JPH09153706A - Dielectric filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To deal with the high frequency of several GHz. SOLUTION: Concerning this dielectric filter, a coaxial dielectric resonator provided with external and internal conductor layers 5 and 6 on the outer surface of a dielectric member 2 and the inner surface of a through hole 3 while passing the through hole 3 through the dielectric member 2 and opening both the terminals of the through hole 3 on both end faces 4 and 4 of the dielectric member 2 is formed and these plural resonators are parallelly arranged in contact and electrically connected. This coaxial resonator is formed into a 1/2 wavelength type resonator 1 respectively exposing the dielectric member 2 on both the end faces 4 and 4 and between the adjacent resonators, an inter- step connection window 8 is provided for electrically connecting the adjacent resonators each other by removing one part of mutually contacting external conductor layers 5 of both the resonators. Then, resonators 10 and 11 at input and output steps are provided with external connection electrodes 7 near one end face 4 of respective resonators so as to be electrically connected through the dielectric member 2 to the internal conductor layer 6 separately from the external conductor layer 5 while removing one part of the external conductor layer 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency dielectric filter used for high frequency signals of several hundred MHz to several GHz.

[0002]

2. Description of the Related Art Currently, various high frequency filters are used in communication equipment. Especially, with the recent spread of mobile communication equipment such as mobile phones and car phones and the increase in communication usage, various filters have been used. , Support for higher frequencies,
Miniaturization and improvement of electrical characteristics are required. Conventionally,
A dielectric filter used at a high frequency has a through hole passing through both end faces (4) and (4) of the dielectric member (2) as shown in FIG.
(3) is formed, the outer peripheral surface of the dielectric member (2), the through hole (3)
1/4 wavelength type coaxial dielectric resonator in which conductor layers (5), (6) and (61) are provided on either one of the inner surface and the end surface (4) (4) of the dielectric member (2) doing. In the drawing, conductor layers (5) (6)
(61) is indicated by a thin broken line. Currently used resonators are formed in a rectangular parallelepiped so that they can be easily mounted on a substrate, and their dimensions are about 2 mm to about 4 mm on the end face.
It is a square of mm square and the length is 1/4 wavelength with respect to the resonance wavelength.

[0003]

SUMMARY OF THE INVENTION A coaxial dielectric resonator is
The higher the resonance frequency, the shorter the resonance wavelength,
As a result, it is necessary to shorten the length of the resonator. For example, in recent years, a filter that can be used in a high frequency band of 3 GHz or higher has been required as a communication filter. In that case, the length of the 1/4 wavelength coaxial dielectric resonator is about 2.6 mm because the relative permittivity of the high dielectric constant ceramics that has been conventionally used as the dielectric member (2) is about 90. Must be: At this time, the length of the resonator becomes as short as the dimension of the side of the end face of the resonator, and in addition to the TEM mode electromagnetic wave which is normally used, the TM mode or TE mode is used.
A so-called degeneration phenomenon occurs in which electromagnetic waves of modes are generated. Therefore, the resonance frequencies of the waves of other modes are mixed in the resonator, resulting in deterioration of the filter characteristics. As means for avoiding this, it is conceivable to reduce the size of the end face of the resonator and to use a material having a low relative dielectric constant as the dielectric material. However, it is difficult to manufacture the dimension of the end face of the resonator smaller than this, and if the dimension is made smaller, the Q value decreases and the filter characteristics deteriorate. Further, if a dielectric material having a low relative permittivity is used, it is necessary to prepare different dielectric materials depending on the frequency band used, resulting in an increase in manufacturing cost.

[0004]

SUMMARY OF THE INVENTION The present inventor has considered the use of a half-wave type coaxial dielectric resonator in order to solve the above problems. The 1/2 wavelength type is different from the 1/4 wavelength type in that both end faces of the dielectric are either covered with the conductor layer or both end faces have the dielectric member (2) exposed. There is. However, even if they have the same resonance frequency, the length is doubled as compared with the 1/4 wavelength type, which is disadvantageous in terms of downsizing. Therefore, in the past, as a small surface mount filter,
A quarter-wave resonator is used. On the other hand, the half-wave type uses a plurality of half-wave resonators (1) whose both ends are open, and adjusts the amount of electrical coupling between the resonators (1) as shown in FIG. A cylindrical filter arranged in series with a metal plate (81) interposed therebetween is used, and is mainly used for a large filter having a high Q value. However, in the above problem, if the half-wavelength type resonator (1) is used, the length of the resonator can be made longer than that of the quarter-wavelength type, so that the degeneracy phenomenon can be prevented. The present invention, in the high frequency band that can not be used 1/4 wavelength type coaxial resonator, using the 1/2 wavelength type coaxial resonator, moreover, like the 1/4 wavelength type, small surface mounting is possible,
An object of the present invention is to provide a dielectric filter having good filter characteristics.

