JPH1168408A - Dielectric filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase attenuation without deteriorating an inserting loss by forming plural conductor films connected to the inner conductors of coaxial resonators on one surface of a dielectric substrate and connecting an inductor between adjacent conductor films among plural conductor films formed on the other surface opposite to it. SOLUTION: The coaxial resonators 1 are installed on a ground conductor formed on a substrate 2. The inner conductors 8 of each coaxial resonator 1 are connected to first conductor films 6a to 6c formed at intervals on the lower surface of a dielectric ceramic substrate 4 respectively through a terminal pin 7. Second conductor films 5a to 5d formed at intervals on the upper surface of the substrate 4 form capacity respectively between the first conductor films 6a to 6c to connect between the respective resonators 1. Then the inductor 13 is connected between the second conductor films 5b and 5c. Thereby an attenuating pole is formed on a high frequency side in the neighborhood of a passing band near e.g. 950 MHz, where the center frequency is e.g. 900 MHz.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric filter mainly used for mobile communication equipment having a center frequency of several hundred MHz to several GHz.

[0002]

2. Description of the Related Art FIG. 6 is an external perspective view showing an example of a conventional dielectric filter. In FIG. 6, the coaxial resonator 1
Are grounded on a ground conductor 3 formed on the substrate 2. As shown in FIG. 7, the dielectric ceramic substrate 4 has first conductor films 6a to 6c formed on the lower surface, and second conductor films 5a to 5d formed on the upper surface. Conductor films 5a to 6a, 6a to 5b, between arrows 15
Capacitors are formed between 5b to 6b, 6b to 5c, 5c to 6c, and 6c to 5d. The size and position of each conductor film depend on the size of the capacitance.

The first conductive films 6a, 6b, 6c are:
It is connected to the inner conductor 8 of the coaxial resonator 1 via the terminal pin 7. Further, the second conductor films 5a and 5d are connected to the connection terminal 9 by the input / output terminal 10 to form a dielectric filter. A metal case 12 is provided on the ground plane of the coaxial resonator 1 and the substrate 2 so as to cover the entire dielectric filter, and is electrically connected to the ground terminal 11. 8 and 9 show an equivalent circuit and a frequency characteristic of this conventional dielectric filter.

[0004]

However, the conventional dielectric filter generally requires a low insertion loss in the pass band and a high attenuation outside the pass band. However, when the attenuation is increased, the insertion loss is reduced. There was a problem of increasing.

Therefore, according to the present invention, an increase in insertion loss can be reduced by forming an attenuation pole in a frequency band in which high attenuation is required. It is to provide a small dielectric filter.

[0006]

SUMMARY OF THE INVENTION The present invention is a dielectric filter having a plurality of coaxial resonators, wherein one surface of a strip-shaped dielectric ceramic substrate is connected to an inner conductor of the coaxial resonator. A plurality of first conductor films are formed at a predetermined interval, and a second conductor film is formed at a predetermined interval on the other surface facing the first conductor film. A plurality is formed, a plurality of coaxial resonators are coupled by a capacitance formed between the first conductor film and the second conductor film, and between the adjacent second conductor films, A dielectric filter comprising the dielectric ceramic substrate to which an inductor is connected.

[0007] The present invention also relates to a dielectric filter having a plurality of coaxial resonators, the first filter being connected to one surface of a strip-shaped dielectric ceramic substrate and the inner conductor of the coaxial resonator. A plurality of one conductive films are formed at a predetermined interval, and a plurality of second conductive films are formed at another predetermined interval on the other surface facing the first conductive film. ,
A plurality of coaxial resonators were coupled by a capacitance formed between the first conductor film and the second conductor film, and a capacitor was connected between the adjacent second conductor films. A dielectric filter comprising the dielectric ceramic substrate.

According to the present invention, the attenuation pole in the vicinity of the pass band of the dielectric filter is, as shown in FIG.
By connecting the attenuation pole forming capacitor 51 so as to straddle the coupling capacitors 42 and 43 for coupling the plurality of resonators 31, 32,..., 3n, an attenuation pole is formed on the low frequency side of the pass band. can do. FIG.
As shown in (b), a plurality of resonators 31, 32,.
..Coupling capacitors 42 and 4 for coupling 3n
By connecting the attenuation pole forming inductor 52 so as to straddle three, an attenuation pole can be formed on the high frequency side of the pass band. Further, when a plurality of capacitors or inductors are connected so as to straddle such a coupling element,
A plurality of corresponding attenuation poles are formed.

