JP2007295015A - Method of adjusting characteristic of dielectric filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of obtaining the desired characteristic of a dielectric filter by easily adjusting a degree of coupling between adjacent resonators among a plurality of resonators configured to be a dielectric block over a wide range with high accuracy and adjusting the resonance frequency of the resonators together with the adjustment of the coupling among the resonators at the same time. <P>SOLUTION: In the condition that inner conductors 3a to 3c and an outer conductor 4 are already formed to the dielectric block 1, a coupling adjustment groove 5 linearly extended from a third face S3 to a fourth face S4 are formed between formed positions of two adjacent throughholes 2a, 2b on a first face S1 of the dielectric block 1, and the coupling degree between the two resonators by throughholes 2a, 2b is adjusted depending on the depth, width or length of the coupling adjustment groove 5. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for adjusting characteristics of a dielectric filter formed by forming a conductor inside and outside a dielectric block.

  Patent Documents 1 to 4 are disclosed as dielectric filters in which a conductor is formed inside and outside a dielectric block whose outer shape is substantially a rectangular parallelepiped.

  In Patent Document 1, a plurality of resonators are formed in a dielectric block, grooves are formed between the resonators, and the resonators are coupled to each other at a dielectric block portion other than the grooves.

  In Patent Document 2, at least three through holes are arranged in parallel in a dielectric block, a recess is formed on the open surface side of at least one resonator inside thereof, and the inner conductor and capacitance of the resonator adjacent to the recess. An electrode to be coupled is formed on the inner peripheral surface of the recess.

  In Patent Document 3, a groove in which the bottom of the dielectric block becomes the exposed surface of the through hole is formed so as to extend in the arrangement direction of the through hole, and a coupling capacitor substrate is provided in the groove.

In Patent Document 4, the inner conductor is cut to adjust the coupling between the resonators.
JP-A-61-62203 JP 2001-068903 A Japanese Utility Model Publication No. 5-15505 JP-A-7-176910

  The dielectric filter using such a dielectric block has its filter characteristics defined by the shape and size of the dielectric block formed by molding or cutting and the pattern of the conductor formed inside and outside thereof.

  However, the characteristics of the obtained filter vary depending on the dimensional accuracy of the dielectric block and the pattern formation accuracy of the conductor formed inside and outside thereof. Therefore, in order to finally obtain a desired filter characteristic, as disclosed in Patent Document 4, the characteristic adjustment is performed by partial deletion (cutting) of the conductor formed on the dielectric block.

  However, there is a problem that a large coupling adjustment amount (coupling adjustment range) cannot be obtained simply by deleting the conductor film formed inside and outside the dielectric block. In addition, since the inner conductor formed on the inner surface of the through hole is partially removed, a cutting tool having a very small tip must be used. In addition, since the alignment of the dielectric filter, which is a characteristic adjustment target, and the cutting tool must be performed with high accuracy in the three-dimensional direction, there is a problem in that the number of manufacturing steps is increased and the manufacturing cost increases. In addition, since the relationship between the amount of partial deletion of the inner conductor (cutting amount) and the change in characteristics varies greatly depending on the accuracy of the cutting position, there is a problem that adjustment parameters for obtaining desired characteristics increase.

  An object of the present invention is to solve the above-described problems and to easily and accurately adjust a coupling degree between adjacent resonators in a dielectric block over a wide range. The object is to provide a filter characteristic adjustment method.

  Another object of the present invention is to provide a dielectric filter characteristic adjustment method that obtains desired filter characteristics by simultaneously adjusting the resonance frequency of the resonators together with coupling adjustment between the resonators. is there.

  In the dielectric filter characteristic adjusting method according to the present invention, the rows are arranged in a direction parallel to the third and fourth surfaces passing through between the first and second surfaces facing each other and orthogonal to the first and second surfaces. A substantially rectangular parallelepiped-shaped dielectric block having a plurality of through-holes disposed therein, an inner conductor formed on the inner surface of the through-hole, and outer conductors on the other five surfaces excluding the first surface of the dielectric block In a state where the inner conductor and the outer conductor are already formed, between the adjacent two through-hole forming positions on the first surface of the dielectric block, linearly from the third surface to the fourth surface direction. The coupling adjustment groove extending is formed, and the coupling degree between the two resonators formed in the two through-hole forming portions is adjusted according to the depth, width, or length of the coupling adjustment groove. It is a feature.

