JPH0795642B2 - Dielectric filter - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric filter having an integral structure mainly used in a high frequency region such as a microwave band.

2. Description of the Related Art In recent years, a dielectric material having a high dielectric constant, a low loss and a good temperature characteristic in a high frequency region has been developed, and a dielectric filter using the dielectric material has been actively developed. In particular, recently, an integrated type dielectric filter having a resonance hole, a coupling hole, and a conductor film in a dielectric block using the above-mentioned dielectric material (for example, described in JP-A-62-165401) has been realized. , Downsizing and cost reduction have been achieved. Hereinafter, a conventional integrated structure type dielectric filter will be described with reference to FIG. Here, as an example thereof, an example of a three-stage structure of resonance holes will be described.

In FIG. 4, 11 is a rectangular parallelepiped dielectric block, 24 to
26 is a resonance hole formed in parallel in the dielectric block 11 at a predetermined interval, 37 and 38 are coupling holes formed between the resonance holes 24 to 26, 4
4 is an outer conductor film formed on the outer surface other than the upper surface of the dielectric block 11, 41 to 43 are formed on the inner peripheral surfaces of the resonance holes 24 to 26, respectively, and one end is connected to the outer conductor film 44. It is the inner conductor film. With the above configuration, the resonance holes 24 to 26 operate as a quarter-wavelength resonance element with one end open and one end shorted, and the coupling hole 3
7,38 form the inter-stage coupling between the resonance holes. Resonance hole
24 and 26 are connected to an external circuit via, for example, a capacitive element or the like (not shown).

In the above structure, the above-mentioned conventional example operates as a band pass filter having a three-stage structure having three resonance holes 24 to 26.

However, since the dielectric filter having the above-described structure has an integrated structure, it is not necessary to individually assemble and assemble the unit resonators, and at the same time, the coupling substrate is not required. It has advantages in manufacturing such as easy manufacturing and cost reduction.
Since a quarter-wavelength resonant element is used, a pass band is generated even for odd-order harmonics such as third-order, fifth-order, oscillator,
As an output filter of a class C amplifier or the like, there is a characteristic problem that it does not have a harmonic suppression effect.

The present invention solves the above problems of the prior art, is easy to manufacture, can be manufactured at low cost, and has an integrated structure,
An object of the present invention is to provide a dielectric filter having a harmonic suppression effect.

Means for Solving the Problems The present invention achieves the above object by providing at least one portion where the hole diameter of the connecting hole is changed in a step shape or a taper shape.

Action The present invention has a filter having a harmonic suppression effect by partially changing the line impedance of the resonance hole that operates as a resonance element and shifting the spurious resonance frequency from an odd multiple of the fundamental resonance frequency. It was realized.

Further, the harmonic suppression effect according to the above configuration can be obtained only by changing the internal structure of the conventional dielectric block without adding a special external circuit. Since the dielectric block is usually manufactured by molding it in a mold and then firing it, a slight modification of the mold is required to change the internal structure. It is the same. Therefore, the manufacturing advantage of the dielectric filter having the integral structure that the manufacturing is easy and the cost can be reduced is not impaired.

As described above, it is possible to realize a dielectric filter having an integrated structure which is easy to manufacture and can be manufactured at low cost and has a harmonic suppression effect.

First Embodiment A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a dielectric filter having an integral structure according to the first embodiment of the present invention. This embodiment is also an example of the same three-stage structure as the conventional example. In FIG. 1, 11
Is a rectangular parallelepiped dielectric block, 21 to 23 are resonance holes formed in parallel in the dielectric block 11 at a predetermined interval, and 31, 32 are hole diameters between the resonance holes 21 to 23 which are changed in steps. Formed on the outer surface of the dielectric block 11 excluding the upper surface of the dielectric block 11, and 41 to 43 are resonance holes 21.
To 23, inner conductor films formed on the inner peripheral surface and having one end connected to the outer conductor film 44, and 51, 52 are capacitive elements for connecting to an external circuit.

The operation of the above configuration will be described below.

Resonance hole 21 formed in rectangular parallelepiped dielectric block 11
~ 23, by changing the hole diameter of the coupling holes 31, 32 in steps, the line impedance partially changes,
The spurious resonance frequency can be shifted from an odd multiple. Together with the desired degree of interstage coupling by the coupling holes 31 and 32 and the input / output coupling with the external circuit by the capacitive elements 51 and 52, it operates as a three-stage band pass filter.

As is clear from the above description, according to the present embodiment, between the resonance holes 21 to 23, by providing the coupling holes 31 and 32 with the hole diameter changed stepwise, the line of the resonance element is formed. By partially changing the impedance and shifting the spurious resonance frequency from an odd multiple, it becomes possible to realize a monolithic dielectric filter having a harmonic suppression effect and easy to manufacture.

Next, a second embodiment of the present invention will be described.

FIG. 2 is a perspective view of a dielectric filter according to the second embodiment of the present invention. This embodiment also has a three-stage structure.

In FIG. 2, the difference from the configuration of FIG.
The point is that the shape of 3,34 was changed to a tapered hole diameter. The components having the same numbers as those in FIG. 1 have the same functions as those in FIG.

The operation of the above configuration will be described below.

Resonance hole 21 formed in rectangular parallelepiped dielectric block 11
Connecting holes 33,3 with the hole diameter tapered between 23 and 3
By forming 4, it is possible to realize a resonator in which the line impedance of the resonance element is partially changed and the spurious resonance frequency is shifted from an odd multiple, as in the embodiment shown in FIG. Operation as a band pass filter with an odd multiple harmonic suppression effect in combination with the desired degree of interstage coupling by coupling holes 33 and 34 and input / output coupling by connecting capacitive elements 51 and 52 with external circuits do.

