JPH0969701A - filter - Google Patents

Abstract

(57) An object of the present invention is to provide a low-loss filter using a quarter-wave resonator that can be downsized and whose Q value is small even when downsized. SOLUTION: Substrates 2A to 2L are laminated to form a laminated body 2. Resonant electrodes 4A and 4B each having a bent shape and formed of straight line portions 4Aa to 4Ae and 4Ba to 4Be are formed on the laminated surface of the laminated body 2. Resonance electrodes 4A, 4
The coupling control electrode 11 is formed on the laminated surface between B.
A shield electrode 6 is formed on the laminated body 2. One end of each of the resonance electrodes 4A and 4B extends to the end surface of the laminated body 2 and is connected to the shield electrode 6. Input / output electrodes 8A and 8B are formed on the end faces of the laminated body 2. Input / output connecting portions 10A, 10B for electrically connecting the resonance electrodes 4A, 4B and the input / output electrodes 8A, 8B are formed on the stacking surface of the stack 2. The resonance electrodes 4A and 4B have an effective electrode length within a range of 0.90 to 0.94 times the center line length.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to several hundred MHz to several G.
The present invention relates to a filter technology in the frequency region of Hz, and particularly relates to a filter in which a plurality of quarter-wavelength resonant electrodes are arranged on different laminated surfaces of laminated dielectrics.

[0002]

2. Description of the Related Art
As a bandpass filter used in a frequency range of several hundred MHz to several GHz, a plurality of through holes parallel to a dielectric block are formed, and a through hole inner surface of the dielectric block and a direction along the through hole are formed. A connection conductor is formed by applying a conductor to the outer side surface to form an inner conductor and an outer conductor, respectively, and connecting the inner conductor and the outer conductor to one of the two end faces of the dielectric block in which the through holes are opened. A coaxial resonator formed is used.

Further, in recent years, a stripline type 1/4 wavelength resonator as shown in FIG. 5 has been used for further miniaturization and simplification of the configuration. (See JP-A-7-46003). In FIG. 5, reference numeral 12 is a dielectric substrate, and the first principal surface (upper surface) thereof has two resonant electrodes 14 of length L.
A and 14B are formed in parallel, and the ground electrode 16 is formed over a part of the first main surface and one end surface of the dielectric substrate 12 and the entire second main surface (lower surface). The resonance electrode 14 is formed on the first main surface of the dielectric substrate 12.
Input / output electrodes 18A and 1 connected to A and 14B, respectively
8B is formed. Thus, the two resonant electrodes 14
A filter using electromagnetic coupling of two quarter-wave resonators including A and 14B is formed.

In this quarter wavelength resonator, the length L of the resonance electrodes 14A and 14B is L = (1) where λ is the wavelength of the electromagnetic wave used and ε is the effective dielectric constant of the dielectric substrate 12. / 4) λ (1 / ε ^1/2 ). Therefore, the frequency ω of the electromagnetic wave is several hundred MHz
In the case of several GHz, the electrode length L becomes considerably long. For example, in the case of ε = 70 and ω = 800 MHz, L = 1.
It becomes 1.2 mm.

Therefore, in order to further reduce the size of the filter, the resonance electrode of the stripline type resonator is bent into a spiral shape in order to reduce the size of the resonator.
It has been proposed to reduce the size (especially length) of the dielectric substrate (see Japanese Patent Laid-Open No. 7-46003). That is, as shown in FIG. 6, the dielectric substrate 12
The resonance electrode 14A formed on the first main surface of the
4Aa to 12Af in a spiral shape, and similarly, although not shown, the resonance electrode 14B is also formed in a spiral shape including a plurality of straight line portions so that the total length of the straight line portions of each resonator is equal to the resonance electrode. The length can be obtained, and the length of the dielectric substrate 12 can be reduced to the same extent as that of the longest straight line portion 14Aa, etc. Thus, even when the above L is long, the size of the entire resonator and thus the entire filter can be reduced. Does not increase the size so much.

However, when such a spiral-shaped resonance electrode is used, when the distance between the adjacent parallel portions of the spiral becomes small, especially between these adjacent portions (for example, the straight line portion 14Aa and the straight line portion in FIG. 6). 14Ae
Between and between the straight line portion 14Ab and the straight line portion 14Af) affect the flow of current in the resonance electrode 14A and the like, which substantially increases the resistance and reduces the resonance Q value. The problem of doing so arises. This increases the loss in filter characteristics.

Therefore, an object of the present invention is to provide a filter using a quarter-wave resonator which can be miniaturized and whose Q value is less likely to decrease even when miniaturized.

A further object of the present invention is to provide a filter with low loss.

