JPH09167901A - Laminated dielectric filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated dielectric filter which is capable of surely suppressing the dispersion of the characteristics of positional deviation. SOLUTION: This filter is composed of the laminated body of plural dielectric layers including the first dielectric layer 10 in which at least two resonance electrodes 11 and 12 composing a strip line type resonator are formed and the second dielectric layer 20 in which the input/output electrodes 21 and 22 to be coupled with the resonance electrodes 11 and 12 are formed. At this time, at the opening end side end parts of the two resonance electrodes 11 and 12 of the first dielectric layer 10, an internal earth electrode 13 which is opposed to the opening ends of the two resonance electrodes 11 and 12 with a prescribed gap and is composed with an external earth electrode is arranged as the continuous pattern covering the ranges of the two resonance electrodes 11 and 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated dielectric filter which is useful when applied to a high frequency filter mounted on a mobile phone or the like.

[0002]

2. Description of the Related Art As a small-sized high frequency filter used in a frequency band of several MHz to several GHz, a laminated dielectric filter made by a green sheet method and having a plurality of dielectric layers formed with a predetermined electrode pattern is laminated. It has been known. FIG. 5 is an exploded perspective view of a conventional laminated dielectric filter. A dielectric layer 10 having resonance electrodes 11 and 12 forming a stripline resonator and input / output electrodes 21 and 22 respectively coupled to the resonance electrodes 11 and 12 are formed in the middle of the dielectric laminated structure. Having a dielectric layer 20. A dielectric layer 30 having an external ground electrode 50 formed thereon is laminated on the dielectric layer 20, and a coupling electrode 41 for coupling the resonance electrodes 11 and 12 is formed on the upper surface below the dielectric layer 10. And a dielectric layer 40 on which the external ground electrode 50 is formed.

Although not shown in FIG. 5, external input / output electrodes connected to the input / output electrodes 21 and 22 are formed on the side surfaces of the dielectric laminated structure, and regions other than the external input / output electrodes are formed. An external earth electrode is formed so as to cover all of them and to connect one ends of the resonance electrodes 11 and 12 and to be continuous with the upper and lower external earth electrodes 50. The electrodes 61 and 71 shown on the uppermost surface of FIG. 5 are the input / output electrodes 21 and 21 on the dielectric layer 20 via the external input / output electrodes on the side surface not shown in the figure.
Connected to 22.

With such a laminated structure, the resonance electrode 11,
12 and the dielectric layer 10 constitute two LC resonance circuits, each of which is composed of a distributed constant circuit. The coupling electrodes 41 capacitively couple these resonance circuits, and the input / output electrodes 21 and 22 are capacitively coupled to the resonance electrodes 11 and 12. Combined to form a bandpass filter.

When such a laminated dielectric filter is produced by, for example, the green sheet method, printing of an electrode pattern,
When the positional displacement of the electrodes embedded inside occurs in the steps such as crimping and cutting, the filter characteristics change due to changes in the resonator length and the additional capacitance value. One of the major causes of this characteristic change is a change in capacitance between the resonance electrodes 11 and 12 with respect to ground. That is, as shown in FIG. 6, the resonance electrodes 11 and 12 have open ends with a predetermined gap g with respect to the external ground electrode 50.
With a predetermined capacitance between the ground and C1 and C2.
Is configured. Therefore, when the gap g changes in the manufacturing process, the capacitors C1 and C2 also change, which has a great influence on the center frequency of the filter.

FIG. 7 shows an example of filter center frequency fluctuation due to the above-mentioned fluctuation of the gap g. Gap g
When becomes smaller, the capacitance to ground of the resonance electrode increases, and the center frequency decreases. As is clear from the figure, this tendency becomes more remarkable as the gap g becomes smaller. Therefore,
As the filter is made smaller, the variation of the gap g due to the positional deviation in the stacking process has a great influence on the filter characteristics. This gap variation affects not only the center frequency but also the coupling strength between the resonators, and causes variation in the pass bandwidth.

