JPH04278702A - Dielectric filter - Google Patents

Abstract

PURPOSE:To miniaturize a product by reducing the pitch between resonators, to automatize the production by simplifying the structure for the purpose of forming plural resonators from one dielectric block, and forming an LC resonance circuit between resonators by an inductance L, which is equivalently generated between resonators by the existence of plural resonators in one electromagnetic field, and a coupling capacitor C between resonators formed on a dielectric substrate to improve the branching characteristic. CONSTITUTION:Plural through holes 45 are formed in a dielectric block 42, and inner electrodes 46 are provided on their inner peripheral surfaces, and meanwhile, an outer electrode 48 is provided on the outer peripheral surface of the dielectric block, 42 and these inner electrodes 46 and outer electrode 48 constitute plural resonators 44, and coupling among these resonators is adjusted by a conductor pattern 58 provided on a dielectric substrate 50 independent of the dielectric block.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric filter in which a resonator is constructed from a dielectric block, and more particularly to a dielectric filter used in a microwave band.

0002

BACKGROUND ART In recent years, filters using various dielectric ceramics have been used in communication devices using microwaves, such as mobile phones and car phones, in order to reduce loss. A typical dielectric filter is constructed by coupling together a plurality of coaxial resonators each having an internal electrode and an external electrode provided on the inner and outer peripheral surfaces of a cylindrical dielectric block. By inserting a predetermined coupling capacitance between each resonator and a predetermined coupling capacitance (input/output coupling capacitance) between the resonator at both ends and the external circuit, the coupling capacitance can be adjusted. , effective demultiplexing characteristics are obtained.

For example, Japanese Patent Laid-Open No. 1-231402 discloses that one dielectric block 12 as shown in FIG.
A filter 1 in which a plurality of resonators 14 are formed from
0 is revealed. That is, the dielectric block 12 has three through holes 15 formed in parallel, and an internal electrode 16 provided on the inner peripheral surface of each through hole 15 and an internal electrode 16 provided on the outer peripheral surface of the dielectric block 12. Three resonators 14 are constituted by the external electrodes 18 (shaded portions).

[0004] In such a filter 10,
A coupling hole 20 for adjusting the amount of coupling between the resonators is formed in a portion of the dielectric block 12 corresponding to between the resonators, and by changing the size, shape, etc. of the coupling hole 20, adjacent resonators 14 , 14 can be adjusted. Further, in the through hole 15 of the resonator 14 located at both ends, an input pin 22 or an output pin 24 is provided.
is fixed via a dielectric ring 26, and a stray capacitance is formed between the internal electrode 16 and the input pin 22 or the output pin 24 by the dielectric ring 26, and this input/output coupling capacitance is It is designed to be able to be electrically connected to an external circuit through the connector.

In addition, in this filter 10, by providing a coupling hole 20 between adjacent resonators 14, 14, coupling is realized by changing the effective permittivity during even mode excitation and odd mode excitation. There is.

However, such a filter 10
Since it is necessary to provide coupling holes 20, there is a physical restriction in reducing the pitch between the resonators 14, which makes it difficult to downsize in the L direction in the figure. In addition, when forming the internal electrodes 16 and external electrodes 18 on the dielectric block 12 having such a three-dimensional structure, the dielectric block 12 is immersed in a conductive paste with low viscosity.
It is common to burn the filter, but such a filter 10
Now, in the integrated dielectric block 12, the through hole 15
While it is necessary to provide a conductor on the inner peripheral surface of the dielectric block 12 and the outer peripheral surface of the dielectric block 12, a conductor is not required on the inner peripheral surface of the coupling hole 20. Therefore, before dipping the dielectric block 12 in the conductive paste, This creates the problem that the bonding hole 20 needs to be masked, which complicates the manufacturing process.

On the other hand, Japanese Patent Application Laid-Open No. 63-250901
The publication discloses a dielectric filter 28 having a structure as shown in FIG. It is designed to be formed by That is, each dielectric block 12 has one through hole 15 formed in its axial center, and an internal electrode 16 is provided on its inner peripheral surface.
An external electrode 18 (shaded area) is provided on the outer peripheral surface of the external electrode 18 (shaded area). Therefore, adjacent dielectric blocks 12, 12
A conductor (external electrode 18) is interposed between the
This is to prevent the resonators 14 from electrically interfering with each other.

In such a filter 28, the coupling capacitance between each resonator 14 and the input/output coupling capacitance are determined by a conductive pattern formed on a dielectric substrate 30 separate from the dielectric block 12. It is being adjusted. That is, a conductor pattern 32 corresponding to each resonator 14 is provided on one surface of the dielectric substrate 30, and each conductor pattern 32 is connected to the internal electrode of the corresponding resonator 14 by a metal pin 36. 16, and here, the adjacent conductor patterns 32
, 32 forms a coupling capacitance between the resonators 14, 14.

