JPH0275203A - Dielectric filter and its coupling adjustment method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the structure of a block-shaped dielectric filter and a method for adjusting the degree of coupling between resonator units.

[Prior art]

Various layers of dielectric filters are used as microwave band filters. Instead of a dielectric filter in which multiple cylindrical coaxial resonators are capacitively coupled, we have developed a block-shaped dielectric filter that uses electromagnetic coupling and capacitive coupling by forming multiple resonator units integrally in a dielectric block. is becoming mainstream.

FIG. 3 is a perspective view of an example of such a dielectric filter. Two through-holes 31 are formed in the dielectric block 30, and a conductor film 32 is formed on the surface of the through-holes 31 to serve as an inner conductor of the resonator unit.

A conductor film 33 is also formed on the side surface of the dielectric block 30 to serve as an outer conductor of the resonator unit. Although not shown in the figure, a conductive film is also formed on the lower surface of the dielectric block 30, and the lower surface serves as a short-circuit end surface. A conductive film is not formed on the upper surface of the dielectric block 30, and the dielectric is exposed as an open end surface.

Two resonator units are configured by the inner conductor 32 in the through hole 31 and the outer conductor 33 on the outer peripheral surface. In order to adjust the coupling between these resonator units and adjust the bandwidth, a coupling hole 34 is formed in the middle from the open end surface to the short-circuited end surface.

[Problem] By changing the size of the coupling hole described above, the coupling coefficient between two resonator units can be changed. However, it is extremely difficult in terms of processing technology to change the size of the holes once the dielectric block has been fired. Therefore, it is necessary to prepare a large number of molds and use them depending on the characteristics.

It is also possible to change the coupling coefficient by inserting a dielectric or metal into the coupling hole, but this increases the number of parts and makes stable support difficult.

The present invention aims to obtain a dielectric filter having an arbitrary bandwidth by easily adjusting the coupling coefficient between resonator units.

[Failure to solve the problem]

In the present invention, a conductive film is formed on the open end surface to adjust the capacitive coupling that is maximum at the open end surface.

That is, in a dielectric filter in which a plurality of resonator units are integrally formed by a dielectric block having a plurality of through holes formed with inner conductors and an outer conductor formed on the outer periphery, there is no open space between the resonator units. It is characterized in that the end face is provided with a conductive film connected to a ground potential.

In other words, in a method for adjusting the degree of coupling of a dielectric filter in which a plurality of resonator units are integrally formed by a dielectric block having a plurality of through holes formed with inner conductors and an outer conductor formed on the outer periphery, The present invention is characterized in that a conductive film connected to the ground potential is formed on the open end surfaces between the resonator units, and the coupling capacitance between the resonator units 71 is adjusted.

[Effect]

In a x-wavelength TEM resonator, the electric field strength is maximum on the open end surface side, and the magnetic field strength is maximum on the short-circuited end surface side. Therefore, the coupling of electric lines of force between the resonator units in the dielectric filter, that is, the capacitive coupling, is strongest on the open end surface side.

The capacitance is adjusted by capturing the lines of electric force that combine on the open end surface side with a conductor film.

〔Example〕

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

FIG. 1 is a perspective view of an embodiment of the invention. Two through holes 11 are formed in the dielectric block 10, and a conductive film 12 is formed on the surface of the through holes 11 to serve as an inner conductor of the resonator unit. A conductor film 13 is also formed on the side surface of the dielectric film 10 to serve as an outer conductor of the resonator unit.

Although not shown in the figure, a conductive film is also formed on the lower surface of the dielectric block 10, and the lower surface is used as a short-circuit end surface. A conductive film is not formed on the two surfaces of the dielectric block 10, and the dielectric material becomes an exposed open end surface.

Two resonator units are constituted by the inner conductor 12 in the through hole 1 and the outer conductor 13 on the outer peripheral surface. In order to adjust the coupling between these resonator units and adjust the bandwidth, a coupling hole 14 is formed in the middle from the open end surface to the short-circuited end surface.

Two conductor films 15 are formed on the open end surface. This conductive film 15 extends from two opposing sides and is connected to the outer conductor 13. In this example, it is formed so as to extend from two sides, but it may be formed only on one side.

Since the conductor film 15 is connected to the outer conductor 13, it will be connected to the ground potential after assembly.

As mentioned above, in a dielectric filter, capacitive coupling is maximum at the open end face. Since the conductor film 15 at ground potential is formed on the open end surface, the lines of electric force are connected to the conductor film 1.
It can be captured in 5. The amount of electric lines of force that can be captured varies greatly depending on the size of the conductor film 15. Thereby, capacitive coupling is reduced and the bandwidth is correspondingly increased.

The dimensions and area of the conductor film can be changed by scraping the pre-formed conductor film or applying a conductor afterwards.
The coupling capacitance can be set arbitrarily, and adjustment to 19% becomes easy.

FIG. 2 is a perspective view showing another embodiment of the present invention, in which a dielectric band block 20, a through hole 21, an inner conductor 22, an outer conductor 2
3. The coupling hole 24 has the same structure as the above example, but a conductive film 25 is formed across the open end surface.

In this case, the coupling capacitance at the open end face will be cut off. Further, from this state, it is also possible to trim the conductor film 25 to adjust the desired bonding state.

Although the explanation has been given for an example of two resonator units, the present invention can be similarly applied to a dielectric filter having three or more resonator units.

〔effect〕

According to the present invention, it is possible to arbitrarily set the state of capacitive coupling, and it is possible to obtain an easily adjustable dielectric filter that can obtain a desired bandwidth.

Further, dielectric band filters having different characteristics such as bandwidth can be manufactured using dielectric band blocks having the same size and shape. Therefore, it becomes possible to realize a low-cost dielectric filter.

Furthermore, fine adjustment of the characteristics is facilitated by trimming the conductor film or the like.

[Brief explanation of the drawing]

1 and 2 are perspective views showing embodiments of the present invention,
FIG. 3 is a perspective view showing a conventional dielectric filter. 10.20...Dielectric block 12.22...
...Inner conductor 12.23...Outer conductor 15.25...Conductor film

Claims (6)

[Claims] (1) In a dielectric filter in which a plurality of resonator units are integrally formed by a dielectric block having a plurality of through holes formed with inner conductors and an outer conductor formed on the outer periphery, there is a gap between the resonator units. A dielectric filter comprising a conductor film connected to a ground potential on an open end surface. (2) The dielectric filter according to claim 1, wherein the conductor film is connected to an outer conductor. (3) The dielectric filter according to claim 1, wherein the conductive film is two conductive films extending from two opposing sides. (4) The dielectric filter according to claim 1, wherein the conductive film traverses between two opposing sides of the open end face and is connected to the outer conductor adjacent to the two opposing sides. (5) A method for adjusting the degree of coupling of a dielectric filter in which a plurality of resonator units are integrally formed by a dielectric block having a plurality of through holes formed with inner conductors and an outer conductor formed on the outer periphery. 1. A method for adjusting the degree of coupling of a dielectric filter, comprising: forming a conductive film connected to a ground potential on open end surfaces between resonator units, and adjusting coupling capacitance between the resonator units. (6) The method for adjusting the coupling degree of a dielectric filter according to claim 5, wherein the coupling capacitance between the resonator units is adjusted by changing the dimensions and area of the conductor film.