JP2988500B2 - Bandpass filter - Google Patents

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 having a pass band in, for example, a several GHz band.

[0002]

2. Description of the Related Art As a conventional bandpass filter, for example, there has been a bandpass filter in which a plurality of resonators are electromagnetically coupled. As a resonator for forming a band-pass filter, for example, there is a stripline resonator having a half wavelength as shown in FIGS. In the resonator 1, a line electrode 3 having both ends opened is formed on one main surface of a dielectric substrate 2, and a ground electrode is formed on the entire surface of the other main surface of the dielectric substrate 2. In such a resonator 1, when the wavelength is λ and the effective permittivity of the dielectric substrate 2 is ε, the length L ₁ of the line electrode 3 is given by the following equation (1).

[0003]

(Equation 1)

[0004] Further, as shown in FIG.
There is a quarter-wavelength resonator in which one end of the line electrode 3 is connected to the ground electrode so as to wrap around from the end. The length L ₂ of the line electrode 3 of the resonator 1 is given by the following equation (2).

[0005]

(Equation 2)

Further, as shown in FIG.
There is a resonator in which a spiral conductive pattern 4 is formed on one main surface. In this resonator 1, a ground electrode 5 is formed on the other main surface of the dielectric layer 2 so as to face the conductor pattern 4. Further, an earth extraction electrode 6 connected to the earth electrode 5 is extracted from one end of the conductor pattern 4, and an extraction electrode 7 is formed at an interval from the earth extraction electrode 6. In this resonator 1, since the conductor pattern 4 is formed in a spiral shape, even if the conductor pattern 4 is made longer,
Miniaturization is possible. By forming these resonators in parallel and electromagnetically coupling, a bandpass filter can be obtained.

[0007]

SUMMARY OF THE INVENTION However, 1/2
For a wavelength resonator or a quarter wavelength resonator, for example,
In a 3 GHz resonator, the line electrode becomes long, and the bandpass filter becomes large. Further, the band-pass filter using the conductive pattern, since the conductor pattern is spiral, mutually influence flux between adjacent lines, guide
It becomes difficult for current to flow through the body pattern . Therefore, the substantial resistance increases, the Q decreases, and the insertion loss of the bandpass filter increases. When the size of the band-pass filter is reduced, the distance between adjacent lines of the conductor pattern is reduced, and the influence of magnetic flux between the lines is increased.

[0008] Therefore, a main object of the present invention is to provide a bandpass filter which can be miniaturized and has a small insertion loss even if it is miniaturized.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a plurality of conductor patterns formed on a plurality of dielectric layers and connected to each other to form a plurality of helical electrodes which are electromagnetically coupled.
Apart and over emissions, from one of the conductor patterns <br/> forming each spiral electrode and the ground lead electrode drawn out to an end of the dielectric layer, apart from the grounding lead electrode, ground and the lead electrode from the conductive pattern that is formed of use lead electrodes are led out to the end of the dielectric layer, facing the shield electrode at a conductor pattern and spacing on both sides of the plurality of conductive patterns, a plurality of spiral electrodes and the shield A capacitor electrode formed between the electrode and the shield electrode, and electrically connected to an end of a conductor pattern forming each spiral electrode through a through hole formed in the dielectric layer. And each of the conductor putters
Emission is formed such that one turn or less turns on the dielectric layer, and is a ground lead electrode and the shield electrode is electrically connected, a band-pass filter.

[0010]

The dielectric layers on which the conductor patterns are formed are laminated, and these conductor patterns are connected to form a plurality of electromagnetically coupled spiral electrodes. In this case, in one spiral electrode, a dielectric layer exists between adjacent lines. Also, by forming a capacitor electrode between the spiral electrode and the shield electrode,
An electrostatic capacitance is formed between the capacitor electrode and the shield electrode.

[0011]

Effects of the Invention According to the present invention, since the electromagnetically coupled plurality of spiral electrodes by a plurality of conductor patterns <br/> is formed, adjusting the number of the formed dielectric layer conductor pattern By doing so, the length of the spiral electrode can be adjusted. In this case, even if the spiral electrode is lengthened, the bandpass filter does not become large unlike the case where the electrode is formed on one plane. Moreover, looking for one of the spiral electrodes, between adjacent conductor patterns due to the presence of the dielectric layer can be secured a distance corresponding to the thickness of the conductor
The effect of the magnetic flux between the patterns can be reduced. Therefore, the size of the bandpass filter can be reduced without lowering the Q. Then, since a decrease in Q can be prevented, the insertion loss of the band-pass filter can be reduced. Further, by forming a capacitance between the capacitor electrode and the shield electrode, the frequency of the pass band can be reduced, and the pass band of the band pass filter can be adjusted.

