JPH05152804A - Dielectric filter and adjustment method of its frequency characteristic - Google Patents

Abstract

PURPOSE:To improve the characteristic of the dielectric filter without incurring the large sized filter and increasing the number of components by incorporating a coupling electrode coupling electrically each resonator electrode. CONSTITUTION:Resonator electrodes 18 adjacent to each other and coupling electrodes 22 coupling the electrodes 18 are formed separately to the dielectric filter 28 and they are formed on a separate dielectric board. The resonator electrode 18 is formed on a 1st dielectric board 30, one terminal is short- circuited to a ground conductor 14 and the other terminal is exposed externally. On the other hand, the coupling electrode 22 is formed on a 2nd dielectric board 32 at a position corresponding to the open terminal of each resonator electrode 18 formed on the 1st dielectric board 30 respectively. Then the dielectric boards 30, 32 of the dielectric filter 28 are laminated and they are integrated by baking.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric filter used in a microwave band and a method of adjusting its frequency characteristic, and particularly to a structure of a dielectric filter which is compact and can exhibit excellent filter characteristics, and the dielectric material. The present invention relates to a method for easily adjusting the frequency characteristic of a filter.

[0002]

2. Description of the Related Art In recent years, filters using various dielectric ceramics have been used in communication devices using microwaves, such as mobile phones and car phones, in order to reduce loss. And, in the past, a coaxial resonator was used in which the inner peripheral surface of a dielectric block having a through hole formed in the center was metallized to form a central conductor corresponding to the resonator, and a plurality of these resonators were combined. The dielectric filter configured as above was used. However, in the dielectric filter having such a structure, due to the through holes, there is a limit to the thinning and miniaturization of the filter, and since the number of parts is large, the assembly process is troublesome and complicated. There was also an inherent problem.

On the other hand, for example, JP-A-59-51.
As disclosed in Japanese Patent No. 606, the tri-plate type dielectric filter having a laminated structure has the above-mentioned problems, can be significantly thinned, and does not require troublesome assembly. It recognized. 12 and 1
3 shows an example of a dielectric filter having such a structure. That is, the dielectric filter 2 shown there
Inside the dielectric substrate 6, the input / output electrode 3 and a plurality of stripline type resonator electrodes 4 (here, three) are incorporated in a pattern as shown in FIG. The ground conductor 8 and the input / output terminals 10 corresponding to the input / output electrodes 3 are provided on the outer peripheral surface, and can be made extremely compact.

In the conventional tri-plate type dielectric filter 2, the coupling length between the resonators is adjusted by the arrangement of the resonator electrodes 4 having the comb line structure or the interdigital structure as shown in FIG. Then, a desired filter characteristic is obtained, and a coupling circuit for electrically coupling the resonator electrodes 4 to each other is not included. However, the characteristics required for recent microwave filters are much more severe, and it is no longer possible to support them with simple combline structures or interdigital structures, and a coupling circuit that couples each resonator with a capacitance is required. Is coming.

Further, conventionally, in order to finally finely adjust the frequency characteristic of the dielectric filter 2 to a desired value, a portion of the ground conductor 8 corresponding to the portion in which the resonator electrode 4 is built, , The short-circuited end of the resonator electrode 4 (the side connected to the ground conductor 8) was trimmed, but since the position of the resonator electrode 4 built in the dielectric substrate 6 is difficult to know accurately, this work is performed. Was a hassle.

[0006]

[Means for Solving the Problems] The present invention has been made in view of such circumstances, and the problem to be solved is to increase the size of the dielectric filter and the number of parts in a dielectric filter having a triplate structure. It is to advantageously improve the filter characteristics without causing an increase in Another object is to facilitate the work when adjusting the frequency characteristics of the dielectric filter.

[0007]

The present invention has been made to solve the above problems, and the gist of the present invention is to provide a triplate structure having a plurality of resonator electrodes built in a dielectric substrate. In the dielectric filter, a coupling electrode for electrically coupling the resonator electrodes to each other through a predetermined coupling capacitance is further incorporated in the dielectric substrate.

