JP3162790B2 - Dielectric filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION This invention Ru <br/> relates to a dielectric filter.

[0002]

2. Description of the Related Art Conventionally, as a dielectric filter using a dielectric coaxial resonator, a through hole is provided in a dielectric member, and a conductive member (an outer peripheral surface of the dielectric member and an inner peripheral surface of the through hole are provided on the dielectric member). For example, a single-sided short-circuit type coaxial resonator formed by coating silver) is connected to a dielectric substrate, and each coaxial resonator is capacitively coupled by an electrode formed on the dielectric substrate. ing.

[0003] In recent years, in mobile communication, weight reduction and volume reduction have been progressing, and accordingly, there has been a demand for miniaturization of dielectric filters.

Incidentally, in order to obtain a high Qu (Q value at no load), it is necessary to set the ratio of the inner coaxial diameter to the outer coaxial diameter to 3.6. For this reason, when reducing the size of the dielectric filter, for example, if the outer coaxial diameter is 4 mm or less, the inner coaxial diameter is 1.2 mm or less, and the external connection member passes through the coaxial resonator as described above. It is difficult to connect to an external circuit by inserting it into the hole.

As a dielectric filter which solves this problem, the present applicant has proposed Japanese Patent Application No. 2-196572.

When a filter is constituted by three or more stages of coaxial resonators, the size of the middle stage coaxial resonator is made larger than that of the first and second stage coaxial resonators in order to make the resonance frequency of each resonator different. There is a need to. For this reason, there is a problem that coaxial resonators of various lengths are required.

On the other hand, in a mobile communication device, a duplexer for separating and combining signals of different frequencies in accordance with the frequency is used. Such a duplexer includes a transmitting dielectric filter and a receiving dielectric filter having different center frequencies. With such a dielectric filter, with the increase in the frequency of mobile communication,
The interval between the center frequencies of the reception band and the transmission band has become narrow, making it difficult to obtain the necessary out-of-band attenuation. For this reason, a dielectric filter used for a duplexer is required to have an attenuation pole in its characteristics.

As a method of forming a pole in an attenuation region, for example, in a dielectric filter disclosed in Japanese Patent Application Laid-Open No. 62-77703, at least one resonator is skipped and a direct reactance element is used between the resonators. By connecting, such a pole is formed.

However, this configuration has a problem that the number of parts increases and assembly becomes complicated.

[0010] In order to solve this problem, Japanese Patent Application No. 3-4 / 1993 discloses a method for solving this problem.
No. 6,796, proposes a dielectric filter as shown in FIGS . This dielectric filter will be described with reference to the drawings.
A filter is configured using the coaxial resonators ₁₁ to ₁₅ . A concave portion 2 is provided in each of the resonators ₁₁ to ₁₅ , and a dielectric substrate 3 ′ is attached to the concave portion 2. The resonators ₁₁ to ₁₅ are coupled to each other via a coupling window.

As shown in FIG. 14 , the dielectric substrate 3 'has input / output connection electrodes 3a', 3a "and capacitance forming electrodes 3c ', 3c", 3c "" on the upper surface, and the lower surface, as shown in FIG. Are formed with stub electrodes 3d 'and 3d "for external connection, which are extended from the electrodes 3a' and 3a" for input and output, and a ground electrode 3b.

The input / output connection electrodes 3a ', 3
a "and resonator ₁ 1, 1 ₅ terminal capacitance between C1, C1 '
Is formed. Also, the capacitance forming electrodes 3c ', 3c ",
3c '''coaxial resonator 1 _2, 1 _3, 1 ₄ of the conductor 1d _2,
1d _3, the resonator length compensation capacitance C2 between 1d _4, C'2,
C ″ 2 is formed. Further, the input / output side connection electrode 3 is formed.
a ′, 3a ″ and capacitance forming electrodes 3c ′, 3c ″, 3
The jump capacitances C3, C'3, and C "3 are formed between the capacitors C" and C "".

