Inductive Filter Elements

Abstract

The present invention relates to an inductive filter element having a wide bandwidth. An inductive filter element (100) is specified, comprising a core part (1) having a first end region (11), a central region (10), and a second end region (12) arranged along a longitudinal direction (91), the central region being arranged between the first end region and the second end region, and a conductive wire (2) having a winding (20) formed as a winding circuit in the central region of the core part, where the central region has a length lc in the longitudinal direction and a rectangular cross section perpendicular to the longitudinal direction, the rectangular cross section including a width wc in the lateral direction (92) and a height hc in the vertical direction (93), where lc>wc and lc>hc.

Description

[Technical field]

[0001] An embodiment of the present invention relates to an inductive filter element. In at least one embodiment, the inductive filter element can be a choke coil, preferably a wideband choke coil. For example, the inductive filter element can be implemented in a high-speed communication device. The inductive filter element can be used in industrial applications, particularly in the automotive or medical fields. [Background technology]

[0002] Modern communication systems increasingly rely on high-speed data transmission while being lightweight and compact. Such structures often require magnetic filters with high impedance over a wide frequency range. It is often required to provide power to another device and transmit data using the same transmission line, which is achieved with a so-called bias-tee configuration. Such systems, which allow the transmission of power over a data transmission line or signal channel, are also known as asymmetric or unbalanced injection systems and usually require small, wideband high-frequency filters.

[0003] For example, using an unbalanced power injection system, a Power over Coax (PoC) system can communicate between two devices and provide power at the same time. A series of inductors can form a multi-stage filter to achieve the required AC blocking level. Using different impedance performances of several different inductors is a common method to achieve the required bandwidth. Depending on the required bandwidth, inductors with high inductance values ​​of about 100-150 μH can be used to fix the low frequency impedance and inductors of several hundred nH can be used to fix the high frequency performance.

[0004] Thus, multi-stage filters are typically used, consisting of filter networks with two, three, four or more inductor stages, depending on the required bandwidth. Each inductor must be capable of delivering sufficient current so that the power injection system can operate at the power levels required, be capable of operating at high temperatures, and operate with as low a resistance as possible to avoid excessive power losses in the filter network. In addition to having to meet these requirements, such filter networks require a lot of area on the printed circuit board, depending on the size of the various inductors.

[0005] For example, prior art documents US Pat. Nos. 5,293,333, 5,393,605, 5,496,213, 5,597,103, and 5,641,633 describe multi-stage filter networks.

[0006] The impedance peak position of the inductors used in multi-stage filters depends on the inductance value and the internal stray capacitance. However, the material, manufacturing orientation, and winding method of the coil, as well as the enamel of the conductive wire, can change the internal stray capacitance of the implemented inductor. This stray capacitance variation creates problems with the standardization of specific filters of the required bandwidth, since two similar inductors with the same inductance value can have different self-resonant frequencies (SRFs) and different impedance curves. This problem is even more serious at high frequencies, where the effect of stray capacitance on the inductance value is greater.

[0007] The existing state of the art offers several solutions to create the desired filter for high frequencies in a power-over-signal configuration. In the first available solution, a topology is presented that uses a bias-tee configuration with multiple inductors to obtain the desired bandwidth. As mentioned before, this solution is used in unbalanced power injection systems such as PoC systems. However, it is difficult to use this solution in balanced transmission lines, since the two-inductor network implemented with multiple stages installed per transmission line has an asymmetric performance. Here, the change in inductance value due to manufacturing tolerances creates problems with mode conversion and return losses at high frequencies. However, when the tolerances are small, it is still possible to use such a solution intended for asymmetric use in the symmetric case, which is also called power-over-data-line (PoDL). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] DE 10 2019 126 816 A1 [Patent Document 2] DE 10 2008 044 845 A1 [Patent Document 3] JP 2010-232988 A [Patent Document 4] U.S. Pat. No. 10,701,693 [Patent Document 5] US Patent Application Publication No. 2018 / 0098324 Summary of the Invention [Problem to be solved by the invention]

[0009] It is at least one object of at least one embodiment to provide an inductive filter element, preferably an inductive filter element having a wide bandwidth. [Means for solving the problem]

[0010] This object is achieved by the subject matter of the independent claims. Further embodiments and configurations are the subject matter of the dependent claims.

[0011] In at least one embodiment, the inductive filter element comprises a core piece having a first end region, a central region, and a second end region disposed along a longitudinal direction, the central region being disposed between the first end region and the second end region.

[0012] In a further embodiment, the inductive filter element comprises a conductive line. The conductive line is formed as a winding in a central region of the core part and may include a portion, hereinafter referred to as a winding portion. The winding portion forms the actual only coil structure of the inductive filter element. In other words, the inductive filter element preferably comprises only one conductive line having only one winding portion, so that the inductive filter element comprises only one coil structure.

