Noise filter

The present invention relates to a noise filter and a noise filter having a built-in common mode choke coil.

A differential transmission method may be used as a signal transmission method between a mobile phone driver and a receiver . In the differential transmission method, since the sum of the currents of the differential signals transmitting the two signal lines is constant, theoretically, common mode noise does not occur.

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

Further, in the differential transmission method, depending on the standard (for example, 3GPP), it is necessary to remove high-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, a noise filter suitable for common mode noise countermeasures and normal mode noise countermeasures between a mobile phone driver and a receiver is desired.

As a conventional noise filter, for example, the laminated array component described in Patent Document 1 is known. However, since the stacked array component is a noise filter for removing normal mode noise, it excessively removes normal mode noise, that is, harmonic signals constituting a differential signal, and deteriorates waveform quality.<patcit num="1"><text>Japanese Patent Application Laid-Open No. 2005-64267</text></patcit>

<p> Therefore, 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 of the quality of the differential signal waveform. ..</p>

<p> The noise filter according to one embodiment 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. The second coil overlaps with the first coil in the stacking direction and is flat from the stacking direction. It is characterized in that it overlaps with the first coil when viewed.</p>

<p> According to the present invention, since it is easy to set the coupling coefficient of the two coils to 0.3 or more and 0.6 or less, transmission between the driver and the receiver of the mobile phone is suppressed while suppressing deterioration of the quality of the differential signal waveform. Common mode noise and normal mode noise can be effectively removed.</p>

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 the noise filters 10a to 10f according to the embodiment of the present invention. FIG. 2 is an exploded view of the laminated body 12a of the noise filter 10a. FIG. 3 is an equivalent circuit diagram of the noise filter 10a. In the following, the direction in which the ceramic green sheets are laminated when the noise filter 10a is formed is defined as the stacking direction. Then, 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 make up the noise filter 10a.

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

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

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

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, 56 are drawers for connecting the capacitor electrodes 50, 52, 54, 56 and the external electrodes E2, E4, E6, E8 at the end on the negative side in the y-axis direction, respectively. It has parts 51,53,55,57. Further, 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-out 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 C1 is formed by the capacitor electrode 50 and the capacitor electrode 58 facing each other with the dielectric layer 16a interposed therebetween. The capacitor C2 is formed by the capacitor electrode 52 and the capacitor electrode 58 facing each other with the dielectric layer 16a interposed therebetween. The capacitor C3 is formed by the capacitor electrode 54 and the capacitor electrode 58 facing each other with the dielectric layer 16a interposed therebetween. The capacitor C4 is formed by the capacitor electrode 56 and the capacitor electrode 58 facing each other with the dielectric layer 16a interposed therebetween.

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

Further, via conductors b1 to b8 and b21 to b28 are provided on the dielectric layers 16c to 16j, respectively. The via conductors b1 to b4 and b6 to b8 are connected to one end of the coil electrodes 30a to 30h. Further, 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 end of the coil electrodes 34a to 34h. Further, the via conductor b25 connects the via conductor b24 and the via conductor b26. As a result, when the dielectric layers 16c to 16k are laminated, the via conductors b1 to b8 and b21 to b28 connect the coil electrodes 30a to 30h and 34a to 34h adjacent to each other in the z-axis direction. As a result, the coil electrodes 30a to 30h form the coil L1, and the coil electrodes 34a to 34h form the coil L4.

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

Further, via conductors b11 to b18 and b31 to b38 are provided on the dielectric layers 16g to 16n, respectively. The via conductors b11 to b14 and b16 to b18 are connected to one end of the coil electrodes 32a to 32h. Further, 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 end of the coil electrodes 36a to 36h. Further, the via conductor b35 connects the via conductor b34 and the via conductor b36. As a result, when the dielectric layers 16g to 16n are laminated, the via conductors b11 to b18 and b31 to b38 connect the coil electrodes 32a to 32h and 36a to 36h adjacent to each other in the z-axis direction. As a result, the coil electrodes 32a to 32h form the coil L2, and the coil electrodes 36a to 36h form 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 60,62,64,66 are drawers for connecting the capacitor electrodes 60,62,64,66 and the external electrodes E2, E4, E6, E8 at the end on the negative side in the y-axis direction, respectively. It has parts 61,63,65,67. Further, 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-out 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.

