JP2003060406A - Dielectric laminate filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact, thin and planar dielectric laminate filter having low loss and proper narrow band-pass characteristics. SOLUTION: The filter has at least four layers of dielectric sheets, at least two shield electrode layers, at least one stripline resonator electrode layer and at least one capacitance electrode layer. The dielectric sheets, having the stripline resonator electrodes and the dielectric sheets having the capacitance electrodes, are laminated one above and below the other and are sandwiched in between the dielectric sheets having the shield electrodes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small dielectric laminated filter mainly used in high frequency radio equipment such as a mobile phone.

[0002]

2. Description of the Related Art In recent years, dielectric filters have been widely used as high frequency filters for mobile phones. However, there is a demand for further miniaturization and thinning, and a planar dielectric that can be made thinner than a coaxial type. Laminated filters are promising in the future. Hereinafter, an example of the above-mentioned conventional dielectric multilayer filter will be described with reference to the drawings.

FIG. 10 is an exploded perspective view showing the structure of a conventional dielectric laminated filter.

In FIG. 10, 1 and 2 are thick dielectric layers. Coil electrodes 3a and 3b are provided on the dielectric sheet 3.
However, on the dielectric sheet 4, the capacitor electrodes 4a, 4b
However, on the dielectric sheet 5, capacitor electrodes 5a, 5b
However, on the dielectric sheet 7, a shield electrode 7a,
7b is formed. The dielectric sheet 6 for protecting electrodes, the dielectric layer and the dielectric sheet are all stacked to form a laminated structure.

The operation of the dielectric filter having the above structure will be described below.

First, the opposing capacitor electrodes 4a and 5a
And 4b and 5b respectively form a parallel plate capacitor. Each parallel plate capacitor is connected in series via the coil electrodes 3a and 3b and the side surface electrodes 8a and 8b to function as a resonance circuit. The two coils are magnetically coupled. A side-pass electrode 8b serves as a ground electrode, and the side-face electrode 8c is connected to terminals 3c and 3d connected to the coil electrode to form a bandpass filter that serves as an input / output terminal (see, for example, Japanese Patent Laid-Open No. Hei 3
-72706).

[0007]

However, in the above-mentioned structure, when the coil electrodes are brought close to each other to reduce the size and the distance between them is narrowed, the magnetic field coupling between the resonators becomes too large and a good band having a narrow band is obtained. It has a problem that it is difficult to realize the path characteristics.

Further, since it is difficult to increase the unloaded Q value of the coil electrode, there is a problem that the insertion loss of the filter is large.

In view of the above problems, it is an object of the present invention to provide a small-sized and thin planar dielectric laminated filter having low loss and excellent narrow bandpass characteristics.

[0010]

In order to solve the above-mentioned problems, a dielectric laminated filter of the present invention comprises a dielectric sheet having at least 4 layers, a shield electrode layer having at least 2 layers, and at least 1 layer. A stripline resonator electrode layer, and at least one or more capacitive electrode layers,
The dielectric sheet having the stripline resonator electrodes formed thereon and the dielectric sheet having the capacitance electrodes formed thereon are vertically sandwiched and laminated between the dielectric sheets having the shield electrodes formed thereon. It has a configuration.

With the above-described structure, the present invention can use a distributed constant type resonator with a high unloaded Q value to reduce the insertion loss of the filter, and the capacitive electrode layer prevents the resonator from being unloaded. Since a large capacitance can be formed without deteriorating the Q value, and the coupling between stripline resonators can be performed by a combination of electromagnetic field coupling and electric field coupling via a capacitive electrode, a filter having an attenuation pole in a narrow band. The characteristics can be realized.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION (Embodiment 1) A first embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 (a) is an exploded perspective view of a dielectric laminated filter showing a first embodiment of the present invention, and FIG. 1 (b) is A- of a dielectric laminated filter showing the first embodiment of the present invention. It is sectional drawing of A'plane. 2 is an equivalent circuit diagram for explaining the operation of the dielectric multilayer filter of the first embodiment shown in FIG.

In FIG. 1, 10a and 10b are thick dielectric sheets. Stripline resonator electrodes 11a and 11b are provided on the dielectric sheet 10a and the dielectric sheet 1
The second electrode 12a, the third electrode 12b, and the fourth electrodes 12c and 12d of the parallel plate capacitor are formed on 0c.

