JPH0430602A - High frequency filter - Google Patents

Abstract

PURPOSE:To arrange a capacitance part in three dimensions and to make the entire filter small by employing a dielectric coupling block having plural grooves in parallel and with a conductor film formed thereto for dielectric bodies for a capacitor coupling each dielectric resonator directly. CONSTITUTION:A coupling block 10 comprises a dielectric block 11 made of a sintered body using a microwave high dielectric constant material. The dielectric block 11 is formed to be rectangular parallelopiped as a whole, and three grooves 12 are provided in parallel (in vertical direction in this case) whose cross section is U-shaped to one face (face of this side) of a set of opposite faces and the dielectric block 11 looks like a comb as a plane view. Then a conductor film 14 is provided to the inner face of each groove 12, that is, both wall faces and a bottom face, an input output electrode 16 is formed to both end faces of the dielectric block 11 to form the coupling block 10. Three lambda/4 dielectric coaxial resonators 20 are juxtaposed to a position corresponding to each groove 12 in the vicinity of the coupling block 10.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a filter used in a high frequency band such as a microwave band. More specifically, the present invention relates to a high frequency filter in which a plurality of λ/4 type dielectric coaxial resonators are coupled by a coupling block having a groove-shaped dielectric coupler structure.

This filter can be used, for example, in the microwave band.
This is useful for A communications, etc.

1. Prior Art] A band-pass filter in which a plurality of λ/4 type dielectric resonators each having a resonator hole of a diameter of 10 mm are arranged in parallel and a capacitor is directly coupled between them is conventionally known. Capacitors used for coupling generally have predetermined conductor patterns printed and wired on a flat substrate, and are configured to have a planar capacitance between adjacent conductor patterns.

[Problems to be Solved by the Invention] As described above, the capacitance obtained by a conductor pattern on a substrate is related to the dimensions of the pattern, and in order to obtain a large capacitance, the substrate itself must be large.

Furthermore, since the size of the capacitor board is determined by the required capacitance, it becomes difficult to connect the dielectric resonator and the capacitor board especially when the capacitance increases, and to compensate for this, the connection terminal must be made longer.

These problems have been a problem in miniaturizing dielectric filters in the prior art.

SUMMARY OF THE INVENTION An object of the present invention is to provide a high-frequency filter that eliminates the drawbacks of the prior art as described above and can be made smaller overall.

[Means for Solving the Problems] The present invention is basically a high frequency filter in which a plurality of 1/4 wavelength type dielectric coaxial resonators are arranged in parallel and directly coupled by a capacitor. In order to achieve the above object, the present invention uses a coupling block as a capacitor that directly couples each dielectric resonator. This coupling block has a structure in which multiple grooves are formed in parallel in a rectangular parallelepiped dielectric block, conductive films are provided on the walls and bottom of the grooves, and input and output electrodes are provided on both end surfaces of the dielectric block. be. A plurality of quarter-wavelength dielectric coaxial resonators are arranged in parallel near the coupling block, and each resonator hole and the conductive film of the groove are directly electrically connected.

Here, a plurality of grooves may be provided in parallel on one of the opposing surfaces of the dielectric block to form a comb shape, or grooves may be provided alternately in parallel on the opposing surfaces of the dielectric block.

The dielectric resonator may be prismatic or cylindrical.

[Operation] Interstage coupling capacitance is generated between the wall conductor films of adjacent grooves of the coupling block. In addition, an input/output coupling capacitance is generated between the input/output electrode on the end face of the coupling block and the wall conductor film of the groove at the end. Each λ/
The type 4 dielectric resonator is directly coupled through an input/output coupling capacitance and an interstage coupling capacitance, and exhibits bandpass filter characteristics.

By using a material with a high dielectric constant for the coupling block, similar to the dielectric resonator, a large capacitor capacity can be provided. These capacitances can be freely adjusted by changing the shape of the grooves, that is, the length, depth, groove spacing, etc. of the grooves.

[Embodiment] FIG. 1 is an exploded perspective view showing an embodiment of a high frequency filter according to the present invention, and FIG. 2 is an assembled perspective view thereof.

The coupling block 10 consists of a dielectric block 11 made of a sintered body of a high dielectric constant material for microwave use. The dielectric block 11 has a rectangular parallelepiped shape as a whole, and one of the opposite faces of the pair (the front face in FIGS. 1 and 2)
Three grooves 12 each having a U-shaped cross section are provided in parallel (in the vertical direction in this case), and when viewed from above, it has a comb shape. Then, a conductor film 14 is provided on the inner surface of the valley groove 12, that is, both wall surfaces and the bottom surface, and input/output electrodes 16 are formed on both end surfaces of the dielectric block 11, thereby forming a coupling block IO.

In the vicinity of the coupling block 10, three λ/4 type dielectric coaxial resonators 20 are arranged in parallel at positions corresponding to the grooves 12.

