JPH0878906A - Dielectric filter - Google Patents

Abstract

PURPOSE: To widen a band, to provide satisfactory input / output characteristics and to facilitate its manufacture. CONSTITUTION: Concerning the dielectric filter, the characteristic impedance of resonators 31-35 consisting of the filter is set lower than the characteristic impedance of an external circuit (lower than 50Ω, for example,) so that the resonators can be easily manufactured even in the case of a wide band filter. Besides, by providing impedance transformers 61 and 62 between an input terminal 51, output terminal 52 and the resonators, the input/output impedance is matched with the characteristic impedance of the external circuit and the satisfactory input/output characteristics can be provided.

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, for example, a receiver of a satellite broadcasting system, having a wide band pass band and having improved insertion loss and reflection loss in the pass band. Is.

[0002]

2. Description of the Related Art Conventionally, a broadband filter of this type has been
There was a coaxial filter using a coaxial line. However, a dielectric filter using a dielectric has come into widespread use for reasons such as easy miniaturization and easy connection with a semiconductor element. Figure 8 shows the Technical Report of the Institute of Electrical Engineers of Japan
Part II-432 (1992) page 13
It is a block diagram which shows the interdigital type dielectric filter using the conventional dielectric material, (a) is a horizontal sectional view,
(B) is sectional drawing in the bb line | wire of (a), (c) is a perspective view, (d) is a figure explaining the relationship of the characteristic impedance inside and outside a filter. 8 (a), (b),
In (c), 10 is a rectangular parallelepiped dielectric block made of a dielectric material, 21 and 22 are ground conductors provided on the surfaces of the dielectric blocks facing each other, 41 to 45 are the ground conductors 21, 22 is a conductor for connecting. 31-
Reference numeral 35 denotes a resonator having one end connected to each of the conductors 41 to 45, and the other end having an open portion that is in an open state. The resonator 35 is electrically coupled to each other, and is connected to the surface of the dielectric block 10. The strip lines are provided inside the dielectric block 10 so as to be parallel and parallel to each other, and have strip lines having an electrical length of ¼ wavelength.
The positions of the short circuit portion and the open portion of the resonators 31 to 35 are reversed in the adjacent resonators. Reference numerals 51 and 52 denote input terminals and output terminals respectively connected to open portions of the resonators 31 and 35 located at both ends of the resonators 31 to 35.

In such an interdigital dielectric filter, at the resonance frequencies of the resonators 31 to 35, the resonators 31 to 35 are strongly coupled to each other, and the incident wave input from the input terminal 51 is , To the output terminal 52. However, at frequencies other than the resonance frequency, the coupling between the resonators 31 to 35 is very weak,
Most of the power of the incident wave on the input terminal 51 is reflected. Thus, the dielectric filter shown in FIG. 8 has a function as a bandpass filter. Here, the center frequency Fc of the pass band of the filter is determined by the resonators 31 to 31.
The pass band width B of the filter is determined by the resonance frequency of the resonators 31 to 35, which is determined by the length L of
It is determined by the coupling coefficient between the resonators 31 to 35, which is determined by the distance P between the resonators 31 to 35. Further, the characteristic impedance Zi of the filter viewed from the input terminal 51 and the output terminal 52 side is the resonator 31 to
The resonators 31 to 35 that are determined by the inner conductor width W of 35.
Of the characteristic impedance and the coupling coefficient between the resonators 31 to 35. The above relationship is described in G.
Matthaei et al., "MICROWAVE FILT
ERS, IMPEDANCE-MATCHING NE
TWORKS, AND COUPLING STRUC
TURES "P. 614-625, 1964, McGr
aw-Hi11. Etc. Also, FIG.
As shown in (d), the characteristic impedance Zi of this filter is as follows when the filter is connected to an external circuit.
The filter impedance is set to match the characteristic impedance Zo of the external circuit so that the filter characteristic does not deteriorate. The characteristic impedance Zo of this external circuit is generally UHF, VH.
50Ω is often used in the F and microwave bands, and will be described as 50Ω in the following description.

