JPH088605A - Laminated dielectric filter - Google Patents

Abstract

PURPOSE:To provide a laminated dielectric filter which has a small size and a low loss. CONSTITUTION:The dielectric sheets 101a-101f are made of a dielectric ceramic material which is sintered at a low temperature, that is, such ceramic materials as those of a Bi-Ca-Nb-O system, etc., having specific inductive capacity of 58 that can be sintered at temperatures lower than about 950 deg.C are formed into green sheets. The internal electrodes having their patterns printed by the metallic paste of silver, copper, gold, etc., of a high dielectric constant construct the shielding electrodes 102a and 102b, the input/output coupling capacity electrodes 103a and 103b, the loading capacity electrodes 104a and 104b, and the strip line resonator electrodes 105a and 105b. Then the sheets 101a-101f are laminated together and sintered. The external electrodes are baked later with a metallic paste and construct the input/output terminals 107a and 107b and the ground electrodes 108a and 108b.

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 can be used in a high frequency device, especially a high frequency filter or an antenna duplexer of a mobile communication device such as a mobile phone.

[0002]

2. Description of the Related Art In recent years, mobile communication devices typified by mobile phones have been required to be smaller and lighter as the market has expanded rapidly, and accordingly, the components used in the devices have also been desired to be smaller and lighter. There is. An example of a conventional laminated dielectric filter will be described below with reference to the drawings.

FIG. 4 is an exploded perspective view of a conventional laminated dielectric filter. In FIG. 4, 1a to 1e are dielectric sheets, 2a and 2b are shield electrodes formed on the upper surfaces of the dielectric sheets 1a and 1d, respectively, 3a and 3b.
Is an input / output coupling capacitance electrode formed on the upper surface of the dielectric sheet 1b, 4a is a loading capacitance electrode formed on the upper surface of the dielectric sheet 1b, and 5a and 5b are dielectric sheets 1c.
, 6a and 6b are input / output terminals formed on the side surface of the filter body, and 7a and 7b are shield electrodes 2a and 2b, loading capacitance electrode 4a and strip line resonance on the side surface of the filter body. It is a ground terminal configured to be connected to the short-circuit side of the battery electrodes 5a and 5b.

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

First, the input / output coupling capacitance electrodes 3a and 3b and the strip line resonator electrodes 5a and 5b which face each other.
Respectively configure the input and output coupling capacitances. The stripline resonator electrodes 5a and 5b are electromagnetically coupled to each other and function as a resonance circuit. The loading capacitance electrode 4a and the strip line resonator electrodes 5a and 5b which face each other constitute the loading capacitance of the resonance circuit. The ground terminals 7a and 7b are ground electrodes, and the input / output electrodes 6a and 6b are connected to the input / output coupling capacitance electrodes 3a and 3b, respectively, to form a bandpass filter.

Further, since the resonance frequency of the strip line resonator can be lowered by adding the loading capacitance, the filter is downsized.

[0007]

However, in the above-mentioned structure, when a large loading capacitance is obtained in order to miniaturize the filter, the area of the loading capacitance electrode becomes large, and the strip resonator line is spread over a wide area. Since the characteristic impedance of (1) becomes low, the conductor loss of the strip resonator increases, and the filter insertion loss increases.

Further, in order to realize a wide band filter, it is necessary to increase the input / output capacitance, but in such a case, the area of the input / output capacitance electrode becomes large, resulting in a large filter.

In view of the above problems, it is an object of the present invention to provide a laminated dielectric filter which is small in size and has a small insertion loss.

[0010]

In order to solve the above problems, a laminated dielectric filter according to the present invention comprises a plurality of strip line resonances, one end of which is grounded and the other end of which is open on the first dielectric sheet. And a capacitor electrode is formed on each of the two second dielectric sheets, and the upper and lower sides of the first dielectric sheet are arranged so that the open end side of the strip line and the capacitor electrode overlap each other. The second dielectric sheet is laminated and the capacitance electrode is grounded. Alternatively, a plurality of strip line resonator electrodes, one end of which is grounded and the other end of which is open, are formed on the first dielectric sheet, and input / output electrodes are formed on the two second dielectric sheets, respectively. The second dielectric sheets are stacked above and below the first dielectric sheet such that the open end side of the strip line resonator electrode and the input / output electrodes overlap each other, and the strip line resonator electrode is placed in front of the second dielectric sheet. It has a configuration in which it is sandwiched between the writing output electrodes. Alternatively, a plurality of strip line resonator electrodes, one end of which is grounded and the other end of which is open, are formed on the first dielectric sheet, and inter-stage coupling capacitance electrodes are respectively formed on the two second dielectric sheets. And a second line above and below the first dielectric sheet such that the strip line resonator electrode and the inter-stage coupling capacitance electrode overlap each other.
Of the dielectric sheet, and the strip line resonator electrode is sandwiched between the inter-stage coupling capacitance electrodes.