  (2) In the dielectric filter characteristic adjusting method according to the present invention, the coupling adjusting groove is formed at a position overlapping one or both of the two through holes. It is said.

  (3) In the dielectric filter characteristic adjusting method according to the present invention, the frequency adjusting method is different from the coupling adjusting groove at a position parallel to the extending direction of the coupling adjusting groove and crossing the through hole. A groove is formed, and the resonance frequency of the resonator formed in the through hole forming portion that the frequency adjusting groove crosses is adjusted.

  (4) Further, in the dielectric filter characteristic adjusting method according to the present invention, the through hole has a step structure in which the inner diameter on the first surface side is larger than the inner diameter on the second surface side, and the first, second, Of the third three through-holes, the distance between the central axis on the second surface side of the second through-hole and the first through-hole, and the second surface side of the second through-hole and the third through-hole. The distance between the central axes is different, and the filter characteristics are adjusted by both the coupling adjustment groove between the first and second through holes and the coupling adjustment groove between the second and third through holes. It is characterized by.

  (1) With the inner conductor and the outer conductor already formed on the dielectric block, linearly between two adjacent through hole forming positions on the first surface, which is the open surface of the dielectric block By forming the extending coupling adjusting groove, the coupling adjusting groove can be formed very easily as compared with the case where the inner conductor formed on the inner surface of the through hole is partially deleted. In addition, since the cutting tool only needs to be moved linearly in one of the three-dimensional axes with respect to the dielectric block, the machining is facilitated, and the position accuracy of the coupling adjustment groove for the dielectric block is also improved. Easily enhanced. For example, an alignment mechanism (function) of a cutting tool or a dielectric filter can be used, and characteristics can be adjusted by a simple operation using a simple mechanism.

  Furthermore, since it is only necessary to linearly move the cutting tool relative to the dielectric filter or the dielectric filter relative to the cutting tool, the width of the coupling adjusting groove is kept constant depending on the depth. Alternatively, a desired degree of binding can be easily obtained depending on the length.

  (2) The inner conductor formed on the inner surface of the overlapped through hole is partially formed by forming the coupling adjusting groove at a position overlapping with a part of one or both of the two through holes. Therefore, the resonance frequency of the resonator formed in the through hole forming portion can also be adjusted. That is, the coupling degree and the resonance frequency can be adjusted by the position of the coupling adjustment groove formed in the dielectric block.

  (3) By forming a frequency adjusting groove different from the coupling adjusting groove at a position parallel to the extending direction of the coupling adjusting groove and crossing the through hole, the frequency adjusting groove crosses. The resonance frequency of the resonator formed in the through hole forming portion can be adjusted. In other words, the coupling adjustment groove adjusts the degree of coupling between the two resonators formed in the two through-hole forming portions, and the frequency adjustment groove is formed by the same cutting method, so that the desired resonator is obtained. The resonance frequency can be also adjusted.

  (4) The through hole has a step structure with a large inner diameter on the open surface side, and the distance between the second surface side central axis of the first and second through holes among the three consecutive through holes, and the second and second The distance between the center axes on the second surface side of the three through holes is different, and the coupling adjustment groove between the first and second through holes and the coupling adjustment groove between the second and third through holes are different. By adjusting the filter characteristics on both sides, the desired filter characteristics can be easily obtained under a high degree of freedom by both inductive coupling and capacitive coupling between two adjacent resonators.

A method for adjusting the characteristics of the dielectric filter according to the first embodiment will be described with reference to FIG.
1A is a front view of the dielectric filter, and FIG. 1B is a bottom view thereof. The dielectric block 1 has a rectangular parallelepiped shape having first to sixth surfaces indicated by S1 to S6. Three through holes 2a, 2b, 2c penetrating between the first surface S1 and the second surface S2 facing each other of the dielectric block 1 are connected to a third surface S3 orthogonal to the first surface S1 and the second surface S2. They are arranged in a row in a direction parallel to the fourth surface S4. Inner conductors 3a, 3b and 3c are formed on the inner surfaces of these through holes 2a to 2c, respectively.

  The outer conductor 4 is formed on the other five surfaces (S2 to S6) excluding the first surface S1 of the dielectric block 1. Accordingly, the first surface S1 is an open surface, and the second surface S2 is a short-circuit surface. Further, an input / output electrode 6a separated from the outer conductor 4 is formed from the fourth surface S4 to the fifth surface S5 of the dielectric block 1. Similarly, an input / output electrode 6c is formed from the fourth surface S4 to the sixth surface S6.

