JPH05199010A - Band pass filter - Google Patents

Abstract

PURPOSE:To obtain the band pass filter with a structure by which the impedance is simply and accurately adjusted. CONSTITUTION:Coil electrodes 14, 16 are formed to one major side of a 1st dielectric layer 12. Extract terminals 20, 24 and earth terminals 18, 22 are formed so as to be extended to the end opposite to the 1st dielectric layer 12 from the coil electrodes 14, 16. A 1st earth electrode 26 is formed to other major side of the 1st dielectric layer 12. The thickness of the 1st dielectric layer 12 and a 2nd dielectric layer 34 is adjusted within a range of 1000mum or below. The extraction terminals 20, 24 are connected to the external extract electrodes. The earth terminals 28, 22 of the coil electrodes 14, 16 are connected to earth terminals 28, 30 of the 1st earth electrode 26 and to earth terminals 38, 40 of the 2nd earth electrode 36.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bandpass filter, and more particularly to a bandpass filter used in the quasi-microwave region of 1 GHz to 3 GHz.

[0002]

2. Description of the Related Art FIG. 9 is an exploded perspective view showing an example of a conventional bandpass filter which is the background of the present invention. The bandpass filter 1 includes two dielectric layers 2. Two coil electrodes 3 are formed between the two dielectric layers 2.
The coil electrode 3 is formed in the shape of a part of the loop. The two coil electrodes 3 are arranged so as to be line-symmetrical to each other. From the vicinity of one end of each coil electrode 3,
The ground terminals 4 are formed so as to extend to the opposite ends of the dielectric layer 2. Separated from this ground terminal,
The lead terminals 5 are formed so as to extend to the opposite ends of the dielectric layer 2. These two coil electrodes 3 are electromagnetically coupled.

Two ground electrodes 6 are formed so as to face the two coil electrodes 3 via the two dielectric layers 2. The ground electrode 6 is formed in a planar shape. Ground terminals 4 are formed on these ground electrodes so as to extend to opposite ends of the dielectric layer 2, and are connected to the ground terminals 4 of the two coil electrodes 3. Further, a protective layer 7 is formed on these ground electrodes 6. Although each coil electrode 3 functions as a resonator, the two resonators electromagnetically couple with each other to function as a bandpass filter.

[0004]

When using such a bandpass filter, it is desirable to perform impedance matching with a circuit incorporating the bandpass filter. Therefore, it is necessary to adjust the impedance according to the circuit incorporating the bandpass filter. In order to adjust the impedance of the bandpass filter, for example, a method of changing the distance between the extraction terminal and the ground terminal can be considered. However, even if the distance between the extraction terminal and the ground terminal is slightly changed, the impedance changes greatly, and it is difficult to accurately adjust the impedance. Further, if there is a restriction on the arrangement of the terminals due to the design of the bandpass filter, the distance between the terminals cannot be changed and the impedance cannot be adjusted.

Therefore, a main object of the present invention is to provide a bandpass filter having a structure capable of easily and accurately adjusting impedance.

[0006]

The present invention is directed to a dielectric layer, two coil electrodes in the shape of a loop or a part of the loop formed on one main surface side of the dielectric layer, and a dielectric layer. A ground electrode formed on the other main surface side, a ground terminal drawn out from the coil electrode and the ground electrode for connecting the coil electrode and the ground electrode, and an extraction terminal drawn out from the coil electrode at a distance from the ground terminal. Including,
The ground terminal and the lead-out terminal drawn out from one coil electrode and the ground terminal and the lead-out terminal drawn out from the other coil electrode are formed in opposite directions, and the thickness of the dielectric layer between the two coil electrodes and the ground electrode. Is 100
It is a bandpass filter formed to 0 μm or less.

[0007]

The bandpass filter is equivalently represented by a circuit having an inductance component and a capacitance component. The capacitance component can be changed equivalently by adjusting the thickness of the dielectric layer between the coil electrode and the ground electrode within the range of 1000 μm or less.

[0008]

According to the present invention, the impedance of the bandpass filter can be changed by changing the thickness of the dielectric layer between the coil electrode and the ground electrode. Therefore, impedance matching with a circuit incorporating the bandpass filter can be achieved. To change the thickness of the dielectric layer, it suffices to change the number of laminated ceramic green sheets made of dielectric material in the manufacturing process, and the thickness can be adjusted accurately and easily.

The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

[0010]

1 is a perspective view showing an embodiment of the present invention, and FIG. 2 is an exploded perspective view thereof. The bandpass filter 10 includes a first dielectric layer 12. First dielectric layer 12
Is adjusted within the range of 1000 μm or less. Two coil electrodes 14 and 16 are formed on one main surface of the first dielectric layer 12. The coil electrodes 14 and 16 are formed in the shape of a part of the loop, which is a U shape in this embodiment. These coil electrodes 14 and 16 are arranged so that their openings are in the same direction. Coil electrodes 14, 16
The length L of is set to a value represented by the following equation, where λ is the wavelength and ε is the dielectric constant of the first dielectric layer 12.