[0013] In a further embodiment, the central region of the core part has a length lc in the longitudinal direction. Preferably, lc is 1 mm or more, or 5 mm or more and 15 mm or less. Furthermore, the core part has a rectangular cross section perpendicular to the longitudinal direction. The cross section is rectangular and has a transverse width wc and a vertical height hc, each of the transverse and vertical directions being preferably perpendicular to the longitudinal direction and the transverse direction being perpendicular to the vertical direction. Furthermore, lc>wc and lc>hc, i.e. the length of the core part is greater than both the width and the height. Preferably, lc / hc≧2, and lc / wc≧2, or even lc / wc≧3. Particularly preferably, 3≦lc / wc≦15 or 5≦lc / wc≦15 or 10≦lc / wc≦15, and 2≦lc / hc≦20 or 5≦lc / hc≦20 or 10≦lc / hc≦20 or 15≦lc / hc≦20.

[0014] Moreover, the cross section being rectangular means in particular that the cross section at any position in the central region of the core part is rectangular, which also means that the cross section is square with wc=hc, preferably 1≦wc / hc≦5, or 2≦wc / hc≦5, or 3≦wc / hc≦5.

[0015] In a further embodiment, the winding is formed as a single layer winding in the central region, i.e., the winding has no conductor wires located on top of other conductor wires in either the top-bottom or left-right direction. Preferably, the number of turns is substantially given by the length lc of the central region divided by the conductor wire diameter, so that the conductor wires are tightly wound. A single layer winding allows for reduced stray capacitance compared to coils with multiple winding layers wound around each other.

[0016] In a further embodiment, the windings of the conductor are formed as a number of winding blocks arranged sequentially in the longitudinal direction and connected in series at the transitions of the conductor. Each winding block can be formed from at least a single layer of windings wound in only one layer, or from a winding having five or less winding layers. Preferably, the length lwb of each winding block in the longitudinal direction is short compared to the length lc of the central region. For example, lwb / lc≦0.5, or lwb / lc≦0.2, or lwb / lc≦0.1. The short length of the winding block compared to the length of the central region and the small number of winding layers allow the formation of a low-capacity coil in each of the winding blocks, so that the sum of all the winding blocks is a low-capacity coil structure. With multiple winding layers per winding block, higher inductance values ​​can be obtained. Preferably, the inductive filter element includes more than two and not more than ten winding blocks. Each transition can have a length lt along the longitudinal direction 91, and the length lt of the transition is preferably long enough so that the winding blocks are sufficiently separated from each other. It is preferable that lt is 0.1 mm or more, or 0.2 mm or more, or 0.5 mm or more, and it is preferable that lt is 0.8 mm or less. It is also preferable that lt / lwb≧10 is satisfied, and it is more preferable that 20≦lc / lt≦150 is satisfied.

[0017] In a further embodiment, the central region has a first cross section adjacent to the first end region and a second cross section adjacent to the second end region. The first and second cross sections can be equal. In other words, the first cross section can have a first area cs1 and the second cross section can have a second area cs2, where cs1 / cs2=1. In particular, any cross section of the central region can be equal to the first and second cross sections and the central region can be rectangular shaped. Alternatively, the first cross section can be larger than the second cross section and the central region of the core part can be pyramidal shaped. This means that at least one of the height hc and width wc decreases as one moves away from the first end region along the longitudinal direction. For example, at least one of the height hc and width wc decreases linearly as one moves away from the first end region. In particular, the first cross section has a first area cs1 and the second cross section has a second area cs2, and the first cross section has a second area cs2. <cs1 / cs2≦15、または2≦cs1 / cs2≦15、または5≦cs1 / cs2≦15、またはさらには10≦cs1 / cs2≦15である。

[0018] The first and second end regions preferably have similar shapes and similar dimensions, regardless of the shape of the central region. In particular, the width of the first end region in the lateral direction can be equal to the width of the second end region in the lateral direction, and the height of the first end region in the vertical direction can be equal to the height of the second end region in the vertical direction.

[0019] In a further embodiment, the inductive filter element comprises a housing made of a plastic material that houses the entire core part and the conductive lines. The housing can be formed by a molding that contains or is made of a plastic material such as an epoxy resin. It is particularly preferred that the housing can be made of a high-temperature stable plastic material, such as a material based on or consisting of liquid crystal polymer (LCP) and / or polyphenylene sulfide (PPS). The housing can be made of only one or more plastic materials without a filler material. Furthermore, the housing can contain at least one filler material dispersed in the plastic material. It is particularly preferred that the housing includes a magnetic material, such as magnetic particles or flakes, dispersed in the plastic material as a filler material. The magnetic material can include or be, for example, ferrite or metal powder.