[0009]

According to the present invention, in order to achieve the above object, a plurality of dielectric substrates are laminated to form a substrate laminate, and the substrate laminates are different from each other. A plurality of resonance electrodes are formed on the laminated surface, the resonance electrode has a shape bent at least once, and shield electrodes are formed on two main surfaces and end surfaces of the substrate laminated body. One end of the resonance electrode extends to the end face of the substrate laminate and is connected to the shield electrode, and first and second input / output electrodes are formed at different positions on the end face of the substrate laminate. The uppermost layer and the lowermost layer of the laminated surface of the substrate laminated body on which the resonance electrodes are formed respectively include a portion separated from the one end of the resonance electrodes and the first and second input / output electrodes. Connect electrically 1st and 2nd input / output connection parts are formed, and it is a lamination | stacking surface different from the lamination | stacking surface in which the said resonance electrode of the said board | substrate laminated body is formed, and between the adjacent ones of this some resonance electrode. A coupling control electrode is formed on each one of the stacked surfaces, and the resonance electrode has an effective electrode length within a range of 0.90 to 0.94 times the center line length. A filter is provided.

In one aspect of the present invention, the bending of the resonance electrode is performed in the same direction and at a right angle when proceeding from the one end to the other end.

In one aspect of the present invention, the number of bends of the resonance electrode is 2 to 5.

In one aspect of the present invention, the resonator having the resonance electrode has a Q value within a range of 70 to 100% of a Q value of a linear resonance electrode having the same center line length and no bending.
Has a value.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an exploded perspective view showing an embodiment of a filter according to the present invention, and FIG. 2 is a perspective view of its assembled state. 1 and 2, 2A, 2B, 2C,
2D, 2E, 2F, 2G, 2H, 2I, 2J, 2K, 2
L is a dielectric substrate, and the materials thereof may be the same, for example, a ceramic dielectric having an effective dielectric constant of 90. The upper surface of each of these substrates is the first main surface and the lower surface is the second main surface. These 12 dielectric substrates 2A to 2
The L is laminated to form the substrate laminate 2.

A film-shaped resonance electrode 4A is formed on the upper surface of the dielectric substrate 2C. The resonance electrode 4A has a bent spiral shape, and has a plurality of straight line portions 4Aa, 4A.
It consists of Ab, 4Ac, 4Ad, 4Ae, and the straight line portion 4A
a and 4Ab form a right angle with each other, and the straight line portion 4A
b and 4Ac form a right angle with each other, and the straight line portion 4A
c and 4Ad form a right angle with each other, and the straight line portion 4A
d and 4Ae are perpendicular to each other. This resonance electrode 4
The bend of A is made so as to form a right angle in the same direction (to the right) when going from the straight line portion 4Aa to 4Ae. One end of the linear portion 4Aa (end portion on the side opposite to the connection side with the linear portion 4Ab) extends to the end surface of the dielectric substrate 2C.

A film-shaped resonance electrode 4B is formed on the upper surface of the dielectric substrate 2I. The resonance electrode 4B has a bent spiral shape and has a plurality of straight line portions 4Ba, 4B.
It consists of Bb, 4Bc, 4Bd and 4Be, and the straight line portion 4B
a and 4Bb form a right angle with each other, and the straight line portion 4B
b and 4Bc form a right angle with each other, and the straight line portion 4B
c and 4Bd form a right angle with each other, and the straight line portion 4B
d and 4Be form a right angle with each other. This resonance electrode 4
The bending of B is made so as to make a right angle in the same direction (to the left) when going from the straight portion 4Ba to 4Be. One end of the linear portion 4Ba (the end opposite to the side connected to the linear portion 4Bb) extends to the end surface of the dielectric substrate 2I.

A film-shaped coupling control electrode 11 is formed on the upper surface of the dielectric substrate 2F. The coupling control electrode 11 is present between the resonance electrode 4A and the resonance electrode 4B,
It controls the electromagnetic coupling of these two resonant electrodes.

A film-like shield electrode 6 is formed on almost the entire upper surface of the dielectric substrate 2L, and although not shown in the figure, the shield electrode 6 on the upper surface of the dielectric substrate 2L is also formed on the lower surface of the dielectric substrate 2A. Corresponding to, a film-shaped shield electrode is formed on almost the entire surface. Two inputs / outputs are provided for a part of the upper surface and a part of the end surface of the dielectric substrate 2L, a part of the lower surface and a part of the end surface of the dielectric substrate 2A, and a part of the end surface of the dielectric substrates 2B to 2K. Electrodes 8A and 8B are formed. Then, on most of the end surfaces of the dielectric substrates 2A to 2L, the film-like shield electrode 6 except the input / output electrodes 8A and 8B and the vicinity thereof.
Are formed. That is, in the substrate laminate 2, the entire exposed surface is covered with the film-shaped shield electrode 6 except for the input / output electrodes 8A and 8B and the vicinity thereof. One end of the linear portion 4Aa of the resonance electrode 4A is connected to the shield electrode 6 at the end face of the substrate laminate 2, and one end of the linear portion 4Ba of the resonance electrode 4B is shielded at the end face of the substrate laminate 2. It is connected to the electrode 6.

