Filter device

Abstract

To miniaturize a filter device. The filter device (1) includes: a substrate (11) including a first main surface and a second main surface (111, 112); a plurality of strip conductors (12a1 to 12a5) provided on the first main surface (111); and a ground conductor layer (13) provided at least on the second main surface (112). For each strip conductor (12ai), a recess (11ai) is formed on the second main surface (112). The recess (11ai) overlaps with the strip conductor (12ai) in a plan view, and the surface thereof is covered with the ground conductor layer (13).

Description

Technical Field

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

[0002] In Patent Document 1 Figure 3 and Figure 4 as an existing 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) disposed on the first main surface of the substrate and electromagnetically coupled to each other, and a ground conductor layer disposed on the second main surface of the substrate (ground conductor 2 in Patent Document 1). In addition, each of the plurality of strip conductors functions as a resonator.

[0003] Patent Document 1: Japanese Patent Laid-Open Gazette "JP-A-9-139605"

[0004] On this basis, in Patent Document 1 Figure 1 a filter device is illustrated, in a region of the substrate that does not overlap with each of the strip conductors of the above-mentioned plurality of strip conductors (resonant conductors 5 and 6 in Patent Document 1 Figure 1 in a plan view), recesses (grooves 11 in Patent Document 1 Figure 1 in a plan view) having openings on the first main surface are respectively provided. According to this structure, since the relative dielectric constant of the air filling the recesses is smaller than the relative dielectric constant of the dielectric constituting the substrate, the electromagnetic coupling generated between adjacent strip conductors can be weakened. Therefore, in the case where the magnitude of the coupling generated between adjacent strip conductors is designed to be the same as that in the past, the interval between adjacent strip conductors can be made narrower, and thus the filter device can be miniaturized. However, in such a filter device, further miniaturization is required. Summary of the Invention

[0005] One aspect of the present invention is made in view of the above problems, and its object is to miniaturize the filter device more than before.

[0006] The filter device according to the first aspect of the present invention includes: a dielectric substrate including opposed first and second main surfaces; a plurality of strip conductors disposed on the first main surface side and electromagnetically coupled to each other; and a ground conductor layer disposed at least on the second main surface side. For each of the plurality of strip conductors, one or more recesses are formed on the second main surface of the substrate, the one or more recesses overlap with the strip conductor in a plan view, and the surface is covered by the ground conductor layer.

[0007] A filter device according to one aspect of the present invention can miniaturize the filter device. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0009] Figure 2 is Figure 1 a cross-sectional view of a first modification of the filter device shown in.

[0010] Figure 3 (a) of and Figure 3 (b) of are respectively Figure 1 a top view and a cross-sectional view of a second modification of the filter device shown in.

[0011] Figure 4 is Figure 1 a cross-sectional view of a third modification of the filter device shown in.

[0012] Figure 5 is Figure 1 a cross-sectional view of a fourth modification of the filter device shown in.

[0013] Figure 6 (a) of is a top view of the filter device according to the second embodiment of the present invention. Figure 6 (b) of and Figure 6 (c) of are Figure 6 cross-sectional views of the filter device shown in (a) of.

[0014] Figure 7 is Figure 6 an enlarged top view of one end of a strip conductor included in a modification of the filter device shown in.

[0015] Figure 8 is a top view of the filter device as an example of the present invention.

[0016] Figure 9 is a graph showing the frequency dependence of the transmission intensity of the filter devices as an example of the present invention, a first comparative example, and a second comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0017] A filter device according to an embodiment of the present invention functions as a band-pass filter that allows a high-frequency signal belonging to a specified passband among high-frequency signals having a frequency belonging to a band called millimeter wave or microwave to pass through, and blocks high-frequency signals other than that. In the first embodiment and the second embodiment described below, the case where the center frequency of the passband is included in the 25 GHz band is described. However, the center frequency and bandwidth of the passband are not limited, and can be appropriately designed according to the use of the filter device.

[0018] 〔First Embodiment〕

[0019] Refer to Figure 1 The filter device 1 according to the first embodiment of the present invention will be described. Figure 1 The (a) of is a top view of the filter device 1. Figure 1 The (b) of and Figure 1 The (c) of is a cross-sectional view of the filter device 1. Figure 1 The (b) of is a cross-sectional view taken along the cross-section under the A-A' line shown in the (a) of Figure 1 , and Figure 1 The (c) of is a cross-sectional view taken along the cross-section under the B-B' line shown in the (a) of Figure 1 .

[0020] <Structure of Filter Device>

[0021] As shown in the (a) to (c) of Figure 1 , the filter device 1 includes a substrate 11, a conductor pattern 12, and a ground conductor layer 13.

[0022] (Substrate)

[0023] The substrate 11 is a plate-like member made of a dielectric including opposed main surfaces 111 and 112. The main surface 111 is an example of the first main surface described in the technical solution. The main surface 112 is an example of the second main surface described in the technical solution.

[0024] In the present embodiment, the substrate 11 is made of quartz. However, the dielectric constituting the substrate 11 is not limited to quartz, and can be appropriately selected. Examples of such a dielectric include glass, ceramics, semiconductors represented by silicon, GaAs, etc., other than quartz, and resins.

[0025] In the present embodiment, the shape of the substrate 11 is rectangular when viewed from above the main surface 111 in the direction along the normal line of the main surface 111. However, the shape of the substrate 11 is not limited to rectangular, and can be appropriately determined. In addition, hereinafter, viewing the main surface 111 in the direction along the normal line of the main surface 111 will be referred to as a top view.