[0011]

[Equation 1]

From the vicinity of one end of one coil electrode 14 to the first
The ground terminal 18 is formed so as to be drawn to one end of the dielectric layer 12. Further, the first dielectric layer 1 is separated from the coil electrode 14 at a distance from the ground terminal 18.
The lead-out terminal 20 is formed so as to be pulled out to one end of the terminal 2. Similarly, the ground terminal 22 is formed so as to be drawn out from the vicinity of one end of the other coil electrode 16 to the other end of the first dielectric layer 12. An extraction terminal 24 is formed at a distance from the ground terminal 22 so as to be extracted from the coil electrode 16 to the other end of the first dielectric layer 12. That is, the ground terminal 18 and the lead-out terminal 20 of the one coil electrode 14 and the ground terminal 22 and the lead-out terminal 24 of the other coil electrode 16 are formed at the opposite ends of the first dielectric layer 12.

On the other main surface side of the first dielectric layer 12, a planar first ground electrode 26 is formed. The first ground electrode 26 has two coil electrodes 14 and 1 having outer dimensions.
It is formed so as to be larger than the outer dimension including 6. Then, the coil electrodes 14 and 16 and the first ground electrode 26
Are formed so as to face each other with the first dielectric layer 12 interposed therebetween. 2 so as to extend from the first ground electrode 26 toward opposite ends of the first dielectric layer 12.
Two ground terminals 28, 30 are formed. Ground terminal 2
8 is formed at a position corresponding to the ground terminal 18 of one coil electrode 14, and the ground terminal 30 is the other coil electrode 1
6 is formed at a position corresponding to the ground terminal 22. Then, the first ground electrode 26 is covered with the protective layer 32.

Further, the first electrode is sandwiched between the coil electrodes 14 and 16.
A second dielectric layer 34 is formed on the opposite side of the dielectric layer 12. The thickness of the second dielectric layer 34 is adjusted within the range of 1000 μm or less, similarly to the first dielectric layer 12. A second ground electrode 36 is formed on the second dielectric layer 34. The outer dimensions of the second ground electrode 36 are formed to be the same as the outer dimensions of the first ground electrode 26. 2 so as to extend from the second ground electrode 36 toward the opposite ends of the second dielectric layer 34.
Two ground terminals 38, 40 are formed. Ground terminal 3
8 is formed at a position corresponding to the ground terminal 18 of one coil electrode 14, and the ground terminal 40 is the other coil electrode 1
6 is formed at a position corresponding to the ground terminal 22. Second
A protective layer 42 is formed on the ground electrode 36.

The ground terminal 18 of the coil electrode 14, the ground terminal 28 of the first ground electrode 26, and the ground terminal 38 of the second ground electrode 36 are connected by an external ground electrode 44. In addition, the ground terminal 22 of the coil electrode 16, the first
The ground terminal 30 of the ground electrode 26 and the ground terminal 40 of the second ground electrode 36 are
Connected by. Further, the opposite ends of the first dielectric layer 12, the second dielectric layer 34, and the protective layers 32 and 42 are
Two external extraction electrodes 48 and 50 are formed, and these external extraction electrodes 48 and 50 are connected to the extraction terminal 20 of one coil electrode 14 and the extraction terminal 24 of the other coil electrode 16.

To produce such a bandpass filter 10, as shown in FIG. 3, a ceramic green sheet 50 made of a plurality of dielectric materials is prepared. 1
Two coil electrode patterns 52 are formed on one sheet 50 by using, for example, a copper paste or the like. These coil electrode patterns 52 are formed so as to have a shape of a part of the loop. The openings of these coil electrode patterns 52 are arranged in the same direction. Further, from the coil electrode pattern 52 to the sheet 50
A ground terminal pattern 54 and a take-out terminal pattern 56 are formed so as to extend to the end portion of. These ground terminal pattern 54 and lead terminal pattern 56
Are formed on both of the two coil electrode patterns 52. Then, the ground terminal pattern 54 and the take-out terminal pattern 5 formed on one of the coil electrode patterns 52.
6 and the ground terminal pattern 54 and the takeout terminal pattern 56 formed on the other coil electrode pattern 52 are formed so as to extend to the opposite ends of the sheet 50.

A first ground electrode pattern 58 is formed on another sheet 50. The first ground electrode pattern 58 is formed in a planar shape on the sheet 50. Then, two ground terminal patterns 60 are formed so as to extend from the first ground electrode pattern 58 to the opposite ends of the sheet 50. The two ground terminal patterns 60 extend from the coil electrode pattern 52.
It is formed at a position corresponding to one ground terminal pattern 54.

A second ground electrode pattern 62 is formed on yet another sheet 50. Then, two ground terminal patterns 64 are formed so as to extend from the second ground electrode pattern 62 to the opposite ends of the sheet 50. The two ground terminal patterns 64 are formed at positions corresponding to the two ground terminal patterns 54 extending from the coil electrode pattern 52.

