JP2010141827A - Noise filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a noise filter suitable for a countermeasure against common-mode noise as well as a countermeasure against normal-mode noise between the driver and receiver of a mobile phone while suppressing the degradation of quality in a differential signal waveform. <P>SOLUTION: An LC filter LC1 contains a coil L1. An LC filter LC2 contains a coil L2. A stack 12a is constructed such that the LC filters LC1, LC2 are embedded therein while a plurality of dielectric layers 14a to 14f, 16a to 16q are stacked. The coil L2 overlaps with the coil L1 in z-axis direction, and overlaps with the coil L1 when plane-viewed from the z-axis direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a noise filter, and relates to a noise filter incorporating a common mode choke coil.

  A differential transmission method may be used as a signal transmission method between a driver and a receiver of a mobile phone. In the differential transmission method, since the sum of the currents of the differential signals transmitted through the two signal lines is constant, no common mode noise is theoretically generated.

  However, in practice, the balance of the amplitude, rise time, phase, etc. of the two signals is lost due to variations in the impedance of the driver, and common mode noise occurs in the differential signal. Therefore, it is necessary to take measures against common mode noise between the driver and the receiver.

  Furthermore, in the differential transmission method, depending on the standard (for example, 3GPP), it is necessary to remove higher-order (fourth-order or higher) harmonics of the normal mode signal constituting the differential signal. That is, the normal mode signal may be regarded as normal mode noise. Therefore, it is necessary to take measures against normal mode noise between the driver and the receiver. As described above, there is a demand for a noise filter suitable for common mode noise countermeasures and normal mode noise countermeasures between mobile phone drivers and receivers.

As a conventional noise filter, for example, a multilayer array component described in Patent Document 1 is known. However, since the multilayer array component is a noise filter for removing normal mode noise, the normal mode noise, that is, the harmonic signal constituting the differential signal is excessively removed, and the waveform quality is deteriorated.
JP 2005-64267 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide a noise filter suitable for common mode noise countermeasures and normal mode noise countermeasures between a mobile phone driver and a receiver while suppressing deterioration in the quality of a differential signal waveform. .

  A noise filter according to one aspect of the present invention includes a first LC filter including a first coil, a second LC filter including a second coil, the first LC filter, and the second LC filter. And a laminated body formed by laminating a plurality of insulator layers, and the second coil overlaps the first coil in the laminating direction and is planar from the laminating direction. It is characterized by overlapping with the first coil when viewed.

  According to the present invention, it becomes easy to set the coupling coefficient of the two coils to 0.3 or more and 0.6 or less, so that the deterioration of the quality of the differential signal waveform is suppressed, and the driver and receiver of the mobile phone Common mode noise and normal mode noise transmitted between the two can be effectively removed.

  The noise filter according to the embodiment of the present invention will be described below.

(First embodiment)
FIG. 1 is an external perspective view of noise filters 10a to 10f according to the embodiment of the present invention. FIG. 2 is an exploded view of the multilayer body 12a of the noise filter 10a. FIG. 3 is an equivalent circuit diagram of the noise filter 10a. Hereinafter, the direction in which the ceramic green sheets are laminated when the noise filter 10a is formed is defined as the lamination direction. The stacking direction is the z-axis direction, the longitudinal direction of the noise filter 10a is the x-axis direction, and the direction orthogonal to the x-axis and the z-axis is the y-axis direction. The x-axis, y-axis, and z-axis are parallel to the sides that constitute the noise filter 10a.

(Noise filter configuration)
As shown in FIG. 1, the noise filter 10a includes a laminated body 12a and external electrodes E1 to E10. Hereinafter, surfaces positioned at both ends in the x-axis direction of the stacked body 12a are defined as end surfaces, surfaces positioned at both ends in the y-axis direction of the stacked body 12a are defined as side surfaces, and a positive direction in the z-axis direction of the stacked body 12a. The surface on the side is defined as the upper surface, and the surface on the negative direction side in the z-axis direction of the laminate 12a is defined as the lower surface.

  The external electrodes E1, E3, E5, and E7 are each formed to extend in the z-axis direction on the side surface on the positive direction side in the y-axis direction. Each of the external electrodes E1, E3, E5, E7 functions as an input terminal. The external electrodes E2, E4, E6, E8 are each formed to extend in the z-axis direction on the negative side surface in the y-axis direction. The external electrodes E2, E4, E6, E8 each function as an output terminal. The external electrodes E9 and E10 are each formed to extend in the z-axis direction on both end faces. The external electrodes E9 and E10 each function as a ground electrode.

  As will be described below, the multilayer body 12a is configured by laminating a plurality of internal electrodes and a plurality of dielectric layers, and incorporates LC filters LC1 to LC4 therein. More specifically, as shown in FIG. 2, the multilayer body 12 a is configured by laminating a plurality of dielectric layers 14 a to 14 c, 16 a to 16 q, and 14 d to 14 f in this order. The plurality of dielectric layers 14a to 14c, 16a to 16q, and 14d to 14f are rectangular insulating layers each having substantially the same area and shape.

  On the main surface of the dielectric layer 16a, rectangular capacitor electrodes 50, 52, 54, 56 having a longitudinal direction in the y-axis direction are formed. Capacitor electrodes 50, 52, 54, and 56 are leads for connecting the capacitor electrodes 50, 52, 54, and 56 to the external electrodes E2, E4, E6, and E8 at the negative end in the y-axis direction, respectively. Parts 51, 53, 55 and 57. A rectangular capacitor electrode 58 having a longitudinal direction in the x-axis direction is formed on the main surface of the dielectric layer 16b. The capacitor electrode 58 has lead portions 71 and 72 for connecting the capacitor electrode 58 and the external electrodes E9 and E10 at both ends in the x-axis direction.

