Multilayer Bandpass Filter

Abstract

To obtain a laminated band-pass filter that makes it possible to mitigate the degradation of filter performance due to manufacturing dispersion.SOLUTION: A laminated band-pass filter 1 comprises: a dielectric substrate 2; and a laminate structure that includes a first grounding conductor that is provided on a first side that is one end side of the dielectric substrate 2 in the thickness direction, a second grounding conductor that is provided on a second side that is the other end side of the dielectric substrate 2 in the thickness direction, and a conductive layer 3 that is an internal layer of the dielectric substrate 2 and has a plurality of resonators 8. The plurality of resonators 8 are such that one end of a resonator 8 is open, and the other end of the resonator 8 is electrically connected to the first and second grounding conductors, thereby constituting an inter-digital type filter. The conductive layer 3 is composed of a material the malleability of which is high, as compared with layers other than the conductive layer 3 of the laminate structure.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a laminated bandpass filter comprising multiple resonators. [Background technology]

[0002] For bandpass filters used in high-frequency bands, a known technique is to form a bandpass filter structure in the inner layer of a multilayer ceramic substrate, with the aim of saving space by miniaturizing the circuit or improving the electromagnetic shielding function to prevent unwanted coupling with surrounding circuits in high-density packaging.Multilayer ceramic substrates include low-temperature co-fired ceramics (LTCC) substrates and high-temperature co-fired ceramics (HTCC) substrates.

[0003] Patent Document 1 discloses a filter in which a plurality of resonators are arranged on an inner layer of a multilayer ceramic substrate, and a grounding through-hole is provided at the end of each resonator in the longitudinal direction. In the filter of Patent Document 1, the longitudinal direction of the resonators is perpendicular to the juxtaposition direction in which the plurality of resonators are arranged. One of the resonators adjacent to each other in the juxtaposition direction has a through-hole at one end in the longitudinal direction, and the other of the resonators has a through-hole at the other end in the longitudinal direction. Patent Document 1 discloses a configuration in which a plurality of resonators are arranged on the same plane in an inner layer of a multilayer ceramic substrate, and a configuration in which a plurality of resonators are arranged at positions alternately shifted in the thickness direction of the multilayer ceramic substrate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5297227 Summary of the Invention [Problem to be solved by the invention]

[0005] Multilayer ceramic substrates are prone to greater manufacturing variations than single-layer substrates, which can lead to degradation of filter performance. The conventional technology disclosed in Patent Document 1 does not address manufacturing variations, which can lead to degradation of filter performance due to manufacturing variations. In particular, in a configuration in which multiple resonators are arranged at alternately shifted positions in the thickness direction, filter performance is achieved by the coupling coefficient in the thickness direction, which can easily lead to degradation of filter performance due to variations in the thickness of each layer in the multilayer ceramic substrate. Therefore, conventional technology has had the problem of making it difficult to reduce degradation of filter performance due to manufacturing variations.

[0006] The present disclosure has been made in view of the above, and has an object to provide a multilayer bandpass filter that can reduce degradation of filter performance due to manufacturing variations. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, the multilayer bandpass filter according to the present disclosure has a laminated structure including a dielectric substrate, a first ground conductor provided on a first surface, which is one end surface of the dielectric substrate in the thickness direction, a second ground conductor provided on a second surface, which is the other end surface of the dielectric substrate in the thickness direction, and a conductive layer, which is an internal layer of the dielectric substrate, and which has a plurality of resonators. One end of each of the plurality of resonators is open and the other end of the resonator is electrically connected to the first ground conductor and the second ground conductor, forming an interdigital filter. The conductive layer is made of a material that is more malleable than each of the layers other than the conductive layer in the laminated structure. [Effects of the Invention]

[0008] The multilayer bandpass filter according to the present disclosure has the advantage of being able to reduce degradation of filter performance due to manufacturing variations. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view showing a configuration of a multilayer bandpass filter according to a first embodiment; [Figure 2] FIG. 1 is a plan view showing an internal configuration of a multilayer bandpass filter according to a first embodiment; [Figure 3] 1 is a cross-sectional view of a multilayer bandpass filter according to a first embodiment; [Figure 4] FIG. 1 is a diagram for explaining the relationship between the thickness of the multilayer band-pass filter and the pass characteristics of the multilayer band-pass filter according to the first embodiment. [Figure 5] FIG. 1 is a diagram for explaining the relationship between the width of a resonator in the multilayer bandpass filter and the pass characteristics of the multilayer bandpass filter according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, a multilayer bandpass filter according to an embodiment will be described in detail with reference to the drawings.