The resonator 20 has a resonator 22 provided at the center of a rectangular prism-shaped sintered body of a microwave high-permittivity material, and one of the surfaces where the resonator hole 22 is open (the upper surface in FIG. 1) is open. conductor film 24 on the other outer surface and the inner surface of the resonator hole 22.
was formed. A cylindrical metal terminal 26 is inserted into the resonator hole 22 from its open end side, and the protruding pieces 28 at the upper end thereof are connected to the conductive film 14 on each groove 12 by soldering.

In order to make the drawings easier to understand in Figures 1 and 2, the parts where there is no conductor film or electrode and the dielectric base is exposed are shown as small dots, and the shaded parts are where the conductor film is exposed. and electrodes. Dielectric blocks and the like are manufactured by a method such as press-molding powder into a predetermined shape and firing it. Further, the conductive film and electrodes may be formed by, for example, baking a silver paste.

FIG. 3 shows an equivalent circuit of the high frequency filter according to the present invention. In the coupling block 10, human output coupling capacitances C, , C, are formed between the input/output electrode 16 and the wall conductor film of the groove near the end, Interstage coupling capacitance Cz between wall conductor films of adjacent grooves,
C3 is formed. The input/output coupling capacitance C+, C4 and the interstage coupling capacitance Ct, Cs are the area of the input/output electrode 16,
It can be adjusted by adjusting the width of the protrusion between the grooves, the groove depth, etc. L.

The parallel circuit of . . . , L3 and Cs, . . . 2 C1 equivalently represents a coaxial resonator.

As a result, the plurality of λ/4 type dielectric resonators 20 are coupled through input/output and inter-stage coupling capacitance, and a high frequency filter exhibiting bandpass filter characteristics is obtained.

Other examples of combined blocks are shown in FIGS. 4 and 5.
In the example shown in the figure, the grooves 30 are provided on opposite surfaces of the dielectric block 32. Further, in the example shown in FIG. 5, the groove 40 has a rectangular cross section, and is provided wide on one side of the dielectric block 42. In the example shown in FIG. In addition, the cross-sectional shape of the groove may be semicircular or trapezoidal. In any case, the required capacity can be obtained by changing the groove length, depth, groove spacing, etc. Groove 30
．． A conductive film is formed over the entirety of 40. Since the conductive film at the bottom of the trench is for connecting the conductive films on the wall surfaces of the trench, it does not need to be provided over the entire surface.

The conductor film 26 of the resonator hole 22 of the λ/4 type resonator 20 and the conductor film 14 of the groove can be connected to each other by using the above-mentioned cylindrical metal terminal, a strip-shaped (tongue-shaped) metal terminal, a lead wire, etc. may also be used. The dielectric resonator may be cylindrical.

In the above embodiment, three sets of grooves and resonators are provided, but the number of sets (number of filter stages) may be arbitrary.

[Effects of the Invention] As described above, the present invention uses a dielectric coupling block in which a plurality of grooves are formed in parallel and a conductive film is formed as a capacitor that directly couples each dielectric resonator. The entire filter can be made smaller than conventional substrate types.

Furthermore, since the capacitor part can be made smaller, the degree of freedom in connecting the dielectric resonator and the coupling block increases, making assembly easier.

Since the filter of the present invention has an integrated capacitive part,
Accurate groove shapes can suppress variations in capacitance, eliminate the need for high-precision screen printing technology to form conductive films, reduce manufacturing costs, and increase reliability.

[Brief explanation of the drawing]

Part 1 is an exploded perspective view showing one embodiment of the high frequency filter according to the present invention, Fig. 2 is a perspective view after assembly, Fig. 3 is its equivalent circuit diagram, and Fig. 4 is a coupling block used in the present invention. FIG. 5 is a plan view showing still another example of the combined block. 10... Coupling block, 11... Dielectric block,
12... Groove, 14... Conductor film, 16... Input/output electrode, 20... Dielectric resonator, 22... Resonator hole, 2
4... Conductor film, 26... Metal terminal. Patent applicant Fuji Electrochemical Co., Ltd.

Claims (3)

[Claims] 1. A plurality of parallel grooves are formed in a dielectric block, a conductive film is provided on the wall and bottom of each groove, and input/output electrodes are provided on both end faces of the dielectric block to form a coupling block, and near the coupling block, A high frequency filter in which a plurality of 1/4 wavelength type dielectric coaxial resonators each having a single resonator hole are arranged in parallel, and each resonator hole and the conductive film of the groove are electrically connected. 2. 2. The filter according to claim 1, wherein a plurality of grooves are provided in parallel on one of the opposing surfaces of the dielectric block to form a comb shape. 3. 2. The filter according to claim 1, wherein grooves are alternately provided in parallel on opposing surfaces of the dielectric block.