JP2004153414A - Low-pass filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-pass filter which has two attenuation poles with high design flexibility and can downsize the whole shape. <P>SOLUTION: This filter comprises a 1st ground electrode 5 on a lower surface of a 1st dielectric layer 1; a 2nd ground electrode 6 between a 2nd and a 3rd dielectric layers 2, 3; a 1st capacitor electrode 7 facing the 1st, 2nd ground electrodes 5, 6, respectively, between the 1st, 2nd dielectric layers 1, 2; a 2nd and a 3rd capacitor electrodes 8, 9 facing the 2nd ground electrode 6, respectively, between the 3rd and a 4th dielectric layers 3, 4; and 1st, 2nd coil electrodes 10, 11 on an upper surface of the 4th dielectric layer 4. Between one ends of the 1st, 2nd coil electrodes 10, 11 are connected to the 1st capacitor electrode 7, the other ends of the 1st coil electrode 10 is connected to the 2nd capacitor electrode 8 to be an input terminal, and the other end of the 2nd coil 11 is connected to the 3rd capacitor electrode 9 to be an output terminal. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a low-pass filter mainly used in an electronic circuit of an electronic device such as a mobile phone or mobile communication in a frequency band of about 1 to 3 GHz, and more particularly to a plurality of low-pass filters formed with a ground electrode, a capacitor electrode, or a coil electrode. And a low-pass filter formed by laminating the dielectric layers described above.
[0002]
[Prior art]
Regarding low-pass filters used in electronic circuits of electronic devices such as mobile phones and mobile communication in a frequency band of about 1 to 3 GHz, there is a demand for downsizing, higher density, and lower price of the electronic devices in which they are used. As they increase, miniaturization and densification are also required.
[0003]
As such a low-pass filter, for example, JP-A-7-273502 discloses a dielectric substrate having a microstrip line on the surface and a dielectric substrate having a capacitor electrode on the surface, and a dielectric sheet and a ground electrode on the surface. In a low-pass filter sandwiched and laminated with a dielectric substrate having a microstrip line and a capacitor electrode and a ground electrode formed on the side surface, a dielectric substrate having a microstrip line and a capacitor electrode are provided. There is disclosed a low-pass filter in which a dielectric substrate having a shield electrode electrically connected to a ground electrode is inserted between the dielectric substrate and the dielectric substrate.
[0004]
According to this, a stray capacitance generated at both ends of a microstrip line is inserted between a dielectric substrate having a microstrip line and a dielectric substrate having a capacitor electrode, by inserting a shield electrode conducting to a ground electrode on the surface. Therefore, the amount of attenuation in the high-frequency band after passing through the low-pass filter can be kept high, and unnecessary harmonics can be removed.
[0005]
In addition, a new capacitor is generated between the capacitor electrode and the shield electrode, and is added in parallel with the capacitor between the capacitor electrode and the ground electrode, so that the total capacitance of the capacitor is doubled and the shape is reduced. The resonance frequency of the low-pass filter can be lowered without any change, and when the resonance frequency is constant, the shape of the low-pass filter can be reduced.
[0006]
[Patent Document 1]
JP-A-7-273502
[0007]
[Problems to be solved by the invention]
However, in the low-pass filter disclosed in Japanese Patent Application Laid-Open No. 7-273502, the stray capacitance generated at both ends of the microstrip line can be reduced, so that the attenuation in the high-frequency band after passing through the low-pass filter is kept high. Although unnecessary harmonics can be removed, a new capacitor is generated between the capacitor electrode and the shield electrode to reduce the resonance frequency in order to reduce the size of the low-pass filter in order to reduce the size. However, since the resonance frequency is generated by the coil electrode and the capacitor electrode of the entire low-pass filter, there is a problem that it is difficult to lower the resonance frequency unless the coil electrode and the capacitor electrode are increased to some extent. Was.
[0008]
Further, since the resonance frequency is generated by the coil electrode and the capacitor electrode of the entire low-pass filter, there is a problem that only one arbitrary resonance frequency can be generated.