The resonance electrode 4A is formed on the upper surface of the dielectric substrate 2C.
An input / output connection portion 10A made of a conductor film is formed to connect the input / output electrode 8A with a position separated from the connection portion of the straight line portion 4Aa with the shield electrode 6 by an appropriate distance DA. Straight line portion 4Aa and input / output connection portion 10A
And may be capacitively coupled at intervals even if they are not directly connected.

The resonance electrode 4B is formed on the upper surface of the dielectric substrate 2I.
An input / output connecting portion 10B made of a conductor film for connecting the input / output electrode 8B and a position separated by an appropriate distance DB from the connecting portion of the straight line portion 4Ba with the shield electrode 6 is formed. Straight line portion 4Ba and input / output connection portion 10B
And may be capacitively coupled at intervals even if they are not directly connected.

As shown in the drawing, the coupling control electrode 11 on the upper surface of the dielectric substrate 2F has a part of the substrate laminated body 2 described above.
Is connected to the shield electrode 6 at the end face thereof. By doing so, it is possible to prevent the occurrence of cracks in the substrate laminate 2, for example, cracks during lamination. The coupling between the resonance electrodes by the coupling control electrode 11 can be controlled by changing the connection position with the shield electrode 6 in addition to the overall shape and size of the coupling control electrode.

The above filter is used for the dielectric substrates 2A to 2A.
A ceramic green sheet made of a dielectric material having a number corresponding to 2 L is prepared, and a predetermined number of green sheets for forming the resonance electrodes 4A and 4B, the input / output connecting portions 10A and 10B, the input / output electrodes 8A and 8B, and the shield electrode 6 are prepared. It can be manufactured by applying a conductive paste such as a silver paste to a predetermined region by screen printing, stacking all of these green sheets in a predetermined arrangement, press-bonding them, and then firing. The shield electrode 6 and the input / output electrodes 8A and 8B formed on the exposed surface of the substrate laminate 2
With respect to, the green sheet may be formed by baking without applying the conductive paste, and then applying the conductive paste and baking.

[0023] In this embodiment, resonance electrodes 4A, the effective electrode length L _EF and 4B are, resonance electrodes 4A, the center line length of 4B (i.e. straight portion 4Aa～4Ae, total center line length of 4Ba～4Be) It is in the range of 0.90 to 0.94 times. That is, instead of the relational expression L = (1/4) λ (1 / ε ^1/2 ), L _EF = (1/4) λ (1 / ε ^1/2 ) · a {a is a correction coefficient} At that time, the value of a is set to a value within the range of 0.90 to 0.94.

FIG. 3 shows an example of the relationship between the correction coefficient value a and the Q value of the resonator. The correction coefficient value a is set to the resonance electrodes 4A, 4
It is related to the number of bends in B and the spacing between adjacent parallel portions of the spiral. That is, the larger the number of bends of the resonance electrodes 4A and 4B, the smaller the correction coefficient value a,
The correction coefficient value a becomes smaller as the interval between adjacent parallel portions of the spirals of the resonance electrodes 4A and 4B becomes smaller. Therefore, when a becomes smaller than 0.90, the number of folds gradually increases, which is advantageous in terms of downsizing, but the Q value sharply decreases. On the other hand, when a becomes larger than 0.94, the Q value hardly decreases,
Since the number of bends is small, there will be problems from the viewpoint of miniaturization.

Therefore, in the present invention, the correction coefficient value a is set to 0.90 as a range in which the size can be reduced and the Q value is less likely to decrease.
It is within the range of 0.94.

The number of bends of the resonance electrodes 4A and 4B is 2 to
5 (that is, the number of linear portions of the resonance electrode is 3 to 6)
Is preferred. The resonators have the same center line length and
= 1, that is, the resonance electrodes 4A and 4B preferably have a Q value in the range of 70 to 100% of the Q value in the case where the bending number is 0 and they are straight.

Specific examples are shown below. (1) When the width of the resonance electrodes 4A and 4B is 500 μm and the number of bends is 3 (the number of straight line portions is 4) [a = 0.92]
The Q value was 88% of that when a = 1.

