JP5471556B2 - LC filter - Google Patents

Description

  The present invention relates to an LC filter, and more particularly, to an LC filter including a resonator composed of a capacitor and an inductor.

  2. Description of the Related Art Conventionally, as a small LC filter for high frequency such as a cellular phone, an LC filter including a resonator constituted by a capacitor and an inductor is provided on a chip body in which an insulating layer or a dielectric layer is laminated. In such an LC filter, as a method of forming an inductor, (1) a method of forming an inductor extending in a plane direction along the insulating layer or the dielectric layer, and (b) penetrating the insulating layer or the dielectric layer. A method of forming an inductor is known.

  For example, FIG. 10 is an exploded perspective view of an LC filter (band-pass filter) 120 in which an inductor is formed by the former method. As shown in FIG. 10, the LC filter 120 includes first, second, and third resonators. These resonators include three inductors formed by three conductor inductor patterns 124a to 124c formed in the plane direction along the insulating layer 122, three counter electrodes (capacitor electrodes) 140a to 140c, dielectrics And three capacitors formed by a body layer 142 and three counter electrodes (ground electrodes) 144a to 144c. The ground side of the first resonator is grounded via a first spurious improvement electrode 126a serving as a first spurious improvement inductor. The ground side of the third resonator is grounded via a second spurious improvement electrode 126b serving as a second spurious improvement inductor (see, for example, Patent Document 1).

  FIG. 11 is an exploded perspective view of an LC filter (laminated LC filter) 221 in which an inductor is formed by the latter method. As shown in FIG. 11, the LC filter 221 has through holes formed in the insulating layers 223 to 226 inside the laminated insulating layers 222 to 228, and the via hole conductors 230 a to 230 d for inductors are formed in these through holes. 231a to 231d are formed. The inductor via-hole conductors 230a to 230d and 231a to 231d are connected in the stacking direction of the insulating layers 222 to 228 to form columnar inductors L201 and L202. One ends (via holes 230a and 231a) of the inductors L201 and L202 are individually electrically connected to the ground external electrodes G1 and G2 (not shown) via the internal ground patterns 236 and 237, respectively, and external to the ground. A bridge pattern 235 that electrically connects the electrodes G1 and G2 (not shown) is disposed in the vicinity of the inductors L1 and L2 (see, for example, Patent Document 2).

JP-A-5-199006 Japanese Patent Laid-Open No. 2002-164761

  However, in any of the methods, it is difficult to obtain desired characteristics when the LC filter is downsized.

  In other words, in the method of forming an inductor extending in the plane direction along the insulating layer or the dielectric layer, when the physical length of the inductor pattern forming the inductor is shortened along with the downsizing of the LC filter, the same inductance is formed. In order to obtain the value, it is necessary to narrow the width of the inductor pattern. However, if the inductor pattern is made thinner, the resonance Q value becomes worse.

  Ideally, the cross-sectional shape of the inductor should be continuous in the direction of current flow so that the electromagnetic field does not concentrate when a high-frequency current flows. However, when the inductor pattern is formed by printing, the sectional shape of the inductor pattern becomes rectangular.

  On the other hand, in the method of forming an inductor penetrating the insulating layer or dielectric layer, the length of the via-hole conductor in the thickness direction of the insulating layer or dielectric layer determines the length of the inductor. Therefore, when the LC filter is made low in height, the absolute length of the inductor is insufficient. If a plurality of via-hole conductors are connected in series via in-plane connection conductors, the length of the inductor can be secured, but in this case, the inductor is bent at a right angle, resulting in a large signal loss.

  In addition, even if the cross-sectional shape of the via-hole conductor forming the inductor can be an ideal circle in the insulating layer or dielectric layer, the connection of the via-hole conductor is caused by the stacking error when the insulating layer or dielectric layer is stacked. When a step is generated on the surface, the cross-sectional shape of the inductor does not become an ideal circle at the step portion. Therefore, when a high-frequency current flows, an electromagnetic field is concentrated, which causes signal loss.

  In view of such circumstances, the present invention is intended to provide an LC filter that can easily obtain desired characteristics even if it is downsized.

  In order to solve the above problems, the present invention provides an LC filter configured as follows.

