JPH03254202A - Dielectric resonator and filter using same - Google Patents

Abstract

PURPOSE:To obtain a stable electric/mechanical characteristic with excellent manufactureability and design performance by adhering a conductor film to an outer face of a dielectric block and an inner wall face of a resonance hole, mounting a coupling capacitor 22 to an open end of a resonator hole placed at both ends and connecting the capacitor to an external circuit. CONSTITUTION:Each resonance hole 32 forms a coaxial resonator of 1/4 wavelength. A conductor film is formed to an inner wall face of a throughhole provided between the resonator holes 32 and a coupling block hole 34 is formed by connecting the conductor film of the inner wall face to an outer conductor at both opening ends to shield propagation of an electromagnetic wave between the resonators thereby blocking the electromagnetic coupling. Thus, almost similar state to the arrangement of single resonators in terms of electromagnetic wave regardless of the integrated structure is attained. The dielectric resonator 38 is used and a flat plate capacitor 50 is mounted to the open end of the resonator hole 32 and the capacitors 50 are connected by a coil 52. Thus, the resonator with excellent manufactureability performance and stable electric/mechanical characteristic is realized inexpensively.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a dielectric resonator mainly used in the microwave band and a filter using the same.
The present invention relates to a wavelength-type integrated multistage coaxial resonator and a bandpass filter and a bandstop filter using the same.

[Prior Art] Multistage filters using high dielectric constant ceramic materials have various structures. For example, as shown in FIG.
Here, there is a tank bottom in which three (3) dielectric prismatic resonators 10 are arranged in parallel and coupled by suitable lumped constant elements. The dielectric resonator 1O has a through hole that becomes the resonator hole 14 in the center of a prism 12 made of a high dielectric constant material, and an outer surface other than the inner wall surface of the through hole and the open surface (in this case, the upper surface) of the prism 12. A conductive film is attached to form a center conductor and an outer conductor, respectively.

Capacitors C+, 'Ct, Cm at the open end of the center conductor
Connect the coils L++L* between each capacitor.
Connect with.

The equivalent circuit is shown in Figure B. Each dielectric resonator lO has a resonant frequency determined by its prism height, relative permittivity, capacitor capacity, etc., and the 1/4 wavelength Okacho resonance type band is determined by the tank bottom. A rejection filter is obtained. An example of filter characteristics is shown in FIG.

In the case of a bandpass filter, a dielectric prismatic resonator as described above may be used, but an integrated type as shown in FIG. 17A is common. Dielectric block 1 in the shape of a rectangular parallelepiped
A plurality (here, three) of resonator holes 18 and two coupling holes 20 are alternately provided at a predetermined interval on 6, and the open surface (
A conductive film is attached to the outer surface of the dielectric block 16 except for the upper surface here and to the inner wall surface of the resonator hole 18. Coupling capacitors 22 are mounted on the open ends of the resonator holes located at both ends, and connected to an external circuit via them. This filter is represented by an equivalent circuit shown in FIG. 17B, and exhibits bandpass filter characteristics as shown in FIG. 18. In addition, in FIG. 17B, the reference numeral 24 represents three resonators, C, .
, C, represents the coupling capacitance at the input and output, and L+ and L* represent the state in which the resonators are coupled through the coupling hole in terms of an equivalent circuit.

[Plot M to be solved by the invention] The band-stop filter shown in FIG. 15A has a plurality of single resonators arranged, so the number of parts increases, which increases the number of assembly steps, and it is difficult to locate the positions between the resonators. Requirements will also become stricter for the surface accuracy of the outer conductor.

Furthermore, since the resonators need to be bonded to each other, there are problems in terms of deterioration of mechanical strength and environmental reliability.

On the other hand, the band-pass filter shown in FIG. 17A does not have the above-mentioned problems because it is an integrated type, but since the coupling hole provides proper coupling, its diameter and position may be affected by hole pinch, Characteristics are greatly affected by variations in materials such as relative dielectric constant, making it difficult to stabilize electrical characteristics and design.

The object of the present invention is to solve these problems in the prior art and to provide an inexpensive filter that is easy to manufacture and design and provides stable electrical and mechanical characteristics, and a dielectric resonator used therein.

[l! Means for Solving the Problem] A dielectric resonator according to the present invention includes a dielectric block in which a plurality of through holes, each serving as a resonator hole, are arranged in parallel, and one of the surfaces where the through holes are open is open. As a surface, the inner wall surface of the through hole,
In a multi-stage coaxial resonator in which a conductive film is formed on the outer surface except for the open surface to serve as a center conductor and an outer conductor, another through hole is formed between each resonator hole to serve as a coupling prevention hole, and the inner wall surface is A conductor film is provided, and the conductor film on the inner wall surface and the outer conductor are connected by the conductor film at both open ends.

Further, a dielectric filter according to the present invention uses the above-mentioned dielectric resonator and additionally connects a lumped constant element such as a capacitor or a coil.