  The capacitor electrode 50 and the capacitor electrode 58 are opposed to each other with the dielectric layer 16a interposed therebetween, thereby forming the capacitor C1. The capacitor electrode 52 and the capacitor electrode 58 are opposed to each other with the dielectric layer 16a interposed therebetween, thereby forming the capacitor C2. The capacitor electrode 54 and the capacitor electrode 58 are opposed to each other with the dielectric layer 16a interposed therebetween, thereby forming a capacitor C3. The capacitor electrode 56 and the capacitor electrode 58 are opposed to each other with the dielectric layer 16a interposed therebetween, thereby forming a capacitor C4.

  Coil electrodes 30a to 30h and 34a to 34h each having a shape in which linear electrodes are bent are provided on the principal surfaces of the dielectric layers 16c to 16f and 16h to 16k, respectively. More specifically, each of the coil electrodes 30a and 34a has an “L” shape, and one end thereof is connected to each of the external electrodes E1 and E7. The coil electrodes 30b to 30g and 34b to 34g are electrodes formed in a spiral shape so as to rotate in opposite directions to each other formed on the same dielectric layer 16. The coil electrodes 30h and 34h each have an “L” shape, and one ends thereof are connected to the external electrodes E2 and E8, respectively.

  Furthermore, via conductors b1 to b8 and b21 to b28 are provided in the dielectric layers 16c to 16j, respectively. The via conductors b1 to b4 and b6 to b8 are connected to one ends of the coil electrodes 30a to 30h. The via conductor b5 connects the via conductor b4 and the via conductor b6. On the other hand, the via conductors b21 to b24 and b26 to b28 are connected to one ends of the coil electrodes 34a to 34h. The via conductor b25 connects the via conductor b24 and the via conductor b26. Thus, when the dielectric layers 16c to 16k are stacked, the via conductors b1 to b8 and b21 to b28 connect the coil electrodes 30a to 30h and 34a to 34h adjacent in the z-axis direction. As a result, the coil electrodes 30a to 30h constitute the coil L1, and the coil electrodes 34a to 34h constitute the coil L4.

  Coil electrodes 32a to 32h and 36a to 36h each having a shape in which linear electrodes are bent are provided on the principal surfaces of the dielectric layers 16g to 16j and 16l to 16o, respectively. More specifically, each of the coil electrodes 32a and 36a has an “L” shape, and one end thereof is connected to each of the external electrodes E4 and E6. The coil electrodes 32b to 32g and 36b to 36g are electrodes formed in a spiral shape so as to rotate in opposite directions to each other formed on the same dielectric layer 16. The coil electrodes 32h and 36h each have a “U” shape, and one ends thereof are connected to the external electrodes E3 and E5, respectively.

  Furthermore, via conductors b11 to b18 and b31 to b38 are provided in the dielectric layers 16g to 16n, respectively. The via conductors b11 to b14 and b16 to b18 are connected to one ends of the coil electrodes 32a to 32h. The via conductor b15 connects the via conductor b14 and the via conductor b16. On the other hand, the via conductors b31 to b34 and b36 to b38 are connected to one ends of the coil electrodes 36a to 36h. The via conductor b35 connects the via conductor b34 and the via conductor b36. Thus, when the dielectric layers 16g to 16n are stacked, the via conductors b11 to b18 and b31 to b38 connect the coil electrodes 32a to 32h and 36a to 36h adjacent in the z-axis direction. As a result, the coil electrodes 32a to 32h constitute the coil L2, and the coil electrodes 36a to 36h constitute the coil L3.

  On the main surface of the dielectric layer 16q, rectangular capacitor electrodes 60, 62, 64, 66 having a longitudinal direction in the y-axis direction are formed. Capacitor electrodes 60, 62, 64, and 66 are leads for connecting the capacitor electrodes 60, 62, 64, and 66 to the external electrodes E2, E4, E6, and E8 at the negative end in the y-axis direction, respectively. It has parts 61, 63, 65, 67. A rectangular capacitor electrode 68 having a longitudinal direction in the x-axis direction is formed on the main surface of the dielectric layer 16p. The capacitor electrode 68 has lead portions 73 and 74 for connecting the capacitor electrode 68 and the external electrodes E9 and E10 at both ends in the x-axis direction.

  Capacitor C1 is configured by capacitor electrode 60 and capacitor electrode 68 facing each other with dielectric layer 16p interposed therebetween. The capacitor electrode 62 and the capacitor electrode 68 are opposed to each other with the dielectric layer 16p interposed therebetween, thereby forming the capacitor C2. The capacitor electrode 64 and the capacitor electrode 68 are opposed to each other with the dielectric layer 16p interposed therebetween, thereby forming the capacitor C3. The capacitor electrode 66 and the capacitor electrode 68 are opposed to each other with the dielectric layer 16p interposed therebetween, thereby forming a capacitor C4.

  Since the laminated body 12a has the above-described configuration, as shown in FIG. 3, the LC filter LC1 including the coil L1 and the capacitor C1, the LC filter LC2 including the coil L2 and the capacitor C2, the coil L3, and the capacitor C3 are included. The LC filter LC3 including the LC filter LC3 and the coil L4 and the capacitor C4 is formed. The LC filters LC2 and LC3 are not electrically connected to the LC filters LC1 and LC4. Here, taking the LC filter LC1 as an example, one end of the coil L1 is connected to the external electrode E1, and the other end of the coil L1 is connected to the external electrode E2. Furthermore, one end of the capacitor C1 is connected to the other end of the coil L1, and the other end of the capacitor C1 is connected to the external electrodes E9 and E10. The configurations of the LC filters LC2, LC3, and LC4 are the same as the configuration of the LC filter LC1, and thus the description thereof is omitted.