[0011]

According to the present invention, since the input / output coupling capacitance electrode, the loading capacitance electrode, and the inter-stage coupling capacitance electrode are formed above and below the strip resonator electrode by the above-described structure, a large input / output capacitance can be obtained even with the same shape as the conventional one. , Loading capacity and interstage coupling capacity can be taken. In particular, by reducing the electrode area that forms the loading capacitance, the low impedance region on the strip line is shortened, and the increase in conductor loss of the strip resonator electrode can be suppressed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the laminated dielectric filter 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 the first embodiment of the present invention. In FIG. 1, 101a to 101f are dielectric sheets, and 102
a and 102b are shield electrodes formed on the upper surfaces of the dielectric sheets 101a and 101e, 103a and 103b and 103c and 103d are input / output coupling capacitance electrodes formed on the upper surfaces of the dielectric sheets 101b and 101d, respectively. 104a and 104b
Are loading capacitance electrodes formed on the upper surfaces of the dielectric sheets 101b and 101d, 105a and 1a, respectively.
05b is a strip line resonator electrode formed on the upper surface of the dielectric sheet 101c, 106a and 106b are interstage coupling capacitance electrodes formed on the upper surface of the dielectric sheets 101b and 101d, and 107a and 107b are on the side surface of the filter body. Input / output coupling capacitance electrode 103a
And 103c and 103b and 103d are connected to the input / output terminals, and 108a and 108b are short-circuited sides of the shield electrodes 102a and 102b, the loading capacitance electrodes 104a and 104b, and the strip line resonator electrodes 105a and 105b on the side surface of the filter body. A ground terminal configured to connect to.

The dielectric sheets 101a to 101f are formed of a low temperature sintered dielectric ceramic or the like. For example, a dielectric material such as Bi-Ca-Nb-O ceramic having a relative dielectric constant of 58 is fired at a temperature of about 950 degrees Celsius or less. It is made into a green sheet using a possible ceramic material.
Shield electrodes 102a and 102b, input / output coupling capacitance electrodes 103a and 103b, loading capacitance electrode 1
04a and 104b and the stripline resonator electrodes 105a and 105b are made of silver, copper,
The electrode pattern is printed with a metal paste having a high conductivity such as gold, and the dielectric sheets 101a to 101f are laminated and integrally fired. Input / output terminals 107a and 107b
The outer electrodes forming the ground electrodes 108a and 108b are formed by later baking a metal paste in this embodiment.

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

The electrical operating principle of the filter of this embodiment is almost the same as that of a combline filter. The operation principle of the combline filter is described in the literature (GLMattha
ei, "Microwave Filters, Improving Matching Network ant Cuplink Structure" / "Microwave Filters, Im
pedance-Matching Networks, and Coupling Structure
s ": McGraw-Hill, 1964).

Loading capacitance electrodes 104a and 10
4b and strip line resonator electrodes 105a and 105
The parallel plate capacitor formed between b acts as a parallel loading capacitor that lowers the resonance frequency of the stripline resonator. As a result, it is possible to shorten the length of the strip line resonator and set the resonance frequency high,
The filter itself can be miniaturized. The conductor loss of the strip line is composed of parallel plates, and is expressed by equation (1) when there is no edge effect (Yoshihiro Konishi, "Fundamentals and Applications of Microwave Circuits", page 52: Sogo Denshi Publishing, 1990).
As can be seen from the equation (1), the conductor loss of the strip line is in inverse proportion to the strip characteristic impedance, and the provision of the parallel loading capacitor reduces the characteristic impedance in that region and increases the conductor loss.

Lc = A / Zc (1) Lc: Conductor loss A: Constant Zc: Characteristic impedance In the laminated dielectric filter of the present embodiment, the loading capacitance electrodes 104a and 104b constituting the loading capacitance are stripline resonator electrodes. 105a and 1
It is configured both above and below 05b. As a result, as compared with the case where only one of them is formed, for example, the dielectric sheet 101
If the materials and thickness of c and 101d are the same, the electrode area that realizes the same loading capacitance can be halved, and the insertion loss of the filter due to the increase of conductor loss can be made very small.

FIG. 2 shows the result of actual measurement of the state. In FIG. 2, (a) shows the filter characteristic of the present embodiment, where the loading capacitance electrode is formed above and below the strip line resonator electrode, and (b) is the conventional filter in which the loading capacitance electrode is formed on only one side. The vertical axis represents transmission characteristics and the horizontal axis represents frequencies standardized by the center frequency. As shown in FIG. 2A, according to the present invention, a laminated dielectric filter having an insertion loss of about 1.5 dB was obtained.
On the other hand, in the case of the conventional configuration, the insertion loss was about 2.5 dB as shown in FIG.