  The first surface S1 (open surface) side of the through holes 2a, 2b, 2c is a step hole whose inner diameter is thicker than that of the second surface S2 (short circuit surface).

  In the example illustrated in FIG. 1, for coupling adjustment, which linearly extends from the third surface S3 to the fourth surface S4 between the positions where the two through holes 2a and 2b of the first surface S1 of the dielectric block 1 are formed. A groove 5 is formed.

The operation of the dielectric filter and its coupling adjusting groove shown in FIG. 1 is as follows.
First, the inner conductors 3a to 3c formed on the inner surfaces of the through holes 2a to 2c act as coaxial resonators together with the outer conductor 4 in the dielectric body of the dielectric block 1, respectively. Since the inner conductors 3a to 3c formed on the inner surfaces of the respective through holes 2a to 2c are relatively close to each other on the first surface S1 (open surface) side, adjacent resonators among the three resonators have capacitances. Sexual coupling. The input / output electrodes 6a and 6c are capacitively coupled to the resonators formed in the portions where the through holes 2a and 2c are formed.

  The coupling adjusting groove 5 reduces the effective dielectric constant between the open surfaces of the inner conductors 3a and 3b, so that the coupling degree between the two resonators formed in the portions where the through holes 2a and 2b are formed. Decreases due to the presence of the coupling adjusting groove 5.

  The effective dielectric constant decreases as the depth and width of the coupling adjusting groove 5 increase. Therefore, the degree of coupling between the two resonators can be adjusted by adjusting the depth or width of the coupling adjusting groove 5.

  FIG. 10 shows a cutting tool used to form the coupling adjusting groove 5. FIG. 10 is a side view of a cutting plate (blade). The cutting tool includes a grinding plate 10 that is rotated at a high speed by a spindle motor, and performs cutting by relatively moving the grinding plate 10 in the y-axis direction in which the coupling adjusting groove 5 shown in FIG. 1 extends. Accordingly, the thickness of the cutting plate 10 determines the width of the coupling adjusting groove 5. Usually, a single type of grinding plate 10 is used, and the coupling degree is adjusted by determining the depth of the coupling adjusting groove 5 with respect to the dielectric block 1.

  At that time, the dielectric filter 100 has an x-axis direction in which the second surface S2 is parallel to the plane of the table and the direction perpendicular to the fifth surface S5 and the sixth surface S6 is the movable direction of the linear table. It arranges on the table so that it becomes. Further, the cutting tool is arranged with respect to the table so that the rotation axis of the spindle motor of the cutting tool shown in FIG. 10 is the x-axis, and the z-axis direction (perpendicular to the first surface S1 and the second surface S2). The cutting tool is moved in the y-axis direction while the position of (direction) is fixed at a predetermined position.

FIG. 11 is a flowchart showing a procedure of a characteristic adjusting method performed using the table and the cutting tool.
First, the filter characteristics of a dielectric filter that is a characteristic adjustment target are measured. When this dielectric filter characteristic adjusting method is applied, the dielectric block 1 already has the inner conductors 3a to 3c, the outer conductor 4, and the input / output electrodes 6a and 6c, and thus acts as a dielectric filter as it is. (There is no need to form a conductor film such as the outer conductor 4 on the inner surface of the coupling adjusting groove 5.) Therefore, a network analyzer probe is connected to the input / output electrodes 6a and 6c to measure the characteristics of the dielectric filter. To do.

  Next, with reference to a database obtained from the result of characteristic adjustment performed in the past, the position and dimension of the coupling adjustment groove 5 are determined. This database is a database of relationships such as the formation position, depth, and width of the coupling adjusting groove 5, the filter characteristics obtained thereby, and the initial characteristics of the filter.

  And it cuts using the above-mentioned cutting tool actually, and measures a filter characteristic again. The database is updated according to the filter characteristics and the positions and dimensions of the actual coupling adjustment grooves.

  If the filter characteristics do not fall within the predetermined characteristic range as a result of this cutting process, the dimension of the coupling adjusting groove (additional cutting amount) is determined again with reference to the database, and the cutting process is performed. This process is repeated as necessary, and the filter characteristic adjustment process ends when the filter characteristic falls within a predetermined characteristic range.