  By the way, since the external electrodes E1 and E3 function as input terminals and the external electrodes E2 and E4 function as output terminals, in FIG. 2, for example, current flows through the coil L1 from the top to the bottom in the z-axis direction. In the coil L2, for example, a current flows from the bottom to the top in the z-axis direction. That is, a current flows through the coil L1 and the coil L2 in the opposite directions in the z-axis direction. Further, the coil electrodes 30a to 30f constituting the coil L1 rotate clockwise as it goes from the top to the bottom in the z-axis direction, and the coil electrodes 34a to 34f constituting the coil L2 are turned from the top in the z-axis direction. As it goes down, it turns counterclockwise. That is, the coil L1 and the coil L2 are rotated in opposite directions. Therefore, when current flows through the coil L1 and the coil L2, the current turns in the same direction. Moreover, the coil L1 and the coil L2 are comprised by bifilar winding. Specifically, as shown in FIG. 2, the coil L1 and the coil L2 are arranged in the z-axis direction so that the coil axis of the coil L1 and the coil axis of the coil L2 overlap when viewed in plan from the z-axis direction. Has been placed. Further, the coil L2 partially overlaps the coil L1 in the dielectric layers 16g to 16k in the z-axis direction. As a result, the coil L1 and the coil L2 generate magnetic fluxes in the same direction and are magnetically coupled, so that the coil L1 constituting the LC filter LC1 and the coil L2 constituting the LC filter LC2 are common mode choke coils. Also functions as L11. Note that the coil L3 constituting the LC filter LC3 and the coil L4 constituting the LC filter LC4 also function as the common mode choke coil L12, but the details are the same as those of the coil L1 and the coil L2, so the description will be given. Omitted.

(effect)
As described above, according to the noise filter 10a, the LC filters LC1 to LC4 are incorporated, and the coils L1 to L4 also serve as the coils constituting the common mode choke coils L11 and L12. Both common mode noises can be removed.

  In particular, in the noise filter 10a, as shown in FIG. 2, when viewed in plan from the z-axis direction, the coil axis of the coil L1 and the coil axis of the coil L2 coincide with each other, and a part of the coil L1 and the coil Part of L2 overlaps in the z-axis direction. Therefore, by adjusting the length of the portion where the coil L1 and the coil L2 overlap in the z-axis direction, the coil L1 and the coil L2 can be easily coupled with an appropriate coupling coefficient. Similarly, it becomes easy to couple the coil L3 and the coil L4 with an appropriate coupling coefficient. Specifically, the appropriate coupling coefficient is not less than 0.3 and not more than 0.6. And the differential signal which transmits between the driver and receiver of a mobile telephone by making the coupling coefficient of the coil L1 and the coil L2 and the coupling coefficient of the coil L3 and the coil L4 into 0.3 or more and 0.6 or less. Can effectively remove normal mode noise.

  More specifically, the present inventor performed a computer simulation described below in order to confirm the effect produced by the noise filter 10a. 4 to 7 are graphs showing the results of the computer simulation. In the noise filter 10a, the coupling coefficient between the coil L1 and the coil L2 and the coupling coefficient between the coil L3 and the coil L4 are 0.2, 0.3. , 0.6, 0.7 is a graph showing the relationship between the insertion loss of normal mode noise and the frequency. The vertical axis represents noise insertion loss, and the horizontal axis represents frequency.

  The frequency of the differential signal transmitted between the driver and the receiver of the mobile phone is about 100 MHz. In such a differential signal, the insertion loss of normal mode noise near 300 MHz, which is the third harmonic, needs to be smaller than 3 dB. This is because if the insertion loss of normal mode noise near 300 MHz is too large, the differential signal itself is adversely affected.

  Therefore, referring to the graph shown in FIG. 4, it can be seen that when the coupling coefficient is 0.2, the insertion loss of normal mode noise at 300 MHz is about 5 dB. On the other hand, referring to the graph shown in FIG. 5, when the coupling coefficient is 0.3, the insertion loss of normal mode noise at 300 MHz is about 3 dB. Therefore, the coupling coefficient between the coil L1 and the coil L2 and the coupling coefficient between the coil L3 and the coil L4 are preferably 0.3 or more.

  Also, the insertion loss of normal mode noise in the vicinity of 470 MHz, which is the lower limit frequency of the UHF band, needs to be larger than 10 dB. This is to prevent the UHF band signal from affecting the differential signal as normal mode noise.

  Therefore, referring to the graph shown in FIG. 7, it can be seen that when the coupling coefficient is 0.7, the insertion loss of normal mode noise at 470 MHz is about 5 dB. On the other hand, referring to the graph shown in FIG. 6, when the coupling coefficient is 0.6, the insertion loss of normal mode noise at 470 MHz is about 10 dB. Therefore, the coupling coefficient between the coil L1 and the coil L2 and the coupling coefficient between the coil L3 and the coil L4 are preferably 0.6 or less.

  As described above, since the noise filter 10a has the common mode choke coils L11 and L12, common mode noise generated between the driver and the receiver of the mobile phone can be removed. Furthermore, since the coupling coefficient between the coil L1 and the coil L2 and the coupling coefficient between the coil L3 and the coil L4 are 0.3 or more and 0.6 or less, the noise filter 10a suppresses the deterioration of the differential signal waveform. However, normal mode noise can also be removed. Therefore, the noise filter 10a is suitable for the common mode noise countermeasure and the normal mode noise countermeasure between the driver and the receiver of the mobile phone.

