JPH05343902A - High frequency filter - Google Patents

Abstract

(57) [Summary] [Construction] External electrodes 4 are formed on the surface of the dielectric block 2, and the dielectric block 2 is formed inside the dielectric block 2.
A plurality of internal electrodes 3 are embedded in parallel in the same plane in close contact with each other. The internal electrodes 3 are formed in a flat plate shape having open ends and projecting capacitive coupling electrode portions 5. High frequency filter. As the coupling between the high frequency resonators 10 is performed by the protruding capacitive coupling electrode 5 formed on the internal electrode 3, the coupling can be made stable, and the high frequency filter Miniaturization is possible. Further, the coupling capacitance can be changed by changing the shape of the protruding capacitive coupling electrode 5, and filters having various bandwidths can be configured without changing the distance between the high frequency resonators. ..

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency filter, and more particularly to a high frequency filter used as a component of a wireless communication device such as a car phone, a mobile phone, a cordless phone or the like in the microwave frequency range. ..

[0002]

2. Description of the Related Art Generally, a microwave filter is a combination of a high frequency resonator capable of obtaining a predetermined function and effect by confining a microwave having a predetermined resonance frequency in a dielectric block formed of a high dielectric constant material. It is composed of

9A and 9B show a filter in which a coaxial dielectric resonator 60 which has been conventionally used as this type of filter is combined, and FIG. 9A is a front view and FIG. 9B is a plan view. The coaxial dielectric resonator 60 uses a microwave of 1/4 wavelength corresponding to 1/4 of 1 wavelength as a resonance frequency (resonance line wavelength), and has two or more dielectrics formed in a cylindrical shape. External electrodes 63 are formed on the outer peripheral surface of the body block 61, and internal electrodes 62 are formed on the inner peripheral surface of the dielectric block 61. A filter is constructed by coupling these coaxial dielectric resonators 60 with a resonator coupling capacitor 64 (Japanese Patent Laid-Open No. 59-114902).
(See the official gazette).

FIG. 10 shows a dielectric block integral type filter which has been conventionally used as described above.
(A) is a perspective view, (b) is a YY 'line sectional view in (a). Two through holes 77 are formed in the dielectric block 71, an internal electrode 72 is formed in this through hole 77 portion, and an external electrode 73 is formed on the outer peripheral surface of the dielectric block 71.
Are formed, and two coaxial dielectric resonators 70 are formed. Further, slits 78 are formed between the through holes 77, and two coaxial dielectric resonators 70 corresponding to the respective through holes 77 are magnetically coupled to form a filter.

FIG. 11 is a perspective view showing a filter in which a resonator 80 to which a conventionally used microstrip line is applied is combined similarly to the above. This filter uses a microstripline resonator 8 whose resonance frequency (resonance line wavelength) is a microwave of an integral multiple of 1/2 wavelength.
0 is combined, and an input / output electrode 85a and a resonance electrode 85b are formed on the front surface of the dielectric block 81 formed in a planar shape, and a ground electrode 86 is formed on the back surface of the dielectric block 81. Has been done. The microstrip line resonator 80 corresponding to the resonance electrode 85b is magnetically coupled to form a filter.

FIG. 12 is a perspective view showing a filter in which a resonator 90 to which a triplate type strip line which has been conventionally used is applied is combined as in the above. Two flat plate-shaped internal electrodes 92 are formed inside the dielectric block 91, and external electrodes 93 are formed on the surface of the dielectric block 91. The microstrip line resonator 90 corresponding to the internal electrode 92 is magnetically coupled to form a filter.