[0009]
Although the total capacitance of all capacitors is generated between the capacitor electrode and the ground electrode and between the capacitor electrode and the shield electrode, the largest capacitance, that is, the capacitor electrode that requires miniaturization However, only the capacitor electrode connected to the portion where the microstrip lines are connected to each other is required. However, since all the capacitor electrodes are arranged on the same dielectric surface, there is a problem that it is difficult to reduce the size.
[0010]
The present invention has been devised in view of the above-mentioned problems of the prior art, and has as its object to reduce the resonance frequency and provide any two resonance frequencies, that is, two attenuation poles. An object of the present invention is to provide a low-pass filter that can be miniaturized and is preferably used in a high-frequency band of about 1 to 3 GHz.
[0011]
[Means for Solving the Problems]
The low-pass filter according to the present invention includes a first to a fourth dielectric layers sequentially laminated, a first ground electrode formed on a lower surface of the first dielectric layer, and the second and third dielectric layers. A second ground electrode formed between the layers; a first capacitor electrode formed between the first and second dielectric layers and facing the first and second ground electrodes; And second and third capacitor electrodes formed between the four dielectric layers and opposed to the second ground electrode, respectively, and first and second coil electrodes formed on the upper surface of the fourth dielectric layer. And connecting one end of the first and second coil electrodes to each other and electrically connecting the one end to the first capacitor electrode, and connecting the other end of the first coil electrode to the other end of the first coil electrode. The second capacitor electrode An input terminal while connecting, is characterized in that the other end of the second coil electrode and the output terminal with connecting the third capacitor electrode electrically.
[0012]
Further, in the low-pass filter according to the present invention, in the above-described configuration, the input terminal and the output terminal are led out to a lower surface of the first dielectric layer.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
According to the low-pass filter of the present invention, the first to fourth dielectric layers sequentially laminated, the first ground electrode formed on the lower surface of the first dielectric layer, and the second and third dielectric layers A second ground electrode formed between the layers, a first capacitor electrode formed between the first and second dielectric layers and facing the first and second ground electrodes, and a third and fourth dielectric layer. A second capacitor electrode formed between the body layers and facing the second ground electrode, and a first and a second coil electrode formed on the upper surface of the fourth dielectric layer; One ends of the first and second coil electrodes are connected to each other, the one end is electrically connected to the first capacitor electrode, and the other end of the first coil electrode is electrically connected to the second capacitor electrode. Input and input And the other end of the second coil electrode is electrically connected to the third capacitor electrode and a low-pass filter is configured as an output terminal. Therefore, the first coil electrode (L1) and the first coil electrode An attenuation pole which is connected to both ends of (L1) and which is developed by a parallel resonance circuit formed by a capacitor (C4) formed between the first capacitor electrode and the second capacitor electrode, and a second coil A parallel resonance circuit including an electrode (L2) and a capacitor (C5) formed between the first and third capacitor electrodes, which is connected to both ends of the second coil electrode (L2). Can be arbitrarily set by changing the size of the coil electrode and the capacitors connected to both ends of the coil electrode. In other words, the capacitor electrode can be made smaller if the coil electrode is to be made larger, and the coil electrode can be made smaller if the capacitor electrode is to be made larger.By appropriately setting the size of the coil electrode and the capacitor electrode, the entire low-pass filter can be made. The attenuation pole can be reduced without increasing the size of the coil electrode and the capacitor electrode.
[0014]
Further, by connecting two parallel resonance circuits in series in this manner, two arbitrary attenuation poles can be provided. Further, among the first to third capacitor electrodes, the first capacitor electrode which is the largest in the configuration of a commonly used low-pass filter such as a Butterworth-type, Bessel-type, or Chebyshev-type is used as the first and second capacitor electrodes. Since the first capacitor electrode and the first and second ground electrodes are formed between the dielectric layers so as to face the first and second ground electrodes, the magnitude of the ground capacitance C1 formed with the first capacitor electrode and the first and second ground electrodes facing each other is reduced. The size can be reduced to approximately half the size required when facing only one ground electrode. Further, when viewed from the stacking direction, the first capacitor electrode and the second and third capacitor electrodes can be overlapped, so that the entire low-pass filter can be reduced in size.