  Next, this inventor experimented in order to clarify the effect which the noise filter 10a has. More specifically, a first experimental example corresponding to the noise filter 10a was produced, and a second experimental example corresponding to the multilayer array component described in Patent Document 1 was produced. The coupling coefficient of the second experimental example was set to 0.05 or less. As a first experiment, a rectangular wave was input to these experimental examples, and the output signal output was measured. As a second experiment, the noise intensity distribution at each frequency at the time of input to these experimental examples and the noise intensity distribution at each frequency at the time of output from these experimental examples were measured.

  FIG. 8 is a graph showing the results when the first experiment was performed in the first experimental example. FIG. 9 is a graph showing the results of performing the first experiment in the second experimental example. 8 and 9, the vertical axis indicates the signal level, and the horizontal axis indicates time.

  FIG. 10 is a graph showing the results of performing the second experiment in the second experimental example. FIG. 11 is a graph showing the results of performing the second experiment in the first experimental example. 10 and 11, the vertical axis represents the noise level, and the horizontal axis represents the frequency.

  In the first experiment, when a rectangular wave is input to the first experimental example and the second experimental example, noise at high frequencies is removed, and as shown in FIGS. In both experimental examples, a sinusoidal signal has been output. Comparing FIG. 8 and FIG. 9, the output signal of FIG. 8 has a sharper rise and fall than the output signal of FIG. 9, and has a waveform closer to the input signal. I understand. Therefore, it can be understood that the degree of deterioration of the output signal when the rectangular wave is used as the input signal is smaller in the first experimental example than in the second experimental example. That is, it can be understood that the degradation of the output signal in the noise filter 10a is smaller than the degradation of the output signal in the multilayer array component described in Patent Document 1.

  Further, in the second experiment, noise having the same intensity distribution was input to the first experiment example and the second experiment example. As a result, as shown in FIGS. 10 and 11, it can be seen that substantially the same noise removal effect can be obtained in the first experimental example and the second experimental example. That is, it can be understood that the noise removal effect of the noise filter 10a is equivalent to the noise removal effect of the multilayer array component described in Patent Document 1.

  As described above, according to the first experiment and the second experiment, it can be seen that the noise filter 10a can obtain a good noise removal effect while reducing the deterioration of the waveform of the output signal.

  Also, according to the noise filter 10a, the LC filter and the common mode choke coil are built in one noise filter 10a, and therefore the LC filter and the common mode choke coil are configured by separate electronic components. As a result, the entire circuit can be reduced in size. In particular, in the noise filter 10a, the coils L1 and L2 function as the common mode choke coil L11 and also function as part of the LC filters LC1 and LC2. Similarly, the coils L3 and L4 function as the common mode choke coil L12 and also function as part of the LC filters LC3 and LC4. As described above, in the noise filter 10a, the coils L1 to L4 are also used as a part of the LC filter and a part of the common mode choke coil, so that the noise filter 10a is further downsized.

  Further, the noise filter 10a can efficiently remove common mode noise as described below. In the xz cross section, when the magnetic flux generated by the coil L1 and the magnetic flux generated by the coil L2, and the magnetic flux generated by the coil L3 and the magnetic flux generated by the coil L4 are not equal, the normal mode noise is converted into common mode noise. As a result, new common mode noise is generated, and the common mode noise is not efficiently removed. Therefore, in the noise filter 10a, the current paths of the coils L1 and L2 are configured so that the magnitude of the magnetic flux generated by the coil L1 and the magnitude of the magnetic flux generated by the coil L2 are substantially equal in the xz section. Similarly, in the xz section, the current paths of the coils L3 and L4 are configured so that the magnitude of the magnetic flux generated by the coil L3 and the magnitude of the magnetic flux generated by the coil L4 are substantially equal. Thereby, the difference in characteristics between the coil L1 and the coil L2 and between the coil L3 and the coil L4 can be reduced. Therefore, normal mode noise is not converted into common mode noise, and new common mode noise is not generated. Therefore, in the noise filter 10a, common mode noise can be more efficiently removed by the common mode choke coil L11 and the common mode choke coil L12.

  In addition, when the capacitor electrode is not line symmetric with respect to the dielectric layer 16i in the xz section, the magnitude of the magnetic flux is difficult to be equal, so that normal mode noise is converted into common mode noise, and a new common Mode noise occurs and common mode noise is not efficiently removed. On the other hand, as shown in FIG. 2, the capacitor electrodes 50, 52, 58, 60, 62, and 68 are on the boundary line (dielectric layer 16i in FIG. 2) between the LC filter LC1 and the LC filter LC2 in the xz cross section. On the other hand, it has a substantially line-symmetric structure. Similarly, as shown in FIG. 2, the capacitor electrodes 54, 56, 58, 64, 66, and 68 are on the boundary line (dielectric layer 16 i in FIG. 2) between the LC filter LC 3 and the LC filter LC 4 in the xz cross section. On the other hand, it has a substantially line-symmetric structure. As a result, the influence of the capacitor electrodes 50, 52, and 58 on the magnetic flux by the coil L1 can be made equal to the influence of the capacitor electrodes 60, 62, and 68 on the magnetic flux by the coil L2. Similarly, the influence of the capacitor electrodes 54, 56, and 58 on the magnetic flux by the coil L4 can be made equal to the influence of the capacitor electrodes 64, 66, and 68 on the magnetic flux by the coil L3. That is, the difference in characteristics between the coil L1 and the coil L2 and between the coil L3 and the coil L4 can be further reduced. Therefore, normal mode noise is not converted into common mode noise, and new common mode noise is not generated. Therefore, in the noise filter 10a, common mode noise can be more efficiently removed by the common mode choke coil L11 and the common mode choke coil L12.

