JPH0564882B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a dielectric resonator, and particularly to a dielectric resonator using a TM mode in which a columnar internal dielectric is disposed within a metal case.

(b) Prior Art Examples of conventional dielectric resonators using the TM mode are shown in FIGS. 7A and 7B. This example shows a portion of a dielectric resonator in a filter using a plurality of dielectric resonators, and FIG. In the figure,
6 and 7 represent the top plate and bottom plate of the metal case,
8, 9, 10a, 10b and 11a, 11b constitute side plates of the metal case, respectively. A cylindrical internal dielectric 1 is disposed at the center of such a metal case and between a top plate 6 and a bottom plate 7.
The internal dielectric 1 is made of dielectric ceramics such as titanium oxide, and both end surfaces 12 and 13 are bonded together using an organic conductive paste, solder, or the like. In this way, a dielectric resonator using the TM ₀₁₀ mode is constructed.

(c) Problems to be solved by the invention In a conventional TM mode dielectric resonator using such a metal case, a displacement current flows in the internal dielectric and an actual current flows in the case, so the internal dielectric Current concentrates at the joint between the end surface of the body and the inner wall surface of the case. However, as mentioned above, the joint between the end face of the internal dielectric and the inner wall of the case is connected with a conductive material with high specific resistance such as conductive paste or solder, which increases the Joule loss at the joint and causes resonance. There is a problem that the Q of the device decreases.
Therefore, by using a case in which an electrode film is formed on the inner wall surface of a case made of ceramic material, and connecting the inner wall surface of this case and the end surface of the internal dielectric material by baking using a silver paste with low resistivity, the above-mentioned problem can be solved. It will be resolved. However, in this case, the entire case is made of ceramic material, which has low impact resistance.
To solve this problem, the entire case must be made thicker. Further, there are problems such as a decrease in workability and an increase in manufacturing costs.

An object of the present invention is to provide a dielectric resonator that uses a metal case to solve the problems of impact resistance, workability, and manufacturing cost, and also prevents a decrease in Q due to an increase in Joule loss.

(d) Means for Solving the Problems The dielectric resonator of the present invention is a TM mode dielectric resonator in which a columnar internal dielectric is arranged in a metal case, and the dielectric resonator has an area larger than the end face of the internal dielectric. A flat ceramic body having at least one main surface coated with a conductive film is interposed between the end face of the columnar internal dielectric and the inner wall surface of the case, and the conductive film of the flat ceramic body and It is characterized by being connected to the inner wall of the case through a conductor.

(e) Effect In the dielectric resonator of the present invention, a flat ceramic body having a larger area than the end face of the internal dielectric and coated with a conductive film on at least one main surface is attached to the end face of the columnar internal dielectric. By interposing it between the conductor film and the inner wall surface of the case, the current spreads over a large area of the conductor film, and the current density is reduced. Therefore, the conductive film of the flat ceramic body and the inner wall surface of the case can be electrically connected using a conductive paste, solder, or a plate spring having a high specific resistance. On the other hand, if a conductive film is formed at the joint between the flat ceramic body and the end face of the internal dielectric, current will concentrate at the joint, but since this joint is a joint between ceramic materials, it has a low specific resistance. Since silver paste can be used, there is little Joule loss, and a decrease in Q of the resonator can be prevented.

(f) Embodiment FIG. 1 is a front sectional view showing the structure of a dielectric resonator according to an embodiment of the present invention, and FIG. 2 is a perspective view showing the structure of a part thereof. In both figures, 1 represents a cylindrical internal dielectric, and flat ceramic bodies 2 and 3 are bonded to both ends of this internal dielectric. The outer surfaces of the flat ceramic bodies 2 and 3 are coated with conductor films 2a and 3a by applying and baking silver paste, and as shown in FIG. The bonding is also done using silver paste. In FIG. 1, 6 and 7 represent the top plate and bottom plate of a metal case made of aluminum alloy, brass, etc. A leaf spring 4 is inserted between the flat ceramic body 2 and the top plate 6, and the bottom plate 7
A top plate spring 5 is inserted between the flat ceramic body 3 and the flat ceramic body 3. With this configuration, both end faces of the internal dielectric 1 and the flat ceramic bodies 2 and 3 are connected to each other.
Although the current is concentrated at the joint, the joint is made by baking an inorganic silver paste with low resistivity, so there is little Joule loss in this part. Further, as the current diffuses into the conductive film formed on the surface of the flat ceramic bodies 2 and 3, the current density is low in the surrounding area. Therefore, even if electrical continuity is established with the inner wall of the metal case through point contact with the leaf springs 4, 5, etc., there is little joule loss at the contact portions. As a result, a high Q dielectric resonator is constructed.