As shown in FIGS. 15 and 16 , in this dielectric filter, a pole P is formed in the attenuation region of the filter characteristic due to the jump capacitors C3, C3 'and C3 ".

[0014]

However, in the above-described dielectric filter, when the grounding of the grounding electrode 3b of the dielectric substrate 3 is incomplete, the grounding electrode 3b is connected between the connecting electrodes 3d 'and 3d ". In particular, it is difficult to obtain perfect grounding in a microwave band of 1 GHz or more, which causes a serious problem.

That is, it is practically difficult to take a complete ground, and an impedance component is included between the ground and the ground electrode 3b. In this case, of the power coming from the input side, a part of the power not coupled to the resonator side is directly coupled to the output side via the capacitor. At this time, in the frequency characteristics of the filter, the attenuation outside the band is significantly deteriorated.

To prevent this, it is conceivable to remove the grounding electrode 3b from the dielectric substrate 3. However, noise from an external circuit or element adjacent thereto may cause the internal conductor of the resonators ₁₁ to ₁₅ or the dielectric substrate 3 Connection electrodes 3d ', 3
d ", which leads to deterioration of filter characteristics.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a miniaturized dielectric filter in which the anti-resonance capacitance and the coupling between the coaxial resonators for obtaining a filter characteristic having an attenuation pole can be manufactured with good workability. .

By the way, the jump capacitance C shown in FIG.
3, C'3, C "3, the extreme
The dielectric filter on which P is formed is connected to the ground of the dielectric substrate 3 '.
If the connection electrode 3b is incompletely grounded, the connection electrode 3
Capacitive coupling occurs between d 'and 3d "via the ground electrode 3b.
This will significantly degrade the filter characteristics. Especially 1G
Complete grounding shall be obtained in the microwave band above
Out of band in the frequency characteristics of the filter.
Damping is significantly degraded.

Therefore, the present invention provides a jump connection
To form a pole P in the attenuation region of the filter characteristic.
Grounding of the grounding electrode is not
Fired through the grounding electrode due to perfect condition
Dielectric filter to prevent direct coupling between input and output
To provide.

[0020]

DISCLOSURE OF THE INVENTION In view of the above points, this invention
Ming's dielectric filter consists of multiple coaxial resonators and external connection
And each of the coaxial resonators has an outer peripheral surface and an inner peripheral surface that are alternated.
First and second axes coaxially parallel to each other and crossing the axis.
A dielectric block having an end surface, and the outer peripheral surface and the inner peripheral surface
First and second conductor layers coated on the surfaces, and the first and second conductor layers
A third conductive layer formed on the second end face for short-circuiting the conductive layer of the third conductive layer.
And a part of the first conductor layer on the side of the first end face.
Or removing part of the first conductor layer including the dielectric block
Recess formed and multiple external connections on one main surface
Electrodes for external connection on the other main surface.
A plurality of grounding electrodes corresponding to the electrodes, each of which is electrically insulated
A pole is formed, and the one main surface side is in contact with the recess.
And a dielectric substrate attached to the substrate.

Further, a second dielectric filter according to the present invention is characterized in that an outer peripheral surface and a plurality of inner peripheral surfaces are arranged coaxially in parallel with each other and have first and second end surfaces crossing the axis. A block, a first conductor layer formed on the outer peripheral surface, a plurality of second conductor layers formed on a plurality of front surfaces,
A third conductive layer formed on the second end face for short-circuiting the first and second conductive layers, and a first conductive layer on a part of the first conductive layer on the first end face, the first conductive layer including a dielectric block. And a plurality of external connection electrodes formed on one main surface, and corresponding to the external connection electrodes on the other main surface, each of which is electrically connected. A dielectric substrate formed with a plurality of insulated grounding electrodes, the one main surface of which is in contact with and attached to the recess.

[0022]

According to the dielectric filters of the first and second aspects, since the plurality of grounding electrodes formed on the dielectric substrate are electrically insulated, they are not coupled to the input side coaxial resonator. All of the power that has flowed into the ground except for the reflected
No direct I / O coupling occurs.