  In the noise filter 10a, as shown in FIG. 2, the coils L1 and L2 are laminated so as to be positioned between the capacitors C1 and C2 in the z-axis direction. That is, no capacitor is provided between the coil L1 and the coil L2. Therefore, the magnetic flux generated in the coil L1 and the coil L2 is not easily disturbed by the capacitors C1 and C2. As a result, the magnetic flux in the coils L1 and L2 can be increased, the normal mode noise removal characteristics of the LC filters LC1 and LC2 can be improved, and the magnetic coupling between the LC filter LC1 and the LC filter LC2 is increased. Therefore, the common mode noise removal characteristics of the common mode choke coil L11 can be improved. The same applies to the LC filters LC3 and LC4 and the coils L3 and L4.

(Second Embodiment)
The configuration of the noise filter 10b according to the second embodiment will be described below with reference to the drawings. FIG. 12 is an exploded perspective view of the multilayer body 12b of the noise filter 10b according to the second embodiment. Since the external perspective view and equivalent circuit diagram of the noise filter 10b are the same as those of the noise filter 10a, FIGS. 1 and 3 are used. 12, the same components as those in FIG. 2 are denoted by the same reference numerals.

  The difference between the noise filter 10a and the noise filter 10b is how to couple the coils L1 and L2 and how to couple the coils L3 and L4. More specifically, in the noise filter 10a, the coil axis of the coil L1 and the coil axis of the coil L2 are matched when viewed in plan from the z-axis direction, and the coil L1 and the coil L2 are partially arranged in the z-axis direction. Are overlapping. Similarly, the coil axis of the coil L3 and the coil axis of the coil L4 are matched when viewed in plan from the z-axis direction, and the coil L4 and the coil L4 are partially overlapped in the z-axis direction. Yes.

  On the other hand, in the noise filter 10b, the coil axis of the coil L1 and the coil axis of the coil L2 are not overlapped when viewed in plan from the z-axis direction, and the coil L1 and the coil L2 are matched in the z-axis direction. Overlapping in the state. The coil axis of the coil L3 and the coil axis of the coil L4 are not overlapped when viewed in plan from the z-axis direction, and the coil L3 and the coil L4 are overlapped with each other in the z-axis direction. .

  More specifically, the coils L1 to L4 are provided in the dielectric layers 16c to 16i, and are provided in regions that coincide in the z-axis direction. And it arrange | positions so that it may not correspond when the coil axis | shaft of the coil L1 and the coil axis | shaft of the coil L2 are planarly viewed from the z-axis direction. However, the coil L1 and the coil L2 overlap when viewed in plan from the z-axis direction. Similarly, the coil axis of the coil L3 and the coil axis of the coil L4 are arranged so as not to coincide when viewed in plan from the z-axis direction. However, the coil L3 and the coil L4 overlap when viewed in plan from the z-axis direction.

  The noise filter 10b as described above can remove both normal mode noise and common mode noise, as with the noise filter 10a.

  In particular, as shown in FIG. 12, in the noise filter 10b, when viewed in plan from the z-axis direction, the coil axis of the coil L1 and the coil axis of the coil L2 are not overlapped when viewed in plan from the z-axis direction. At the same time, the coil L1 and the coil L2 are overlapped in the z-axis direction. Therefore, by adjusting the shift amount between the coil axis of the coil L1 and the coil axis of the coil L2, it becomes easy to couple the coil L1 and the coil L2 with an appropriate coupling coefficient. Similarly, it becomes easy to couple the coil L3 and the coil L4 with an appropriate coupling coefficient. Specifically, the appropriate coupling coefficient is not less than 0.3 and not more than 0.6. And the differential signal which transmits between the driver and receiver of a mobile telephone by making the coupling coefficient of the coil L1 and the coil L2 and the coupling coefficient of the coil L3 and the coil L4 into 0.3 or more and 0.6 or less. Can effectively remove normal mode noise.

(Third embodiment)
The configuration of the noise filter 10c according to the second embodiment will be described below with reference to the drawings. FIG. 13 is an exploded perspective view of the multilayer body 12c of the noise filter 10c according to the third embodiment. FIG. 14 is an equivalent circuit diagram of the noise filter 10c. 13 and 14, the same reference numerals are assigned to the same components as those in FIGS. 2 and 3.

  As shown in FIG. 13, the laminated body 12c is different from the laminated body 12a in that capacitor electrodes 80, 82, 84, 86, 90, 92, 94, and 96 are formed on the dielectric layers 16a and 16q, respectively. Is different. Hereinafter, the difference between the stacked body 12c and the stacked body 12a will be mainly described.

  Capacitor electrodes 50, 52, 54, 56, 80, 82, 84, 86 are formed on the dielectric layer 16a. The capacitor electrode 80 and the capacitor electrode 58 constitute a capacitor C5 by facing each other with the dielectric layer 16a interposed therebetween. The capacitor electrode 82 and the capacitor electrode 58 are opposed to each other with the dielectric layer 16a interposed therebetween, thereby forming a capacitor C6. The capacitor electrode 84 and the capacitor electrode 58 are opposed to each other with the dielectric layer 16a interposed therebetween, thereby forming a capacitor C7. The capacitor electrode 86 and the capacitor electrode 58 are opposed to each other with the dielectric layer 16a interposed therebetween, thereby forming a capacitor C8.