Further, a parallel plate capacitor formed between the input / output coupling capacitance electrodes 103a and 103c and the strip line resonator electrode 105a, and the input / output coupling capacitance electrode 1
03b and 103d and strip line resonator electrode 10
The parallel plate capacitors formed between 5b each function as an input / output coupling capacitor. In this embodiment, since the input / output coupling capacitance electrodes are formed on both the upper and lower sides of the strip line resonator electrode, the input / output coupling capacitance electrodes are formed as compared with the case where the input / output coupling capacitance electrodes are formed only on the upper and lower sides of the strip line resonator electrode. Since the capacitance can be increased, a wide band filter can be configured even if it is small.

In addition, the strip line resonator electrode 105a
And 105b both above and below the interstage coupling capacitance electrode 108a.
By forming and 108b, the inter-stage coupling capacitance can be increased even with the same electrode area, and as a result, it is possible to realize a wide band filter characteristic even with a small size.
Further, by forming the inter-stage coupling capacitance electrode, not only the band pass characteristic is exhibited in the pass band, but also the attenuation pole can be formed at a desired frequency of the transfer characteristic. Therefore, it is possible to realize a selection characteristic superior to the Chebyshev characteristic.

Further, since the entire filter is electromagnetically shielded by the shield electrodes 102a and 102b, it is possible to prevent the filter characteristic from changing due to an external influence.

Further, in the electrode structure of this embodiment, the input / output coupling capacitance electrode and the loading capacitance electrode are formed on both sides of the strip line resonator electrode, and the dielectric sheet 101 is formed.
The electrode patterns on the upper surfaces of b and 101d are the same. As a result, the number of printing plates for the electrode pattern can be reduced by one, and the manufacturing becomes easier accordingly.

As described above, according to this embodiment, the size is small,
It is possible to realize a laminated dielectric filter having low loss, easy manufacturing, and high frequency selectivity.

The second embodiment of the laminated dielectric filter of the present invention will be described below.
Embodiments will be described with reference to the drawings.

As a second embodiment of this embodiment, FIG.
There is also a structure shown in. FIG. 3 is an exploded perspective view of a laminated dielectric filter according to the second embodiment of the present invention.
In FIG. 3, 109 and 110 are stepped impedance line resonators.
SIR) electrode (for example, Japanese Patent Application No. 5-28794)
8), respectively, consisting of thick line portions 109a and 110a and thin line portions 109b and 110b. The SIR electrodes 109 and 110 are grounded at the grounding portions 109c and 110c, respectively.

In the electrode structure shown in FIG. 3, SIR electrodes are used instead of the strip line resonator electrodes in the laminated dielectric filter of the first embodiment of the present invention shown in FIG. By using the SIR electrode, the length of the electrode can be shortened as compared with the case where the strip line resonator electrode is used, so that the size can be further reduced.

The line width of the portion forming the ground portions 109c and 110c is thicker than the other portions of the SIR resonator. By increasing the line width on the ground end side, the potential distribution is less likely to occur, and the ground end can be grounded more reliably.

In FIG. 3, the grounding portions 109c and 1 are provided.
Not only is the line width of 10c thickened, but the electrode pattern is also integrated and grounded. With such an electrode pattern, the ground end side of the SIR electrode can be grounded more reliably, and at the same time, even if the electrode pattern is misaligned, the effective line length of the SIR resonator, that is, the SIR electrode Thick line length 109a (110
Since the electrode structure in which the length obtained by adding a) and the thin line length 109b (110b) does not change is obtained, it is possible to suppress variations in filter characteristics. The above configuration can also be used for the ground end sides of the strip line resonator electrodes 105a and 105b in FIG.

Further, as shown in FIG. 3, the input / output coupling capacitance electrodes 103a to 103b are formed into a key-shaped electrode pattern, and the input / output capacitance electrodes 103a and 103b and the SIR electrode 1 are formed.
By making the line widths of the input / output coupling capacitance electrodes 103a and 103b narrower at the boundaries between the regions facing each other and the regions not facing each other than the regions facing each other, the print displacement of the electrode pattern may occur. Since the facing area of each electrode that determines the coupling capacitance between the input and output does not change significantly, it is possible to suppress variations in filter characteristics. This configuration corresponds to the input / output coupling capacitance electrode 10 in FIG.
It can also be used for 3a and 103b.