  The LC filter has (a) a dielectric layer and a counter electrode disposed so as to face each other with the dielectric layer interposed therebetween, and a capacitor is formed by the counter electrode and the dielectric layer between the counter electrodes. And (b) a mounting substrate on which the dielectric substrate is mounted. An inductor is formed on the dielectric substrate by a first bonding wire, and the inductor and the capacitor constitute a resonator. The dielectric substrate and the mounting substrate are connected by a second bonding wire. The first virtual surface including the first bonding wire and the second virtual surface including the second bonding wire are substantially perpendicular to each other.

  In the above configuration, the characteristics of the inductor are changed by changing the length and the cross-sectional diameter of the first bonding wire for the inductor. Since the first bonding wire has a circular cross-sectional shape and a constant circular shape continues in the direction in which the current flows, the signal loss is small when a high-frequency current flows. Therefore, an inductor having desired characteristics can be easily formed.

  According to the above configuration, since the first bonding wire for inductor and the second bonding wire for connection form an angle of approximately 90 °, the first bonding wire for inductor and the first bonding wire for connection Electromagnetic coupling with the second bonding wire is suppressed. Therefore, it is easy to obtain an LC filter having desired characteristics.

Furthermore, the first bonding wire is disposed so as to overlap the capacitor when viewed from the direction in which the counter electrode and the dielectric layer forming the capacitor overlap.

  In this case, when viewed from the stacking direction of the counter electrode of the capacitor and the dielectric layer, the bonding wire for the inductor is arranged so as to overlap the capacitor so that the bonding wire for the inductor does not overlap with the capacitor. Since the dielectric substrate can be made smaller than the arrangement, the LC filter can be downsized.

  Preferably, the first bonding wire is covered with a resin.

  In this case, the first bonding wire forming the inductor of the resonator can be fixed, and the characteristics and quality of the LC filter can be stabilized.

  Preferably, the adjacent first bonding wires have different shapes.

  In this case, since the magnetic coupling between the adjacent first bonding wires can be made as small as possible, the influence on the filter characteristics can be reduced even if the shape of the first bonding wire is deformed.

  Preferably, the adjacent first bonding wires are: (a) the interval between the ends on the same side is larger than the interval between the other ends on the other side, and (b) the one end side is relatively high, The other end side is relatively low.

  In the adjacent first bonding wires, the shorter the distance between the parallel parts, and the longer the parallel parts, the stronger the magnetic coupling. In the adjacent first bonding wires, when the interval between the relatively high one ends is made larger than the interval between the relatively low other ends, the interval between the relatively high ends is relatively low. The magnetic coupling is weaker than when the distance is smaller than. Since the magnetic coupling between the first bonding wires can be made as small as possible, the influence on the filter characteristics can be reduced even if the shape of the first bonding wire is deformed.

  Even if the LC filter of the present invention is downsized, desired characteristics can be easily obtained.

It is a perspective view of LC filter. Example 1 It is (a) top view and (b) side view of a dielectric substrate. Example 1 It is an equivalent circuit diagram of the LC filter. Example 1 It is a plane of a dielectric substrate. (Example 2) It is a perspective view of a dielectric substrate. (Example 2) It is a perspective view of a dielectric substrate. (Example 3) It is (a) perspective view and (b) side view of a dielectric substrate. Example 4 It is (a) top view and (b) side view of a dielectric substrate. (Example 5) It is (a) top view and (b) side view of a dielectric substrate. (Example 6) It is a disassembled perspective view of LC filter. (Conventional example 1) It is a disassembled perspective view of LC filter. (Conventional example 2)

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  Example 1 An LC filter 10 of Example 1 will be described with reference to FIGS.

  FIG. 1 is a perspective view of the LC filter 10. As shown in FIG. 1, the LC filter 10 has a dielectric substrate 20 mounted on a mounting substrate 12. The substrate body 13 of the mounting substrate 12 and the substrate body 22 of the dielectric substrate 20 may be any material that can be wire-bonded, such as alumina or ceramic, and a substrate such as GaS can also be used.

  FIG. 2A is a plan view of the dielectric substrate 20. FIG.2 (b) is the side view seen along line AA of Fig.2 (a). As shown in FIGS. 2A and 2B, the dielectric substrate 20 has an electrode pattern 23 and a pad electrode 25 formed on the upper surface 22 s which is one main surface of the substrate body 22. The electrode pattern 23 includes counter electrodes 23a, 23b, and 23c that form capacitors, and connection electrodes 24a and 24b. A back surface electrode (not shown) is formed on the lower surface 22 t which is the other main surface of the substrate body 22.

