JPH0611081B2 - Dielectric resonator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a dielectric resonator utilizing a TE ₀₁ δ mode.

(b) Background of the Invention A dielectric resonator is generally smaller than a conventional metal cavity resonator and can have a high Q. In particular, a dielectric resonator device used as a bandpass filter is a microresonator. It is used as a transmitter multiplexer in a wave communication device.

The structure of the dielectric resonator differs depending on the electromagnetic wave mode used, and the mode according to the purpose is used. For example, TE ₀₁ δ is not so good in spurious characteristics, but the energy concentration of the resonator is high, and the loss of the entire resonator is determined only by the loss of the dielectric resonator, and a high Q can be obtained. In the case of TEM, spurious characteristics are good, but the loss of the metal conductor is relatively large, and the Q of the resonator is not so high. In the case of TM, which exhibits an intermediate characteristic between the above two modes, since a real current flows through the junction surface between the dielectric resonator and the case, it is necessary to keep the conduction state of this junction surface good. Therefore, it is necessary to absorb the mechanical strain due to the difference in thermal expansion coefficient between the dielectric resonator made of ceramic and the case, and the metallized ceramic must be used as the material of the case. Therefore, in order to use a highly workable metal as the case and increase the Q,
A TE ₀₁ δ mode dielectric resonator is used.

(c) Prior Art A dielectric resonator utilizing TE ₀₁ δ mode has already been filed by the same applicant (Japanese Patent Application No. 62-008525), which has good spurious characteristics, is small in size, and can be used for relatively high power. FIG. 12 shows the structure of a bandpass filter using a dielectric resonator that can be used. In the figure, reference numerals 1 and 2 denote case members made of a metal material that form a box-shaped case by a combination of the two. N-type connectors 3 and 4 for input and output are attached to the side surface of the case member 1. ing. Inside the metal case, a metal plate 6 that stands upright in the center is provided. A plurality of ceramic substrates 7 are incorporated on both side surfaces of the metal plate 6 and the bottom surface of the case member 1, respectively. The entire surface of the ceramic substrate 7 is covered with a silver electrode to form an electric wall. In contact with the electric wall, a dielectric resonator having a shape obtained by dividing a cylindrical dielectric resonator into four is fixed by baking onto the silver electrode. Eight of these dielectric resonators are housed in the case.

FIG. 13 shows a current path for one of the dielectric resonators 57. Dielectric resonator 5
A displacement current i ₀ flows in the dielectric body 7 in the direction indicated by the broken line in the figure, and the silver electrode formed on the surface of the ceramic substrate is joined to the dielectric body, and the silver electrode on the surface of the ceramic substrate and the inner wall of the case member. The real currents i ₁ and i ₂ respectively flow in the. In this way, it operates as a TE ₀₁ δ mode dielectric resonator similar to the cylindrical dielectric resonator before being divided into four.

(d) Problems to be Solved by the Invention In such a dielectric resonator utilizing the TE ₀₁ δ mode, as shown in FIG. 13, the actual current path is more ceramic than the case inner wall. because the shorter passing through the silver electrode substrate, increases the current i1 flowing through the silver electrode of the ceramic substrate, i ₂ is to flow slightly as leakage current in the case inner wall. By the way, when an actual current flows through the silver electrode on the ceramic substrate or the inner wall of the case, a Joule loss occurs, but since the Joule loss is related to the squared value of the current, the concentration of the current increases the Joule loss as a whole. It was the cause. Due to the increase in Joule loss, not only the amount of heat generated increases, but also the Q of the resonator decreases.

An object of the present invention is to provide a dielectric resonator which prevents current concentration, has a small Joule loss as a whole, and has a high Q.

(e) Means for Solving the Problems In the dielectric resonator of the present invention, a dielectric is placed in contact with an electric wall forming one or two planes, and a straight line on the one electric wall or the two In a TE ₀₁ δ mode dielectric resonator in which the line of intersection of two electric walls is the central axis of the electromagnetic field distribution, a cavity is provided in the vicinity of the central axis.

(f) Action In the dielectric resonator of the present invention, by arranging the dielectric in contact with the electric wall forming one or two planes, the straight line on the one electric wall or the two electric walls A TE ₀₁ δ-mode dielectric resonator having an intersection line as the central axis of the electromagnetic field distribution is constructed, and a cavity is provided in the vicinity of the central axis, so that the distribution of displacement current in the dielectric is kept away from the central axis. The path of the actual current flowing through the electric wall becomes relatively long as compared with the case without the cavity. As a result, the current flowing through the electric wall is dispersed without being concentrated in the vicinity of the central axis, and the Joule loss is reduced as a whole. Therefore, a dielectric resonator having a high Q can be constructed.