In addition, as shown in FIG. 3, the electrode patterns of the loading capacitance electrodes 104a and 104b have a line width at the boundary between a region facing the strip resonator electrodes 105a and 105b and a region not facing the strip resonator electrodes 105a and 105b. By making it thin, even if the print displacement of the electrode pattern occurs, the facing area of each electrode that determines the loading capacity does not change significantly, so that variations in filter characteristics can be suppressed. This configuration can also be used for the loading capacitance electrodes 104a and 104b in FIG.

[0032]

As described above, according to the present invention, a plurality of strip line resonator electrodes, one end of which is grounded and the other end of which is open, are formed on the first dielectric sheet, and the upper and lower dielectric sheets are interposed therebetween. By configuring the loading capacitance electrode, the input / output coupling capacitance electrode and the inter-stage coupling capacitance electrode, it is possible to realize a small laminated dielectric filter with a small loss.

[Brief description of drawings]

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

FIG. 2 is a filter characteristic diagram for explaining the operation in the first embodiment of the present invention.

FIG. 3 is an exploded perspective view of a laminated dielectric filter according to a second embodiment of the present invention.

FIG. 4 is an exploded perspective view of a conventional laminated dielectric filter.

[Explanation of symbols]

 101a to 101f Dielectric sheets 102a and 102b Shield electrodes 103a to 103d I / O electrodes 104a and 104b Loading electrodes 105a and 105b Strip line resonator electrodes 106a and 106b Interstage coupling capacitance electrodes 107a and 107b I / O terminals 108a and 108b Ground terminals 109 and 110 SIR electrodes 109a and 110a Thick line sections 109b and 110b Narrow line sections 109c and 110c Ground section

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Atsushi Sasaki 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (12)

[Claims] 1. A plurality of strip line resonator electrodes, one end of which is grounded and the other end of which is open, are formed on a first dielectric sheet, and capacitive electrodes are respectively formed on two second dielectric sheets. And the second dielectric sheet is laminated above and below the first dielectric sheet such that the open end side of the strip line and the capacitance electrode overlap each other, and the capacitance electrode is grounded. Multilayer dielectric filter. 2. A plurality of strip line resonator electrodes, one end of which is grounded and the other end of which is open, are formed on a first dielectric sheet, and input and output are made on two second dielectric sheets, respectively. An electrode is formed, and the second dielectric sheet is laminated above and below the first dielectric sheet such that the open end side of the strip line resonator electrode and the input / output electrode overlap each other, and the strip line resonator is formed. A laminated dielectric filter having an electrode sandwiched between the input and output electrodes. 3. A plurality of stripline resonator electrodes, one end of which is grounded and the other end of which is open, are formed on a first dielectric sheet, and interstages are respectively formed on two second dielectric sheets. A striped resonator in which a coupling capacitance electrode is formed, and the second dielectric sheet is laminated above and below the first dielectric sheet so that the stripline resonator electrode and the interstage coupling capacitance electrode overlap each other. A laminated dielectric filter having electrodes sandwiched between the inter-stage coupling capacitance electrodes. 4. The laminated dielectric filter according to claim 1, wherein the electrode patterns formed on the upper surface of the second dielectric sheet are the same. 5. The width of the capacitance electrode is narrower than the opposing region in the vicinity of the boundary between the region where the capacitance electrode and the strip line resonator electrode face each other and the region where they do not face each other. Multilayer dielectric filter. 6. The width of the input / output electrode is narrower than that of the facing area in the vicinity of the boundary between the area where the input / output electrode and the strip line resonator electrode face each other and the area where they do not face each other. The laminated dielectric filter according to. 7. The width of the inter-stage coupling capacitance electrode is narrower than the opposing region in the vicinity of the boundary between the region where the inter-stage coupling capacitance electrode and the strip line resonator electrode face each other and the region where they do not face each other. The laminated dielectric filter according to claim 3. 8. The laminated dielectric body according to claim 1, wherein shield electrodes are provided above and below the stacked dielectric sheets via dielectrics, and the shield electrodes are grounded. filter. 9. The multilayer dielectric filter according to claim 1, wherein the line width on the open end side of the strip resonator electrode is made thicker in a step shape than the line width on the ground end side. 10. The multilayer dielectric filter according to claim 1, wherein the strip resonator electrode is grounded by widening the line width on the grounding end side. 11. The multilayer dielectric filter according to claim 9, wherein the strip resonator electrode has an electrode pattern in which lines on the ground end side of the strip resonator electrode are integrated with each other. 12. A dielectric sheet, each of which is formed by stacking a plurality of thin dielectric green sheets, electrodes are printed on each of the dielectric sheets, and each of the dielectric sheets is stacked and fired. The laminated dielectric filter according to any one of claims 1 to 3, characterized in that.