (see Figure 1 (a)), and each strip conductor 12ai and the first ground conductor layer 131 are short-circuited (see Figure 1 The conductor post 11b2 shown in (c)).

[0049] Each conductor post 11bi is obtained by forming a conductor film on the inner wall of a through hole provided in the substrate 11 in a region corresponding to one end of each strip conductor 12ai. Alternatively, each conductor post 11bi may be formed of a conductor filled in the through hole.

[0050] The conductor posts 11c1, 11c2, 11c3, 11c4 are provided in regions overlapping the ground conductor patterns 12b2, 12b3, 12c2, 12c3 in a plan view. The conductor posts 11c1, 11c2, 11c3, 11c4 short-circuit the ground conductor patterns 12b2, 12b3, 12c2, 12c3 and the first ground conductor layer 131.

[0051] In the filter device 1, each conductor post 11bi is composed of two conductor posts. However, the number of conductor posts constituting each conductor post 11bi is not limited, and may be one or more than three. In addition, the cross-sectional shape of the conductor post constituting each conductor post 11bi is not limited to a circular shape.

[0052] The filter device 1 having the above-described structure can achieve an effect of being able to be miniaturized compared to a filter device having the same coupling amount using the conventional technology.

[0053] <First Modification>

[0054] Next, refer to Figure 2 To illustrate as Figure 1The filter device 1 shown is a filter device 1A according to a first modified example of the filter device 1 . Figure 2 is a cross-sectional view of the filter device 1A, which is similar to the filter device 1 Figure 1 (b) corresponds to the cross-sectional view. In the filter device 1A, for convenience of description, components having the same functions as those already described in the filter device 1 are denoted by the same reference numerals, and their description is not repeated. The same applies to each modified example described below.

[0055] The filter device 1A is obtained by changing the shape of each recess 11aj from a rectangular parallelepiped to a half-tube shape based on the filter device 1. The half-tube shape of this embodiment is a shape obtained by dividing a tube having an elliptical cross section into two along the center axis of the tube and along the minor axis of the ellipse.

[0056] In the filter device 1, since each recess 11aj is in the shape of a rectangular parallelepiped, a discontinuous corner is formed at the boundary between the bottom surface and the side surface of each recess 11aj (see Figure 1 (b)). However, as in the filter device 1A of this modification, the bottom surface and the side surface of each recess 11aj can also be smoothly connected. In addition, in a further modification of the filter device 1A, based on the filter device 1, the bottom surface of each recess 11aj as a cube can be formed by an arc (e.g., a semicircular shape).

[0057] In this variation, the same effect as in the first embodiment can be obtained. Moreover, by making the shape of the recess 11aj a semi-tube-shaped as in this variation, the thickness of the second ground conductor layer 132 of the recess 11aj can be easily and uniformly formed compared to the case where the shape of the recess 11aj is a rectangular parallelepiped.

[0058] <Second Modification>

[0059] Next, refer to Figure 3 To illustrate Figure 1 A filter device 1B according to a second modified example of the filter device 1 is shown. Figure 3 (a) is a top view of the filter device 1B. Figure 3 (b) is a cross-sectional view of the filter device 1B taken along the line AA′, which is similar to the cross-sectional view of the filter device 1. Figure 1 (b) The corresponding cross-sectional view.

[0060] The filter device 1B is obtained by changing the shape of each recess 11 aj from a single rectangular parallelepiped to a plurality of rectangular parallelepiped shapes with a reduced width based on the filter device 1. Therefore, in this modification, the shape of one recess 11 aj will be described.

[0061] like Figure 3As shown, each concave portion 11aj of the filter device 1B is composed of a left concave portion 11aj1, a middle concave portion 11aj2, and a right concave portion 11aj3. In addition, the terms "left", "middle", and "right" mentioned here are only used to distinguish the three concave portions constituting one concave portion 11aj, and have no other meanings.

