JP2007028140A - Dielectric filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dielectric filter wherein the length of resonator inner conductors in a mono block can be adjusted, external effect can be decreased without exposing the resonator inner conductors (columnar conductors) to the surface of the filter, and the position and the diameter of columnar electrodes are changed to control the coupling between resonators and the coupling between the resonator and a ground conductor. <P>SOLUTION: In the dielectric filter configuring the resonators by providing a plurality of through-holes to a dielectric ceramic, a first laminator comprising a ceramic dielectric sheet and having a plurality of parallel through-holes extended in the lamination direction and a second laminator comprising a ceramic dielectric sheet and having a different structure in the through-holes from that of the first laminator are joined and integrally baked, the inner conductor is formed in each through-hole, and an outer conductor, a short-circuit conductor and a terminal electrode are formed on the surface and end faces of the laminator. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a structure of a dielectric filter configured using a dielectric coaxial resonator, and relates to a dielectric filter used as a chip filter having a laminated structure.

  As a general dielectric filter, a filter is formed by combining coaxial resonators, but a ceramic monoblock is often used. In a dielectric filter having three or more resonators, it is necessary to change the resonance frequency for each resonator. For example, in the case of three elements, the resonance frequency of the two elements on both sides is the same, but the resonance frequency of the center element is often different from the resonance frequency of the two elements on both sides. Therefore, in the monoblock dielectric filter, it is necessary to form a short-circuit electrode in order to lower the resonance frequency, or to cut the center conductor in order to increase the frequency of the resonator.

In a conventional monoblock type dielectric filter, the inner conductor of the resonator is exposed at both ends of the filter. Therefore, it is easy to be affected by an external electromagnetic field, and it is necessary to add a shield structure particularly at the open end face. In addition, in the conventional monoblock type dielectric filter, the diameter of the inner conductor of the resonator and the interval between adjacent inner conductors cannot be changed in the same resonator, and even if it can be changed, it can be changed to two stages in one place. there were. For this reason, there is a limit in controlling the coupling between the resonators.
JP-A-7-142914 JP 7-31503 A JP-A-10-29006

  The present invention makes it possible to adjust the length of the inner conductor of the resonator so that each of the inner conductors of the resonator in the monoblock has an appropriate length. Further, the influence of the outside can be reduced by not exposing the inner conductor (columnar conductor) of the resonator to the surface of the filter. Further, the position and diameter of the columnar electrode can be changed to control the coupling between the resonators and the coupling between the resonator and the ground conductor.

  The present invention solves the above-described problems by forming a dielectric block in a laminated structure and forming a resonator by forming a through hole in the laminated body. That is, in a dielectric filter that includes a plurality of through holes in a dielectric ceramic and constitutes a resonator, the first laminated body that is formed of a ceramic dielectric sheet and has a plurality of parallel through holes extending in the stacking direction, and the ceramic A dielectric sheet, a second laminate having a through hole structure different from that of the first laminate is joined and integrally fired to form an inner conductor in the through hole, and the surface of the laminate and It is characterized in that an outer conductor, a short-circuit conductor, and a terminal electrode are formed on the end face.

  According to the present invention, it becomes possible to freely change the resonance frequency for each resonator, and in particular, in a dielectric filter having three or more resonators, a short-circuit electrode is formed, or a center conductor is used to increase the resonance frequency. There is no longer any need to sharpen. Further, since a structure in which the inner conductor of the resonator is not exposed to the filter end is possible, the influence from the outside can be removed and the characteristics can be stabilized. In addition, the diameter of the inner conductor of the resonator and the spacing between adjacent ones can be freely changed, so that the coupling between the resonators can be controlled and the design of high-performance filters is easy. It became.

The embodiment of the present invention is as follows. Basically, a multilayer ceramic dielectric having a plurality of through holes and a multilayer ceramic dielectric having different through hole formation forms are joined and fired integrally.
As a first embodiment, a part of the latter ceramic dielectric at a position facing the former through hole does not form a through hole. Thereby, the length of the through hole of the resonator is changed, and the resonance frequency can be adjusted by changing the length of the central conductor (columnar electrode).
As a second embodiment, there is a latter multilayer ceramic dielectric that does not have through holes. Thereby, it can be set as the structure where the edge part of a through-hole is not exposed.
As a third embodiment, there is one in which a multilayer ceramic dielectric is joined and integrated above and below a multilayer ceramic dielectric formed with a through hole. These embodiments can be used in combination and can be arbitrarily selected.

  The dielectric filter according to the present invention is manufactured by a process of forming a through-hole by bonding, punching or the like of dielectric ceramic green sheets, bonding, firing, and electrode formation. For electrode formation, a conductor paste is applied before firing, and an inner conductor, an outer conductor, a short-circuit conductor, and a terminal electrode can be formed by simultaneous firing. In particular, it is necessary to form columnar conductors that are closed on both sides by this method. It is manufactured by a method in which a large number of sheets are laminated and then the laminate is cut to obtain a large number of elements. An electrode film or the like provided in the dielectric block may be printed at the stage of lamination.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing an embodiment of the present invention, and shows a structure in which the lengths of resonators of a two-element dielectric filter are made different. A ceramic dielectric green sheet is laminated to produce a laminate with two different thicknesses. The thickness is adjusted such that the laminated body (a) corresponding to the conductor portion having a common length and (b) corresponding to the length corresponding to the difference in frequency are used. Both are adjusted to have a predetermined length after being baked and contracted. In the laminate (a), both portions corresponding to two resonators are perforated and filled with a conductive paste to form columnar electrodes. In the laminated body (b), only a portion corresponding to a long (low frequency) resonator is perforated and filled with a conductive paste to form a columnar electrode. The laminate (a) and the laminate (b) are bonded and fired. In this way, a dielectric filter (c) having resonators having different lengths in the same block is manufactured.