(g) Embodiment FIG. 1 is a partially cutaway perspective view showing the structure of a bandpass filter using the dielectric resonator of the present invention. In the figure, reference numerals 1 and 2 denote case members made of a metal material that form a box-shaped case by a combination of the two. N-type connectors 3 and 4 for input and output are provided on a side surface of the case member 1.
Is attached. A metal plate 6 is provided upright in the center of the metal case, and a plurality of ceramic substrates 7 are incorporated on both side surfaces of the metal plate 6 and the bottom surface of the case member 1. The entire surface of the ceramic substrate 7 is covered with a silver electrode. In contact with this electrode, a dielectric resonator having a shape obtained by dividing a donut-shaped dielectric resonator into four is fixed by baking onto the silver electrode.
In the dielectric resonator having such a structure, since the electric wall in the TE ₀₁ δ-mode dielectric resonator exists at the position where this electrode exists, the dielectric resonator similar to the cylindrical dielectric resonator before being divided into four parts is obtained. TE ₀₁ Operates as a δ mode dielectric resonator. These dielectric resonators are 8 of 51-58 in the case.
Individual pieces (only 52 to 54 are shown in the figure) are stored. In addition, L is the third-stage resonator 53 and the sixth
A loop for magnetic field coupling with the resonator (56) of the stage, S is the resonator 54 of the fourth stage and the resonator (5 of the fifth stage
5) It is a slit for magnetic field coupling with.

FIG. 2 is a cross-sectional view of the device shown in FIG. 1, showing a cross-section of a plane parallel to the end faces on which the connectors 3 and 4 are formed. In the figure, reference numerals 52 and 57 denote dielectric resonators, respectively, and the divided surfaces 52a, 52b and 57a, 57b are respectively fixed to the vertical surfaces 7a, 7a of the ceramic substrates 7, 7 and the horizontal surfaces 7b, 7b by baking. The inner wall 2a of the case member 2 is formed into a cylindrical surface centered on the central axis of the dielectric resonator. In the figure, reference numeral 8 is a frequency tuning adjusting screw, which is made of metal or dielectric and is screwed into a screw hole provided in a corner portion of the case member 2 as shown in the drawing to rotate the adjusting screw 8. As a result, the tip portion 8a is projected into the case, and frequency tuning is performed according to the amount of projection.

FIG. 7 shows a current path of the dielectric resonator 57 shown in FIG. In the dielectric of the dielectric resonator 57, an electromagnetic field distribution having a donut-shaped central axis O as the central axis is generated, a displacement current i ₀ flows in the direction shown by the wavy line in the figure, and the silver electrode 7a on the surface of the ceramic substrate 7 7b and the dividing surface 5 of the dielectric
The actual current i ₁ flows between the joint portions with the 7a and 57b, and the actual current i ₂ flows through the inner wall 2a of the case member 2. As shown in the figure, the distribution of the displacement current in the dielectric moves away from the central axis O, so the currents flowing in the conductors are dispersed as i ₁ and i ₂ .
Current is not concentrated near the central axis, and Joule loss is reduced as a whole.

Here, the Joule loss in the conductor is 1 / Q ', the unloaded Q
Is Q ₀ and the unloaded Q in the original cylindrical dielectric resonator which is not a four-divided shape is Q _0o , the following relationship holds.

Q ′ = (πμ ₀ ω / 4R _s ) · <r> − (1) 1 / Q ₀ = (1 / Q _0o ) + (1 / Q ′) − (2) where <r> = ∫rH ² drdz / ∫H ² drdz- (3) The average <r> of the magnetic field spread can be calculated by the finite element method based on the definition of the equation (3), and FIG. 8 shows the change of Q ₀ in each dimension of the dielectric resonator and the case. As is clear from the figure, Q ₀ can be increased by using a dielectric resonator from which the dielectric near the central axis is removed.
For example, the inner diameter Rc of the case is 55 mm, the outer radius Ro of the dielectric resonator is 41 mm, and the inner radius Rx of the dielectric resonator is Rx.
By setting the outer radius Ro to 0.35, the theoretical value of Q ₀ was 7500, and 7100 was obtained as the measured value.

Although the dielectric resonator 57 and the like generate heat due to dielectric loss and Joule loss of the peripheral conductor, the heat is radiated to the outside from the case members 1 and 2 via the ceramic substrate 7 and the metal plate 6. Further, at this time, since the dielectric resonator 57 and the like are fixed via the ceramic substrate 7 adhered to the case member, thermal expansion of the case member made of the metal material and the dielectric resonator made of the ceramic material occurs. The mechanical strain due to the difference can be absorbed, and the complete T without causing the peeling of the joint portion between the silver electrode and the dielectric resonator on the surface of the ceramic substrate.
It becomes possible to maintain the excitation of the E ₀₁ δ mode.