In the present invention, the resonator electrode is formed so as to form a TEM mode stripline type resonance circuit of 1/4 or 1/2 wavelength, and the open end thereof is exposed to the outside. The dielectric filter having the above structure is advantageously realized.

Further, in the dielectric filter according to the present invention, the ground conductor is provided over substantially the entire upper surface and the lower surface of the dielectric substrate, and the ground conductors on the upper surface and the lower surface are electrically connected to each other. On one side surface of the dielectric substrate which is exposed and the open end of the resonator electrode is exposed, a strip-shaped ground conductor having a predetermined width is vertically arranged so as not to come into contact with the exposed portion of the resonator electrode. It is provided so as to extend, and the band-shaped ground conductor is used to
A structure in which the ground conductor on the lower surface is electrically connected is advantageously adopted.

Further, in the present invention, in the dielectric filter having such a structure, it is advantageous to adjust the resonance frequency of each corresponding resonance circuit by trimming the open end of the resonator electrode. Will be done.

[0011]

Concrete Structure The structure of the dielectric filter according to the present invention and the method of adjusting the frequency characteristic thereof will be specifically described below with reference to the drawings.

First, FIGS. 1 and 2 show an example of a dielectric filter having a triplate structure according to the present invention. There, a ground conductor 14 is provided on substantially the entire surface of the dielectric filter 12, and in a state where the ground conductor 14 is not electrically connected to the ground conductor 14, on two opposite side surfaces of the dielectric filter 12, A pair of input / output terminals 1
6 is provided. Inside the resonator electrode 18, the input / output electrode 20, and further, the coupling electrode 2 is provided.
2, 26 are built in.

That is, such a dielectric filter 1
2 can be manufactured according to a normal manufacturing method of a laminated substrate, and three resonator electrodes 18 are formed on one of the dielectric substrates 24 in the pattern shown in FIG. A pair of input / output electrodes 20 are formed at positions corresponding to the input / output terminals 16 with the three resonator electrodes 18 interposed therebetween. Here, 3
The resonator electrodes 18 of the book are arranged in a combline structure, and three resonators corresponding to the resonator electrodes 18 are formed. Then, each resonator electrode 18
Has one end serving as a short-circuited end connected to the ground conductor 14 on the side surface of the dielectric substrate 24, and the other end located at a position about 1/4 of the opposite side surface of the dielectric substrate 24. , It is an open end housed inside the substrate.

At the open end of the resonator electrode 18, the coupling electrode 22 is integrally formed as a continuous conductor pattern in a form of being bent and extended toward the adjacent resonator electrode 18. It has been formed. Therefore, in this dielectric filter 12, the coupling electrode 2
By adjusting the capacitance between 2 and 22, the coupling amount between the resonators can be adjusted advantageously.
Therefore, it is possible to bring out excellent filter characteristics that cannot be obtained by the conventional dielectric filter.

Further, here, a U-shaped coupling electrode 26 for coupling the resonator electrodes 18 located at both ends is further provided on the open end side of the resonator electrode 18, and the coupling electrode 26 is provided. By adjusting the capacitance between the coupling electrode 26 and the resonator electrodes 18, 18 at both ends, the amount of coupling between the resonators at both ends can be adjusted. By thus coupling the resonator electrodes 18, 18 at both ends, the frequency characteristic of the dielectric filter 12 can be advantageously enhanced.

That is, in the dielectric filter 12, since the coupling electrodes 22 and 26 are provided, it is possible to sufficiently meet strict characteristic requirements, and moreover, the coupling electrodes 22 and 26 are also provided. Is built in the dielectric substrate 24 together with the resonator electrode 18, the thin and small dielectric filter 12 can be advantageously realized, and the filter does not become large or complicated. Of. In addition, the resonator electrodes 18 and 1 at both ends
The coupling electrode 26 for coupling 8 is not necessarily required in the present invention.