[0007]

In the filter in which the coaxial dielectric resonator 60 shown in FIG. 9 is combined,
Although the structure of the coaxial dielectric resonator 60 is simple, the frequency (resonance frequency) of the microwave confined in the dielectric block 61 depends on the shape and dimensions of the dielectric block 61 and the dielectric constant of the material forming the dielectric block 61. Determined by Therefore, when the degree of freedom in design is reduced and the resonance frequency is relatively low even in the frequency range of the microwave, the dielectric block 61 becomes large and the resonance frequency of the coaxial dielectric resonator 60 can be adjusted. There was a problem that it would be difficult. Further, since the resonator coupling capacitor 64 and the input / output coupling capacitor 65 are arranged outside, this hinders downsizing and at the same time requires a shield at the coupling portion, which complicates the manufacturing process and increases the cost. There was a problem of becoming.

In the dielectric block integrated filter shown in FIG. 10, the slit 7 serving as a resonator coupling portion is used.
Although 8 is built in, it is necessary to form the through hole 77 and the slit 78, and like the coaxial dielectric resonator 60 shown in FIG.
There is also a problem that it is difficult to adjust the resonance frequency.

Further, the filter in which the microstripline resonator 80 shown in FIG. 11 is combined is designed because the input / output electrode 85a and the resonance electrode 85b can be formed on the surface of the dielectric block 81 by a printed pattern. Since the metallization can be formed using a thick film printing technique, it can be manufactured at low cost. However, the input / output electrode 85a and the resonance electrode 8
Since 5b and one surface of the ground electrode 86 are exposed to the outside and are in contact with air, the effective relative permittivity is low and radiation loss occurs,
In addition, there is a problem that it is easily affected by the external environment and its reliability is poor. Further, since the effective relative permittivity is low, it is necessary to make the dielectric block 81 large, and thus it is difficult to reduce the size of the filter.

Further, in the filter in which the triplate type stripline resonator 90 shown in FIG. 12 is combined, the effective relative permittivity is high and the degree of freedom in design is large, but the coupling between the triplate type stripline resonators 90 is large. Since the coupling is magnetic field and the degree of coupling is determined by the distance between the internal electrodes 92, there is a problem that the size is restricted by the pass band width. Further, there is a problem that the coupling is unstable and therefore the characteristics of the filter vary. In order to suppress this, a filter in which a coupling capacitor (capacitance for resonator coupling) is provided outside has been proposed. In this case, like the filter in which the coaxial dielectric resonator 60 is combined, There is a problem in that the manufacturing process is complicated and the cost is increased because it hinders the miniaturization and a shield is required at the connecting portion.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a high frequency filter which has a large degree of freedom in design, is small in size, has stable coupling, and can suppress variations in characteristics. Has a purpose.

[0012]

In order to achieve the above object, a high frequency filter according to the present invention has an outer electrode formed on the surface of a dielectric block, and the dielectric block is provided inside the dielectric block. A plurality of internal electrodes are embedded in parallel on the same plane in close contact with each other, and the internal electrodes are formed in a flat plate shape having an open end and a protruding capacitive coupling electrode portion. It is characterized (1).

External electrodes are formed on the surface of the dielectric block, and a plurality of internal electrodes are embedded in parallel inside the dielectric block in close contact with the dielectric block in the same plane. The internal electrodes, which have an open end and are formed in the shape of a flat plate, overlap each other with two or more layers sandwiching a dielectric and are electrically connected to each other at the open ends, and at least one layer of the internal electrodes has a protruding shape for capacitive coupling. It is characterized in that an electrode portion is formed (2).

External electrodes are formed on the surface of the dielectric block, and a plurality of internal electrodes are embedded in parallel in the same plane in close contact with the dielectric block. Two or more layers of the internal electrodes having an open end and formed in a flat plate are overlapped with each other with a dielectric material sandwiched therebetween, and are electrically connected to each other at one or more locations in the vicinity of the open end, and are projected on at least one layer of the internal electrodes. It is characterized in that a capacitive coupling electrode portion is formed (3).

External electrodes are formed on the surface of the dielectric block, and a plurality of internal electrodes are embedded in parallel inside the dielectric block in close contact with the dielectric block in the same plane. At least one of the internal electrodes has at least one internal electrode that has an open end and is formed in a flat plate shape, and that two or more layers of the internal electrode are overlapped with each other with a dielectric material sandwiched between them and are electrically connected to each other at two or more positions near the open end. The layer is characterized in that a projection-shaped capacitive coupling electrode portion is formed (4).

