JP2000341006A - Dielectric filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To actualize the formation of a capacitor without using any conductor pattern and to make the dielectric filter small-sized and easy to manufacture by joining a planar 2nd dielectric substrate having a larger dielectric constant than a 1st dielectric substrate on the surface of the 1st dielectric substrate where parallel recessed grooves which extend linearly are formed. SOLUTION: The dielectric filter formed by adhering dielectric substrates 11 and 12 has a through hole 15. An inner conductor is formed in the through hole 15, an outer conductor 17 is formed on an outer peripheral surface parallel to the extending direction of the through hole 15, and a terminal electrode 18 surrounded by the outer conductor 17 is formed. The dielectric constant of the dielectric substrate 11 having recessed grooves is made smaller and the dielectric constant of the plane dielectric substrate 12 is made larger. For example, the dielectric constant of the dielectric substrate 11 is 20 to 30 and the dielectric constant of the dielectric substrate 12 is about 90. Consequently, more electric lines of force are attracted to the dielectric substrate 12 to increase the capacity between resonators.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a dielectric filter, and more particularly to a structure of a conductor pattern for obtaining a desired characteristic by adding a capacitance between resonators.

[0002]

2. Description of the Related Art Various dielectric filters are used in a high frequency range such as a UHF band to a microwave band. Among them, a dielectric filter having a through-hole, in which an inner conductor is formed, and a TEM resonator having an outer conductor formed on an outer peripheral surface thereof is often used. There are a type that is configured by connecting individual resonators, and a type that is integrated with a dielectric block.

In these dielectric filters, input and output coupling capacitances must be formed between the input and output stages and the inner conductor of the resonator. As a means to obtain this coupling capacity,
There are methods for connecting a capacitor and using a dielectric substrate on which the capacitor is formed. In addition, a metal rod coated with a dielectric may be inserted into the through-hole in which the inner conductor is formed, a metal rod may be inserted into a hole provided in the dielectric near the inner conductor, or the outer conductor may be separated from the outer conductor. Or a method of forming a metal film.

In the field of dielectric filters, there is a demand for miniaturization and thinning, and the size must be reduced because the wavelength becomes shorter as the frequency band increases. Accompanying this, it is also difficult to obtain input / output coupling capacitance. Therefore, Japanese Patent Application Laid-Open No. 6-125204 discloses a dielectric filter in which two dielectric substrates are bonded, a conductive pattern is formed on the bonded surface, and the input / output conductive pattern is directly connected to the impedance matching point. Proposed. Also,
Attempts have also been made to adjust bandpass characteristics by adjusting the coupling between resonators by forming a conductor pattern on the bonded surfaces.

FIG. 3 is a plan view of an example of the dielectric filter before assembly. A second flat plate to be bonded to the grooved surface of the first dielectric substrate 21 having two parallel grooves 24
1 shows a dielectric substrate 22 of FIG. The conductor pattern 26 connected to the input / output terminal is pulled out from the impedance matching point. By bonding this to the dielectric substrate 21 having the concave groove, a dielectric block having two parallel through holes is formed.

FIG. 4 is a perspective view showing a dielectric filter having a conductor film formed after bonding. The through hole 25 is formed in a dielectric block to which a dielectric substrate is bonded. An inner conductor is formed in the through hole 25, and an outer conductor 27 is formed on an outer peripheral surface parallel to a direction in which the through hole 25 extends. A terminal electrode 28 surrounded by the outer conductor is formed and connected to the conductor pattern 26 shown in FIG.

[0007]

In order to adjust the band-pass characteristics of the dielectric filter integrally formed with the resonator as described above, a conductor pattern is formed on the joint surface of the dielectric substrate or the like to form an inductance or capacitance. Is considered to be added. When a capacitance is added by these conductor patterns, an attenuation pole can be formed on the low band side or the high band side of the pass band.

In order to obtain sufficient capacitance, it is necessary to make the dimensions of the conductor pattern sufficiently large. However, it is difficult to form the joint in a narrow range, and the design is greatly restricted. In addition, it is necessary to reliably connect and couple the conductor patterns. An object of the present invention is to provide a small-sized dielectric filter that can be formed without using a conductor pattern and that can be easily manufactured.