  The substrate body 22 includes one or more dielectric layers. The dielectric layer includes a first counter electrode (not shown) formed on or under the lower surface 22t of the substrate body 22, and second counter electrodes 23a, 23b formed on the upper surface 22s or inside of the substrate body 22. The capacitor is formed by the first and second counter electrodes and the dielectric layer between the first and second counter electrodes.

  A via hole conductor (not shown) penetrating the dielectric layer is formed in the substrate body 22 and is connected to the electrode pattern 23, the pad electrode, the counter electrode of the capacitor, and the back electrode. The substrate body 22 can be manufactured by a method similar to a conventional LC filter in which a capacitor and an inductor are formed on a substrate body on which a plurality of insulating layers or dielectric layers are stacked.

  The electrode pattern 23 and the pad electrode 25 formed on the upper surface 22 s of the substrate body 22 are connected by a first bonding wire 26, and an inductor is formed by the first bonding wire 26. As the first bonding wire 26, a bonding wire used for connection (wire bonding) of an IC chip or the like is used.

  Since bonding wires generally cause parasitic inductance and have an adverse effect, efforts are made to keep the inductance value low, and designs that take the inductance value into account are being performed. On the other hand, in the LC filter of the present invention, the bonding wire actively uses the formation of an inductor and is used as an inductor of a resonance circuit.

  The bonding wire has a circular shape with a constant cross-sectional shape at any position, and bends smoothly in an arc shape. Therefore, there is almost no concentrated electromagnetic field when a high-frequency current flows. Therefore, it is possible to make an LC filter having a higher Q value than when the cross-sectional shape of the inductor is rectangular or the step is formed in the inductor and the cross-sectional shape is not constant in the direction of current flow. For example, in the prototype of the LC filter 10 (for 2.4 GHz), the signal loss is about 1 dB better than when the inductor is formed by printing so as to extend in the plane direction along the insulating layer.

  FIG. 3 is an equivalent circuit diagram of the LC filter 10. Capacitors C1 to C3 formed on the substrate body 22 of the dielectric substrate 20, inductors L1 to L3 formed by the first bonding wires 26, and capacitive couplings C4 and C5 between the adjacent first bonding wires 26 Thus, an LC resonance circuit is configured.

  The inductance values of the inductors L1 to L3 change depending on the length of the first bonding wire 26, and the resonance frequency changes. The size of the capacitive couplings C4 and C5 varies depending on the distance between the adjacent first bonding wires 26. Therefore, different filter characteristics can be realized only by changing the length, connection position, diameter, and the like of the first bonding wire 26 with respect to the common substrate body 22.

  Since a plurality of filter characteristics can be realized by changing the diameter, height, shape, arrangement interval, and the like of the first bonding wire 26, the substrate body 22 can be shared and the cost can be reduced. Since it is not necessary to prepare a mold or a print pattern for each filter characteristic, it is easy to meet individual specifications. Adjustments can be made to the manufacturing variations in the capacitance characteristics of the capacitors C1 to C3 of the dielectric substrate 20 by changing the length, shape, diameter, and the like of the second bonding wire 26.

  As shown in FIG. 1, the dielectric substrate 20 is placed on the upper surface 13 s that is one main surface of the substrate body 13 of the mounting substrate 12. The dielectric substrate 20 and the mounting substrate 12 are connected by the second bonding wires 16a and 16b. That is, the pad electrodes 24a and 24b formed on the upper surface 22s of the substrate body 22 of the dielectric substrate 20 and the terminal electrodes 14a and 14b formed on the upper surface 13s of the substrate body 13 of the mounting substrate 12 are second bonded. They are connected by wires 16a and 16b. Further, a back electrode (not shown) formed on the lower surface 22t of the substrate body 22 of the dielectric substrate 20 and a terminal electrode (not shown) formed on the upper surface 13s of the substrate body 13 of the mounting substrate 12 are connected. Is done. As the second bonding wires 16a and 16b, bonding wires used for connection (wire bonding) of an IC chip or the like are used.