[0009]

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

First, a first embodiment of the present invention will be described. FIG. 1 is an external perspective view of a dielectric filter according to a first embodiment of the present invention. In FIG. 1, a coaxial resonator 1 is provided on a ground conductor 3 formed on a substrate 2. On a lower surface of a dielectric ceramic substrate 4, first conductive films 6 a to 6 d and on an upper surface, Second conductor films 5a to 5d
Are formed, and the conductor films 5a to 6a and 6a facing each other are formed.
~ 5b, 5b ~ 6b, 6b ~ 5c, 5c ~ 6c, 6c ~
A capacitor is formed between 5d, and each conductor film is connected to the inner conductor 8 of the coaxial resonator 1 via the terminal pin 7. A chip capacitor (capacitor) 14 is electrically connected to the second conductor films 5b and 5c formed on the upper surface of the dielectric ceramic substrate 4.

FIG. 2 shows the frequency characteristics of the dielectric filter according to the first embodiment. In FIG. 2, the center frequency is 900 MHz, the insertion loss is 2.27 dB, and the attenuation is 46.5 dB as compared with the conventional configuration by forming an attenuation pole near 850 MHz on the low frequency side near the pass band. , 22.
4 dB improvement.

Next, a second embodiment of the present invention will be described. FIG. 3 is an external perspective view of a dielectric filter according to a second embodiment of the present invention. In FIG. 3, a second conductor film 5b formed on the upper surface of the dielectric ceramic substrate 4,
This is the same as described in the first embodiment, except that the inductor 13 is electrically connected to 5c.

FIG. 4 shows the frequency characteristics of the dielectric filter according to the second embodiment. In FIG. 4, an attenuation pole is formed on the high frequency side near the pass band. The center frequency of this dielectric filter is 900 MHz, the insertion loss is 2.27 dB, and 950 on the high frequency side near the pass band is used.
By forming the attenuation pole in the vicinity of MHz, the attenuation was 46.5 dB, and the attenuation could be improved by 22.4 dB with almost no deterioration in insertion loss as compared with the conventional configuration.

Although the above embodiment has been simplified for the sake of explanation, there may be a plurality of coaxial resonators, a plurality of chip capacitors (capacitors), and a plurality of inductors connected thereto. Further, a plurality of capacitors and inductors may be combined.

[0015]

As described above, according to the present invention,
A chip capacitor (capacitor) or a coil (inductor) is formed on a conductor film formed on a dielectric ceramic substrate.
By externally forming the filter, an attenuation pole is formed in the vicinity of the pass band, so that it is possible to provide a dielectric filter capable of increasing the attenuation without deteriorating insertion loss in the pass band.

[Brief description of the drawings]

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

FIG. 2 is a frequency characteristic diagram of the dielectric filter of FIG.

FIG. 3 is an external perspective view of a dielectric filter according to a second embodiment of the present invention.

FIG. 4 is a frequency characteristic diagram of the dielectric filter of FIG.

FIG. 5 is an equivalent circuit of a dielectric filter for forming an attenuation pole according to the present invention.

FIG. 6 is an external perspective view of a conventional dielectric filter.

FIG. 7 is a structural diagram of a dielectric ceramic substrate.

FIG. 8 is a diagram showing an equivalent circuit of a conventional dielectric filter.

FIG. 9 is a diagram illustrating frequency characteristics of a dielectric filter according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Coaxial resonator 2 Substrate 3 Ground conductor 4 Dielectric ceramic substrate 5a, 5b, 5c, 5d (Second) conductor film 6a, 6b, 6c (First) conductor film 7 Terminal pin 8 Inner conductor 9 Connection terminal DESCRIPTION OF SYMBOLS 10 I / O terminal 11 Ground terminal 12 Metal case 13 Inductor 14 Chip capacitor (capacitor) 15 Arrow 31, 32, ..., 3n Resonator 41, 42, ..., 4n Coupling capacitor 51 Attenuation pole forming capacitor 52 Attenuation pole forming inductor C1, C2, C3, C4 Capacitor

Claims (2)

[Claims] 1. A dielectric filter having a plurality of coaxial resonators, wherein a first conductor film for connecting to an inner conductor of the coaxial resonator is provided on one surface of a dielectric ceramic substrate, A plurality of second conductor films are formed at a certain predetermined interval, and a plurality of second conductor films are formed at a certain predetermined interval on the other surface facing the first conductor film. A plurality of coaxial resonators are coupled by a capacitance formed between the film and the second conductor film, and an inductor is connected between the adjacent second conductor films. Dielectric filter. 2. A dielectric filter comprising a plurality of coaxial resonators, wherein a first conductor film for connecting to an inner conductor of the coaxial resonator is provided on one surface of a dielectric ceramic substrate. A plurality of second conductor films are formed at a certain predetermined interval, and a plurality of second conductor films are formed at a certain predetermined interval on the other surface facing the first conductor film. A plurality of coaxial resonators are coupled by a capacitance formed between the film and the second conductive film, and a capacitor is connected between the adjacent second conductive films. Dielectric filter.