JP2002100911A - Dielectric resonator, dielectric filter, dielectric duplexer, high-frequency module, and communications equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dielectric resonator in which Qo is kept high and which is made small overall in size, a dielectric filter, a dielectric duplexer, a high-frequency module equipped therewith, and communications equipment. SOLUTION: Two sets of electrodes 2 and 3, having square openings respectively which are opposite to each other, are formed on both main faces of a dielectric plate 1, and projecting parts of the electrodes are formed at almost the center of the long side of the opening, so that they are non-linearly symmetrical with respect to a center line along the direction of the long side of the opening of the electrode. Thus, a basic resonance mode in which electric field is directed along the long-axis direction of the opening is coupled with a secondary resonance mode, where an electric field is directed in the short-axis direction of the opening.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric resonator formed by forming electrodes on both main surfaces of a dielectric plate, a dielectric filter, a dielectric duplexer, a high-frequency module including the same, and a communication device. is there.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication No.
1-4108 and JP-A-11-346102.

[0003] On both main surfaces of a dielectric plate, opposing electrode openings are provided to form a rectangular slot mode dielectric resonator, and one corner of the square electrode opening is cut off. In the figure, a slot mode resonance mode generated between two sets of opposing sides is coupled to each other to form a double shape by dropping (chamfering) the shape.

Discloses a dielectric resonator device in which electrodes having electrode openings facing each other are provided on both main surfaces of a dielectric plate, and a fundamental mode and a higher-order mode are used in combination. In addition, there is shown a structure in which a resonance frequency of a spurious mode is adjusted by forming a shape in which a corner portion of an electrode opening is cut off or rounded.

[0005]

However, in the device shown in the above, the basic mode is duplicated,
When the no-load Q is not high and a filter is configured, there is a problem that insertion loss increases. Further, in the device shown in (1), although the no-load Q of the higher-order mode resonator is high, it constitutes only a single-mode resonator.
The problem that the size becomes large arises.

SUMMARY OF THE INVENTION An object of the present invention is to provide a dielectric resonator, a dielectric filter, a dielectric duplexer, and a high-frequency module and a communication device including the same, which maintain a high Qo and reduce the overall size. is there.

[0007]

According to the present invention, an electrode having one or more sets of substantially rectangular openings opposed to each other is provided on each of both main surfaces of a dielectric plate. In a dielectric resonator having the opening as a resonator, a plurality of resonance modes having different directions and orders of an electromagnetic field are multiplexed in a resonator section having one or more sets of openings. With this structure, Qo due to higher order modes
And the number of resonators can be easily increased, and the overall size can be reduced.

The present invention also relates to a long-side portion of an opening provided on at least one main surface of a dielectric plate so as to be non-symmetric with respect to a center line along a long-side direction of the opening. Of the electrode is provided at the approximate center thereof. Alternatively, a convex portion or a concave portion of the electrode is provided substantially at the center of the long side portion of the opening such that the opening on both main surfaces of the dielectric plate is asymmetric or plane symmetric. This couples the fundamental resonance mode in which the electric field is directed in the major axis direction of the opening with the secondary resonance mode in which the electric field is directed in the minor axis direction, and couples two resonators coupled to one set of opposed electrode openings. Is configured.

Further, according to the present invention, an electrode is provided at a corner of an opening provided on at least one main surface of a dielectric plate so as to be non-symmetric with respect to a center line along a long side direction of the opening. Are provided. Alternatively, a convex portion or a concave portion of the electrode is provided at a corner of the opening such that the opening on both main surfaces of the dielectric plate is asymmetric or planar symmetric. This couples the fundamental resonance mode in which the electric field is directed in the major axis direction of the opening with the secondary resonance mode in which the electric field is directed in the minor axis direction, and couples two resonators coupled to one set of opposed electrode openings. Is configured.

The present invention also provides the above dielectric resonator,
A signal input / output unit coupled to the resonator unit by the opening is provided to constitute a dielectric filter.

Further, according to the present invention, the dielectric filter is provided as a transmission filter and a reception filter, respectively, to constitute a dielectric duplexer.

Further, the present invention provides a high-frequency module including the above-mentioned dielectric filter or dielectric duplexer and an antenna.