[0004]

In such a dielectric filter having the conventional structure, a wide band pass characteristic is realized and the characteristic impedance of the filter is matched with the characteristic impedance of the external circuit (= 50Ω). In such a case, it is necessary to increase the characteristic impedance of the resonators 31 to 35 and increase the coupling coefficient between the resonators 31 to 35. Therefore, the resonators 31 to 3 are
5 by reducing the inner conductor width W.
It is necessary to increase the coupling coefficient between the resonators 31 to 35 by making the characteristic impedance of 35 high impedance and reducing the interval P between the resonators 31 to 35. By the way, in order to widen the band of the filter, for example, in the filter used in the intermediate frequency band of the receiver of the recent satellite broadcasting system, the ratio band (= pass bandwidth / center frequency) needs to be 30% or more due to the increase in the number of broadcasting channels. In addition, a dielectric material having a high relative dielectric constant of 20 or more has been required due to the demand for miniaturization of the device. However, when an attempt is made to realize a wide band filter using such a high dielectric constant dielectric material, the inner conductor width W of the resonators 31 to 35 and the interval P between the resonators 31 to 35 become smaller. There is a problem that it becomes small and its manufacture becomes difficult, and in the worst case, the design itself cannot be performed. For example, relative permittivity 3
Zi = 50Ω, specific bandwidth 30% using 9.5 dielectric
In the case of the filter of No. 2, if it is designed according to the above-mentioned document, the inner conductor width W of the resonator and the interval P between the resonators become negative values, which makes it physically impossible to realize.

The present invention has been made to solve the above problems, and in the dielectric filter, the characteristic impedance of the filter as viewed from the input terminal and output terminal sides is set to be equal to or less than the characteristic impedance of the external circuit. As a result, even in the case of a wide band filter having a relative bandwidth of more than 30%, the inner conductor width of the resonator and the distance between the resonators can be increased to a manufacturable level. Further, by providing an impedance transformer between the input terminal and the output terminal and the resonator, a wide band pass characteristic is realized and the input and output reflection loss and insertion loss are improved.

[0006]

In the dielectric filter according to the present invention, the characteristic impedance of the filter as seen from the input terminal and output terminal sides is the characteristic impedance of the external circuit connected to the input terminal and the output terminal. It is a lower version.

Further, the characteristic impedance of the filter as viewed from the input terminal and the output terminal is set to 50Ω or less.

A dielectric block having a rectangular parallelepiped shape is used, a plurality of resonators are provided in parallel with the surface of the dielectric block and in parallel with each other, and a ground conductor is provided on the surface of the dielectric block. Is.

In addition to using a plate-shaped dielectric substrate,
A plurality of resonators are provided on the surface of the dielectric substrate in parallel with each other, and a ground conductor is provided in parallel with the surface of the dielectric substrate at a distance from the dielectric substrate.

Further, a plurality of resonators are provided alternately so that one end on the opposite side is a short circuit portion and the other end is an open portion, and the short circuit portion is connected to a ground conductor.

Further, a plurality of resonators are provided such that one end on the same side is a short circuit portion and the other end is an open portion, and the short circuit portion is connected to a ground conductor.

A plurality of resonators are provided on the surface of the dielectric block in parallel with each other, and a ground conductor is provided on the other surface of the dielectric block with respect to the surface.
An input terminal and an output terminal are respectively connected to the resonators located at both ends of the resonators, and the other resonators are paired by two adjacent resonators, and each resonator forming a pair is
The adjacent ends are connected to each other and the other end is an open part.

Further, by connecting the input terminal and the output terminal to the resonator through the impedance transformer, respectively, the characteristic impedance as seen from the inside of the filter from the input terminal and the output terminal through the impedance transformer. Is adapted to match the characteristic impedance of an external circuit connected to the outside of the filter via the input terminal and the output terminal.

Further, the impedance transformer is constituted by a strip line having an electrical length of ¼ wavelength.

Further, the impedance transformer comprises a strip line and a capacitive stub whose tip connected in parallel to the strip line is short-circuited to a ground conductor.

Also, a conductor is provided on the side surface of the dielectric block on the open side of the resonator to which the input terminal and the output terminal are connected.

[0017]

In the dielectric filter constructed as described above, the characteristic impedance of the filter as seen from the input terminal and output terminal sides should be lower than the characteristic impedance of the external circuit connected to the input terminal and output terminal. As a result, the characteristic impedance of the resonator becomes low and the coupling coefficient between the resonators becomes small, so that the inner conductor width of the resonator and the interval between the resonators become large.