As a structure for reducing the variation in characteristics due to the variation in the distance between the resonance electrode and the external ground electrode on the side surface, as shown in FIG. 8, on the same surface as the resonance electrodes 11 and 12 and at the open ends thereof. Opposing internal earth electrode 1
Providing 8 and 19 has been proposed (see, for example, Japanese Patent Laid-Open No. 5-243810). Resonant electrode 11,1
The gap between 2 and the internal ground electrodes 18 and 19 is determined in the printing process and does not change in the subsequent laminating process or cutting process, so that it is possible to reduce the above-mentioned characteristic variation due to the positional deviation to some extent. .

[0008]

However, in the structure shown in FIG. 8, since the separate internal ground electrodes 18 and 19 are arranged so as to face only the open ends of the resonance electrodes 11 and 12, respectively, the position of The effects of misalignment are not completely eliminated. That is, in the structure of FIG. 8, electric field radiation from the edge portions of the resonance electrodes 11 and 12 to the external earth electrode 50 is unavoidable.
The influence of the external ground electrode 50 cannot be completely suppressed, and the center frequency and the bandwidth vary due to the position shift.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a laminated dielectric filter capable of reliably suppressing characteristic variations due to positional deviation.

[0010]

The present invention is directed to a dielectric layer having n (n is an integer of 2 or more) resonance electrodes forming a stripline resonator and an input for coupling to the resonance electrodes. An external earth electrode, which is composed of a laminated body of a plurality of dielectric layers including a dielectric layer on which an output electrode is formed, and the ground end of the resonance electrode is connected to the outer surface of the laminated body, and the input / output electrode, respectively. In the laminated dielectric filter having external input / output electrodes connected thereto, the n-number of resonance electrodes are formed at the end of the dielectric layer having the n-number of resonance electrodes on the open end side. The internal ground electrode facing the open end of the resonance electrode with a predetermined gap is arranged as a continuous pattern covering the array region of the two resonance electrodes.

In the present invention, preferably, the internal ground electrode has a continuous pattern having a bent portion facing the open ends of the n resonance electrodes and also facing the side surfaces of the resonance electrodes near the open ends.

According to the present invention, n embedded in the inside
With respect to the two resonance electrodes, the internal ground electrodes facing the open ends of the resonance electrodes are arranged not as each resonance electrode but as one continuous pattern that covers the area where the n resonance electrodes are arranged. By installing this, the electric field from the edge of the resonance electrode is concentrated on the internal ground electrode, and direct coupling with the external ground electrode is surely suppressed, and most of the capacitance between the ground and the resonance electrode is It is formed between the ground electrode. Therefore, the variation in the filter characteristics due to the positional deviation caused in the manufacturing process is effectively reduced. Furthermore, the internal ground electrode is formed into a continuous pattern having a bent portion so as to face not only the resonance electrode open end but also the resonance electrode side surface near the open end, in other words, the resonance electrode tip is three-way. By forming the U-shape so as to be surrounded by, the coupling of the resonance electrode tip portion with the external ground electrode can be more reliably suppressed.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an exploded perspective view of a laminated dielectric filter according to an embodiment of the present invention, and FIG. 2 is an external perspective view. The parts corresponding to those of the conventional structure shown in FIG. 5 are designated by the same reference numerals as those in FIG.

On the surface of the inner first dielectric layer 10, two parallel resonant electrodes 11 and 12 for forming a quarter-wave stripline resonator in this embodiment are formed. ing. The ground ends of the resonance electrodes 11 and 12 are arranged up to one end of the first dielectric layer 10, and are connected to an external ground electrode 50 formed on the side surface after lamination as shown in FIG. At the end portions of the resonance electrodes 11 and 12 of the first dielectric layer 10 on the open end side, the internal ground electrode 13 having a rectangular pattern continuous over the entire range of the width w of the first dielectric layer 10.
Are arranged. The internal ground electrode 13 is the resonance electrode 1
It faces 1 and 12 with a predetermined gap g0.
The internal ground electrode 13 is also connected to the external ground electrode 50 formed on the side surface.

Input / output electrodes 21 and 22 that are capacitively coupled to the resonance electrodes 11 and 12 are formed on the upper surface of the second dielectric layer 20 that overlaps the first dielectric layer 10. These input / output electrodes 21 and 22 are respectively connected to external input / output electrodes 60 and 70 formed on the side surfaces as shown in FIG.