[0062] Each of the left concave portion 11aj1, the middle concave portion 11aj2, and the right concave portion 11aj3 is the same as each concave portion 11aj of the filter device 1, and is in a rectangular parallelepiped shape. However, each of the left concave portion 11aj1, the middle concave portion 11aj2, and the right concave portion 11aj3 is narrowed to about 1 / 5 of the width of each concave portion 11aj of the filter device 1. Moreover, each of the left concave portion 11aj1, the middle concave portion 11aj2, and the right concave portion 11aj3 is arranged at equal intervals. In addition, the width of each concave portion 11aj of the filter device 1B is equal to the width of each concave portion 11aj of the filter device 1.

[0063] In this modification, the same effect as the first embodiment can be obtained. Moreover, as in this modification, by dividing each recess 11aj into a plurality of recesses, it is possible to obtain an effect of easy manufacturing compared to the case where a single recess is used. In addition, by setting a plurality of narrow recesses, it is possible to obtain an effect of increasing the strength of the substrate 11 compared to the filter device 1. In addition, in this modification, the above-mentioned first modification can also be applied. Thus, the effect obtained in the first modification can be obtained together.

[0064] <Third Modification>

[0065] Next, refer to Figure 4 To illustrate Figure 1 A filter device 1C according to a third modified example of the filter device 1 is shown. Figure 4 is a cross-sectional view of the filter device 1C, which is similar to the filter device 1 Figure 1 (b) The corresponding cross-sectional view.

[0066] like Figure 4 As shown in FIG. 1 , the concave portion 11aj of the filter device 1C is arranged on both sides of each of the plurality of strip conductors 12ai in a plan view. Specifically, in a plan view, the concave portion 11a1 and the concave portion 11a2 are arranged on both sides of the strip conductor 12a1. In addition, the concave portion 11a3 and the concave portion 11a4 are arranged on both sides of the strip conductor 12a2. Furthermore, the concave portion 11a5 and the concave portion 11a6 are arranged on both sides of the strip conductor 12a3.

[0067] Furthermore, for example, the combined width of two recessed portions 11 aj disposed between two strip conductors 12 ai is made substantially the same as the width of one recessed portion 11 aj of the filter device 1 .

[0068] In this modification, the same effect as the first embodiment can be obtained. In addition, in this modification, the above-mentioned first modification can also be applied. Thus, the effect obtained in the first modification can be obtained together. In addition, the filter device 1C can be expected to have a miniaturized effect from the perspective of impedance control compared to the case where the recess 11aj is not provided. This is because when the impedance is matched, the width of each strip conductor 12ai can be narrowed compared to the case where the recess 11aj is not provided.

[0069] [Second embodiment]

[0070] Next, refer to Figure 5 A filter device 2 according to a second embodiment of the present invention will be described. For convenience of description, components having the same functions as those described in the above embodiment are denoted by the same reference numerals, and description thereof will not be repeated. Figure 5 (a) is a top view of the filter device 2. Figure 5 (b) and (c) are cross-sectional views of the filter device 2 . Figure 5 (b) is along Figure 5 A cross-sectional view of the cross section taken along the line AA′ shown in (a), Figure 5 (c) is along Figure 5 The filter device 2 can also be said to be a cross-sectional view of the cross section of the BB' line shown in (a). Figure 1 Therefore, for the sake of convenience, in the filter device 2, components having the same functions as those described in the filter device 1 are denoted by the same reference numerals, and their descriptions are not repeated. The same applies to the various modifications described hereinafter.

[0071] (Additional recess)

[0072] like Figure 5 As shown, the filter device 2 is based on the filter device 1, and has recessed portions 11d1 to 11d3 in addition to the recessed portions 11a1 to 11a2 on the main surface 112. The recessed portions 11d1 to 11d3 are examples of second recessed portions.

[0073] Each of the recesses 11d1 to 11d3 provided on the main surface 112 corresponds to each of the opposing strip conductors 12a1 to 12a3. Each recess 11di corresponding to each strip conductor 12ai is provided so as to overlap with each strip conductor 12ai when the main surface 111 is viewed from above (see Figure 5 (a)). In the present embodiment, each recess 11di is provided so as to include each strip conductor 12ai. However, each recess 11di only needs to have at least a portion thereof overlap with at least a portion of each strip conductor 12ai.

[0074] The depth of the recess 11di is the same as the depth of the recess 11aj. In addition, the bottom surface and the side surface of each recess 11di are the same as those of the recess 11aj and are covered by the second ground conductor layer 132 (see Figure 5 (b)).