[0026] In the present embodiment, a conductor pattern 12 described later is provided on the main surface 111, and concave portions 11a1 to 11a5 and a ground conductor layer 13 described later are provided on the main surface 112. However, the conductor pattern 12 may be indirectly provided on the main surface 111 side of the substrate 11, and the ground conductor layer 13 may be indirectly provided on the main surface 112 side of the substrate 11. For example, at least one of a layer with low conductivity (such as a dielectric layer) may be interposed between the main surface 111 and the conductor pattern 12 and between the main surface 112 and the ground conductor layer 13. In addition, conductor posts 11b1 to 11b5 described later are provided inside the substrate 11.

[0027] (Conductor pattern)

[0028] The conductor pattern 12 provided on the main surface 111 is obtained by patterning a conductor film into a prescribed 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 12a5, a coplanar line 12b, and a coplanar line 12c. In addition, in the present embodiment, the conductor pattern 12 is constituted by five strip conductors 12a1 to 12a5, but the number of strip conductors constituting the conductor pattern 12 is not limited to five.

[0029] As Figure 1 shown in (a) of FIG., the shapes of the strip conductors 12a1 to 12a5 are each rectangular. Hereinafter, the direction in which each strip conductor 12ai (i is an integer of 1 or more and 5 or less) extends (that is, 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 (that is, the direction along the short side of each strip conductor 12ai) is referred to as the width direction. In addition, in each strip conductor 12ai, the length measured along the length direction is referred to as the length, and the length measured along the width direction is referred to as the width.

[0030] Each strip conductor 12ai is arranged such that their long sides are parallel to each other. In addition, each strip conductor 12ai is arranged such that the interval between adjacent strip conductors is a prescribed value. Each strip conductor 12ai arranged in this way is electromagnetically coupled to an adjacent strip conductor. The interval between adjacent strip conductors is appropriately adjusted so that the coupling amount between adjacent strip conductors becomes a desired magnitude.

[0031] When observing in 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 such that the frequency is 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 also be an integer multiple of 1 / 4.

[0032] The coplanar line 12b is composed of a signal line 12b1 and ground conductor patterns 12b2, 12b3. One end of the signal line 12b1 is electrically connected to one end of the strip conductor 12a1. The ground conductor patterns 12b2, 12b3 are respectively arranged to sandwich the signal line 12b1. The coplanar line 12b functions as an input / output port of the filter device 1.

[0033] The coplanar line 12c is composed of a signal line 12c1 and ground conductor patterns 12c2, 12c3. One end of the signal line 12c1 is electrically connected to one end of the strip conductor 12a5. The ground conductor patterns 12c2, 12c3 are respectively arranged to sandwich the signal line 12c1. The coplanar line 12c functions as an input / output port of the filter device 1.

[0034] (Recess)

[0035] The recesses 11a1 to 11a5 provided on the main surface 112 respectively correspond to the opposed strip conductors 12a1 to 12a5. Each recess 11ai corresponding to each strip conductor 12ai is provided to overlap with each strip conductor 12ai when observing the main surface 111 from above (refer to Figure 1 (a)). In the present embodiment, each recess 11ai is provided to include each strip conductor 12ai. However, each recess 11ai only needs to overlap at least a part of each strip conductor 12ai at least partially.

[0036] In addition, the bottom surface and side surfaces of the surface constituting each recess 11ai are covered with a second ground conductor layer 132 to be described later (refer to Figure 1 (b)).

[0037] In the present embodiment, the shape of each recess 11ai is a rectangular parallelepiped shape. However, the shape of each recess 11ai is not limited to the rectangular parallelepiped shape, and can be appropriately determined.

[0038] In the present embodiment, the width of each recess 11ai is larger than the width of the corresponding strip conductor 12ai. However, the width of each recess 11ai may also be narrower than the width of each strip conductor 12ai, or may be equal to the width of each strip conductor 12ai.

[0039] In addition, the intervals between the respective strip conductors 12ai and the bottom surfaces of the respective recesses 11ai are appropriately adjusted such that the coupling amounts between the respective strip conductors 12ai and the second ground conductor layer 132 provided on the bottom surfaces of the respective recesses 11ai are of a desired magnitude.

[0040] In the present embodiment, when viewed in the direction in which the respective strip conductors 12ai extend, that is, the length direction, the length of each recess 11ai is greater than the length of the strip conductor 12ai that overlaps with the recess 11ai in a top view (see Figure 1 (c)). Further, when viewed in the length direction of the respective strip conductors 12ai, each recess 11ai includes the strip conductor 12ai that overlaps with the recess 11ai (see Figure 1 (a)).

[0041] (Ground Conductor Layer)

[0042] The ground conductor layer 13 is provided at least on the main surface 112. Specifically, as shown in Figure 1 (b), the ground conductor layer 13 is composed of a first ground conductor layer 131 and a second ground conductor layer 132. The first ground conductor layer 131 in the ground conductor layer 13 refers to the portion provided on the main surface 112, and the second ground conductor layer 132 refers to the portion covering the surfaces of the respective recesses 11ai.

[0043] The ground conductor layer 13 is formed of a conductor film. In the present embodiment, the ground conductor layer 13 is made of copper. However, the conductor forming the ground conductor layer 13 is not limited to copper and can be appropriately selected.

[0044] As shown in Figure 1 (b), the first ground conductor layer 131 and the second ground conductor layer 132 are formed continuously and are also electrically connected. Therefore, the first ground conductor layer 131 and the second ground conductor layer 132 are at the same potential.