[0020] In a preferred embodiment, the inductive filter element combines the idea of ​​a rectangular magnetic core part with a conductive line organized in only one layer of windings or in several spatially separated winding blocks. To close the magnetic circuit, the magnetic core part is preferably housed in a housing formed by a molding containing magnetic fillers that ensure good shielding and high current withstand performance. The inductive filter element can be used and implemented in particular in asymmetric current injection systems, since the described features reduce stray capacitance and provide a high self-resonant frequency. The housing is preferably made of plastic and can contain magnetic fillers to provide a magnetic shield and improve electrical parameters such as low direct current resistance (RDC), high inductance values ​​and good high frequency performance due to the low losses offered by the material used. In particular, the good performance regarding scattering parameters such as low reflection loss and low insertion loss makes it suitable for applications such as PoC (Power over Coaxial) or LVDS (Low Voltage Differential Signaling).

[0021] The inductive filter elements described herein can form broadband choke coils for high speed communication devices and can offer several improvements over current state of the art inductive filters. Ultra-wide (broadband) frequency response that covers frequency ranges normally covered by combinations of two or three inductors by forming an inductive filter element compatible with PoC or LVDS. Good magnetic shielding by encasing the magnetic core using a housing that contains or is constructed from a plastic material in combination with a magnetic material. The windings form a coil structure with low stray capacitance for good high frequency performance. High permeability achieved by magnetic materials with low RDC and simultaneously high saturation current.

[0022] In a further preferred embodiment, the inductive filter element comprises a magnetic core part having a pyramidal shape. The coil structure formed by the windings of the pyramidal core part provides further low return and insertion losses, as well as high inductance, and provides improved electrical characteristics with low stray capacitance enabling a high self-resonant frequency.

[0023] Furthermore, the inductive filter elements described herein can be used and implemented in symmetric current injection systems, as they can improve the performance achieved by conventional inductors used in PoDL (Power over Dataline) or similar systems. In particular, in such systems, the use of filters with multiple filter stages can be difficult due to differences in symmetric transmission lines. This effect of introducing mode conversion in the scattering parameters (Scd11, Scd12, Scd21, Scd22, Sdc11, Sdc12, Sdc21, Sdc22) can be reduced by using the inductive filter elements described herein in combination with the further improvements mentioned above.

[0024] Further features, advantages and preferences will become apparent from the following description of exemplary embodiments taken in conjunction with the drawings. [Brief description of the drawings]

[0025] [Figure 1A] FIG. 1A shows a schematic diagram of an inductive filter element in one embodiment. [Figure 1B] FIG. 1B shows a schematic diagram of an inductive filter element of one embodiment. [Figure 1C] FIG. 1C shows a schematic diagram of an inductive filter element in one embodiment. [Figure 1D] FIG. 1D shows a schematic diagram of an inductive filter element in one embodiment. [Figure 1E] FIG. 1E shows a schematic diagram of an inductive filter element of one embodiment. [Diagram 2] FIG. 2 shows a schematic diagram of a further embodiment of an inductive filter element. [Figure 3A] FIG. 3A shows a schematic diagram of a further embodiment of an inductive filter element. [Figure 3B] FIG. 3B shows a schematic diagram of a further embodiment of an inductive filter element. [Figure 4A] FIG. 4A shows a schematic diagram of the core components of the inductive filter element of various further embodiments. [Figure 4B] FIG. 4B shows a schematic diagram of the core components of the inductive filter element of various further embodiments. [Figure 4C] FIG. 4C shows a schematic diagram of the core components of the inductive filter element of various further embodiments. [Diagram 5] FIG. 5 shows a schematic diagram of a circuit diagram of an AC blocking inductive filter in an exemplary PoC structure used in the art and further embodiments. [Figure 6] FIG. 6 shows a schematic diagram of a circuit diagram of an AC blocking inductive filter in an exemplary PoC structure used in the art and further embodiments. [Figure 7] FIG. 7 shows a schematic diagram of a circuit diagram of an AC blocking inductive filter in an exemplary PoC structure used in the art and further embodiments. [Figure 8A] FIG. 8A shows impedance curves of a typical inductor used in a multi-stage filter structure and an inductive filter element according to a further embodiment. [Figure 8B] FIG. 8B shows the impedance curve of a typical inductor used in a multi-stage filter structure and an impedance curve of an inductive filter element according to a further embodiment. [Figure 8C] FIG. 8C shows the impedance curve of a typical inductor used in a multi-stage filter structure and an impedance curve of an inductive filter element according to a further embodiment. [Figure 8D] FIG. 8D shows the impedance curve of a typical inductor used in a multi-stage filter structure and an impedance curve of an inductive filter element according to a further embodiment. [Figure 8E] FIG. 8E shows impedance curves of a typical inductor used in a multi-stage filter structure and an inductive filter element according to a further embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Elements of the same design and / or function are identified by the same reference numerals in the drawings. It should be understood that the illustrated embodiments are illustrative representations and are not necessarily drawn to scale.

[0027] 1A-1E show in various views an inductive filter element 100 according to one embodiment and some of its constituent parts. The inductive filter element 100 includes a core part 1, a conductive wire 2 that forms a coil structure on the core part 1, an electrical contact part 3, and a housing 4.