As described above, according to the present embodiment, between the resonance holes 21 to 23, by providing the coupling holes 33 and 34 in which the hole diameter is changed in a tapered shape, the line impedance of the resonance element is partially changed, By shifting the spurious resonance frequency from an odd multiple,
It is possible to realize a dielectric filter having an integral structure that has a harmonic suppression effect and is easy to manufacture.

Next, a third embodiment of the present invention will be described.

FIG. 3 is a perspective view of a dielectric filter according to the third embodiment of the present invention. This embodiment also has a three-stage structure.

In FIG. 3, the structural difference from FIG. 1 is that the connecting holes 35, 3
6 is a shape, and in detail, in FIG. 1, all the coupling holes have a large diameter part on the lower side of the shaft (short-circuited end face side),
While the small diameter portion is formed so as to be on the upper side (open end surface side) of the shaft, in the present embodiment, the first coupling hole is formed.
35 is formed such that the large diameter portion is on the lower side of the shaft (short-circuited end surface side) and the small diameter portion is on the upper side of the shaft (open end surface side). The open end surface side) and the small diameter portion are formed below the shaft (short-circuit end surface side). That is, in FIG. 1, the positions of the large diameter portion and the small diameter portion on the shaft of the two coupling holes formed between the resonance holes are the same, whereas in this embodiment, the two coupling holes are located. The large diameter portion and the small diameter portion are formed so that the positions thereof are different.

The operation of the above configuration will be described below.

Resonance hole 21 formed in rectangular parallelepiped dielectric block 11
The first coupling hole 35 in which the hole diameter is changed stepwise so that the large diameter portion is on the lower side of the shaft (short-circuited end surface side) and the small diameter portion is on the upper side of the shaft (open end surface side) between 23 , And the second coupling hole 36 with the hole diameter changed stepwise so that the large diameter portion is on the upper side of the shaft (open end surface side) and the small diameter portion is on the lower side of the shaft (short circuit end surface side). By changing the line impedance of the resonant element, the resonators (holes 21, 22, 23 for resonance) that have the same fundamental resonance frequency but shift the spurious resonance frequencies from odd multiples to different frequencies are realized. ing. It works as a band pass filter in combination with the desired degree of inter-stage coupling by the coupling holes 35, 36 and the input / output coupling by the connecting capacitors 51, 52 with the external circuit.
Since each resonator has a different spurious resonance frequency, it is possible to realize a band pass filter that cancels each other out and has a wide stop band, and to have a harmonic suppression characteristic.

As described above, according to the present embodiment, the positions of the large diameter portion and the small diameter portion of the coupling hole having the resonance holes 35 and 36 sandwiched between the resonance holes 21 to 23 formed in the dielectric block. Is set to be different for each coupling hole, so that the line impedance of the resonant element is partially changed. In this case, since the spurious resonance frequencies of the resonators are different from each other, a band pass filter having a wide cancellation band can be realized. Therefore, a harmonic suppression effect can be obtained.

In the present embodiment, the hole diameters of the coupling holes 35, 36 are changed in a step shape, but they may be changed in a taper shape.

In addition, as for the hole diameter of the connecting hole, in both FIG. 1 and FIG. 2, the upper side (open end surface side) of the hole shaft is the small diameter portion, and the lower side (short circuit end surface side) of the hole shaft is the large diameter portion. Although it is formed, it is not limited to this as long as it changes the line impedance of the resonator, and the upper side (open end face side) of the hole shaft is the large diameter part and the lower side of the hole shaft is the small diameter part. It is also possible to form a combination hole having a stepped hole diameter and a uniform connection hole.

EFFECTS OF THE INVENTION As described above, the present invention provides the line impedance of the resonator by providing the coupling hole having the hole diameter changed in the step shape or the taper shape between the resonance holes formed in the dielectric block. By partially changing the superior resonance frequency by an odd number, changing the combination type of the coupling holes that are changed in a step shape or taper shape, or by combining them with a uniform coupling hole. By canceling out the spurious resonance frequencies of the above, a simple structure of the dielectric filter having a harmonic suppression characteristic can be realized, and its effect is great.

[Brief description of drawings]

1 is a perspective view of a dielectric filter according to a first embodiment of the present invention, FIG. 2 is a perspective view of a dielectric filter according to a second embodiment of the present invention, and FIG. 3 is a third view of the present invention. FIG. 4 is a perspective view of a dielectric filter in the example, and FIG. 4 is a perspective view of a conventional dielectric filter. 11 ... Dielectric block, 21-26 ... Resonance hole, 31-38 ... Coupling hole, 41-43 ... Inner conductor film, 44 ... Conductor film, 51, 52 ... Connection capacitive element.

Claims (2)

[Claims] 1. A rectangular parallelepiped dielectric block, and a plurality of resonance holes formed in parallel in the dielectric block at predetermined intervals,
A coupling hole formed between the resonance holes, an outer conductor film formed on the outer surface except one surface orthogonal to the axis of the resonance hole of the dielectric block, and an inner peripheral surface of the resonance hole. A dielectric filter, comprising: an inner conductor film formed at one end thereof and connected to the outer conductor; and one or more places where the hole diameter of the coupling hole is changed stepwise. . 2. A dielectric filter, wherein the hole diameter of the coupling hole is changed to the stepped shape according to claim 1 and is changed to a tapered shape.