A shield electrode 13a is formed on the dielectric sheet 10b, and a shield electrode 13b is formed on the dielectric sheet 10d. Electrode protection dielectric sheet 1
0e and these dielectric sheets are all overlaid to form a laminated structure. As the dielectric material, for example, a Bi-Ca-Nb-O-based ceramic material having a relative dielectric constant of 58 or the like, which can be fired at a temperature of about 950 degrees Celsius or less, is used as a green sheet, and a conductive material such as silver, copper, or gold is used. The electrode pattern is printed with a metal paste having a high rate, and is laminated and integrally fired.

By firing, the dielectric sheet and each electrode layer shrink by several tens of percents in the vertical and horizontal directions, respectively, and become smaller.
If the contraction rate of the electrode layer is larger than the contraction rate of the dielectric sheet, the terminal of the electrode will be retracted inward at the end face of the laminate, so that the terminal electrode formed on the side surface cannot be connected. In order to avoid this, the stripline resonator electrode and the shield electrode are formed on each of a plurality of dielectric sheets by using an electrode material whose shrinkage factor during firing is slightly smaller than that of the dielectric sheets. Are laminated and integrally fired. By doing this,
The terminal of the electrode protrudes from several μm to several tens of μm on the end face of the laminated body, so that the connection with the terminal electrode formed on the side face can be performed well.

The thick dielectric sheets 10a and 10b can be made to have a predetermined thickness by laminating several thin green sheets. By doing so, all the dielectric sheets can be configured to have the same standardized thickness, which facilitates manufacturing.

The fourth electrodes 12c and 12d are connected to the side surface electrodes 14a and 14b of the input / output terminals. The upper and lower shield electrodes 13a, 13b are the side electrodes 15a, 15 of the ground terminal.
connected to b. By providing side electrodes, which are ground terminals, on the two side surfaces of the stripline resonator, which are the open-end side surface and the short-circuit end side surface, respectively, and grounding the side electrodes, the resonance of the shield electrode is suppressed and the filter characteristics are deteriorated. Can be prevented. Further, by forming a side surface electrode serving as a ground terminal between the input terminal and the output terminal, there is an effect that isolation between the input and output terminals can be achieved. Furthermore, 2
By making the number or shape of the side surface electrodes provided on one side surface different and making them asymmetric, the mounting direction of the dielectric multilayer filter can be easily confirmed.

The shape of the shield electrodes 13a, 13b should be inside the outer periphery of the dielectric sheet, except for the portion where the outer periphery of the shield electrode is connected to the side electrode serving as a ground terminal and its periphery. , The size of the shield electrode is made smaller than the size of the dielectric sheet. Since the adhesive strength between the laminated ceramic green sheets becomes weaker in the places where the metal paste forming the electrode pattern is sandwiched, especially in the outer periphery of the dielectric sheet, the margins of the shield electrode are arranged so that the ceramics are directly adhered to each other. To provide.

Further, by making the shapes of the two layers of shield electrodes the same, there is an advantage that only one type of screen for printing shield electrode patterns is required.

Further, since the upper and lower two layers of shield electrodes are both formed by the inner layer electrodes, they can be manufactured by the same method as the stripline resonator electrode layer and the capacitance electrode layer, and therefore are easy to manufacture. Dielectric sheet for electrode protection 1 on top layer
By laminating 0e, it is possible to protect the upper shield electrode layer formed of the inner layer electrode having insufficient mechanical strength. Of course, since the lower shield electrode layer is also printed on the dielectric sheet 10d, it is protected from the outside by the dielectric sheet 10d.

The stripline resonator has a line width on the short-circuited end side of the stripline in the middle of the stripline,
From the wide parts 111a, 111b to the width details 112a, 112
The size is narrowed in a stepwise manner to b to reduce the size. Electrodes 112a, 112b of stripline resonator width detail
The short-circuited end side of is connected to the side surface electrode 15b of the ground terminal through the wide common ground electrode 113 and is grounded. The change in length of the wide common ground electrode 113 is greater than the change in length of the stripline resonator electrodes 11a and 11b.
Since the influence on the resonance frequency is small, it is possible to suppress the variation of the resonance frequency due to the accuracy when cutting the dielectric sheet.