Further, the shielding property in a high frequency region can be improved by the shield electrode. Further, the impedance of the bandpass filter can be adjusted by changing the distance between the ground extraction electrode and the extraction electrode. Therefore, a bandpass filter can be manufactured in consideration of impedance matching with an external circuit.

The above 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.

[0014]

FIG. 1 is a perspective view showing an embodiment of the present invention. The bandpass filter 10 includes a laminate 12. The stacked body 12 includes a first dielectric layer 14, as shown in FIG. On the first dielectric layer 14, the first shield electrode 1
6 are formed. The first shield electrode 16 is formed on almost the entire surface of the first dielectric layer 14. Then, from the first shield electrode 16, the opposing 2
Toward one end, four ground extraction electrodes 18a,
18b, 18c and 18d are pulled out.

On the first shield electrode 16, a second dielectric layer 20 is disposed. On the second dielectric layer 20,
Two first conductor patterns 22a and 22b are formed. One first conductive pattern 22a is formed in a U-shape in a substantially half area of one main surface of the second dielectric layer 20. Also, the other first conductor pattern 22b
Is formed in a U-shape in a direction opposite to the first conductor pattern 22a in the remaining half area of the one main surface of the second dielectric layer 20. These first conductor patterns 22a,
From one end of 22b, ground extraction electrodes 24a and 24b are formed toward the opposite ends of the second dielectric layer 20, respectively. Further, the first conductor pattern 22
The extraction electrodes 26a and 26b are drawn out from the intermediate portions of the first and second a and 22b toward the other opposite end of the second dielectric layer 20, respectively. In this embodiment, the extraction electrode 26
a, 26b are drawn out to the end of the second dielectric layer 20 adjacent to the end from which the ground lead-out electrodes 24a, 24b are drawn out. That is, the first conductor patterns 22a, 22
b is formed so as to face the first shield electrode 16, and the ground extraction electrodes 18a and 24a and the ground extraction electrodes 18d and 24b are formed so as to oppose each other. In addition, the extraction electrodes 26a and 26b are drawn out to ends corresponding to portions where no electrodes are formed.

A third dielectric layer 28 is formed on the first conductor patterns 22a and 22b. Second conductor patterns 30a and 30b are formed on third dielectric layer 28. The second conductor patterns 30a and 30b are formed so as to have a U-shape in opposite directions. Also, one second conductor pattern 30a is the first conductor pattern 2
2a is formed in a U-shape opposite to the second conductor path.
The turn 30b is formed in a U-shape opposite to the first conductor pattern 22b. Second conductor patterns 30a, 30b
At one end, through holes 32a and 32b are formed to penetrate the third dielectric layer 28, respectively. Then, the first conductor path is inserted through the through hole 32a.
The other end of the turn 22a and one end of the second conductor pattern 30a is connected, the first conductor through the through hole 32b
The other end of the pattern 22b is connected to one end of the second conductor pattern 30b.

A fourth dielectric layer 34 is formed on the second conductor patterns 30a and 30b. Third conductive patterns 36a and 36b are formed on fourth dielectric layer 34. The third conductor patterns 36a and 36b are formed so as to have a U-shape in opposite directions. Also, one of the third conductor pattern 36a and the second conductor pattern 3
0a, and is formed in a U-shape opposite to the third conductor path.
The turn 36b is formed in a U-shape which is opposite to the second conductor pattern 30b. That is, the third conductor pattern 36
a and 36b are the first conductor patterns 22a and 22b, respectively.
It is formed so as to have a U-shape in the same direction as 2b. Third
Through holes 38a and 38b are formed at one ends of the conductor patterns 36a and 36b so as to penetrate the fourth dielectric layer 34, respectively. The other end of the second conductor pattern 30a and one end of the third conductor pattern 36a are connected via the through hole 38a, and the other end of the second conductor pattern 30b and the third end of the third conductor pattern 30a are connected via the through hole 38b. One end of the conductor pattern 36b is connected. Thus, the first conductor pattern 22a and the second conductor pattern
Emissions 30a, by connecting a third conductor pattern 36a, one of the spiral electrodes are formed. Also, the first
The conductor pattern 22b, the second conductor pattern 30b, the third
The other helical electrode is formed by connecting the conductor pattern 36b. These two spiral electrodes are formed so as to be wound in the same direction. And 2
The two spiral electrodes are electromagnetically coupled by being formed adjacent to each other.