The capacitor C1 is formed by the capacitor electrode 60 and the capacitor electrode 68 facing each other with the dielectric layer 16p interposed therebetween. The capacitor C2 is formed by the capacitor electrode 62 and the capacitor electrode 68 facing each other with the dielectric layer 16p interposed therebetween. The capacitor C3 is formed by the capacitor electrode 64 and the capacitor electrode 68 facing each other with the dielectric layer 16p interposed therebetween. The capacitor C4 is formed by the capacitor electrode 66 and the capacitor electrode 68 facing each other with the dielectric layer 16p interposed therebetween.

As the laminate 12a has the above configuration, as shown in FIG. 3, it is composed of an LC filter LC1 composed of a coil L1 and a capacitor C1, an LC filter LC2 composed of a coil L2 and a capacitor C2, a coil L3 and a capacitor C3. An LC filter LC3 and an LC filter LC4 composed of a coil L4 and a capacitor C4 are 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. Further, 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 configurations of the LC filter LC1, so the description thereof will be 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, a current flows through the coil L1 from top to bottom in the z-axis direction. , For example, a current flows through the coil L2 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 from the top to the bottom in the z-axis direction, and the coil electrodes 34a to 34f constituting the coil L2 rotate from above in the z-axis direction. It turns counterclockwise as it goes down. That is, the coil L1 and the coil L2 rotate in opposite directions to each other. Therefore, when a current flows through the coil L1 and the coil L2, the currents rotate in the same direction. Further, the coil L1 and the coil L2 are configured to be wound by a bifilar. 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 a plan view from the z-axis direction. It is arranged. Further, the coil L2 partially overlaps with the coil L1 in the dielectric layer 16g to 16k in the z-axis direction. As a result, the coil L1 and the coil L2 are magnetically coupled by generating magnetic flux in the same direction, so that the coil L1 constituting the LC filter LC1 and the coil L2 constituting the LC filter LC2 are common mode choke coils. It also functions as L11. The coil L3 that constitutes the LC filter LC3 and the coil L4 that constitutes 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. Omit.

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

In particular, in the noise filter 10a, as shown in FIG. 2, when viewed in a plan view from the z-axis direction, the coil shaft of the coil L1 and the coil shaft of the coil L2 coincide with each other, and a part of the coil L1 and the coil A 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, it becomes easy to connect 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, this appropriate coupling coefficient is 0.3 or more and 0.6 or less. Then, by setting the coupling coefficient between the coil L1 and the coil L2 and the coupling coefficient between the coil L3 and the coil L4 to 0.3 or more and 0.6 or less, the normal generated in the differential signal transmitted between the driver and the receiver of the mobile phone is generated. Mode noise can be effectively removed.

More specifically, the inventor of the present application has performed a computer simulation described below in order to confirm the effect of the noise filter 10a. FIGS. 4 to 7 are graphs showing the results of 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. It is a graph which showed the relationship between the insertion loss of a normal mode noise, and a frequency at the time of. The vertical axis shows the noise insertion loss, and the horizontal axis shows the frequency.

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

Further, the insertion loss of normal mode noise near 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, it is possible to remove the common mode noise generated between the driver and the receiver of the mobile phone. Further, 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 0.3 or more and 0.6 or less, so that the noise filter 10a is normal while suppressing deterioration of the differential signal waveform. Mode noise can also be removed. Therefore, the noise filter 10a is suitable for measures against common mode noise and measures against normal mode noise between the driver and the receiver of the mobile phone.

Next, the inventor of the present application conducted an experiment in order to clarify the effect of the noise filter 10a. More specifically, a first experimental example corresponding to the noise filter 10a was prepared, and a second experimental example corresponding to the stacked array component described in Patent Document 1 was prepared. The coupling coefficient of the second experimental example was set to 0.05 or less. Then, as the first experiment, a square wave was input to these experimental examples, and the output signal was measured. In addition, 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 of the first experiment in the first experimental example. FIG. 9 is a graph showing the results of the first experiment in the second experimental example. In FIGS. 8 and 9, the vertical axis represents the signal level and the horizontal axis represents time.

