JPH0818306A - Dielectric filter - Google Patents

Abstract

PURPOSE:To provide a dielectric filter which is reduced in the number of parts, inexpensive and can be miniaturized by setting the phase in the input/output part to a desired value without adding parts for phase adjustment. CONSTITUTION:Resonator holes 2 and 2 whose inside faces are formed with inner conductors 3 are formed in a dielectric block 1, and a pair of excitation holes 5 and 5 are provided on the outsides of resonator holes 2 and 2. Input/ output electrodes 7 and 7 which are made conductive to the inner conductor 3 of excitation holes 5 and are separated from an outer conductor 4 are formed on an end face 1b on the short-circuit side, and the inner conductor 3 of excitation holes 5 is made conductive to the outer conductor in an end face 1a on the open side. In this constitution, forming positions, shapes, and sizes of excitation holes 5 are changed to obtain desired external coupling and phase.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to, for example, a car telephone,
The present invention relates to a dielectric filter used in mobile communication devices such as mobile phones.

[0002]

2. Description of the Related Art A conventional dielectric filter using a dielectric block has, for example, a structure as shown in FIG. In the following figures, the dot-filled portion shows the visible portion (conductor non-forming portion) of the dielectric block.

As shown in FIG. 5, this dielectric filter has a pair of opposed end faces 1a, 1b of a dielectric block 1.
Through which a resonator hole 2 is formed with an inner conductor 3 formed on the inner surface thereof, an outer conductor 4 is formed on the outer surface of the dielectric block 1, and a pair of outer conductors 4 are formed at predetermined positions on the outer conductor 4. Input / output electrodes 7, 7 are formed.

This dielectric filter has resonator holes 2 and 2 respectively.
It consists of two stages of resonators formed for each, and between each resonator,
So-called comb line coupling is performed by stray capacitance generated in the inner conductor non-forming portion formed on the open end face side, and external coupling is performed by external coupling capacitance Ce generated between the input / output electrode 7 and the corresponding inner conductor 3. Is getting

When an antenna duplexer is constructed by using, for example, two of these dielectric filters, there is a reflection phase in the pass band of the other filter between the antenna end, which is the common input / output end of both filters, and the filter. A demultiplexing circuit for adjusting the phase is inserted so as to be open. As the branching circuit, a lumped constant element such as a capacitance element or an inductance element, or a distributed constant line such as a cable or a strip line is used.

[0006]

As described above, when a conventional dielectric filter is used to construct an antenna duplexer, etc., it is added to the dielectric filter to adjust the phase of capacitors, coils, strip lines, etc. Components are needed, and they are assembled on the board and soldered,
Alternatively, work such as forming on a substrate is required. Therefore, there is a problem that miniaturization is difficult, and component cost and manufacturing cost increase.

That is, in the conventional dielectric filter, when the degree of external coupling at the input / output section is determined, its phase is also determined, and the external coupling and phase cannot be set independently, so that the desired external filter cannot be set. It is difficult to obtain the coupling and the phase at the same time, and when the phase is related to the connection with another filter or an external circuit, it is necessary to add another component for adjusting the phase.

Therefore, an object of the present invention is to solve the above-mentioned problems of the conventional dielectric filter and to set the phase at the input / output unit to a desired value without adding a component for phase adjustment. Therefore, it is an object of the present invention to provide a dielectric filter that can be set to, and thus can be manufactured at a low cost and with a reduced number of parts.

[0009]

In order to achieve the above object, the invention according to claim 1 forms a resonator hole between a pair of opposed end faces of a dielectric block, and an inner surface of the resonator hole. In a dielectric filter comprising an inner conductor and an outer conductor formed on the outer surface of a dielectric block, next to the resonator hole corresponding to the input / output stage, an excitation hole having an inner conductor formed therein is provided. So that the desired outer coupling and phase are obtained,
It is characterized in that the formation position, shape and size of the excitation hole are set.