Next, another example of the triplate-structured dielectric filter according to the present invention will be described with reference to FIGS. The dielectric filter 28 shown there is
Except for one side (front side in FIG. 3) of the built-in resonator electrode 18, which is on the open end side, substantially the entire surface is covered with the ground conductor 14, and the upper surface thereof is electrically connected to the ground conductor 14. A pair of input / output terminals 16 are formed in a state of not being connected to. The open end of the resonator electrode 18 built in the dielectric substrate (30, 32) is exposed on the surface where the ground conductor 14 is not provided.

In this dielectric filter 28, the coupling electrodes 22 for coupling the adjacent resonator electrodes 18 and 18 are formed separately and formed on different dielectric substrates. Among them, the resonator electrode 18
Is formed on the first dielectric substrate 30 and has one end short-circuited to the ground conductor 14 as shown in FIG.
The other end is exposed to the outside as described above. on the other hand,
The coupling electrode 22 is formed on the second dielectric substrate 32, and, as shown in FIG. 5, at the open end of each resonator electrode 18 formed on the first dielectric substrate 30. It is formed in each of the corresponding portions. Then, the dielectric filter 28 includes the first and second dielectric substrates 30 and 3
The two are laminated and integrated by firing to be configured.

As a result, as is apparent from FIG. 6 showing the broken line section of the dielectric filter 28 in FIGS. 4 and 5 and FIG. 7 showing the equivalent circuit thereof, the adjacent resonators 3 are arranged.
The four components are coupled to each other via a capacitance 36 between the resonator electrode 18 and the coupling electrode 22 and a capacitance 38 between the coupling electrodes 22 and 22, and the capacitances 36 and 38 are appropriately adjusted. As a result, the coupling amount between the resonators 34 can be adjusted. Therefore, even with such a configuration, excellent filter characteristics can be obtained, and the coupling electrode 22 can be formed by the dielectric substrate 30,
Since it is built in 32, the dielectric filter 28 having a small size and a simple structure can be advantageously realized.

Further, by forming the coupling electrodes 22 in multiple layers in this way, it is possible to increase the degree of freedom in design and also possible to design a complicated coupling circuit. Here, the coupling electrodes 22 at both ends also serve as input / output electrodes, and a capacitance 40 is formed between the input / output electrode (20) and the input / output terminal 16 to provide a coupling capacitance for input / output. Adjustments can be made advantageously.

In addition, in the dielectric filter 28 having such a structure, the resonator electrode 18 exposed to the outside is provided.
Since the frequency characteristic can be easily and finely adjusted by trimming the open end of the above, there is also an advantage that such work becomes accurate and simple and the workability is improved.

Next, still another example of the triplate-structured dielectric filter according to the present invention will be described with reference to FIGS. Dielectric filter 4 shown there
2 has substantially the entire surface covered with the ground conductor 14 except a part of one side surface (front surface in FIG. 8) corresponding to the open end side of the built-in resonator electrode 18, and on the other side surface, Similar to the previous example, a pair of input / output terminals 16 are formed in a state of not being electrically connected to the ground conductor 14. The open end of the resonator electrode 18 built in the dielectric substrate (44, 46, 48, 50) is exposed on the surface where the ground conductor 14 is not provided.

In this dielectric filter 42, the coupling electrodes 22 for coupling the adjacent resonator electrodes 18 and 18 are separately formed and are respectively formed on different dielectric substrates. Among them, the resonator electrode 18
Is formed on the third dielectric substrate 48, one end of which is short-circuited to the ground conductor 14 and the other end is exposed to the outside as described above, as shown in FIG. On the other hand, the coupling electrode 22 is formed on the second dielectric substrate 46, and, as shown in FIG. 9, each of the resonator electrodes 18 formed on the third dielectric substrate 48. Each is formed at a portion corresponding to the open end. Then, the dielectric filter 42 includes the first to fourth dielectric substrates 44, 4
6, 48, and 50 are laminated and integrated by firing.