[0045] (Conductor Posts)

[0046] The conductor posts 11b1 to 11b5 respectively correspond to the strip conductors 12a1 to 12a5. Each conductor post 11bi corresponding to each strip conductor 12ai is provided in the region where the respective strip conductor 12ai overlaps with the respective recess 11ai (in one end portion in the present embodiment) when the main surface 111 is viewed from above (see Figure 1 (a)), and shorts each strip conductor 12ai to the second ground conductor layer 132 (see the conductor posts 11b2 and 11b4 shown in Figure 1 (b)).

[0047] Each conductor post 11bi is obtained by forming a conductor film on the inner wall of a through-hole in a region corresponding to one end of each strip conductor 12ai provided in the substrate 11. In addition, each conductor post 11bi may also be composed of a conductor filled in the above through-hole.

[0048] In addition, in the present embodiment, when observing the main surface 111 from above, each recess 11ai includes each strip conductor 12ai. Therefore, when viewed from above, each conductor post 11bi is located inside each recess 11ai. However, the position where each conductor post 11bi is provided is not limited to the inside of each recess 11ai, and may also be outside each recess 11ai (i.e., the first ground conductor layer), or may be on the outer edge (i.e., the side surface) of each recess 11ai.

[0049] Conductor posts 11c1, 11c2, 11c3, and 11c4 are respectively provided in regions that overlap with the ground conductor patterns 12b2, 12b3, 12c2, and 12c3 when viewed from above. Conductor posts 11c1, 11c2, 11c3, and 11c4 respectively short-circuit the ground conductor patterns 12b2, 12b3, 12c2, and 12c3 to the first ground conductor layer 131.

[0050] In addition, 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 also be one, or three or more. In addition, the cross-sectional shape of the conductor posts constituting each conductor post 11bi is not limited to a circular shape.

[0051] <First modification example>

[0052] Next, with reference to Figure 2 to Figure 1 a filter device 1A, which is a first modification example of the filter device 1 shown, will be described. Figure 2 is a cross-sectional view of the filter device 1A and is a cross-sectional view corresponding to (b) of the filter device 1. In addition, for ease of explanation, in the filter device 1A, components having the same functions as those described with the filter device 1 are labeled with the same reference numerals, and their descriptions will not be repeated. This is the same for each modification example described later. Figure 1

[0053] The filter device 1A is obtained by changing the shape of each recess 11ai from a rectangular parallelepiped shape to a semi-tubular shape based on the filter device 1. The semi-tubular shape in the present embodiment refers to a shape obtained by dividing a tube with an elliptical cross-section into two parts along the central axis of the tube and along the minor axis of the elliptical shape.

[0054] ​In the filter device 1, since each recess 11ai has a rectangular parallelepiped shape, a discontinuous corner is formed at the boundary between the bottom surface and the side surface of each recess 11ai (see Figure 1 (b) of

[0055] ). However, as in the filter device 1A of this modification example, the bottom surface and the side surface of each recess 11ai can also be smoothly connected. Further, in another modification example of the filter device 1A, the bottom surface of each recess 11ai of the cube can also be formed of an arc (for example, a semi-circular shape) based on the filter device 1.

[0056] <Second Modification Example>

[0057] Next, with reference to Figure 3 a description will be given of a filter device 1B which is a second modification example of the filter device 1 Figure 1 shown in Figure 3 (a) of Figure 3 is a top view of the filter device 1B. Figure 1 (b) of

[0058]

[0059] Figure 3 The filter device 1B is obtained by changing the shape of each recess 11ai from a rectangular parallelepiped shape to an E shape when the main surface 111 is viewed from above, based on the filter device 1. Therefore, in this modification example, the shape of each recess 11ai will be described. Figure 3 As

[0060] shown, each recess 11ai of the filter device 1B is composed of a first recess 11ai1, a second recess 11ai2, a third recess 11ai3, and a fourth recess 11ai4.

[0061] When observing the main surface 111 from above, the fourth recess 11ai4 is provided in a region including each conductor post 11bi. The fourth recess 11ai4 is arranged such that the first recess 11ai1, the second recess 11ai2, and the third recess 11ai3 communicate with each other, and its long side direction is along the width direction of each strip conductor 12ai. The distance between the bottom surface of the fourth recess 11ai4, which is the region including each conductor post 11bi among the bottom surfaces of the respective recesses 11ai, and the main surface 111 is constant.

[0062] In addition, in the filter device 1B, the fourth recess 11ai4 can also be omitted. In this case, each recess 11ai of the filter device 1B is composed of the first recess 11ai1, the second recess 11ai2, and the third recess 11ai3, which are three recesses.

[0063] In this modified example, the same effect as that of the first embodiment can also be obtained. Moreover, as in this modified example, by forming each recess 11ai by dividing it into a plurality of recesses, an effect of being easier to manufacture compared to forming with a single recess is obtained. In addition, by providing a plurality of recesses with a narrow width, an effect of further improving the strength of the substrate 11 compared to the filter device 1 can be obtained. Furthermore, in this modified example, the above-described first modified example can also be applied. Thus, the effects obtained by the first modified example can be obtained together.

[0064] <Third and Fourth Modified Examples>

[0065] Refer to Figure 4 Regarding Figure 1 the filter device 1C, which is a third modified example of the filter device 1 shown. In addition, refer to Figure 5 the filter device 1D, which is a fourth modified example of the filter device 1. Figure 4 is a cross-sectional view of the filter device 1C and is a cross-sectional view corresponding to (b) in Figure 1 the filter device 1. Figure 5 is a cross-sectional view of the filter device 1D and is a cross-sectional view corresponding to (b) in Figure 1 the filter device 1.