According to a second aspect of the present invention, in the invention according to the first aspect, the dielectric block is electrically connected to the inner conductor of the excitation hole and separated from the outer conductor across one end face or the end face and the side face. It is characterized in that an input / output electrode is formed.

[0011]

According to the first aspect of the invention, the external coupling of the filter can be obtained by the electromagnetic field coupling between the excitation hole and the resonator hole adjacent thereto, and the formation position, shape and size of the excitation hole can be changed. Can set the desired external coupling and phase.

According to the second aspect of the invention, in addition to the above operation, the input / output electrodes electrically connected to the inner conductor of the excitation hole can be connected to the external circuit.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing the embodiments thereof. In the figure, the same or corresponding parts and those having the same functions as those in the conventional example are designated by the same reference numerals.

The structure of the dielectric filter according to the first embodiment of the present invention is shown in FIG. FIG. 1 is an external perspective view of the dielectric filter as viewed from the open end surface side.

In the dielectric filter of this embodiment, as shown in FIG. 1, a pair of opposed end faces 1a and 1b of a substantially rectangular parallelepiped dielectric block 1 are penetrated, and inner conductors 3 are formed on the inner faces thereof. The two resonator holes 2 and 2 and the pair of excitation holes 5 and 5 are formed, and the outer conductor 4 is formed on substantially the entire outer surface of the dielectric block 1. The excitation holes 5 and 5 are formed outside the resonator holes 2 and 2, respectively, and extend over the short-circuit side end face 1b and the one side face 1c (upper surface in the figure) to be electrically connected to the inner conductor 3 of the excitation holes 5 and 5. A pair of input / output electrodes 7, 7 that are separated from the outer conductor 4 are formed. That is, the inner conductors 3, 3 of the excitation holes 5, 5 are separated from the outer conductor 4 at the short-circuit side end face 1b and are electrically connected to the outer conductor 4 at the open side end face 1a. Further, the inner conductors 3 and 3 of each resonator hole 2 and 2 are provided with an inner conductor non-formation portion in the vicinity thereof on the open side end surface 1a, separated (opened) from the outer conductor 4, and external on the short-circuit side end surface 1b. It is electrically connected (short-circuited) with the conductor 4.

In this dielectric filter, the excitation hole 5 and the resonator hole 2 adjacent to the excitation hole 5 are electromagnetically coupled, and this electromagnetic field coupling is configured to obtain external coupling of the input / output portion of the dielectric filter. Therefore, the input / output electrodes 7 and 7 are formed merely for connection with an external circuit.

The desired external coupling and phase can be set by changing the formation position, shape, and inner size (size) of the excitation hole. That is, the phase can be changed while the external coupling is kept constant.

The relationship between the formation position and shape of the excitation hole and the external coupling and phase will be described below based on experimental results.

2 (a) to 2 (d) are schematic cross-sectional views in the vicinity of the excitation hole forming portion of the dielectric filter, in which the formation position, shape, etc. of the excitation hole 5 are changed, and the inner conductor and the outside of the excitation hole 5 are changed. FIG. 6 is a diagram showing a method of setting the self-capacitance C ₁₁ of the excitation hole 5 formed between the conductors and the mutual capacitance C ₁₂ formed between the excitation hole 5 and the inner conductor of the resonator hole 2.

In FIG. 2A, the excitation hole 5 is formed on either side of the upper and lower sides (lower side in the figure) to increase the self-capacitance C ₁₁ and reduce the mutual capacitance C _12. 2B and 2C, the self-capacitance C ₁₁ and the mutual capacitance C ₁₂ can be set in various ways by making the shape of the excitation hole 5 substantially elliptical and changing its forming direction. Therefore, in FIG. 2D, the self-capacitance C ₁₁ and the mutual capacitance C ₁₂ are both increased by increasing the inner diameter of the excitation hole 5. in this way,
The self-capacitance C ₁₁ and the mutual capacitance C ₁₂ can be changed by changing the formation position, shape, size, etc. of the excitation hole.