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

In the first experiment, when a square wave was input to the first experimental example and the second experimental example, noise at high frequencies was removed, and as shown in FIGS. 8 and 9, the first experimental example and the second experimental example were used. A sinusoidal signal was output in both of the two experimental examples. Comparing FIG. 8 and FIG. 9, the output signal of FIG. 8 has a steeper rise and fall than the output signal of FIG. 9, and has a waveform close to that of 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 deterioration of the output signal in the noise filter 10a is smaller than the deterioration of the output signal in the stacked array component described in Patent Document 1.

Further, in the second experiment, noise having the same intensity distribution was input to the first experimental example and the second experimental 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 removing effect of the noise filter 10a is equivalent to the noise removing effect of the laminated 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 removing effect while reducing the deterioration of the waveform of the output signal.

Further, according to the noise filter 10a, since the LC filter and the common mode choke coil are built in one noise filter 10a, when the LC filter and the common mode choke coil are composed of separate electronic components. Compared to, the entire circuit can be miniaturized. In particular, in the noise filter 10a, the coils L1 and L2 function as the common mode choke coil L11 and also function as a 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 a part of the LC filters LC3 and LC4. As described above, in the noise filter 10a, since the coils L1 to L4 are also used as a part of the LC filter and a part of the common mode choke coil, the noise filter 10a is further miniaturized.

Further, the noise filter 10a can efficiently remove common mode noise as described below. In the xz cross section, if 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 the common mode noise. As a result, new common mode noise is generated, and the common mode noise cannot be removed efficiently. 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 cross section. Similarly, in the xz cross 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 to each other. As a result, 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, the normal mode noise is not converted into the common mode noise, and new common mode noise is not generated. Therefore, in the noise filter 10a, the common mode choke coil L11 and the common mode choke coil L12 can remove the common mode noise more efficiently.

In addition, if the capacitor electrodes are not line-symmetrical with respect to the dielectric layer 16i in the xz cross section, the magnitudes of the magnetic fluxes are unlikely to be equal, so normal mode noise is converted to common mode noise, and a new common is created. Mode noise is generated and common mode noise is not removed efficiently. On the other hand, as shown in FIG. 2, the capacitor electrodes 50,52,58,60,62,68 are on the boundary line between the LC filter LC1 and the LC filter LC2 (dielectric layer 16i in FIG. 2) in the xz cross section. On the other hand, it has a substantially axisymmetric structure. Similarly, as shown in FIG. 2, the capacitor electrodes 54,56,58,64,66,68 are on the boundary line between the LC filter LC3 and the LC filter LC4 (dielectric layer 16i in FIG. 2) in the xz cross section. On the other hand, it has a substantially axisymmetric structure. As a result, the influence of the capacitor electrodes 50,52,58 on the magnetic flux of the coil L1 and the influence of the capacitor electrodes 60,62,68 on the magnetic flux of the coil L2 can be equalized. Similarly, the effect of the capacitor electrodes 54,56,58 on the magnetic flux of the coil L4 can be equalized with the effect of the capacitor electrodes 64,66,68 on the magnetic flux of 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 made smaller. Therefore, the normal mode noise is not converted into the common mode noise, and new common mode noise is not generated. Therefore, in the noise filter 10a, the common mode choke coil L11 and the common mode choke coil L12 can remove the common mode noise more efficiently.

Further, in the noise filter 10a, as shown in FIG. 2, the coils L1 and L2 are laminated so as to be located 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 strengthened, the removal characteristics of the normal mode noise 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 strengthened. This makes it possible to improve the common mode noise removal characteristics of the common mode choke coil L11. 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 laminated body 12b of the noise filter 10b according to the second embodiment. Since the external perspective view and the equivalent circuit diagram of the noise filter 10b are the same as those of the noise filter 10a, FIGS. 1 and 3 are used. In FIG. 12, the same reference numerals are given to the same configurations as those in FIG.

The difference between the noise filter 10a and the noise filter 10b is how to connect the coil L1 and the coil L2 and how to connect the coil L3 and the coil L4. More specifically, in the noise filter 10a, the coil shaft of the coil L1 and the coil shaft of the coil L2 are matched when viewed in a plan view from the z-axis direction, and the coil L1 and the coil L2 are partially aligned in the z-axis direction. It overlaps with each other. Similarly, the coil shaft of the coil L3 and the coil shaft of the coil L4 are matched when viewed in a plan view from the z-axis direction, and the coil L4 and the coil L4 are partially overlapped in the z-axis direction. There is.

