Patent Application
20240014534
This application claims the benefit of priority to Japanese Patent Application No. 2021-055344 filed on Mar. 29, 2021 and is a Continuation Application of PCT Application No. PCT/JP2022/004292 filed on Feb. 3, 2022. The entire contents of each application are hereby incorporated herein by reference.
The present disclosure relates to a dielectric filter, and, more particularly, to a technology to improve filter characteristics of a dielectric filter.
Japanese Patent Laid-Open No. 2007-235465 discloses a band-pass filter including a multilayer dielectric resonator that includes multiple internal electrode layers stacked in a dielectric. In the band-pass filter disclosed in Japanese Patent Laid-Open No. 2007-235465, the inductive portion of the internal electrode layer is configured in a longitudinal pattern with a portion having a tapered width. This configuration allows reduction of the resonance frequency, without reducing Q value. As a result, size reduction of the resonator can be achieved.
For example, the dielectric filter, as disclosed in Japanese Patent Laid-Open No. 2007-235465, is used, in a small handheld device represented by a mobile phone or smartphone, to filter the radio-frequency signal.
Typically, the dielectric filter is manufactured by compression bonding or sintering a dielectric including multiple plate conductors disposed therein. The dielectric filter manufactured by this process may have a plate conductor that has a thinner tip, as compared to other portions of the plate conductor, due to an external pressure, or the stress caused by thermal contraction.
Typically, the radio-frequency current is known to primarily flow near the surface of a conductor, which is a signal carrying member, due to the skin effect. Therefore, a tapered tip of a plate conductor in the dielectric filter may cause an increased resistance at a radio-frequency current passage path. This increases a loss caused by the passage of the current, and Q value thereby decreases. This may result in degradation in filter characteristics of the dielectric filter.
Preferred embodiments of the present invention prevent a Q value in dielectric filters from being reduced.
A dielectric filter according to a preferred embodiment of the present invention includes a laminate body having a cuboid shape, a first plate electrode and a second plate electrode, a plurality of resonators, and a first shield conductor and a second shield conductor. The laminate body includes a plurality of dielectric layers. The first plate electrode and the second plate electrode are provided within the laminate body and spaced apart from each other in a lamination direction. The plurality of resonators are provided between the first plate electrode and the second plate electrode and extend in a first direction orthogonal or substantially orthogonal to the lamination direction. The first shield conductor and the second shield conductor are provided within the laminate body on a first side surface and a second side surface orthogonal or substantially orthogonal to the first direction and connected to the first plate electrode and the second plate electrode. The plurality of resonators are provided within the laminate body and aligned in a second direction orthogonal or substantially orthogonal to the lamination direction and the first direction. The plurality of resonators each include a first end connected to the first shield conductor and a second end spaced apart from the second shield conductor. The plurality of resonators each include a plurality of the conductors laminated in the lamination direction. When the plurality of resonators are viewed in plan from the first direction, the plurality of the conductors each include a first region including an end portion of the conductor and having a thickness greater than other portions of the conductor.
With each of the dielectric filters according to preferred embodiments of the present invention, the first region, which includes an end portion of one of the plurality of electrodes included in the dielectric resonator, has a thickness greater than other portions of the electrode. Each electrode having such a profile enables a reduced resistance of the electrode at a current passage path when a radio-frequency current flows therethrough. As a result, a Q value in the dielectric filter can be prevented from being reduced.
The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings.
Hereinafter, preferred embodiments of the present invention will be described, with reference to the accompanying drawings. The same reference signs are used to refer to like or corresponding portions in the drawings, and the description thereof will not be repeated.
Referring to
The communication device 10 upconverts a signal, carried from the RF circuit 50, into a radio-frequency signal and emits the radio-frequency signal through the antenna 12. The modulated digital signal, output from the RF circuit 50, is converted into an analog signal by the digital-to-analog converter 40. The mixer 30 mixes the analog signal, converted from the digital signal by the digital-to-analog converter 40, with an oscillating signal from the local oscillator 32, and upconverts the mixed signal into a radio-frequency signal. The band-pass filter 28 filters out undesired waves caused by the upconversion and extracts only a signal that is in a desired frequency band. The attenuator 26 adjusts the strength of the signal. The amplifier 24 power-amplifies the signal having passed through the attenuator 26, to a predetermined level. The band-pass filter 22 filters out, from the signal, undesired waves caused during the amplification process, and passes therethrough only a signal component that is in a frequency band defined by the communication standards. The signal having passed through the band-pass filter 22 is emitted as a transmission signal through the antenna 12.