[0066] As Figure 4 shown, the filter device 1C further includes a metal shield 14 based on the filter device 1. The shield 14 is obtained by forming a metal plate (for example, stamping). The shield 14 has a top plate provided along the main surface 111 and side walls provided to surround the side of the top plate. The top plate is separated from each strip conductor 12ai and covers each strip conductor 12ai. In addition, the side walls surround the sides of each strip conductor 12ai.

[0067] In addition, on the main surface 111 of the substrate 11 that constitutes the filter device 1C, a strip conductor 12d is provided so as to surround its outer edge. The strip conductor 12d is short-circuited with the first ground conductor layer 131 through Figure 4 a conductor post (not shown) in

[0068] The lower end of the side wall of the shield 14 is fixed to the strip conductor 12d using solder (not shown in Figure 4 ) as an example of a connection component. However, the connection component only needs to be a component having conductivity and capable of fixing metals to each other, and is not limited to solder. As other examples of the connection component, silver paste can be cited. The shield 14 configured in this way is short-circuited with the first ground conductor layer 131 via the strip conductor 12d and the conductor post.

[0069] As Figure 5 shown, the filter device 1D further includes a shield 15 based on the filter device 1. The shield 15 includes a dielectric substrate 15a, a plurality of conductor posts 15b arranged in a grid pattern at the outer edge portion of the substrate 15a, and a conductor layer 15c.

[0070] The conductor layer 15c is provided to cover the main surface on the side of the pair of main surfaces of the substrate 15a that is far from the substrate 11. The conductor layer 15c corresponds to the top plate included in the shield 14, separates from each strip conductor 12ai, and covers each strip conductor 12ai.

[0071] The plurality of conductor posts 15b are obtained by forming a conductor film on the inner wall of a through hole that penetrates the main surfaces of the substrate 15a or filling the through hole with a conductor. The center interval between adjacent conductor posts among the plurality of conductor posts 15b can be appropriately determined, but it is preferably determined to be capable of reflecting electromagnetic waves belonging to a specified passband (for example, the 25 GHz band). The plurality of conductor posts arranged at such a center interval function as column walls and function in the same way as the side walls of the shield 14.

[0072] In addition, in the filter device 1D, a bump 16 is used as a connection component for fixing the plurality of conductor posts 15b to the strip conductor 12d. However, the connection component is not limited to the bump 16, and it can also be solder or solder balls.

[0073] <Other aspects of the present invention>

[0074] In the present embodiment, the filter device 1 as one aspect of the present invention has been described. However, one aspect of the present invention is not limited to the filter device 1. That is, the present invention includes within the scope of the invention each structure of the filter device 1 described below.

[0075] A transmission line as one aspect of the present invention is configured to Figure 1The transmission line of a part of the filter device 1 shown includes: a dielectric substrate 11 including a pair of opposed first main surface 111 and second main surface 112; a strip conductor provided on the first main surface 111 (here, strip conductor 12a2); and a ground conductor layer 13 provided at least on the second main surface 112. In this transmission path, one or more recesses (here, recess 11a2) are formed on the second main surface 112. The one or more recesses overlap the strip conductor 12a2 in a top view, and the surface is covered by the second ground conductor layer 132 of the ground conductor layer 13. This transmission line is a microstrip type transmission line. According to this structure, compared with a microstrip type transmission line composed of a substrate without one or more recesses, a strip conductor, and a ground conductor layer, the interval between the strip conductor and the ground conductor layer can be reduced. Therefore, the width of the strip conductor can be narrowed, and thus, in the case of along the width direction of the strip conductor, the transmission line can be miniaturized. In addition, in the case of arranging a plurality of microstrip type transmission lines in parallel, by using such a microstrip type transmission line as each transmission line, the interval between the strip conductors in adjacent transmission lines can be narrowed.

[0076] In addition, this transmission line functions as a resonator having a resonance frequency determined according to the length of the strip conductor 12a2. Therefore, within the scope of the present invention, there is included a resonator including: a dielectric substrate 11 including a pair of opposed first main surface 111 and second main surface 112; a strip conductor provided on the first main surface 111 (here, strip conductor 12a2); and a ground conductor layer 13 provided at least on the second main surface 112. One or more recesses (here, recess 11a2) are formed on the second main surface 112. The one or more recesses overlap the strip conductor 12a1 in a top view, and the surface is covered by the second ground conductor layer 132 of the ground conductor layer 13. According to this configuration, compared with a microstrip type resonator composed of a substrate without one or more recesses, a strip conductor, and a ground conductor layer, the interval between the strip conductor and the ground conductor layer can be reduced. Therefore, the width of the strip conductor can be narrowed, and thus, in the case of along the width direction of the strip conductor, the resonator can be miniaturized. In addition, in the case of arranging a plurality of microstrip type resonators substantially in parallel, by using such a microstrip type resonator as each resonator, the interval between the strip conductors of adjacent resonators can be narrowed.

[0077] In addition, the transmission line group as one aspect of the present invention constitutes Figure 1The transmission line group that is a part of the filter device 1 shown includes: a dielectric substrate 11 including opposed first main surface 111 and second main surface 112; a plurality of adjacent strip conductors (here strip conductors 12a2 and 12a3) provided on the first main surface 111; and a ground conductor layer 13 provided at least on the second main surface 112. For each of the plurality of strip conductors (here strip conductors 12a2 and 12a3), one or more recesses (here recesses 11a2 and 11a3) are formed on the second main surface 112. The one or more recesses overlap with the strip conductor 12a2 in a plan view, and the surface is covered by the second ground conductor layer 132 of the ground conductor layer 13.

