JPH0255402A - Dielectric filter - Google Patents

Abstract

PURPOSE:To adjust the characteristic through the adjustment of a coupling capacity by providing a 2nd throughhole between plural resonator units each forming an inner conductor in a 1st throughhole formed to a dielectric block and forming an outer conductor on an outer circumferential face except an open end face, forming a conductor film in the 2nd throughhole and coupling the units with a capacitance coupling means. CONSTITUTION:Two throughholes 11 are formed to a dielectric block 10, a conductor film 12 is formed in the surface to form an inner conductor, a conductor film 13 is formed except the open end face to form an outer conductor thereby forming a resonator unit. The 2nd throughhole 15 is formed between resonator units and a conductor film 16 is formed to the surface of the throughhole 15. The conductor film 16 is in continuity with the conductor film 17 and also the conductive film 17 is in continuity with the outer conductor 13 to interrupt the magnetic coupling between two resonator units. Since the dielectric unit 18 couples the resonator units, the units are coupled by the capacitance only.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a dielectric filter that couples resonators by capacitance, and particularly relates to a dielectric filter using an integrated dielectric block. It is.

[Prior art]

Filters using dielectric resonators are now being used in various fields as filters for microwave bands, duplexers, etc.

In the past, filters in which cylindrical dielectric coaxial TEM resonators were coupled by capacitance were common, but recently dielectric filters in which multiple resonator units were formed within a dielectric block have come into use. There is.

FIG. 4 is a perspective view showing such a block-shaped dielectric filter, in which a through hole 41 is formed in a dielectric block 40, and a conductive film is formed in this through hole 41 to serve as an inner conductor. A conductor film 43 is formed on the surface of the dielectric block 40, except for the open end surface of the lower surface, and serves as an outer conductor.

In FIG. 4, two resonators are integrally formed. Note that a coupling hole 45 is formed to adjust the coupling between the resonators.

FIG. 5 is an equivalent circuit diagram of the above dielectric filter.

The two resonators are coupled by electromagnetic coupling M and capacitive coupling C2.

[Problem] The characteristics of the dielectric filter as described above are determined by the coupling state of electromagnetic coupling and capacitive coupling. Binding hole 45
is primarily used to adjust capacitive coupling, and its mechanical dimensions determine the state of capacitive coupling and determine its characteristics. Further, the state of electromagnetic coupling also changes depending on the shape and dimensions of the coupling hole. That is, both electromagnetic coupling and capacitive coupling are determined by the coupling hole. Therefore, many molds are required to accommodate different characteristics with different bonding states.

Furthermore, there are two elements in determining the characteristics, and it has been difficult to measure them individually. Therefore, many man-hours are required to adjust the frequency characteristics.

Furthermore, when combining separate resonators, there are problems with assembly man-hours, strength, etc.

The present invention solves these problems and provides easy-to-adjust
The present invention also aims to provide a dielectric filter that can accommodate various characteristics.

Another object of the present invention is to obtain a dielectric filter that is easy to assemble and has high reliability.

[Means to solve the problem]

The present invention solves the above problem by eliminating the electromagnetic coupling of the block-shaped dielectric filter and coupling the resonator corner and throat only by capacitive coupling.

In other words, the dielectric filter includes a plurality of resonator units in which inner conductors are formed in first through holes formed at intervals in a dielectric block, and outer conductors are formed on the outer peripheral surface except for the open end surface. The present invention is characterized in that a second through hole is provided between the resonator units, and a conductive film is formed within the second through hole.

Further, in order to adjust the coupling coefficient, a capacitive coupling means is added to this.

[Effect]

In the dielectric filter according to the present invention, the coupling between the resonators is made very small, and the resonator uni-nodes function almost independently.

Since electromagnetic coupling can be eliminated, the only element of coupling between resonator units is capacitive coupling. Therefore, the characteristics can be adjusted only by adjusting the coupling capacitance.

〔Example〕

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

FIG. 1 is a front sectional view showing an embodiment of the present invention. Two through holes 1) are formed in the dielectric block 10, and a conductor film 12 is formed on the surface thereof to serve as an inner conductor. A conductor film 13 is formed on the surface of the dielectric block IO except for the open end surface (in this case, the bottom surface) to serve as an external conductor. This means that two resonator units are formed.

A second through hole 15 is formed between the resonator units, and a conductive film 16 is also formed on the surface of this second through hole 15. This conductor film 16 is electrically connected to a conductor film 17 formed on the open end surface. Further, the conductor film 17 is electrically connected to the outer conductor 13.