[0028] FIG. 1A is a perspective view of a core part 1 of an inductive filter element 100. FIG. 1B is a perspective view of the internal structure of the inductive filter element 100. FIG. 1C is a perspective view of the external appearance of the inductive filter element 100. FIG. 1D is a diagram of the core part 1 with dimensions of each part indicated. FIG. 1E is a diagram showing the inductive filter element 100 at an intermediate stage during manufacture. The following description applies equally to FIGS. 1A to 1E.

[0029] The core part 1, which may for example be made from ferrite and formed as a single part, comprises a central region 10 between a first end region 11 and a second end region 12. The first end region 11 and the second end region 12 are preferably directly adjacent to the central region 10. Here and in the following, the main extension direction of the core part 1, from the first end region 11 to the second end region 12, is indicated as a longitudinal direction 91 as shown in the figure. Thus, the first end region 11, the central region 10 and the second end region 12 are arranged successively along the longitudinal direction 91.

[0030] Further, a lateral direction 92 and a vertical direction 93 are shown in the figure. For example, when mounted on a mounting surface of a carrier such as a printed circuit board, the horizontal plane defined by the longitudinal direction 91 and the lateral direction 92 is typically arranged parallel to the mounting surface of the carrier, and the vertical direction 93 is arranged perpendicular to the mounting surface. The dimension along the longitudinal direction 91 is indicated as a length, the dimension along the lateral direction 92 is indicated as a width, and the dimension along the vertical direction 93 is indicated as a height. Thus, each of the inductive filter element 100 and the core component 1 has a length in the longitudinal direction 91, a width in the lateral direction 92, and a height in the vertical direction 93, respectively.

[0031] The central region 10 of the core part 1 is bounded in a lateral direction 92 by two side surfaces 101 arranged opposite each other, the distance between the side surfaces 101 defining the width of the central region 10. Furthermore, the central region of the core part 1 is bounded in a vertical direction 93 by a top surface 102 and a bottom surface 102' arranged opposite each other, the distance between the top surface 102 and the bottom surface 102' defining the height of the central region 10.

[0032] Similarly, the first end region 11 is bounded in a lateral direction 92 by two oppositely disposed side surfaces 111, the distance between the side surfaces 111 defining the width of the first end region 11. The second end region 12 is bounded in a lateral direction 92 by two oppositely disposed side surfaces 121, the distance between the side surfaces 121 defining the width of the second end region 12.

[0033] Furthermore, the first end region 11 is bounded in the vertical direction 93 by a top surface 112 and a bottom surface 112' disposed opposite each other, the distance between the top surface 112 and the bottom surface 112' defining a height of the first end region 11. The second end region 12 is bounded in the vertical direction 93 by a top surface 122 and a bottom surface 122' disposed opposite each other, the distance between the top surface 122 and the bottom surface 122' defining a height of the second end region 12.

[0034] As can be seen from Figures 1A and 1D, in the illustrated embodiment, the heights of the central region 10 and the first and second end regions 11 and 12 are equal to each other and are shown as heights hc and h, respectively. The top faces 102, 112 and 122 form a flat top surface of the core part 1, and the bottom faces 102', 112' and 122' form a flat bottom surface of the core part 1. The width wc of the central region 10 is smaller than the width w of the first and second end regions 11 and 12, and the widths of the first and second end regions 11 and 12 are equal to each other, so that the core part 1 has a bone-like shape. As a result, the central region 10 perpendicular to the longitudinal direction 91 has a cross section consisting of a height hc and a width wc, which can be equal, so that the central region 10 can have a square cross section. Alternatively, the central region 10 may have a rectangular cross section, since the height hc and width wc may satisfy hc / wc>1 or hc / wc<1. Preferably, 1≦wc / hc≦5. Furthermore, wc / hc has a value that can be specified in a general purpose portion.

[0035] Adjacent to the first end region 11, the central region 10 has a first cross-section 110, and adjacent to the second end region 12, the central region 10 has a second cross-section 120. In the illustrated embodiment, the first cross-section 110 and the second cross-section 120 are equal to each other.

[0036] In the longitudinal direction 91, the central region 10 has a length lc defined by the distance between the first cross section 110 and the second cross section 120. Furthermore, the first end region 11 has a first end face 113 and the second end region 12 has a second end face 123. The first end face 113 and the second end face 123 define the boundaries of the core part 1 in the longitudinal direction 91. The distance between the first end face 113 and the second end face 123 thus defines the length l of the core part 1. Preferably, 1.1≦lc / l≦1.5 is satisfied.