As a result, as is clear from FIG. 10 which shows the equivalent circuit of the dielectric filter 42 in FIGS. 8 and 9, the adjacent resonators 34 are separated from each other by the resonator electrode 18.
The capacitors 36 and 36 are coupled to each other via the coupling electrode 22, and the coupling amount between the resonators 34 can be adjusted by appropriately adjusting the respective capacitances 36. It is like this.

The dielectric filter 42 of this embodiment is also used.
In the above, one side surface (end surface) of the dielectric substrate (44, 46, 48, 50) corresponding to the open end side of the resonator electrode 18
8, a strip-shaped ground conductor 14a for connecting the ground conductors 14 provided on the upper surface and the lower surface of the dielectric substrate is provided so as to be located between the open ends of the resonator electrode 18. Has been. Due to the existence of the band-shaped ground conductor 14a, it is possible to effectively eliminate the difference in the ground potential between the ground conductor 14 on the upper surface and the ground conductor 14 on the lower surface, thereby stabilizing the filter characteristics. Exert the characteristic that

Further, due to the capacitance 52 formed between the portion near the open end side of the resonator electrode 18 and the strip-shaped ground conductor 14a formed on one side surface of the dielectric substrate, resonance occurs at the resonance frequency. The instrument electrode 18 is inductive, so that inductive coupling M occurs between the resonators 34. In this way, each resonator 34 has a capacitance 36
Since the coupling (capacitive coupling) and the inductive coupling M are generated, the amount of attenuation on the lower frequency side than the pass band of the filter can be made large, and the frequency separation characteristic can be improved as shown in FIG. .. In addition, due to the presence of the capacitance 52, the length of the resonator 34 can be shortened at the same resonance frequency as compared with the case where the capacitance 52 is not present, which can also contribute to downsizing of the filter. ..

In the dielectric filter 28 having such a structure, the open end of the resonator electrode 18 exposed to the outside is trimmed as in the previous example.
Since the frequency characteristics can be easily fine-tuned,
There is also an advantage that such work becomes accurate and simple and the workability is improved.

By the way, in the present invention, the resonator electrode 18 is used.
And the coupling electrode 22, the dielectric substrate 24 (30, 32;
44, 46, 48, 50), it is desirable to use a conductor having a low specific resistance for the conductors forming these electrodes because they are completely incorporated. Because the loss in the electrode increases the loss in the pass band of the filter,
In particular, when dealing with electromagnetic waves in the microwave band, the resistance of the conductor of the coupling circuit needs to be low.
It is preferable to use a g-based or Cu-based conductor.

Therefore, when Ag-based or Cu-based conductors are used, the melting points of these conductors are low, and it is difficult to co-fire with a usual dielectric material. It is necessary to use a dielectric material that can be fired at a temperature below 1100 ° C.). Also, due to the characteristics of the device as a microwave filter, the temperature characteristic (temperature coefficient) of the resonance frequency of the formed resonance circuit is ± 50 ppm.
A dielectric material having a temperature of / ° C or less is preferable. Examples of such a dielectric material include glass-based materials such as a mixture of cordierite-based glass powder, TiO ₂ powder and Nd ₂ Ti ₂ O ₇ powder, and BaO—TiO ₂ —RE ₂
O ₃ -Bi ₂ O ₃ based composition: the (RE rare earth component) is obtained by adding a small amount of glass forming component or glass powder.

[0030]

EXAMPLES Hereinafter, representative examples of the present invention will be shown to clarify the present invention in more detail. However, the present invention is not limited by the description of such examples. Needless to say, it is not something to receive. Further, in addition to the following specific examples, in addition to the following embodiments, the present invention includes various modifications based on the knowledge of those skilled in the art without departing from the spirit of the present invention.
It should be understood that modifications, improvements, etc. may be made.