[0023]

FIG . 1 is a diagram showing a first embodiment of the present invention.
This shows an example in which a first coaxial resonator 50 and a second coaxial resonator 51 constitute a dielectric filter. The first coaxial resonator 50 is on the input side, and the second coaxial resonator 51 is on the output side. And The coaxial resonators 51 and 52 are made of TiO with through holes.
₂ -SnO ₂ -ZrO ₂ based dielectric member (dielectric constant 40)
Conductive material such as silver is coated on the outer peripheral surface of the
This is a single-sided short-circuit type coaxial resonator. The first coaxial resonator 50 and the second coaxial resonator 51 are formed with concave portions 52 and 52 ′, respectively.
A dielectric substrate 53 made of alumina having an input-side connection electrode 53a and an output-side connection electrode 53a 'shown in FIG. 1D is attached to 2', and the connection electrodes 53a, 53 are provided.
a 'and the inner conductors 50d, 51d' of the coaxial resonators 50, 51
Is performed.

The coupling between the coaxial resonators 50 and 51 (inter-stage coupling) is performed by the outer conductors 50c and 50c of the respective coaxial resonators 50 and 51.
This is achieved by joining together windows (not shown) formed by removing a part of 51c.

As shown in the bottom view of FIG. 1C, first and second grounding electrodes are provided on the back surface of the dielectric substrate 53 corresponding to the input and output connection electrodes 53a, 53a ', respectively. 53b and 53b 'are formed. The distance between the first and second grounding electrodes 53b and 53b 'is a distance that does not cause coupling and prevents the entry of noise, and is, for example, 0.2 mm.

FIG. 2 is a diagram showing an equivalent circuit of the dielectric filter according to the first embodiment, wherein C1 and C1 'denote the coaxial resonator 50,
A coupling capacitance formed between the inner conductors 50 d and 51 d ′ of 51 and the connection electrodes 53 a and 53 a ′ of the dielectric substrate 53;
C2 and C2 'are capacitances formed between the connection electrodes 53a and 53a' and the first and second ground electrodes 53b and 53b ', C3 is an interstage coupling capacitance, and Z and Z' are ground electrodes. 53
b, 53b 'are impedance components generated when the grounding is incomplete.

FIG. 3 is a graph showing the frequency characteristic of the dielectric filter of the first embodiment, the broken lines are those of the dielectric filter of the structure shown in FIG. 13. As is apparent from this characteristic diagram, by dividing the ground electrode formed on the back surface of the dielectric substrate 53, direct coupling between input and output is prevented,
The out-of-band attenuation characteristics of the filter are improved.

FIG . 4 is a view showing a second embodiment of the present invention, and shows an example in which a filter is constituted by using four coaxial resonators 61 to 64. 4A is a perspective view, and FIG. 4B is a bottom view. Each of the resonators 61 to 64 is provided with a concave portion 65, and a dielectric substrate 70 is attached to the concave portion 65. Each of the resonators 61 to 64 has a coupling window (not shown).
Are coupled through.

On the upper surface of the dielectric substrate 70, input / output connection electrodes 70a, 70a 'and capacitance forming electrodes 70c, 7
0c ', and the input / output side connection electrodes 70a, 7
External connection stub electrodes 70d, 70 extended from 0a '
d ', the connection electrodes 70a, 70a' and the capacitance forming electrodes 70c, 70c '
_{1 ~70b 4} is formed.

The input / output connection electrodes 70a, 70
Input / output coupling capacitors C21 and C21 'are formed between a' and the inner conductors 61d and 64d of the coaxial resonators 61 and 64.
Further, the capacitance forming electrodes 70c and 70c 'and the coaxial resonator 6
Resonator length correcting capacitors C24 and C24 'are formed between the inner conductors 62d and 63d of the second and 63 inner conductors.

FIG . 5 shows an equivalent circuit of the dielectric filter according to the second embodiment. In the circuit diagram, C23, C23 ', C2
3 ″ is an inter-stage coupling capacitance, and C25 and C25 ′ are capacitances formed between the capacitance forming electrodes 70C and 70C ′ and the grounding electrodes 70b ₂ and 70b ₃ .