Further, in the high frequency filter described in (1), (2) and (4), the connection electrode at the open end of the internal electrode is formed on the surface of the dielectric block in addition to the external electrode. Is characterized by.

[0017]

The relationship between the dimension of the above-mentioned capacitive coupling electrode and the bandwidth was investigated. As shown in FIG. 7, the high-frequency filter used for the investigation has external electrodes 4 formed on the surface of the dielectric block 2, and the two internal electrodes are in close contact with and inside the dielectric block 2 in the same plane. The electrodes 3 are embedded in parallel, and the internal electrodes 3 are formed in a flat plate shape having open ends and projecting capacitive coupling electrodes 5. The dimension a is 1.5 mm, the dimension b is 0.375 mm, and the dimension c is 0.75 mm. The length x of the capacitive coupling electrode 5 is set to 1.5, 1.
When it is changed to 0 or 0.5 mm, as shown in FIGS.
It was possible to obtain the attenuation characteristics for frequencies as shown in (c). Further, as shown in FIG. 8D, it was found that the bandwidth at 1 dB increases substantially in proportion to the length x of the capacitive coupling electrode 5.

According to the high frequency filter of the present invention,
Since the capacitive coupling electrode is formed inside the dielectric block, the filter itself becomes small, and the capacitive coupling electrode in the form of a protrusion is formed which is stable in addition to the capacitance between the resonant electrodes. Therefore, the resonator can be stably coupled. In addition, since it is possible to change the coupling capacitance by changing the shape of the protruding capacitive coupling electrode and the coupling between the resonators can be changed, various couplings can be performed without changing the distance between the resonant electrodes. It will be possible to construct a filter having a bandwidth.

[0019]

Embodiments of the high frequency filter according to the present invention will be described below with reference to the drawings. In each of the following examples, the filter shows the case where two 1/4 wavelength resonators are coupled. 1A and 1B show a high frequency filter according to Example 1, where FIG. 1A is a front view and FIG. 1B is a sectional view taken along the line AA ′ in FIG. In the figure, 2 is a dielectric block obtained by molding a high-frequency dielectric ceramic of a high dielectric material into a substantially rectangular parallelepiped shape and sintering the same. 4 are formed. In the dielectric block 2, two internal electrodes 3 are formed side by side on the same plane, are embedded in close contact with the dielectric block 2, and one end of the internal electrode 3 is open. . The internal electrode 3 is formed in a flat plate shape, and extends from the long side corners of the internal electrode 3 so that the protruding capacitive coupling electrodes 5 face each other. Also,
The internal electrode 3 is made of Ag, Pd, Pt, Au, Cu, Co, Ni, or an alloy containing at least one of the above metals (provided that Ni, N, etc.), which has excellent processability and microwave conductivity.
i-based alloys, Co, and Co-based alloys are limited to non-magnetic materials).

In the high frequency filter 11 according to the first embodiment having such a structure, a stable coupling capacitance is formed between the capacitive coupling electrodes 5 in addition to the capacitance between the internal electrodes 3 serving as the resonance electrodes. Thus, stable coupling of the resonator 10 and miniaturization of the high frequency filter can be achieved. In addition, since the coupling capacitance is changed by changing the shape of the protruding capacitive coupling electrode 5, and thus the coupling between the resonators 10 is changed, it is possible to change the distance between the internal electrodes 3 serving as the resonant electrodes. It is possible to construct filters having various bandwidths.

