JPH04361402A - Dielectric filter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to an integrated dielectric filter having a 1/4 wavelength type dielectric coaxial resonator structure. This invention relates to a dielectric bandpass filter polarized by adding a capacitive reactance element in parallel to a coupling means. This dielectric filter is used, for example, in various microwave communication devices.

0002

[Prior Art] As a technique for increasing the amount of out-of-band attenuation in an integrated dielectric filter without increasing the number of resonator stages, a plurality of resonators are formed in a dielectric block, and the distance between adjacent resonators is There is a method in which polarization is achieved by adding a reactance element in parallel with the coupling means to be coupled, and one example thereof is described in Japanese Patent Laid-Open No. 63-64404.

As shown in FIG. 6, the dielectric filter body has a plurality of (
Here, four (4) resonator holes 12 are formed and their inner surfaces are metallized to form inner conductors 14. Connector holes 16 are provided between adjacent resonator holes 12, and four sides of the dielectric block 10 are metalized. The inner conductor 14 and the outer conductor 18 are bonded together using a metallized layer (
(not shown). Each resonator is constituted by the inner conductor 14, the outer conductor 18, and the dielectric material between them.

Here, as shown in detail in FIG. 7, resin molded terminals 2 are attached to the first stage resonator and the other stage resonators, respectively.
Insert 0,21. The resin mold terminals 20 and 21 are
The structure is such that resins 24 and 25 surround the outsides of metal pins 22 and 23, respectively. Metal pins 22, 23 and inner conductor 14
A desired capacitance is formed between the two. Then, they are connected to each other by a substrate 28 having a conductive pattern 26. The resin molded terminal 20 constitutes a first-stage coupling capacitor, and the resin molded terminal 21 serves as a capacitive reactance element. This addition of coupling capacitance creates a pole and increases out-of-band attenuation.

[0005]

Incidentally, the coupling reactance for polarization is generally a very small value (usually 1 pF or less), and the characteristics of the filter change with slight fluctuations and dispersions. Therefore, a structure in which a resin molded terminal is used as a reactance element as shown in FIGS. 6 and 7 is not suitable because there are many variable factors such as the resonator hole diameter and the fitting size of the resin. It is also inconvenient to make fine adjustments.

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to provide a polarized dielectric filter having a structure that has few fluctuation elements, can accurately realize a small coupling capacitance, and is easy to finely adjust. It is to be.

[0007]

[Means for Solving the Problems] The present invention includes integrally forming three or more resonators in a dielectric block, coupling adjacent resonators by a coupling means, and connecting a reactance element in parallel with the coupling means. This is a dielectric filter that is polarized by adding . Its characteristics lie in the configuration of the capacitive reactance element added for the first-stage coupling capacitance and polarization, and in both cases, a capacitor block made of a dielectric separate from the dielectric block is provided outside the dielectric block. , the desired capacitance is formed by the capacitor block.

The capacitor block has a plurality of holes, and electrodes are provided on the inner surface of the holes and a part of the outer surface of the capacitor block to obtain a coupling capacity with the first stage resonator. A second capacitor portion functioning as a reactance element is formed. Then, an external connection terminal is connected to the common electrode of both capacitor sections, and the other two electrodes are connected to the inner conductors of the first-stage and other-stage resonators using conductors, respectively.

[0009] The capacitor block has first and second through holes extending in the horizontal direction, electrodes are formed on the inner surface thereof, and a surface is formed on the top or side surface of the capacitor block opposite to the first hole. There is a structure in which electrodes are formed, an external connection terminal is connected to a first hole electrode, and a second hole electrode and a surface electrode are connected to an inner conductor using a conductor. In this case, a structure in which the patterns of both hole electrodes are extended until they are close to each other on the side surface of the capacitor block is also included. Preferably, the capacitor block has an inverted convex shape with a protruding lower center portion, and a conductive film for case attachment is formed on the protruding lower surface.