  FIG. 2 shows an example of configuring a three-element dielectric filter, and shows a comparison between a resonator having the same length and a length changed according to the present invention. The attenuation characteristics and return loss characteristics of the filter (a) with the same resonator length are shown in (b). On the other hand, the characteristics of (c) in which the length of the inner conductor (columnar conductor) of the resonator is changed to balance the resonance frequency are shown in (d). Conventionally, it has been necessary to adjust the frequency by making the resonator longer and scraping the resonator or adding a short-circuit electrode, but this step is not necessary.

  FIG. 3 shows an example of obtaining a structure in which the inner conductor (columnar conductor) of the resonator is not exposed to the end face. By using the layered body shown in FIG. 1 (b) that is not perforated or injected, a structure in which the open side of the inner conductor of the resonator is not exposed to the end face of the filter as shown in FIG. 3 (a) is realized. it can. As a result, the open end face that is exposed to the influence of the external electromagnetic field due to the exposure of the dielectric is shielded, so that it is difficult to be affected by the outside. Similarly, as shown in FIG. 3B, a conductor film may be formed on the bonding surface, and the short-circuit end surface may be formed inside the dielectric. When a pattern is formed on the conductor film on the short-circuit end face for adjusting the characteristics, it can be made less susceptible to external influences. Further, as shown in FIG. 3C, a half-wave resonator can be configured by opening both sides of the inner conductor of the resonator.

  FIG. 4 shows an example applied to a structure for adjusting coupling between resonators. This is an example in which the distance between the inner conductors (columnar electrodes) of adjacent resonators is different depending on the position of the same columnar electrode. By shifting the perforation position applied to the laminate of FIG. 1B, the interval between the inner conductors (columnar electrodes) of the resonator can be changed at an arbitrary position. Thereby, the coupling (capacitive coupling, inductive coupling, or both) between the resonators can be changed and adjusted. This is very useful when adjusting the passband of the filter or controlling the attenuation pole. In the conventional molding using a mold, the process up to FIG. 4 (a) was possible, but it is possible for the first time to make a change of two or more steps as shown in FIG. 4 (b).

  FIG. 5 shows another example applied to a structure for adjusting coupling between resonators. This is an example in which the thickness of the inner conductor of the resonator is changed so that the distance between the inner conductors (columnar electrodes) of adjacent resonators varies depending on the position of the same columnar electrode. By changing the diameter of the perforations applied to the laminate of FIG. 1B, the interval between the inner conductors (columnar electrodes) of the resonator can be changed at an arbitrary position. Thereby, the coupling (capacitive coupling, inductive coupling, or both) between the resonators can be changed and adjusted. This is very useful when adjusting the passband of the filter or controlling the attenuation pole. In the conventional molding using a mold, the process up to FIG. 5 (a) was possible, but it is possible for the first time to make a change of two or more steps as shown in FIG. 5 (b).

  The above example is a two-element or three-element bandpass filter, but the present invention can also be applied to a resonator, a trap, a band element filter, a duplexer, or the like. In addition, as described above, a half-wavelength coaxial resonator can be easily manufactured, and can be applied to a balanced filter. Of course, it is useful not only for the comb line type but also for an interdigital type filter.

  INDUSTRIAL APPLICABILITY The present invention can be used for all coaxial dielectric filters used in terminals of mobile communication devices, and is particularly useful for devices that require high-density mounting when a small and low profile type is required. A filter is obtained.

The perspective view which shows the Example of this invention A perspective view, a plan view, and an explanatory view of characteristics showing a comparison between a conventional and a dielectric filter according to the present invention The perspective view which shows the other Example of this invention. The perspective view which shows the other Example of this invention. The perspective view which shows the other Example of this invention.

Explanation of symbols

11: Ceramic dielectric laminate
13: Through hole (inner conductor)

Claims (7)

In a dielectric filter constituting a resonator having a plurality of through holes in a dielectric ceramic,
A first laminated body made of a ceramic dielectric sheet and having a plurality of parallel through holes extending in the laminating direction, and a second laminated body made of a ceramic dielectric sheet and having a structure of through holes different from that of the first laminated body. The body is joined and fired integrally,
A dielectric filter, wherein an inner conductor is formed in a through-hole, and an outer conductor, a short-circuit conductor, and a terminal electrode are formed on a surface and an end surface of the laminate.   2. The dielectric filter according to claim 1, wherein the through hole is formed only in a part of the second laminated body at a position facing the through hole of the first laminated body, and the through hole is not formed in the other part.   The dielectric filter according to claim 1, wherein no through hole is formed in the second laminate.   The dielectric filter according to claim 1, wherein the positions of the through holes of the first laminated body and the through holes of the second laminated body are shifted at least partially.   2. The dielectric filter according to claim 1, wherein the positions of the through holes of the first laminated body and the through holes of the second laminated body are formed to have different diameters at least partially. In a dielectric filter constituting a resonator having a plurality of through holes in a dielectric ceramic,
A first laminated body made of a ceramic dielectric sheet and having a plurality of parallel through holes extending in the laminating direction, and a second laminated body made of a ceramic dielectric sheet and having a through hole structure different from the first laminated body. 3 laminates are bonded to both end face sides of the first laminate and integrally fired,
A dielectric filter, wherein an inner conductor is formed in a through-hole, and an outer conductor, a short-circuit conductor, and a terminal electrode are formed on a surface and an end surface of the laminate.   The dielectric filter according to claim 6, wherein the second laminated body or the third laminated body is joined to the first laminated body via a conductor film.

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