[0015]
Further, when the input terminal and the output terminal are led out to the lower surface of the first dielectric layer, the low-pass filter can be mounted on an external electric circuit board as a surface-mounted electronic component.
[0016]
Hereinafter, a low-pass filter of the present invention will be described with reference to the drawings.
[0017]
FIG. 1 is an exploded perspective view showing an example of a low-pass filter according to an embodiment of the present invention. In FIG. 1, 1 is a first dielectric layer, 2 is a second dielectric layer, 3 is a third dielectric layer, 4 is a fourth dielectric layer, 5 is a first ground electrode, 6 is A second ground electrode, 7 is a first capacitor electrode, 8 is a second capacitor electrode, 9 is a third capacitor electrode, 10 is a first coil electrode, 11 is a second coil electrode, and 12 is a first coil electrode. , 13 is a second through conductor, and 14 is a third through conductor.
[0018]
In the example shown in FIG. 1, a first ground electrode 5 formed on the lower surface of the first dielectric layer 1 and a second ground electrode 5 formed between the second dielectric layer 2 and the third dielectric layer 3 are formed. Between the first ground electrode 6 and the first capacitor electrode 7 formed between the first dielectric layer 1 and the second dielectric layer 2 and opposed to the first ground electrode 5 and the second ground electrode 6. A second capacitor electrode 8 and a third capacitor formed between the third dielectric layer 3 and the fourth dielectric layer 4 and opposed to the second ground electrode 6, respectively, where C1 is a ground capacitance generated therebetween. The ground capacitances generated between the first and second electrodes 9 and 11 are C2 and C3, respectively, and the inductances generated by the first coil electrode 10 and the second coil electrode 11 formed on the upper surface of the fourth dielectric layer 4 are L1 and L2, respectively. And the first condition The second capacitor electrode 8 and the third capacitor electrode 9 are formed so as to face each other via the second dielectric layer 2, the second ground electrode 6, and the third dielectric layer 3. Are C4 and C5, respectively.
[0019]
In the example shown in FIG. 1, one end of the first coil electrode 10 and one end of the second coil electrode 11 are connected to each other, and a first capacitor electrode that generates a ground capacitance C1 via the first through conductor 12, for example. 7, and the other end of the first coil electrode 10 is electrically connected to the second capacitor electrode 8 which generates the ground capacitance C2 via, for example, the second through conductor 13 to serve as an input terminal. A low-pass filter is formed by electrically connecting the other end of the second coil electrode 11 to the third capacitor electrode 9 that generates the ground capacitance C3, for example, via the third through conductor 14. Here, the capacitance generated between the first capacitor electrode 7 and the second capacitor electrode 8 via the second dielectric layer 2 / second ground electrode 6 and the third dielectric layer 3 is C4. Similarly, the capacitance generated between the first capacitor electrode 7 and the third capacitor electrode 9 is C5.
[0020]
According to such an example of the low-pass filter of the present invention shown in FIG. 1, the equivalent circuit diagram of the low-pass filter is as shown in FIG. The capacitances C1 to C5 are adjusted by the first to third dielectric layers 1 to 3, the first and second ground electrodes 5.6 and the first to third capacitor electrodes 7 to 9, and By adjusting the inductances L1 and L2 with the second coil electrodes 10 and 11, a low-pass filter having desired low-pass characteristics can be obtained.
[0021]
In addition, the input terminal and the output terminal are led out to the lower surface of the first dielectric layer while being electrically insulated from the first ground electrode 5, so that this low-pass filter can be used as a surface-mounted electronic component as an external electric circuit. It can be mounted on a substrate.