Next, a method for adjusting the characteristics of the dielectric filter according to the second embodiment will be described with reference to FIGS.
In the example shown in FIG. 1, the coupling adjusting groove 5 is formed at a substantially intermediate position between the positions where the through holes 2a and 2b are formed. In the example shown in FIG. 2, the position is overlapped with a part of one of the through holes 2a. A coupling adjusting groove 5 is formed on the surface. The structure of the dielectric filter before characteristic adjustment is the same as that of the first embodiment. By forming the coupling adjusting groove 5, the vicinity of the open end of the inner conductor 3a formed on the inner surface of the through hole 2a is partially deleted. As a result, the effective length of the resonant line length by the inner conductor is shortened and the effective dielectric constant between the vicinity of the open end and the outer conductor 4 is lowered, so that the resonance of the resonator configured at the formation position of the through hole 2a is reduced. The frequency increases. Therefore, the formation of the coupling adjusting groove 5 allows the resonance frequency to be adjusted simultaneously with the adjustment of the degree of coupling between the two resonators formed in the portions where the through holes 2a and 2b are formed.

  In the example shown in FIG. 3, the coupling adjusting groove 5 is formed at a position overlapping with a part of the two through holes 2a and 2b. In this case, it is possible to adjust the resonance frequency of the two resonators at the same time as adjusting the degree of coupling between the two resonators formed in the portions where the two through holes 2a and 2b are formed.

  The characteristic adjusting method as shown in FIGS. 2 and 3 is effective when a sufficient dielectric thickness cannot be secured by forming the coupling adjusting groove 5. For example, when the thickness between adjacent through-holes 2a-2b is 0.6 mm and a cutting plate having a thickness of 0.2 mm is used, the thickness of the dielectric in the uncut portion is slightly smaller in the cutting method shown in FIG. It becomes 0.2 mm, and the part becomes structurally fragile. On the other hand, if the cutting position of the coupling adjusting groove 5 is moved to one of the two through holes as shown in FIG. 2, the thickness of the uncut portion can be increased. Further, as shown in FIG. 3, the uncut portion can be eliminated by forming the coupling adjusting groove 5 so as to partially overlap both the through holes.

Next, a method for adjusting the characteristics of the dielectric filter according to the third embodiment will be described with reference to FIGS.
In the first and second embodiments, the example in which only the coupling adjusting groove is formed in the dielectric filter is shown. In the examples shown in FIGS. 4 and 5, the resonance frequency of the resonator is adjusted. A frequency adjusting groove is also formed.

  4A is a front view of the dielectric filter, and FIG. 4B is a bottom view thereof. The structure of the dielectric filter before the characteristic adjustment is the same as in the first and second embodiments. As shown in the figure, a frequency adjusting groove 7 having a predetermined depth and a predetermined width is formed at a position parallel to the extending direction of the coupling adjusting groove 5 and crossing the through hole 2a. Thus, by providing the frequency adjusting groove 7 narrower than the inner diameter on the open surface (S1) side of the through hole 2a, the effective line length of the resonance line by the inner conductor 3a formed on the inner surface of the through hole 2a is shortened. In addition, since the effective dielectric constant between the vicinity of the open end and the outer conductor 4 decreases, the resonance frequency of the resonator formed in the portion where the through hole 2a is formed increases. Further, even if the frequency adjusting groove 7 is formed, the capacitance in the vicinity of the open end between the inner conductor 3a on the inner surface of the through hole 2a and the inner conductor 3b on the inner surface of the through hole 2b adjacent thereto is hardly changed. The coupling degree between the two resonators is hardly affected. Accordingly, the coupling adjustment and the frequency adjustment can be independently performed by the coupling adjustment groove 5 and the frequency adjustment groove 7.

  In the example shown in FIG. 5, the positions of the coupling adjustment groove 5 and the frequency adjustment groove 7 are determined so that they are adjacent (continuous). By determining the formation positions of the two grooves in this way, as in the case of FIG. 2 and FIG. 3, there is no uncut portion where the thickness of the dielectric portion becomes thin. Applicable even when the thickness is thin.