On the other hand, in the noise filter 10b, the coil shaft of the coil L1 and the coil shaft of the coil L2 are not overlapped when viewed in a plan view from the z-axis direction, and the coil L1 and the coil L2 are matched in the z-axis direction. It overlaps in the state. The coil shaft of the coil L3 and the coil shaft of the coil L4 are not overlapped when viewed in a plan view from the z-axis direction, and the coil L3 and the coil L4 are overlapped in the z-axis direction in a aligned state. ..

More specifically, the coils L1 to L4 are provided in the dielectric layers 16c to 16i, and are provided in the regions that coincide with each other in the z-axis direction. Then, the coil shaft of the coil L1 and the coil shaft of the coil L2 are arranged so as not to match when viewed in a plan view from the z-axis direction. However, the coil L1 and the coil L2 overlap when viewed in a plan view from the z-axis direction. Similarly, the coil shaft of the coil L3 and the coil shaft of the coil L4 are arranged so as not to match when viewed in a plan view from the z-axis direction. However, the coil L3 and the coil L4 overlap when viewed in a plan view from the z-axis direction.

Similar to the noise filter 10a, the noise filter 10b as described above can also remove both the normal mode noise and the common mode noise.

In particular, in the noise filter 10b, as shown in FIG. 12, the coil axis of the coil L1 and the coil axis of the coil L2 do not overlap when viewed in a plan view from the z-axis direction. At the same time, the coil L1 and the coil L2 are overlapped in the z-axis direction in a matched state. Therefore, by adjusting the amount of deviation between the coil shaft of the coil L1 and the coil shaft 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, this appropriate coupling coefficient is 0.3 or more and 0.6 or less. Then, by setting the coupling coefficient between the coil L1 and the coil L2 and the coupling coefficient between the coil L3 and the coil L4 to 0.3 or more and 0.6 or less, the normal generated in the differential signal transmitted between the driver and the receiver of the mobile phone is generated. Mode noise can be effectively removed.

(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 laminated body 12c of the noise filter 10c according to the third embodiment. FIG. 14 is an equivalent circuit diagram of the noise filter 10c. In FIGS. 13 and 14, the same reference numerals are given to the same configurations as those in FIGS. 2 and 3.

As shown in FIG. 13, the laminate 12c is different from the laminate 12a in that the capacitor electrodes 80,82,84,86,90,92,94,96 are formed on the dielectric layers 16a and 16q, respectively. It's different. Hereinafter, the differences between the laminated body 12c and the laminated 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 form a capacitor C5 by facing each other with a dielectric layer 16a interposed therebetween. The capacitor electrode 82 and the capacitor electrode 58 form a capacitor C6 by facing each other with a dielectric layer 16a interposed therebetween. The capacitor electrode 84 and the capacitor electrode 58 form a capacitor C7 by facing each other with a dielectric layer 16a interposed therebetween. The capacitor electrode 86 and the capacitor electrode 58 form a capacitor C8 by facing each other with a dielectric layer 16a interposed therebetween.

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

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

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

The noise filter 10c can have a steep and large insertion loss of normal mode noise and common mode noise by adding capacitors C5 to C8 and adopting a Π type structure.

In the noise filter 10c, similarly to the noise filter 10a, the coil shaft of the coil L1 and the coil shaft of the coil L2 are matched when viewed in a plan view from the z-axis direction, and the coil L1 and the coil L2 are matched in the z-axis direction. And are partially overlapped. Similarly, the coil shaft of the coil L3 and the coil shaft of the coil L4 are matched when viewed in a plan view from the z-axis direction, and the coil L3 and the coil L4 are partially overlapped in the z-axis direction. There is. 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 shaft of the coil L1 and the coil shaft of the coil L2 are not overlapped when viewed in a plan view from the z-axis direction, and the coil L1 and the coil L2 are not overlapped in the z-axis direction. May be overlapped in a state where and are matched. Similarly, if the coil shaft of the coil L3 and the coil shaft of the coil L4 are not overlapped when viewed in a plan view from the z-axis direction, and if the coil L3 and the coil L4 are overlapped in the z-axis direction, they are overlapped. You may let it.

(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 laminated body 12d of the noise filter 10d according to the fourth embodiment. FIG. 16 is an equivalent circuit diagram of the noise filter 10d. In FIGS. 15 and 16, the same reference numerals are given to the same configurations as those in FIGS. 2 and 3.