[0011] Embodiment 1 Fig. 1 is a perspective view showing the configuration of a multilayer bandpass filter 1 according to a first embodiment. Fig. 2 is a plan view showing the internal configuration of the multilayer bandpass filter 1 according to the first embodiment. Fig. 3 is a cross-sectional view of the multilayer bandpass filter 1 according to the first embodiment. Fig. 3 shows a cross section taken along line III-III shown in Fig. 2.

[0012] The multilayer bandpass filter 1 has a bandpass filter structure formed in an inner layer of a multilayer ceramic substrate such as an LTCC substrate or an HTCC substrate. The multilayer structure of the multilayer bandpass filter 1 includes a dielectric substrate 2, a conductive layer 3 which is an inner layer of the dielectric substrate 2, a first ground conductor 4 provided on a first surface of the dielectric substrate 2, and a second ground conductor 5 provided on a second surface of the dielectric substrate 2. The multilayer bandpass filter 1 also has a plurality of first through holes 6 and a plurality of second through holes 7.

[0013] The first surface of the dielectric substrate 2 is the surface at one end of the dielectric substrate 2 in the thickness direction. The second surface of the dielectric substrate 2 is the surface at the other end in the first direction, which is the thickness direction of the dielectric substrate 2. The first and second surfaces are parallel to each other. The first direction is the normal direction to the first surface and also the normal direction to the second surface. The dielectric substrate 2 is made up of two ceramic plates 2a and 2b stacked on top of each other. In Figure 1, the dielectric substrate 2 is represented by a dashed line, and the components other than the dielectric substrate 2 are represented by solid lines. Also, in Figure 1, the first ground conductor 4 and the second ground conductor 5 are not shown. Figure 2 shows the components provided inside the dielectric substrate 2 as viewed from the first surface side.

[0014] The conductive layer 3 is a layered conductor parallel to the first and second surfaces. The conductive layer 3 forms a transmission path through which high-frequency signals propagate. The conductive layer 3 is disposed between the ceramic plates 2a and 2b. The conductive layer 3 includes multiple resonators 8, two through-hole connection portions 9, a power supply portion 10, and an output portion 11. Each of the multiple resonators 8 has a rectangular planar shape. The second direction, in which the multiple resonators 8 are arranged, is parallel to the first and second surfaces. The conductive layer 3 shown in FIGS. 1 and 2 has eight resonators 8. The number of resonators 8 on the conductive layer 3, i.e., the number of stages, can be determined according to the desired filter characteristics. The third direction, which is the longitudinal direction of each resonator 8, is perpendicular to the first direction and perpendicular to the second direction. The multiple resonators 8 are arranged at equal intervals in the second direction.

[0015] One of the two through-hole connection portions 9 constitutes one end in the third direction of the conductive layer 3. The other of the two through-hole connection portions 9 constitutes the other end in the third direction of the conductive layer 3. Each through-hole connection portion 9 is electrically connected to each of the first through-holes 6 and the second through-holes 7.

[0016] A plurality of first through holes 6 are formed in the ceramic plate 2a. Each of the first through holes 6 electrically connects a through hole connecting portion 9 and a first ground conductor 4. A plurality of second through holes 7 are formed in the ceramic plate 2b. Each of the second through holes 7 electrically connects a through hole connecting portion 9 and a second ground conductor 5.

[0017] One of the ends of each resonator 8 in the third direction is an open end. The other end of each resonator 8 in the third direction is connected to a through-hole connection portion 9. The other end of each resonator 8 is electrically connected to the first ground conductor 4 via the through-hole connection portion 9 and the first through-hole 6. The other end of each resonator 8 is also electrically connected to the second ground conductor 5 via the through-hole connection portion 9 and the second through-hole 7.

[0018] The resonators 8 connected to one of the two through-hole connection portions 9 and the resonators 8 connected to the other of the two through-hole connection portions 9 are arranged alternately in the second direction. One end of each of the multiple resonators 8 is open, and the other end of each of the multiple resonators 8 is electrically connected to the first ground conductor 4 and the second ground conductor 5. The multiple resonators 8 form an interdigital filter.

[0019] Of the multiple resonators 8, the resonator 8 at one end in the second direction is connected to a power supply unit 10. A high-frequency signal is input to the power supply unit 10. Of the multiple resonators 8, the resonator 8 at the other end in the second direction is connected to an output unit 11. The multilayer bandpass filter 1 outputs the high-frequency signal from the output unit 11.

[0020] The line length of the resonator 8 is a length equivalent to (λc) / 4. The line length of the resonator 8 is the length of the resonator 8 in the third direction. λc is the wavelength corresponding to the center frequency of the high-frequency signal propagating through the conductive layer 3, i.e., the wavelength corresponding to the center frequency of the multilayer bandpass filter 1. The multilayer bandpass filter 1 includes a plurality of resonators 8, each of which is a short stub with a line length of (λc) / 4. Instead of such a plurality of resonators 8, the multilayer bandpass filter 1 may include a plurality of resonators, each of which is an open stub with a line length of (λc) / 2.