Filter devices corresponding to preferred embodiments of the present invention can be used as the band-pass filters 22 and 28 included in the communication device 10 as described above.
Next, referring to
Referring to
For example, each dielectric layer included in the laminate body 110 is made of ceramics such as a low temperature co-fired ceramics (LTCC), or a resin. Within the laminate body 110, the distributed elements including the resonators, and capacitors and inductors to couple the distributed elements include multiple plate conductors provided on each dielectric layer and multiple vias provided between the dielectric layers. The “via,” as used herein, refers to a conductor that connects the conductors included in different dielectric layers and extends in the lamination direction. For example, the via is provided by a conductive paste, plating, and/or a metal pin.
In the following description, the lamination direction for the laminate body 110 will be referred to as “Z-axis direction,” a direction orthogonal or substantially orthogonal to Z-axis direction and along a long side of the laminate body 110 will be referred to as “X-axis direction” (a second direction), and a direction along a short side of the laminate body 110 will be referred to as “Y-axis direction” (a first direction). Moreover, in the following, the positive direction of Z-axis in the figures may be referred to as the upper side of the figures and the negative direction of Z-axis in the figures may be referred to as the lower side of the figures.
As shown in
The filter device 100 includes an input terminal T1 and an output terminal T2, which are disposed on the lower surface 112 of the laminate body 110. The input terminal T1 is disposed on the lower surface 112, closer to the side surface 113 in the positive direction of X axis. The output terminal T2, in contrast, is disposed on the lower surface 112, closer to the side surface 114 in the negative direction of X axis. The input terminal T1 and the output terminal T2 are connected to corresponding electrodes on the mounting substrate by connection members such as solder bumps, for example.
Next, referring to
The plate electrodes 130 and 135 are disposed oppositely within the laminate body 110, spaced apart from each other in the lamination direction (Z-axis direction). The plate electrode 130 is disposed on the dielectric layer that is closer to the upper surface 111. Ends of the plate electrode 130 along X axis are connected to the shield conductors 121 and 122. The plate electrode 130 is shaped to cover or substantially cover the dielectric layers, as viewed in plan from the lamination direction.
The plate electrode 135 is disposed on the dielectric layer that is closer to the lower surface 112. As viewed in plan from the lamination direction, the plate electrode 135 has an H shape or an approximate H shape in which notches are provided opposite the input terminal T1 and the output terminal T2. Ends of the plate electrode 135 along X axis are connected to the shield conductors 121 and 122.
In the laminate body 110, the resonators 141 to 145 are disposed between the plate electrode 130 and the plate electrode 135. The resonators 141 to 145 extend in Y-axis direction. Each end (a first end) of each of the resonators 141 to 145 in the positive direction of Y axis is connected to the shield conductor 121. Each end (a second end) of each of the resonators 141 to 145 in the negative direction of Y axis, in contrast, is spaced apart from the shield conductor 122.
In the filter device 100, the resonators 141 to 145 are aligned in X-axis direction within the laminate body 110. More specifically, the resonators 141, 142, 143, 144, and 145 are disposed in the stated order from the positive direction of X axis to the negative direction of X axis.
The resonators 141 to 145 each include multiple conductors disposed along the lamination direction. As shown in
Referring to
Moreover, in the resonator 140, the conductors including each resonator are electrically connected to the connection conductor 170 near the second end on the shield conductor 122 side. The distance between the second end of each resonator and the connection conductor 150 is designed to be approximately λ/4, where λ is the wavelength of a radio-frequency signal carried by the resonator.
As shown in
The resonator 140 defines and functions as a distributed-element TEM mode resonator, which includes multiple conductors as middle conductors and the plate electrodes 130 and 135 as outer conductors.