Example 1 MgO: 18 wt% -Al ₂ O ₃ : 37 wt% -SiO
_{2: 37wt% -B 2 O 3} : 5wt% -TiO 2: 3w
73% by weight of glass powder having a composition of t% and commercially available Ti
17 wt% of O ₂ powder and 10 of Nd ₂ Ti ₂ O ₇ powder
wt% was thoroughly mixed to obtain a mixed powder. Note that Nd ₂
Ti ₂ O ₇ powder consists of Nd ₂ O ₃ powder and TiO ₂ powder.
A product obtained by calcination at 200 ° C. and crushing was used.
Then, to this mixed powder, an acrylic organic binder,
A plasticizer, toluene, and an alcohol-based solvent were added, and the mixture was thoroughly mixed with alumina cobblestone to form a slurry. Then, using this slurry, a doctor blade method of
A green tape having a thickness of 2 mm to 0.5 mm was produced.

On the other hand, Ag-based powder, acrylic organic binder and terpineol-based organic solvent were well kneaded by a three-roller to obtain a conductor paste for printing. Then, using this conductor paste, the wiring pattern shown in FIG. 2 and the ground conductors on the two upper and lower surfaces were printed on the green tape. Next, after stacking the green tapes on which these conductor patterns are printed in a predetermined order, 100
The layers were integrated under a condition of ℃ and 100 kg / cm ² . After stacking
This laminated body was cut, and the side surface ground conductor was printed so as to connect the input / output terminals and the upper and lower ground conductors to the side surface (cut surface) to obtain a filter precursor having the structure shown in FIG. After that, the filter precursor was fired in the atmosphere at 900 ° C. for 30 minutes to obtain a thin microwave filter having a total thickness of 2 mm.

The characteristics of this filter were as follows: 900 MHz band, bandwidth: 20 MHz, insertion loss: 3 dB. Further, a sintered body of the mixed powder was produced, and after being ground to a predetermined size, the temperature characteristic (temperature coefficient) of the resonance frequency in the microwave band was measured by the parallel conductor plate resonator method. + 10ppm / ℃ between -25 ℃ and + 75 ℃
Met.

Example 2 MgO: 17 wt% -Al ₂ O ₃ : 37 wt% -SiO
_{2: 37wt% -B 2 O 3} : 5wt% -TiO 2: 3w
73% of glass powder having a composition of t% -MnO: 1 wt%
t%, 17 wt% of TiO ₂ powder, Nd ₂ Ti ₂ O
10 wt% of the ₇ powders were thoroughly mixed to obtain a mixed powder. The TiO ₂ powder used was obtained by mixing commercially available TiO ₂ and 1 wt% of MnO, calcining it at 1200 ° C., and then pulverizing it. Further, the Nd ₂ Ti ₂ O ₇ powder was Nd ₂ Ti ₂ O ₇ powder. ₂ O ₃ powder, TiO ₂ powder and 1 wt% Mn
It was obtained by mixing O, calcining at 1200 ° C., and then pulverizing.

Next, an acrylic organic binder, a plasticizer, toluene and an alcohol solvent were added to this mixed powder, and the mixture was thoroughly mixed with alumina cobblestone to form a slurry. Then, using this slurry, a green tape having a thickness of 0.2 mm to 0.5 mm was prepared by a doctor blade method.

On the other hand, Cu-based powder, acrylic organic binder and terpineol-based organic solvent were well kneaded by a three-roller to obtain a conductive paste for printing. Then, using this conductor paste, the wiring pattern shown in FIG. 2 and the ground conductors on the two upper and lower surfaces were printed on the green tape. Then, in the same manner as in Example 1, green tapes were laminated and integrated. Then, the obtained laminated body was cut, and the ground conductor on the side surface was printed so as to connect the input / output terminals and the upper and lower ground conductors to obtain a filter precursor having a structure shown in FIG. After that, this filter precursor was fired under a nitrogen atmosphere at 950 ° C. for 30 minutes to obtain a thin microwave filter having a total thickness of 2 mm. The characteristics of this filter are 9
At 00MHz band, bandwidth: 30MHz, insertion loss: 3.5d
It was B.