[0022]
As described above, in the example of the low-pass filter of the present invention shown in FIG. 1, the inductance L1 formed by the first coil electrode 10 and the inductance of the first coil electrode 10, as shown in the equivalent circuit diagram of FIG. The first capacitor electrode 7 connected to both ends and the second capacitor electrode 8 are formed with the second dielectric layer 2, the second ground electrode 6, and the third dielectric layer 3 interposed therebetween. A parallel resonance circuit with the capacitor C4, an inductance L2 formed by the second coil electrode 11, a first capacitor electrode 7 connected to both ends of the second coil electrode 11, and a second dielectric. A parallel resonance circuit is formed with a capacitor C5 formed by the third capacitor electrode 9 facing the third capacitor layer 9 with the layer 2, the second ground electrode 6 and the third dielectric layer 3 interposed therebetween. Both parallel resonance circuits By appropriate frequency doubling and triple harmonics of the respective pass bands, it can be reliably performed twice and three times the harmonic elimination of passband required for the low-pass filter.
[0023]
Further, the parallel resonance circuit is formed by the inductance L1 and the capacitance C4 and the inductance L2 and the capacitance C5, respectively, and can be set by the length of each of the coil electrodes 10 and 11 and the area of each of the capacitor electrodes 7 to 9. It is possible to lower the resonance frequency without increasing the overall shape as disclosed in JP-A-7-273502.
[0024]
When the resonance frequency is adjusted by the inductances L1 and L2, the lengths of the first and second coil electrodes 10 and 11 and the thickness of the fourth dielectric layer 4 may be adjusted. Further, when the resonance frequency is adjusted by the capacitances C4 and C5, the overlapping area of the first capacitor electrode 7, the second capacitor electrode 8, and the third capacitor electrode 9 as viewed in the laminating direction, Opening around the first through conductor 12 of the second ground electrode 6 which limits the overlapping area of the second capacitor electrode 7 and the second capacitor electrode 8 and the third capacitor electrode 9 as viewed in the laminating direction. The area of the portion and the thickness of the second and third dielectric layers 2 and 3 may be adjusted. Thus, in the low-pass filter of the present invention, there are many parameters that can set the attenuation pole, that is, the resonance frequency of the parallel resonance circuit, and the design flexibility is large.
[0025]
The first and second coil electrodes 10 and 11 are formed on the upper surface of the fourth dielectric layer 4 so as to be opposed to, for example, the second and third capacitor electrodes 8 and 9. However, as in the example shown in FIG. 1, the first and second coil electrodes 10 and 11 may be formed not only on the upper surface of the fourth dielectric layer 4 but also on the inside thereof. In that case, a region for mounting electronic components or providing wiring can be secured on the upper surface of the fourth dielectric layer 4, so that the structure is not a simple low-pass filter but a part of the module substrate. You can also. In addition, the first and third coil electrodes 10 and 11 are arranged so as to face the second and third capacitor electrodes 8 and 9, respectively, so that the first to third through conductors 12 to 14 are substantially perpendicular. Direction, the length can be minimized, and unnecessary inductance components of the through conductor can be reduced, so that a low-pass filter having good attenuation characteristics can be obtained.
[0026]
Further, of the first to third three capacitor electrodes 7 to 9, the first capacitor electrode 7, which is the largest in the configuration of a commonly used Butterworth-type, Bessel-type, and Chebyshev-type low-pass filter, is replaced with the first capacitor electrode 7. Formed between the first ground electrode 5 and the second ground electrode 6, the size of the ground capacitance C1 formed with the first capacitor electrode 7 and the first and second ground electrodes 5 and 6 facing each other Can be reduced to approximately half the size required when facing only one ground electrode, and the first capacitor electrode 7, the second capacitor electrode 8, and the third capacitor electrode 9 Since they are arranged to face each other and overlap when viewed from the laminating direction, the area of the entire low-pass filter can be reduced when viewed from the laminating direction. It is possible to reduce the size of.
