COMMON MODE CHOKE AND METHOD OF OPERATION

Abstract

A common mode choke with extended frequency range and improved reflection in mode conversion is specified. In this case, the common mode choke has a coil with three turns, where a coupling between a first turn and a second turn is different from a coupling between the second turn and an n-th turn, and so on.

Claims

1. A common mode choke, comprising a first coil with a winding from a first, a second to an n-th turn, wherein a coupling between the first turn and the second turn is different from a coupling between the second turn and the n-th turn, and wherein n is a number ≥2.

2. The common mode choke according to claim 1, comprising a second coil having a winding with a first, a second . . . and an n-th turn.

3. The common mode choke according to claim 1, wherein a coupling between the first turn and the second turn of the second coil is different from a coupling between the second turn and the n-th turn of the second coil.

4. The common mode choke according to claim 1, wherein the coupling is a magnetic and/or capacitive coupling.

5. The common mode choke according to claim 4, wherein the coupling is a capacitive coupling.

6. The common mode choke according to claim 1, wherein the first turn, the second turn and the n-th turn have different lengths.

7. The common mode choke according to claim 1, wherein the first coil comprises a magnetic core around which the winding of the first coil is wound.

8. The common mode choke according to claim 7, wherein the magnetic core of the first coil has a variable circumference along a longitudinal axis.

9. The common mode choke according to claim 8, wherein the magnetic core of the first coil has a linearly increasing circumference along the longitudinal axis with increasing longitudinal position.

10. The common mode choke according to claim 1, wherein the magnetic core of the first coil and/or the winding of the first coil is conical or trapezoidal in shape.

11. The common mode choke according to claim 1, comprising a second coil formed symmetrically or anti-symmetrically with respect to the first coil.

12. The common mode choke according to claim 1, wherein windings are made of a material selected from copper or an alloy with copper as main component, silver or an alloy with silver as main component.

13. The common mode choke according to claim 1, wherein coil cores consist of a material selected from a magnetic material, Ferrite, MnZn, NiZn, iron powder, an organic material enriched with a magnetic material, and a material comprising one of these materials as a major constituent.

14. The common mode choke according to claim 1, comprising four terminals for interconnection with an external circuit environment, wherein the common mode choke is configured as an SMD component.

15. A method of operating a common mode choke, using a common mode choke according to claim 1.

16. A method of operating a common mode choke in which differential coupling between a first turn and a second turn relative to the second turn and an n-th turn improves insertion loss and/or mode conversion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Details of specific embodiments and central principles of operation are explained in more detail with reference to schematic figures. They show:

[0039] FIG. 1 a common mode choke in which a first turn is located in a different spatial region compared to an n-th turn.

[0040] FIG. 2 a first winding with different winding lengths.

[0041] FIG. 3 a common mode choke with toroidal core of varied diameter along the longitudinal position.

[0042] FIG. 4 an exploded view of a common mode choke with a first coil core, each with a rectangular cross-section.

[0043] FIG. 5 a view of a common mode choke parallel to the vertical direction in which both coil cores and both windings are tapered.

[0044] FIG. 6 also shows a view of a common mode choke parallel to the vertical direction, in which the coil cores and coils are aligned antiparallel to each other.

[0045] FIG. 7 the insertion loss for common mode signals of a conventional choke (B) and a choke as described above (A).

[0046] FIG. 8 a comparison of the mode conversion reflection between a conventional common mode choke (B) and a choke as described above (A).

[0047] FIG. 9 an explanation of the term “mode conversion” from common mode signal to push-pull signal.

DETAILED DESCRIPTION

[0048] FIG. 1 shows a common mode choke GTD with a first winding WICK1 and a second winding WICK2. The first winding WICK1 has a first turn WIN1, a second turn WIN2 and an n-th turn WINS. The first winding is arranged in a first space region B1. The n-th turn is arranged in a second space region B2. The two spatial areas B1, B2 differ in that the coupling of the first turn WIN1 to the second turn WIN2 and of the n-th turn WIN3 to the second turn WIN2 are different.

[0049] The different coupling of the respective turns to the second turn results in the common mode choke having improved insertion loss in a higher frequency range on the one hand and reduced reflection (S.sub.11) for the conversion of common mode signals in a wide frequency range.

[0050] The number of turns is of course not limited to two or three per winding. The windings may have a plurality, for example 10, 20, 50, 100, 200, 500 or 1000 turns. Preferably, the first winding has as many turns as the second winding. The second winding WICK2 can be symmetrical to the first winding WICK1 and can be connected in the same way or in an antiparallel way.