Next, a method for adjusting the characteristics of the dielectric filter according to the fourth embodiment will be described with reference to FIG.
In the first to third embodiments, the coupling adjusting groove 5 is formed in the entire width from the third surface to the fourth surface of the dielectric block 1, but the length of the coupling adjusting groove 5 is as shown in FIG. Alternatively, the coupling adjusting groove 5 may be formed so as to end in the middle of the width between the third surface S3 and the fourth surface S4 of the dielectric block 1. In that case, the degree of coupling can also be adjusted by the length of the coupling adjusting groove 5 (the dimension in the direction of the third surface S3 to the fourth surface S4 of the dielectric block 1). Therefore, for example, the length of the coupling adjusting groove 5 and the depth thereof are determined by the amount of movement in the y-axis direction while keeping the height in the z-axis direction of the cutting tool shown in FIG. Make adjustments.

  Next, a characteristic adjustment method for a dielectric filter according to a fifth embodiment will be described with reference to FIGS. FIG. 7 is an external perspective view of the dielectric filter, which is arranged in a characteristic adjustment state with the first surface S1 as the upper surface. 8A is a front view, FIG. 8B is a top view, and FIG. 8C is a bottom view.

  In the first to fourth embodiments, the through-holes 2a to 2c formed in the dielectric block 1 are formed so that the center axes of the open end side and the short-circuit end side are coaxial. This fifth embodiment So that is the different axis. Moreover, among the three through holes 2a to 2c, the distance between the central axis on the second surface S2 side of the second through hole 2b and the first through hole 2a, the second through hole 2b, and the third through hole 2c. The distance between the central axes on the second surface S2 side is made different. That is, as shown in FIG. 8A, when this dielectric filter is viewed from the first surface S1, the pair of through holes 2a-2b has a “separate structure”, and the pair of through holes 2b-2c has “Cross-eye structure”.

  A coupling adjustment groove 5ab is formed between the first and second through holes 2a and 2b, and a coupling adjustment groove 5bc is formed between the second and third through holes 2b and 2c.

  By arranging the through holes 2a to 2c having such a different axis structure, the two resonators configured in the formation portions of the through holes 2a and 2b are capacitively coupled to each other. In addition, the two resonators formed in the portions where the through holes 2b and 2c are formed are inductively coupled. Therefore, by forming the first coupling adjusting groove 5ab, the capacitive coupling between the two resonators formed in the through holes 2a and 2b is suppressed, and the coupling degree is lowered. Further, by providing the second coupling adjusting groove 5bc, the capacity in the vicinity of the open end of the two resonators formed in the portions where the through holes 2b and 2c are formed is reduced, and inductive coupling is increased.

  In this way, the coupling degree between adjacent resonators can be reduced by one coupling adjustment groove, and the coupling degree between the resonators can be increased by forming the other coupling adjustment groove. Therefore, the degree of coupling can be adjusted in both directions, and the coupling adjustment range is wide.

  Incidentally, when the adjustment can only be made in the direction of lowering the coupling degree, the dimensions of the dielectric block are designed in advance in consideration of the cutting amount of the coupling adjustment groove, and the coupling adjustment groove is obtained in order to obtain a desired filter characteristic. However, if the coupling degree adjustment direction is in both directions, the cutting amount for coupling adjustment can be reduced. In other words, if the dimensions of the dielectric block are designed so that the desired filter characteristics can be obtained without providing two coupling adjustment grooves, the variation from the design value can be reduced by the two coupling adjustment grooves. It may be corrected. As a result, the cutting amount of the entire coupling adjusting groove can be reduced, the lead time of the characteristic adjusting process can be shortened, and the manufacturing cost can be reduced.

Next, a characteristic adjustment method for a dielectric filter according to a sixth embodiment will be described with reference to FIG.
In the first to fifth embodiments, a single dielectric filter having two input / output electrodes is taken as an example. However, in the sixth embodiment, a common input / output electrode and the other two input / output electrodes are used. This is applied to the provided dielectric duplexer.

  9A is a front view of the dielectric duplexer, FIG. 9B is a bottom view, and FIG. 9C is a rear view. As shown in this figure, the substantially rectangular parallelepiped dielectric block 1 has six through holes 2a to 2f penetrating between the first surface S1 and the second surface S2, and the first surface S1 and the second surface S2. They are arranged in a row in a direction parallel to the third surface S3 and the fourth surface S4 perpendicular to the surface S2. Inner conductors are formed on the inner surfaces of these through holes 2a to 2f, respectively. On the other five surfaces S2 to S6 excluding the first surface S1 of the dielectric block 1, the outer conductor 4 is formed on almost the entire surface.