[0078] In addition, this transmission line group functions as a resonator group having a resonance frequency determined according to the lengths of the strip conductors 12a2 and 12a3. Therefore, within the scope of the present invention, there is included a resonator group including: a dielectric substrate 11 including opposed first main surface 111 and second main surface 112; a plurality of adjacent strip conductors (here strip conductors 12a2 and 12a3) provided on the first main surface 111; and a ground conductor layer 13 provided at least on the second main surface 112. For each of the plurality of strip conductors (here strip conductors 12a2 and 12a3), one or more recesses (here recesses 11a2 and 11a3) are formed on the second main surface 112. The one or more recesses overlap with the strip conductor 12a2 in a plan view, and the surface is covered by the second ground conductor layer 132 of the ground conductor layer 13.

[0079] In addition, one aspect of the present invention is not limited to the transmission lines, resonators, transmission line groups, and resonator groups that are a part of the filter device 1, and may also be the transmission lines, resonators, transmission line groups, and resonator groups that are a part of the filter devices 1A and 1B, and the filter devices 2 and 2A described later.

[0080] 〔Second Embodiment〕

[0081] Refer to Figure 6 The filter device 2 of the second embodiment of the present invention will be described. Figure 6 (a) is a plan view of the filter device 2. Figure 6 (b) of Figure 6 (c) of Figure 6 (b) is a cross-sectional view taken along the Figure 6 A-A' line shown in (a) of Figure 6 (c) is a cross-sectional view taken along the Figure 6 B-B' line shown in (a) of

[0082] <Structure of Filter Device>

[0083] As shown in Figure 6 (a) to (c) of the filter device 2 includes a substrate 21, a conductor pattern 22, and a ground conductor layer 23. The substrate 21, the conductor pattern 22, and the ground conductor layer 23 of the filter device 2 respectively correspond to the substrate 11, the conductor pattern 12, and the ground conductor layer 13 of the filter device 1. Therefore, hereinafter, the structure of the filter device 2 that is different from the filter device 1 will be described, and the description of the structure common to the filter device 1 will be omitted.

[0084] (Substrate)

[0085] Similar to the substrate 11, the substrate 21 is a plate-like member made of a dielectric including opposing main surfaces 211 and 212. The main surfaces 211 and 212 respectively correspond to the main surfaces 111 and 112 of the substrate 11.

[0086] In the present embodiment, the conductor pattern 22 described later is provided on the main surface 211, and the recesses 21a1 to 21a5 and the ground conductor layer 23 described later are provided on the main surface 212. However, the conductor pattern 22 may be indirectly provided on the main surface 211 side of the substrate 21, and the ground conductor layer 23 may be indirectly provided on the main surface 212 side of the substrate 21. For example, at least one of a layer with low conductivity (such as a dielectric layer) may be interposed between the main surface 211 and the conductor pattern 22 and between the main surface 212 and the ground conductor layer 23. In addition, the conductor posts 21b1 to 21b5 described later are provided inside the substrate 21.

[0087] (Conductor Pattern)

[0088] Similar to the conductor pattern 12, the conductor pattern 22 provided on the main surface 211 is obtained by patterning a conductor film into a specified shape. The conductor pattern 22 includes strip conductors 22a1 to 22a5, coplanar lines 22b, and coplanar lines 22c.

[0089] The strip conductors 22a1 to 22a5 are configured to be the same as the strip conductors 12a1 to 12a5 of the filter device 1. However, compared with each strip conductor 12ai of the filter device 1, each strip conductor 22ai is configured to have a length shortened by the thickness of the substrate 21. This is for each conductor post 21bi described later to function as a signal line of a double-conductor line together with each strip conductor 22ai.

[0090] Since the coplanar lines 22b and 22c are the same as the coplanar lines 12b and 12c of the filter device 1, their description is omitted.

[0091] (Recess)

[0092] The recesses 21a1 to 21a5 provided on the main surface 212 are configured to be the same as the recesses 11a1 to 11a5 of the filter device 1 respectively. Accordingly, each recess 21ai corresponds to each opposed strip conductor 22ai. However, each recess 21ai is configured to have a shorter length compared to each recess 11ai of the filter device 1. Therefore, in the filter device 2, one end portion of each strip conductor 22ai protrudes from the recess 21ai that overlaps with the 22ai in a plan view (see Figure 6 in (a) and Figure 6 in (c)).

[0093] In addition, when observing along the length direction of each strip conductor 22ai (see Figure 6 in (c)), the positions where the recesses 21ai are provided are determined such that the intervals between each conductor post 21bi described later and the second ground conductor layer 232 close to each conductor post 21bi and the intervals between each strip conductor 22ai and the bottom surfaces of the recesses 21ai are of the same degree. More specifically, the positions where the recesses 21ai are provided are determined such that the coupling amounts generated between each conductor post 21bi and the second ground conductor layer 232 (the second ground conductor layer 232 covering the side surface on the side of the conductor post 21bi in the side surface of the recess 21ai) close to the conductor post 21bi and the coupling amounts generated between each strip conductor 22ai and the second ground conductor layer 232 provided on the bottom surface of each recess 21ai are of the same degree.