2A and 2B show a high frequency filter according to a second embodiment. FIG. 2A is a front view and FIG. 2B is a sectional view taken along the line AA 'in FIG. Reference numeral 2 in the drawing denotes a dielectric block formed in the same manner as in the first embodiment, and external electrodes 4 are formed on the other five surfaces except one side surface of the dielectric block 2. Inside the dielectric block 2, there are three layers of internal electrodes 3 which are overlapped with each other with the dielectric portion 6 sandwiched therebetween and are arranged on the same plane.
They are formed side by side and are embedded in close contact with the dielectric block 2 and the dielectric portion 6, respectively, and one open end of the internal electrode 3 is electrically connected by the connection electrode 7. The internal electrodes 3 are formed in a flat plate shape using the same metal or alloy as in the case of the first embodiment, and further, similarly to the case of the first embodiment, the projecting capacitive coupling electrodes 5 face each other. It extends from the long side corner of the internal electrode 3.

In the high frequency filter 21 according to the second embodiment having such a configuration, the internal electrode 3 as the resonance electrode is used.
Since there are three layers and they are electrically connected and operate like an electrode of one layer, the resistance of the internal electrode 3 becomes low and the Q value of the resonator 20 can be increased. Example 1
As in the case of (1), stable coupling of the resonator 20 and miniaturization of the high frequency filter can be achieved, and the filter having various bandwidths can be used without changing the distance between the internal electrodes 3 serving as the resonance electrodes. Configuration is possible.

In addition, the protruding capacitive coupling electrode 5 in the second embodiment is formed on each of the three layers of internal electrodes 3. However, since the three layers of internal electrode 3 are electrically connected, Electrode 5 for capacitive coupling to internal electrode 3 of one layer or two layers
In the case of the formation, the same effect as that of the second embodiment is obtained.

3A and 3B show a high frequency filter according to the third embodiment. FIG. 3A is a front view and FIG. 3B is a sectional view taken along the line AA 'in FIG. Reference numeral 2 in the drawing denotes a dielectric block formed in the same manner as in the first embodiment, and external electrodes 4 are formed on the other five surfaces except one side surface of the dielectric block 2. Inside the dielectric block 2, there are three layers of internal electrodes 3 which are overlapped with each other with the dielectric portion 9 sandwiched therebetween, and are arranged on the same plane.
They are formed side by side, are buried in close contact with the dielectric block 2 and the dielectric portion 9, respectively, and the vicinity of the open end of the internal electrode 3 is electrically connected by the connection electrode 8. The internal electrode 3 is formed in a flat plate shape using the same metal or alloy as in the case of the first embodiment, and further, similarly to the case of the first embodiment, the projecting capacitive coupling electrodes 5 face each other. It extends from the long side corner of the internal electrode 3.

The high frequency filter 31 according to the third embodiment thus configured has substantially the same effect as that of the second embodiment.

In addition, the protruding capacitive coupling electrode 5 in the third embodiment is formed on each of the three layers of internal electrodes 3. However, since the three layers of internal electrodes 3 are electrically connected, Electrode 5 for capacitive coupling to internal electrode 3 of one layer or two layers
In the case of the formation, the same effect as that of the third embodiment is obtained.

4A and 4B show a high frequency filter according to the fourth embodiment. FIG. 4A is a front view and FIG. 4B is a sectional view taken along the line AA 'in FIG. Reference numeral 2 in the drawing denotes a dielectric block formed in the same manner as in the first embodiment, and external electrodes 4 are formed on the other five surfaces except one side surface of the dielectric block 2. A dielectric portion 12 is provided in the dielectric block 2.
Two internal electrodes 3 of three layers that are overlapped with each other sandwiched between are formed side by side on the same surface, and are embedded in close contact with the dielectric block 2 and the dielectric portion 12, respectively, and one of the internal electrodes 3 Connection electrode 1 at open end and near open end
4 and 13 electrically connect. The internal electrode 3 is formed in a flat plate shape using the same metal or alloy as in the case of the first embodiment, and further, similarly to the case of the first embodiment, the projecting capacitive coupling electrodes 5 face each other. It extends from the long side corner of the internal electrode 3.

