JPH0787283B2 - High frequency filter - Google Patents

Description

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 connector structure.

This filter is useful, for example, in mobile radio communication in the microwave band.

[Prior Art] A band-pass filter in which a plurality of λ / 4-type dielectric resonators having a single resonator hole are arranged in parallel and are directly coupled to each other has been conventionally known. What is used for coupling is generally one in which a predetermined conductor pattern is printed and wired on a flat substrate, and is configured to have a planar capacitance between adjacent conductor patterns.

[Problems to be Solved by the Invention] As described above, the capacitance obtained by the conductor pattern on the substrate has a dimensional relationship of the pattern, and the substrate itself becomes large in order to obtain a large capacitance. Also, since the size of the substrate is defined by the required capacitance, it becomes difficult to connect the dielectric resonator and the capacitor substrate when the capacitance becomes large, and in order to compensate for this, the connection terminal must be lengthened.

These have been problems in reducing the size of the dielectric filter in the prior art.

It is an object of the present invention to provide a high-frequency filter that overcomes the above-mentioned drawbacks of the prior art and can be downsized.

[Means for Solving the Problem] The present invention is basically a high-frequency filter in which a plurality of quarter-wave dielectric coaxial resonators are arranged in parallel and directly coupled by a capacitor. To achieve the above object, the present invention uses a coupling block as a capacitor that directly couples each dielectric resonator. In this coupling block, a plurality of grooves are formed in parallel in a rectangular parallelepiped dielectric block, a conductor film is provided on the inner surface of each groove (that is, the wall surface of the groove and the bottom surface of the groove), and the groove arrangement of the dielectric block is arranged. This is a structure in which input and output electrodes on both end surfaces perpendicular to the direction are provided. Then, a plurality of quarter-wave dielectric coaxial resonators are arranged in the vicinity of the coupling block, and the resonator holes and the conductor films of the grooves 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 the grooves may be alternately provided in parallel on the opposing surfaces of the dielectric block.

The dielectric resonator may have a prismatic shape or a cylindrical shape.

[Operation] Inter-stage coupling capacitance is generated between the wall surface conductor films of the 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 surface conductor film on the end portion. Each λ / 4 type dielectric resonator is directly coupled by the input / output coupling capacitance and the inter-stage coupling capacitance, and exhibits a bandpass filter characteristic.

Similar to the dielectric resonator, a material having a large dielectric constant is used for the coupling block, so that a large capacitor capacity can be provided. These capacities can be freely adjusted by changing the groove shape, that is, the groove length, the groove length, the groove interval, and the like.

[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 is composed of a dielectric block 11 made of a sintered body of a high dielectric constant material for microwaves. Dielectric block
Reference numeral 11 denotes a rectangular parallelepiped shape as a whole, and three grooves 12 each having a U-shaped cross section are parallel to one of the pair of opposing surfaces (the surface on the front side in FIGS. 1 and 2) (here It is provided in the up and down direction) and has a comb shape when viewed from above. Then, the conductor film 14 is provided on the inner surface of each groove 12, that is, both the wall surfaces and the bottom surface, and the input / output electrodes 16 are formed on both end surfaces of the dielectric block 11 to form the coupling block 10.

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 respective grooves 12. Resonator 20
Is a square hole having a resonator hole 22 formed at the center of a sintered body of a high dielectric constant material for microwaves, and one of the surfaces where the resonator hole 22 is open (the upper surface in FIG. 1) is an open surface. The conductor film 24 is formed on the other outer surface and the inner surface of the resonator hole 22. Insert a cylindrical metal terminal into the resonator hole 22 from its open end side.
26 and insert the protruding piece 28 at the upper end thereof into the grooves 12
Solder connection to the upper conductor film 14.

In addition, in order to make the drawings easy to understand in FIG. 1 and FIG. 2, the portions where there is no conductor film or electrode and the base material of the dielectric is exposed are indicated by fine dots, and the shaded portions indicate the conductor film. And electrodes are shown. The dielectric block and the like are manufactured by a method such as press-molding powder into a predetermined shape and firing. The conductor film and the electrodes may be formed by baking silver paste, for example.

FIG. 3 shows an equivalent circuit of the bright high frequency filter according to the present invention. In the coupling block 10, input / output coupling capacitances C ₁ and C ₄ are formed between the input / output electrode 16 and the wall surface conductor film of the groove near the end, and the interstage coupling capacitance C ₂ between the wall surface conductor films of the adjacent grooves C ₂ , C ₃ is formed. Input / output coupling capacitance C ₁ , C ₄ and interstage coupling capacitance C ₂ , C ₃
Can be adjusted by the area of the input / output electrode 16, the width of the convex portion between the grooves, the groove depth, and the like. The parallel circuit of L ₁ , ..., L ₃ and C ₅ , ..., C ₇ is equivalent to a coaxial resonator.

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

Another example of the combined block is shown in FIGS. 4 and 5. Fourth
In the example shown in the figure, the grooves 30 are provided on both surfaces of the dielectric block 32 that face each other. Further, in the example of FIG. 5, the groove 40 has a square cross section, and the groove is wide on one surface of the dielectric block 42. 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, and the like. A conductor film is formed on the entire grooves 30 and 40. Since the conductor film at the bottom of the groove is for connecting the groove wall surface conductor films, it is not necessary to provide it on the entire surface.

Conductor film 26 of resonator hole 22 of λ / 4 type resonator 20 and conductor film 14 of groove
In addition to the cylindrical metal terminal, a strip-shaped (tongue-shaped) metal terminal, a lead wire, or the like may be used for the connection with.
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 The present invention uses a dielectric coupling block in which a plurality of grooves are formed in parallel and a conductor film is formed as a capacitor for directly coupling the respective dielectric resonators as described above. The entire filter can be made smaller than the conventional substrate type.

Further, since the capacitance portion can be downsized, the degree of freedom in connecting the dielectric resonator and the coupling block is increased, which facilitates assembly.

Since the filter of the present invention has an integrated capacitive portion,
The accurate groove shape can suppress variations in capacitance, does not require high-precision screen printing technology for forming the conductor film, reduces manufacturing costs, and improves reliability.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing an embodiment of a high frequency filter according to the present invention, FIG. 2 is a perspective view after assembly thereof, FIG. 3 is an equivalent circuit diagram thereof, and FIG. 4 is a coupling block used in the present invention. FIG. 5 is a plan view showing another example of FIG. 5, and 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, 24 ... Conductor film, 26 ... Metal terminal.

Claims (3)

[Claims] 1. A plurality of grooves are formed in parallel in a dielectric block, a conductor film is provided on the inner surface of each groove, and input / output electrodes are provided on both end faces perpendicular to the groove arrangement direction of the dielectric block. As a coupling block, a plurality of 1/4 wavelength dielectric coaxial resonators each having a single resonator hole are juxtaposed in the vicinity of the coupling block, and an electrical connection is made between each resonator hole and the conductor film of the groove. High-frequency filter connected electrically. 2. The filter according to claim 1, wherein a plurality of grooves are provided in parallel on one of the surfaces of the dielectric block which face each other and are formed in a comb shape. 3. The filter according to claim 1, wherein grooves are alternately provided in parallel on one of surfaces of the dielectric block which face each other.