[0005]

A through hole penetrates a dielectric member, and both ends of the through hole are opened to both end faces of the dielectric member.
A coaxial dielectric resonator having an outer conductor layer and an inner conductor layer is formed on the outer surface of the dielectric member and the inner surface of the through hole, and a plurality of the coaxial dielectric resonators are arranged in contact with each other in parallel and electrically. In the coupled dielectric filter, the coaxial dielectric resonator is
It is formed in a half-wave type with dielectric members exposed on both end faces, and between adjacent resonators, a part of the outer conductor layer that is in contact with both resonators is removed, and In the input stage and output stage coaxial dielectric resonators, a part of the outer conductor layer is removed to separate it from the outer conductor layer. And an external connection electrode electrically coupled to the internal conductor layer through the dielectric member.

[0006]

[Operation and effect] By changing the coaxial dielectric resonator from the conventional 1/4 wavelength type to 1/2 wavelength type, the coaxial length is doubled, but the maximum usable frequency is doubled. It can be used in a higher frequency band than the 1/4 wavelength type. Further, as for the pass characteristic of the dielectric filter having the above-described configuration, as shown in FIG. 3, the harmonic portion of the fundamental wave is suppressed, and a band pass filter having a good pass characteristic can be provided.

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings. As shown in FIG. 1D, the half-wavelength type coaxial dielectric resonator (1) having both ends opened, which is used in the dielectric filter according to the present invention, has a prismatic dielectric member.
A through hole (3) passing through both end faces (4) and (4) is formed for (2), and only both end faces (4) and (4) of the dielectric member (2) are removed,
An outer conductor layer (5) and an inner conductor layer (6) are formed by covering the outer surface and the entire inner surface of the through hole (3) with a conductive material. As the material of the dielectric member (2), high dielectric constant ceramics such as barium oxide, titanium oxide, and neodymium oxide are suitable. Further, as the conductive material, a high conductivity material such as silver or copper is suitable. The material and the material are the same as the conventional 1/4 wavelength type.

(Embodiment 1) In the dielectric filter of this embodiment, as shown in FIGS. 1A and 1B, two half-wavelength resonators (1) are arranged in parallel. . As shown in FIG. 1 (c), the through-hole of the resonator (1) is located at the contact surface of the resonator (1) (1) at a position approximately half the resonator length from the end face (4).
The outer conductor layer of both resonators (1) and (1) in the direction perpendicular to (3)
By deleting (5), the inter-stage coupling window (8) is formed. Further, in the vicinity of the one end face (4) of the one resonator (10), with respect to the outer conductor layer (5), from the outer face, that is, the side face opposite to the side face on which the interstage coupling window (8) is formed. The external connection electrode (7) is formed by removing the peripheral conductor layer (5) over the lower surface. The other resonator (11)
Also in the above, the similar external connection electrode (7) is formed at a position diagonal to the external connection electrode (7) with respect to the inter-stage coupling window (8). The external connection electrode (7) functions as an input terminal or an output terminal, and also functions as an electrical coupling means with the internal conductor layer (6).

The dielectric filter having the above structure is mounted on the printed circuit board as it is. At that time, the external connection electrode (70) of the input stage resonator (10) and the external connection electrode (71) of the output stage resonator (11) are connected to the input electrode and the output electrode of the substrate, respectively. The outer conductor layer (5) of the resonators (10) and (11) is connected to the ground electrode of the substrate. The equivalent circuit of the dielectric filter at this time is as shown in FIG. In the resonator (10) of the input stage, a capacitive coupling C1 is formed between the external connection electrode (70) which becomes the input terminal IN and the internal conductor layer (6), and the same applies to the resonator (11) of the output stage. Then, the capacitive coupling C2 is formed between the external connection electrode (71) which becomes the output terminal OUT and the internal conductor layer (6). And the resonator (10) (11)
The interstage coupling inductance (L) is set by the
Form one. Also, pass characteristics of the dielectric filter is as shown in FIG. 3, realized by the filter using conventional quarter-wavelength coaxial resonators has been difficult, the fundamental wave f ₀ ≒
A bandpass filter in the frequency band at 4 GHz can easily be provided. Moreover, the use of interstage coupling window (8) and the external connection electrodes (7), attenuation of the harmonics 2f _0, 3f near ₀ of the fundamental wave f ₀ is increased, the fundamental wave f ₀ and a second
The amount of attenuation between the harmonics 2f ₀ also increases, and therefore the pass characteristic can be improved.

In this embodiment, two half-wave type coaxial resonators (1) are used, but as shown in FIG. 4, three or more resonators (1) are used. May be used. At that time, the structures of the input stage resonator (10) and the output stage resonator (11) are the same as above, but the intermediate stage resonator (12) is
Interstage coupling windows (8) and (8) are formed on the side surfaces adjacent to the other resonators (10) and (11), respectively, and the external connection electrodes (7) are not formed. By increasing the number of resonators (1) to be connected, the pass characteristic in the vicinity of the fundamental wave f ₀ can be changed.