FIG. 3 shows a vertical cross section perpendicular to the side surface of the case member to which the connector 3 is attached in FIG. In the figure, 51 is a first-stage dielectric resonator, 9 is a stripline substrate, and 10 is a lead wire connecting the input connector 3 and the stripline 9. FIG. 4 is a perspective view showing this portion,
As shown in the figure, the strip line 9 is a strip substrate 9
The lead wire 10 connects the center conductor of the input connector 3 and the strip conductor 9b. A silver electrode is formed on the bottom of the first-stage dielectric resonator 51 and is connected to the strip conductor 9b in a direct current manner. In this way, the dielectric resonator and the input connector are electrically connected, and a similar circuit is formed on the output side. Of course, the external coupling structure may be replaced with a conventionally known structure, for example, various other structures such as a coupling structure using a loop.

As described above, the bandpass filter using the 8-stage dielectric resonator is constructed. FIG. 5 shows the equivalent circuit. In the figure, Qe1 shows the coupling portion between the connector 3 and the first-stage dielectric resonator 51, and Qe2 shows the coupling portion between the eighth-stage dielectric resonator (58) and the connector 4. Also, k12, k23, k34, k45,
k56, k67, and k78 each represent a coupling portion between the dielectric resonators in the number of stages indicated by the two-digit number. Further, k36 is the third value due to the existence of the coupling loop L shown in FIG.
The dielectric resonator 53 of the stage and the dielectric resonator (5
6) represents the connecting part with.

Specific examples of constituent materials and respective dimensions of the bandpass filter shown above, and characteristic examples under the conditions are shown below.

FIG. 6 shows the material of each resonator and the ceramic substrate that holds these resonators. FIG. 9 shows the specifications of the bandpass filter constructed under such conditions. In this way, a bandpass filter with low insertion loss and large attenuation can be constructed.

In the above embodiment, when the dielectric resonator was brought into contact with the inner wall of the case and fixed, a ceramic substrate having a silver electrode on the surface was used. However, as in the present invention, the dielectric resonator is used. Since the electric current does not concentrate on the local portion of the joint surface between the electric wall and the electric wall, it is possible to fix it to some extent roughly with an elastic body made of a metal material as shown in FIG. In the figure, 14 is a corrugated metal plate or metal net, which is partially fixed by soldering or using a synthetic resin adhesive such as epoxy.

Further, the above embodiment is an example in which a dielectric resonator having a shape obtained by dividing a donut-shaped dielectric into four is used. However, for example, as shown in FIGS. It is also possible to use a dielectric resonator in which the through hole H is formed by partially removing the dielectric near the central axis, and similarly, the concentration of the current near the central axis is relaxed to disperse the current distribution. Is possible.

(h) Effects of the Invention As described above, according to the present invention, it is possible to downsize the entire dielectric resonator device by using the small dielectric resonator and the case, and the current is concentrated on the local part of the conductor. It is possible to prevent the Q of the resonator from decreasing due to an increase in Joule loss.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view showing an example of a bandpass filter using a dielectric resonator of the present invention, FIG. 2 is a vertical sectional view of the same device, and FIG. 3 is a part of the device shown in FIG. FIG. 4 is a longitudinal sectional view, FIG. 4 is a perspective view of a portion shown in FIG. 3, FIG. 5 is an equivalent circuit of the bandpass filter, and FIG. 6 is a material and characteristics of a resonator and a ceramic substrate which constitute the device. Fig. 7 is a diagram showing the current flowing in the dielectric resonator and the conductor, and Fig. 8 is each dimension of the dielectric resonator and the case and no load Q.
FIG. 9 is a diagram showing the characteristic obtained as a concrete band pass filter, FIG. 10 is a longitudinal sectional view showing the fixing structure of the dielectric resonator according to another embodiment, and FIG. (A) and (B) are sectional views showing the structure of a dielectric resonator according to another embodiment, and FIG. 12 is a partially cutaway perspective view showing the structure of a bandpass filter using a conventional dielectric resonator. , First
FIG. 3 is a diagram showing a current flowing through a dielectric resonator and a conductor used in the device. 1, 2 ... Case member, 6 ... Metal plate, 7 ... Ceramic substrate, 51-58 ... Dielectric resonator.

Claims (1)

[Claims] 1. A dielectric is arranged in contact with an electric wall forming one or two planes, and a straight line on the one electric wall or a line of intersection of the two electric walls is used as a central axis of the electromagnetic field distribution. TE
_{01 A} δ-mode dielectric resonator, wherein a cavity is provided near the central axis.