[Function] Each resonator hole houses a 174-wavelength coaxial resonator. The through hole provided between the resonator holes has a conductor film formed on its inner wall surface, and the conductor film on the inner wall surface is connected to the outer conductor at both open ends, so it becomes a coupling prevention hole, and there is no interference between the resonators. shields the propagation of electromagnetic waves and prevents electromagnetic coupling. Therefore, although it is an integrated structure, it is electromagnetically almost equivalent to an array of single resonators.

Therefore, when an appropriate lumped constant element is additionally connected to this dielectric resonator, it operates as a band reversing filter or a band pass filter.

[Embodiment] FIG. 1A is a perspective view showing an embodiment of a dielectric resonator according to the present invention, and FIG. 1B is a longitudinal sectional view thereof. This example is a case of three stages.

A dielectric block 30 having a rectangular parallelepiped shape has three through holes arranged in parallel to serve as resonator holes 32, and a conductor film is provided on the inner wall surface of the dielectric block 30 and on the four surfaces and the lower surface of the dielectric block 30. and an outer conductor 31 to constitute a multistage coaxial resonator. The top surface of the dielectric block without the HL conductor film is an open surface, and the bottom surface is a short-circuit surface. Note that the dielectric block 30 is made of a sintered body of a high dielectric constant material (for example, barium titanate, etc.).

Here, the feature of the present invention is that another through hole is formed between each resonator hole 32 to serve as a coupling prevention hole 34, and a conductor l is formed on the inner wall surface of the through hole.
! 135 is provided, and the conductor film 35 on the inner wall surface and the outer conductor 31 are connected at both open ends thereof. Since the lower surface of the dielectric block 30 is entirely covered with a conductive film, the opening at the lower end of the coupling prevention hole 34 is directly connected to the conductive film 35 on the inner wall surface thereof. On the open side, dielectric block 3
A strip-shaped conductor film 36 is formed in the width direction of the dielectric block 30, thereby connecting the conductor film 35 on the inner wall surface of the coupling prevention hole 34 to the outer conductor 31 on the side surface of the dielectric block 30. In this way, a multi-stage resonator 38 is obtained.

Here, the conductive film is a very thin layer of conductive material, such as baked silver paste.

The coupling prevention hole 34 located between the resonator holes 32 has its inner wall surface covered with a conductor film 35 and is electrically connected to the outer conductor 31 at both upper and lower open end surfaces, so that electromagnetic waves between the resonators are prevented. The propagation of the resonator is shielded, and although it is an integral structure, it is electromagnetically equivalent to each resonator being independent.

A filter can be constructed by using this resonator 38 and additionally connecting a suitable lumped constant element. As shown in FIG. 2, a band rejection filter is obtained by connecting capacitors tc+, Cx, Cs to each resonator and connecting coils L+, Lx between the capacitors. Further, as shown in FIG. 3, a bandpass filter can be obtained by connecting coupling capacitors C, . Note that capacitors Ca and C
A coil may be used instead of s0.

Other examples of the dielectric resonator are shown in FIGS. 4 to 9. FIG. 4 shows an example in which a rectangular through hole long in the width direction of the dielectric block 30 is used as the coupling prevention hole 39. In this way, the dielectric cross-sectional area between adjacent resonators becomes smaller, and the propagation of electromagnetic waves can be further inhibited, thereby improving the shielding effect. FIG. 5 shows an example in which most of the open surface of the dielectric block is covered with a conductive film except for the vicinity of the open end of each resonator hole.

This increases Q[ compared to the dielectric resonator shown in FIG. Also, the dielectric block is immersed in silver paste,
If the masking in the vicinity of the open end of the resonator hole is removed later, a conductor film having a desired shape can be easily attached, so that screen printing or the like is not required and manufacturing is facilitated.

When the dielectric block 30 has a recess near the coupling blocking hole 34, the recess reduces the cross-sectional area of the dielectric near the coupling blocking type, making it possible to further reduce electromagnetic coupling between the resonators. In the preferred example shown in FIG. 6, a groove 41 is provided on the short-circuit surface side of the dielectric block 4°. Since the magnetic field coupling between the resonators is strong, it is more effective to provide a recess on the short-circuit surface side as shown in FIG.

In FIG. 7, a groove 43 is formed on the side surface of the dielectric block 42. In FIG. FIG. 8 shows an example in which notches 45 are provided on both sides of the short circuit side of the dielectric block 44, and FIG. 9 shows an example in which notches 47 are provided on the open side of the dielectric block 46. be.

FIG. 1A is a perspective view showing an example of a dielectric filter, and FIG. 1B is a sectional view thereof. This is a specific example of the configuration of the band rejection filter shown in FIG. A dielectric resonator 38 shown in FIG. 1 is used, a plate capacitor 50 is mounted on the open end of the resonator hole 32, and each capacitor 50 is connected by a coil 52. Here, in order to facilitate connection of the capacitor 5o, a rivet-shaped metal terminal 54 is fitted into each resonator hole 32 and soldered to the center conductor, and the plate capacitor 50 is placed on top of it and the soldering is fixed.