In the second embodiment, when a pole P is formed in the attenuation region of the filter characteristic, at least one resonator is skipped and the resonators are connected by a transmission line. For example, the input / output side connection electrode 70a and the capacitance forming electrode 70c '
And input / output side connection electrode 70a 'and capacitance forming electrode 70c
May be connected by a transmission line, or one of them may be jump-connected.

FIG . 6 shows a third embodiment of the present invention.
In the dielectric member 81a ', a plurality of through holes 81b, 81b',
81b '', an example of a dielectric filter including a plurality of coaxial resonators, one end of which is short-circuited, in which an outer conductor 81c and an inner conductor are formed by coating a conductive member on the outer peripheral surface and the inner peripheral surface. Is shown.

In the third embodiment, a concave portion 82 is formed by removing a part of the outer conductor on the open side of each coaxial resonator or a part of the outer conductor including a dielectric member. Dielectric substrate 83 having external connection electrodes 83a and 83a 'and grounding electrodes 83b and 83b' formed substantially at the center.
Is attached to form a dielectric filter.

In the third embodiment, when the capacitance forming electrode is formed on the dielectric substrate as in the second embodiment, the grounding electrode provided on the back surface is divided accordingly.

In the sixth embodiment, when the pole P is formed in the attenuation region of the filter characteristic, the external connection electrode 8
By connecting 3a and 83a 'with transmission lines, respectively,
One resonator is skipped to connect the resonators.

According to the first to third embodiments, the ground electrode formed on the back surface of the dielectric substrate having at least the external connection electrode attached to the concave portion of the coaxial resonator is replaced with the external connection electrode and the ground electrode. Since a plurality of electrodes are provided separately from each other in correspondence with the capacitance forming electrodes, direct coupling between the input and output is prevented, thereby improving the out-of-band attenuation in the frequency characteristics of the filter without impairing the noise shielding effect. be able to.

By the way, in the above-described dielectric filter using a coaxial resonator, by short-circuiting one side of the resonator, a quarter-wavelength that resonates at a quarter of the wavelength at the resonance frequency is generated. A filter using a cavity resonator is well known.

For example, in the dielectric filter shown in FIG. 1 , a TiO ₂ —ZrO ₂ —SnO ₂ ceramic is used as a resonator material, and its relative dielectric constant εr is 40.
The dimensions of the coaxial resonators 50 and 51 are such that one side of the cross section perpendicular to the length direction has a length of 3 mm, the diameter of the through hole is 1 mm,
Assuming that the resonator length is 4.6 mm, the characteristic impedance Z ₀ is 12Ω.

In such a dielectric filter, impedance matching occurs in a specific frequency band as viewed from the input side, and exhibits characteristics of a band-pass filter. The resonance condition of the quarter-wave resonator is given by the following equation (1).

[0041]

## EQU1 ## Z ₀ · tan (β · 1) = ∞ (1) (where β is a propagation constant in the resonator)

The resonator length 1 is given by Equation 2 where c is the speed of light.

[0043]

1 = c / (4f ₀ εr ^1/2 ) (2) From the equation (2),

[0044]

F ₀ = c / (4l ₀ εr ^1/2 ) (3)

Therefore, the resonance frequency of the coaxial resonators 50 and 51 in FIG. 1 is 2.6 GHz.

By the way, since a resonator constituting a filter usually has two or more resonance modes, it may exhibit an undesirable filter characteristic. For example, in order to minimize the resonator length in a quarter-wavelength resonator, a basic TEM mode is usually used. However, a higher-order TEM having a resonance frequency that is an odd multiple of the frequency of the basic TEM mode is used. Mode exists. In the dielectric filter shown in FIG.
The resonance frequency of the mode is 2.6 GHz,
The resonance frequency of the higher order TEM mode is 7.8, 13.0, 1
It exists around 8.2 GHz. FIG. 7 shows the frequency characteristics of the dielectric filter of FIG . The reason why a large resonance characteristic appears at the resonance frequency of the higher-order TEM mode is that the coaxial resonators 50 and 51 strengthen each other because the resonance frequencies of the higher-order TEM mode are equal.