The dielectric laminated filter of the first embodiment having the above-described structure will be described below with reference to FIGS.
The operation will be described with reference to FIG.

First, the stripline resonator electrode 11
a, 11b and the second, third and fourth electrodes 12a, 12b, 12c, 12d facing them are parallel plate capacitors 21, 22, 23, 24, 25, respectively.
26 is formed.

A parallel plate capacitor 21 formed between the second electrode 12a and the stripline resonator electrode 11a.
And the second electrode 12a and the stripline resonator electrode 1
The parallel plate capacitor 22 formed between 1b acts as an interstage coupling capacitor. Therefore, the inter-stage coupling between the resonators is performed by a combination of electromagnetic field coupling between the stripline resonators and electric field coupling through the parallel-plate capacitors 21 and 22 connected in series. If the distance between the stripline resonator electrodes is reduced for downsizing,
Although the interstage coupling becomes too large, it becomes difficult to realize a good narrow band characteristic. However, in the configuration of the present invention, the combination of the electromagnetic field coupling and the electric field coupling cancels each other to reduce the interstage coupling. Therefore, narrow band characteristics can be realized. At the same time, the resonance phenomenon due to the combination of the electromagnetic field coupling and the electric field coupling makes it possible to configure the attenuation pole in the transfer characteristic, and to obtain a more excellent selection characteristic.

The capacitance electrode of the inter-stage coupling capacitor is composed of the second electrode 12a which is a floating electrode and is not electrically connected to any terminal electrode provided on the capacitance electrode layer. The feature of the configuration of the present embodiment is that the first electrode forming the parallel plate capacitor is shared by the electrode surfaces 11a and 11b of the stripline resonator and the parallel plate capacitors 21 and 22 are connected in series. This realized the interstage coupling capacitor with a planar structure that allows stacking.

A parallel plate capacitor 23 formed between the third electrode 12b and the stripline resonator electrode 11a.
And the third electrode 12b and the stripline resonator electrode 1
The parallel plate capacitor 24 formed between 1b acts as a parallel loading capacitor that lowers the resonance frequency of the stripline resonator. Therefore, the length of the stripline resonators 11a and 11b can be made shorter than a quarter wavelength, and the filter can be miniaturized.

In FIG. 1, the third electrode 12b is integrated with the two stripline resonator electrodes 11a and 11b, but the third electrode 12b is divided into two parts to form a stripline resonator. A third electrode may be provided on each of the electrodes 11a and 11b to be grounded.

A parallel plate capacitor 25 formed between the fourth electrode 12c and the stripline resonator electrode 11a, and a parallel plate capacitor formed between the fourth electrode 12d and the stripline resonator electrode 11b. 26
Respectively function as input / output coupling capacitors.

In the structure of this embodiment, since the shield electrode layer and the capacitor electrode layer are composed of different layers,
A large coupling capacitance is formed between the stripline resonator electrode and the capacitance electrode while keeping the thickness of the dielectric sheet between the stripline resonator electrode layer and the shield electrode layer large in order to obtain a high unloaded Q value. It is possible to obtain a large capacity necessary for use in input / output coupling or interstage coupling. If the capacitor electrode is formed in the same layer as the shield electrode layer, the dielectric sheet between the shield electrode layer and the capacitor electrode layer must be thin, the unloaded Q value is deteriorated, and ,
Achieving the required degree of coupling with the filter of the present invention is very difficult. However, the configuration of the present invention skillfully solves such a problem by making the capacitive electrode layer provided separately from the shield electrode layer face the stripline resonator electrode layer with the thin dielectric sheet interposed therebetween. .