  Between the first surface S1 and the second surface S2 of the dielectric block 1, excitation holes 8 other than the six through holes 2a to 2f are formed. An inner conductor is formed on the inner surface of the excitation hole 8. On the first surface S1 of the dielectric block 1, an outer conductor 4 that is electrically connected to the inner conductor of the excitation hole 8 is partially formed. An input / output electrode 9 is formed separately from the outer conductor 4 from the second surface to the fourth surface of the excitation hole 8.

  With such a structure, one filter is constituted by three resonators formed in the formation portions of the three through holes 2a to 2c. Similarly, another filter is constituted by three resonators formed in the portions where the through holes 2d to 2f are formed. The resonator formed by the through hole 2a is capacitively coupled to the input / output electrode 6a. Similarly, the resonator formed by the through hole 2f is capacitively coupled to the input / output electrode 6f. The excitation hole 8 is interdigitally coupled to the respective resonators formed by the through holes 2c and 2d.

  With this structure, the former filter is a transmission filter, the latter filter is a reception filter, the input / output electrode 6a is a transmission signal input terminal, the input / output electrode 6f is a reception signal output terminal, and the input / output electrode 9 is an antenna terminal. Acts as a duplexer.

  In the example shown in FIG. 9, the coupling adjustment groove 5ab is formed in the middle of the formation positions of the through holes 2a and 2b, and the coupling adjustment groove 5bc is partially overlapped with the through hole 2b between the through holes 2b and 2c. Is forming. A coupling adjusting groove 5de is formed between the through holes 2d-2e and at a position overlapping with a part of the through hole 2d. Further, a frequency adjusting groove 7 is formed at a position crossing the through hole 2f. Each of these various grooves extends linearly from the third surface S3 of the dielectric block 1 to the fourth surface S4 direction on the first surface S1, and therefore can be formed in the same process using the same cutting tool. A dielectric duplexer having desired filter characteristics can be easily obtained.

Three views of the dielectric filter according to the first embodiment Two views of a dielectric filter according to a second embodiment Two views of another dielectric filter according to the second embodiment Two views of a dielectric filter according to a third embodiment Two views of another dielectric filter according to the third embodiment Two views of a dielectric filter according to a fourth embodiment External perspective view of a dielectric filter according to a fifth embodiment Three views of the same dielectric filter Three views of a dielectric duplexer according to a sixth embodiment External view of cutting tool used in each embodiment Flow chart showing the characteristic adjustment procedure in each embodiment

Explanation of symbols

1-dielectric block 2-through hole 3-inner conductor 4-outer conductor 5-coupling adjusting groove 6-input / output electrode 7-frequency adjusting groove 8-excitation hole 9-input / output electrode 10-grinding plate 100-dielectric Body filter S1-S6-first side-sixth side

Claims (4)

A substantially rectangular parallelepiped having a plurality of through holes arranged in rows in a direction parallel to the third and fourth surfaces that pass through between the first and second surfaces facing each other and orthogonal to the first and second surfaces A dielectric filter characteristic adjustment method comprising: a dielectric block having a shape; an inner conductor formed on an inner surface of the through hole; and an outer conductor formed on the other five surfaces excluding the first surface of the dielectric block. There,
In a state where the inner conductor and the outer conductor are already formed, the first surface of the dielectric block extends linearly from the third surface to the fourth surface between two adjacent through hole forming positions. The coupling adjusting groove is formed, and the coupling degree between the two resonators configured in the two through-hole forming portions is adjusted according to the depth, width, or length of the coupling adjusting groove. A method for adjusting the characteristics of a dielectric filter.   The dielectric filter characteristic adjusting method according to claim 1, wherein the coupling adjusting groove is formed at a position overlapping with a part of one or both of the two through holes.   A frequency adjusting groove different from the coupling adjusting groove is formed at a position parallel to the extending direction of the coupling adjusting groove and crossing the through hole, and a through hole formed by the frequency adjusting groove is crossed. The method for adjusting characteristics of a dielectric filter according to claim 1 or 2, wherein the resonance frequency of the resonator formed in the portion is adjusted.   The through hole has a step structure in which an inner diameter on the first surface side is larger than an inner diameter on the second surface side, and among the three first, second, and third through holes that are continuous, The distance between the central axes on the second surface side of the first through hole is different from the distance between the central axes on the second surface side of the second through hole and the third through hole, and the first and second 4. The dielectric according to claim 1, wherein the filter characteristics are adjusted by both the coupling adjusting groove between the through holes and the coupling adjusting groove between the second and third through holes. Body filter characteristic adjustment method.

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