Although not shown in the drawings, in this filter 28, a conductor pattern coupled to the input pin 22 and a conductor pattern coupled to the output pin 24 are provided on the other surface of the dielectric substrate 30, respectively. The input/output coupling capacitance is formed by the thickness (capacitance) of the dielectric substrate 30 interposed between these conductive patterns and the conductive pattern 32 connected to the resonator 14. -ing

[0010] Such a filter 28 has the inherent problem of complicating the manufacturing process, and also requires holding each resonator 14 one by one during manufacturing. It is necessary to add some ingenuity to the structure, and
Its automation was also disadvantageous.

[0011] Furthermore, in any of the dielectric filters of the above-mentioned structure, the frequency characteristics of the filter exhibit a relatively small amount of attenuation before and after the passband, so radio waves in that frequency range are also passed through, resulting in poor filter performance. There was a problem that the

0012

[Problem to be solved] Under such circumstances, the present invention has been made, and the problem to be solved is to miniaturize the dielectric filter, simplify the structure, and make manufacturing automation advantageous. Another object of the present invention is to improve the attenuation characteristics of a dielectric filter and improve the demultiplexing characteristics.

[0013]

[Solution] In order to solve the above problems, in the present invention, a plurality of through holes are formed in a dielectric block, internal electrodes are provided on the inner peripheral surface of the through holes, and an inner electrode is provided on the outer peripheral surface of the dielectric block. An external electrode is provided on the surface, and the internal electrode and external electrode constitute a plurality of resonators, and the coupling between the plurality of resonators is provided on a dielectric substrate separate from the dielectric block. The gist of the present invention is a dielectric filter characterized by being configured to be adjusted using a conductor pattern.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to clarify the present invention more specifically, one embodiment of the present invention will be described below in detail with reference to the drawings.

First, FIG. 1 shows a dielectric filter 40 having a structure according to the present invention. There, 42
is a rectangular parallelepiped-shaped dielectric block, and in this dielectric block 42, three resonators 44 are arranged in the longitudinal direction (
They are formed so as to be lined up in the L direction (in the figure). That is, three through holes 45 are formed in parallel in the dielectric block 42, and an internal electrode 46 is formed of a conductor provided on the inner peripheral surface of the through hole 45. External electrodes 48 are formed by conductors provided on the outer peripheral surface and bottom surface of the block 42.

Note that the dielectric block 42 can be formed from various known dielectric materials such as barium oxide-titanium oxide-neodymium oxide, and the internal electrode 46 and the external electrode 48
is formed using a metal conductor such as silver. Normally, the electrodes 46 and 48 are formed by producing the dielectric block 42 and forming the through holes 45, then dipping the dielectric block 42 into a conductor paste such as silver, and then baking it. . Then, by polishing one end surface (upper surface) of the dielectric block 42, unnecessary electrodes are removed, and the block height (H) is adjusted to match the resonance frequency to the designed value.

By the way, in this embodiment, in order to insert coupling capacitance between the three resonators 44, the dielectric block 4
A dielectric substrate 50 in the form of a rectangular plate, which is separate from 2, is provided. One end of the dielectric substrate 50 and the dielectric block 42 is inserted into the through hole 45 of the dielectric block 42 and fixed to the internal electrode 46, while the other end is inserted through the dielectric substrate 50. They are integrally attached by metal pins 52 that serve as leads and are fixed in this state.

Then, on one surface of the dielectric substrate 50 (here, the surface on which the dielectric block 42 is not located), each resonator 44 is attached to each of the metal pins 52.
By connecting and providing the conductor pattern 58 corresponding to the above, the internal electrode 46 of the dielectric block 42 and the conductor pattern 58 on the dielectric substrate 50 are electrically connected by the metal pins 52. be. Thus, there is a gap 6 of a predetermined width between the adjacent conductor patterns 58, 58.
0, the capacitance forms a coupling capacitance between the adjacent resonators 44, 44.

Further, an input pin 54 or an output pin 56 is fixed to one end of the dielectric substrate 50 in the length direction (L direction in the figure) in a penetrating state, and is connected to an external circuit. It is now connected. Although not shown, conductor patterns connected to the input pins 54 and output pins 56 are provided on the other surface of the dielectric substrate 50 (the surface on which the dielectric block 42 is located). As a result, an input/output coupling capacitance is formed with a capacitance corresponding to the thickness of the dielectric substrate 50.