(2) The width of the resonance electrodes 4A and 4B is 770 μm.
When the number of folds is 3 and the number of folds is 3 (the number of straight line portions is 4) [a
= 0.94], the Q value was 89% of that in the case of a = 1.

(3) The width of the resonance electrodes 4A and 4B is 500 μ
m and the number of folds is 4 (the number of straight line portions is 5) and the interval between adjacent parallel portions of the spiral is 300 μm [a
= 0.91], the Q value was 79% of that in the case of a = 1.

(4) The width of the resonance electrodes 4A and 4B is 770 μm.
m and the number of folds is 4 (the number of straight line portions is 5) and the interval between adjacent parallel portions of the spiral is 300 μm [a
= 0.92], the Q value was 78% of that in the case of a = 1.

FIG. 4 shows an example of frequency characteristics of the filter of the present embodiment as described above. Good bandpass characteristics with little insertion loss are obtained.

In the above embodiment, by adjusting the positions of the resonance electrodes 4A and 4B connected to the input / output connecting portions 10A and 10B, that is, the values of the distances DA and DB shown in FIG. The filter can be manufactured in consideration of impedance matching with an external circuit.

Further, in the above embodiments, since the exposed surfaces except the input / output electrodes 8a and 8B and the vicinity thereof are covered with the shield electrode 6, a high frequency resonator which is hardly influenced by external noise is obtained. be able to.

In the above embodiment, a two-stage filter using two resonance electrodes is shown, but the present invention can also be applied to a case where there are three or more resonance electrodes (that is, a filter with three or more stages). In that case, a resonance electrode that is not connected to the input / output electrode is formed on one or more laminated surfaces between the laminated surfaces on which the two resonant electrodes connected to the input / output electrodes are formed, and The coupling control electrode as described above may be arranged on the laminated surface between the adjacent ones.

[0035]

As is apparent from the above description, according to the present invention, it is possible to provide a filter using a quarter-wave resonator which can be downsized and whose Q value is not much reduced even when downsized. You can In particular, the present invention provides a small-sized filter with a small loss by using the characteristic resonance electrode and controlling the coupling between the resonators by the coupling control electrode.

In the filter of the present invention, by adjusting the position of the resonance electrode connected to the input / output connection portion, the filter can be manufactured in consideration of impedance matching with an external circuit.

Further, in the filter of the present invention, since the exposed surface except the input / output electrodes and the vicinity thereof is covered with the shield electrode, it is possible to obtain a high frequency filter which is hardly influenced by noise from the outside.

[Brief description of drawings]

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

FIG. 2 is a perspective view of an assembled state of an embodiment of a filter according to the present invention.

FIG. 3 is a graph showing a relationship between a correction coefficient value a and a Q value.

FIG. 4 is a graph showing frequency characteristics of a filter.

FIG. 5 is a perspective view showing a conventional stripline filter.

FIG. 6 is a plan view showing a conventional stripline filter.

[Explanation of symbols]

 2 substrate laminated body 2A-2L dielectric substrate 4A, 4B resonance electrode 4Aa-4Ae, 4Ba-4Be resonance electrode straight line part 6 shield electrode 8A, 8B input / output electrode 10A, 10B input / output connection part 11 coupling control electrode

Claims (4)

[Claims] 1. A plurality of dielectric substrates are laminated to form a substrate laminate, and a plurality of resonance electrodes are formed on different lamination surfaces of the substrate laminate, and the resonance electrodes are formed at least once. It has a bent shape, and shield electrodes are formed on two main surfaces and end faces of the substrate laminate, and one end of the resonance electrode extends to the end face of the substrate laminate and is connected to the shield electrode. And the first and second positions on the end surface of the substrate stack are different from each other.
Input / output electrodes are formed, and the uppermost layer and the lowermost layer of the laminated surface of the substrate laminated body on which the resonance electrodes are formed are respectively separated from the one end of the resonance electrodes and the first layer. And first and second input / output connecting portions for electrically connecting the first and second input / output electrodes are formed, and on a stacking surface different from the stacking surface on which the resonance electrode of the substrate stack is formed. And a coupling control electrode is formed on each of the laminated surfaces located between adjacent ones of the plurality of resonant electrodes, and the resonant electrode has an effective electrode length of 0.90 to a center line length. A filter characterized by being in the range of 0.94 times. 2. The filter according to claim 1, wherein the bending of the resonance electrode is made in a right angle in the same direction when going from the one end to the other end. 3. The filter according to claim 1, wherein the number of bends of the resonance electrode is 2 to 5. 4. The resonator having the resonance electrode has a Q value within a range of 70 to 100% of a Q value of a linear resonance electrode having the same center line length and no bending. The filter according to claim 1.