[0094] In the present embodiment, the shape of each recess 21ai is a rectangular parallelepiped shape. However, similar to the shape of each recess 11ai, the shape of each recess 21ai can be appropriately determined. The shape of each recess 21ai may be the same as that of each recess 11ai of the filter device 1A, or may be the same as that of each recess 11ai of the filter device 1B.

[0095] (Ground Conductor Layer)

[0096] As shown in Figure 6 in (b) and Figure 6 in (c), similar to the ground conductor layer 13, the ground conductor layer 23 is composed of a first ground conductor layer 231 and a second ground conductor layer 232. The first ground conductor layer 231 corresponds to the first ground conductor layer 131 of the ground conductor layer 13, and the second ground conductor layer 232 corresponds to the second ground conductor layer 132 of the ground conductor layer 13. The first ground conductor layer 231 in the ground conductor layer 23 refers to the portion provided on the main surface 212, and the second ground conductor layer 232 refers to the portion covering the surfaces of the recesses 21ai.

[0097] (Conductor Post)

[0098] Similar to each conductor post 11b1 to 11b5 of the filter device 1, each conductor post 21b1 to 21b5 corresponds to each strip conductor 22a1 to 22a5 respectively. Each conductor post 21bi corresponding to each strip conductor 22ai is disposed at one end of each strip conductor 22ai and in a region where one end protruding from each recess 21ai overlaps with a first ground conductor layer 231 to be described later when observing the main surface 211 from above. Each conductor post 21bi shorts the above-mentioned one end to the first ground conductor layer 231. Each conductor post 21bi has a prescribed coupling amount with a second ground conductor layer 232 close to the conductor post 21bi, and thus forms a two-conductor line together with the second ground conductor layer 232.

[0099] In the filter device 2 like this, in addition to each strip conductor 22ai, each conductor post 21bi also functions as a signal line of the two-conductor line. Therefore, the length of each strip conductor 22ai can be made shorter by the thickness of the substrate 21 than the length of each strip conductor 12ai of the filter device 1.

[0100] In addition, in the present embodiment, each conductor post 21bi is composed of 4 conductor posts. However, the number of conductor posts constituting each conductor post 21bi is not limited. In addition, in order to reduce the difference between the width of each strip conductor 22ai and the effective width of each conductor post 21bi, (1) when the conductor posts constituting each conductor post 21bi are separated from each other, the total value of the diameters of the conductor posts constituting each conductor post 21bi is preferably close to the width of each strip conductor 22ai, and (2) when the conductor posts constituting each conductor post 21bi are integrated with each other, the width of each conductor post 21bi (the length of each conductor post 21bi along the width direction of each strip conductor 22ai) is preferably close to the width of each strip conductor 22ai.

[0101] <Modification Example>

[0102] Refer to Figure 7 Regarding Figure 6 A filter device 2A as a modification example of the filter device 2 shown will be described. Figure 7 It is an enlarged top view of one end of a strip conductor 22a3 which is one of the strip conductors included in the filter device 2A. In addition, for ease of explanation, in the filter device 2A, components having the same functions as those described with the filter device 2 are denoted by the same reference numerals, and their descriptions are not repeated.

[0103] The filter device 2A is obtained by changing the shape of each conductor post 21bi based on the filter device 2. In Figure 7Among them, the conductor post 21b3 is shown as an example of each conductor post 21bi, but the other conductor posts 21b1, 21b2, 21b4, and 21b5 are also configured to be the same as the conductor post 21b3.

[0104] Specifically, each conductor post 21bi of the filter device 2 is composed of four conductor posts with a circular cross-sectional shape. In contrast, each conductor post 21bi of the filter device 2A is composed of eight conductor posts with a circular cross-sectional shape, and the center-to-center distance between adjacent conductor posts is configured to be narrower than the diameter of each conductor post. As a result, when viewed in the width direction of each strip conductor 22ai, the width of each conductor post 21bi of the filter device 2A is of the same degree as the width of each strip conductor 22ai.

[0105] In addition, in the present embodiment, the width of each conductor post 21bi is 92.5% of the width of each strip conductor 22ai. However, the width of each conductor post 21bi is not limited thereto. In addition, in order to improve the continuity between each strip conductor 22ai and each conductor post 21bi, the ratio of the width of each conductor post 21bi to the width of each strip conductor 22ai is preferably 80% or more and 120% or less.

[0106] 〔Example〕

[0107] Refer to Figure 8 and Figure 9 A comparison between the filter device 1E as an example of the present invention and the comparative example of the filter device 1 will be described. Figure 8 is a top view of the filter device 1E. Figure 9 is a graph showing the results obtained by simulating the frequency dependence of the transmission intensity of the filter device 1E, the first comparative example, and the second comparative example. In addition, hereinafter, the frequency dependence of the transmission intensity will be referred to as the transmission characteristic.

[0108] The filter device 1E is Figure 3 a modified example of the filter device 1B shown. The filter device 1E is obtained by changing each recess 11ai from a recess that looks like the letter E in a top view to two independent recesses, namely recesses 11ai1 and 11ai2, based on the filter device 1B. The shapes of the recesses 11ai1 and 11ai2 are both rectangular parallelepiped. In addition, the fourth recess 11ai4 provided in each recess 11ai of the filter device 1B is omitted in each recess 11ai of the filter device 1E. In addition, the lengths of the recesses 11ai1 and 11ai2 are the same as the lengths of the respective strip conductors 12ai.