[0051] FIG. 2 shows a possible embodiment to make the couplings between the turns different. FIG. 2 shows the possibility to design the length of the turns differently, so that the second turn WIN2 has a turn length (length of the conductor of the turn) which is between the length of the n-th turn WIN3 and the length of the first turn WIN1.

[0052] FIG. 3 shows another possibility to adjust the couplings differently. For example, the windings can have essentially the same, homogeneous winding structure, while the magnetic core is designed in such a way that its cross-sectional diameter increases or decreases along the longitudinal axis Z, respectively. In this case, the core can be designed as a toroidal core, where a part of the toroidal core is considered as a first magnetic core, that is, as a magnetic core of the first winding, while another part of the magnetic core is considered as a second magnetic core, that is, as a magnetic core of the second winding WICK2.

[0053] FIG. 4 shows another possibility to adjust the coupling accordingly. Thus, the first winding WICK2 is wound around a magnetic core which is trapezoidal in shape. In particular, the magnetic core K1 has a rectangular cross-section along each longitudinal position Z, with the area of the rectangle decreasing as the position along the longitudinal direction Z increases. The two magnetic cores are thereby magnetically coupled by corresponding sections J1, J2 of a yoke.

[0054] FIG. 5 shows the possibility of making both the windings and the magnetic cores conical. This means that the cross-section along the longitudinal axis is essentially circular with a radius that decreases as the longitudinal position Z increases. Furthermore, FIG. 5 shows the possibility of designing the common mode choke GTD as an SMD component. Thus, the common mode choke GTD has four external connections EA1, EA2, EA3, EA4, via which the common mode choke GTD can be electrically and mechanically connected to an external circuit environment via SMD methods. The four external connections EA1, EA2, EA3 and EA4 represent the connections of the two ports of the second port.

[0055] In contrast to FIG. 5, in which the directions of decrease of the diameters are arranged parallel, FIG. 6 shows an embodiment in which the directions are arranged antiparallel.

[0056] FIG. 7 shows the frequency-dependent insertion loss (S.sub.CC21) for a frequency range from 104 to 1010 Hz (in logarithmic representation). It can be clearly seen that curve A, which represents the electrical characteristics of the improved common mode choke as described above, shows the reduced insertion loss for the frequency range from 200 MHz (compare the dashed ellipse). FIG. 7 shows the electrical characteristics for signals where common mode signals are considered at both the input port and the output port.

[0057] In contrast, FIG. 8 indicates the improvement in the suppression of reflection (S.sub.DC11), considering common mode signals at the first port (input port) and also push-pull signals at the first port (output port). FIG. 8 thus clearly indicates that the common mode choke described above exhibits a substantial improvement in reflection during mode conversion. The improvement is 15 to 20 dB.

[0058] FIG. 9 illustrates the consideration of mode conversion with respect to FIG. 8: At the first port, the input port, common mode signals are considered, while at the second port, the output port, push-pull signals are considered. In common mode signals, an electrical signal propagates in two parallel signal lines essentially in phase. In push-pull signals, an electrical signal propagates in two parallel signal paths essentially in phase opposition, i.e. with a phase offset of 180°.

[0059] The common mode choke is not limited to the forms shown. Chokes having further circuit elements and/or further structural elements, for example for mechanical connection of core, winding or yoke, or chokes having further electrical contact surfaces or contact surfaces on different sides of the choke, also belong to the above description.

LIST OF REFERENCE SIGNS

[0060] (A) Scattering matrix parameter S.sub.CCC21 of a conventional common mode choke [0061] (A′) Scattering matrix parameter S.sub.DC11 of a conventional common mode choke [0062] (B) Scattering matrix parameter S.sub.CC21 of an improved common mode choke [0063] (B′) Scattering matrix parameter S.sub.DC11 of an improved common mode choke [0064] B1, B2 First, second space area [0065] Comm Common mode signal [0066] Diff Push-pull (Counterclock) signal [0067] EA1, EA2, EA3, EA4 First, second, third, fourth external connection [0068] GTD Common mode choke [0069] J1, J2 First, second part of magnetic yoke [0070] K1, K2 First, second magnetic core [0071] WICK1, WICK2 First, second winding [0072] WIN1, WIN2, WINS First, second, n-th turn [0073] Z Longitudinal direction