Also, as seen from the input terminal and output terminal side,
By setting the characteristic impedance of the filter to 50Ω or less, the characteristic impedance of the resonator becomes low and the coupling coefficient between the resonators becomes small, so that the inner conductor width of the resonator and the distance between the resonators become large.

Further, by connecting the input terminal and the output terminal to the resonator through the impedance transformer, respectively, the characteristic impedance of the inside of the filter seen from the input terminal and the output terminal through the impedance transformer. Is adapted to match the characteristic impedance of an external circuit connected to the outside of the filter via the input terminal and the output terminal.

Further, by configuring the impedance transformer by a strip line having an electrical length of ¼ wavelength, the characteristic impedance of the inside of the filter seen from the input terminal and the output terminal through the impedance transformer, The characteristic impedance of an external circuit connected to the outside of the filter is matched through the input terminal and the output terminal.

Further, the impedance transformer comprises a strip line and a capacitive stub whose tip is connected in parallel to the strip line and whose tip is short-circuited to the ground conductor, so that the impedance transformer is connected from the input terminal and the output terminal. The characteristic impedance as viewed from the inside of the filter via is matched with the characteristic impedance of an external circuit connected to the outside of the filter via the input terminal and the output terminal.

Further, a conductor is provided on the side surface of the dielectric block on the open side of the resonator to which the input terminal and the output terminal are connected, and the size of the conductor is changed to adjust the electrostatic capacitance on the open side. The characteristic impedance viewed from the inside of the filter from the input terminal and the output terminal is matched with the characteristic impedance of an external circuit connected to the outside of the filter via the input terminal and the output terminal.

[0023]

【Example】

Example 1. An embodiment of the present invention will be described below with reference to the drawings. 1A and 1B show an embodiment of an interdigital dielectric filter using a dielectric according to the present invention. FIG. 1A is a horizontal sectional view, FIG. 1B is a sectional view taken along line bb of FIG. FIG. 3C is a diagram for explaining the relationship between the characteristic impedance inside and outside the filter. The same or corresponding parts as those shown in FIG. 8 are designated by the same reference numerals, and the description thereof will be omitted. In the present embodiment, as shown in FIG. 8C, the characteristic impedance (= Zi) seen from the inside of the filter from the input terminal 51 and the output terminal 52 is set to an impedance lower than 50Ω.

In the dielectric filter constructed as in this embodiment, the resonators 31 to 31 are formed by setting the characteristic impedance of the input terminal 51 and the output terminal 52 as viewed from the inside of the filter to be lower than 50Ω. Three
5 has a low characteristic impedance, and the resonator 31
Since the coupling coefficient between .about.35 is small, the inner conductor width W of the resonators 31 to 35 and the interval P between the resonators 31 to 35 can be increased even in the case of a broadband filter. For example, using a dielectric having a relative dielectric constant of 39.5, Z
In the case of a filter having i = 30Ω and a relative bandwidth of 30%, the inner conductor width W of the resonator is 0.72 m when designed according to the above-mentioned literature.
m, the interval P between the resonators is 0.96 mm, and a value that can be easily manufactured can be realized.

Example 2. 2A and 2B show a configuration example of an interdigital dielectric filter using a dielectric according to another embodiment of the present invention. FIG. 2A is a horizontal sectional view, and FIG. 2B is a line bb of FIG. 2C is a cross-sectional view, and FIG. 7C is a diagram illustrating a relationship between the characteristic impedance inside and outside the filter. Reference numerals 61 and 62 denote impedance transformers provided between the input terminal 51 and the output terminal 52 and the resonators 31 and 35. In this embodiment, as shown in FIG. 2C, when the impedance transformers 61 and 62 are connected to the resonators 31 and 35 on the primary side and the external circuit is connected to the secondary side. The characteristic impedances Z1 and Z2 on the primary side and the secondary side of the impedance transformers 61 and 62 are set equal to the characteristic impedance Zi of the filter and the characteristic impedance Zo of the external circuit, respectively. According to this embodiment, by providing the impedance transformers 61 and 62, the characteristic impedance (= Z2) on the filter side seen from the input terminal 51 and the output terminal 52 through the impedance transformers 61 and 62 is set to 50Ω. Therefore, reflection caused by impedance mismatch with an externally connected circuit can be reduced, and reflection loss and insertion loss at the input / output of the filter can be improved.