FIG. 11 shows a modification of the dielectric filter described above, which uses one capacitor substrate. As shown in FIG. 12, the capacitor substrate has electrodes 58 and 59 formed on the upper and lower surfaces of a dielectric substrate 56 corresponding to each resonator hole. A capacitor substrate is mounted on the dielectric resonator 38, and the electrode 59 on the lower surface and the center conductor are electrically connected. Then, the electrodes 58 on the upper surface are connected by a coil 52.

In the embodiment shown in FIG. 13, a dielectric resonator 38 and a capacitor substrate 62 are mounted on a base plate 64. Here, the capacitor substrate 62 has a plurality of capacitor sections of a pattern-gamble type, and the capacitor capacitance is realized by the electrode open circuit 11[d. Then, each center conductor is connected to one electrode 66a, and the other electrode 66b is coupled by a coil 52. Reference numeral 67 is an input/output terminal.

The capacitor substrate 6B may have a structure in which a chip capacitor 69 is mounted between electrodes, as shown in FIG. 14B.

Note that the above embodiments are all examples of a three-stage configuration in which three resonator holes are provided in the dielectric block, but the present invention also applies when there are two resonator holes or four or more resonator holes. It goes without saying that the invention can be applied. In each drawing depicting the external appearance of a dielectric resonator, the parts marked with small dots indicate the exposed surface of the dielectric material.
The shaded area represents the surface to which the conductive film is attached.

[Effects of the Invention] As described above, the present invention is basically integrated with a dielectric block and has a simple structure, so it is easy to manufacture and obtain stable electrical and mechanical properties. ,
It is easy to design because it is coupled using lumped constant elements, and frequency and coupling adjustment are also easy. As a result, cheaper band rejection filters and band encounter filters can be realized.

[Brief explanation of drawings]

FIG. 1A is a perspective view showing one embodiment of a dielectric resonator according to the present invention, B is a longitudinal sectional view thereof, and FIG. 2 is an explanatory diagram of a band rejection filter using a dielectric resonator according to the present invention. , FIG. 3 is an explanatory diagram of a bandpass filter. FIG. 4, FIG. 5, FIG. 6, FIG. 7, FIG. 8, and FIG. 9 are perspective views showing other embodiments of the dielectric resonator according to the present invention, respectively. FIG. 10A is a perspective view showing one embodiment of a dielectric filter according to the present invention, and FIG. 10B is a longitudinal sectional view thereof. FIG. 11 is a perspective view showing another embodiment of the dielectric filter;
Figure 12 is a perspective view of the capacitor board used for it,
Figure 3 is a perspective view showing another embodiment of the dielectric filter;
4A is a plan view of a capacitor substrate used therein, and B is a plan view showing another example of the capacitor substrate. FIG. 15A is an explanatory diagram showing an example of a conventional band-pass filter, B is an equivalent circuit diagram thereof, FIG. 16 is a filter characteristic diagram thereof, and FIG. 17A is an explanatory diagram showing an example of a conventional band-pass filter. B is its equivalent diagram IN! Figure r and Figure 18 are filter characteristic diagrams. 30... Dielectric block, 32... Resonator hole, 34
...Coupling blocking hole, 38...Dielectric resonator, 41°4
3...Groove, 45.47...Notch, 50...Capacitor, 52...Coil.

Claims (6)

[Claims] 1. A plurality of through holes each serving as a resonator hole are arranged in parallel in a dielectric block, and one of the surfaces where the through holes are open is an open surface, and a conductive film is formed on the inner wall surface of the through hole and the outer surface excluding the open surface. In a multi-stage coaxial resonator that forms a center conductor and an outer conductor, another through hole is formed between each resonator hole to serve as a coupling prevention hole, and a conductive film is provided on the inner wall surface of the through hole, and a conductive film is provided on the inner wall surface of the through hole. A dielectric resonator characterized in that a conductor film on an inner wall surface and the outer conductor are connected at an end by a conductor film. 2. The dielectric resonator according to claim 1, wherein the coupling blocking hole is a rectangular through hole long in the width direction of the dielectric block. 3. 2. The dielectric resonator according to claim 1, wherein the dielectric block has a shape in which a recess is provided near each coupling blocking hole. 4. A dielectric filter using the dielectric resonator according to claim 1, having a flat plate capacitor mounted on the open end of the resonator hole, and connecting the capacitors with a coil. 5. 5. The dielectric filter according to claim 4, wherein the plurality of capacitors each include a plurality of electrodes provided on both sides of a single dielectric substrate. 6. The dielectric resonator according to claim 1 and a capacitor substrate having a plurality of pattern gap type capacitor sections are installed on a base plate, the center conductor and one electrode of the capacitor section are respectively connected, and the center conductor is connected between the other electrodes. A dielectric filter that is connected with a coil.