[0075] In the present embodiment, the shape of each recessed portion 11di is a rectangular parallelepiped, but the shape of each recessed portion 11di is not limited to the rectangular parallelepiped, and can be appropriately determined.

[0076] In the present embodiment, the width of each recess 11di exceeds the width of each corresponding strip conductor 12ai. However, the width of each recess 11di may be narrower than or equal to the width of each strip conductor 12ai.

[0077] The interval between each strip conductor 12ai and the bottom surface of each recess 11di is appropriately adjusted so that the coupling amount between each strip conductor 12ai and the second ground conductor layer 132 provided on the bottom surface of each recess 11di becomes a desired magnitude.

[0078] In the present embodiment, when viewed along the longitudinal direction, that is, the direction in which each strip conductor 12ai extends, the length of each recess 11di exceeds the length of the strip conductor 12ai overlapping the recess 11di in a plan view (see FIG. Figure 5 (c)). In addition, when viewed along the length direction of each strip conductor 12ai, each recess 11di includes a strip conductor 12ai overlapping the recess 11di (see Figure 5 (c)). However, the length of each recess 11di may be equal to the length of the strip conductor 12ai overlapping the recess 11di, or may be shorter than the length of the strip conductor 12ai overlapping the recess 11di. In addition, each recess 11di may be such that at least a portion thereof overlaps at least a portion of the strip conductor 12ai corresponding to the recess 11di in a plan view.

[0079] (Conductor column)

[0080] In the present embodiment, each of the conductor posts 11b1 to 11b3 corresponds to each of the strip conductors 12a1 to 12a3. When the principal surface 111 is viewed from above, each conductor post 11bi corresponding to each strip conductor 12ai is provided in a region (in the present embodiment, one end) where each strip conductor 12ai and each recess 11di overlap (see Figure 5 (a)), and each strip conductor 12ai and the second ground conductor layer 132 are short-circuited (refer to Figure 5In addition, the distance between the region including one or more conductor posts 11bi in the bottom surface of the recess 11di and the main surface 111 is constant.

[0081] In addition, in this embodiment, each recess 11di includes each strip conductor 12ai when the main surface 111 is viewed from above. Therefore, each conductor post 11bi is located inside each recess 11di when viewed from above. However, the location where each conductor post 11bi is provided is not limited to the inside of each recess 11di, but may be outside each recess 11di (i.e., the first ground conductor layer) or on the outer edge (i.e., the side surface) of each recess 11di.

[0082] In the second embodiment, in addition to the recesses 11a1 to 11a2, recesses 11d1 to 11d3 are provided. By providing the recesses 11d1 to 11d3, since the interval between each of the plurality of strip conductors 12ai and the ground conductor layer 13 (second ground conductor layer 132) closest to each strip conductor 12ai is narrowed, the electric lines of force generated between the strip conductor 12ai and the ground conductor layer 13 are concentrated in the normal direction of the main surface 111, and are difficult to spread in the in-plane direction of the main surface 111. Therefore, the coupling between adjacent strip conductors 12ai can be weakened. Therefore, in the filter device 2 of the second embodiment, when the size of the coupling generated between adjacent strip conductors 12ai is designed to be approximately the same as in the past, the interval between adjacent strip conductors 12ai can be further narrowed compared to the filter device 1. That is, the size of the filter device 2 can be further reduced.

[0083] In the second embodiment, at least one of the concave portions 11a1 to 11a2 and the concave portions 11d1 to 11d3 may be combined with at least one of the first modification and the second modification of the first embodiment. In this case, the effects corresponding to the modifications can be obtained together.

[0084] <Fourth Modification>

[0085] Next, refer to Figure 6 To illustrate as Figure 5 The filter device 2 shown is a filter device 2A according to a first modification example (a fourth modification example of the present invention). Figure 6 is a cross-sectional view of the filter device 2A, which is similar to the filter device 2 Figure 5 (b) Corresponding cross-sectional view.