The dielectric layer 40 below the first dielectric layer 10 is provided with a coupling electrode 41 for capacitively coupling the resonance electrodes 11 and 12 on the upper surface, and at the tips of the resonance electrodes 11 and 12. Additional capacitance electrode 4 for adding capacitance to ground
2 and 43 are formed so as to overlap the tip ends of the resonance electrodes 11 and 12, respectively. An external ground electrode 50 is formed on the entire lower surface of the dielectric layer 40.

An external earth electrode 50 and electrodes 61 and 71 which are a part of external input / output electrodes are formed on the upper surface of the dielectric layer 30 which overlaps the second dielectric layer 20. That is, the electrodes 61 and 71 are connected to the external input / output electrodes 60 and 70 formed on the side surfaces as shown in FIG.

When the dielectric filter of this embodiment is specifically manufactured by the green sheet method, each dielectric layer 10,
20, 30 and 40 are stacked with a required number of sheets in accordance with the filter characteristics to be designed in consideration of the dielectric constant of the ceramic material used. Then, after forming the ceramic laminated body in which the above-mentioned respective electrodes are embedded, the external ground electrode 50, the external input / output electrodes 60, 70, etc. are formed on the side surface by printing, firing, etc. of silver paste.

FIG. 3 shows an equivalent circuit of the laminated dielectric filter according to this embodiment. The two resonance electrodes 11 and 12 form distributed parallel LC parallel resonance circuits 1 and 2, respectively. Between the two resonance circuits 1 and 2, the coupling capacitance C22 mainly determined by the electrostatic capacitance between the two resonance circuits 1 and 2.
And the mutual inductance M determined by the inductance of the coupling electrode 41. Input / output terminal IN, OU
Capacitances C21 and C23 of T are capacitances between the input / output electrodes 21 and 22 and the resonance electrodes 11 and 12. The capacitances C31 and C32 to the ground at the open end of the resonator are determined by the capacitance between the tips of the resonance electrodes 11 and 12 and the internal ground electrode 13 in the same plane, and between the additional capacitance electrodes 42 and 43 in the lower layer. .

As described above, in this embodiment, the internal ground electrode facing the open ends of the resonance electrodes 11 and 12 has a continuous pattern across the surface of the dielectric layer 10 on which the resonance electrodes 11 and 12 are formed. 13 is formed. Therefore, unlike the structure shown in FIG. 8 in which the internal electrodes are separately provided to face the resonance electrodes 11 and 12, respectively,
Since the connection with the external earth electrode due to the edge effect of 12 is almost completely eliminated, the capacitance between the resonance electrodes 11 and 12 with respect to the ground, that is, the capacitance shown in FIG. There is almost no variation in C31 and C32. This ensures that the center frequency and bandwidth of the filter are prevented from fluctuating. The capacitances C31 and C32 to the ground of the resonance electrodes 11 and 12 are formed between the resonance electrodes 11 and 12 and the internal ground electrode 13, and between the underlying additional capacitance electrodes 42 and 43, and the external ground electrode 50. Since there is no influence of, the overall size of the filter can be reduced.

In the embodiment shown in FIG. 1, the internal earth electrode 1
Although 3 is a continuous pattern over the entire width of the first dielectric layer 10, the internal ground electrode 13 can prevent direct coupling between the resonance electrodes 11 and 12 and the external ground electrode in consideration of the edge effect. Any length will do. Therefore, FIG.
As shown in (a), if the internal ground electrode 13 is formed in a continuous pattern so as to cover the area where at least two resonant electrodes 11 and 12 are arranged, a sufficient effect can be obtained.

FIG. 4B shows a more preferable internal ground electrode pattern. In this example, bent portions 14a and 14b facing the side surfaces of the tip portions of the resonance electrodes 11 and 12 are continuously formed on the internal ground electrode 13 which crosses the width direction shown in FIG. The internal earth electrode 13 is formed as a U-shaped bending pattern like this and the resonance electrodes 11, 1
By surrounding the open end tip portion of 2 from the three sides, the influence of the positional deviation in the left-right direction in the drawing is surely suppressed. In particular, this structure is designed to reduce the size of the entire filter by using the resonance electrode 1
This is effective when the distance between the side surfaces of Nos. 1 and 12 and the external ground electrode becomes small.