Further, in this structure, since all the stripline resonator electrodes are printed on the dielectric sheet 10a and all the capacitive electrodes are printed on the dielectric sheet 10c, electrode printing is performed on these two dielectric sheets. Since only the body sheet and the two shield electrode layers are required, the number of man-hours for printing is small and the variation in filter characteristics can be suppressed. That is,
By configuring the stripline resonator electrode layer with a single electrode layer, the relative positional accuracy between the stripline resonator electrodes can be increased, and therefore variations can be reduced. In addition, by configuring the capacitive electrode layer with a single electrode layer, the thickness of the dielectric sheet, which has a large effect on filter characteristic variations, can be controlled by using a single dielectric layer between the stripline resonator electrode layer and the capacitive electrode layer. Since it is sufficient to perform only the body sheet, there is a great advantage that manufacturing control becomes easy.

FIG. 3 is a perspective view showing the arrangement of the capacitive electrode and the stripline resonator electrode of the dielectric laminated filter according to the first embodiment of the present invention. In the manufacturing process of the dielectric laminated filter, it is considered that the filter characteristics vary due to the positional deviation between the stripline resonator electrode layer and the capacitive electrode layer.

In order to reduce this effect, as shown in FIG. 3, in the region where each capacitance electrode overlaps the outer edge of the stripline resonator electrode, the capacitance electrode is narrowed to narrow the width of the electrode. A constriction 31 is formed on the second electrode 12a, and a constriction 32, 3 is formed on the third electrode 12b.
3, 34 are formed, and constrictions 35, 36 are formed on the fourth electrodes 12c, 12d, respectively. By providing such a narrowed constricted region, the change in the area of the overlapping region occurring when the stripline resonator electrode layer and the capacitive electrode layer are misaligned can be made smaller than when there is no constriction. can do.

As shown in the electrode layout diagram of FIG. 3, the electrode 12a of the inter-stage coupling capacitor is a stripline resonator electrode 11a, because of the electrode pattern layout.
11b is located not between the open end but between the open end and the short-circuited end. Strictly speaking, it is different from the equivalent circuit of FIG. 2, but taps down by shifting the position of the inter-stage coupling capacitor. Since this is equivalent to reducing the capacitance value of the inter-stage coupling capacitor equivalently, it is represented by the circuit of FIG. 2 for convenience.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings. FIG. 4 is an exploded perspective view of the dielectric laminated filter showing the second embodiment of the present invention. 4, the same components as those in FIG. 1 are designated by the same reference numerals.

The difference from the first embodiment is that instead of the fourth electrodes 12c and 12d of the first embodiment, fourth electrodes 12e and 12f taken out from the lateral direction of the strip line resonator electrode are used. Was used. In accordance with this, one side electrode 14a, 14b is used as an input / output terminal.
4c, 14d, and the side electrode to be the ground terminal is 15
Changed from a to 15c.

By taking out the fourth electrode serving as the input / output electrode from the lateral direction, the distance between the input / output electrodes can be increased, so that the spatial coupling between the input and output can be reduced and the isolation can be achieved. Can be taken large.

Also, in the second embodiment, the coupling position of the fourth electrode is located between the open end and the short-circuited end of the stripline resonator electrode. An equivalent circuit diagram of the dielectric multilayer filter of the second embodiment is as shown in FIG. The input / output coupling capacitors 25 and 26 are tapped down and connected to the stripline resonator. Therefore,
Wide portions 111a and 111 of the stripline resonator electrode
b are electrodes 113a and 114a, 113b and 1 respectively.
14b can be considered separately.

Here, the series circuit 51 composed of the electrode 113a and the loading capacitor 23, and the electrode 11
The series circuit 52 composed of 3b and the loading capacitor 24 respectively operates as a series resonance circuit. At the frequency at which the series circuits 51 and 52 resonate, the impedance becomes zero, which causes an attenuation pole in the transfer characteristic of the filter. That is, in the second embodiment, in addition to the attenuation pole generated by the combination of the electromagnetic field coupling and the electric field coupling of the resonator included in the first embodiment, the attenuation pole generated by the series resonance of the series circuits 51 and 52. Therefore, it is possible to realize more excellent selection characteristics.

(Embodiment 3) A third embodiment of the present invention will be described below with reference to the drawings. FIG. 6 is an exploded perspective view of the dielectric laminated filter showing the third embodiment of the present invention. 6, the same components as those in FIGS. 1 and 4 are designated by the same reference numerals. FIG. 7 is an equivalent circuit diagram for explaining the operation of the dielectric multilayer filter of the third embodiment shown in FIG.