The resonator 141 is connected to the input terminal T1 by vias V10 and V11 and a plate electrode PL1. The resonator 145 is connected to the output terminal T2 by vias and a plate electrode, which is hidden from view by the resonator in
On the second end side of the resonator 140, a projecting capacitor electrode is disposed between adjacent resonators. The capacitor electrode is an overhung portion of the conductors including the resonator. An extent of capacitive coupling of the resonators can be adjusted by adjusting the length of the capacitor electrode in Y-axis direction, the distance of the capacitor electrode to an adjacent resonator, and/or the number of conductors comprising the capacitor electrode.
In the filter device 100, a capacitor electrode C10 projects from the resonator 141 toward the resonator 142, and a capacitor electrode C20 projects from the resonator 142 toward the resonator 141, as shown in
The capacitor electrodes C10 to C50 are not necessary. Some or all of the capacitor electrodes may not be provided if a desired extent of coupling is achieved between the resonators. In addition of the configuration of
In the filter device 100, a capacitor electrode 160 is also disposed opposite the second end of the resonator 140. A cross section of the capacitor electrode 160 parallel or substantially parallel to Z-X plane is the same as or similar to the cross section of the resonator 140. The capacitor electrode 160 is connected to the shield conductor 122. This allows a capacitor to be defined by the resonator 140 and a corresponding capacitor electrode 160. The capacitance of the capacitor including the resonator 140 and the corresponding capacitor electrode 160 can be adjusted by adjusting a gap (a distance in Y-axis direction) GP between the resonator and the capacitor electrode in
In the filter device 100, as a radio-frequency signal is transmitted from the input terminal T1 to the output terminal T2, the radio-frequency current flows through the conductors of each resonator with a resonance of the radio-frequency signal.
In general, the radio-frequency current is known to primarily flow near the surface of a conductor, due to the skin effect. Therefore, if a cross-sectional shape of the entirety of the conductors is a rectangular or substantially rectangular shape, current crowding is caused at the corners (i.e., the ends of the uppermost and lowermost electrodes). The current crowding can be alleviated by configuring the conductors, as a whole, to have an oval or a substantially oval cross section, as shown in
In a resonator of the filter device 100, a current also flows through the conductors defining the resonator in the longitudinal direction (Y-axis direction) and a current flows between the conductors and through the plate electrodes 130 and 135 via the connection conductors 150 and 170. As described with respect to
As an approach to achieve the reduced resistance of each of the conductors including a resonator, it may also be contemplated to increase the thickness of the entirety of the conductor, rather than only the thicknesses of portions of the conductor in particular regions as described above. However, an increase of the conductor density in the lamination direction may cause structural defects in the manufacturing process, such as, for example, development of cracks between a conductor and a dielectric, delamination of interlayers, and/or degradation in coplanarity of the surface of the laminate body 110, due to the difference in coefficient of thermal expansion between a region dense with conductors and a region not dense with conductors. Therefore, a Q value can be reduced or prevented from being reduced and the structural deficit can be reduced or prevented from occurring, by relatively increasing the thicknesses of portions of the conductor corresponding to the current path in the conductor, and relatively reducing the thicknesses of portions of the conductors that are regions having less contribution to the current path, as the filter device 100 according to Preferred Embodiment 1.
Increasing the thicknesses of the end portions of the conductors can also improve the capacitive coupling of adjacent resonators. This, thus, contributes to size reduction of the filter device 100.
The “plate electrode 130” and the “plate electrode 135” according to Preferred Embodiment 1 correspond to a “first plate electrode” and a “second plate electrode,” respectively, in the present disclosure. The “side surface 115” and the “side surface 116” according to Preferred Embodiment 1 correspond to a “first side surface” and a “second side surface,” respectively, in the present disclosure. The “shield conductor 121” and the “shield conductor 122” according to Preferred Embodiment 1 correspond to a “first shield conductor” and a “second shield conductor,” respectively, in the present disclosure. “Y-axis direction” and “X-axis direction” according to Preferred Embodiment 1 correspond to a “first direction” and a “second direction,” respectively, in the present disclosure. The “connection conductor 150 (151 to 155)” according to Preferred Embodiment 1 corresponds to a “first connection conductor” according to the present disclosure. The “connection conductor 170 (171 to 175)” according to Preferred Embodiment 1 corresponds to a “second connection conductor” in the present disclosure.
Variation 1 of a preferred embodiment of the present invention will now be described, with respect to Variation 1 of the shapes of conductors of a resonator.