[0009]

The present invention solves the above-mentioned problems by changing the dielectric constant of a substrate to be joined.

That is, in a dielectric filter in which a plurality of resonators are integrally formed by joining two dielectric substrates, a first dielectric substrate having a plurality of parallel concave grooves extending linearly. A dielectric block having a plurality of through-holes formed by joining a flat plate of a second dielectric substrate having a higher dielectric constant than the first dielectric substrate is formed on the surface having the concave grooves. An inner conductor is formed on the surface of the first dielectric substrate and the respective surfaces facing the joining surface of the second dielectric substrate, and outer conductors are formed on both end surfaces parallel to the extending direction of the concave groove, It is characterized in that a short-circuit conductor is formed on one of the end faces where the through holes are opened.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Since a dielectric having a low dielectric constant formed by a dielectric substrate having a concave groove is present between resonators, capacitive coupling between the resonators is weakened and relatively inductive. Bond becomes stronger. However, since the dielectric constant of the flat dielectric substrate is high, a capacitance is generated between the inner conductors of the resonator, and the state is the same as that of coupling by a capacitor. This capacitance means that a capacitor is connected between the resonators, and an attenuation pole can be obtained on either side of the pass band.

[0012]

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

FIG. 1 is a perspective view showing a dielectric filter in which a conductive film is formed after assembly, and has the same shape as that shown in FIG. It has a structure in which a through hole 15 is formed in a dielectric block to which the dielectric substrates 11 and 12 are bonded. An inner conductor is formed in the through hole 15, and an outer conductor 17 is formed on an outer peripheral surface parallel to a direction in which the through hole 15 extends. A terminal electrode 18 surrounded by the outer conductor is formed, and a conductor pattern for input / output coupling is connected.

In the present invention, the dielectric constant of the dielectric substrate 11 having the concave groove is low, and the dielectric constant of the flat dielectric substrate 12 is high. For example, the dielectric constant of the dielectric substrate 11 having the concave groove is set to be about 20 to 30, and the dielectric constant of the flat dielectric substrate 12 is set to be as high as about 90. As a result, many lines of electric force are drawn into the dielectric substrate 12, and the capacitance between the resonators increases.

FIG. 2 shows the characteristics of the dielectric filter according to the present invention.
Shown in It was confirmed that an attenuation pole was obtained on the higher side of the pass band. By changing the dielectric constant, the frequency of the attenuation pole can be changed.

The present invention is not limited to the above example, but can be applied to general dielectric filters for joining dielectric substrates. It can be applied not only to the comb line type but also to the inter digital type. .

[0017]

According to the present invention, it is possible to form an attenuation pole by relatively increasing the inductive coupling between dielectric resonators and adding a capacitance. Therefore, an arbitrary bandpass characteristic can be obtained without impairing other characteristics.

Further, since a conductor pattern is not required, a small, inexpensive and easily manufactured dielectric filter can be obtained.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram of characteristics of a dielectric filter according to the present invention.

FIG. 3 is a perspective view of an example of a conventional dielectric filter.

FIG. 4 is a perspective view of a conventional dielectric filter.

[Explanation of symbols]

 11, 12: (first) dielectric substrate 21, 22: (second) dielectric substrate

Claims (1)

[Claims] 1. A dielectric filter in which a plurality of resonators are integrally formed by joining two dielectric substrates to form a first dielectric substrate having a plurality of parallel concave grooves extending linearly. A dielectric block having a plurality of through-holes formed by joining a flat plate of a second dielectric substrate having a higher dielectric constant than the first dielectric substrate is formed on the surface having the concave grooves. An inner conductor is formed on the surface of the first dielectric substrate and the respective surfaces facing the joining surface of the second dielectric substrate, and outer conductors are formed on both end surfaces parallel to the extending direction of the concave groove, A dielectric filter, wherein a short-circuit conductor is formed on one of the open end faces of the through hole.