The third embodiment differs from the second embodiment in that it has a three-stage filter.
The stripline resonator electrodes 61a, 61b, 61c are composed of wide portions 161a, 161b, 161c and narrow portions 162a, 162b, 162c, respectively, and the short-circuited end side of the narrow portion is grounded via a wide common ground electrode 163. It is connected to the side electrode 15b serving as a terminal and grounded.

The second electrode 62a is the dielectric sheet 10c.
On top of the stripline resonator electrodes 61a, 61b,
It partially opposes all of 61c and realizes electric field coupling between stages.

In the areas on the dielectric sheet 10c facing the stripline resonator electrodes, respectively,
The third electrode 62b is partially formed in the remaining area where the second electrode is formed and grounded. The parallel plate capacitor formed between the third electrode 62b and the stripline resonator electrode acts as a parallel loading capacitor that lowers the resonance frequency of the stripline resonator. Therefore,
The lengths of the stripline resonators 11a and 11b can be made shorter than a quarter wavelength, and the filter can be miniaturized.

The shield electrodes 63a and 63b are respectively formed on the dielectric sheets 10b and 10d so as to cover the whole. By laminating the dielectric sheet 10e for electrode protection on the uppermost layer, the upper shield electrode layer formed of the inner layer electrode having insufficient mechanical strength can be protected.

Also, in the third embodiment, the coupling position of the fourth electrode is located between the open end and the short-circuited end of the stripline resonator electrode, so that the dielectric laminated filter of the third embodiment is used. The equivalent circuit diagram of is as shown in FIG. The input / output coupling capacitors 25 and 26 are tapped down and connected to the stripline resonator. Therefore, the wide portions 161a and 161b of the stripline resonator electrode are
Are electrodes 163a and 164a, 163b and 16 respectively.
4b can be considered separately.

Here, the series circuit 77 composed of the electrode 163a and the loading capacitor 74, and the electrode 16
At a frequency at which the series circuit 78 composed of 3b and the loading capacitor 754 resonates, an attenuation pole is generated in the transfer characteristic of the filter. This is the same as in the second embodiment.

Adjacent stripline resonators are electromagnetically coupled to each other, and interstage coupling capacitors 71 and 7 are connected.
The electric field coupling is performed via 2, 73, and the coupling between the stripline resonators is performed by the combination of the electromagnetic field coupling and the electric field coupling. Since two attenuation poles can be configured, it is possible to obtain even better selection characteristics.

The basic configuration in the third embodiment is the second
Although it is the same as that of the first embodiment, of course, the same direction as that of the first embodiment may be adopted by setting the extraction direction of the input / output terminals to the direction of the open end of the stripline resonator electrode.

As described above, in the third embodiment, by forming the filter in three stages, it is possible to obtain a more excellent selectivity. Needless to say, the selectivity can be further increased by increasing the number of stages to four or five.

(Embodiment 4) Hereinafter, a fourth embodiment of the present invention will be described with reference to the drawings. FIG. 8 is an exploded perspective view of a dielectric laminated filter showing a fourth embodiment of the present invention. 8, the same components as those in FIGS. 1, 4 and 6 are designated by the same reference numerals. In addition, FIG.
FIG. 9 is an equivalent circuit diagram for explaining the operation of the dielectric multilayer filter according to the fourth embodiment shown in FIG.

The operation of the fourth embodiment is almost the same as that of the third embodiment. The difference between the fourth embodiment and the third embodiment is the method of connecting the interstage coupling capacitors. In the third embodiment, the second electrode forming the interstage coupling capacitor is composed of one electrode 62a facing all the stripline resonator electrodes, but in the fourth embodiment, the second electrode is formed. The electrode is an electrode 8 provided for each adjacent stripline resonator electrode.
It is composed of 1, 82.

Adjacent stripline resonators are electromagnetically coupled to each other, and a capacitor 8 connected in series is used.
The electric field coupling is performed through the inter-stage coupling capacitors configured by 1 and 82 and 83 and 84, and the coupling between the stripline resonators is performed by the combination of the electromagnetic field coupling and the electric field coupling. Two resonance poles can be formed in the transfer characteristic by the resonance phenomenon due to the combination of coupling.