[0109] In this embodiment, in the filter device 1E, the following design parameters are adopted. That is, quartz glass is used as the dielectric constituting the substrate 11, its relative dielectric constant is 3.82, and the thickness of the substrate 11 is 400 μm. In addition, as the length and width of each strip conductor 12ai, 1550 μm and 350 μm are respectively adopted. In addition, as the interval between the central axes of adjacent strip conductors 12ai, 700 μm is adopted. In addition, as the length, width, and depth of the recesses 11ai1 and 11ai2 constituting each recess 11ai, 1550 μm, 100 μm, and 250 μm are respectively adopted.

[0110] In addition, the recesses 11ai are omitted from the filter device of the first comparative example in the filter device 1. Therefore, in the first comparative example, the main surface 112 is composed of a flat surface, and the ground conductor layer 13 is composed only of the first ground conductor layer 131. Among the multiple strip conductors included in the filter device of the first comparative example, adjacent strip conductors are arranged as in Figure 4 that of Patent Document 1. In addition, the filter of the second comparative example is obtained by providing recesses in the region between adjacent strip conductors in the region of the main surface 111 where the strip conductors 12ai are not provided, based on the filter device of the first comparative example. The filter device of the second comparative example corresponds to the filter device shown in Figure 1 Patent Document 1.

[0111] As in the filter device 1 and the filter devices of the comparative examples, in a structure where multiple strip conductors each function as a resonator and adjacent strip conductors are electromagnetically coupled to each other, the coupling coefficient k between the resonators is known to be represented by Equation (1).

[0112] [Equation 1]

[0113]

[0114] Here, the coupling coefficient k is an index indicating the strength of the coupling between the resonators. The larger the coupling coefficient k, the stronger the coupling between the resonators. In Equation (1), f h is the resonance frequency on the side with the larger frequency, and f l is the resonance frequency on the side with the smaller frequency.

[0115] According to Figure 9The coupling coefficients k obtained from the transmission characteristics of the illustrated embodiment, the first comparative example, and the second comparative example are 0.0854, 0.184, and 0.149, respectively. Therefore, in the case of designing such that the magnitude of the coupling generated between adjacent strip conductors 12ai is the same as that of the filter devices of the comparative examples, it is known that the filter device 1E of the embodiment can reduce the interval between adjacent strip conductors 12ai compared to the filter devices of the first comparative example and the second comparative example, respectively. That is, it is known that the filter device 1E can be miniaturized compared to the filter devices of the first comparative example and the second comparative example, respectively.

[0116] 〔Summary〕

[0117] The filter device of the first aspect of the present invention includes: a dielectric substrate including a first main surface and a second main surface opposed to each other; a plurality of strip conductors provided on the first main surface side and electromagnetically coupled to each other; and a ground conductor layer provided at least on the second main surface side. For each of the plurality of strip conductors, one or more recesses are formed on the second main surface of the substrate, and the one or more recesses overlap with the strip conductor in a top view and the surface is covered with the ground conductor layer.

[0118] According to the above structure, compared with a filter device in which no recess is provided in the substrate (for example, the filter device described in Patent Document 1 Figure 3 ), in the case of designing such that the magnitude of the coupling generated between adjacent strip conductors is the same as that in the past, the interval between adjacent strip conductors can be reduced, and thus the filter device can be miniaturized. This is because, compared with a filter device in which no recess is provided in the substrate, since the interval between each of the plurality of strip conductors and the ground conductor layer closest to each strip conductor becomes narrower, the power lines generated between the strip conductor and the ground conductor layer are concentrated in the normal direction of the first main surface and are not easily extended in the in-plane direction of the first main surface.

[0119] In addition, the filter device of the second aspect of the present invention is based on the structure of the filter device of the first aspect described above and adopts the following structure: when viewed in the direction along the respective extending directions (i.e., the length directions) of the plurality of strip conductors, the length of each of the recesses is greater than the length of the strip conductor overlapping with the recess in a top view and the recess includes the strip conductor.

[0120] According to the above structure, the ground conductor layer provided on the bottom surface of the recess has a sufficient size as the ground conductor layer constituting the microstrip line.

[0121] In addition, on the basis of the structure of the filter device according to the first or second mode of the present invention, the filter device according to the third mode of the present invention adopts the following structure: for each of the plurality of strip conductors, a plurality of recesses are formed on the second main surface of the substrate, the plurality of recesses overlap with the strip conductor in a top view, and the surface is covered by the ground conductor layer.

[0122] According to the above structure, the volume of the recess provided on the substrate can be reduced, so that the number of processes, time, etc. required for forming the recess can be reduced.

[0123] In addition, on the basis of the structure of the filter device according to any one of the first to third modes of the present invention, the filter device according to the fourth mode of the present invention adopts the following structure: for each of the plurality of strip conductors, one or more conductor posts are further provided, the one or more conductor posts are provided in a region where the strip conductor overlaps with the recess in a top view, and the strip conductor is short-circuited to the ground conductor layer.

[0124] According to the above structure, since the strip conductor and the recess can be short-circuited by a short conductor post, a single-ended short-strip resonator that can suppress reactance to the minimum can be realized.

[0125] In addition, on the basis of the structure of the filter device according to the fourth mode of the present invention, the filter device according to the fifth mode of the present invention adopts the following structure: in a top view, the one or more conductor posts are provided in a region overlapping with the recess, and the distance between the region of the bottom surface of the recess including the one or more conductor posts and the first main surface is constant.

[0126] According to the above structure, one or more conductor posts are only short-circuited to the ground conductor layer on the bottom surface of the recess, so that the shape of one or more conductor posts can be simplified. In addition, the length of each of the one or more conductor posts can be made constant.