As described above, an undesired filter characteristic having a center frequency near an odd multiple of the center frequency of the desired filter characteristic appears. Such undesired filter characteristics have various adverse effects on microwave equipment. For example, when the filter on the receiving side has such unnecessary filter characteristics, a microwave in another band enters the circuit. When the filter on the transmission side has such unnecessary filter characteristics, microwaves other than the original transmission frequency are emitted into space.

The first and second embodiments of the present invention provide a dielectric filter which is small in size, does not complicate the circuit, and can eliminate undesired filter characteristics at the resonance frequency of a high-order TEM mode. Things.

FIG . 8 is a view showing a dielectric filter according to Embodiment 1 of the present invention . Single-side short-circuit type coaxial resonators 90, 10
Reference numeral 0 indicates that the outer peripheral surface and the inner peripheral surface of the dielectric member provided with the through-hole are covered with a conductive member such as silver except for the open surfaces 90a and 100a. The resonator material is TiO ₂ -ZrO _2-
It is a SnO ₂ -based ceramic and has a relative dielectric constant of 40.

The coaxial resonator 90 is the same as that shown in FIG. 1 , and its resonance frequency is 2.6 GHz.
The coaxial resonator 100 has a capacitance forming portion 1 on the open surface 100a.
01 is attached. FIG. 9A shows a coaxial resonator 100.
9B is an exploded perspective view of the capacitor forming unit 101, and FIG .

Each dimension of the coaxial resonator 90 is perpendicular to the length.
The length of one side of the straight section is 3 mm, the diameter of the through hole is 1 mm,
The shaker length is 4.6 mm. Each dimension of the coaxial resonator 100 is such that one side of a cross section perpendicular to the length direction has a length of 3 mm,
The diameter of the through hole is 0.8 mm, and the resonator length is 2.3 mm.

A first conductor 100d electrically connected to the outer conductor 100b is provided on the open surface 100a of the coaxial resonator 100.
And the second conductor 1 electrically connected to the inner conductor 100c
00e is formed.

The capacitance forming portion 101 is formed of a quadrangular prism-shaped dielectric member 102 having a bottom surface substantially the same as the open surface 100a of the coaxial resonator 100. This dielectric material may be the same as that of the coaxial resonator, or another dielectric material. The dielectric member 102 is provided with a through hole 102a, and a capacitor forming conductor 102b is provided on one surface. The surface of the capacitor forming portion 101 where no conductor is formed is attached to the open surface 102 a of the coaxial resonator 100 with an adhesive or a dielectric paste 96. The first conductor 100d and the second conductor 1 on the open surface 100a of the coaxial resonator 100
00e, the resonance frequency correction capacitors C31 and C32 are formed.

The coaxial resonator 100 and the capacitance forming section 101
Is set to 2.6 GHz as in the case of the coaxial resonator 90, and the combined capacitance C of the resonance frequency correction capacitors C31 and C32 is set to 5 pF. The combined capacitance C is obtained from Expression 4 indicating the resonance condition of the resonator.

[0055]

## EQU4 ## Z ₀ tan (β1) = 1 / (2πf ₀ C) (4)

The resonance frequency of the higher order TEM mode of this resonator appears around 11.1, 21.0 and 31.2 GHz. On the other hand, since the resonator lengths of the coaxial resonators 90 and 100 are different, the resonance frequencies of the high-order TEM mode of the coaxial resonator 90 are 7.8, 13.0, and 18.2 GHz.
different from z. Therefore, since the respective harmonic components are not added, undesired filter characteristics are suppressed.