  Furthermore, a lead-out portion 81 is provided at the end of the capacitor electrode 80 on the positive side in the y-axis direction. As a result, as shown in FIG. 14, the capacitor C5 is connected between the external electrode E1 and the external electrodes E9 and E10. A lead-out portion 83 is provided at the end of the capacitor electrode 82 on the positive side in the y-axis direction. Thereby, as shown in FIG. 14, the capacitor C6 is connected between the external electrode E3 and the external electrodes E9 and E10. A lead-out portion 85 is provided at the end of the capacitor electrode 84 on the positive side in the y-axis direction. Thereby, as shown in FIG. 14, the capacitor C7 is connected between the external electrode E5 and the external electrodes E9 and E10. A lead-out portion 87 is provided at the end of the capacitor electrode 86 on the positive side in the y-axis direction. Thereby, as shown in FIG. 14, the capacitor C8 is connected between the external electrode E7 and the external electrodes E9 and E10.

  Capacitor electrodes 60, 62, 64, 66, 90, 92, 94, and 96 are formed on the dielectric layer 16q. The capacitor electrode 90 and the capacitor electrode 68 are opposed to each other with the dielectric layer 16p interposed therebetween, thereby forming a capacitor C5. The capacitor electrode 92 and the capacitor electrode 68 are opposed to each other with the dielectric layer 16p interposed therebetween, thereby forming a capacitor C6. The capacitor electrode 94 and the capacitor electrode 68 are opposed to each other with the dielectric layer 16p interposed therebetween, thereby constituting a capacitor C7. The capacitor electrode 96 and the capacitor electrode 68 are opposed to each other with the dielectric layer 16p interposed therebetween, thereby forming a capacitor C8.

  Further, a lead-out portion 91 is provided at the end of the capacitor electrode 90 on the positive side in the y-axis direction. As a result, as shown in FIG. 14, the capacitor C5 is connected between the external electrode E1 and the external electrodes E9 and E10. A lead-out portion 93 is provided at the end of the capacitor electrode 92 on the positive side in the y-axis direction. Thereby, as shown in FIG. 14, the capacitor C6 is connected between the external electrode E3 and the external electrodes E9 and E10. A lead-out portion 95 is provided at the end of the capacitor electrode 94 on the positive side in the y-axis direction. Thereby, as shown in FIG. 14, the capacitor C7 is connected between the external electrode E5 and the external electrodes E9 and E10. A lead-out portion 97 is provided at the end of the capacitor electrode 96 on the positive side in the y-axis direction. Thereby, as shown in FIG. 14, the capacitor C8 is connected between the external electrode E7 and the external electrodes E9 and E10.

  The noise filter 10c is added with capacitors C5 to C8 and has a saddle type structure, whereby the insertion loss of normal mode noise and common mode noise can be increased sharply.

  In the noise filter 10c, similarly to the noise filter 10a, the coil axis of the coil L1 and the coil axis of the coil L2 are matched when viewed in plan from the z-axis direction, and the coil L1 and the coil L2 are aligned in the z-axis direction. Are partially overlapped. Similarly, the coil axis of the coil L3 and the coil axis of the coil L4 are matched when viewed in plan from the z-axis direction, and the coil L3 and the coil L4 are partially overlapped in the z-axis direction. Yes. However, the method of coupling the coil L1 and the coil L2 and the method of coupling the coil L3 and the coil L4 are not limited to this. In the noise filter 10c, unlike the noise filter 10b, the coil axis of the coil L1 and the coil axis of the coil L2 are not overlapped when viewed in plan from the z-axis direction, and in the z-axis direction, the coil L1 and the coil L2 are not overlapped. And may be overlapped in a state in which. Similarly, when the coil axis of the coil L3 and the coil axis of the coil L4 are not overlapped when viewed in plan from the z-axis direction, the coil L3 and the coil L4 are overlapped with each other in the z-axis direction. It may be allowed.

(Fourth embodiment)
The configuration of the noise filter 10d according to the fourth embodiment will be described below with reference to the drawings. FIG. 15 is an exploded perspective view of the multilayer body 12d of the noise filter 10d according to the fourth embodiment. FIG. 16 is an equivalent circuit diagram of the noise filter 10d. 15 and 16, the same components as those in FIGS. 2 and 3 are denoted by the same reference numerals.

  As shown in FIGS. 15 and 16, the noise filter 10d is different from the noise filter 10a shown in FIGS. 2 and 3 in that capacitors C9 to C12 are provided instead of the capacitors C1 to C4. Hereinafter, the difference between the stacked body 12c and the stacked body 12a will be mainly described.

  In the noise filter 10d, as shown in FIG. 15, dielectric layers 16c and 16d on which capacitor electrodes 100 to 102 are formed are inserted in the middle of the coils L1 and L4. Similarly, dielectric layers 16n and 16o in which capacitor electrodes 105 to 107 are formed are inserted in the middle of the coils L2 and L3.

  More specifically, the dielectric layers 16c and 16d are disposed between the dielectric layer 16b and the dielectric layer 16e. The capacitor electrodes 100 and 101 are connected to the coils L1 and L4, respectively, and the capacitor electrode 102 is not connected to the coils L1 and L4. However, the capacitor electrode 102 is provided with lead portions 103 and 104 connected to the external electrodes E9 and E12. Thereby, the capacitors C9 and C12 are connected between the coils L1 and L4 and the external electrodes E9 and E10 as shown in FIG.

