JPH06326503A - Dielectric filter - Google Patents

Abstract

PURPOSE:To provide a dielectric filter of such an electrostatic capacity coupling structure that has the excellent temperature characteristics, the desired electrostatic capacity value of high precision and also a high degree of designing freedom. CONSTITUTION:A dielectric filter is provided with a coupling substrate 3 consisting of the capacitor electrodes 7, 8... which are formed on a dielectric board having the excellent temperature characteristic and the capacitors 11 and 12 which are prepared separately from the substrate 3. In such a constitution, the necessary electrostatic capacity is acquired with high precision.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a dielectric filter having a capacitance coupling structure which is excellent in temperature characteristics, has a high precision of a desired capacitance value, and has a high degree of freedom in design.

[0002]

2. Description of the Related Art An example of a dielectric filter using a dielectric coaxial resonator is shown in a perspective view of FIG. 5 and an equivalent circuit thereof in FIG. In this dielectric filter 30, three dielectric coaxial resonators 2 are arranged in parallel, a coupling substrate 3 is arranged on the open side end face 2b side of each resonator 2, and this is placed in a metal case (not shown). It is housed and configured to function as a three-stage bandpass filter.

A coupling terminal 5 is inserted into a resonator hole 4 formed in the axis of each coaxial resonator 2, and a part of the coupling terminal 5 projects from the open side end face 2b side. .

On the surface 3a of the combined substrate 3, comb-shaped capacitor electrodes 7, 8 and 9 extending in the longitudinal direction thereof are formed by patterning, and each of the capacitor electrodes 7, 8 and 9 is formed.
The tip of the coupling terminal 5 of the coaxial resonator 2 is soldered to. Further, on the back surface 3b of the coupling substrate 3, capacitor electrodes 6, 10 (not shown) are formed so as to face the capacitor electrodes 7, 9 with the substrate 3 interposed therebetween.

One end of each of the input and output terminals 13 and 14 is soldered to each of the capacitor electrodes 6 and 10.
The other end projects outward from the metal case (not shown).

The capacitor electrodes 7, 8 and 9 formed on the front surface 3a of the combined substrate 3 are shown in FIG.
FIG. 3 shows the capacitor electrodes 6 and 10 formed on b.

With the structure described above, the capacitor C1 is formed between the electrodes 6 and 7 and the portion of the combined substrate 3 sandwiched therebetween, the capacitor C2 is formed between the electrodes 7 and 8 and the portion of the combined substrate 3 interposed therebetween, and the electrodes 8 and 9
And the coupling substrate 3 portion between them, the capacitor C3 is connected to the electrode 9,
10 and the portion of the combined substrate 3 sandwiched between them, the capacitance C4
Therefore, the adjacent coaxial resonators 2 are capacitively coupled to each other.

[0008]

However, when designing a dielectric filter having a capacitive coupling structure having excellent temperature characteristics and a high precision of a desired capacitance value with the above structure, the dielectric filter is used as a coupling substrate. The design of the dielectric plate is difficult because there are a limited number of dielectric plates made of a material that can be used with good temperature characteristics and can obtain a desired capacitance with a predetermined size and shape.

As a method of solving this, there is a method of obtaining the capacitance by using, for example, a commercially available chip capacitor without using a coupling substrate, but in general, the chip capacitor has a large capacitance variation and is difficult to use.

It is an object of the present invention to obtain a dielectric filter having an excellent temperature characteristic and having a capacitance coupling portion having a desired capacitance value, which can be easily designed.

[0011]

According to the present invention, in a dielectric filter having a capacitance coupling portion, a coupling substrate formed by forming a capacitor electrode on a dielectric plate and a capacitor formed separately from the coupling substrate are provided. And the required capacitance is obtained by the capacitance obtained by the coupling substrate and the capacitance obtained by the capacitor.

[0012]

[Function] Since the combination substrate formed by forming the capacitor electrode on the dielectric plate and the capacitor formed separately from the combination substrate are combined, the capacitance coupling portion having excellent temperature characteristics and a desired capacitance value can be formed. Can be easily obtained.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a dielectric filter according to an embodiment of the present invention will be described with reference to the perspective view shown in FIG.

In FIG. 1, reference numeral 20 denotes a dielectric filter that functions as a three-stage bandpass filter to which the structure of this embodiment is applied, and the portions corresponding to those of the conventional example of FIG. In this filter 20, three dielectric coaxial resonators 2 are arranged in parallel, and a coupling substrate 3 is arranged in front of the resonator 2 on the open end face 2b side. In each of the dielectric coaxial resonators 2, a resonator hole 4 is formed in the axis of a prismatic dielectric block 2a, and an inner conductive film 2c is formed in the through hole.
And the outer conductive film 2d is formed on the outer surface of the dielectric block 2a except the open end surface 2b.