[0027]
FIG. 3 is a diagram showing frequency characteristics in the example of the low-pass filter of the present invention shown in FIG. In FIG. 3, the horizontal axis represents frequency (unit: GHz), the vertical axis represents signal passing amount S (2, 1) (unit: dB), and the characteristic curve represents the frequency characteristic. According to the results shown in FIG. 3, according to the low-pass filter of the present invention, the frequencies (1.76 GHz to 1.83 GHz and 2.64 GHz to 2.times.3) twice and three times the pass band (0.88 GHz to 0.915 GHz). It can be seen that an attenuation pole appears at 745 GHz) and a large amount of attenuation is obtained.
[0028]
The low-pass filter of the present invention, for example, when the dielectric layer is made of ceramics, performs predetermined perforation processing on a dielectric ceramic green sheet to be each dielectric layer after firing, and performs pattern formation of each electrode. It is manufactured by applying a conductive paste to the through holes serving as the through conductors, the side surfaces of the green sheets, and the like, laminating these and firing. Alternatively, using a resin substrate such as a fluororesin or glass epoxy resin / polyimide resin for the dielectric layer, etching the copper foil on the surface to form each electrode pattern, forming via conductors for interlayer connection, and laminating press It is also manufactured with a resin substrate as described below.
[0029]
The dielectric layers including the first to fourth dielectric layers 1 to 4 are made of a ceramic material such as alumina ceramic or mullite ceramic, an inorganic material such as glass ceramic, or an ethylene tetrafluoride resin (polyethylene). Tetrafluoroethylene; PTFE) / tetrafluoroethylene-ethylene copolymer resin (tetrafluoroethylene-ethylene copolymer resin; ETFE) / tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin (tetrafluoroethylene-perfluteroalkyl) Fluororesins such as vinyl ether copolymer resin (PFA) and resin materials such as glass epoxy resin and polyimide are used. The first and second ground electrodes 5 and 6, the first to third capacitor electrodes 7 to 9, and the first and second coil electrodes 10 and 11 are each provided with a conductive layer of a metal material for transmitting a high-frequency signal. For example, a Cu layer, a Ni-plated layer and an Au-plated layer deposited on a Mo-Mn metallized layer, a Ni-plated layer and an Au plated layer deposited on a W-metallized layer, Cr-Cu Alloy layer, Cr-Cu alloy layer with Ni plating layer and Au plating layer deposited, Ta ₂ Ni-Cr alloy layer and Au plating layer deposited on N layer-Pt layer and Au plating layer deposited on Ti layer-Pt layer and Au plating on Ni-Cr alloy layer It is formed by a thick film printing method, various thin film forming methods, a plating method, or the like, using a material having a layer adhered thereto. The thickness and width are set according to the frequency of the high frequency signal to be transmitted, the application, and the like.
[0030]
Next, FIG. 4 shows another example of the low-pass filter according to the embodiment of the present invention in an exploded perspective view similar to FIG.
[0031]
In FIG. 4, 1a is a first dielectric layer, 2a is a second dielectric layer, 3a is a third dielectric layer, 4a is a fourth dielectric layer, 5a is a first ground electrode, and 6a is A second ground electrode, 7a is a first capacitor electrode, 8a is a second capacitor electrode, 9a is a third capacitor electrode, 10a is a first coil electrode, 11a is a second coil electrode, and 12a is a first coil electrode. , 13a is a second through conductor, and 14a is a third through conductor.
[0032]
In the example shown in FIG. 4, a first ground electrode 5a formed on the lower surface of the first dielectric layer 1a and a second ground electrode 5a formed between the second dielectric layer 2a and the third dielectric layer 3a are formed. Between the first ground electrode 6a and the first capacitor electrode 7a formed between the first dielectric layer 1a and the second dielectric layer 2a and facing the first ground electrode 5a and the second ground electrode 6a. The second capacitor electrode 8a and the third capacitor electrode formed between the third dielectric layer 3a and the fourth dielectric layer 4a and facing the second ground electrode 2a, respectively, where C2a and C3a, respectively, and the inductance generated by the first coil electrode 10a and the second coil electrode 11a formed on the upper surface of the fourth dielectric layer 4a. L1a and L2a, respectively, the first capacitor electrode 7a, the second capacitor electrode 8a and the third capacitor via the second dielectric layer 2a, the second ground electrode 6a and the third dielectric layer 3a. Capacitors formed to face the electrode 9a are denoted by C4a and C5a, respectively.
