Multilayer band-pass filter

Abstract

The present invention provides a multilayer band-pass filter that includes at least one LC resonator inside a laminate in which a plurality of dielectric layers are stacked. The LC resonator includes a capacitor conductor pattern, a line conductor pattern, and a GND conductor pattern disposed on the surface of one of the plurality of dielectric layers, and first and second interlayer connecting conductors extending in the stacking direction. The capacitor conductor pattern and the line conductor pattern are connected by the first interlayer connecting conductor. The line conductor pattern and the GND conductor pattern are connected by the second interlayer connecting conductor. Provided that the "via length" is defined to be the length of the first interlayer connecting conductor in relation to the stacking direction and the "line length" is defined to be the length of the gap between the first interlayer connecting conductor and the second interlayer connecting conductor, the via length is greater than the line length.

Description

Multilayer Bandpass Filter

[0001] The present invention relates to a multilayer bandpass filter.

[0002] An example of a multilayer bandpass filter is described in Japanese Patent No. 6369638 (Patent Document 1).

[0003] The invention described in Patent Document 1 has been adopted as a method for efficiently ensuring a coil L value and achieving a good Q value in a limited space by taking advantage of the characteristics of the process for multilayer electronic components. Generally, a closed-loop coil configured in a rectangular shape, i.e., a helical coil, can achieve a good Q value as the magnetic flux path is ensured. Therefore, it is considered preferable to make the length of each side 1:1.

[0004] Patent No. 6369638

[0005] As described in Patent Document 1, an LC resonator is known. The LC resonator includes a coil portion and a capacitance portion. The coil portion is formed by two interlayer connection conductors and a conductor pattern connecting the interlayer connection conductors. The capacitance portion is formed by a portion of a GND conductor pattern and a conductor pattern facing the GND conductor pattern. In such LC resonators, the length of the interlayer connection conductors has been designed to be shorter than the conductor pattern connecting the interlayer connection conductors, due to actual product space constraints, the risk of structural defects due to longer interlayer connection conductors, and avoidance of cost increases.

[0006] Interlayer connection conductors often have a circular cross section, which results in low transmission loss. On the other hand, the conductor patterns connecting the interlayer connection conductors are formed by screen printing or the like, and therefore have a cross section that is rectangular with a small thickness relative to the width or a rectangular shape with tapered ends, which results in relatively high transmission loss.

[0007] With regard to the GND conductor pattern and the capacitance section, not only is the film thickness reduced as a countermeasure against structural defects, but in some cases additives such as glass or ceramic are mixed in to suppress shrinkage, and the loss associated with the stray L component of the capacitance section cannot be ignored.

[0008] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a multilayer bandpass filter that can reduce loss and achieve a good Q value.

[0009] To achieve the above object, a multilayer bandpass filter according to the present invention is a multilayer bandpass filter including at least one LC resonator inside a laminate formed by stacking multiple dielectric layers. The LC resonator has a loop shape with its winding axis arranged inside the laminate so as to be perpendicular to the stacking direction of the laminate. The LC resonator includes a capacitor conductor pattern, a line conductor pattern, and a GND conductor pattern arranged on any surface of the multiple dielectric layers, and a first interlayer connection conductor and a second interlayer connection conductor extending in the stacking direction. The capacitor conductor pattern and the line conductor pattern are connected by the first interlayer connection conductor. The line conductor pattern and the GND conductor pattern are connected by the second interlayer connection conductor. The LC resonator includes a capacitive portion in which at least a portion of the capacitor conductor pattern and at least a portion of the GND conductor pattern face each other to form a capacitance. The capacitor conductor pattern and the GND conductor pattern are arranged on different layers. If the length of the first interlayer connection conductor in the stacking direction is defined as the "via length" and the length of the gap between the first interlayer connection conductor and the second interlayer connection conductor is defined as the "line length," then the via length is longer than the line length.

[0010] According to the present invention, since the via length is longer than the line length, the electrical resistance can be kept low within one loop of the LC resonator, thereby reducing loss and achieving a good Q value.