The coaxial resonators 90 and 100 are provided with a concave portion 95 similarly to the dielectric filter of FIG. 1 , and the concave portion 95 has a dielectric substrate 110 on which external connection electrodes 110a and 110b are formed. Installed. The external connection electrodes 110a and 110b are connected to the inner conductors 90C and 100C of the coaxial resonators 90 and 100 by an input / output coupling capacitance C3.
3. Form C34. Also, the coaxial resonators 90 and 100
Are coupled via a coupling window (not shown) formed in the outer conductor.

FIG . 10 is an equivalent circuit of the dielectric filter of FIG. L is a coupling inductance between the resonators 90 and 100.

FIG . 11 is a diagram showing frequency characteristics of the dielectric filter of FIG. Compared to the frequency characteristic of FIG.
The characteristic that the pass characteristic at the resonance frequency of the EM mode is suppressed is different from the characteristic diagram.

FIG . 12A to FIG .
FIG. 9 is a cross-sectional view showing the reference example 2 and showing an example in which the configuration of the capacitance forming portion 101 attached to the coaxial resonator 100 is different. In the resonator shown in FIG. 12A, a first conductor 100e electrically connected to the inner conductor 100c is formed on the open surface 100a of the coaxial resonator 100, and a capacitance for electrically connecting to the outer conductor 100b is formed. The dielectric member 102 on which the conductor 102b is formed is attached to the open surface 100a of the coaxial resonator 100.

The resonator shown in FIG .
The first conductor 100d electrically connected to the outer conductor 100b is formed on the open surface 100a of the first member, and the dielectric member 102 on which the capacitor forming conductor 102b electrically connected to the inner conductor 100c is formed is coaxially formed. It is attached to the open surface 100a of the resonance 100.

FIG . 12C shows that a plurality of capacitance forming conductors 102b are alternately arranged facing each other in the capacitance forming portion 101, so that a large capacitance can be formed.

In the above-mentioned reference example , the resonance main fraction correction capacitance is connected to the inner conductor only to one of the pair of coaxial resonators. May be the same. By doing so, the length of both coaxial resonators can be shortened, so that the filter can be downsized.

As described above, in Reference Examples 1 and 2
According to this method , a small-sized dielectric filter having an improved undesired filter characteristic with suppressed pass characteristics at a resonance frequency of a high-order TEM mode can be realized without complicating the circuit.

[0065]

As described above , the first and second embodiments of the present invention are described.
According to a beauty second invention, since a plurality of ground electrodes formed on the derivative collector substrate is electrically insulated, the power has not been coupled to the input side coaxial resonator everything except where reflected It flows into the ground, and no direct coupling of input and output occurs.

[Brief description of the drawings]

FIG. FIG. 1 (A) shows an external view of the first embodiment of the present invention.
1B is a cross-sectional view, and FIG. 1C is a bottom view.
FIG. 1D is a plan view of the dielectric substrate.

FIG. 2 Dielectric filter according to a first embodiment of the present invention
3 is an equivalent circuit diagram of FIG.

FIG. 3 Dielectric filter according to a first embodiment of the present invention
3 is a frequency characteristic diagram of FIG.

FIG. 4 FIG. 4 (A) shows a second embodiment of the present invention.
FIG. 4B is a bottom perspective view.

FIG. 5 Dielectric filter according to a second embodiment of the present invention
3 is an equivalent circuit diagram of FIG.

FIG. 6 FIG. 6 (A) shows a third embodiment of the present invention.
FIG. 6B is a bottom perspective view.

FIG. 7 Dielectric filter according to a third embodiment of the present invention
3 is a frequency characteristic diagram of FIG.

FIG. 8 The dielectric filter according to Embodiment 1 of the present invention
It is an external appearance perspective view shown.

FIG. 9 FIG. 9A shows a coaxial cable according to the first embodiment of the present invention.
Exploded perspective view showing a resonator including a resonator and a capacitance forming portion
FIG. 9 and FIG. 9B show a common structure including a coaxial resonator and a capacitance forming portion.
It is a cross-sectional view which shows a shaker.

FIG. 10 Dielectric filter according to Embodiment 1 of the present invention
3 is a diagram showing an equivalent circuit of FIG.