[0086] like Figure 6As shown, the depth L1 of the recess 11aj of the filter device 2A is greater (deeper) than the depth L2 of the recess 11di. Specifically, the depth L1 of the recess 11aj is made deeper than that of the filter device 2. As a result, the magnitude of the coupling generated between the adjacent strip conductors 12ai can be further reduced compared to the case where the depth L1 of the recess 11aj and the depth L2 of the recess 11di are the same. In addition, in the fourth modification, for at least any one of the recesses 11a1 to 11a2 and the recesses 11d1 to 11d3, at least any one of the first modification and the second modification can also be combined.

[0087] <Fifth Modification>

[0088] Next, refer to Figure 7 To illustrate as Figure 5 The filter device 2 shown is a filter device 2B of the second modification example (fifth modification example of the present invention). Figure 7 (a) is a top view of the filter device 2B. Figure 7 (b) and (c) are cross-sectional views of the filter device 2B. Figure 7 (b) is along Figure 7 A cross-sectional view of the cross section taken along the line AA′ shown in (a), Figure 7 (c) is along Figure 7 A cross-sectional view of a cross section taken along line BB′ shown in (a).

[0089] (concave)

[0090] The filter device 2B is obtained by shortening the length of the second recesses 11d1 to 11d3 based on the filter device 2. Therefore, in the filter device 2B, one end of each strip conductor 12ai protrudes from the second recess 11di overlapping the strip conductor 12ai in a plan view (see Figure 7 (a) and (c)).

[0091] In addition, when viewed along the length direction of each strip conductor 12ai (see Figure 7 (c)), the position of each second recess 11di is determined so that the interval between each conductor post 11bi and the second grounding conductor layer 132 close to each conductor post 11bi is equal to the interval between each strip conductor 12ai and the bottom surface of each second recess 11di. More specifically, the position of each second recess 11di is determined so that the amount of coupling generated between each conductor post 11bi and the second grounding conductor layer 132 close to the conductor post 11bi (the second grounding conductor layer 132 on the side surface of the second recess 11di that covers the conductor post 11bi) is equal to the amount of coupling generated between each strip conductor 12ai and the second grounding conductor layer 132 provided on the bottom surface of each second recess 11di.

[0092] (Conductor column)

[0093] Each of the conductor posts 11b1 to 11b3 of the filter device 2B is the same as each of the conductor posts 11b1 to 11b3 of the filter device 2, and corresponds to each of the strip conductors 12a1 to 12a3. Each conductor post 11bi corresponding to each strip conductor 12ai is provided in a region where one end of each strip conductor 12ai and one end protruding from each second recess 11di overlaps with the first ground conductor layer 131 when the main surface 111 is viewed from above. Each conductor post 11bi short-circuits the one end and the first ground conductor layer 131. Each conductor post 11bi has a predetermined coupling amount with the second ground conductor layer 132 close to the conductor post 11bi, and thus forms a dual conductor line together with the second ground conductor layer 132.

[0094] In the filter device 2B, in addition to the strip conductors 12ai, the conductor posts 11bi also function as signal lines of the dual-conductor line. Therefore, the length of each strip conductor 12ai can be made shorter than that of the filter device 2 by the thickness of the substrate 11.

[0095] In addition, in the present embodiment, each conductor post 11bi is composed of two conductor posts. However, the number of conductor posts constituting each conductor post 11bi is not limited. In addition, in order to reduce the difference between the width of each strip conductor 12ai and the effective width of each conductor post 11bi, (1) when the conductor posts constituting each conductor post 11bi are separated from each other, it is preferred that the total value of the diameters of the conductor posts constituting each conductor post 11bi is close to the width of each strip conductor 12ai, and (2) when the conductor posts constituting each conductor post 11bi are integrated with each other, it is preferred that the width of each conductor post 11bi (the length of each conductor post 11bi along the width direction of each strip conductor 12ai) is close to the width of each strip conductor 12ai.

[0096] <Sixth Modification>

[0097] Reference Figure 8 To illustrate as Figure 7 A filter device 2C is shown as a modified example of the filter device 2B. Figure 8 1 is an enlarged plan view of one end of a strip conductor 12a2 as one of the strip conductors included in the filter device 2C. For ease of description, in the filter device 2C, components having the same functions as those described in the filter device 2B are denoted by the same reference numerals, and their descriptions are not repeated.