[0037] As can be seen from FIG. 1B, the conductive wire 2 has turns 20 wound around the central region 10 to form a square or rectangular coil structure with a single layer of windings, depending on the cross section of the central region 10. That is, the turns 20 are not arranged on top of one another, either vertically or laterally. In particular, the central region 10 is defined as the part of the core part 1 in which the turns 20 of the conductive wire 2 are arranged, i.e. the coil windings are arranged. The actual coil structure formed by the turns 20 thus starts at the first cross section 110 and ends at the second cross section 120. The conductive wire 2 can contain or consist of one or more metals, for example selected from copper, nickel and chromium, can be coated with an electrically insulating material made of a polymer, a lacquer or an enamel, and can have a diameter of 20 μm to 1 mm.

[0038] Preferably, at least the edges 119 of the central region 10 between the side surfaces 101 and the top and bottom surfaces 102, 102' may be chamfered or rounded to facilitate tight winding of the conductive wires 2 around the central region 10. Thus, the terms "rectangular" and "square" used throughout this description may include shapes with rounded or chamfered corners. Additionally, more or all edges of the core part 1 may be chamfered or rounded.

[0039] The inductive filter element 100 has electrical contact elements 3 arranged in the first end region 11 and the second end region 12, respectively, and electrically connects the coil structure formed by the windings 20 of the conductive line 2. The electrical contact elements 3 are formed from lead frame pieces 300, as shown in FIG. 1E. Each of the electrical contact elements 3 includes an external contact region 31, a tongue region 33 arranged between support regions 32, and a conductive line connection region 34 that serves as a joining point for the conductive line 2. The tongue region 33 extends vertically, and the support region 32 extends longitudinally. The external contact region 31 is bent to reach the underside of the inductive filter element 100, so that the inductive filter element 100 can be soldered to a mounting surface of a carrier, such as a printed circuit board, for example by surface mount technology (SMT). The core component 1 is placed on the support area 32 of the external contact component 3, the tongue area 33 of the external contact component 3 being guided vertically along the first end face 113 and the second end face 123 of the core component 1, respectively. To fix each of the electrical contact components 3 to the core 1, it is possible to use an adhesive that is applied between the support area 32 of each of the electrical contact components 3 and the core component 1 and / or between the tongue area 33 of each of the electrical contact components 3 and the core component 1. As can be seen from Figs. 1A and 1B, the first end region 11 and the second end region 12 preferably have a groove 114 and a groove 124, respectively, in which the tongue area 33 can be placed. The groove 114 and the groove 124 can thus be provided for easy attachment of the external contact component 3 to the core component 1. As can be seen from Fig. 1E, the leadframe strip 300 with the tongue area 33 already bent in the vertical direction 93 is attached and fixed to the core component 1. After connecting the conductive wire 2 to the conductive wire connection area 34 of the lead frame piece 300, the housing 4 described below can be applied, the lead frame piece 300 can be cut at the dashed lines shown, and the external contact area 31 can be bent as described above to reach the underside of the housing 4.

[0040] The conductive wire 2 further includes a transition portion 21 and a connection portion 22, with each end of the winding portion 20 having a transition portion 21 disposed between either the winding portion 20 or the connection portion 22. The transition portion 21 extends across the top surface 112 of the first end region 11 and the top surface 122 of the second end region 12 to the conductive wire connection region 34 of the electrical contact element 3. Each of the connection portions 22 is connected to the conductive wire connection region 34 by welding or soldering, e.g., laser welding, selective soldering, or iron soldering, to provide a reliable connection between the conductive wire 2 and the electrical contact element 3.

[0041] All components of the inductive filter element 100, except for the external contact area 31 of the electrical contact part 3, are housed in a housing 4, which may be formed by a molding method such as injection molding, compression molding, or transfer molding. The housing 4 is therefore preferably formable by a molding containing or made of a plastic material such as an epoxy resin. More preferably, the housing 4 is made of a high-temperature stable plastic material such as LCP or PPS.

[0042] Furthermore, magnetic materials such as ferrite particles or flakes can be dispersed in the plastic material of the housing 4. The ratio of the amount of magnetic material to the amount of plastic material in the housing 4 is preferably 40% by mass or more and 95% by mass or less. The magnetic material can form a magnetic filler that provides magnetic shielding, and can improve electrical parameters such as lower direct current resistance (RDC), higher inductance value, and better high frequency performance.

[0043] As previously mentioned, the dimensions of the coil structure formed by the windings 20 are defined by the length lc, width wc, and height hc of the central region. The windings 20 forming the actual coil structure of the inductive filter element 100 are rectangular or square coils with lc>wc and lc>hc. Preferably, 3≦lc / wc≦15, 2≦lc / hc≦20. Furthermore, each of lc / wc and lc / hc can be specified in a general purpose part. As will be described below with respect to Figures 8A-8E, such coil dimensions associated with a single layer winding provide low stray capacitance with high inductance values ​​and high bandwidth.

[0044] The following figures show variants and further developments of the inductive filter element 100. The following description is therefore limited substantially to the differences from the previous embodiment.