[0127] In addition, on the basis of the structure of the filter device according to the first mode of the present invention, the filter device according to the sixth mode of the present invention adopts the following structure: the ground conductor layer provided on the second main surface is used as the first ground conductor layer, the ground conductor layer covering the surface of the one or more recesses is used as the second ground conductor layer, for each of the plurality of strip conductors, one end of the strip conductor protrudes from the recess overlapping with the strip conductor in a top view, for each of the plurality of strip conductors, one or more conductor posts are further provided, the one or more conductor posts are provided in a region where the one end overlaps with the first ground conductor layer in a top view, and the one end is short-circuited to the first ground conductor layer, and the one or more conductor posts and the second ground conductor layer covering the side surface of the recess in the second ground conductor layer together form a two-conductor line.

[0128] Based on the above structure, while each strip conductor and the second ground conductor layer provided on the bottom surface of the recess function as a two-conductor line, one or more conductor pillars and the second ground conductor layer provided on the side surface of the recess also function as a two-conductor line. Therefore, the filter device according to the sixth aspect can shorten the length in the length direction of each strip conductor, and thus can miniaturize the filter device also in the length direction.

[0129] In addition, the filter device according to the seventh aspect of the present invention is based on the structure of the filter device according to the sixth aspect described above, and adopts the following structure: for each of the plurality of strip conductors, when viewed in the direction intersecting the extending direction of the strip conductor, that is, in the width direction, the width of the one or more conductor pillars is about the same as the width of the strip conductor.

[0130] Based on the above structure, it is possible to reduce the discontinuity that may occur at the connection point between the strip conductor functioning as a signal line of the two-conductor line and the conductor pillar, and thus it is possible to improve the functionality of the two-conductor line.

[0131] In addition, the filter device according to the eighth aspect of the present invention is based on the structure of the filter device according to any one of the first to eighth aspects described above, and adopts the following structure: it further includes a metal shield, which is separated from the plurality of strip conductors and covers the plurality of strip conductors.

[0132] Based on the above structure, even when a metal object approaches the plurality of strip conductors from the first main surface side, the shield can shield the plurality of strip conductors from the metal object. Therefore, it is possible to suppress fluctuations in the filter characteristics that may occur in such a case.

[0133] 〔Additional matters〕

[0134] The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims. Embodiments obtained by appropriately combining technical means separately disclosed in different embodiments are also included in the technical scope of the present invention.

[0135] Description of reference numerals

[0136] 1. 2... filter device; 11, 21... substrate; 111, 211... main surface (first main surface); 112, 212... main surface (second main surface); 11a1 to 11a5, 21a1 to 21a5... concave portion; 11b1 to 11b5, 11c1 to 11c4, 21b1 to 21b5, 21c1 to 21c4... conductor post; 12, 22... conductor pattern; 12a1 to 12a5, 22a1 to 22a5... strip conductor; 12b, 12c, 22b, 22c... coplanar line; 12b1, 12c1, 22b1, 22c1... signal line; 12b2, 12b3, 12c2, 12c3, 22b2, 22b3, 22c2, 22c3... ground conductor pattern; 13, 23... ground conductor layer; 131, 231... first ground conductor layer; 132, 232... second ground conductor layer.

Claims

1. A filter device, characterized in that, Comprising: A dielectric substrate including opposed first and second main surfaces; A plurality of strip conductors disposed on the first main surface side, and adjacent strip conductors being electromagnetically coupled to each other; And A ground conductor layer disposed at least on the second main surface side, For each of the plurality of strip conductors, one or more recesses are formed in the second main surface of the substrate, the one or more recesses overlapping with the strip conductor in a plan view, and the surface being covered by the ground conductor layer, When viewed in the plan view along the extending direction, i.e., the length direction, of each of the plurality of strip conductors, the length of each of the recesses is greater than the length of the strip conductor overlapping with the recess in the plan view and the recess includes the strip conductor.

2. The filter device according to claim 1, wherein: For each of the plurality of strip conductors, one or more conductor posts are further provided, the one or more conductor posts being disposed in a region where the strip conductor overlaps with the recess in the plan view and short-circuiting the strip conductor to the ground conductor layer.

3. A filter device, characterized in that, Comprising: A dielectric substrate including opposed first and second main surfaces; A plurality of strip conductors disposed on the first main surface side, and adjacent strip conductors being electromagnetically coupled to each other; And A ground conductor layer disposed at least on the second main surface side, For each of the plurality of strip conductors, one or more recesses are formed in the second main surface of the substrate, the one or more recesses overlapping with the strip conductor in a plan view, and the surface being covered by the ground conductor layer, The ground conductor layer is composed of a first ground conductor layer and a second ground conductor layer, the first ground conductor layer being disposed on the second main surface, and the second ground conductor layer covering the surface of the one or more recesses, For each of the plurality of strip conductors, one end of the strip conductor protrudes from the recess overlapping with the strip conductor in the plan view, For each of the plurality of strip conductors, one or more conductor posts are further provided, the one or more conductor posts being disposed in a region where the one end overlaps with the first ground conductor layer in the plan view and short-circuiting the one end to the first ground conductor layer, and the one or more conductor posts and the second ground conductor layer covering the side surface of the recess in the second ground conductor layer together form a two-conductor line.

4. The filter device according to claim 1, wherein: A metal shield is further provided, the shield being separated from the plurality of strip conductors and covering the plurality of strip conductors.

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