FIG. 11 Dielectric filter according to Embodiment 1 of the present invention
3 is a frequency characteristic diagram of FIG.

FIG. FIGS. 12 (A) to 12 (C) are reference diagrams of the present invention.
It is sectional drawing which shows Example 2.

FIG. 13A is an external view of a conventional dielectric filter.
FIG. 13B is a perspective view, and FIG.

FIG. 14 FIG. 14A shows a conventional dielectric filter.
14B is a perspective view of a dielectric substrate, and FIG. 14B is a bottom view of the dielectric substrate.
FIG. 14C is a cross-sectional view of the dielectric substrate.

FIG. It is an equivalent circuit diagram of the conventional dielectric filter.

FIG. 16 FIG. 9 is a frequency characteristic diagram of a conventional dielectric filter.
You.

[Explanation of symbols] 50, 51, 61, 62, 63, 64, 90, 100
Coaxial resonator 50c, 51c, 61c, 62c, 63c, 64c, 9
0c, 100c Outer conductor 50d, 51d, 61d, 62d, 63d, 64d, 9
0d, 100d inner conductor 52, 52 ', 65, 95 recess 53, 70, 110 Dielectric substrate

Continuation of the front page (56) References JP-A-5-55811 (JP, A) JP-A-2-130103 (JP, U) JP-A-2-116102 (JP, U) (58) Fields surveyed (Int) .Cl. ⁷ , DB name) H01P 1/205 H01P 3/08

Claims (6)

(57) [Claims] 1. A coaxial resonator comprising a plurality of coaxial resonators and an external connection means, wherein each of said coaxial resonators has an outer peripheral surface and an inner peripheral surface coaxially parallel to each other and crosses said axis. A dielectric block having an end surface of the first and second conductor layers coated on the outer peripheral surface and the inner peripheral surface, and formed on the second end surface for short-circuiting the first and second conductor layers. A third conductive layer, a concave portion formed by removing a part of the first conductive layer including a dielectric block, which is significantly different from a part of the first conductive layer on the side of the first end face; A plurality of external connection electrodes are formed on the main surface, and a plurality of electrically grounded electrodes corresponding to the external connection electrodes are formed on the other main surface, and the one main surface side is A dielectric substrate that abuts and is attached to the recess. 2. A part of an external connection electrode formed on the one main surface side of the dielectric substrate is used as a capacitance forming electrode, and a part of the grounding electrode formed on the other main surface. 2. The dielectric filter according to claim 1 , wherein the dielectric filter corresponds to the capacitance forming electrode, and the ground electrode is electrically insulated. 3. The coaxial resonator according to claim 1, wherein each of the coaxial resonators has a window formed by removing a part of the first conductor layer, and performs coupling between the coaxial resonators. 2. The dielectric filter according to 1. Wherein said window portion, the central portion of the coaxial resonator, and the longitudinal direction according to claim 1, characterized in that it is formed such that the direction orthogonal to the second conductor layer Dielectric filter. 5. A dielectric block having an outer peripheral surface and a plurality of inner peripheral surfaces disposed coaxially in parallel with each other and having first and second end surfaces crossing the axis, and formed on the outer peripheral surface. A first conductor layer; a plurality of second conductor layers formed on a plurality of front surfaces; and a third conductor layer formed on the second end surface for short-circuiting the first and second conductive layers. A concave portion formed by removing a part of the first conductive layer including the dielectric block, which is notably a part of the first conductive layer on the first end face side; and a plurality of external connections on one main surface. Electrodes are formed, and
Corresponding to the external connection electrode on the other main surface, each electrically insulated plurality of ground electrodes are formed, a dielectric substrate mounted in the concave portion said one main surface is in contact with, and more Dielectric filter. Wherein said part of the dielectric substrate external connection electrode formed on one main surface side of the capacitance forming electrodes, a portion of the other of the ground electrode formed on the main surface 6. The dielectric filter according to claim 5 , wherein the dielectric filter corresponds to the capacitance forming electrode, and the grounding electrodes are electrically insulated from each other.