[0045] The inductive filter element 100 shown in Fig. 2 has a winding 20 of the conductive line 2 including a plurality of winding blocks 23 arranged spatially spaced apart from one another in the central region 10 of the core part 1. Between the plurality of winding blocks 23, the winding 20 of the conductive line 2 is provided with transitions 24 formed of a single conductive wire and preferably extends only on a single surface of the core part 1, for example the top surface 102 as shown, or alternatively the bottom surface or one of the side surfaces. Thus, the winding 20 of the conductive line 2 is formed from a plurality of coil structures formed by the winding blocks 23 connected in series only by the transitions 24 of the single-wire conductive line 2.

[0046] The winding section 20 is preferably made up of at least two winding blocks 23, and can be made up of up to ten winding blocks 23. As shown in FIG. 2, the winding section 20 can be made up of, for example, five winding blocks 23.

[0047] Each winding block 23 can be implemented as a single layer of winding or can include multiple winding layers. For example, as shown in FIG. 2, each winding block 23 can include three winding layers. Each winding block 23 is preferably formed of at least a single layer of winding wound in only one layer, or five or less winding layers. The length lwb of each winding block 23 in the longitudinal direction 91 is preferably short compared to the length lc of the central region 10. For example, lwb / lc≦0.5, or lwb / lc≦0.2, or lwb / lc≦0.1. Since the multiple winding blocks 23 are short in length and have a small number of winding layers, each winding block 23 can be formed as a low-capacity coil, so that the sum of all the winding blocks 23 also has a low-capacity coil structure. With the multiple winding blocks 23, the inductive filter element 100 can achieve a higher inductance value. The inductive filter element 100 preferably includes a number of winding blocks 23 between 2 and 10. In FIG. 2, the inductive filter element 100 has, for example, five winding blocks 23 .

[0048] The length lt of the transition portion 24 in the longitudinal direction 91 is preferably long enough so that the winding blocks 23 are sufficiently spaced apart from one another. It is preferable that lt / lwb≧10 is satisfied, and it is more preferable that 20≦lc / lt≦150 is satisfied.

[0049] 3A and 3B show an embodiment of an inductive filter element 100 which, in contrast to the previous embodiment, has a pyramidal core part 1. This means that the cross section of the central region 10 decreases or increases moving away from the first end region 11 or the second end region 12. Thus, at least one of the width wc and height hc of the central region 10 decreases moving away from the first end region 11 or the second end region 12.

[0050] As shown in Figures 3A and 3B, for example, the width wc of the central region 10 can decrease linearly away from the first end region 11. Thus, the central region 10 has a first cross section 110 adjacent the first end region 11 and a second cross section 120 adjacent the second end region 12, the first cross section 110 being larger than the second cross section 120. The widths of the first end region 11 and the second end region 12 are preferably equal. The height hc of the central region 10 remains constant in this example. As the cross-sectional area of ​​the central region 10 decreases, the wound diameter of the turns 20 of the conductive wire 2 also decreases away from the first end region 11. The cone shape is applicable to both directions of the core, but is shown in one direction in Figures 3A and 3B.

[0051] Figures 4A-4C show further examples of pyramidal shapes of the core 1 that can be combined with the pyramidal shapes shown in Figures 3A and 3B and / or with each other. Figure 4A shows that the height hc of the central region 10 decreases linearly away from the first end region 11. Figures 4B and 4C show that the width wc and height hc decrease curvilinearly away from the first end region 11.

[0052] The width wc and / or height hc are preferably selected such that the ratio cs1 / cs2 of the area cs1 of the first cross section and the area cs2 of the second cross section decreases in the range of greater than 1 and less than or equal to 15. Furthermore, the value of cs1 / cs2 can be specified in a generic part.

[0053] The inductive filter element 100 of the above-described embodiment can be used in any application requiring an inductive filter element, particularly in applications requiring a wideband inductive filter element, such as asymmetric injection systems, such as PoC structures.

[0054] 5 shows a circuit diagram of a typical PoC structure as an example of a power injection application using the inductive filter element 100 of the above-mentioned embodiment. Furthermore, the inductive filter element 100 can also be used in other asymmetric or symmetric current injection systems.

[0055] The circuit shown in Fig. 5 comprises a serializer 212a and a deserializer 212b, forming a so-called "SerDes". The serializer 212a and the deserializer 212b are AC-coupled in the data transmission line via DC-blocking capacitors 213a, 213b, 213c, and 213d, and are connected via a coaxial cable 216 that provides power transmission 217b as well as data transmission 217a. Power is injected by a power sourcing equipment (PSE) 211a through an AC-blocking inductive filter 215a and is discharged to a power receiving device (PD) 211b by another AC-blocking inductive filter 215b. The capacitors 214a and 214b are implemented to remove AC noise caused by the transmission line as well as AC noise generated by either the PSE 211a or the PD 211b. DC blocking capacitors 213a, 213b, 213c, and 213d, together with AC blocking inductive filters 215a and 215b, on either side of coaxial cable 216a, form a so-called "bias tee."