A plurality of sheets 50 are sandwiched between the sheets 50 on which the respective electrode patterns are formed so that the thickness of the dielectric layers 12 and 34 can be obtained. Further, another sheet 50 is placed on the sheet 50 on which the second ground electrode pattern 62 is formed. These sheets 50 are laminated and pressure-bonded to form a molded body. Further, two external ground electrode patterns and two external extraction electrode patterns are formed on the end portion of the obtained molded body by using copper paste or the like. Then, by these external ground electrode patterns, the ground terminal pattern 54 of the coil electrode pattern 52 and the first ground electrode pattern 5 are formed.
The ground terminal pattern 60 of 8 and the ground terminal pattern 64 of the second ground electrode pattern 62 are connected. Further, the external extraction electrode patterns are formed so as to be connected to the two extraction terminal patterns 56, respectively. The bandpass filter 10 is obtained by firing this molded body. The electrode patterns formed on the outer surface of the molded body may be formed after firing the molded body.

In this bandpass filter 10, as shown in the equivalent circuit of FIG. 4, two resonators having an inductance component and a capacitance component are electromagnetically coupled. Here, the coil electrodes 14 and 16 are connected to the first ground electrode 26 and the second ground electrode 36, and the length of the coil electrodes 14 and 16 is the length L shown in Formula 1.
Therefore, each resonator shown in FIG. 4 acts as a quarter-wave stripline dielectric resonator. In FIG. 4, L is the inductance component due to the coil electrodes 14 and 16, C is the stray capacitance between the coil electrodes 14 and 16 and the ground electrodes 26 and 36, and M is the mutual inductance component between the two resonators. Is.

In such a bandpass filter 10,
By changing the thicknesses of the first dielectric layer 12 and the second dielectric layer 34 within the range of 1000 μm or less, the capacitance component can be equivalently changed. Thereby, the impedance of the bandpass filter 10 can be adjusted. For example, when the thickness of each of the dielectric layers 12 and 34 is 600 μm, the bandpass filter 10
Has an impedance of 44.3Ω, and each dielectric layer 1
The impedance of the bandpass filter 10 is 38.1Ω when the thickness of the layers 2, 34 is 700 μm, and the impedance of the bandpass filter 10 is 35.9Ω when the thickness of the dielectric layers 12, 34 is 800 μm. there were. In this way, the impedance of the bandpass filter 10 can be adjusted by changing the thickness of each of the dielectric layers 12 and 34, and impedance matching with the circuit incorporating the bandpass filter 10 can be achieved. The thickness of each of the dielectric layers 12 and 34 can be easily adjusted by changing the number of laminated green sheets 50 during manufacturing. Moreover, if the thickness of the sheet 50 is accurately formed, the thickness of each of the dielectric layers 12 and 34 can be adjusted accurately.

The coil electrodes 14 and 16 may have a perfect loop shape as shown in FIG.
Further, as shown in FIG. 6, a part of the loop may be formed in a cut shape so that the cuts of the coil electrodes 14 and 16 are arranged inside each other. Further, as shown in FIG. 7, the cuts of the loop may be arranged outside each other, or as shown in FIG. 8, the cuts of the loop may be arranged in the same direction.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

FIG. 2 is an exploded perspective view of the bandpass filter shown in FIG.

FIG. 3 is an exploded perspective view showing one step of manufacturing the bandpass filter shown in FIG.

FIG. 4 is an equivalent circuit diagram of the bandpass filter shown in FIG.

5 is a plan view showing a modification of the coil electrode of the bandpass filter shown in FIG.

6 is a plan view showing another modified example of the coil electrode of the bandpass filter shown in FIG.

FIG. 7 is a plan view showing still another modification of the coil electrode of the bandpass filter shown in FIG.

8 is a plan view showing another modified example of the coil electrode of the bandpass filter shown in FIG.

FIG. 9 is an exploded perspective view showing an example of a conventional bandpass filter which is the background of the present invention.

[Explanation of symbols]

 10 band pass filter 12 1st dielectric layer 14 coil electrode 16 coil electrode 18 earth terminal 20 extraction terminal 22 earth terminal 24 extraction terminal 26 1st earth electrode 34 2nd dielectric layer 36 2nd earth electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location H01P 11/00 G

Claims (1)

[Claims] 1. A dielectric layer, two coil electrodes having a loop shape or a part of a loop formed on one main surface side of the dielectric layer, and formed on the other main surface side of the dielectric layer. A ground electrode, a ground terminal drawn from the coil electrode and the ground electrode for connecting the coil electrode and the ground electrode, and a take-out terminal drawn from the coil electrode at a distance from the ground terminal; The ground terminal and the lead-out terminal drawn out from the coil electrode and the ground terminal and the take-out terminal drawn out from the other coil electrode are formed in directions opposite to each other, and the two coil electrodes and the ground electrode A bandpass filter in which the thickness of the dielectric layer in between is 1000 μm or less.