A cylindrical coupling terminal 5 connected to the inner conductive film 2c is press-fitted into the resonator hole 4 of each dielectric block 2a, and the tip of the coupling terminal 5 projects outward. ing.

The bonded substrate 3 is in the form of a strip made of a dielectric ceramic material having good temperature characteristics, and has a surface 3a.
Is formed with comb-shaped capacitor electrodes 7, 8 and 9 extending in the longitudinal direction thereof. The tip of the coupling terminal 5 of the coaxial resonator 2 is formed on each of the capacitor electrodes 7, 8 and 9. Soldered and connected.

One electrode of the chip capacitor 11 is soldered to the electrode 7 of the coupling substrate 3, the other electrode of the chip capacitor 11 is soldered to the electrode 8, and one electrode of the chip capacitor 12 is connected to the electrode 8. The electrode is soldered and connected, and the other electrode of the chip capacitor 12 is soldered and connected to the electrode 9.

On the back surface 3b of the combined substrate 3, capacitor electrodes 6 and 10 that face the capacitor electrodes 7 and 9 with the combined substrate 3 in between are formed by patterning. If necessary, the electrodes 6 to 10 are formed. It has a structure of trimming. With the above structure, the degree of freedom in capacitance design is increased.

The capacitor electrodes 6 and 10 have a structure in which one end of each of the input and output terminals 13 and 14 is connected by soldering, and the other ends of the output terminals 13 and 14 are shown to project. It is configured to be stored in a metal case that does not. With such a structure, a bandpass filter having a three-stage structure is formed.

An equivalent circuit of this structure is shown in FIG. Here, the capacitance C1 is obtained by the electrodes 6 and 7 and the portion of the combined substrate 3 sandwiched therebetween. The electrostatic capacitance C2 is obtained by the chip capacitor 11 and the electrostatic capacitance C2 ′ obtained by the electrodes 7, 8 and the portion of the combined substrate 3 sandwiched therebetween.
Get at. The electrostatic capacitance C3 is obtained by the electrostatic capacitance C6 obtained by the chip capacitor 12 and the electrostatic capacitance C3 'obtained by the electrodes 8 and 9 and the portion of the combined substrate 3 sandwiched therebetween. The capacitance C4 is obtained by the electrodes 9, 10 and the part of the bonded substrate 3 sandwiched therebetween.

Then, by trimming these electrodes 6 to 10 as necessary, the capacitance can be adjusted, and finally the variation in the chip capacitor can be absorbed to obtain the desired capacitance. Therefore, even if there is a large variation in the chip capacitor, the chip capacitor can be used, and the degree of freedom in designing the capacitance and thus the filter is increased.

The electrodes may be trimmed by measuring the capacitance of the chip capacitor before mounting it and mounting it accordingly.

[0023]

According to the present invention, a coupling substrate formed by forming a capacitor electrode whose dimensions can be finely adjusted by trimming on a dielectric plate having good temperature characteristics, and a capacitor formed separately from this coupling substrate. By combining the above, respective advantages can be effectively utilized, and therefore, a dielectric filter having excellent temperature characteristics and having a capacitance coupling portion having a desired capacitance value can be easily obtained.

[Brief description of drawings]

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

FIG. 2 is an electrode structure diagram of a surface of a coupling substrate used in a dielectric filter according to an embodiment of the present invention.

FIG. 3 is an electrode structure diagram of a back surface of a combined substrate used in a dielectric filter according to an embodiment of the present invention.

FIG. 4 is an equivalent circuit diagram of a dielectric filter according to an embodiment of the present invention.

FIG. 5 is a perspective view of a conventional dielectric filter.

FIG. 6 is an equivalent circuit diagram of a conventional dielectric filter.

[Explanation of symbols]

 20 Dielectric Filter 2 Dielectric Coaxial Resonator 3 Coupling Substrate 5 Coupling Terminals 6 to 10 Capacitor Electrode 11 and 12 Chip Capacitor

Claims (1)

[Claims] 1. A dielectric filter having a capacitance coupling portion, comprising: a coupling substrate formed by forming a capacitor electrode on a dielectric plate; and a capacitor formed separately from the coupling substrate, and a required capacitance. Is obtained by the electrostatic capacitance obtained by the coupling substrate and the electrostatic capacitance obtained by the capacitor.