[0098] The filter device 2C is obtained by changing the shape of each conductor post 11bi based on the filter device 2B. Figure 8 Although the conductor post 11b2 is shown as an example of each conductor post 11bi, the other conductor posts 11b1 and 11b3 are configured similarly to the conductor post 11b2.

[0099] Specifically, each conductor post 11bi of the filter device 2B is composed of two conductor posts whose cross-sectional shape is a circle. In contrast, each conductor post 11bi of the filter device 2C is composed of eight conductor posts whose cross-sectional shape is a circle, and is configured so that the center-to-center distance between adjacent conductor posts is narrower than the diameter of each conductor post. As a result, when viewed along the width direction of each strip conductor 12ai, the width of each conductor post 11bi of the filter device 2C becomes the same as the width of each strip conductor 12ai.

[0100] In addition, in this embodiment, the width of each conductor post 11bi is 92.5% of the width of each strip conductor 12ai. However, the width of each conductor post 11bi is not limited to this. In addition, in order to improve the continuity of each strip conductor 12ai and each conductor post 11bi, it is preferred that the ratio of the width of each conductor post 11bi to the width of each strip conductor 12ai is 80% or more and 120% or less.

[0101] [Example]

[0102] Next, refer to Fig. 9 as well as Fig.10 First to third embodiments of the present invention and a first comparative example and a second comparative example will be described. Fig. 9 (a) is a top view showing the structure of the first embodiment of the present invention, Fig. 9 (b) is a top view showing the structure of the second embodiment of the present invention, Fig. 9 (c) is a plan view showing the structure of the second comparative example. Fig.10 (a) is a graph showing the frequency dependence of the transmission intensity of the structures of the first to third embodiments of the present invention, Fig.10 (b) is a graph showing the frequency dependency of the transmission intensity of the structures of the first comparative example and the second comparative example. In addition, the frequency dependency of the transmission intensity is hereinafter referred to as transmission characteristics.

[0103] Each of the examples and comparative examples has a quartz glass substrate; two strip conductors A1 and A2 provided in parallel with each other on a first main surface which is one main surface of the substrate; and a ground conductor layer provided on a second main surface which is the other main surface of the substrate.

[0104] If using Fig. 9 The structure of the first embodiment shown in (a) and Figure 3The correspondence between the structures of the embodiments and comparative examples and the filter devices of the embodiments is explained by using the filter device 1B of the second variant shown as follows. That is, the substrate, strip conductor, and ground conductor layer of the structure of the first embodiment correspond to the substrate 11, strip conductor 12ai (i is two consecutive ones from 1, 2, and 3), and ground conductor layer 13 of the filter device 1B, respectively. In this way, the structures of the embodiments and comparative examples can be said to be the structure of the filter device having multiple strip conductors, from which the minimum structure of multiple coupled strip conductors, that is, the structure of two strip conductors, is extracted. In addition, in Fig. 9 In (a) to (c) of FIG. 1 , the outer edge of the substrate and the ground conductor layer are omitted from illustration.

[0105] In each of the examples and comparative examples, a quartz glass substrate having a relative dielectric constant of 3.82 and a thickness of 400 μm was used, and the shapes of the strip conductors A1 and A2 were determined as follows (see Fig. 9 (a) to (c)). The strip conductors A1 and A2 are 350 μm wide and 1550 μm long rectangles, and the interval between the strip conductors A1 and A2 is 350 μm. The dimensions related to the strip conductors A1 and A2 are shown in FIG. Fig. 9 As shown in (a), in the same size Fig. 9 The illustration is omitted in (b) and (c). In addition, the recessed portion provided in each embodiment and the second comparative example will be described later.

[0106] The results of simulating the frequency dependence of the transmission intensity using the structure thus constructed as a calculation model in each embodiment and each comparative example are shown in FIG. Fig.10 middle.

[0107] In addition, as in the structures of each embodiment and each comparative example, it is known that in two electromagnetically coupled strip conductors, the coupling coefficient k between adjacent strip conductors is expressed by the following equation (1). In addition, each of the two strip conductors operates as a resonator.

[0108] [Number 1]

[0109]

[0110] Here, the coupling coefficient k is an index indicating the strength of the coupling between resonators. The larger the coupling coefficient k, the stronger the coupling between resonators. h is the resonant frequency on the higher frequency side, f l It is the resonant frequency on the smaller frequency side.