  The first bonding wire 26 for inductor and the second bonding wires 16a and 16b for connection form an angle of about 90 °. That is, the first virtual surface 26k including the first bonding wire 26 and the second virtual surface 16k including the second bonding wires 16a and 16b are substantially perpendicular. In addition, although the case where the 2nd bonding wires 16a and 16b are contained in the same 2nd virtual surface 16k is illustrated, the 2nd bonding wires 16a and 16b are respectively different 2nd virtual surfaces. May be included. The first virtual surface 26k can be determined by the two points 26u and 26v at both ends of the bonding wire 26 and the one point 26w at the intermediate portion. The second virtual surface 16k can be determined by the two points 16p, 16q; 16u, 16v at both ends of the bonding wires 16a, 16b and the one point 16r, 16w at the intermediate portion. The angle formed by the first virtual surface 26k and the second virtual surface 16k is at least 60 ° to 120 °, preferably 80 ° to 100 °, and more preferably 85 ° to 95 °. is there.

  Since the first bonding wire 26 for inductor and the second bonding wires 16a, 16b for connection form an angle of about 90 °, the first bonding wire 26 for inductor and the second bonding wire 26 for connection are formed. Since the electromagnetic coupling with the bonding wires 16a and 16b is suppressed, it is easy to obtain the LC filter 10 having desired characteristics.

  Example 2 An LC filter of Example 2 will be described with reference to FIGS. 4 and 5.

  The second embodiment has substantially the same configuration as the first embodiment. Below, it demonstrates centering around difference with Example 1, and uses the same code | symbol for the same component as Example 1. FIG.

  In the LC filter of the second embodiment, the dielectric substrate is mounted on the mounting substrate, similarly to the LC filter 10 of the first embodiment, but the configuration of the dielectric substrate 20a is different from that of the first embodiment.

  FIG. 4 is a plan view of the dielectric substrate 20a of the LC filter according to the second embodiment. FIG. 5 is a perspective view of the dielectric substrate 20a of the LC filter according to the second embodiment.

  As shown in FIGS. 4 and 5, the dielectric substrate 20a of the LC filter according to the second embodiment has an electrode pattern 23 and a pad electrode 25 formed on the upper surface 22s of the substrate body 22 in the same manner as the first embodiment. The pattern 23 and the pad electrode 25 are connected by a first bonding wire 26.

  Unlike the first embodiment, the electrode pattern 23 is disposed at a position rotated by 180 °, and a capacitor is disposed under the first bonding wire 26. That is, as shown in FIG. 4, the first bonding wire 26 is included in the electrode pattern 23 when viewed from the direction in which the counter electrode of the capacitor and the dielectric layer overlap (normal direction of the upper surface 22 s of the substrate body 22). It arrange | positions so that it may overlap with counter electrode 23a-23c (namely, capacitor | condenser).

  When the capacitor is arranged under the inductor formed by the first bonding wire 26 as described above, the inductor formed by the first bonding wire 26 and the capacitor are arranged so as not to overlap as in the first embodiment. Compared to the above, the dielectric substrate 20a can be made small, and thus the LC filter can be miniaturized.

  Example 3 An LC filter of Example 3 will be described with reference to FIG. The third embodiment is different from the first embodiment in the configuration of the dielectric substrate 20b.

  As shown in the perspective view of FIG. 6, the dielectric substrate 20 b has the resin 29 disposed on the upper surface 22 s of the substrate body 22, and the first bonding wire 26 is covered with the resin 29.

  On the lower surface 22t of the substrate body, an LGA (Land grid array) terminal 28 in which planar electrode pads are arranged in a grid is formed. The electrode pattern 23 and the pad electrode 25 on the upper surface 22 s of the substrate body 22 and the LGA terminal 28 on the lower surface 22 t of the substrate body 22 are connected by a via-hole conductor 27 that penetrates the dielectric layer of the substrate body 22.

  Since the first bonding wire 26 that forms the inductor of the resonator is fixed by the resin 29 and protected from the external environment, the characteristics and quality of the LC filter can be stabilized.

  When the dielectric substrate 20b is mounted on the mounting substrate, if the dielectric substrate 20b and the mounting substrate are connected via the LGA terminal 28, the second bonding wire that connects the dielectric substrate 20b and the mounting substrate. Can be eliminated.