Further, the present invention constitutes a communication device including the high-frequency module and a communication circuit.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a dielectric resonator according to a first embodiment will be described with reference to FIGS. FIG. 1 is a perspective view of a dielectric resonator. In this example, electrodes 2 and 3 are provided on both main surfaces of a dielectric plate 1 having a rectangular plate shape. The electrodes 2 and 3 have rectangular openings 4 opposed to each other with the dielectric 1 interposed therebetween. , 5 are formed. The direction of the long sides of the openings 4 and 5 is such that the shape of the openings is non-linearly symmetric with respect to a center line (indicated by a dashed line in the figure) along the long side direction of the rectangular opening. Are provided substantially at the centers of the electrodes, respectively.

FIG. 2 shows each resonance mode of the dielectric resonator shown in FIG. (A) shows the direction of the electric field component of the fundamental wave in the rectangular slot mode generated in the resonator portions of the electrode openings 4 and 5 facing each other. (B) shows the direction of the electric field component in the second harmonic (second harmonic). When the resonance mode in which the electric field is oriented in the major axis direction of the opening as described above is set as the fundamental resonance mode, the aperture is formed so that a second-order resonance mode (hereinafter, referred to as “second harmonic mode”) occurs in the minor axis direction. The dimensions of the long sides and short sides of the parts 4 and 5 are determined.

FIGS. 2C and 2D show the directions of the electric field components in the coupling mode of the fundamental mode and the second harmonic mode. That is, (C) shows the even mode,
(D) shows the direction of each electric field component in the odd mode. Since the openings 4 and 5 are formed with a convex portion p substantially at the center in the long side direction, (C) and (D) of FIG.
In the state shown in (1), the resonance frequency of the even mode becomes lower than the resonance frequency of the odd mode. Due to the difference between the even mode resonance frequency and the odd mode resonance frequency,
The fundamental mode and the second harmonic mode are combined.

FIG. 3 shows the relationship between the size of the opening and the resonance frequency in the fundamental wave mode and the second harmonic mode. Here, the relative permittivity εr of the dielectric plate 1 is 24, the thickness of the dielectric plate 1 is 0.6 mm, the dimension of the long sides of the openings 4 and 5 is 3.4 mm, and the dimension (width) of the short side is ) From 1.5 to
The graph shows changes in the resonance frequencies of the fundamental wave and the second harmonic when changed in the range of 1.7 mm. In this example, by setting the width of the opening in the short side direction to 1.57 mm, the resonance frequency of the fundamental wave and the second harmonic can be made equal to about 26.9 GHz.

FIG. 4 shows the relationship between the coupling coefficient of the fundamental wave and that of the second harmonic with respect to the size of the projection p projecting inward from the electrode opening. Here, the configuration of the dielectric plate and the dimension in the major axis direction of the opening are the same as those shown in FIG. 3, the dimension in the minor axis direction is 1.57 mm, and the width of the projection is 0.4 mm.
And the change of the coupling coefficient when the protrusion amount L is changed in the range of 0 to 0.4 mm. As the protrusion amount L of the protrusion p increases, the coupling coefficient between the fundamental wave and the second harmonic wave increases. Therefore, when configuring a resonator device including a two-stage resonator in which two resonators of a fundamental wave and a second harmonic are coupled, the coupling coefficient between the two-stage resonators is determined by setting the dimension L.

Next, the configuration of a dielectric resonator according to a second embodiment will be described with reference to FIG. FIG. 5A is a perspective view of the dielectric resonator. Unlike the example shown in FIG. 1, the electrode 3 on the lower surface of the dielectric plate 1 is formed with a rectangular electrode opening 5 having no projection. Other configurations are the same as those shown in FIG.

As described above, the opposing electrode openings are formed in a rectangular shape, and the center line (dashed line) along the long side direction is formed.
The shape of the electrode openings is determined so that the openings are non-symmetrical with respect to the plane and the openings on both main surfaces of the dielectric plate are asymmetric with respect to the center plane of the dielectric plate. Even in such a shape of the electrode opening, a difference is generated between the even mode and the odd mode resonance frequencies of the fundamental wave and the second harmonic, as in the cases shown in FIGS. 2C and 2D. Both modes can be combined.

FIGS. 5B and 5C show another example of the shape of the electrode opening. In the example shown in FIGS. 1 and 5A, a convex portion of the electrode protruding inward of the opening is provided substantially at the center of the long side of the opening. (B), a concave portion of the electrode may be provided. Further, as shown in FIG. 5C, a convex portion p may be formed at the center of one long side portion, and a concave portion d may be formed at the center of the other long side portion.