[0056] Figure 6 shows a typical AC blocking inductive filter 215a used in the art as a PoC filter between nodes 151 and 152 of the circuit shown in Figure 5. AC blocking inductive filter 215b is similarly feasible.

[0057] 5, the RF path goes from serializer 212a through node 152 to deserializer 212b, which are separated by a DC blocking capacitor. On the RF side of serializer 212a, there is also a DC signal provided by PSE 211a that is separated from the RF path by AC blocking inductive filter 215a.

[0058] As shown in FIG. 6, the exemplary AC blocking inductive filter 215a is composed of three filter stages 150a, 150b, and 150c, each of which includes an inductor 156a, 156b, and 156c connected to a damping resistor 155a, 155b, and 155c. For example, in some applications, resistor 155a is often omitted. For example, filter stages 150b and 150c can be composed of additional resistors 157b and 157c, respectively, along with capacitors 158b and 158c, to form a T-filter. However, resistors 157b and 157c and capacitors 158b and 158c are optional and can be omitted depending on the application.

[0059] A typical PoC filter structure includes at least a first stage 150a and a second stage 150b, and may include three stages 150a, 150b, and 150c as shown in Figure 6, and may further include additional stages embodied as stage 150c, for a total of four or more stages.

[0060] Since each inductor in a modern filter structure has a certain bandwidth, the combination of multiple filter stages produces the required filter bandwidth and necessary AC rejection level. Therefore, modern filter structures that form wideband inductive filter solutions typically require a lot of area on a printed circuit board and are not cost-effective.

[0061] As shown in FIG. 7, the entirety of each state-of-the-art multi-stage filter structure forming an inductive filter in a circuit such as the circuit shown in FIG. 5 can be replaced by the inductive filter element 100 of the above embodiment, and thus by a single inductor element. Optionally, for example, a damping resistor can be added in parallel with the inductive filter element 100. As a result, instead of the two complex multi-stage filter structures forming the inductive filter 215a and the inductive filter 215b, the circuit of FIG. 5 can be constructed using only two inductive filter elements 100. Thus, the power injection system comprises a power input side at one side of a signal transmission line such as a data transmission line or a coaxial cable, and DC power is coupled to the signal transmission line through exactly one inductive filter element 100 as described herein. Furthermore, at the other side of the signal transmission line, which is the power output side, the DC power is coupled to the signal transmission line through exactly one further inductive filter element 100 as described herein. The power input side inductive filter element 100 and the power output side inductive filter element 100 can be implemented in a similar manner.

[0062] As described below, the inductive filter element 100 provides a solution with wide bandwidth and very high self-resonant frequency. Additionally, the inductive filter element 100 can provide good ability to withstand high DC currents, allowing for reduced area on a printed circuit board, thus reducing overall system cost.

[0063] 8A to 8E show impedance curves of a multi-stage filter structure using a general inductor and the impedance curve of the inductive filter element described above.

[0064] 8A shows impedance curves 50a and 50b of impedance I versus frequency f for a typical PoC filter circuit using two inductors. An inductor with a lower inductance value, shown in curve 50b, is used to tune the impedance for high frequency performance, while a second inductor with a higher inductance value, shown in curve 50a, is used to tune the low frequency performance.

[0065] Figure 8B shows impedance curves 50a, 50b, and 50c of a typical PoC filter circuit using three inductors. The first and second inductors shown in curves 50a and 50b are similar to the configuration in Figure 8A. The lowest frequency band inductor shown in curve 50c requires a very high inductance value, which significantly increases the cost and size of the filter structure.

[0066] For example, three inductor coils with inductances of 100 μH, 5.6 μH, and 220 nH, respectively, can be used to generate the desired impedance levels over the frequency range shown. The different self-resonant frequency (SRF) of each inductor results in an impedance peak. The SRF of an inductor is determined by the stray capacitance according to the formula SRF=1 / [2π×(LC)1 / 2], where L is the inductance value and C is the stray capacitance. Since the stray capacitance is highly dependent on the inter-winding capacitance, the best way to reduce the SRF is to reduce the inter-winding capacitance. In the inductive filter element 100 described above, low stray capacitance can be achieved at high inductance values ​​by a rectangular core component consisting of a winding section including a single layer of winding as described in connection with Figures 1A-1E, or a winding section including multiple well-separated winding blocks as described in connection with Figure 2. This is because both measures can significantly reduce the inter-winding capacitance. As discussed in connection with Figures 3A and 3B, a cone-shaped core piece having a larger cross-sectional area on one side of the core piece and a smaller cross-sectional area on the other side of the core piece helps to further reduce the capacitance between the windings due to the smaller connection area between the turns in the area of ​​smaller cross-sectional area, while at the same time providing better high frequency performance and eliminating resonant peaks.

[0067] In Figures 8C and 8D, the impedance curves 50a, 50b, and 50c shown in Figures 8A and 8B are compared with the impedance curve 110a of an inductive filter element according to the present invention, in particular the inductive filter element embodied as described in relation to Figures 1A-1E.

