JPH10190305A - Dielectric filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily connect a conductor pattern for an inductor. SOLUTION: This filter obtains an LC parallel resonance circuit by the inductance and inter-line capacity of the conductor pattern for the inductor formed on the front and back surfaces of a dielectric substrate 10. In this case, the end parts of the conductor patterns 11, 12, 13 and 14 circulating on the front and back surfaces of the dielectric substrate 10 of the filter are performed through capacity by the conductor patterns 17 (17a and 17b) and 18 (18a and 18b) formed oppositely on the front and back surfaces of the substrate 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric filter which can be used in a high-frequency band exceeding 100 MHz, and more particularly to a dielectric filter in which a conductor pattern of one or more turns is formed on the front and back surfaces of a dielectric substrate. It is.

[0002]

2. Description of the Related Art Helical resonators (filters) and dielectric resonators (filters) have been used as filters that can be used in the hundreds of MHz band for mobile communication devices and the like, but the size is limited by the resonance frequency. However, there is a limit to miniaturization.
Therefore, it has been considered that a conductor pattern for an inductor and a conductor pattern for a capacitor are formed on the front and back surfaces of a dielectric substrate, and an LC resonance circuit constituted by the conductor pattern is used as a filter or the like.

[0003] Such a filter is disclosed in Japanese Patent Application No. Hei 3-1832.
No. 91 (Japanese Patent Application Laid-Open No. H5-14007) and the like have proposed a filter in which a conductor pattern for an inductor is provided with a line capacitance to form a parallel resonance circuit by inductance and capacitance.

FIG. 3 is a plan view (a) and a bottom view (b) of an example of the filter. Conductor striplines 31 and 32 are formed on the front and back surfaces of a ceramic substrate 30 having a relatively high dielectric constant of about 90. Strip line 31 of this conductor,
Reference numerals 32 are connected by through holes formed in the substrate 30, and constitute one continuous strip line. On the substrate 30,
Strip lines 33, 34 of other conductors are also formed and similarly connected by through holes. Conductor stripline 3
One ends of 1, 33 are connected to conductor patterns facing input / output electrodes 35, 36. Also, conductor strip lines 32, 34
Is pulled out to the end face of the substrate and grounded.

[0005] An LC parallel resonance circuit is formed by the inductance of the conductor pattern continuous on the front and back surfaces and the line capacitance, and a coupling is generated between the respective circuits to form a filter. When the conductor strip lines are arranged line-symmetrically, inductive coupling is increased, and when the strip lines are arranged point-symmetrically, capacitive coupling is increased.

[0006]

In the above-mentioned filter, in order to connect the conductor patterns on the front and back surfaces of the dielectric substrate, a through hole is formed in the dielectric substrate, and the through hole is filled with a conductor. Is required. The man-hours for this occupy a large proportion in the manufacturing, and also cause an increase in cost. The present invention solves such a problem.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems by forming conductor patterns facing each other in place of through holes, and connecting the conductor patterns on the front and back surfaces by the capacitance obtained by the conductor patterns. It is.

That is, a plurality of conductor patterns for inductors, which circulate in the same direction and are connected at one end to each other, are arranged on the front and back surfaces of the dielectric substrate at intervals, and each conductor pattern has a front and back surface except for a bent portion. In a dielectric filter in which one end of the conductor pattern is grounded and the other end of the conductor pattern located at both ends is connected to the input / output end via a capacitor, the conductor pattern for the inductor on the front and back surfaces is provided. Are connected via a capacitor.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Inductance is obtained by a conductor pattern that goes around the front and back surfaces of a dielectric substrate, and the line capacitance due to the overlap of the front and back surfaces is used as a parallel capacitance. The conductor patterns on the front and back surfaces are connected via the capacitance obtained by the conductor patterns facing each other. The circuit shown in FIG. 2 is an equivalent circuit of the dielectric filter according to the present invention.

[0010]

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

FIG. 1 is a plan view (a) and a bottom view (b) showing an embodiment of the present invention. Conductor striplines 11 and 12 are formed on the front and back surfaces of a ceramic substrate 10 having a relatively high dielectric constant of about 90. Stripline 1 of this conductor
1 and 12 are connected to capacitor electrodes formed by conductor patterns 17a and 17b formed on the front and back surfaces of the dielectric substrate, and are capacitively coupled. That is, the conductor pattern for the inductor is connected through the capacitor.