(Embodiment 2) As shown in FIG. 5, the dielectric filter of this embodiment has a resonator as compared with the first embodiment.
An outer conductor layer (5) and an inner conductor layer (6) extend on both end faces (4) and (4) of (1). In order to form such a resonator, the entire outer surface of the dielectric member (2) and the entire inner surface of the through hole (3) are coated with a conductive material to form a conductor layer, and then the end surface (4 ), The conductor layer having a predetermined radius surrounding the through hole (3) may be removed in a ring shape. The equivalent circuit at this time is
As shown in FIG. 6, on the end face (4) of the resonator (1), a capacitive coupling C3 is formed between the extended outer conductor layer (5) and inner conductor layer (6). Therefore, the length of the resonator with respect to the resonance frequency f ₀ can be shortened, and a smaller dielectric filter can be provided. Also, as in the first embodiment, three or more resonators can be used in this embodiment as well, in which case the external connection electrode (7) is used in the intermediate-stage resonator.
Is not formed, the inter-stage coupling window 8 is formed on both side faces adjacent to other resonators.

In the above embodiment, the external connection electrode (7) is formed from the lower surface of the filter to the outer surface, because this is because it is easy to connect to the input / output electrodes on the printed circuit board. The electrode (7) is located near the end face (4), separated from the outer conductor layer (5), and can be electrically connected to the inner conductor layer (6), so that the position and shape can be freely set. You can choose.

The above description of the embodiments is for explaining the present invention, and should not be construed as limiting the invention described in the claims or reducing the scope. or,
The configuration of each part of the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made within the technical scope described in the claims.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a first embodiment of the present invention,
(A) is a perspective view, (b) is a bottom view, (c) and (d) are a perspective view and a sectional view of a 1/2 wavelength type coaxial dielectric resonator used, respectively.

FIG. 2 is an equivalent circuit diagram of the first embodiment.

FIG. 3 is a diagram showing a pass characteristic of the first embodiment.

FIG. 4 is a perspective view in which three half-wavelength coaxial dielectric resonators are used in the first embodiment, FIG.
(B) is a bottom view.

FIG. 5 is a second embodiment, (a) is a perspective view,
(B) is sectional drawing of the 1/2 wavelength type coaxial dielectric resonator used.

FIG. 6 is an equivalent circuit diagram of the second embodiment.

7A and 7B are schematic diagrams showing a conventional quarter-wave coaxial dielectric resonator, in which FIG. 7A is a perspective view, FIG. 7B is a perspective view seen from the back side of FIG. 7A, and FIG. Is a sectional view.

FIG. 8 is a schematic diagram showing a conventional half-wave type coaxial dielectric resonator.

[Explanation of symbols]

 (1) 1/2 wavelength type coaxial dielectric resonator (2) Dielectric member (3) Through hole (4) End surface of dielectric member (5) External conductor layer (6) Internal conductor layer (7) External connection electrode ( 8) Interstage coupling window

Claims (4)

[Claims] 1. A through hole (3) penetrates a dielectric member (2), and both ends of the through hole (3) are both end faces (4) of the dielectric member (2).
An outer surface of the dielectric member (2) and a through hole (3) opened in (4)
A coaxial dielectric resonator having an outer conductor layer (5) and an inner conductor layer (6) is formed on the inner surface, and a plurality of the coaxial dielectric resonators are arranged in contact with each other in parallel and electrically coupled to each other. In the body filter, the coaxial dielectric resonator is formed on the half-wave type coaxial dielectric resonator (1) in which the dielectric members (2) are exposed at both end faces (4) and (4), respectively, and the adjacent resonance is formed. Between the children, a part of the outer conductor layer (5) of both resonators contacting each other is removed, and an inter-stage coupling window (8) for electrically coupling adjacent resonators is provided,
In the coaxial dielectric resonators (10) and (11) at the input stage and the output stage, an outer conductor layer is provided near one end face (4) of each.
A dielectric having an external connection electrode (7) separated from the outer conductor layer (5) by partially removing (5) and electrically coupled to the inner conductor layer (6) through the dielectric member (2). Body filter. 2. The dielectric filter according to claim 1, wherein the inter-stage coupling window (8) is formed near the center of the resonator corresponding to the node of the resonance waveform in the direction of the through hole (3). 3. External input electrodes (70) (7) for input and output
The dielectric filter according to claim 1 or 2, wherein 1) are formed on opposite sides with respect to the direction of the through hole (3). 4. The outer conductor layer (5) and the inner conductor layer (6) are
The dielectric filter according to any one of claims 1 to 3, which is formed to extend to an end surface (4) of the dielectric member (2).