The first stage resonator here refers to a resonator formed at the end of the dielectric block, and in actual use it is not only the first stage (input side) in the strict sense but also the final stage (input side). (output side) is also included. Therefore, it may be provided not only in the first stage in a narrow sense, but also only in the final stage, and includes cases in which it is provided in both the first stage and the final stage. Further, other resonators are resonators other than the first stage (including the final stage), and include not only resonators adjacent to the first stage but also resonators that are not adjacent and are apart.

[0011]

[Operation] Two capacitor sections are constituted by a single capacitor block and the electrodes formed thereon, one of which serves as a first-stage coupling capacitance, and the other serves as a capacitive reactance element for polarization. Coupling capacitance can be set accurately by molding the capacitor block and by pattern printing the electrodes. By changing the shape of the electrodes and appropriately selecting the capacitance value, a filter having an attenuation pole at a predetermined frequency can be realized. The coupling capacitance of the first stage and the coupling capacitance for polarization can be easily adjusted by cutting the electrodes even after assembly.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an overall perspective view showing an embodiment of a dielectric filter according to the present invention. The dielectric filter body may have a configuration similar to that of the prior art as shown in FIG. Therefore, the same reference numerals are used for ease of understanding. A plurality of (four in this case) resonator holes 12 are formed in the longitudinal direction of a rectangular parallelepiped dielectric block 10 made of dielectric ceramic for microwaves, and the inner surface is metalized to form an inner conductor 14, and the adjacent resonator holes are A connector hole 16 is provided between the connector holes 12. Then, four sides of the dielectric block 10 are metallized to form an outer conductor 18, and the inner conductor 14 and the outer conductor 18 are short-circuited by a metallized layer (not shown) on one side of the dielectric block 10. A resonator is configured by each inner conductor 14, outer conductor 18, and the dielectric between them.

A capacitor block 30 made of a dielectric separate from the dielectric block 10 is provided outside the dielectric block 10. This capacitor block 30 has a substantially rectangular parallelepiped shape, has an inverted convex shape with a protruding center on the lower surface, and has first and second through holes 31 and 32 in the lateral direction. These through holes 31 and 32 are provided at positions away from the protrusion 30a. Then, first and second hole electrodes 33 and 34 are formed on the inner surfaces of both through holes 31 and 32, respectively, and a surface electrode 35 is formed on the upper surface of the capacitor block near the first through hole 31. Further, a case attachment conductor film 38 is provided on the protruding lower surface of the capacitor block 30. The external connection terminal 40 is inserted into the first through hole 31 and connected to the first hole electrode 33 . Then, the surface electrode 35 and the inner conductor of the first stage resonator are connected, and the second hole electrode 34 and the inner conductor of the second stage resonator are connected by conductive wires 42, respectively. The conductive wire 42 is preferably a wire having a small coefficient of thermal expansion, such as Kovar, and plated with silver, copper, solder, or the like to improve conductivity.

As shown in FIG. 2, an initial coupling capacitance Ci between the first hole electrode 33 and the surface electrode 35 opposite thereto is
is formed, and the coupling capacitance Cp formed between the first and second hole electrodes 33 and 34 functions as the capacitive reactance element. Since it is sufficient to obtain a small capacitance of about 1 pF for the coupling capacitance Cp, the double-hole electrode 3
There is no problem even if 3 and 34 are formed separately. FIG. 3 shows a first stage resonator 51 and a second stage resonator 5 in the above embodiment.
This is an equivalent circuit of part 2. The coupling capacitance Cp is added in parallel with the inter-resonator coupling means M, thereby polarizing the filter characteristics. An example of filter characteristics is shown in FIG. In the same figure, the characteristics shown by the solid line represent the characteristics of the dielectric filter of the present invention, and the attenuation pole P is on the high frequency side.
is occurring. Note that the characteristics shown by the broken line are obtained when there is no coupling capacitance Cp due to the reactance element for polarization (
Comparative example).

The dielectric filter body is placed horizontally in a case (not shown), and the capacitor block 30 is also installed in the case. Both are fixed by soldering. The capacitor block 30 has an inverted convex shape, and the hole electrodes 33, 3
By increasing the distance between 4 and the case, the grounding capacity is kept as small as possible.