  The dielectric layers 16n and 16o are disposed between the dielectric layer 16m and the dielectric layer 16p. The capacitor electrodes 105 and 106 are connected to the coils L2 and L3, and the capacitor electrode 107 is not connected to the coils L2 and L3. However, the capacitor electrode 107 is provided with lead portions 108 and 109 connected to the external electrodes E9 and E10. Accordingly, the capacitors C10 and C11 are connected between the coils L1 and L4 and the external electrodes E9 and E10 as shown in FIG.

  The noise filter 10d is added with capacitors C9 to C12 and has a T-type structure, whereby the insertion loss of normal mode noise and common mode noise can be increased sharply.

  In the noise filter 10d, as in the noise filter 10a, the coil axis of the coil L1 and the coil axis of the coil L2 are matched when viewed in plan from the z-axis direction, and the coil L1 and the coil L2 are aligned in the z-axis direction. Are partially overlapped. Similarly, the coil axis of the coil L3 and the coil axis of the coil L4 are matched when viewed in plan from the z-axis direction, and the coil L4 and the coil L4 are partially overlapped in the z-axis direction. Yes. However, the method of coupling the coil L1 and the coil L2 and the method of coupling the coil L3 and the coil L4 are not limited to this. In the noise filter 10d, unlike the noise filter 10b, the coil axis of the coil L1 and the coil axis of the coil L2 are not overlapped when viewed in plan from the z-axis direction, and in the z-axis direction, the coil L1 and the coil L2 are not overlapped. And may be overlapped in a state in which. Similarly, when the coil axis of the coil L3 and the coil axis of the coil L4 are not overlapped when viewed in plan from the z-axis direction, the coil L3 and the coil L4 are overlapped with each other in the z-axis direction. It may be allowed.

(Fifth embodiment)
The configuration of the noise filter 10e according to the fifth embodiment will be described below with reference to the drawings. FIG. 17 is an exploded perspective view of the multilayer body 12e of the noise filter 10e according to the fifth embodiment. FIG. 18 is an equivalent circuit diagram of the noise filter 10e. 17 and 18, the same components as those in FIGS. 2, 3, 15, and 16 are denoted by the same reference numerals.

  The noise filter 10e has a structure in which a noise filter 10a and a noise filter 10d are combined. Specifically, the noise filter 10e has a structure in which capacitors C9 to C12 of the noise filter 10d are added to the noise filter 10a. As a result, the noise filter 10e has a structure in which L-type LC filters are connected in series as shown in FIG.

  In the noise filter 10e, as in the noise filter 10a, the coil axis of the coil L1 and the coil axis of the coil L2 are matched when viewed in plan from the z-axis direction, and the coil L1 and the coil L2 are aligned in the z-axis direction. Are partially overlapped. Similarly, the coil axis of the coil L3 and the coil axis of the coil L4 are matched when viewed in plan from the z-axis direction, and the coil L4 and the coil L4 are partially overlapped in the z-axis direction. Yes. However, the method of coupling the coil L1 and the coil L2 and the method of coupling the coil L3 and the coil L4 are not limited to this. In the noise filter 10e, unlike the noise filter 10b, the coil axis of the coil L1 and the coil axis of the coil L2 are not overlapped when viewed in plan from the z-axis direction, and the coil L1 and the coil L2 are not overlapped in the z-axis direction. And may be overlapped in a state in which. Similarly, when the coil axis of the coil L3 and the coil axis of the coil L4 are not overlapped when viewed in plan from the z-axis direction, the coil L3 and the coil L4 are overlapped with each other in the z-axis direction. It may be allowed.

(Sixth embodiment)
The configuration of the noise filter 10f according to the sixth embodiment will be described below with reference to the drawings. FIG. 19 is an exploded perspective view of the multilayer body 12f of the noise filter 10f according to the sixth embodiment. 19, the same components as those in FIG. 2 are given the same reference numerals.

  As shown in FIG. 19, the laminated body 12f is different from the laminated body 12a shown in FIG. 2 in that dielectric layers 16c and 16q provided with coupling electrodes 120 and 121 are provided. Hereinafter, differences between the laminated body 12f and the laminated body 12a will be described.

  As shown in FIG. 19, the coupling electrode 120 is an electrode for capacitively coupling the coil L1 and the coil L4, and is a strip-like electrode extending in the x-axis direction. The coupling electrode 120 is provided between the coils L1 and L4 and the capacitors C1 to C4 in the z-axis direction. Further, the coupling electrode 120 is provided so as to overlap the coil L1 and the coil L4 when viewed in plan from the z-axis direction. Thereby, a parasitic capacitance is formed between the coil L1 and the coil L4.

  The coupling electrode 121 is an electrode for capacitively coupling the coil L2 and the coil L3, and is a strip-like electrode extending in the x-axis direction. The coupling electrode 121 is provided between the coils L2 and L3 and the capacitors C1 to C4 in the z-axis direction. The coupling electrode 121 is provided so as to overlap with the coil L2 and the coil L3 when viewed in plan from the z-axis direction. Thereby, a parasitic capacitance is formed between the coil L2 and the coil L3.

  As described above, in the noise filter 10f, the coupling electrodes 120 and 121 are provided. The coupling electrodes 120 and 121 capacitively couple a set including the coils L1 and L2 and a set including the coils L3 and L4. Thereby, the noise filter 10f can suppress the reflection of the common mode noise as compared with the noise filter without the coupling electrodes 120 and 121.