As shown in FIG. 5B, when the concave portion of the electrode is formed in the center of the long side portion of the opening, the resonance frequency of the even mode and the odd mode, which are the coupling mode of the fundamental wave and the second harmonic, is reduced. Due to the difference, the fundamental wave and the second harmonic can be combined.
Also in the example shown in (C), a difference occurs between the resonance frequencies of the even mode and the odd mode, which are the coupling modes of the fundamental wave and the second harmonic, so that the fundamental wave and the second harmonic can be coupled. In particular, in the example shown in (C), when the directions of the electric fields of the odd mode and the even mode are set to the directions shown in FIG. 2, the resonance frequency of the odd mode becomes higher and the resonance frequency of the even mode becomes higher. , The coupling coefficient between the fundamental wave and the second harmonic can be easily increased.

The openings shown in FIGS. 5B and 5C are formed only on one main surface of the dielectric plate, and are formed on the other main surface with a simple rectangular opening. May be formed so that the openings on both main surfaces are asymmetric with respect to the plane. Alternatively, the openings on both main surfaces may have the same shape so that they are plane-symmetric.

Next, the structure of a dielectric resonator according to a third embodiment will be described with reference to FIGS. This third
The overall configuration of the dielectric resonator according to the embodiment is the same as that shown in FIG. 1 or FIG. FIG. 6 shows the shape of the electrode opening and each resonance mode. (A) shows an example of the electric field distribution for the fundamental wave mode, and (B) shows an example of the electric field distribution for the second harmonic mode. (C) shows the even mode of the combined mode of both modes.
(D) shows an example of each electric field distribution for the odd mode.

In the dielectric resonator according to the third embodiment, the whole shape of the electrode opening is rectangular, but the projection p of the electrode is formed at the corner of the opening.

As a result, a difference occurs between the resonance frequencies of the even mode and the odd mode shown in FIGS. 6C and 6D, and coupling occurs between the fundamental wave and the second harmonic.

FIG. 7 shows the relationship between the size of the protrusion p and the coupling coefficient. Here, the relative permittivity εr of the dielectric plate is 2
4. The thickness of the dielectric plate is 0.6 mm, the dimension in the long side direction of the opening is 3.4 mm, the dimension in the short side direction is 1.57 mm, and the long side direction and the short side direction from the corner of the convex portion p. Is a projection amount of L, and shows a change in coupling coefficient when this L is changed from 0 to 0.47.

As described above, as L increases, the coupling coefficient between the fundamental wave and the second harmonic can be increased. From this relationship, when configuring a resonator device including a two-stage resonator in which two resonators of a fundamental wave and a second harmonic are coupled, the coupling coefficient between the two-stage resonator is set by setting the dimension L. Determine.

Next, the configuration of a dielectric resonator according to a fourth embodiment will be described with reference to FIG. FIG. 8 shows the shape of the electrode opening. In (A), the convex portion p of the electrode is formed at two corner portions at non-diagonal positions of the opening. With this shape, the difference between the resonance frequencies of the even mode and the odd mode of the coupling mode can be increased as compared with the third embodiment. In the example shown in (B), (A)
From the state shown in FIG.
Is formed. Among the three electrode protrusions, the protrusion p at the diagonal position acts in a direction to reduce the difference between the resonance frequencies of the even mode and the odd mode, but depending on the balance of the protrusion amounts of the three protrusions p. , The coupling coefficient between the fundamental wave and the second harmonic can be determined.

In the example shown in FIG. 8C, a concave portion d of the electrode is formed at one corner of the opening. The concave portion d of the electrode acts in the opposite direction to the case where the convex portion of the electrode is formed at the corner of the electrode opening, causing a difference between the resonance frequency of the even mode and the odd mode of the coupling mode, and the fundamental wave and the two Coupling with harmonics. Similarly, as shown in FIG. 8D, concave portions d of the electrodes may be formed at non-diagonal positions of the openings.

FIG. 8E shows an example in which a concave portion d of the electrode is formed at another corner from the state shown in FIG. Here, the concave portion d of the electrode at the diagonal position acts in a direction to cancel the difference between the resonance frequencies of the even mode and the odd mode, but due to the balance of the concave portions d of these three electrodes,
The coupling coefficient between the fundamental wave and the second harmonic can be determined.