[0011] 3 is a perspective view of a multilayer bandpass filter according to a first embodiment of the present invention; FIG. 4 is a perspective view showing only a structure formed of conductors of an LC resonator included in the multilayer bandpass filter according to the first embodiment of the present invention; FIG. 5 is a view showing the LC resonator included in the multilayer bandpass filter according to the first embodiment of the present invention as viewed from the direction of the winding axis; FIG. 6 is a cross-sectional view taken along line IV-IV in FIG. 3; FIG. 7 is a cross-sectional view taken along line V-V in FIG. 3; FIG. 8 is a cross-sectional view of an example of a line conductor pattern included in the multilayer bandpass filter according to the first embodiment of the present invention; FIG. 9 is a cross-sectional view of the multilayer bandpass filter according to the first embodiment of the present invention; FIG. 10 is a cross-sectional view of a multilayer bandpass filter according to a second embodiment of the present invention; and FIG. 11 is a graph showing the results of determining the Q value when the line length L1 and the via length L2 are variously changed.

[0012] The dimensional ratios shown in the drawings do not necessarily represent the actual ratios, and may be exaggerated for the sake of convenience. In the following description, when the concepts of up and down are mentioned, they do not necessarily mean absolute up and down, but may mean relative up and down in the illustrated position.

[0013] First Embodiment A multilayer bandpass filter according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 7 . FIG. 1 shows the external appearance of a multilayer bandpass filter 101 according to this embodiment. The multilayer bandpass filter 101 includes a laminate 1. The laminate 1 is fabricated by stacking and integrating multiple dielectric layers 2. In FIG. 1 , the multilayer bandpass filter 101 is shown with a stacking direction 90 aligned vertically. Although FIG. 1 shows the boundaries between the dielectric layers 2, in reality, the boundaries are not necessarily visually recognizable. Although FIG. 1 does not show the external terminals of the multilayer bandpass filter 101, multiple external terminals are actually arranged on one surface of the laminate 1. The multiple external terminals may be arranged, for example, in the form of pad electrodes on the lower surface of the laminate 1.

[0014] The multilayer bandpass filter 101 incorporates one or more LC resonators. FIG. 2 shows a perspective view of one LC resonator 20 incorporated in the multilayer bandpass filter 101. In FIG. 2, the dielectric layer 2 that fills the periphery of the LC resonator 20 has been removed, showing only the structure formed by the conductor. Although FIG. 2 shows only one LC resonator 20, in reality, multiple LC resonators 20 may be arranged side by side. A GND conductor film 10 is disposed below. In FIG. 2, a winding axis 93 is indicated by a dashed line.

[0015] Fig. 3 shows LC resonator 20 as viewed from the direction of winding axis 93. Fig. 4 shows a cross-sectional view taken along line IV-IV in Fig. 3. Fig. 5 shows a cross-sectional view taken along line V-V in Fig. 3.

[0016] The multilayer bandpass filter 101 is a multilayer bandpass filter including at least one LC resonator 20 inside a laminate 1 formed by stacking multiple dielectric layers 2. The LC resonator 20 has a loop shape with a winding axis 93 disposed inside the laminate 1 perpendicular to a stacking direction 90 of the laminate 1. The LC resonator 20 includes a capacitor conductor pattern 81, a line conductor pattern 82, and a GND conductor pattern 83 disposed on any surface of the multiple dielectric layers 2. The LC resonator 20 includes a first interlayer connection conductor 61 and a second interlayer connection conductor 62 extending in the stacking direction 90. The capacitor conductor pattern 81 and the line conductor pattern 82 are connected by the first interlayer connection conductor 61. The line conductor pattern 82 and the GND conductor pattern 83 are connected by the second interlayer connection conductor 62. The LC resonator 20 includes a capacitive portion 3 in which at least a portion of the capacitor conductor pattern 81 and at least a portion of the GND conductor pattern 83 face each other to form a capacitance. The capacitor conductor pattern 81 and the GND conductor pattern 83 are arranged on different layers.

[0017] The GND conductor pattern 83 may be an individual, independent conductor pattern, but is not limited to an individual, independent conductor pattern, and may be configured such that a portion of the wide GND conductor film 10 is regarded as the GND conductor pattern 83. In the example shown in Fig. 2, there is one wide GND conductor film 10 that is common to multiple LC resonators 20, and several regions of this GND conductor film 10 serve as GND conductor patterns 83 for each LC resonator 20. In Fig. 2, the area corresponding to one GND conductor pattern 83 is virtually indicated by a two-dot chain line.