  In the noise filter 10f, similarly to the noise filter 10a, the coil axis of the coil L1 and the coil axis of the coil L2 are matched when viewed in plan from the z-axis direction, and the coil L1 and the coil L2 are aligned in the z-axis direction. Are partially overlapped. Similarly, the coil axis of the coil L3 and the coil axis of the coil L4 are matched when viewed in plan from the z-axis direction, and the coil L4 and the coil L4 are partially overlapped in the z-axis direction. Yes. However, the method of coupling the coil L1 and the coil L2 and the method of coupling the coil L3 and the coil L4 are not limited to this. In the noise filter 10f, unlike the noise filter 10b, the coil axis of the coil L1 and the coil axis of the coil L2 are not overlapped when viewed in plan from the z-axis direction, and the coil L1 and the coil L2 in the z-axis direction are not overlapped. And may be overlapped in a state in which. Similarly, when the coil axis of the coil L3 and the coil axis of the coil L4 are not overlapped when viewed in plan from the z-axis direction, the coil L3 and the coil L4 are overlapped with each other in the z-axis direction. It may be allowed.

  In addition, the coupling electrodes 120 and 121 may be provided in the noise filters 10b to 10e.

1 is an external perspective view of a noise filter according to an embodiment of the present invention. It is an exploded view of the laminated body of the noise filter which concerns on 1st Embodiment. It is an equivalent circuit diagram of the noise filter according to the first embodiment. In the noise filter, it is a graph showing the relationship between the insertion loss of normal mode noise and the frequency when the coupling coefficient between the coil L1 and the coil L2 and the coupling coefficient between the coil L3 and the coil L4 are 0.2. In the noise filter, it is a graph showing the relationship between the insertion loss of normal mode noise and the frequency when the coupling coefficient between the coil L1 and the coil L2 and the coupling coefficient between the coil L3 and the coil L4 are 0.3. In the noise filter, it is a graph showing the relationship between the insertion loss of normal mode noise and the frequency when the coupling coefficient between the coil L1 and the coil L2 and the coupling coefficient between the coil L3 and the coil L4 are 0.6. In the noise filter, it is a graph showing the relationship between the insertion loss of normal mode noise and the frequency when the coupling coefficient between the coil L1 and the coil L2 and the coupling coefficient between the coil L3 and the coil L4 are 0.7. It is the graph which showed the result at the time of performing a 1st experiment in the 1st example of an experiment. It is the graph which showed the result at the time of performing a 1st experiment in the 2nd example of an experiment. It is the graph which showed the result at the time of performing a 2nd experiment in the 2nd experiment example. It is the graph which showed the result at the time of performing a 2nd experiment in the 1st experiment example. It is a disassembled perspective view of the laminated body of the noise filter which concerns on 2nd Embodiment. It is a disassembled perspective view of the laminated body of the noise filter which concerns on 3rd Embodiment. FIG. 14 is an equivalent circuit diagram of the noise filter of FIG. 13. It is a disassembled perspective view of the laminated body of the noise filter which concerns on 4th Embodiment. FIG. 16 is an equivalent circuit diagram of the noise filter of FIG. 15. It is a disassembled perspective view of the laminated body of the noise filter which concerns on 5th Embodiment. FIG. 18 is an equivalent circuit diagram of the noise filter of FIG. 17. It is a disassembled perspective view of the laminated body of the noise filter which concerns on 6th Embodiment.

Explanation of symbols

C1 to C12 Capacitors L1 to L4 Coils L11 and L12 Common mode choke coils LC1 to LC4 LC filters 10a to 10f Noise filters 12a to 12f Laminates 14a to 14f, 16a to 16u Dielectric layers 30a to 30h, 32a to 32h, 34a to 34h, 36a to 36h Coil electrode 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 80, 82, 84, 86 Capacitor electrode E1 to E10 External electrode

Claims (9)

A first LC filter including a first coil;
A second LC filter including a second coil;
A laminated body in which the first LC filter and the second LC filter are incorporated, and a plurality of insulating layers are laminated;
With
The second coil overlaps the first coil in the stacking direction, and overlaps the first coil when viewed in plan from the stacking direction;
Noise filter characterized by. The second coil partially overlaps the first coil in the stacking direction,
The coil axis of the first coil and the coil axis of the second coil overlap when viewed in plan from the stacking direction;
The noise filter according to claim 1. The second coil overlaps with the first coil in a stacking direction,
The coil axis of the first coil and the coil axis of the second coil do not overlap when viewed in plan from the stacking direction;
The noise filter according to claim 1. The first LC filter includes a first capacitor;
The second LC filter includes a second capacitor;
The first coil and the second coil are provided between the first capacitor and the second capacitor in the stacking direction;
The noise filter according to any one of claims 1 to 3, wherein: The first coil and the second coil are magnetically coupled with a coupling coefficient of 0.3 to 0.6;
The noise filter according to claim 1, wherein: A third LC filter including a third coil;
A fourth LC filter including a fourth coil;
Further comprising
The first coil and the third coil are capacitively coupled;
The noise filter according to any one of claims 1 to 5, wherein: The fourth coil overlaps with the third coil in the stacking direction, and overlaps with the third coil when viewed in plan from the stacking direction;
The noise filter according to claim 6. The third LC filter includes a third capacitor;
The fourth LC filter includes a fourth capacitor;
The third coil and the fourth coil are provided between the third capacitor and the fourth capacitor in the stacking direction;
The noise filter according to claim 6, wherein: A capacitive coupling electrode provided so as to overlap the first coil and the third coil when viewed in plan from the stacking direction;
More
The noise filter according to claim 6, wherein:

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