In the example shown in FIG. 8F, a convex portion p of the electrode and a concave portion d of the electrode are formed at diagonal positions of the opening. Even with such a shape, the fundamental wave and the second harmonic can be coupled by causing a difference between the resonance frequencies of the even mode and the odd mode of the coupling mode.

In the example shown in FIG. 8G, a concave portion d of the electrode is formed at a non-diagonal position of the electrode opening, and a convex portion p of the electrode is formed at another corner. Further, in the example shown in (H), the convex portion p of the electrode is formed at a corner portion further remaining from the state shown in (G). Even with such a shape,
By generating a large difference between the resonance frequencies of the even mode and the odd mode of the coupling mode, it is possible to secure a large coupling coefficient between the fundamental wave and the second harmonic.

The electrode openings of various shapes shown in FIG. 8 may be formed on one main surface of the dielectric plate, and the other main surface may be formed with an electrode opening having no concave or convex portions. Good. Further, the electrode openings of the respective shapes shown in FIG. 8 may be formed symmetrically on both the one main surface and the other main surface. further,
As an electrode opening formed on one main surface and the other main surface,
Any of the shapes shown in FIGS. 8A to 8H may be appropriately combined.

Next, the structure of a dielectric filter according to a fifth embodiment will be described with reference to FIGS. FIG.
FIG. 3 is an exploded perspective view of a dielectric filter. Here, 1 is a dielectric plate, and 2 and 3 are electrodes formed on both main surfaces thereof. The electrodes 2 and 3 form electrode openings facing each other with the dielectric plate 1 interposed therebetween. Reference numerals 4a and 4b denote electrode openings on the upper surface in the figure. The dielectric plate 1 on which the electrodes are formed constitutes a four-stage resonator as described later.

Reference numeral 6 denotes a base plate made of an insulating ceramic or the like, on which a ground electrode 7 and microstrip lines 8a and 8b as probes are formed. Reference numeral 9 denotes a metal frame mounted on the upper surface of the base plate 6, in which a spacer 10 is provided, and the dielectric plate 1 is accommodated in an upper portion thereof. Reference numeral 11 denotes a metal cover which covers the frame 9.

With the above configuration, a shield space is formed between the electrode 2 on the upper surface of the dielectric plate 1 and the cover 11 and between the electrode 3 on the lower surface and the ground electrode 7 at predetermined intervals.

FIG. 10 shows an example of the electric field distribution in the resonance mode of the resonator formed at the two opposing electrode openings. In FIG. 10, the dual mode resonator a shows a resonator generated at the electrode opening 4a shown in FIG. The resonance mode of the second harmonic is used as the first-stage resonator, and the resonance mode of the fundamental wave is used as the second-stage resonator. Since the electrode opening is formed with a convex portion p of an electrode similar to that shown in FIG. 2, the first-stage resonator and the second-stage resonator are coupled with a predetermined coupling coefficient.

In FIG. 10, the dual mode resonator b
9 shows a resonator generated in the electrode opening 4b shown in FIG. The resonance mode of the fundamental wave is used as the third-stage resonator, and the resonance mode of the second harmonic is used as the fourth-stage resonator. Since a convex portion p of the electrode similar to that shown in FIG. 2 is formed in the electrode opening, the third-stage resonator and the fourth-stage resonator are coupled with a predetermined coupling coefficient. In the second and third fundamental wave resonance modes shown in FIG. 10, electric field coupling is performed.

The microstrip line 8 shown in FIG.
a and 8b are magnetically coupled to the first-stage resonator and the fourth-stage resonator, respectively. Therefore, the four-stage resonators of the first to fourth stages shown in FIG. 10 function as filters having band-pass characteristics, which are sequentially coupled.

Next, an example of the dielectric duplexer according to the sixth embodiment will be described with reference to FIG. FIG. 11 is an exploded perspective view of the dielectric duplexer. Here, reference numeral 6 denotes a base plate in which glass cloth is impregnated with PTFE, and a ground electrode 7 and a microstrip line 8t are provided on the surface thereof.
x, 8ant, and 8rx are formed, respectively. Reference numeral 9 denotes a metal frame whose surface is plated with Ag. 10
Reference numerals 0tx and 100rx denote dielectric plate units formed by forming electrodes on both main surfaces of the dielectric plate, respectively, and constitute main parts of the transmission filter and the reception filter. Reference numeral 12 denotes an electromagnetic wave absorber block. Further, reference numeral 11 denotes a cover of a metal package, whose surface is plated with Ag.