  Although not shown, a resin may be disposed on the mounting substrate. For example, after mounting the dielectric substrate on the mounting substrate, a resin is placed on the upper surface of the substrate body of the mounting substrate, and the first bonding wire of the dielectric substrate and the dielectric substrate and the mounting substrate are connected with this resin. You may comprise so that the 2nd bonding wire to be covered may be covered.

  <Example 4> The LC filter of Example 4 will be described with reference to FIG. The fourth embodiment is different from the first embodiment in the configuration of the dielectric substrate 20c.

  FIG. 7A is a perspective view of the dielectric substrate 20c. FIG.7 (b) is the side view seen along line BB of Fig.7 (a).

  As shown in FIGS. 7A and 7B, first bonding wires 26a to 26c for connecting the electrode pattern 23 formed on the upper surface 22s of the substrate body 22 of the dielectric substrate 20c and the pad electrodes 25a to 25c. Are different from each other in shape.

  That is, the first bonding wire 26a is relatively high on one end side (half on the electrode pattern 23 side) and relatively low on the other end side (half on the pad electrode 25a side). The second bonding wire 26b adjacent to the first bonding wire 26a is relatively low on one end side (half on the electrode pattern 23 side) and relatively high on the other end side (half on the pad electrode 25b side). The third bonding wire 26c adjacent to the second bonding wire 26b is relatively high on one end side (half on the electrode pattern 23 side) and relatively low on the other end side (half on the pad electrode 25c side).

  For example, when wire bonding is performed using a wedge bonder, the wire on one end side to be fixed first is relatively high, and the other end side to be fixed later is relatively low, so as shown in FIG. In the adjacent first bonding wires 26a to 26c, the heights can be alternately switched.

  Since the bonding wire uses a thin metal wire, it may be inclined even if the positional accuracy is sufficient. Moreover, when embedding in resin like Example 3, it may deform | transform. When the shape of the bonding wire changes, the magnetic coupling coefficient between adjacent bonding wires changes and the characteristics as a filter change. Therefore, the magnetic coupling between the bonding wires is preferably reduced.

  By making the shapes of the adjacent first bonding wires 26a to 26c different from each other, the magnetic coupling between the adjacent first bonding wires 26a and 26b and between the adjacent first bonding wires 26b and 26c can be reduced. Even if the shapes of 26a to 26c are deformed, the influence on the filter characteristics can be reduced.

  Example 5 An LC filter of Example 5 will be described with reference to FIG. The fifth embodiment is different from the first embodiment in the configuration of the dielectric substrate 20d.

  FIG. 8A is a plan view of the dielectric substrate 20d according to the fifth embodiment. FIG.8 (b) is the side view seen along line BB of Fig.8 (a).

  As shown in FIG. 8A, in the dielectric substrate 20d of Example 5, the electrode pattern 23 and the three pad electrodes 25p to 25r are formed on the upper surface 22s of the substrate body 22, The pad electrodes 25p to 25r are connected by first bonding wires 26p to 26r, respectively. The interval between the pad electrodes 25p to 25r is larger than that in the first embodiment. Therefore, as shown to Fig.8 (a), as for the 1st bonding wires 26p-26r, the space | interval of the ends of the same side connected to the pad electrodes 25p-25r is the other side connected to the electrode pattern 23. It is larger than the distance between the other ends.

  As shown in FIGS. 8A and 8B, the first bonding wires 26p to 26r are relatively high on one end side connected to the pad electrodes 25a to 25c, and have the other end side connected to the electrode pattern 23 on the other end side. Relatively low. For example, when wire bonding is performed using a wedge bonder, one end side (pad electrodes 25a to 25c) to be fixed first is relatively high, and the other end side (electrode pattern 23 side) is relatively low. .

  When the first bonding wires having different heights on the one end side and the other end side are arranged adjacent to each other with the height direction aligned, between the adjacent first bonding wires, the relatively high one end side is Magnetic coupling is stronger than the relatively low end. In addition, if the intermediate portions of the adjacent first bonding wires are inclined with respect to each other, the magnetic coupling can be weakened more than when they are parallel to each other.

  As shown in FIGS. 8A and 8B, the adjacent first bonding wires 26a and 26b, 26b and 26c have one end side (half of the pad electrodes 25a to 25c side) on the other end side (electrode pattern 23). The higher one end side is relatively far away, and the lower other end side is relatively closer. The intermediate portions of the adjacent first bonding wires 26a and 26b and 26b and 26c are not parallel to each other but have an inclination, as shown in FIG. Therefore, since the magnetic coupling between the first bonding wires 26a to 26c can be made as small as possible, the influence on the filter characteristics can be reduced even if the shape of the first bonding wires 26a to 26c is deformed.