A fifth dielectric layer 60 is disposed on the third conductor patterns 36a and 36b. Then, on the fifth dielectric layer 60, planar capacitor electrodes 62a and 62b are formed. Capacitor electrodes 62a, 62
b is formed at a position facing the third conductor patterns 36a and 36b, respectively. A through hole 64a is formed so as to penetrate the fifth dielectric layer 60 from the capacitor electrode 62a, and a through hole 64b is formed so as to penetrate the fifth dielectric layer 60 from the capacitor electrode 62b.
Is formed. The capacitor electrode 62a and the third conductor pattern 36a are connected through the through hole 64a, and the capacitor electrode 6a is connected through the through hole 64b.
2b and the third conductor pattern 36b are connected.

A sixth dielectric layer 40 is disposed on the capacitor electrodes 62a and 62b. A second shield electrode 42 is formed on the sixth dielectric layer 40 so as to face the capacitor electrodes 62a and 62b. The second shield electrode 42 is formed in the same shape as the first shield electrode 16. The second shield electrode 42 to the sixth
Four ground extraction electrodes 44a, 44b, 44c and 44d are formed toward the end portion facing the dielectric layer 40 of FIG. These ground extraction electrodes 44a to 44d
Are formed at positions corresponding to the ground extraction electrodes 18 a to 18 d formed on the first shield electrode 16. On this second shield electrode 42, a seventh dielectric layer 46 is formed. Then, a laminate 12 is formed in a state where these dielectric layers are laminated.

The external terminals 48a,
48b, 48c, 48d, 48e, 48f, 48g, 4
8h, 48i and 48j are formed. External terminals 48a,
48b is connected to the ground lead electrode 18a formed on the first shield electrode 16 and the ground lead electrode 44a formed on the second shield electrode 42. In particular, the external terminal 48b is simultaneously connected to the first conductor pattern 22a. Is also connected to the ground extraction electrode 24a formed at the bottom. External terminal 4
Reference numerals 8c and 48d denote an earth extraction electrode 18b formed on the first shield electrode 16 and a second shield electrode 42.
Is connected to the ground lead-out electrode 44b formed at the bottom. The external terminal 48e is connected to the extraction electrode 26b formed on the first conductor pattern 22b. External terminals 48f, 48
g is connected to the ground lead electrode 18d formed on the first shield electrode 16 and the ground lead electrode 44d formed on the second shield electrode 42.
8g is also connected to the ground lead electrode 24b formed on the first conductor pattern 22b at the same time. External terminal 48
h and 48i are connected to the ground extraction electrode 18c formed on the first shield electrode 16 and the ground extraction electrode 44c formed on the second shield electrode 42. The external terminal 48j is connected to the extraction electrode 26a formed on the first conductor pattern 22a.

To manufacture the bandpass filter 10, a plurality of ceramic green sheets 50 made of a dielectric material, that is, an insulating material are prepared as shown in FIG. And a plurality of ceramic green sheets 5
0, the first shield electrode 16 and the ground extraction electrode 1
8a to 18d, first conductor patterns 22a and 22b, ground extraction electrodes 24a and 24b, extraction electrodes 26a and 26
b, the second conductive patterns 30a, 30b, the third conductor path
Turns 36a, 36b, capacitor electrodes 62a, 62
b, second shield electrode 42 and ground extraction electrode 4
The paste layer 52 is formed by printing, for example, a conductive paste on the shapes 4a to 44d. Further, through holes 54 are formed at the ends of the paste layer 52 corresponding to the second conductor patterns 30a, 30b, the third conductor patterns 36a, 36b, and the capacitor electrodes 62a, 62b so as to penetrate the ceramic green sheet 50. Is formed. Then, by inserting a conductive paste or the like into these through holes 54, the first conductor pattern 22a, the second conductor pattern 30a, and the third conductor pattern are formed.
The paste layer 52 corresponding to the conductor 36a and the capacitor electrode 62a is connected to the first conductor pattern 22.
b, second conductor pattern 30b, third conductor pattern 3
6b and the paste layer 52 corresponding to the capacitor electrode 62b are connected. Then, a required number of ceramic green sheets 50 are sandwiched so that the thickness of each dielectric layer is obtained, and the respective ceramic green sheets 50 are laminated.
The compact is obtained by pressing.