In the high frequency filter 41 according to the fourth embodiment thus configured, in addition to the effect of the second embodiment, the electrical connection between the internal electrodes 3 becomes more reliable,
Therefore, the resistance in the internal electrode 3 becomes low and the resonator 4
The Q value of 0 can be further increased.

In addition, the protruding capacitive coupling electrode 5 in the fourth embodiment is formed on each of the three layers of internal electrodes 3. However, since the three layers of internal electrode 3 are electrically connected, Electrode 5 for capacitive coupling to internal electrode 3 of one layer or two layers
In the case of the formation, the same effect as that of the fourth embodiment is obtained.

5A and 5B show a high frequency filter according to the fifth embodiment. FIG. 5A is a front view and FIG. 5B is a sectional view taken along the line AA 'in FIG. Reference numeral 2 in the drawing denotes a dielectric block formed in the same manner as in the first embodiment, and external electrodes 4 are formed on the other five surfaces except one side surface of the dielectric block 2. A dielectric portion 16 is provided in the dielectric block 2.
Two internal electrodes 3 of three layers that are overlapped with each other sandwiched between are formed side by side on the same plane, and are embedded in close contact with the dielectric block 2 and the dielectric portion 16, respectively, and one of the internal electrodes 3 The open end is electrically connected to the surface of the dielectric block 2 by the connection electrode 17. Internal electrode 3
Is formed in a flat plate shape using the same metal or alloy as in the case of Example 1, and further, as in the case of Example 1,
The protruding capacitive coupling electrodes 5 are extended from the long side corners of the internal electrodes 3 so as to face each other.

In the high frequency filter 51 according to the fifth embodiment thus configured, in addition to the effect obtained in the second embodiment, the connection electrode 17 is formed on the surface of the dielectric block 2, so that the connection electrode 17 is formed. Can be formed simultaneously with the external electrode 4, and the manufacturing process can be simplified. The connection electrode 17 can also be used as an input / output electrode of the resonator 50.

In addition, the protruding capacitive coupling electrode 5 in the fifth embodiment is formed on each of the three layers of internal electrodes 3. However, since the three layers of internal electrode 3 are electrically connected, Electrode 5 for capacitive coupling to internal electrode 3 of one layer or two layers
In the case of the formation, the same effect as that of the fifth embodiment is obtained.

FIG. 6 is a graph showing the results of investigating the attenuation characteristics with respect to frequency of the high frequency filter 51 in the fifth embodiment, in which the vertical axis represents the attenuation amount (dB) and the horizontal axis represents the frequency (MHz). There is. As is apparent from the figure, the high frequency filter 51 has excellent characteristics as a bandpass filter having a pass band of about 881.5 MHz.

[0034]

As described above in detail, in the high frequency filter according to the present invention, the coupling between the high frequency resonators is performed by the protruding capacitive coupling electrode formed on the internal electrode. The coupling can be made stable, and the high frequency filter can be downsized. Further, the coupling capacitance can be changed by changing the shape of the protruding capacitive coupling electrode, and filters having various bandwidths can be configured without changing the distance between the high frequency resonators. ..

Further, when the internal electrodes are overlapped with each other with two or more layers sandwiching the dielectric portion and these internal electrodes are electrically connected, the resistance of the internal electrodes becomes low and the high frequency resonator has The Q value can be increased.

Further, when the open ends of the internal electrodes and the vicinity of the open ends, which are overlapped by two or more layers sandwiching the dielectric part, are electrically connected to each other, respectively,
The electrical connection between the internal electrodes becomes more reliable, and therefore the resistance at the internal electrodes becomes lower, and the Q value of the resonator can be further increased.

Further, when the connection electrode is formed on the surface of the dielectric block, the connection electrode can be formed at the same time as the external electrode, and the manufacturing process can be simplified. Further, the connection electrode can be used as an input / output electrode of the resonator. Therefore, the manufacturing cost of the high frequency filter can be reduced.

[Brief description of drawings]

1A and 1B show a high frequency filter according to a first embodiment of the present invention, in which FIG. 1A is a front view and FIG. 1B is a sectional view taken along the line AA ′ in FIG.