Example 3. FIG. 3 shows a configuration example of an interdigital dielectric filter using a dielectric according to still another embodiment of the present invention, (a) is a horizontal sectional view,
(B) is sectional drawing in the bb line of (a). In the present embodiment, the impedance transformers 61 and 62 are strip lines 71 and 72 provided between the input terminal 51 and the output terminal 52 of the filter and the resonators 31 and 35 and having an electrical length of ¼ wavelength. It is supposed to be configured. According to this embodiment, by providing the impedance transformers 61 and 62, the characteristic impedance on the filter side seen from the input terminal 51 and the output terminal 52 through the impedance transformers 61 and 62 can be set to 50Ω. Therefore, the reflection loss and the insertion loss of the input and output of the filter can be improved, and the configurations of the impedance transformers 61 and 62 can be easily realized.

Example 4. 4A and 4B show a configuration example of an interdigital dielectric filter using a dielectric according to another embodiment of the present invention. FIG. 4A is a horizontal sectional view and FIG. 4B is a line bb of FIG. FIG. In this embodiment, impedance transformers 61 and 62 are connected in parallel to the strip lines 81 and 82 provided between the input terminals 51 and output terminals 52 of the filter and the resonators 31 and 35, and the strip lines 81 and 82. And the capacitive stubs 91 and 92 whose tips are short-circuited to the ground conductors 21 and 22 by the conductors 46 and 47. According to this embodiment,
By providing the impedance transformers 61 and 62,
Since the characteristic impedance of the filter seen from the input terminal 51 and the output terminal 52 through the impedance transformers 61 and 62 can be set to 50Ω, the reflection loss and the insertion loss of the input and output of the filter can be improved, and
The impedance transformers 61 and 62 can be downsized.

Example 5. FIG. 5 shows an example of the construction of an interdigital dielectric filter using a dielectric according to another embodiment of the present invention. (A) is a horizontal sectional view, (b) is a line bb of (a). 2 is a sectional view of FIG. 101 and 102 are strip lines that connect the input terminal 51 and the output terminal 52 to the resonators 31 and 35, and 11
Reference numerals 1 and 112 denote conductors provided on the side surfaces of the dielectric block 10 corresponding to the open portions of the resonators 31 and 35 to which the strip lines 101 and 102 are connected. According to the present embodiment, the capacitance applied to the open parts of the resonators 31 and 35 can be adjusted by the conductors 111 and 112, and the characteristic impedance of the filter viewed from the input terminal 51 and the output terminal 52 is set to 50Ω. Therefore, the reflection loss and the insertion loss of the input and output of the filter can be improved. Further, unlike the fourth and fifth embodiments, since the impedance transformer is not separately provided, a small filter can be realized.

Example 6. In each of the above embodiments, the characteristic impedance of the external circuit is generally UHF,
Although 50Ω which is often used in the VHF and microwave bands has been described, it goes without saying that the present invention can be applied to the case where it is not 50Ω. In this case, the characteristic impedance inside the filter is made lower than the characteristic impedance of the external circuit. As a result, a dielectric filter having the same effect can be obtained.

Example 7. Further, in each of the above-described embodiments, as shown in FIG. 6A, the strip line 121 is provided inside the dielectric block 10, and the ground conductors 21 and 22 are provided on the surfaces of the dielectric block 10 facing each other. The case where it is applied to a plate line has been described.
As shown in (b), the strip line 121 is provided on one surface of the dielectric block 10, and the ground conductor 22 is provided on the other surface of the dielectric block 10 opposite to the surface. The same applies to the suspended line in which the strip line 121 is provided on both surfaces of the dielectric substrate 11 and the ground conductor 22 is provided at a position apart from the surface of the dielectric substrate 11 as shown in FIG. 6 (c). can do.

Example 8. Further, in each of the above embodiments, the case where a plurality of resonators are applied to an interdigital resonator in which one end on the opposite side is alternately a short circuit portion and the other end is an open portion has been described. , FIG. 7 (a)
7, a plurality of resonators 31 to 35 are provided in a combline shape so that one end on the same side has a short-circuited portion and the other end has an open portion, and as shown in FIG. The resonators 31 to 38 are connected to the input terminals 51 and the output terminals 52 to the resonators 31 and 38 located at both ends, and the other resonators 32 to 37 form a pair with two adjacent resonators.
The respective resonators forming a pair can be similarly applied to a resonator provided in a side-coupling type such that the resonators are connected to each other at adjacent ends and the other end is an open portion.