[0018] The cross-sectional shape of the first interlayer connection conductor 61 is circular, as shown in Fig. 4 . The cross-sectional shape of the second interlayer connection conductor 62 is also circular. The cross-sectional shape of the line conductor pattern 82 may be rectangular, as shown in Fig. 5 . However, the cross-sectional shape of the line conductor pattern 82 may also be a shape in which the areas near both ends become thinner as they approach the ends, as shown in Fig. 6 . The same applies to the cross-sectional shape of the capacitor conductor pattern 81. The same also applies to the cross-sectional shape of the GND conductor pattern 83 when the GND conductor pattern 83 is an individual, independent conductor pattern.

[0019] If the length of the first interlayer connection conductor 61 in the stacking direction 90 is defined as the "via length" and the length of the gap between the first interlayer connection conductor 61 and the second interlayer connection conductor 62 is defined as the "line length," then the via length is longer than the line length. In the example shown in FIG. 7 , the line length is L1 and the via length is L2. In this case, L2 > L1. In the example shown in FIG. 7 , the shape of the LC resonator 20 is vertically long, but the external shape of the laminate 1 is horizontally long.

[0020] As shown in FIG. 4 , the first interlayer connection conductor 61 and the second interlayer connection conductor 62, which have a circular cross-sectional shape, have a larger cross-sectional area and a longer outer periphery than the line conductor pattern 82, which has a cross-sectional shape as shown in FIG. 5 or 6 . Furthermore, because the first interlayer connection conductor 61 and the second interlayer connection conductor 62 have a circular cross-sectional shape, they are less susceptible to the edge effect. These factors contribute to lower electrical resistance of the first interlayer connection conductor 61 and the second interlayer connection conductor 62 than the line conductor pattern 82. In this embodiment, the via length L2 is longer than the line length L1, so that electrical resistance can be kept low within one loop of the LC resonator 20, thereby achieving a favorable Q value for the resonator. In other words, the multilayer bandpass filter 101 according to this embodiment can reduce loss and achieve a favorable Q value.

[0021] Second Embodiment With reference to FIG. 8, a multilayer bandpass filter according to a second embodiment of the present invention will be described.

[0022] 8 , in the multilayer bandpass filter 102, the length of the laminate 1 in the lamination direction 90 is longer than the length along the longitudinal direction of the line conductor pattern 82 of the laminate 1. The configuration of other parts is the same as that described in the first embodiment. That is, in the multilayer bandpass filter 102, the shape of the LC resonator 20 is vertically long, and the outer shape of the laminate 1 is also vertically long.

[0023] In this embodiment, the laminate 1 has a vertically long shape, which reduces the area required to mount the multilayer bandpass filter 102. The vertically long shapes of both the laminate 1 and the LC resonator 20 can improve the characteristics per volume.

[0024] Using the multilayer bandpass filter 101 shown in the first embodiment as an example, we investigated what would be particularly preferable for the line length L1 and via length L2 shown in FIG. 7. As shown in Table 1, the values ​​of L1 and L2 were changed to simulate samples under conditions 1 to 8, and the Q value was calculated for each by simulation. Condition 1 is the same as the conventional condition. Under condition 2, L1 = L2, and the shape of the LC resonator 20 is approximately square.

[0025]

[0026] FIG. 9 shows a graph of the results of determining the Q value under each of conditions 1 to 8. In FIG. 9, the vertical axis represents L2 / L1, and the horizontal axis represents the Q value. The larger the Q value, the more preferable it is. As shown in FIG. 9, the Q value is particularly large in region Z. This region Z corresponds to the range where L2 / L1 is 1.1 or more and 2.1 or less.

[0027] From the above, it can be said that in the multilayer bandpass filter, it is preferable that the value obtained by dividing the via length L2 by the line length L1 is 1.1 or more and 2.1 or less.

[0028] When forming the capacitance section 3, it is possible to suppress sintering by adding a non-metallic additive to at least one of the capacitor conductor pattern 81 and the GND conductor pattern 83. Examples of non-metallic additives include glass components and ceramic components. One of the drawbacks of suppressing sintering in this way is a deterioration in the Q value of the stray L component of the capacitance section 3. By reducing the line length L1, the L component in the capacitance section 3 can be reduced, thereby improving the Q value of the LC resonator 20. In the capacitance section 3, it is preferable that the capacitor conductor pattern 81 and the GND conductor pattern 83 contain a non-metallic additive. By adopting this configuration, the benefit of an improved Q value can be more typically enjoyed.