FIG. 3 shows the relationship between these capacitors C ₁₁ and C ₁₂ and the external coupling, and the relationship between the phases. FIG. 3 shows an example of the result of measurement of the reflection phase between 869 and 894 MHz, which is the pass band of the counterpart filter, with the center frequency set to 836.5 MHz, for example. In FIG. 3, the self-capacitance C ₁₁ of the excitation hole when the external coupling is fixed to a certain value
And the mutual capacitance C ₁₂ are indicated by Δ, and the relation between the self-capacitance C ₁₁ and the reflection phase at 869 MHz and 894 MHz at this time is indicated by ○ and ●.

As shown in FIG. 3, the external coupling can be made constant by changing the self-capacitance C ₁₁ and the mutual capacitance C ₁₂ by changing the formation position and shape of the excitation hole, and the reflection phase can be greatly changed. Can be made. That is, the self capacity C
By making both ₁₁ and the mutual capacitance C ₁₂ small, the reflection phase can be made smaller, that is, the reflection phase can be close to open, while keeping the external coupling constant.

Therefore, when an antenna duplexer is constructed by using this dielectric filter, the formation position, shape, size, etc. of one excitation hole corresponding to the antenna end are changed so that the pass band of the partner filter is changed. Since the reflection phase of can be made open, the antenna duplexer can be easily configured without adding another component such as a capacitance element, an inductance element, or a strip line for phase adjustment. That is, an antenna duplexer can be constructed by using two of these dielectric filters or using this dielectric filter and the conventional dielectric filter shown in FIG. 5 and directly connecting one input / output electrode. .

Not only when applied to an antenna duplexer, but also when it is necessary to change the phase of the input / output section in connection with an external circuit, another component for phase adjustment is similarly added. It is possible to obtain a proper matching with an external circuit without any trouble.

The shape of the excitation hole may be any shape, and may be an elliptical shape, a rectangular shape, a triangular shape or the like. Further, in the above-described embodiment, the dielectric filter including the two-stage resonators is described, but a dielectric filter including one-stage or three-stage or more resonators may be used.

Next, FIG. 4 shows the structure of the antenna duplexer according to the second embodiment of the present invention. FIG. 4 is an external perspective view of the antenna duplexer viewed from the open end face side.

The antenna duplexer according to this embodiment is shown in FIG.
, A pair of end faces 1a, 1 of the dielectric block 1
5 resonator holes 2a to 2e are formed through b.
Excitation holes 5a, 5b, 5c are formed outside the resonator holes 2a, 2e and between the resonator holes 2b, 2c, and are formed on the inner surfaces of the resonator holes 2a to 2e and the excitation holes 5a, 5b, 5c. Has an inner conductor 3 formed therein. An outer conductor 4 is formed on substantially the entire outer surface of the dielectric block 1. Each excitation hole 5a, 5b, straddling the short-circuit side end face 1b and the one side face 1c,
There are formed three input / output electrodes 7a, 7b, 7c that are electrically connected to the inner conductor 3 of 5c and separated from the outer conductor 4. That is,
The inner conductor 3 of each excitation hole 5a, 5b, 5c has an open end face 1a.
Is conductive with the outer conductor 4, and is separated from the outer conductor 4 at the short-circuit side end face 1b. The inner conductor 3 in each of the resonator holes 2a to 2e is separated from the outer conductor 4 by the inner conductor non-forming portion on the open side end face 1a side, and is electrically connected to the outer conductor 4 on the short side end face 1b.

