JP2002050906A - Dielectric filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dielectric filter which is able to form an attenuation pole and easy to be configured. SOLUTION: The dielectric filter comprises four stages of resonators, where a first stage resonator is capacitively coupled to a third stage resonator, and a second stage resonator is capacitively coupled to a fourth stage resonator. The dielectric filter uses three dielectric substrates 10, 20, 30. A conductor pattern 33 is formed at a position facing a conductor of each of the resonators, to produce a capacitance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric filter, and more particularly to a circuit configuration and a structure for improving a pass band characteristic thereof.

[0002]

2. Description of the Related Art Various types of dielectric filters have been used for processing high-frequency signals of mobile communication devices and the like.
In mobile communication equipment terminals and the like, those in which coaxial TEM resonators are connected in multiple stages are often used, and those in which a plurality of resonators are integrated have been put to practical use.

In a dielectric filter in which a plurality of resonators are integrally formed in a dielectric block, there is capacitive coupling and inductive coupling between adjacent resonators, and the coupling state is adjusted. Thus, the bandpass characteristics can be adjusted.

[0004]

Attempts have been made to improve the bandpass characteristics by forming an attenuation pole above or below the passband of the dielectric filter. Generally, when an attenuation pole is formed, a reactance element must be connected to the outside, and it has been difficult to obtain an attenuation pole with a simple structure. The present invention provides a dielectric filter that can obtain an attenuation pole below a pass band with a simple structure.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problem by adding a capacitance between specific resonators. The body filter is characterized in that it has an element for capacitively coupling the resonators at both ends and one placed resonator, respectively.

In a specific structure, a dielectric filter in which three dielectric substrates are joined and four resonators are integrally formed is provided with four parallel grooves extending linearly. A flat second dielectric substrate is joined to a plane having a concave groove of the first dielectric substrate to form four through holes, and a flat third dielectric substrate is formed on the second dielectric substrate. Joined to form a dielectric block, an inner conductor is formed on the surface of the through hole,
An outer conductor is formed on a surface parallel to the direction in which the through hole extends, except for the joint surface of each dielectric substrate, and the through hole is opened.
(1) A short-circuit conductor is formed on one end face, and four resonators are integrally formed in the dielectric block.One of the joining surfaces of the second dielectric substrate and the third dielectric substrate has a resonator at both ends. It is characterized in that it has two parallel conductor patterns extending from a position facing the inner conductor to a position facing the inner conductor of one resonator.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A dielectric filter according to the present invention comprises:
As shown in the equivalent circuit of FIG. 2, it is composed of four resonators,
The resonator R ₁ and the third resonator R ₃ input terminal capacitively coupled, the second resonator R ₄ resonator R ₂ and the output terminal are capacitively coupled.

This capacitive coupling utilizes the capacitance obtained by making the conductor pattern formed on the joint surface of the dielectric substrate opposed to the inner conductor of the resonator irrespective of the external element, and uses the size and formation of the conductor pattern. The capacity can be changed depending on the position where the operation is performed.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an exploded perspective view showing an embodiment of the present invention. This shows a state before the first dielectric substrate 10 on which the four parallel concave grooves 11 are formed and the flat dielectric substrates 20 and 30 are bonded. The dielectric substrate is made of a ceramic fired body, and a groove is formed in the first dielectric substrate 10 by cutting.

Conductive patterns 22a and 22b for obtaining an input / output coupling capacitance are formed on the bonding surface of the second dielectric substrate 20 with the first dielectric substrate 10. The conductor pattern 22a extends inward from the end face of the substrate, and the conductor pattern 22b is formed to extend from the portion facing the concave groove toward the end face,
They are opposed by a predetermined length on the substrate. After assembling, they are connected to the terminals and the inner conductor, respectively, to obtain input / output coupling capacitance. The capacitance can be obtained only by the conductor pattern 22a.

On the third dielectric substrate 30, conductor patterns 33a and 33b for connecting the resonators are formed. The conductor pattern 33a extends from the position facing the left groove in the figure to the position facing the second groove from the right, and the conductor pattern 33b faces the right groove from the second groove from the left. Extending to the position.

The three dielectric substrates 10, 20, 30 are adhered by glass or the like, an inner conductor is formed in a through hole formed by the concave groove, and an outer conductor is formed on a surface other than the one end face where the through hole is opened. A conductor and a short-circuit conductor are formed. Conductor pattern 22a
A terminal electrode insulated from the outer conductor is formed in a portion from which is drawn out. The conductor pattern 22b in FIG. 1 is connected to the inner conductors of the resonators at both ends.

The conductor patterns 33a and 33b face the inner conductor of the resonator at the end to form a capacitance. Since there are resonators at both ends, they are connected in series by capacitors. This means that every other four resonators are capacitively coupled.

FIG. 3 is an explanatory view of the characteristics of the dielectric filter according to the present invention. When a conductor pattern is added as described above, an attenuation pole 37 appears below the pass band of the curve 36 showing the attenuation characteristics.

The frequency of the attenuation pole is determined by the conductor patterns 33a and 33b.
Varies by. That is, the coupling state between the resonators changes due to the change in the capacitance obtained thereby. The capacitance value can be adjusted by the width of the conductor pattern, and the capacitance can be increased as the formation position is closer to the open end face.

When the above-mentioned one conductor pattern for capacitive coupling is further extended from the position of the resonator where the one conductor pattern is placed to the resonator at the end, a slight capacitance is added between the conductor pattern and the resonator at the end. As a result, a phenomenon in which the attenuation characteristics outside the pass band are improved has also appeared.

[0018]

According to the present invention, an attenuation pole can be obtained below the pass band, and its frequency can be adjusted. In addition, if a dielectric block in which a dielectric substrate is bonded is used,
Since a coupling capacitance can be formed inside the dielectric block, a small-sized and easily manufactured dielectric filter can be obtained.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing an embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram of a dielectric filter according to the present invention.

FIG. 3 is an explanatory diagram of characteristics of a dielectric filter according to the present invention.

[Explanation of symbols]

10.20,30: conductor pattern 22 :( for output coupling) for between conductor patterns 33 :( resonator coupling) conductor patterns R ₁ to R _4: the resonator

Claims (3)

[Claims] 1. A dielectric filter in which three dielectric substrates are joined and four resonators are integrally formed, the first dielectric having four parallel grooves extending linearly. A flat second dielectric substrate is bonded on a plane having a concave groove of the substrate.
Three through holes are formed, and a flat third dielectric substrate is joined to the second dielectric substrate to form a dielectric block, and an inner conductor is formed on the surface of the through hole. The outer conductor is formed on the surface parallel to the direction in which the through hole extends, except for the joint surface of the above. The two extending from the position facing the inner conductor of the resonator at both ends to the position facing the inner conductor of one placed resonator on one of the bonding surfaces of the second dielectric substrate and the third dielectric substrate. A dielectric filter comprising a conductor pattern. 2. The dielectric filter according to claim 1, wherein at least one of the conductor patterns extends further toward the resonator at the other end. 3. A dielectric filter in which four dielectric coaxial resonators are capacitively coupled, wherein the dielectric filter includes elements for capacitively coupling the resonators at both ends and one placed resonator, respectively. Dielectric filter.