[0111] (First embodiment)

[0112] like Fig. 9 As shown in (a), in the structure of the first embodiment, a recess B1 is provided in an area between adjacent strip conductors A1 and A2 in an area of ​​the second main surface of the substrate that is not opposed to the strip conductors A1 and A2. The recess B1 is an example of a first recess. Although each recess 11aj of the filter device 1B is composed of three recesses 11aj1, 11aj2, and 11aj3, the recess B1 of the present embodiment is composed of two recesses B11 and B12. The shapes of the recesses B11 and B12 are rectangular parallelepipeds with a width of 100μm, a length of 1550μm, and a depth of 250μm, respectively. In addition, the interval between the recess B11 and the recess B12 is 100μm. In addition, when viewed from above, the interval between the strip conductor A1 and the recess B11 and the interval between the recess B12 and the strip conductor A2 are 25μm, respectively.

[0113] (Second embodiment)

[0114] like Fig. 9 As shown in (b), the structure of the second embodiment is based on the structure of the first embodiment, and is obtained by providing a recess C1 in the area of ​​the second main surface of the substrate that overlaps with the strip conductor A1 when viewed from above, and providing a recess C2 in the area that overlaps with the strip conductor A2 when viewed from above. Recesses C1 and C2 are examples of second recesses. Recess C1 is composed of recesses C11 and C12, and recess C2 is composed of recesses C21 and C22. The shapes of recesses C11, C12, C21, and C22 are rectangular parallelepipeds with a width of 100μm, a length of 1550μm, and a depth of 250μm, respectively. The interval between recess C11 and recess C12 and the interval between recess C21 and recess C22 are 100μm. The distance from the long side of the strip conductor A1 to each of recess C11 and recess C12 is 25μm. The structure of the second embodiment can be said to be a combination of the above. Figure 5 The filter device 2 shown has a deformed structure of the recessed portions 11a1, 11a2, 11d1, 11d2, and 11d3.

[0115] (Third Embodiment)

[0116] The third embodiment is constructed with Fig. 9 The structure of the second embodiment shown in (b) is used as a basis, but the depth of the recesses C1 and C2 is changed from 250 μm to 300 μm. Therefore, the structure of the third embodiment is identical to that of the second embodiment in a plan view.

[0117] (First Comparative Example)

[0118] The structure of the first comparative example is Fig. 9The first comparative example is obtained by omitting the concave portion B1 based on the first embodiment shown in (a) of FIG. 1. In the first comparative example, no concave portion is formed on either the first principal surface or the second principal surface of the substrate.

[0119] (Second Comparative Example)

[0120] like Fig. 9 As shown in (c), the structure of the second comparative example is based on the structure of the first comparative example, and is obtained by providing a recess D1 in a region between adjacent strip conductors A1 and A2 in a region of the substrate where the strip conductors A1 and A2 of the first main surface are not provided. The structure of the second comparative example corresponds to the structure shown in the figure of Patent Document 1.

[0121] from Fig.10 The coupling coefficients k obtained from the transmission characteristics of the first example, the second example, and the third example shown in (a) are 0.0864, ​​0.0621, and 0.0466, respectively.

[0122] On the other hand, from Fig.10 The coupling coefficients k obtained from the transmission characteristics of the first comparative example and the second comparative example shown in (b) are 0.185 and 0.149, respectively.

[0123] According to the above results, it can be seen that the structure of the second comparative example can reduce the coupling coefficient k compared to the structure of the first comparative example in which the recess is not provided, but each of the first embodiment, the second embodiment, and the third embodiment can make the coupling coefficient k smaller than that of the second comparative example. In other words, it can be seen that when manufacturing a filter device having the same coupling coefficient as the prior art, the filter device of one embodiment of the present invention can be miniaturized compared to the filter device of the prior art.

[0124] 〔Summarize〕

[0125] A filter device according to a first embodiment of the present invention comprises: a dielectric substrate including a first main surface and a second main surface facing each other; a plurality of strip conductors provided on the first main surface side and electromagnetically coupled to adjacent strip conductors; and a ground conductor layer provided at least on the second main surface side, wherein each region between adjacent strip conductors on the first main surface is defined as an intermediate region, and one or more first recesses whose surfaces are covered by the ground conductor layer are formed in regions on the second main surface facing each of the intermediate regions.