[0033]
Then, in the example shown in FIG. 4, one end of the first coil electrode 10a and one end of the second coil electrode 11a are connected to each other, and for example, a first capacitor electrode that generates a ground capacitance C1a via the first through conductor 12a. 7a, and the other end of the first coil electrode 10a is electrically connected to a second capacitor electrode 8a that generates a ground capacitance C2a via, for example, a second through conductor 13a to serve as an input terminal. Further, the other end of the second coil electrode 11a is electrically connected to the third capacitor electrode 9a for generating the ground capacitance C3a via, for example, a third through conductor 14a, thereby forming a low-pass filter. Here, the capacitance generated between the first capacitor electrode 7a and the second capacitor electrode 8a is C4a, and the capacitance generated between the first capacitor electrode 7a and the third capacitor electrode 9a is C5a.
[0034]
In the example shown in FIG. 4, the first and second coil electrodes 10a and 11a formed on the upper surface of the fourth dielectric layer 4a are each formed in a meander shape, so that the first and second coil electrodes are formed. Since there is no need to electrically connect using a through conductor, the fourth dielectric layer 4a and the first and second coil electrodes are compared with the example shown in FIG. The configurations of 10a and 11a can be simplified, which is an advantageous configuration in terms of reduction in variation in characteristics and reduction in manufacturing cost.
[0035]
According to such an example of the low-pass filter of the present invention shown in FIG. 4, the equivalent circuit diagram is as shown in FIG. By adjusting the capacitances C1a to C5a and the inductances L1a and L2a, a low-pass filter having desired characteristics can be obtained.
[0036]
FIG. 6 is a diagram similar to FIG. 3 showing frequency characteristics in the example of the low-pass filter of the present invention shown in FIG. According to the results shown in FIG. 6, according to the low-pass filter of the present invention, as in FIG. 3, the frequencies (1.76 GHz to 1.83 GHz and 2.83 GHz) which are twice and three times the passband (0.88 GHz to 0.915 GHz) are used. It can be seen that an attenuation pole appears at a frequency range of 0.664 GHz to 2.745 GHz) and a large amount of attenuation is obtained.
[0037]
It should be noted that the present invention is not limited to the above-described embodiments, and various changes may be made without departing from the spirit of the present invention. For example, according to the low-pass filter of the present invention, the thickness of the first to third dielectric layers 1 to 3 can be reduced, a high dielectric constant material can be used for the first to third dielectric layers, , It is possible to further improve the characteristics and reduce the size.
[0038]
Also, a shield electrode may be provided on the upper surface of the fourth dielectric layer, or a connection conductor for each electrode may be formed on the side surface of the dielectric layer instead of the first through third through conductors, and electrical connection between the electrodes may be made. May be connected.
[0039]
Further, the low-pass filter of the present invention can be configured as a part of a circuit board, not as a filter single component.
[0040]
【The invention's effect】
According to the low-pass filter of the present invention, the first to fourth dielectric layers sequentially laminated, the first ground electrode formed on the lower surface of the first dielectric layer, and the second and third dielectric layers A second ground electrode formed between the layers, a first capacitor electrode formed between the first and second dielectric layers and facing the first and second ground electrodes, and a third and fourth dielectric layer. A second capacitor electrode formed between the body layers and facing the second ground electrode, and a first and a second coil electrode formed on the upper surface of the fourth dielectric layer; One ends of the first and second coil electrodes are connected to each other, the one end is electrically connected to the first capacitor electrode, and the other end of the first coil electrode is electrically connected to the second capacitor electrode. Input and input And the other end of the second coil electrode is electrically connected to the third capacitor electrode and a low-pass filter is configured as an output terminal. Therefore, the first coil electrode (L1) and the first coil electrode (L1) An attenuation pole developed by a parallel resonance circuit formed by a capacitor (C4) formed between the first capacitor electrode and the second capacitor electrode to be connected to both ends of the second capacitor electrode, and a second coil electrode (L2) and a capacitor (C5) formed between the first capacitor electrode and the third capacitor electrode, which is connected to both ends of the second coil electrode (L2). The developed attenuation pole can be arbitrarily set by changing the size of the coil electrode and the capacitors connected to both ends of the coil electrode. In other words, the capacitor electrode can be made smaller if the coil electrode is to be made larger, and the coil electrode can be made smaller if the capacitor electrode is to be made larger.By appropriately setting the size of the coil electrode and the capacitor electrode, the entire low-pass filter can be made. The attenuation pole can be reduced without increasing the size of the coil electrode and the capacitor electrode.