This antenna duplexer has resonator holes 2a, 2
It is composed of a transmission filter (or a reception filter) including two resonators corresponding to b and a reception filter (or a transmission filter) including three resonators corresponding to the resonator holes 2c, 2d, and 2e. The excitation holes 5a and 5c and the resonator holes 2a and 2e, and the excitation hole 5b and the resonator holes 2b and 2c adjacent to the excitation holes 5b and 2c are electromagnetically coupled to each other, and external coupling is obtained by this electromagnetic field coupling. The input / output electrode 7b between the resonator holes 2b and 2c is an antenna electrode that shares the input and output of the transmission filter and the reception filter.

In this antenna duplexer, desired external coupling is obtained and the reflection phase is opened in the pass band of the counterpart filter by changing the formation position of the excitation hole 5b that shares the input and output of both filters. Is set so that

As described above, the phase at the antenna end of both filters can be changed by changing the formation position, shape, etc. of the excitation hole without adding a separate component for phase adjustment. It is possible to form a high-performance antenna duplexer by integrally forming two dielectric filters on the body block, and it is possible to reduce the size and cost of the antenna duplexer.

In each of the above embodiments, the input / output electrodes are formed on the short-side end face, but the present invention is not limited to this, and the input / output electrodes may be formed on the open-side end face. The shape and the like are not particularly limited.
Alternatively, a metal terminal or the like may be used to connect to an external circuit without forming the input / output electrodes.

Further, the coupling between the resonators does not have to be due to the stray capacitance formed in the inner conductor non-forming portion, other coupling means such as coupling holes may be used, and the resonators on the open side end face side may be used. Separation of the inner conductor and the outer conductor of the hole is not limited to the embodiment.

In short, according to the present invention, the input / output portion of the dielectric filter is provided with an excitation hole having a conductor formed therein,
It is characterized in that desired external coupling is obtained by changing the formation position, shape, and size of the excitation hole, and the phase of the desired input / output section is obtained. It is not particularly limited.

[0034]

As described above, according to the dielectric filter of the present invention, an excitation hole is provided at the input / output portion of the dielectric filter, and the formation position, shape, and size of this excitation hole are set appropriately. As a result, a desired outer coupling and phase can be obtained. That is, by using the dielectric filter of the present invention, an antenna duplexer or the like can be configured by directly connecting another dielectric filter without adding a phase adjusting component such as a capacitor, a coil, or a strip line. Therefore, it is possible to reduce the number of parts, and therefore, it is possible to reduce the size and significantly reduce the parts cost and the manufacturing cost. Further, since a plurality of dielectric filters can be integrally formed on one dielectric block to easily construct an antenna duplexer, further miniaturization and cost reduction can be realized.

[Brief description of drawings]

FIG. 1 is an external perspective view of a dielectric filter according to a first embodiment of the present invention.

2A to 2D are schematic cross-sectional views in the vicinity of an excitation hole forming portion of the dielectric filter of the present invention.

FIG. 3 is a diagram showing a relationship between self-capacitance and mutual capacitance of an excitation hole of a dielectric filter of the present invention, and a relationship between self-capacitance and reflection phase.

FIG. 4 is an external perspective view of an antenna duplexer according to a second embodiment of the present invention.

FIG. 5 is an external perspective view of a conventional dielectric filter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dielectric block 2, 2a-2e Resonator hole 3 Inner conductor 4 Outer conductor 5, 5a-5c Excitation hole 7, 7a-7c Input / output electrode

Claims (2)

[Claims] 1. A dielectric material comprising a resonator block, a resonator hole formed between a pair of opposing end faces, an inner conductor formed on the inner surface of the resonator hole, and an outer conductor formed on the outer surface of the dielectric block. In the body filter, an excitation hole having an inner conductor formed inside is provided next to the resonator hole corresponding to the input / output stage, and the position and shape of the excitation hole are formed so that desired external coupling and phase can be obtained. , A dielectric filter having a set size. 2. An input / output electrode, which is electrically connected to the inner conductor of the excitation hole and separated from the outer conductor, is formed on one end surface of the dielectric block or across the end surface and the side surface. Item 2. The dielectric filter according to item 1.