As shown in FIGS. 15 and 16, the noise filter 10d differs 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 differences between the laminated body 12c and the laminated body 12a will be mainly described.

In the noise filter 10d, as shown in FIG. 15, the dielectric layers 16c and 16d on which the capacitor electrodes 100 to 102 are formed are inserted in the middle of the coils L1 and L4. Similarly, the dielectric layers 16n and 16o on which the 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 arranged 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 electrodes 102 are not connected to the coils L1 and L4, respectively. However, the capacitor electrode 102 is provided with lead-out portions 103 and 104 connected to the external electrodes E9 and E12. As a result, the capacitors C9 and C12 are connected between the middle of the coils L1 and L4 and the external electrodes E9 and E10, as shown in FIG.

The dielectric layers 16n and 16o are arranged 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 electrodes 107 are not connected to the coils L2 and L3. However, the capacitor electrode 107 is provided with lead-out portions 108 and 109 connected to the external electrodes E9 and E10. As a result, the capacitors C10 and C11 are connected between the middle of the coils L1 and L4 and the external electrodes E9 and E10, as shown in FIG.

The noise filter 10d has a T-shaped structure with the addition of capacitors C9 to C12, so that the insertion loss of normal mode noise and common mode noise can be steeply and increased.

In the noise filter 10d, similarly to the noise filter 10a, the coil shaft of the coil L1 and the coil shaft of the coil L2 are matched when viewed in a plan view from the z-axis direction, and the coil L1 and the coil L2 are matched in the z-axis direction. And are partially overlapped. Similarly, the coil shaft of the coil L3 and the coil shaft of the coil L4 are matched when viewed in a plan view from the z-axis direction, and the coil L4 and the coil L4 are partially overlapped in the z-axis direction. There is. 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 shaft of the coil L1 and the coil shaft of the coil L2 are not overlapped when viewed in a plan view from the z-axis direction, and the coil L1 and the coil L2 are not overlapped in the z-axis direction. May be overlapped in a state where and are matched. Similarly, if the coil shaft of the coil L3 and the coil shaft of the coil L4 are not overlapped when viewed in a plan view from the z-axis direction, and if the coil L3 and the coil L4 are overlapped in the z-axis direction, they are overlapped. You may let me.

(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 laminated body 12e of the noise filter 10e according to the fifth embodiment. FIG. 18 is an equivalent circuit diagram of the noise filter 10e. In FIGS. 17 and 18, the same reference numerals are given to the same configurations as those in FIGS. 2, 3, 15, and 16.

The noise filter 10e has a structure in which the noise filter 10a and the 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 LC filters having an L-shaped structure are connected in series, as shown in FIG.

In the noise filter 10e, similarly to the noise filter 10a, the coil shaft of the coil L1 and the coil shaft of the coil L2 are matched when viewed in a plan view from the z-axis direction, and the coil L1 and the coil L2 are matched in the z-axis direction. And are partially overlapped. Similarly, the coil shaft of the coil L3 and the coil shaft of the coil L4 are matched when viewed in a plan view from the z-axis direction, and the coil L4 and the coil L4 are partially overlapped in the z-axis direction. There is. 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 shaft of the coil L1 and the coil shaft of the coil L2 are not overlapped when viewed in a plan view from the z-axis direction, and the coil L1 and the coil L2 are not overlapped in the z-axis direction. May be overlapped in a state where and are matched. Similarly, if the coil shaft of the coil L3 and the coil shaft of the coil L4 are not overlapped when viewed in a plan view from the z-axis direction, and if the coil L3 and the coil L4 are overlapped in the z-axis direction, they are overlapped. You may let it.

(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 laminated body 12f of the noise filter 10f according to the sixth embodiment. In FIG. 19, the same reference numerals are given to the same configurations as those in FIG.

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

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-shaped 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 a plan view from the z-axis direction. As a result, a parasitic capacitance is formed between the coil L1 and the coil L4.

Further, the coupling electrode 121 is an electrode for capacitively coupling the coil L2 and the coil L3, and is a strip-shaped 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. Further, the coupling electrode 121 is provided so as to overlap the coil L2 and the coil L3 when viewed in a plan view from the z-axis direction. As a result, a parasitic capacitance is formed between the coil L2 and the coil L3.