As described above, in the fourth embodiment, the same effect as that of the third embodiment can be obtained, and the resonance due to the combination of the electromagnetic field coupling and the electric field coupling is provided for each adjacent stripline resonator. Since the characteristics can be designed, there is an advantage that the design is easier than in the third embodiment.

In addition to the embodiments described above, various modifications of the dielectric multilayer filter and combinations thereof, such as the shape of the electrode pattern and the arrangement of the terminals, are naturally conceivable, but such modifications are the gist of the present invention. It is a matter of course that the present invention is included in the scope of the present invention as long as it complies with.

[0054]

As described above, the present invention has at least four or more dielectric sheets, at least two or more shield electrode layers, at least one or more stripline resonator electrode layers, and at least one or more layers. Of the capacitor electrode layer, the dielectric sheet having the stripline resonator electrode formed thereon and the dielectric sheet having the capacitor electrode formed above and below the dielectric sheet having the shield electrode formed thereon. It is possible to provide a small-sized and thin planar dielectric laminated filter having low loss, excellent narrow bandpass characteristics, and stacking by sandwiching and stacking the two.

[Brief description of drawings]

FIG. 1A is an exploded perspective view of a dielectric laminated filter according to a first embodiment of the present invention, and FIG. 1B is a cross section taken along the line AA ′ of the dielectric laminated filter according to the first embodiment of the present invention. Figure

FIG. 2 is an equivalent circuit diagram for explaining the operation of the dielectric laminated filter of the first embodiment shown in FIG.

FIG. 3 is a perspective view showing the arrangement of capacitive electrodes and stripline resonator electrodes of the dielectric multilayer filter according to the first embodiment of the present invention.

FIG. 4 is an exploded perspective view of a dielectric multilayer filter according to a second embodiment of the present invention.

FIG. 5 is an equivalent circuit diagram for explaining the operation of the dielectric multilayer filter according to the second embodiment shown in FIG.

FIG. 6 is an exploded perspective view of a dielectric multilayer filter according to a third embodiment of the present invention.

FIG. 7 is an equivalent circuit diagram for explaining the operation of the dielectric multilayer filter according to the third embodiment shown in FIG.

FIG. 8 is an exploded perspective view of a dielectric multilayer filter according to a fourth embodiment of the present invention.

9 is an equivalent circuit diagram for explaining the operation of the dielectric multilayer filter according to the fourth embodiment shown in FIG.

FIG. 10 is an exploded perspective view of a conventional dielectric multilayer filter.

[Explanation of symbols]

10a, 10b, 10c, 10d, 10e Dielectric sheets 11a, 11b Stripline resonator electrode 12a Second electrode 12b Third electrode 12c, 12d Fourth electrode 13a, 13b Shield electrode 14a, 14b Input / output terminal 15a, 15b Ground terminal

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Koji Banno             55-12 Ohsumihama, Kyotana-shi, Kyoto Prefecture Matsushita Nitto             Denki Co., Ltd. (72) Inventor Tadanori Fujisawa             55-12 Ohsumihama, Kyotana-shi, Kyoto Prefecture Matsushita Nitto             Denki Co., Ltd. (72) Inventor Toshikazu Muramatsu             55-12 Ohsumihama, Kyotana-shi, Kyoto Prefecture Matsushita Nitto             Denki Co., Ltd. (72) Inventor Mitsuhiro Fujita             55-12 Ohsumihama, Kyotana-shi, Kyoto Prefecture Matsushita Nitto             Denki Co., Ltd. F-term (reference) 5J006 HB05 HB17 JA01 JA11 JA12                       LA21 NA04 NB07 NC03

Claims (2)

[Claims] 1. A stripline resonator electrode is formed on a dielectric sheet by using an electrode material made of a metal paste having a shrinkage factor at firing which is slightly smaller than that of the dielectric sheet, and a dielectric sheet is further laminated. A laminated dielectric filter characterized by being integrally fired. 2. A wide common ground electrode is formed on the same electrode layer as the stripline resonator electrode layer, and a short-circuited end of the stripline resonator is electrically connected to a side ground terminal via the common ground electrode. The dielectric multilayer filter according to claim 1, wherein the dielectric multilayer filter is connected and grounded.