Example 9. Further, in each of the above-described embodiments, the impedance transformers 61 and 62 have been described as being configured by strip lines, but the same effect can be obtained even if the impedance transformers 61, 62 are configured by discrete discrete inductances, capacitors and lines. It is obvious that the above can be achieved according to the above description.

Example 10. Further, in each of the above embodiments, a rectangular parallelepiped dielectric block, resonators arranged in parallel, resonators having an electrical length of ¼ wavelength, input terminals and output terminals connected to the resonators at both ends, Although the case has been described, the shape of the dielectric block, the arrangement of the resonators, the resonator length, and the position of the resonator to which the input terminal and the output terminal are connected are not limited to the above case.

[0034]

Since the present invention is configured as described above, it has the following effects.

By making the characteristic impedance of the filter seen from the input terminal and the output terminal side lower than the characteristic impedance of the external circuit connected to the input terminal and the output terminal, the characteristic impedance of the resonator becomes low, and Since the coupling coefficient between the resonators is small, the width of the inner conductor of the resonators and the distance between the resonators can be increased, which facilitates the processing of the dielectric and the manufacturing of the resonators.

Also, as seen from the input terminal and output terminal side,
By setting the characteristic impedance of the filter to 50Ω or less, the characteristic impedance of the resonator becomes low and the coupling coefficient between the resonators becomes small. Therefore, it is possible to increase the inner conductor width of the resonator and the distance between the resonators. This facilitates processing of the dielectric and manufacturing of the resonator.

Further, by connecting the input terminal and the output terminal to the resonator through the impedance transformer, respectively, the characteristic impedance of the inside of the filter seen from the input terminal and the output terminal through the impedance transformer. Is matched with the characteristic impedance of the external circuit connected to the outside of the filter via the input terminal and the output terminal, so that the reflection loss and the insertion loss of the input and output of the filter can be improved.

Further, by configuring the impedance transformer with a stripline having an electrical length of ¼ wavelength, the impedance transformer can be simplified in configuration, and the input and output terminals can be connected via the impedance transformer. The characteristic impedance of the filter as seen inside the filter is matched to the characteristic impedance of the external circuit connected to the outside of the filter via the input and output terminals. Can be improved.

Further, by configuring the impedance transformer with a strip line and a capacitive stub whose tip connected in parallel to the strip line is short-circuited to the ground conductor, the impedance transformer can be connected from the input terminal and the output terminal. Since the characteristic impedance as seen from the inside of the filter via the input terminal and the output terminal is matched with the characteristic impedance of the external circuit connected to the outside of the filter, the impedance transformer is miniaturized, Moreover, the reflection loss and the insertion loss of the input and output of the filter can be improved.

Further, by providing a conductor on the side surface of the dielectric block on the open side of the resonator to which the input terminal and the output terminal are connected and changing the size thereof, the capacitance on the open side is adjusted. , The characteristic impedance of the input terminal and the output terminal as viewed from the inside of the filter is matched with the characteristic impedance of the external circuit connected to the outside of the filter through the input terminal and the output terminal. It is possible to improve the reflection loss and the insertion loss of the input and output of the filter without increasing.

[Brief description of drawings]

1A and 1B are configuration diagrams showing a dielectric filter according to an embodiment of the present invention, in which FIG. 1A is a horizontal sectional view, FIG. 1B is a sectional view taken along line bb of FIG. 1A, and FIG. It is a figure explaining the relationship of the internal / external characteristic impedance.

2A and 2B are configuration diagrams showing a dielectric filter according to another embodiment of the present invention, where FIG. 2A is a horizontal sectional view, FIG. 2B is a sectional view taken along line bb of FIG. 2A, and FIG. It is a figure explaining the relationship of the characteristic impedance inside and outside a filter.

FIG. 3 is a configuration diagram showing a dielectric filter according to still another embodiment of the present invention, in which (a) is a horizontal sectional view,
(B) is sectional drawing in the bb line of (a).

FIG. 4 is a configuration diagram showing a dielectric filter according to still another embodiment of the present invention, in which (a) is a horizontal sectional view,
(B) is sectional drawing in the bb line of (a).