[0029] It should be noted that a plurality of the above-described embodiments may be appropriately combined and employed. The above-described embodiments disclosed herein are illustrative in all respects and are not limiting. The scope of the present invention is defined by the claims, and includes all modifications within the meaning and scope of the claims.

[0030] (Supplementary Notes) (Supplementary Note 1) A multilayer bandpass filter including at least one LC resonator inside a laminate formed by stacking a plurality of dielectric layers, wherein the LC resonator has a loop shape arranged such that a winding axis is perpendicular to a stacking direction of the laminate inside the laminate, the LC resonator includes a capacitor conductor pattern, a line conductor pattern, and a GND conductor pattern arranged on the surfaces of any of the plurality of dielectric layers, and a first interlayer connection conductor and a second interlayer connection conductor extending in the stacking direction, the capacitor conductor pattern and the line conductor pattern are connected by the first interlayer connection conductor, and the line conductor pattern and the GND conductor pattern are connected by the second interlayer connection conductor, the LC resonator includes a capacitive portion in which at least a part of the capacitor conductor pattern and at least a part of the GND conductor pattern face each other to form a capacitance, the capacitor conductor pattern and the GND conductor pattern are arranged on different layers, A multilayer bandpass filter, wherein the length of the first interlayer connection conductor in the stacking direction is defined as the "via length" and the length of the gap between the first interlayer connection conductor and the second interlayer connection conductor is defined as the "line length", and the via length is longer than the line length.

[0031] (Supplementary Note 2) The multilayer bandpass filter according to Supplementary Note 1, wherein a value obtained by dividing the via length by the line length is 1.1 or more and 2.1 or less.

[0032] (Supplementary Note 3) The multilayer bandpass filter according to Supplementary Note 1 or 2, wherein in the capacitive section, the capacitor conductor pattern and the GND conductor pattern contain a non-metallic additive.

[0033] (Supplementary Note 4) The multilayer bandpass filter according to any one of Supplementary Notes 1 to 3, wherein a length of the laminate in the lamination direction is longer than a length of the laminate along the longitudinal direction of the line conductor pattern.

[0034] REFERENCE SIGNS LIST 1 laminate, 2 dielectric layer, 3 capacitance portion, 10 GND conductor film, 20 LC resonator, 61 first interlayer connection conductor, 62 second interlayer connection conductor, 81 capacitor conductor pattern, 82 line conductor pattern, 83 GND conductor pattern, 90 lamination direction, 91 first direction, 93 winding axis, 101, 102 laminated bandpass filter.

Claims

1. A laminated bandpass filter including at least one LC resonator inside a laminate obtained by stacking a plurality of dielectric layers, wherein the LC resonator has a loop shape arranged such that a winding axis is perpendicular to a stacking direction of the laminate inside the laminate, the LC resonator includes a capacitor conductor pattern, a line conductor pattern and a GND conductor pattern arranged on any surface of the plurality of dielectric layers, and a first interlayer connection conductor and a second interlayer connection conductor extending in the stacking direction, the capacitor conductor pattern and the line conductor pattern are connected by the first interlayer connection conductor, and the line conductor pattern and the GND conductor pattern are connected by the second interlayer connection conductor, the LC resonator includes a capacitive portion in which at least a part of the capacitor conductor pattern and at least a part of the GND conductor pattern face each other to form a capacitance, and the capacitor conductor pattern and the GND conductor pattern are arranged on different layers, A laminated bandpass filter, wherein the length of the first interlayer connection conductor in the stacking direction is defined as the "via length" and the length of the gap between the first interlayer connection conductor and the second interlayer connection conductor is defined as the "line length", and the via length is longer than the line length.

2. The multilayer bandpass filter according to claim 1, wherein a value obtained by dividing the via length by the line length is equal to or greater than 1.1 and equal to or less than 2.

1.

3. The multilayer bandpass filter according to claim 1 or 2, wherein in the capacitive section, the capacitor conductor pattern and the GND conductor pattern contain a non-metallic additive.

4. A laminated bandpass filter according to any one of claims 1 to 3, wherein the length of the laminate in the lamination direction is longer than the length of the laminate along the longitudinal direction of the line conductor pattern.

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