Coupling of the human output of the resonator unit is obtained by the dielectric unit 8. The dielectric uniform 8 is a metal rod coated with a dielectric, and an input/output capacitance is formed between the metal rod and the inner conductor.

In this example, a dielectric substrate 19 having electrodes 20 formed on its surface is used. The electrode 20 is electrically connected to the conductor film 12 of the inner conductor, and is configured to face the dielectric substrate 19 at the center thereof. This forms a coupling capacitance between the two resonator units.

FIG. 2 shows an equivalent circuit diagram of the above embodiment. Since the conductive film 16 formed in the second through hole 15 blocks the magnetic coupling between the two resonators,
- the coupling between the two resonator units is through a capacitance C;

In addition, in order to cut off magnetic coupling, a conductive pattern 37 is provided around the second through hole 35 on the open end surface as shown in FIG.
It is preferable that the conductor pattern 37 is electrically connected to the conductor film in the through hole 35 and the outer conductor 33. As a result, both ends of the conductor film within the through hole are short-circuited.

In addition, in the example in ``2'', the coupling capacitance between the resonator units was obtained by the conductor pattern provided on the dielectric substrate 19, but it is also possible to obtain the capacitance by the conductor pattern formed on the open end surface of the dielectric block. be.

In manufacturing the dielectric filter according to the present invention,
After forming a through hole for the inner conductor of the resonator unit and a second through hole disposed between them in the dielectric block, the entire dielectric block is immersed in an electrode paste of silver, copper, etc. Can be done. In conventional block-shaped dielectric filters, a conductive film must not be formed in the coupling hole, so a conductive film is formed with the coupling hole closed.
In the present invention, the opening can be manufactured by polishing the open end surface after forming the opening over the entire surface, which is advantageous in terms of the number of man-hours. After polishing, a conductor pattern that short-circuits the conductor film may be formed on the open end surface.

Since the dielectric filter according to the present invention can measure the characteristics of each resonator unit 1-, it becomes easy to adjust the characteristics of each resonator unit. Moreover, the adjustment of the characteristics does not affect the characteristics of other resonator units. Furthermore, since there is no electromagnetic coupling between the resonator units and there is only capacitive coupling, the coupling coefficient can be adjusted only by adjusting the capacitance.

〔effect〕

According to the present invention, it becomes easy to design a dielectric filter and adjust its frequency characteristics. This is because it becomes possible to measure the characteristics of each individual resonator unit, and coupling is limited to capacitance only.

Further, dielectric filters that can accommodate various characteristics can be easily manufactured. This is because dielectric blocks of the same size can be used for filters with different characteristics with different coupling states.

Furthermore, since an integrated dielectric block is used, assembly is easy, and it is advantageous in terms of mechanical strength and stability, and an extremely reliable dielectric filter can be obtained. Moreover, the number of man-hours required for forming the conductive film can be reduced.
It is also advantageous in terms of cost.

[Brief explanation of the drawing]

FIG. 1 is a front sectional view showing an embodiment of the invention, FIG. 2 is an equivalent circuit diagram thereof, and FIG. 3 is a perspective view showing another embodiment of the invention. Fig. 4 is a perspective view showing a conventional dielectric filter, and Fig. 5 is its equivalent circuit diagram 35...37... Conductor film (inner conductor) Conductor film (outer conductor) Through hole conductor film conductor pattern

Claims (5)

[Claims] (1) A plurality of resonator units each having an inner conductor formed in a plurality of first through holes formed at intervals in a dielectric block, and an outer conductor formed on the outer peripheral surface excluding the open end surface. A dielectric filter comprising a second through hole between the resonator units, and a conductive film formed in the second through hole. (2) A conductor film in the second through hole and a conductor film electrically connected to the outer conductor are formed on the open end surface, and both ends of the conductor film in the second through hole are connected to the conductor film and the outer conductor. 2. The dielectric filter according to claim 1, wherein the dielectric filter is short-circuited. (3) A plurality of resonator units each having an inner conductor formed in a plurality of first through holes formed at intervals in a dielectric block, and an outer conductor formed on an outer peripheral surface excluding the open end surface. In the dielectric filter, a second through hole is provided between the resonator units, a conductive film is formed in the second through hole, and a means for capacitive coupling between the resonator units is provided. Features of dielectric filter. (4) The dielectric filter according to claim 3, wherein the capacitive coupling means is a capacitor formed by a conductor pattern formed on a dielectric substrate. (5) The dielectric filter according to claim 3, wherein the capacitive coupling means is a capacitor having a conductive pattern formed on the open end surface.