[0126] According to the above structure, it is different from a filter device in which no recess is provided on the substrate (for example, the filter device disclosed in Patent Document 1). Figure 3Compared with the filter device described in the prior art, the size of the coupling generated between adjacent strip conductors is reduced. Therefore, in the case where the size of the coupling generated between adjacent strip conductors is designed to be the same as in the past, the interval between adjacent strip conductors is narrowed, so the filter device can be miniaturized compared with the existing filter device. This is because compared with the filter device in which no recess is provided on the substrate between adjacent strip conductors, an air layer such as a recess is formed on the substrate between adjacent strip conductors, thereby reducing the lines of force between adjacent strip conductors.

[0127] In addition, in addition to the structure of the filter device of the first embodiment, the filter device of the second embodiment of the present invention further adopts a structure in which, for each of the one or more first recesses, when viewed along the direction in which each of the multiple strip conductors extends, that is, the length direction, both ends of each of the one or more first recesses protrude more than both ends of two strip conductors adjacent to the first recess.

[0128] According to the above configuration, the ground conductor layer provided on the bottom surface of the recess has a size sufficient as a ground conductor layer constituting the microstrip line.

[0129] In addition, in addition to the structure of the filter device of the first embodiment or the second embodiment, the filter device of the third embodiment of the present invention further adopts a structure in which, for each of the above-mentioned multiple strip conductors, one or more second recesses are formed on the above-mentioned second main surface, overlapping with the strip conductor when viewed from above and the surface of which is covered by the above-mentioned ground conductor layer.

[0130] According to the above structure, since the interval between each of the multiple strip conductors and the grounding conductor layer closest to each strip conductor is narrowed, the electric lines generated between the strip conductor and the grounding conductor layer are concentrated in the normal direction of the first main surface and are difficult to expand in the in-plane direction of the first main surface, so the coupling between adjacent strip conductors can be further weakened.

[0131] Furthermore, in addition to the structure of the filter device of the third embodiment described above, a filter device according to a fourth embodiment of the present invention adopts a structure in which the depth of the first recessed portion is deeper than the depth of the second recessed portion.

[0132] According to the above configuration, the coupling between adjacent strip conductors can be further weakened.

[0133] In addition, in addition to the structure of the filter device of the third embodiment or the fourth embodiment, the filter device of the fifth embodiment of the present invention further adopts a structure in which, when viewed along the direction in which each of the plurality of strip conductors extends, that is, the length direction, for each of the second recesses, in a plan view, the length of the second recess exceeds the length of the strip conductor overlapping the second recess in the plan view, and the second recess includes the strip conductor.

[0134] According to the above configuration, the ground conductor layer provided on the bottom surface of the recess has a size sufficient as a ground conductor layer constituting the microstrip line.

[0135] In addition, in addition to the structure of the filter device of any one of the first to fifth embodiments described above, the filter device of the sixth embodiment of the present invention further adopts a structure in which, for each of the above-mentioned multiple strip conductors, one or more conductor posts are arranged in an area where the strip conductor and the second recess overlap when viewed from above and short-circuit the strip conductor and the above-mentioned ground conductor layer.

[0136] According to the above configuration, the strip conductor and the second recess can be short-circuited by the short conductor post, so that a single-ended short strip resonator with the reactance suppressed to a minimum can be realized.

[0137] In addition, in addition to the structure of the filter device of the third embodiment or the fourth embodiment, the filter device of the seventh embodiment of the present invention further adopts a structure in which the grounding conductor layer provided on the second main surface is set as a first grounding conductor layer, and the grounding conductor layer covering the surface of the one or more second recesses is set as a second grounding conductor layer, and for each of the plurality of strip conductors, one end of the strip conductor protrudes from the second recess overlapping with the strip conductor in a plan view, and one or more conductor posts are provided corresponding to each of the plurality of strip conductors, the conductor posts being provided in a region where the one end overlaps with the first grounding conductor layer in a plan view and short-circuiting the one end and the first grounding conductor layer, and forming a dual conductor line together with the second grounding conductor layer in the second grounding conductor layer covering the side surface of the second recess.