If the capacitor block is provided outside the dielectric block and connected to it by a conductive wire as described above, the coupling capacitance Ci of the first stage is connected to the surface electrode 35 or the first hole electrode 3.
3, and the coupling capacitance Cp is the first hole electrode 33 or the second hole electrode 33.
This can be adjusted by cutting the hole near the electrode 34.

Another example of the structure of the capacitor block is shown in FIG. Since it is basically the same as in FIGS. 1 and 2, the same reference numerals are given to corresponding parts, and the description thereof will be omitted. In this example, patterns of double-hole electrodes 33 and 34 functioning as capacitive reactance elements are extended so as to be close to each other on the side surface of the capacitor block 30. The capacitance can be increased by the extended patterns 43 and 44, and the capacitance can be easily adjusted by scraping them off. Although the surface electrode is formed on the upper surface of the capacitor block in the above example, it may be provided on the end surface.

Note that the reactance element as described above may be added not only to the input side but also to the output side (final stage), or may be added to both the input side and the output side. By adding reactance elements to both the input and output sides, two attenuation poles can be obtained. Further, it is also possible to connect the reactance element not only to the resonator adjacent to the first stage (or final stage) resonator but also to other resonators separated from the resonator.

[0019]

Effects of the Invention As described above, the present invention forms a capacitor serving as a first-stage coupling capacitor and a capacitive reactance element by a capacitor block outside the dielectric filter body. The pattern determines the capacitance. The shape of the capacitor block is determined by the molding die, and the electrode pattern can be applied by pattern printing, so there are few variables and small coupling capacitance can be achieved with high precision. Further, since the capacitance can be finely adjusted by scraping off a part of the surface electrode or the hole electrode, a dielectric filter exhibiting desired polar filter characteristics can be easily obtained.

[Brief explanation of drawings]

FIG. 1 is an overall perspective view showing an embodiment of a dielectric filter according to the present invention.

FIG. 2 is a perspective view showing an example of a capacitor block used in the dielectric filter of FIG. 1;

FIG. 3 is an equivalent circuit diagram of the first-stage and second-stage resonators of the dielectric filter in FIG. 1;

FIG. 4 is a graph showing an example of filter characteristics of the dielectric filter of FIG. 1;

FIG. 5 is a perspective view showing another example of a capacitor block used in the present invention.

FIG. 6 is an overall perspective view showing an example of conventional technology.

7 is a partial sectional view of the first stage and second stage of the dielectric filter of FIG. 6. FIG.

[Explanation of symbols]

10 Dielectric block 12 Resonator hole 14 Inner conductor 16 Connector hole 18 Outer conductor 30 Capacitor block 31 First through hole 32 Second through hole 33 First hole electrode 34 Second hole electrode 35 Surface electrode 40 External connection terminal 42 Conductor wire

Claims (3)

[Claims] [Claim 1] Three or more resonators are integrally formed in a dielectric block, adjacent resonators are coupled by a coupling means, and a reactance element is added in parallel with the coupling means to polarize the resonators. In the dielectric filter, a capacitor block made of a separate dielectric material having a plurality of holes is installed outside the dielectric block, and electrodes are provided on a part of the outer surface of the capacitor block and on the inner surface of the holes to generate the first stage resonance. forming a first capacitor section for obtaining a coupling capacitance with the device and a second capacitor section functioning as the reactance element, and connecting an external connection terminal to a common electrode of both capacitor sections;
A dielectric filter characterized in that the other two electrodes and the inner conductors of the first-stage and other-stage resonators are connected by conductors, respectively. 2. A capacitor block is provided with first and second through holes extending in the horizontal direction, electrodes are formed on the inner surface of the capacitor block, and a surface electrode is formed on the top or side surface of the capacitor block opposite to the first through hole. and connect the external connection terminal to the first hole electrode,
The dielectric filter according to claim 1, wherein the second hole electrode and the surface electrode are connected to the inner conductor. 3. The dielectric filter according to claim 2, wherein the capacitor block has an inverted convex shape with a protruding lower center portion, and a conductive film for mounting the case is formed on the protruding lower surface.