In the dielectric filter 40 having such a structure, three resonators 44 are connected to one dielectric block 4.
Since it is formed from two pieces, it has the advantage that the structure is simple and manufacturing can be advantageously automated. In addition, since the coupling capacitance between the resonators 44 is adjusted by the conductor pattern 58 provided on the dielectric substrate 50, the amount of coupling between the resonators 14, 14 as in the conventional filter 10 shown in FIG. There is no need to provide the coupling hole 20 in the dielectric block 12 for adjusting the L of the dielectric filter 40.
Since the length can be shortened, miniaturization can be advantageously achieved.

Furthermore, in the dielectric filter 40, since the dielectric block 42 is not partitioned by a conductor, each resonator 44 is located within the spread of one electromagnetic field and electrically influences each other. It has become. Therefore, if an inductance L exists between the resonators 44, 44, similar characteristics will be observed, and when expressed as an equivalent circuit, it will become as shown in FIG. 2. In other words, each resonator 4
A parallel resonant circuit 62 made of LC is constructed between 4 and 44.

As a result, series resonance occurs between the resonant circuit 62 and each resonator 44, and thus the frequency characteristics of the dielectric filter 40 can be effectively improved. That is, FIG. 3 shows the frequency characteristics measured for the dielectric filter 40 having the structure according to the present invention, in which the frequency characteristics are steep on the lower frequency side than the passband (approximately 920 MHz), as indicated by the □ mark. It has been revealed that a significant attenuation peak appears (approximately 770 MHz), and that the attenuation characteristics of the dielectric filter 40 are effectively improved on the low frequency side, thereby improving the demultiplexing characteristics. In addition, in FIG. 3, for comparison, the frequency characteristics measured for the filter 10 (28) of the conventional structure are also indicated by an x mark, but the characteristics of the dielectric filter 40 according to the present invention as described above are also shown. is not recognized in any way.

Although one embodiment of the present invention has been described in detail above, it goes without saying that the present invention is not limited in any way by the description of such embodiment. Furthermore, it is understood that in addition to the above embodiments, various changes, modifications, improvements, etc. can be made to the present invention based on the knowledge of those skilled in the art, as long as they do not depart from the spirit of the present invention. It should be.

For example, in the above example, a filter consisting of three resonators was used, but the present invention can also be applied to a filter consisting of two resonators or a filter consisting of four or more resonators. Of course, that's true. Also,
In the above example, the input/output capacitors are formed with a dielectric substrate sandwiched between them, but the conductor patterns connected to the input/output pins are placed on the same surface as the conductor patterns connected to the metal pins. A predetermined coupling capacitance may be formed by the gaps between the conductor patterns. Or, conversely, it is also possible to form the coupling capacitance between the resonators with a dielectric substrate sandwiched therebetween. Furthermore, there is no problem in forming the gaps between the conductor patterns using chip capacitors or the like.

[0025]

[Effects of the Invention] As is clear from the above explanation, the dielectric filter according to the present invention has a simple structure since a plurality of resonators are formed from one dielectric block. Manufacturing can advantageously be automated. Furthermore, since the coupling capacitance between resonators can be adjusted using a conductor pattern provided on a dielectric substrate separate from the dielectric block, it is necessary to form coupling holes in the dielectric block. Therefore, the L length of the dielectric block can be shortened accordingly, and the size can be reduced.

Furthermore, in the dielectric filter according to the present invention, since a plurality of resonators are located within the spread of one electromagnetic field, an inductance L is equivalently generated between the resonators. Coupling capacitance between resonators: Together with C, a parallel resonant circuit of LC is formed between the resonators. Therefore,
In such a dielectric filter, an attenuation peak occurs on the low frequency side of the passband, and the attenuation characteristics of the filter can be effectively improved on the low frequency side, and the demultiplexing characteristics can be improved.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of a dielectric filter having a structure according to the present invention.

FIG. 2 is a circuit diagram equivalently representing the dielectric filter shown in FIG. 1;

FIG. 3 is a graph showing a comparison between the frequency characteristics of a dielectric filter having a structure according to the present invention and the frequency characteristics of a filter having a conventional structure.

FIG. 4 is a perspective view showing the structure of a conventional filter.

FIG. 5 is a perspective view showing a different structure of a conventional filter.

[Explanation of symbols]

40 dielectric filter 42 dielectric block 44 resonator
45 Through hole 46 Internal electrode
48 External electrode 50 Dielectric substrate 52 Metal pin 54 Input pin
56 Output pin 58 Conductor pattern
60 Gap 62 Parallel resonant circuit

Claims (1)

[Claims] Claim 1: A plurality of through holes are formed in a dielectric block, internal electrodes are provided on the inner peripheral surface of the dielectric block, and external electrodes are provided on the outer peripheral surface of the dielectric block, and the internal electrodes and external electrodes are connected to each other. A dielectric comprising a plurality of resonators, and the coupling between the plurality of resonators is adjusted by a conductor pattern provided on a dielectric substrate separate from the dielectric block. body filter.