[0068] The improved behavior of the inductive filter element is clearly visible in both the high and low frequency ranges, improving performance while simultaneously reducing the area on the printed circuit board and design effort, as well as the costs associated with component procurement, etc. Substituting a three-stage filter structure further reduces the cost and size of the filter, providing an even greater improvement compared to substituting two inductors.

[0069] Figure 8E shows impedance curve 100a compared to impedance curve 100b of an inductive filter element having a pyramidal core component as described in connection with Figures 3A and 3B. It can be seen that the pyramidal design provides improved high frequency performance, thereby providing a wider bandwidth.

[0070] Instead of or in addition to the features described in connection with the drawings, the embodiments shown in the figures may include further features described in the general part of this specification. Moreover, the features and embodiments of the figures may be combined with each other, even in cases where the combination is not explicitly described.

[0071] The present invention is not limited in any way by the description based on the exemplary embodiments, but rather includes each and every novel feature and any combination of features, including any combination of features in the claims, even if that feature or combination itself is not explicitly recited in the claims or embodiments. [Explanation of symbols]

[0072] 1 Core components 2 Conductive wire 3 Electrical Contact Components 4. Housing 10 Central area 11 First end area 12 Second end area 20 Winding section 21 Transition 22 Connection 23 Winding block 24 Transition 31, 31a, 31b External contact area 32 Support area 33 Lingual area 34 Conductive Wire Connection Area 50a, 50b, 50c impedance curves 91 Longitudinal 92 Horizontal 93 Vertical 100 Inductive filter element 100a, 100b impedance curves 101, 111, 121 Side 102, 112, 122 top surface 102´, 112´, 122´ Bottom 110 1st cross section 113 First end surface 114, 124 groove 119 Edge 120 Second cross section 123 Second end face 151, 152 nodes 150a, 150b, 150c filter stages 155a, 155b, 155c resistors 156a, 156b, 156c Inductors 157b, 157c resistor 158b, 158c capacitors 211a Power Supply Equipment 211b Power receiving device 212a Serializer 212b Deserializer 213a, 213b, 213c, 213d capacitors 214a, 214b capacitors 215a, 215b Inductive filters 216 Coaxial Cable 217a Data transmission 217b Power transmission 300 Lead frame pieces

Claims

1. a core part (1) having a first end region (11), a central region (10) and a second end region (12) arranged along a longitudinal direction (91), said central region being arranged between said first end region and said second end region; a conductive wire (2) having a winding portion (20) formed as a winding line in the central region of the core part, The central region of the core piece includes a rectangular cross-section having a length lc in the longitudinal direction and perpendicular to the longitudinal direction, the cross-section having a width wc in a lateral direction (92) and a height hc in a vertical direction (93), where lc>wc and lc>hc.

2. 2. An inductive filter element according to claim 1, characterized in that 3≦lc / wc≦15 and 2≦lc / hc≦20.

3. 2. An inductive filter element according to claim 1, characterized in that 1≦hc / wc≦5.

4. The inductive filter element of claim 1 , wherein the windings are formed as a single layer winding in the central region.

5. 2. The inductive filter element according to claim 1, wherein the windings of the conductor wire are formed as a plurality of winding blocks (23) arranged one after the other in the longitudinal direction and connected in series by transitions (21) of the conductor wire.

6. The inductive filter element of claim 5 , wherein each of the plurality of winding blocks comprises five or fewer winding layers.

7. 6. The inductive filter element of claim 5, wherein each of the plurality of winding blocks has a length along the longitudinal direction lwb, where 2≦lc / lwb≦10.

8. 6. The inductive filter element of claim 5, wherein each of the conductive line transitions between two adjacent winding blocks has a length lt along the longitudinal direction, where 20≦lc / lt≦150.

9. the central region having a first cross-section (110) adjacent the first end region and a second cross-section (120) adjacent the second end region; 2. The inductive filter element of claim 1, wherein the first cross section is larger than the second cross section and the central region of the core piece has a pyramidal shape.

10. 10. An inductive filter element according to claim 9, wherein the first cross section (S1) has a first area (cs1) and the second cross section (S2) has a second area (cs2), where 1<cs1 / cs2≦15.

11. 10. The inductive filter element of claim 9, wherein at least one of the height hc and the width wc decreases moving along the longitudinal direction away from the first end region.

12. 12. An inductive filter element according to claim 11, wherein the height hc and / or the width wc decrease linearly away from the first end region.

13. 2. An inductive filter element as claimed in claim 1, wherein a lateral width of the first end region is equal to a lateral width of the second end region and a vertical height of the first end region is equal to a vertical height of the second end region.

14. 14. An inductive filter element according to any one of the preceding claims, further comprising a housing (4) containing a plastic material that accommodates the entire core part and the conductive lines.

15. 15. The inductive filter element of claim 14, wherein the housing includes magnetic particles dispersed within the plastic material.

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