[0138] According to the above structure, in addition to each strip conductor and the second ground conductor layer provided on the bottom surface of the second recess functioning as a dual conductor line, one or more conductor posts and the second ground conductor layer provided on the side surface of the second recess also function as a dual conductor line. Therefore, the filter device of the seventh embodiment can shorten the length of each strip conductor in the longitudinal direction, so that the filter device can be miniaturized in the longitudinal direction.

[0139] [Additional Notes]

[0140] The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims. Embodiments obtained by appropriately combining the technical mechanisms disclosed in different embodiments are also included in the technical scope of the present invention.

[0141] Description of Reference Numerals

[0142] 1…Filter device

[0143] 11...Substrate

[0144] 111, 112 ... main surface (first main surface, second main surface)

[0145] 11a1~11a2…first concave portion

[0146] 11b1~11b3、11c1~11c4…conductor column

[0147] 11d1~11d3…the second concave part

[0148] 12…Conductor pattern

[0149] 12a1~12a3…Strip conductor

[0150] 12b, 12c…coplanar line

[0151] 12b1, 12c1…signal line

[0152] 12b2, 12b3, 12c2, 12c3…ground conductor pattern

[0153] 13…Ground conductor layer

[0154] 131, 132 ... a first grounding conductor layer and a second grounding conductor layer.

Claims

1. A filter device, It is characterized in that have: A dielectric substrate including a first main surface and a second main surface facing each other; a plurality of strip conductors disposed on the first main surface, wherein adjacent strip conductors are electromagnetically coupled to each other; as well as a ground conductor layer provided at least on the second main surface side, Each region between adjacent strip conductors on the first main surface is defined as an intermediate region, and one or more first recesses whose surfaces are covered by the ground conductor layer are formed in regions on the second main surface that are opposite to each of the intermediate regions. For each of the plurality of strip conductors, one or more second recessed portions are formed on the second main surface, overlapping the strip conductor in a plan view and having a surface covered by the ground conductor layer. When viewed along the direction in which each of the plurality of strip conductors extends, that is, along the length direction, for each of the second recesses, in a plan view, the length of the second recess exceeds the length of the strip conductor overlapping the second recess in the plan view, and the second recess includes the strip conductor. Each of the plurality of strip conductors further includes one or more conductor posts which are provided in a region where the strip conductor and the second recess overlap in a plan view and which short-circuit the strip conductor and the ground conductor layer.

2. The filter device according to claim 1, It is characterized in that When viewed along the longitudinal direction in which each of the plurality of strip conductors extends, both ends of each of the one or more first recesses protrude further than both ends of two strip conductors adjacent to the first recess.

3. The filter device according to claim 1 or 2, It is characterized in that The depth of the first recessed portion is deeper than the depth of the second recessed portion.

4. A filter device, It is characterized in that have: A dielectric substrate including a first main surface and a second main surface facing each other; a plurality of strip conductors disposed on the first main surface, wherein adjacent strip conductors are electromagnetically coupled to each other; as well as a ground conductor layer provided at least on the second main surface side, Each region between adjacent strip conductors on the first main surface is defined as an intermediate region, and one or more first recesses whose surfaces are covered by the ground conductor layer are formed in regions on the second main surface that are opposite to each of the intermediate regions. For each of the plurality of strip conductors, one or more second recessed portions are formed on the second main surface, overlapping the strip conductor in a plan view and having a surface covered by the ground conductor layer. The ground conductor layer provided on the second main surface is set as a first ground conductor layer, and the ground conductor layer covering the surface of the one or more second recesses is set as a second ground conductor layer. For each of the plurality of strip conductors, one end of the strip conductor protrudes from a second recessed portion overlapping the strip conductor in a plan view. Corresponding to each of the above-mentioned multiple strip conductors, there is also one or more conductor posts, which are arranged in an area where the above-mentioned one end and the above-mentioned first grounding conductor layer overlap when viewed from above and short-circuit the above-mentioned one end and the above-mentioned first grounding conductor layer, and together with the second grounding conductor layer in the above-mentioned second grounding conductor layer covering the side surface of the above-mentioned second recess, form a dual conductor line.

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