JPH04361401A - Dielectric filter - Google Patents

Abstract

PURPOSE:To realize a coupling capacitor with a small capacitance being a reactance element of a polar dielectric filter with high precision and to attain ease of fine adjustment. CONSTITUTION:Three resonators or over are formed to a dielectric block and a reactance element is added in parallel with a coupling means between adjacent resonators to make polarization. A 1st capacitor board 30 forming a 1st stage coupling capacitor and a 2nd capacitor board 34 being a reactance element are laminated at the outside of the dielectric block. An external connection terminal 40 is connected to the capacitor board and an inner conductor 14 and both the capacitors are connected respectively by a conductor 38. Two capacitors are formed to a single capacitor board.

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 first-stage coupling capacitance and the capacitive reactance element added for polarization.In both cases, a capacitor substrate is provided outside the dielectric block, and the desired capacitance is formed by the capacitor substrate. are doing.

Specifically, a first capacitor substrate for obtaining a coupling capacitance with the first stage resonator and a second capacitor substrate that supports the first capacitor substrate and functions as the reactance element are used. Then, one electrode of both capacitor boards is connected together and an external connection terminal is connected between the inner conductor of the first stage resonator and the other electrode of the first capacitor, and between the inner conductor of the other resonator and the first capacitor. The other electrodes of the two capacitors are connected to each other by conductors.

Another example is a structure in which a first capacitor section for obtaining a coupling capacitance with the first stage resonator and a second capacitor section functioning as the reactance element are formed on the same capacitor substrate. In this case, the external connection terminal is connected to the back common electrode, and the connection terminal is connected between the inner conductor of the first stage resonator and the surface electrode of the first capacitor section, and between the inner conductor of the other resonator and the surface of the second capacitor section. Connect each electrode with a conductor.

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 not adjacent to the first stage.

[0011]

[Operation] A first-stage coupling capacitance is formed between the electrodes on both sides of the first capacitor substrate or capacitor section. Further, the coupling capacitance formed by the second capacitor substrate or the capacitor section serves as a reactance element for polarization. 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 first capacitor substrate 30 and a second capacitor substrate 34 on which it is mounted are provided outside the dielectric block 10. The first capacitor substrate 30 is made of a material with a high relative permittivity in order to be as compact as possible, and electrodes 31 and 32 are formed on both surfaces to form a capacitor with electrodes facing each other. The second capacitor board 34 has a thick plate structure using a material with a small dielectric constant, and has two electrodes 35 on the top surface, since it is sufficient that a ground plate such as a case is located on the bottom surface and a small capacitance of about 1 pF is obtained. , 36 are placed close together to form a planar capacitor. The electrodes 35 of the second capacitor substrate 34 and the electrodes 32 of the first capacitor substrate 30 are joined by soldering or the like in a manner such that a thin plate-shaped external connection terminal 40 is sandwiched between them. Then, the electrode 31 and the inner conductor of the first-stage resonator and the electrode 36 and the inner conductor of the second-stage resonator are connected by conductive wires 38, respectively. The conductive wire 38 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. Although not shown, the dielectric filter body is placed horizontally in the case, and the second capacitor board 34
is also installed inside the case. Both are fixed by soldering. By making the second capacitor substrate 34 thick and reducing its dielectric constant, the ground capacitance is kept as small as possible.

The shape and connection state of the external connection terminal may be as shown in FIG. A thin plate-shaped external connection terminal 40 is formed along the second capacitor board 34,
It is connected to the electrode 35 without being sandwiched between the two substrates. With such a configuration, it becomes easy to bond the capacitor substrates together, and it also becomes easy to connect the external connection terminal 40 to an external circuit or the like. Since the other configurations are the same as those in FIG. 1, the explanation will be omitted.

FIG. 3 shows an equivalent circuit of the first stage and second stage parts in the above embodiment. First capacitor board 30
External connection terminal 40 is connected by electrodes 31 and 32 on both sides.
A first-stage coupling capacitance Ci is formed between the first-stage resonator 41 and the first-stage resonator 41 . Further, a coupling capacitance Cp is formed between the second capacitor substrate 34 and the second stage resonator 42 by the electrodes 35 and 36 on its surface. This coupling capacitance 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 a comparative example that does not have the coupling capacitance Cp due to the reactance element for polarization.

If the capacitor substrate is provided outside the dielectric block and connected with a conductive wire as described above, the coupling capacitance Ci of the first stage is connected to the electrode 31, and the coupling capacitance Cp is connected to the electrode portion near the electrodes 35 and 36. It can be adjusted by cutting.

Another configuration example of the capacitor is shown in FIG. 5A. Since it is basically the same as the case of FIG. 1, corresponding parts are given the same reference numerals and their description will be omitted. This serves as a second capacitive reactance element.
This is an example in which the electrodes 35 and 36 of the capacitor substrate 34 are combined into an uneven pattern to increase the capacitance.

Still other configuration examples of capacitors are shown in FIGS. 5B to 5D.
Shown below. These are basically examples using a single capacitor board. In the case shown in B, a full-surface electrode 52 is formed on the back surface of a capacitor substrate 50, and two electrodes 54 and 55 are formed on the front surface at positions separated from each other. It is placed on another insulating substrate 56, and the external connection terminal 40 is sandwiched between them. An initial coupling capacitance is formed between the back surface electrode 56 and one surface electrode 54, and a capacitive reactance element (
coupling capacitance) is formed. The example shown in C is a modification of the example B, and has a structure in which leg portions 62 are provided at both ends of the capacitor substrate 60, and the insulating substrate is omitted. The legs 62 allow the back electrode 56 to float above the mounting surface. A conductor layer is formed on the lower surface of both legs 62 and attached to a case etc. by soldering. Furthermore, D is a modified example,
A resin 64 is molded into the recess on the bottom surface, and an external connection terminal 40 is formed.
This increases the strength of the connection. In either example, the purpose of raising the position of the capacitor board by providing an insulating board or forming legs is to minimize the ground capacitance.

Note that the above reactance element 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.

[0020]

Effects of the Invention As described above, the present invention forms a capacitor serving as an initial coupling capacitor and a capacitive reactance element using a capacitor substrate outside a dielectric filter body. The capacitance is determined by the pattern, 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 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 coupling capacitance portion used in the dielectric filter of FIG. 1;

FIG. 3 is an equivalent circuit diagram of the first stage and second stage portions 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 the coupling capacitance portion used in the dielectric filter of 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 First capacitor board 31, 32 Electrode 34 Second capacitor board 35, 36 electrode 38 Conductor 40 External connection terminal

Claims (2)

[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, the dielectric block includes a first capacitor substrate for obtaining a coupling capacitance with the first stage resonator, and a second capacitor substrate that supports the first capacitor substrate and functions as the reactance element. It connects one electrode of both capacitor boards to each other and connects the external connection terminal, and connects the inner conductor of the first stage resonator and the other electrode of the first capacitor and the other resonator. A dielectric filter characterized in that the inner conductor and the other electrode of the second capacitor are connected by conductors. [Claim 2] 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 for polarization. In the dielectric filter, a first capacitor section for obtaining a coupling capacitance with the first stage resonator and a second capacitor section functioning as the reactance element are mounted on a single capacitor substrate provided outside the dielectric block. The external connection terminal is connected to the back common electrode, and the connection terminal is connected between the inner conductor of the first stage resonator and the surface electrode of the first capacitor section, and between the inner conductor of the other resonator and the surface electrode of the second capacitor section. A dielectric filter characterized in that each of the two is connected by a conductor.