Example 3 On the green tape produced in Example 1, only the wiring pattern shown in FIG. 2 was printed with Ag paste, and a laminate was obtained in the same manner as in Example 1. Then, in the obtained laminated body,
The ground conductor and the input / output terminals were printed using a commercially available Cu paste to obtain a filter precursor having the structure shown in FIG.
Then, it was fired at 600 ° C. in an air atmosphere to obtain a thin microwave filter having a total thickness of 2 mm. The characteristics of this filter are 900MHz band, bandwidth: 20MH
z, insertion loss: 3 dB.

Example 4 A low melting glass powder and a low melting metal oxide powder were added to a powder having a composition of BaO—TiO ₂ —Nd ₂ O ₃ —Bi ₂ O ₃ system so that the total amount thereof was 8 wt%. Then, a mixed powder was prepared. Next, an acrylic organic binder, a plasticizer, toluene and an alcohol solvent were added to this mixed powder, and the mixture was sufficiently mixed with alumina boulders to obtain a slurry. Then, using this slurry, a green tape having a thickness of 0.2 mm to 0.5 mm was prepared by a doctor blade method.

On the other hand, Ag-based powder, acrylic organic binder and terpineol-based organic solvent were well kneaded by a three-roller to obtain a conductor paste for printing. Using this conductor paste, the wiring patterns shown in FIGS. 4 and 5 and the upper and lower two-sided ground conductors and input / output terminal portions as shown in FIG. 3 were printed on the green tape. Next, after stacking the green tapes with these conductor patterns printed in a predetermined order, 100 ℃, 100kg
The layers were integrated under the condition of / cm ² . After the lamination, the laminated body was cut, and the side surface ground conductor was printed so as to connect the input / output terminal portions and the upper and lower ground conductors to the side surface (cut surface) to obtain the structure shown in FIG. After that, it is baked in the atmosphere at 900 ° C. for 30 minutes, and the total thickness is 2
A thin microwave filter of mm was obtained.

The characteristics of this filter were that the bandwidth was 900 MHz, the bandwidth was 20 MHz, and the insertion loss was 3 dB. Also,
After producing a sintered body of the mixed powder and polishing it to a predetermined size, the temperature characteristic (temperature coefficient) of the resonance frequency in the microwave band was measured by the parallel conductor plate resonator method. It was +15 ppm / ° C between 0 ° C and + 75 ° C. At this time, the fine adjustment of the frequency characteristic was performed by trimming the open end exposed to the outside of the resonator electrode (see FIG. 3).

Example 5 A low melting glass powder and a low melting metal oxide powder were added to a powder having a composition of BaO—TiO ₂ —Nd ₂ O ₃ —Bi ₂ O ₃ system so that the total amount thereof was 8 wt%. Then, a mixed powder was prepared. Next, an acrylic organic binder, a plasticizer, toluene and an alcohol solvent were added to this mixed powder, and the mixture was sufficiently mixed with alumina boulders to obtain a slurry. Then, using this slurry, a green tape having a thickness of 0.2 mm to 0.5 mm was prepared by a doctor blade method.

On the other hand, Ag-based powder, acrylic organic binder and terpineol-based organic solvent were well kneaded by a three-roller to obtain a conductor paste for printing. Using this conductor paste, the wiring patterns shown in FIGS. 8 and 9 and the ground conductors and the input / output terminal portions on the two upper and lower surfaces were printed on the green tape. Next, the green tapes on which these conductor patterns were printed were stacked in a predetermined order, and then laminated and integrated under conditions of 100 ° C. and 100 kg / cm ² . After the lamination, this laminated body was cut, and the side surface ground conductor was printed so as to connect the input / output terminal portions and the upper and lower ground conductors to the side surface (cut surface) to obtain the structure shown in FIG. After that, in an air atmosphere, 900 ° C,
Firing was performed for 30 minutes to obtain a thin microwave filter having a total thickness of 2 mm.