The conductor strip line 11 has approximately 1
It is formed as a conductor pattern that goes around a half turn. The strip line 12 of the conductor on the back surface connected by the capacitor is also formed as a conductor pattern that makes a slight round of two turns, and the end is drawn out to the end face of the substrate. The conductor patterns on the front and back surfaces are formed so as to overlap and face each other. Since they are formed so as to go around in the same direction, they cannot all be overlapped, but they can be overlapped in most parts except for bent parts. As a result, the line capacitance between the conductor patterns can be obtained.

In this example, the conductor strip lines 11,
Conductor striplines 13 and 14 were formed on the front and back surfaces of the dielectric substrate 10 in a pattern symmetrical to 12. As before,
Conductor patterns 18a, 18 formed on the front and back surfaces of dielectric substrate 10
b capacitively coupled.

The ends of the strip conductors 11 and 13 on the front side that are not connected to the conductor patterns 17a and 18a are connected to conductor patterns formed near the end face of the substrate. These conductor patterns are the conductor patterns 15, 16 formed on the back side.
Are formed so as to face each other, whereby a capacitance is formed to obtain an input / output coupling capacitance of the dielectric filter.

By forming such a conductor pattern, a dielectric filter having the equivalent circuit shown in FIG. 2 is formed. If the conductor strip line is formed so as to be symmetrical with respect to the direction in which the conductor circulates, the inductive coupling between the two resonators becomes strong, and the pass band characteristic becomes steep on the high frequency side. If the circling strip lines are formed point-symmetrically so as to be the same, capacitive coupling between the resonators will be strong, and the passband characteristics will be steep on the low frequency side.

The dielectric substrate on which the conductor pattern as shown in FIG. 1 is formed is sandwiched between two dielectric substrates from both sides, and a conductor film connected to the ground potential is formed on the surface of the resulting laminate. It is formed. One ends of the strip lines 12 and 14 of the conductor shown in FIG. 1 are also connected to the conductor film connected to the ground potential. Note that the conductor patterns 15, 16 in FIG.
Are connected to input / output terminal electrodes.

In order to obtain an arbitrary pass band characteristic,
It is also possible to arrange three or more orbiting conductor patterns for the inductor on the dielectric substrate or adjust the coupling state.
As a result, a dielectric filter having a pass band characteristic up to about 400 MHz could be obtained.

[0018]

According to the present invention, it is not necessary to form through holes in the dielectric substrate, so that the number of steps can be reduced and the strength of the dielectric substrate can be prevented from being impaired.

In addition, the step of filling the through hole with a conductor is not required, and problems such as reliability of the conductor for connection can be solved.

[Brief description of the drawings]

FIG. 1A is a plan view showing an embodiment of the present invention.
(B) is a bottom view

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

3 (a) is a plan view and FIG. 3 (b) is a bottom view showing an example of a conventional dielectric filter.

[Explanation of symbols]

 10, 30: Dielectric substrate 11, 12, 13, 14: Conductor strip line 15, 16: I / O electrode 17, 18: Conductor pattern

Claims (3)

[Claims] 1. A plurality of conductor patterns for inductors, which circulate in the same direction and are connected at one end to each other on the front and back surfaces of a dielectric substrate, are disposed at intervals, and each of the conductor patterns is formed on the front and back surfaces except for bent portions. And one end of the conductor pattern is grounded,
What is claimed is: 1. A dielectric filter in which the other ends of conductor patterns located at both ends are connected to input / output ends via capacitors, wherein the conductor patterns for inductors on the front and rear surfaces are connected via capacitors. 2. A plurality of inductor conductor patterns circling in the same direction and having one end connected to each other on the front and back surfaces of the dielectric substrate at intervals, and each of the conductor patterns is excluding a bent portion. And one end of the conductor pattern is grounded,
In a dielectric filter in which the other end of the conductor pattern located at both ends is connected to the input / output end via a capacitor, the inductor conductor patterns on the front and back surfaces are connected via a capacitor, and the inductance of each inductor conductor pattern is A dielectric filter comprising an LC parallel resonance circuit formed by the line capacitance of these conductor patterns. 3. A plurality of inductor conductor patterns, which circulate in the same direction and are connected at one end to each other on the front and back surfaces of a dielectric substrate, are arranged at intervals, and each of the conductor patterns is cut on the front and back surfaces except for bent portions. And one end of the conductor pattern is grounded,
In a dielectric filter in which the other end of the conductor pattern located at both ends is connected to the input / output end via a capacitor, the end opposite to the end connected to the ground or the input / output end of the inductor conductor pattern on the front and back surfaces The part is connected to the conductor pattern which opposes on the front and back, The dielectric filter characterized by the above-mentioned.