As described above, the noise filter 10f is provided with coupling electrodes 120 and 121. The coupling electrodes 120 and 121 capacitively couple a set of coils L1 and L2 and a set of coils L3 and L4. As a result, the noise filter 10f can suppress the reflection of common mode noise more than the noise filter without the coupling electrodes 120 and 121.

In the noise filter 10f, similarly to the noise filter 10a, the coil shaft of the coil L1 and the coil shaft of the coil L2 are matched when viewed in a plan view from the z-axis direction, and the coil L1 and the coil L2 are matched in the z-axis direction. And are partially overlapped. Similarly, the coil shaft of the coil L3 and the coil shaft of the coil L4 are matched when viewed in a plan view from the z-axis direction, and the coil L4 and the coil L4 are partially overlapped in the z-axis direction. There is. 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 shaft of the coil L1 and the coil shaft of the coil L2 are not overlapped when viewed in a plan view from the z-axis direction, and the coil L1 and the coil L2 are not overlapped in the z-axis direction. May be overlapped in a state where and are matched. Similarly, if the coil shaft of the coil L3 and the coil shaft of the coil L4 are not overlapped when viewed in a plan view from the z-axis direction, and if the coil L3 and the coil L4 are overlapped in the z-axis direction, they are overlapped. You may let it.

The noise filters 10b to 10e may be provided with coupling electrodes 120 and 121.

<figref num="1">It is external perspective view of the noise filter which concerns on embodiment of this invention.</figref><figref num="2">It is an exploded view of the laminated body of the noise filter which concerns on 1st Embodiment.</figref><figref num="3">It is an equivalent circuit diagram of the noise filter which concerns on 1st Embodiment.</figref><figref num="4">It is a graph which showed the relationship between the insertion loss of a normal mode noise, and a frequency when the coupling coefficient of coil L1 and coil L2 and the coupling coefficient of coil L3 and coil L4 is 0.2 in a noise filter.</figref><figref num="5">It is a graph which showed the relationship between the insertion loss of a normal mode noise, and a frequency when the coupling coefficient of coil L1 and coil L2 and the coupling coefficient of coil L3 and coil L4 is 0.3 in a noise filter.</figref><figref num="6">It is a graph which showed the relationship between the insertion loss of a normal mode noise, and a frequency when the coupling coefficient of coil L1 and coil L2 and the coupling coefficient of coil L3 and coil L4 is 0.6 in a noise filter.</figref><figref num="7">It is a graph which showed the relationship between the insertion loss of a normal mode noise, and a frequency when the coupling coefficient of coil L1 and coil L2 and the coupling coefficient of coil L3 and coil L4 is 0.7 in a noise filter.</figref><figref num="8">It is a graph which showed the result when the 1st experiment was performed in the 1st experimental example.</figref><figref num="9">It is a graph which showed the result when the 1st experiment was performed in the 2nd experimental example.</figref><figref num="10">It is a graph which showed the result when the 2nd experiment was performed in the 2nd experimental example.</figref><figref num="11">It is a graph which showed the result when the 2nd experiment was performed in the 1st experimental example.</figref><figref num="12">It is an exploded perspective view of the laminated body of the noise filter which concerns on 2nd Embodiment.</figref><figref num="13">It is an exploded perspective view of the laminated body of the noise filter which concerns on 3rd Embodiment.</figref><figref num="14">It is an equivalent circuit diagram of the noise filter of FIG.</figref><figref num="15">It is an exploded perspective view of the laminated body of the noise filter which concerns on 4th Embodiment.</figref><figref num="16">It is an equivalent circuit diagram of the noise filter of FIG.</figref><figref num="17">It is an exploded perspective view of the laminated body of the noise filter which concerns on 5th Embodiment.</figref><figref num="18">It is an equivalent circuit diagram of the noise filter of FIG.</figref><figref num="19">It is an exploded perspective view of the laminated body of the noise filter which concerns on 6th Embodiment.</figref>

Code description

C1 ~ C12 capacitors L1 ~ L4 coil L11, L12 common mode choke coil LC1 ~ LC4 LC filter 10a ~ 10f noise filter 12a ~ 12f laminate 14a ~ 14f, 16a ~ 16u Dielectric layer 30a ~ 30h, 32a ~ 32h, 34a ~ 34h, 36a ~ 36h Coil electrode 50,52,54,56,58,60,62,64,66,68,80,82,84,86 Capacitor electrodes E1 ~ E10 External electrodes