The characteristics of this filter were a bandwidth of 20 MHz in the 900 MHz band and an insertion loss of 3 dB. Also,
After producing a sintered body of the mixed powder and polishing it to a predetermined size, the temperature characteristic (temperature coefficient) of the resonance frequency in the microwave band was measured by the parallel conductor plate resonator method. It was +15 ppm / ° C between 0 ° C and + 75 ° C. At this time, the fine adjustment of the frequency characteristic was performed by trimming the open end exposed to the outside of the resonator electrode (see FIG. 8).

[0044]

As is apparent from the above description, in the present invention, in the dielectric filter having the triplate structure,
By incorporating a coupling electrode for adjusting the coupling amount between the resonator electrodes, excellent filter characteristics can be obtained, and the filter does not become large or complicated. Then, in such a dielectric filter, when the open end of the resonator electrode is exposed to the outside, fine adjustment of the frequency characteristic can be extremely easily performed by trimming the open end. The property is improved.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a dielectric filter according to the present invention.

FIG. 2 is a plan sectional view of the dielectric filter shown in FIG.

FIG. 3 is a perspective view showing another example of the dielectric filter according to the present invention.

FIG. 4 is a plan view showing a first dielectric substrate of the dielectric filter shown in FIG.

5 is a plan view showing a second dielectric substrate of the dielectric filter shown in FIG.

FIG. 6 is a cross-sectional view of a broken line portion of the dielectric filter shown in FIG.

7 is a diagram showing an equivalent circuit of the dielectric filter shown in FIG.

FIG. 8 is a perspective view showing still another example of the dielectric filter according to the present invention.

9 is an exploded perspective view of the dielectric filter shown in FIG.

10 is a diagram showing an equivalent circuit of the dielectric filter shown in FIG.

FIG. 11 is a graph showing the relationship between frequency and attenuation in a dielectric filter.

FIG. 12 is a perspective view showing an example of a conventional dielectric filter.

13 is a plan sectional view of the dielectric filter shown in FIG.

[Explanation of symbols]

 12 Dielectric Filter 14 Earth Conductor 14a Band-shaped Earth Conductor 16 Input / Output Terminal 18 Resonator Electrode 20 Input / Output Electrode 22 Coupling Electrode 24 Dielectric Substrate 26 Coupling Electrode 28 Dielectric Filter 30 First Dielectric Substrate 32 Second Dielectric Substrate 34 Resonator 42 Dielectric Filter 44 First Dielectric Substrate 46 Second Dielectric Substrate 48 Third Dielectric Substrate 50 Fourth Dielectric Substrate

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01P 5/08 H 8941-5J 11/00 G

Claims (4)

[Claims] 1. A dielectric filter having a triplate structure in which a plurality of resonator electrodes are built in a dielectric substrate, wherein the resonator electrodes are electrically coupled to each other via a predetermined coupling capacitance. A dielectric filter characterized by further incorporating a coupling electrode. 2. The resonator electrode is 1/4 or 1/2.
2. The dielectric filter according to claim 1, wherein the dielectric filter is formed so as to form a TEM mode stripline type resonance circuit having a wavelength, and its open end is exposed to the outside. 3. A ground conductor is provided over substantially the entire upper surface and lower surface of the dielectric substrate, and the ground conductors on the upper surface and the lower surface are electrically connected to each other.
On one side surface of the dielectric substrate where the open end of the resonator electrode is exposed, a strip-shaped ground conductor having a predetermined width is provided so as to extend in the vertical direction so as not to contact the exposed portion of the resonator electrode, The dielectric filter according to claim 1 or 2, wherein the upper and lower ground conductors are electrically connected by the band-shaped ground conductor. 4. The dielectric filter according to claim 2 or 3, wherein the resonance frequency of each corresponding resonance circuit is adjusted by trimming the open end of the resonator electrode exposed to the outside. A method of adjusting frequency characteristics of a dielectric filter characterized by the above.