[0021] 1 to 3, the conductive layer 3 and the first ground conductor 4 are connected via the first through-hole 6, and the conductive layer 3 and the second ground conductor 5 are connected via the second through-hole 7, but this is not limiting. The conductive layer 3 and the first ground conductor 4 may be connected directly without the first through-hole 6, and the conductive layer 3 and the second ground conductor 5 may be connected directly without the second through-hole 7.

[0022] In the first embodiment, the multilayer bandpass filter 1 has, as a countermeasure against degradation of filter performance due to variations in thickness of the multilayer bandpass filter 1, only the conductive layer 3 of the multilayer bandpass filter 1 made of a material with excellent malleability. The conductive layer 3 is made of a metal material such as gold or high-purity silver. The first ground conductor 4 and the second ground conductor 5 are made of a metal material with lower malleability than the conductive layer 3, such as copper. The conductive layer 3 is made of a material with higher malleability than the layers other than the conductive layer 3 in the laminate structure of the multilayer bandpass filter 1. Furthermore, the conductive layer 3 is made of a material with higher malleability than the materials used for the first through holes 6 and the second through holes 7. The materials used for the first through holes 6 and the second through holes 7 are each, for example, copper. Thus, in the multilayer bandpass filter 1, only the conductive layer 3 is made of a material with excellent malleability.

[0023] FIG. 4 is a diagram illustrating the relationship between the thickness of the multilayer band-pass filter 1 according to the first embodiment and the pass characteristics of the multilayer band-pass filter 1. In FIG. 4, the vertical axis represents attenuation. The horizontal axis represents normalized frequency. The normalized frequency is a frequency normalized based on the center frequency of a high-frequency signal propagating through the conductive layer 3. In FIG. 4, the solid line graph represents the pass characteristics when the thickness of the multilayer band-pass filter 1 is a reference value. The reference value of the thickness of the multilayer band-pass filter 1 is, for example, the design value of the thickness of the multilayer band-pass filter 1. The dashed line graph represents the pass characteristics when the thickness of the multilayer band-pass filter 1 is 0.5% thinner than the reference value. The dashed line graph represents the pass characteristics when the thickness of the multilayer band-pass filter 1 is 0.5% thicker than the reference value.

[0024] The thinner the multilayer bandpass filter 1, the shorter the distance between the conductive layer 3 and the first ground conductor 4 and the distance between the conductive layer 3 and the second ground conductor 5. On the other hand, the thicker the multilayer bandpass filter 1, the longer the distance between the conductive layer 3 and the first ground conductor 4 and the distance between the conductive layer 3 and the second ground conductor 5. The double-headed arrows in FIG. 4 represent the change in the passband when the thickness of the multilayer bandpass filter 1 is changed around a reference value. As shown in FIG. 4, the thinner the multilayer bandpass filter 1, the narrower the passband, and the thicker the multilayer bandpass filter 1, the wider the passband. Hereinafter, this feature will be referred to as the first feature.

[0025] FIG. 5 is a diagram illustrating the relationship between the width of the resonator 8 in the multilayer bandpass filter 1 according to the first embodiment and the pass characteristics of the multilayer bandpass filter 1. The width of the resonator 8 is the width of the resonator 8 in the second direction. In FIG. 5, the vertical axis represents attenuation. The horizontal axis represents normalized frequency. In FIG. 5, the solid line graph represents the pass characteristics when the width of the resonator 8 is a reference value. The reference value of the width of the resonator 8 is, for example, the design value of the width of the resonator 8. The dashed line graph represents the pass characteristics when the width of the resonator 8 is 0.1% narrower than the reference value. The dashed line graph represents the pass characteristics when the width of the resonator 8 is 0.1% wider than the reference value.

[0026] The double-headed arrows in FIG. 5 represent the change in the passband when the width of the resonator 8 is changed around a reference value. Since multiple resonators 8 form an interdigital filter, the spacing between the resonators 8 changes depending on the width of each resonator 8. That is, the narrower the width of the resonator 8, the wider the spacing between the resonators 8, and vice versa. As shown in FIG. 5, the narrower the width of the resonator 8, the narrower the passband, and the wider the width of the resonator 8, the wider the passband. Hereinafter, this feature will be referred to as the second feature.

[0027] One type of manufacturing variation in the multilayer bandpass filter 1 is the variation in the thickness of the multilayer bandpass filter 1, which is caused by the variation in the pressing pressure, which is the pressure applied in the thickness direction when manufacturing the multilayer bandpass filter 1. The stronger the pressing pressure, the thinner the multilayer bandpass filter 1 becomes, and therefore, due to the first feature, the stronger the pressing pressure, the narrower the passband of the multilayer bandpass filter 1 becomes. If manufacturing variation occurs due to the pressing pressure being too strong when manufacturing the multilayer bandpass filter 1, the passband of the multilayer bandpass filter 1 will become narrower.