[0041]
Further, by connecting two parallel resonance circuits in series in this manner, two arbitrary attenuation poles can be provided. Further, among the first to third capacitor electrodes, the first capacitor electrode which is the largest in the configuration of a commonly used low-pass filter such as a Butterworth-type, Bessel-type, or Chebyshev-type is used as the first and second capacitor electrodes. Since the first capacitor electrode and the first and second ground electrodes are formed between the dielectric layers so as to face the first and second ground electrodes, the magnitude of the ground capacitance C1 formed with the first capacitor electrode and the first and second ground electrodes facing each other is reduced. The size can be reduced to approximately half the size required when facing only one ground electrode. Further, when viewed from the stacking direction, the first capacitor electrode and the second and third capacitor electrodes can be overlapped, so that the entire low-pass filter can be reduced in size.
[0042]
Further, when the input terminal and the output terminal are led out to the lower surface of the first dielectric layer, the low-pass filter can be mounted on an external electric circuit board as a surface-mounted electronic component.
[0043]
As described above, according to the present invention, attenuation poles are provided twice and three times the passband, the attenuation pole can be adjusted with many parameters, and the overall shape can be reduced in size. A low-pass filter suitably used in a high frequency band can be provided.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing an example of an embodiment of a low-pass filter of the present invention.
FIG. 2 is an equivalent circuit diagram of an example of the low-pass filter shown in FIG.
FIG. 3 is a diagram illustrating frequency characteristics of an example of the low-pass filter illustrated in FIG. 1;
FIG. 4 is an exploded perspective view showing another example of the embodiment of the low-pass filter of the present invention.
FIG. 5 is an equivalent circuit diagram of an example of the low-pass filter shown in FIG.
FIG. 6 is a diagram illustrating frequency characteristics of the example of the low-pass filter illustrated in FIG. 4;
[Explanation of symbols]
1, 1a... First dielectric layer
2, 2a... Second dielectric layer
3, 3a... Third dielectric layer
4, 4a... Fourth dielectric layer
5, 5a... First ground electrode
6, 6a... Second ground electrode
7, 7a... First capacitor electrode
8, 8a... Second capacitor electrode
9, 9a... Third capacitor electrode
10, 10a... First coil electrode
11, 11a... Second coil electrode
12, 12a... First through conductor
13, 13a... Second through conductor
13, 13a... Third through conductor

Claims (2)

First to fourth dielectric layers sequentially stacked, a first ground electrode formed on the lower surface of the first dielectric layer, and a second ground electrode formed between the second and third dielectric layers. A ground electrode, a first capacitor electrode formed between the first and second dielectric layers, and facing the first and second ground electrodes, and a third capacitor layer formed between the third and fourth dielectric layers. And second and third capacitor electrodes respectively opposed to the second ground electrode, and first and second coil electrodes formed on the upper surface of the fourth dielectric layer. One ends of the first and second coil electrodes are connected to each other, the one end is electrically connected to the first capacitor electrode, and the other end of the first coil electrode is connected to the second capacitor electrode. Electrical connection and input terminal Low-pass filter and is characterized by the other end of the second coil electrode and the output terminal with connecting the third capacitor electrode electrically. 2. The low-pass filter according to claim 1, wherein said input terminal and said output terminal are led out to a lower surface of said first dielectric layer.

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