Using each component shown in FIG. 11, a frame 9 is mounted on the base plate 6, and the electromagnetic wave absorber block 12 is accommodated in the frame 9 together with the dielectric plate units 100tx and 100rx. The dielectric duplexer is constituted by covering the cover with the opening.

The dielectric plate unit 100tx has four electrode openings facing each other across the dielectric plate. 4a, 4b, 4c, and 4d in the figure indicate electrode openings on the upper surface.

FIG. 12 shows the resonance mode of the resonator formed in the dielectric plate unit 100tx in FIG. Here, the first-stage resonator is the resonator at the opening 4a in FIG. 11, and the second-stage and third-stage resonators are the opening 4a.
The resonator in the b section, the fourth and fifth resonators have an opening 4c.
The resonator at the portion and the resonator at the sixth stage are the resonator at the opening 4d. The first-stage and sixth-stage resonators resonate in the mode in which the electric field component is oriented in the directions of the microstrip lines 8tx and 8ant shown in FIG. 11, and the resonance of the second harmonic of the dual-mode resonator in the opening 4b. Mode to the second stage resonator,
The fundamental mode is used as the third-stage resonator. Further, among the dual mode resonators formed in the opening 4c, the fundamental mode is used as the fourth stage resonator and the second harmonic mode is used as the fifth stage resonator. The second-stage and third-stage resonators are coupled by the presence of the protruding portion of the electrode protruding into the opening, as in the case shown in FIG. Similarly, the fourth-stage and fifth-stage resonators are also coupled, and the third-stage and fourth-stage resonators have electric field coupling between fundamental modes.

In this manner, a transmission filter having a band-pass characteristic composed of six stages of resonators is formed. Similarly, for the dielectric plate unit 100rx, a reception filter having a band-pass characteristic including six resonators is configured.

Next, an example of a high-frequency module according to the seventh embodiment will be described with reference to FIG. In FIG. 13, ANT is a transmitting / receiving antenna, DPX is a duplexer,
BPFa and BPFb are bandpass filters and AM, respectively.
Pa and AMPb are amplifier circuits, MIXa and MIX, respectively.
b is a mixer, OSC is an oscillator, and SYN is a frequency synthesizer.

MIXa represents the transmission intermediate frequency signal IF and SY
N is mixed with the signal output from N, and BPFa is mixed with MIXa
AMPa passes only the transmission frequency band of the mixed output signal from
Send more. AMPb amplifies the received signal extracted from DPX. BPFb allows only the reception frequency band of the reception signal output from AMPb to pass. MIXb
Mixes the frequency signal output from the SYN with the received signal and outputs a received intermediate frequency signal IF.

The BPFa and BPFb include first to fifth
The filter shown in the sixth embodiment is used, and the duplexer shown in the sixth embodiment is used for the DPX. As described above, a small high-frequency module is configured as a whole by using small filters and duplexers.

FIG. 14 is a block diagram showing the configuration of the communication device according to the eighth embodiment. This communication device is shown in FIG.
And a signal processing circuit. The signal processing circuit shown in FIG. 14 includes a voice codec, a TDMA synchronization control circuit, a modulator, a demodulator, and a C code.
A mobile phone is configured by connecting a microphone, a speaker, a display, a battery, and the like to an input unit of the signal processing circuit.

As described above, by using a small high-frequency module, a small communication device is constituted as a whole.

[0051]

According to the present invention, the one provided on the dielectric plate is provided.
By multiplexing a plurality of resonance modes having different directions and orders of the electromagnetic field in a resonator section formed by a set or a plurality of sets of openings, Qo can be improved, and the number of resonator stages can be increased. Small resonators, filters,
And a duplexer can be configured.

Further, according to the present invention, while the general shape of the opening is a simple rectangular shape, the fundamental resonance mode in which the electric field is directed in the long axis direction of the opening and the secondary resonance mode in which the electric field is directed in the short axis direction. And two resonators to be coupled to a pair of opposed electrode openings can be easily formed.

Further, according to the present invention, a small-sized high-frequency module and a communication device can be configured by using a small-sized filter or duplexer.

[Brief description of the drawings]

FIG. 1 is a perspective view of a dielectric resonator according to a first embodiment.

FIG. 2 is a diagram showing an example of an electric field distribution of each resonance mode in the dielectric resonator.