[0028] In the first embodiment, only the conductive layer 3 in the laminate structure of the multilayer bandpass filter 1 is made of a material with excellent malleability. Therefore, when the pressing pressure is too strong, the conductive layer 3 of each layer in the laminate structure is stretched in the second and third directions and becomes thinner. When the width of each resonator 8 is increased by stretching the conductive layer 3, the second feature acts to widen the passband of the multilayer bandpass filter 1. This action counteracts the band narrowing caused by the thinning of the multilayer bandpass filter 1, thereby reducing the band narrowing caused by variations in the thickness of the multilayer bandpass filter 1. In this way, the multilayer bandpass filter 1 can reduce degradation of filter performance due to manufacturing variations.

[0029] Furthermore, because the weaker the pressing pressure, the thicker the multilayer bandpass filter 1, and therefore the weaker the pressing pressure, the wider the passband of the multilayer bandpass filter 1 due to the first feature. If manufacturing variations occur due to an excessively weak pressing pressure when manufacturing the multilayer bandpass filter 1, the band of the multilayer bandpass filter 1 will become wider.

[0030] In the first embodiment, if the pressing pressure is too weak, the conductive layer 3 will not expand much, and the width of each resonator 8 in the conductive layer 3 will become narrower. When the width of each resonator 8 becomes narrower, the second feature acts to narrow the passband of the multilayer bandpass filter 1. This action counteracts the band broadening caused by an increase in the thickness of the multilayer bandpass filter 1, thereby reducing the band broadening caused by variations in the thickness of the multilayer bandpass filter 1. In this case as well, the multilayer bandpass filter 1 can reduce degradation of filter performance caused by manufacturing variations.

[0031] In the laminated structure of the laminated bandpass filter 1, only the conductive layer 3 is made of a material with excellent malleability, so the influence of manufacturing variations in the thickness direction of the laminated bandpass filter 1 can be reduced for the first ground conductor 4, the second ground conductor 5, the first through hole 6, and the second through hole 7.

[0032] By using gold or silver as the material for the conductive layer 3, the laminated bandpass filter 1 can ensure malleability for the conductive layer 3, which can reduce degradation of filter performance due to manufacturing variations. The material for the conductive layer 3 may be any material that has excellent malleability, no problems with electrical properties, and no problems with use in manufacturing the laminated bandpass filter 1. The material for the conductive layer 3 may be a material other than gold or silver.

[0033] According to the first embodiment, in the multilayer bandpass filter 1, the multiple resonators 8 of the conductive layer 3 form an interdigital filter. Furthermore, the conductive layer 3 is made of a material that is more malleable than the layers other than the conductive layer 3 in the laminated structure. The multilayer bandpass filter 1 can reduce changes in pass characteristics due to variations in the thickness of the multilayer bandpass filter 1. As a result, the multilayer bandpass filter 1 has the effect of reducing degradation of filter performance due to manufacturing variations.

[0034] The configurations described in the above embodiments are examples of the contents of the present disclosure. The configurations of the embodiments can be combined with other known technologies. Part of the configurations of the embodiments can be omitted or modified without departing from the gist of the present disclosure. [Explanation of symbols]

[0035] 1 laminated bandpass filter, 2 dielectric substrate, 2a, 2b ceramic plates, 3 conductive layer, 4 first ground conductor, 5 second ground conductor, 6 first through hole, 7 second through hole, 8 resonator, 9 through hole connection portion, 10 power supply portion, 11 output portion.

Claims

1. a dielectric substrate; a first ground conductor provided on a first surface, which is a surface at one end in a thickness direction of the dielectric substrate; a second ground conductor provided on a second surface, which is the surface at the other end in the thickness direction of the dielectric substrate; a conductive layer within the dielectric substrate, the conductive layer having a plurality of resonators; A laminated structure including one end of each of the plurality of resonators is open, and the other end of each of the resonators is electrically connected to the first ground conductor and the second ground conductor, thereby forming an interdigital filter; A laminated bandpass filter, wherein the conductive layer is made of a material that is more malleable than each of the layers other than the conductive layer in the laminated structure.

2. a first through hole electrically connecting the conductive layer and the first ground conductor; a second through hole electrically connecting the conductive layer and the second ground conductor; 2. The laminated bandpass filter according to claim 1, wherein the conductive layer is made of a material that is more malleable than the material used for the first through hole and the material used for the second through hole.

3. 3. The laminated bandpass filter according to claim 1, wherein the conductive layer is made of gold or silver.

Images