A conductive paste is applied to the molded body so as to have the shape of the external electrodes 48a to 48j. These conductive pastes are connected to necessary paste layers 52 inside the molded body. Then, by firing this molded body, the bandpass filter 10 is obtained. Before applying the conductive paste corresponding to the external electrodes 48a to 48j, the molded body is fired, and thereafter, the external electrodes 48a to 48j are fired.
~ 48j may be printed.

In this band pass filter 10, one first conductive pattern 22a and two shield electrodes 16,
42 are connected via ground extraction electrodes 18a, 24a, 44a and an external electrode 48b, and the other first conductor
Since the pattern 22b and the two shield electrodes 16 and 42 are connected via the ground extraction electrodes 18d, 24b and 44d and the external electrode 48g, the two spiral electrodes function as a quarter-wavelength resonator. Since the two spiral electrodes are formed close to each other, they are electromagnetically coupled. In this bandpass filter 10, each conductor pattern 22a, 30a, 36a and each conductor pattern 22b,
An inductance is formed by the spiral electrode portion formed by 30b and 36b. In addition, each conductor pattern 22a, 2
A slight capacitance is formed between 2b, 30a, 30b, 36a, 36b and the two shield electrodes 16, 42. Further, the capacitor electrode 62a and the first and second
Between the first and second shield electrodes 16, 42, and between the capacitor electrode 62b and the first and second shield electrodes 16, 42.
And a capacitance is formed between them. Therefore, the equivalent circuit of the bandpass filter 10 shown in FIG. 1 has two circuits in which an inductance and two capacitances are connected in parallel, as shown in FIG. Are electromagnetically coupled to each other. FIG. 5 shows an example of the frequency characteristic of the band-pass filter 10. In this frequency characteristic, a pass band exists at about 1.6 GHz.

In the band pass filter 10, the conductor path
By adjusting the number of dielectric layers in which the turns are formed, the length of the spiral electrode can be freely adjusted.
Therefore, the resonance frequency of each resonator can be freely designed, and thereby the frequency of the pass band of the band-pass filter 10 can be adjusted. Further, in the manufacturing process of the band-pass filter, the processing process can be simplified because of the alternately stacked structure of the same pattern.

Further, since the band-pass filter 10 has a laminated structure, the band-pass filter 10 can be downsized even if the spiral electrode becomes long. That is, in the bandpass filter 10 of the present invention, the conductor patterns 22a,
Since a spiral electrode is formed by 22b, 30a, 30b, 36a, and 36b, in one spiral electrode,
Adjacent lines of the conductor pattern are located in the stacking direction via the dielectric layer. Therefore, even if the spiral electrode becomes long, it is not necessary to enlarge the dielectric layer on which the conductor pattern is formed, and the bandpass filter 10 can be downsized. At this time, since the distance between the adjacent conductor patterns is ensured by the dielectric layer, the decrease in Q due to the influence of the magnetic flux is small, and the insertion loss of the bandpass filter 10 can be reduced.

The distance between the ground lead-out electrode 24a formed on the first conductor pattern 22a and the lead-out electrode 26a, and the distance between the ground lead-out electrode 24b formed on the second conductor pattern 22b and the lead-out electrode 26b By adjusting the distance between the two, the impedance of the bandpass filter 10 can be adjusted. In the above embodiment, the ground extraction electrodes 24a, 24b and the extraction electrodes 26a, 26
b were drawn out toward different ends of the second dielectric layer 20, respectively. However, the ground extraction electrode 24a and the extraction electrode 26a may be drawn out to the same end, and the ground extraction electrode 24b and the extraction electrode 26b may be drawn out to the same end. It may be drawn out to a part. Furthermore, conductor pattern 2
2a, 22b, 30a, 30b, 36a, to adjust the line width of 36b, these conductors patterns and the shield electrode 1
The impedance can also be adjusted by adjusting the distance between 6,6. Thus, since the adjustment of the impedance of the bandpass filter 10 is simple, the bandpass filter can be manufactured in consideration of impedance matching with an external circuit.