FIG. 4 (c) shows an internal ground electrode similar to that of FIG. 4 (b) when a pattern having step portions 15 and 16 with wide widths at the open ends is used as the resonance electrodes 11 and 12. This is an example of using a pattern. The resonance electrodes 11 and 12 having the step portions 15 and 16 as shown are used when the capacitance is increased and the resonance electrode length is reduced accordingly. In this case, since the distance between the side surfaces of the resonance electrodes 11 and 12 and the external ground electrode becomes smaller, the conventional structure is greatly affected by the positional deviation. However, as in this embodiment, the steps 15 and 16 are opposed to each other. Bent part 14
By using the internal ground electrode 13 provided with a and 14b, the characteristic variation can be effectively reduced.

FIG. 4D shows an example in which convex portions 17a and 17b are pattern-formed on the portion of the internal ground electrode 13 facing the resonance electrodes 11 and 12. Even if such an internal ground electrode pattern is used, the influence of the external ground electrode can be avoided as in the above embodiment.

The present invention is not limited to the above embodiment. For example, in the embodiment, the input / output electrodes 21 and 22 are formed on the same dielectric layer, but the input electrode 21 and the output electrode 22 are formed on the resonant electrode 1.
It is also possible to adopt a structure in which the dielectric layers disposed above and below the dielectric layer on which 1 and 12 are formed are separately provided. Further, the present invention is similarly applied to the case where the coupling electrode 41 and the additional capacitance electrodes 42 and 43 are not used, or when the dielectric layers having the resonance electrodes 11 and 12 are arranged above and below the dielectric layer. Can be applied. Furthermore, although the embodiment has been described with reference to the case of having two resonance electrodes, the present invention can be similarly applied to a filter having three or more resonance electrodes.

[0026]

As described above, according to the present invention, with respect to the n resonance electrodes embedded inside, the internal ground electrodes facing the open ends of the resonance electrodes are not provided for each resonance electrode, but for each resonance electrode. By arranging them as one continuous pattern that covers the range of the n resonance electrodes, direct coupling with the external ground electrode is surely suppressed, and therefore occurs in the manufacturing process of the laminated dielectric filter. Variations in filter characteristics due to positional deviation are effectively reduced.

[Brief description of the drawings]

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

FIG. 2 is an external perspective view of the embodiment.

FIG. 3 is an equivalent circuit of the filter of the example.

FIG. 4 is an internal ground electrode pattern of another embodiment.

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

FIG. 6 is a resonance electrode pattern of the conventional example.

FIG. 7 is a characteristic diagram showing the dependence of the center frequency of the conventional example on the gap at the open end side of the resonance electrode.

FIG. 8 shows another conventional internal ground electrode pattern.

[Explanation of symbols]

10 ... 1st dielectric material layer, 11, 12 ... Resonant electrode, 13 ...
Internal ground electrode, 20 ... Second dielectric layer, 21, 22 ...
Input / output electrodes, 30, 40 ... Dielectric layer, 50 ... External ground electrode, 60, 61, 70, 71 ... External input / output electrode, 14
a, 14b ... Bent part.

Front page continued (72) Inventor Koichi Fukuda 5 1978, Koujigushi, Ube City, Ube Yamaguchi Prefecture 5 Ube Kosan Co., Ltd. Ube Laboratory

Claims (2)

[Claims] 1. An n constituting a stripline resonator.
It is composed of a laminated body of a plurality of dielectric layers including a dielectric layer in which (n is an integer of 2 or more) resonant electrodes are formed, and a dielectric layer in which input / output electrodes coupled to the resonant electrodes are formed. A multilayer dielectric filter in which an external ground electrode to which a ground end of the resonance electrode is connected and an external input / output electrode to which the input / output electrode is respectively connected are formed on an outer surface of the multilayer body, An internal ground electrode facing the open ends of the n resonance electrodes with a predetermined gap is provided at the open ends of the n resonance electrodes of the dielectric layer on which the resonance electrodes are formed.
A laminated dielectric filter, which is arranged as a continuous pattern covering an array region of the n resonance electrodes. 2. The internal ground electrode has a continuous pattern having a bent portion that faces the open ends of the n resonance electrodes and also faces the side surfaces of the resonance electrodes near the open ends. Item 1. A laminated dielectric filter according to item 1.