Although the above example was an example in which the flat ceramic body and the inner wall of the metal case were connected via a leaf spring, it is also possible to connect them using solder as shown in FIG. 3. In the figure, 14 is solder that joins the peripheral edge of the flat ceramic body 2 and the inner wall surface of the top plate 6, and 15 is the solder that joins the peripheral edge of the flat ceramic body 3 and the inner wall surface of the top plate 7. Each represents the solder to be used. Since the current density is low at the peripheral edge of the flat ceramic body, the Joule loss will not become large even if a conductive material such as solder having a relatively high resistivity is used for bonding.

FIGS. 4, 5, and 6 are diagrams showing still other embodiments, and particularly show the internal dielectric and the flat ceramic bodies formed on both end faces thereof. The example shown in FIG. 4 uses a flat ceramic body in which a conductive film is formed only on the surface facing the inner wall surface of the case. Bonding surface B between both end surfaces of internal dielectric 1 and flat ceramic bodies 2 and 3
1 and B2 are joined by applying glass glaze or the like and sintering. In this case, the current is diffused in the large-area conductive films 2a and 3a formed on one side of the flat ceramic bodies 2 and 3 and flows to the case, so that the current is not concentrated, and therefore the plate springs, solder, etc. It can be easily integrated into the case. FIG. 5 shows an example in which a flat ceramic body portion is integrally molded on both end portions of the internal dielectric body 1.
Conductive films 2a and 3a are provided only on the surfaces in contact with the inner wall surface of the case.
is formed. In this case as well, as in the example shown in FIG. 4, the concentration of current is alleviated, and the Joule loss can be kept low. The example shown in Fig. 6 uses a ceramic frame that resembles a rectangular parallelepiped without its front and rear walls; in other words, it consists of a top plate, a bottom plate, and two side plates continuous to these. A conductive film consisting of silver paste coating and baking is formed on all exposed surfaces. An internal dielectric 1 is bonded between the top plate and the bottom plate of such a frame using silver paste. A dielectric resonator is constructed by incorporating this structure into a metal case and connecting it to the inner wall surface of the metal case using a leaf spring, solder, or the like. In this case, the current concentrates at the joint between both end faces of the internal dielectric 1 and the frame 16;
Because they are joined using silver paste, there is little joule loss, and because the current density at the joint between the metal case and the frame is low, joule loss is not a problem even if they are joined using a leaf spring or solder.

(g) Effect of the Invention As described above, according to the present invention, a flat ceramic body having at least one main surface coated with a conductive film is provided between the end face of the internal dielectric and the inner wall face of the metal case. Due to the presence of the conductor film, the current is diffused by the conductive film of the flat ceramic body, reducing the Joule loss at the joint with the inner wall of the case, and preventing the Q of the resonator from decreasing. Moreover, since a case made of a metal material that is excellent in impact resistance, workability, and manufacturing cost can be used, a dielectric resonator can be constructed at low cost and with high reliability.

[Brief explanation of the drawing]

FIG. 1 is a front sectional view showing the configuration of a dielectric resonator according to an embodiment of the present invention, FIG. 2 is a perspective view showing the state of bonding between the internal dielectric and the flat ceramic body,
3 to 6 are diagrams showing a dielectric resonator and a part thereof according to other embodiments, and FIGS. 7A and 7B are a plan sectional view and a front sectional view showing an example of a conventional dielectric resonator. It is. 1... Internal dielectric, 2, 3... Flat ceramic body, 2a, 3a... Conductor film, 4, 5... Leaf spring, 6, 7... Metal case.

Claims (1)

[Claims] 1. In a TM mode dielectric resonator in which a columnar internal dielectric is disposed within a metal case, the area is larger than the end face of the internal dielectric and a conductor is provided on at least one main surface. A flat ceramic body coated with a film is interposed between the end face of the columnar internal dielectric and the inner wall surface of the case, and the conductive film of the flat ceramic body and the inner wall surface of the case are connected by a conductor. dielectric resonator.