  In the adjacent first bonding wires 26p to 26r, a capacitor is formed when the interval between the other ends connected to the electrode pattern 23 is smaller than the interval between the one ends connected to the pad electrodes 25p to 25r. The area on the electrode pattern 23 side can be widened.

  Example 6 An LC filter of Example 6 will be described with reference to FIG. Example 6 differs from Example 1 in the configuration of the dielectric substrate 20e.

  FIG. 9A is a plan view of the dielectric substrate 20e. FIG.9 (b) is the side view seen along line BB of Fig.9 (a).

  As shown in FIG. 9A, the dielectric substrate 20e has an electrode pattern 23 and one pad electrode 25x formed on the upper surface 22s of the substrate body 22, and the electrode pattern 23 and the pad electrode 25x are 1 bonding wires 26x to 26z.

  As shown to Fig.9 (a), as for the 1st bonding wires 26x-26z, the space | interval of the one end of the same side connected to the electrode pattern 23 is the other end of the other side connected to the pad electrode 25x. Greater than the interval.

  As shown in FIGS. 9A and 9B, the first bonding wires 26x to 26z are relatively high on one end side connected to the electrode pattern 23 and relatively on the other end side connected to the pad electrode 25x. Very low.

  The adjacent first bonding wires 26x and 26y, and 26y and 26z are higher at one end side (half on the electrode pattern 23 side) than the other end side (half on the pad electrode 25x side) and relatively higher at one end side and lower. The other end side is relatively close. Thereby, since the magnetic coupling between the first bonding wires 25x to 25z can be made as small as possible, the influence on the filter characteristics can be reduced even if the shape of the first bonding wires 25x to 25z is deformed.

  When the first bonding wires 25x to 25z are connected to the common pad electrode 25x, one end of the inductor formed by the first bonding wires 25x to 25z is connected to the common GND, so that the high frequency characteristics are improved.

  <Summary> As described above, the inductor of the resonance circuit is formed by using the first bonding wire, the second bonding wire for connecting the dielectric substrate and the mounting substrate, and the first bonding for the inductor. By configuring the wire so as to form an angle of approximately 90 °, an LC filter having desired characteristics as designed can be easily obtained even if the wire is downsized.

  The present invention is not limited to the above embodiment, and can be implemented with various modifications.

DESCRIPTION OF SYMBOLS 10 LC filter 12 Mounting board 13 Substrate body 14a, 14b Terminal electrode 16a, 16b Second bonding wire 16k Second virtual surface 20, 20a-20e Dielectric substrate 22 Substrate body 23x Electrode pattern 23a-23c Counter electrode 24a, 24b Connection electrode 25, 25a to 25b, 25p to 25r, 25x to 25z Pad electrode 26, 26a to 26c, 26p to 26r, 26x to 26z First bonding wire 26k First virtual surface 27 Via hole conductor 28 LGA terminal 29 Resin

Claims (4)

A dielectric substrate having a dielectric layer and a counter electrode disposed so as to face each other through the dielectric layer, wherein a capacitor is formed by the dielectric layer between the counter electrode and the counter electrode;
A mounting substrate on which the dielectric substrate is mounted;
With
An inductor is formed by the first bonding wire on the dielectric substrate, and a resonator is configured by the inductor and the capacitor.
The dielectric substrate and the mounting substrate are connected by a second bonding wire,
The first and the second virtual surface which the first virtual plane bonding including a wire and comprising a second bonding wire, to substantially name a right angle,
The LC filter, wherein the first bonding wire is disposed so as to overlap the capacitor when viewed from a direction in which the counter electrode and the dielectric layer forming the capacitor overlap . The LC filter according to claim 1, wherein the first bonding wire is covered with a resin. The adjacent first bonding wire is characterized in that shapes are different from each other, LC filter according to claim 1 or 2. The adjacent first bonding wires are
The distance between the ends on the same side is greater than the distance between the other ends on the other side; and
Wherein one end side is relatively high, the other end is characterized in that relatively low, LC filter according to any one of claims 1 to 3.

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