FIG. 3 is a diagram showing a relationship between dimensions of an electrode opening of the dielectric resonator and a resonance frequency.

FIG. 4 is a diagram showing a relationship between dimensions of electrode protrusions and a coupling coefficient in the dielectric resonator.

FIG. 5 is a view showing the shape of an electrode opening of a dielectric resonator according to a second embodiment.

FIG. 6 is a diagram showing an example of a shape of an electrode opening of a dielectric resonator according to a third embodiment and an electric field distribution of each resonance mode.

FIG. 7 is a diagram showing the relationship between the dimensions of electrode protrusions and the coupling coefficient in the dielectric resonator.

FIG. 8 is a view showing various shapes of an electrode opening of a dielectric resonator according to a fourth embodiment.

FIG. 9 is a perspective view showing a configuration of a dielectric filter according to a fifth embodiment.

FIG. 10 is a diagram showing an example of an electric field distribution in a resonator at each stage in the dielectric filter.

FIG. 11 is an exploded perspective view showing a configuration of a dielectric duplexer according to a sixth embodiment.

FIG. 12 is a diagram showing an example of an electric field distribution in a resonator at each stage of the dielectric duplexer.

FIG. 13 is a block diagram illustrating a configuration of a high-frequency module according to a seventh embodiment.

FIG. 14 is a block diagram showing a configuration of a communication device according to an eighth embodiment.

[Explanation of symbols]

 Reference Signs List 1-dielectric plate 2,3-electrode 4,5-opening 6-base plate 7-ground electrode 8-microstrip line (probe) 9-frame 10-spacer 11-cover 12-electromagnetic wave absorber block 100-dielectric Body plate unit p-projection d-recess

Claims (11)

[Claims] 1. An electrode having one or more sets of substantially rectangular openings facing each other on both main surfaces of a dielectric plate, and the openings of the dielectric plate serve as resonators. In a dielectric resonator, a plurality of resonance modes having different directions and orders of an electromagnetic field are multiplexed on a resonator unit including the one or more sets of openings. 2. A long side portion of an opening provided on at least one main surface of the dielectric plate such that the shape of the opening is non-symmetric with respect to a center line along a long side direction. A convex portion or a concave portion of the electrode is provided substantially at the center, and a fundamental resonance mode in which an electric field is directed in a long axis direction of the opening and a secondary resonance mode in which an electric field is directed in a short axis direction of the opening are coupled. Item 2. A dielectric resonator according to item 1. 3. The dielectric resonance according to claim 2, wherein a convex portion or a concave portion of the electrode is provided such that openings of the two main surfaces are asymmetric with respect to a center plane of the dielectric plate. vessel. 4. The dielectric resonator according to claim 2, wherein the protrusion or the recess of the electrode is provided such that the openings of the two main surfaces are plane-symmetric with respect to the center plane of the dielectric plate. . 5. The electrode according to claim 1, wherein the shape of the opening is non-linearly symmetric with respect to a center line along a long side direction, and the electrode is provided at a corner of the opening provided on at least one main surface of the dielectric plate. 2. The method according to claim 1, wherein a convex portion or a concave portion is provided, and a fundamental resonance mode in which an electric field is directed in a long axis direction of the opening and a secondary resonance mode in which an electric field is directed in a short axis direction of the opening are coupled. Dielectric resonator. 6. The dielectric resonance according to claim 5, wherein a convex portion or a concave portion of the electrode is provided such that openings of the two main surfaces are asymmetric with respect to a center plane of the dielectric plate. vessel. 7. The dielectric resonator according to claim 5, wherein a convex portion or a concave portion of the electrode is provided such that openings of the two main surfaces are plane-symmetric with respect to a center plane of the dielectric plate. . 8. A dielectric filter comprising: the dielectric resonator according to claim 1; and a signal input / output unit coupled to the resonator unit by an opening of the electrode. 9. A dielectric duplexer comprising the dielectric filter according to claim 8 provided as a transmission filter for passing a signal in a transmission frequency band and a reception filter for passing a signal in a reception frequency band. 10. A high-frequency module comprising: the dielectric filter according to claim 8, or the dielectric duplexer according to claim 9, and an antenna that radiates a transmission signal and receives a reception signal. 11. A communication device comprising: the high-frequency module according to claim 10; and a communication circuit that outputs a transmission signal to the high-frequency module and inputs a reception signal.