Referring to
If the first regions, in which the conductors have increased thicknesses, overlap in the lamination direction, the conductor density of the overlapping portions is increased, as compared to other portions of the conductors. This can be a main cause of the structural defects as described above. However, in the filter device 100A according to Variation 1, the conductors are disposed so that the end portions of adjacent conductors do not overlap in the lamination direction. This can spread out the positions of the end portions of the conductors and reduce the conductor density in the lamination direction, thus reducing or preventing the structural defects from occurring.
Variation 2 of a preferred embodiment of the present invention will now be described with respect to Variation 2 of the shapes of the conductors of a resonator.
Referring to
As described above, in the conductors including the resonator, a portion of a conductor is removed in a region that has small contribution to the current path, and the difference in conductor density of the laminate body is thus reduced. As a result, the structural deficit can further be reduced or prevented from occurring.
The configuration according to Variation 2 may be applied to the configuration of Variation 1.
Variation 3 of a preferred embodiment of the present invention will be now described with respect to a configuration in which a second region AR2 is further increased, where a portion of a conductor is connected to a connection conductor 150.
In a TEM resonator, an open end (a second end) has low current density, and the current density increases toward the shorted end (a first end). Thus, insertion loss can be improved by increasing the thickness of the conductor near the first end portion.
In a dielectric filter that includes a resonator in which conductors are laminated, due to the difference in conductor density between a region where the resonator is disposed in the laminate body and a region where no resonator but only a dielectric is disposed, the structural defects may occur in the manufacturing process, such as, for example, development of cracks between a conductor and the dielectric, as described above.
Preferred Embodiment 2 of the present invention will now be described with respect to a configuration that can prevent the structural defects from occurring, while reducing or preventing degradation of the filter characteristics, by adjusting the number of conductors included in a resonator and the arrangement of the conductors.
In the filter device 100 according to Preferred Embodiment 1, the conductors including the resonator 140 and the capacitor electrode 160 are disposed equidistantly or substantially equidistantly in the lamination direction. In contrast, in the resonator 140D and the capacitor electrode 160D in the filter device 100D according to Preferred Embodiment 2, the conductor spacing centered across the lamination direction is greater than the conductor spacing at end regions in the lamination direction.
The conductors of each resonator at the end regions on the upper surface 111 side are connected to each other by a connection conductor 180. The conductors of each resonator at the end regions on the lower surface 112 side are connected to each other by the connection conductor 181. Since the connection conductors 180 and 181 are provided, an extent of inductive coupling of the resonators can be enhanced. Note that, depending on desired characteristics, the connection conductors 180 and 181 may not be provided.
As described in Preferred Embodiment 1, the radio-frequency current has the tendency to flow to the ends of the resonator in the cross section, due to the skin effect. Therefore, considering the cross sections of the resonator and the capacitor electrode, the current is likely to be crowed and flow near the end regions near the upper surface 111 and the lower surface 112 in the lamination direction. Therefore, in Preferred Embodiment 2, the conductors defining a resonator and a capacitor electrode are arranged so that the conductor spacing at the end regions on the upper surface side and the lower surface side are narrower than the conductor spacing at the central region, and the loss caused by the passage of the current is thereby reduced.
Stated differently, in the filter device 100D, some of the conductors at the central region are thinned out, in contrast to the conductors of the resonator and the capacitor electrode all being arranged at the same or substantially the same conductor spacing as the conductor spacing at the end regions. Accordingly, as compared to the conductors being arranged at the same or substantially the same conductor spacing as the conductor spacing at the end regions, a reduced number of conductors are disposed in the central region, and the conductor density in the lamination direction is thus reduced. Accordingly, the structural defects caused by the difference in conductor density can be reduced or prevented, while reducing or preventing a Q value from being reduced by reducing or preventing the current loss.
Referring to
As described above, regarding the conductors defining the resonator and the capacitor electrode, the conductor spacing at the central region is wider than the conductor spacing at the end regions, thus reducing the total number of conductors, while inhibiting the loss. Accordingly, the structural deficit caused by the difference in conductor density can be inhibited, while inhibiting Q value from being lowered.
While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-055344 | Mar 2021 | JP | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2022/004292 | Feb 2022 | US |
| Child | 18370686 | US |