Also, by changing the area of the capacitor electrodes 62a, 62b or changing the thickness of the dielectric layer 40 between the capacitor electrodes 62a, 62b and the second shield electrode 42, the shield between the capacitor electrodes 62a, 62b The capacitance formed between the electrodes 16 and 42 can be changed. Thus, the capacitor electrodes 62a, 6a
By changing the capacitance between 2b and the shield electrodes 16 and 42, the pass band of the bandpass filter 10 can be adjusted.

Further, the conductor patterns 22a, 22b, 3
0a, 30b, 36a, 36b
Since the layers 6, 42 are formed, the shielding performance in a high frequency range is good, and stable characteristics can be obtained.

Further, as shown in FIG. 6, the first conductor pattern
Lead 22a of the ground 22a and the first conductor pattern.
A ground lead electrode 24b of over emissions 22b, may be drawn out toward to the same end of the second dielectric layer 20. In this case, the two spiral electrodes formed are wound in mutually different directions. Even in such a case, the two spiral electrodes are electromagnetically coupled to form the bandpass filter 10. FIG. 7 shows the frequency characteristics of the bandpass filter 10. As can be seen from FIG. 7, this band-pass filter 10 also has a pass band around about 1.6 GHz, but the attenuation on the low frequency side is larger than the characteristic in FIG. The amount is getting smaller.

In each of the embodiments described above, two spiral electrodes are formed, but three or more spiral electrodes may be formed. In this case, to form a three or more conductor patterns on one dielectric layer, these conductors patterns
The dielectric layers may be stacked such that the layers are connected in the stacking direction. Of course, these spiral electrodes are electromagnetically coupled to each other.

[Brief description of the drawings]

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

FIG. 2 is an exploded perspective view showing a laminated body of the bandpass filter shown in FIG.

FIG. 3 is an illustrative view showing one portion of a manufacturing process of the bandpass filter shown in FIG. 1;

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

FIG. 5 is a graph showing frequency characteristics of the bandpass filter shown in FIG.

FIG. 6 is a perspective view showing a modification of the bandpass filter shown in FIG.

FIG. 7 is a graph showing frequency characteristics of the bandpass filter shown in FIG.

FIG. 8 is a plan view showing an example of a resonator used in a conventional bandpass filter as a background of the present invention.

FIG. 9 is a plan view showing a modification of the resonator shown in FIG.

FIG. 10 is a plan view showing another example of a resonator used in a conventional bandpass filter.

FIG. 11 is a plan view showing still another example of the resonator used in the conventional bandpass filter.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Band pass filter 12 Laminated body 14 1st dielectric layer 16 1st shield electrode 20 2nd dielectric layer 22a, 22b 1st conductor pattern 24a, 24b Grounding | leading-out electrode 26a, 26b Extraction electrode 28 3rd Dielectric layers 30a, 30b Second conductor pattern 34 Fourth dielectric layer 36a, 36b Third conductor pattern 40 Sixth dielectric layer 42 Second shield electrode 46 Seventh dielectric layer 60 Fifth Dielectric layer 62a, 62b capacitor electrode

Claims (1)

(57) [Claims] 1. A formed on the plurality of dielectric layer, a plurality of conductive patterns comprising a plurality of helical electrodes which are electromagnetically coupled by being connected together, the conductor forming each of the spiral electrode A ground extraction electrode that is drawn out from one of the patterns to the end of the dielectric layer, spaced apart from the ground extraction electrode, from the conductor pattern on which the ground extraction electrode is formed extraction electrodes to be drawn to the ends of said dielectric layer, said conductor pattern on both sides of the plurality of the conductor patterns
It is formed so as to face the shield electrode between the shield electrode facing at a down and spacing, and a plurality of the spiral electrode and the shield electrode, and through a through hole formed in the dielectric layer And a capacitor electrode electrically connected to an end of the conductor pattern forming each of the spiral electrodes. Each of the conductor patterns is formed to have one or less turns on the dielectric layer. And the ground extraction electrode and the shield electrode are electrically connected,
Bandpass filter.