FIG. 2 shows a high frequency filter according to a second embodiment,
(A) is a front view, (b) is a sectional view taken along the line AA 'in (a).

FIG. 3 shows a high frequency filter according to a third embodiment,
(A) is a front view, (b) is a sectional view taken along the line AA 'in (a).

FIG. 4 shows a high frequency filter according to Example 4,
(A) is a front view, (b) is a sectional view taken along the line AA 'in (a).

FIG. 5 shows a high frequency filter according to a fifth embodiment,
(A) is a front view, (b) is a sectional view taken along the line AA 'in (a).

FIG. 6 is a graph showing the results of examining the attenuation characteristic with respect to frequency of the high frequency filter of Example 5;

FIG. 7 is a front view of a high-frequency filter used when investigating the relationship between the dimension of the capacitive coupling electrode and the bandwidth.

FIG. 8 shows the results of examining the relationship between the dimension of the capacitive coupling electrode and the bandwidth, (a), (b), and (c) are graphs showing attenuation characteristics with respect to frequency, and (d) is a graph showing these. It is the graph which summarized the result.

FIG. 9 shows a filter in which a coaxial dielectric resonator that has been conventionally used is combined, (a) is a front view,
(B) is a plan view

10A and 10B show a dielectric block integrated type filter which has been conventionally used, in which FIG. 10A is a perspective view and FIG.
6 is a sectional view taken along line YY ′ in FIG.

FIG. 11 is a perspective view showing a filter combined with a conventionally used microstrip line resonator.

FIG. 12 is a perspective view showing a filter combined with a conventionally used triplate-type stripline resonator.

[Explanation of symbols]

 2 Dielectric block 3 Internal electrode 4 External electrode 5 Capacitive coupling electrode 11, 21, 31, 41, 51 High frequency filter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Kikuyama 1-3-1 Otemachi, Chiyoda-ku, Tokyo Sumitomo Metal Industries, Ltd.

Claims (5)

[Claims] 1. An external electrode is formed on the surface of a dielectric block, and a plurality of internal electrodes are embedded in parallel in the same plane in close contact with the dielectric block inside the dielectric block. A high frequency filter characterized in that the internal electrode is formed in a flat plate shape having an open end and a protruding capacitive coupling electrode portion. 2. An external electrode is formed on the surface of the dielectric block, and a plurality of internal electrodes are embedded in parallel in the same plane inside the dielectric block in close contact with the dielectric block. The internal electrodes, which have an open end and are formed in the shape of a flat plate, overlap each other with two or more layers sandwiching a dielectric and are electrically connected to each other at the open ends, and at least one layer of the internal electrodes has a protruding shape for capacitive coupling. A high-frequency filter characterized in that an electrode portion is formed. 3. An external electrode is formed on the surface of the dielectric block, and a plurality of internal electrodes are embedded in parallel inside the dielectric block in close contact with the dielectric block in the same plane. The internal electrodes, which have an open end and are formed in a flat plate shape, overlap each other with two or more layers sandwiching a dielectric, and are electrically connected at one or more places near the open end, respectively.
A high-frequency filter, wherein a protruding capacitive coupling electrode portion is formed on at least one layer of the internal electrode. 4. An external electrode is formed on the surface of the dielectric block, and a plurality of internal electrodes are embedded in parallel inside the dielectric block in close contact with the dielectric block in the same plane. At least one of the internal electrodes has at least one internal electrode that has an open end and is formed in a flat plate shape, and that two or more layers of the internal electrode are overlapped with each other with a dielectric material sandwiched between them and are electrically connected to each other at two or more positions near the open end. A high-frequency filter characterized in that a projection-shaped capacitive coupling electrode portion is formed on the layer. 5. The high frequency filter according to claim 1, wherein a connection electrode at the open end of the internal electrode is formed on the surface of the dielectric block in addition to the external electrode.