FIG. 5 is a constitutional view showing a dielectric filter according to still another embodiment of the present invention, in which (a) is a horizontal sectional view,
(B) is sectional drawing in the bb line | wire of (a), (c) is a perspective view.

6A and 6B are explanatory views showing types of strip lines in a dielectric filter according to still another embodiment of the present invention, where FIG. 6A is a triplate line, FIG. 6B is a microstrip line, and FIG. 6C is a suspended line. It is a figure explaining.

FIG. 7 is an explanatory view showing types of resonators in a dielectric filter according to still another embodiment of the present invention,
(A) is a figure explaining a comb line type resonator, (b) is a figure explaining a side coupling type resonator.

FIG. 8 is a configuration diagram showing a conventional dielectric filter,
(A) is a horizontal sectional view, (b) is a sectional view taken along the line bb of (a), (c) is a perspective view, and (d) is a diagram for explaining the relationship between the internal and external characteristic impedance of the filter. .

[Explanation of symbols]

10 Dielectric Blocks, 11 Dielectric Substrates 21, 22
Ground conductor, 31-38 resonator, 41-47 conductor,
51 input terminal, 52 output terminal, 61, 62 impedance transformer, 71, 72 strip line, 81,
82 strip line, 91, 92 tip short-circuit stub, 101, 102 strip line, 111, 11
2 conductors, 121,122 stripline.

Claims (11)

[Claims] 1. A ground conductor made of metal, a dielectric block made of a dielectric material, and a strip provided on or inside the dielectric block and having an electrical relationship with the ground conductor. A plurality of resonators electrically connected to each other configured by lines, an input terminal connected to any one of the resonators, and an output terminal connected to any one of the resonators In the dielectric filter, the characteristic impedance as viewed from the inside of the filter from the input terminal and the output terminal is lower than the characteristic impedance of an external circuit connected to the outside of the filter via the input terminal and the output terminal. And a dielectric filter. 2. The dielectric filter according to claim 1, wherein the characteristic impedance as viewed from the inside of the filter from the input terminal and the output terminal is 50Ω or less. 3. A rectangular parallelepiped dielectric block, a plurality of resonators provided parallel to the surface of the dielectric block and parallel to each other, and a ground conductor provided on the surface of the dielectric block. The dielectric filter according to claim 1, wherein the dielectric filter is formed of: 4. A plate-shaped dielectric substrate, a plurality of resonators provided on the surface of the dielectric substrate in parallel with each other, and a gap from the dielectric substrate in parallel with the surface of the dielectric substrate. The dielectric filter according to any one of claims 1 and 2, wherein the dielectric filter is formed of a grounded conductor that is placed side by side. 5. A plurality of resonators, which are alternately provided with one end on the opposite side being a short-circuit portion and the other end being an open portion, wherein the short-circuit portion is connected to a ground conductor. The dielectric filter according to claim 3. 6. A resonator comprising a plurality of resonators, one end of which is on the same side and the other end of which is an open portion. The short circuit portion is connected to a ground conductor. 3. The dielectric filter according to any one of 3 and 4. 7. A resonator comprising a plurality of resonators provided on a surface of a dielectric block in parallel with each other, and a ground conductor provided on another surface with respect to the surface of the dielectric block, the resonance comprising: The input terminals and the output terminals are respectively connected to the resonators located at both ends of the resonator, and the other resonators are paired by two adjacent resonators, and the paired resonators are adjacent to each other. The dielectric filter according to claim 3, wherein the dielectric filter is connected and the other end is open. 8. An input terminal and an output terminal are respectively connected to a resonator via an impedance transformer, and a characteristic impedance as viewed from the inside of the filter from the input terminal and the output terminal via the impedance transformer is provided. The dielectric filter according to any one of claims 1 to 7, wherein the dielectric filter is matched with a characteristic impedance of an external circuit connected to the outside of the filter via the input terminal and the output terminal. 9. The dielectric filter according to claim 8, wherein the impedance transformer is constituted by a stripline having an electrical length of ¼ wavelength. 10. The dielectric filter according to claim 8, wherein the impedance transformer comprises a stripline and a capacitive stub whose tip connected in parallel to the stripline is short-circuited to a ground conductor. 11. The dielectric according to claim 5, wherein a conductor is provided on a side surface of the dielectric block on the open side of the resonator to which the input terminal and the output terminal are connected. Body filter.