This application claims priority of Taiwanese application no. 102200792, filed on Jan. 14, 2013.
1. Field of the Invention
The present invention relates to a common mode filter.
2. Description of the Related Art
In recent years, as the amount of data transfer increases, differential signals are being used widely in high-speed data transmission. Although differential signals generally perform better in terms of resistance to noise and electromagnetic interference, common mode (common mode) noise will still be generated in the circuit paths due to the impacts of the actual circuit layout and its surrounding environment, causing transmission signal distortion and electromagnetic interference. Furthermore, the common-mode noise is the main source of electron radiation. Therefore, in order to comply with the electromagnetic compatibility (EMC) standard, the conversion between common mode and differential mode in the data signal suppressed, i.e., the problem of mode conversion, must be effectively
Referring
The positive conductor structure 12 and the negative conductor structure 13 are arranged closely adjacent to each other on an X-axis that is perpendicular with the Y-axis and overlap each other on a Z-axis that is perpendicular with the Y-axis and the X-axis. Therefore, the symmetry and balance of the positive conductor structure 12 and the negative conductor structure 13 in the electromagnetic field is poor, resulting in poor suppression of mode conversion. Moreover, the overlapping areas of the positive conductor structure 12 and the negative conductor structure 13 generate parasitic capacitance, thereby degrading the electrical characteristics of the common mode filter.
The object of the present invention is to provide a common mode filter that is capable of mitigating mode conversion problems in differential signals.
According to this invention, a common mode filter includes a plurality of substrates stacked along an axial direction, a first conductor structure disposed on the substrates and including a plurality of first rings connected electrically in series and disposed sequentially along the axial direction, and a second conductor structure disposed on the substrates and including a plurality of second rings connected electrically in series and disposed sequentially along the axial direction.
The first rings and the second rings are disposed to alternate with each other along the axial direction. The first conductor structure and the second conductor structure are spaced apart by a first clearance in a first direction transverse to the axial direction.
Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiments with reference to the accompanying drawings, of which:
Before the present invention is described in greater detail with reference to the preferred embodiments, it should be noted herein that like elements are denoted by the same reference numerals in the following detailed description.
Referring to
The plurality of substrates 2 are stacked along an axial direction Y, and are disposed on the base 3.
The first conductor structure 4 is disposed on the substrates 2 and includes a plurality of first rings 41 connected electrically in series and disposed sequentially along the axial direction Y.
In this embodiment, each of the first rings 41 has a first ring section 411, a second ring section 412 disposed opposite to the first ring section 411, a first connecting section 413 connected between the first ring section 411 and the second ring section 412, and a second connecting section 414 disposed opposite to the first connecting section 413 and connected between the first ring section 411 and the second ring section 412.
The second conductor structure 5 is disposed on the substrates 2 and includes a plurality of second rings 51 connected electrically in series and disposed sequentially along the axial direction Y. The first rings 41 and the second rings 51 are disposed to alternate with each other along the axial direction Y.
In this embodiment, each of the second rings 51 has a first ring segment 511 disposed adjacent to the first ring sections 411 of the first rings 41, and a second ring segment 512 disposed opposite to the first ring segment 511. Each of the second rings 51 further has a first connecting segment 513 disposed adjacent to the first connecting sections 413 of the first rings 41 and connected between the first ring segment 511 and the second ring segment 512, and a second connecting segment 514 disposed opposite to the first connecting segment 513 and connected between the first ring segment 511 and the second ring segment 512.
In this embodiment, the first rings 41 and the second rings 51 are substantially similar in size and shape and are preferred to be substantially rectangular. However, the first rings 41 and the second rings 51 may have the shape of a square or other shapes in other embodiments of this invention.
Preferably, the first conductor structure 4 has a first axis L1, and the second conductor structure 5 has a second axis L2. The second axis L2 forms a first offset with the first axis L1 in a first direction X transverse to the axial direction Y, and further forms a second offset with the first axis L1 in a second direction Z transverse to the first direction X and the axial direction Y.
In this embodiment, the first offset is sufficient to space the first ring sections 411 of the first rings 41 apart from the first ring segments 511 of the second rings 51 by the first clearance 71 in the first direction X, and to space the second ring sections 412 of the first rings 41 apart from the second ring segments 512 of the second rings 51 by a second clearance 72 in the first direction X.
Moreover, the second offset is sufficient to configure projections of the first connecting sections 413 of the first rings 41 on a virtual plane perpendicular to the axial direction Y to be substantially free from overlap with projections of the first connecting segments 513 of the second rings 51 on the virtual plane, and to configure projections of the second connecting sections 414 of the first rings 41 on the virtual plane to be substantially free from overlap with projections of the second connecting segments 514 of the second rings 51 on the virtual plane.
In this embodiment, each of the first ring sections 411, the second ring sections 412, the first ring segments 511 and the second ring segments 512 extends in the second direction Z, and each of the first connecting sections 413, the second connecting sections 414, the first connecting segments 513 and the second connecting segments 514 extends in the first direction X. Moreover, the first ring sections 411 and the second ring segments 512 are disposed between the first ring segments 511 and the second ring sections 412 in the first direction X, and the second connecting sections 414 and the first connecting segments 513 are disposed between the first connecting sections 413 and the second connecting segments 514 in the second direction Z.
The terminal electrodes 6 are provided on the base 3, and are electrically connected with the first conductor structure 4 and the second conductor structure 5, respectively.
Referring to
The advantages of the present invention can be summarized as follows:
The new layout is designed such that the first ring sections 411 of the first rings 41 are spaced apart from the first ring segments 511 of the second rings 51 by a first clearance 71 in a first direction X transverse to the axial direction Y, and the second ring sections 412 of the first rings 41 are spaced apart from the second ring segments 512 of the second rings 51 by a second clearance 72 in the first direction X.
Therefore, by virtue of the clearances 71, 72 in the first direction X, the symmetry and balance of the first conductor structure 4 and the second conductor structure 5 in the electromagnetic field is improved, resulting in improvements in the suppression of mode conversion problems in differential signals.
Furthermore, since the projections of the first connecting sections 413 of the first rings 41 on a virtual plane perpendicular to the axial direction Y are substantially free from overlap with projections of the first connecting segments 513 of the second rings 51 on the virtual plane, and since the projections of the second connecting sections 414 of the first rings 41 on the virtual plane are substantially free from overlap with projections of the second connecting segments 514 of the second rings 51 on the virtual plane, the parasitic capacitance problem encountered in the prior art and attributed to overlapping conductor parts can be mitigated, thus improving the electrical characteristics of the common mode filter of the first preferred embodiment.
In the second preferred embodiment, the first rings 41 and the second rings 51 have different sizes, the first ring sections 411 of the first rings 41 are spaced apart from the first ring segments 511 of the second rings 51 by a first clearance 71 in the first direction X transverse to the axial direction Y, and the second ring sections 412 of the first rings 41 do not form a second clearance in the first direction X with the second ring segments 512 of the second rings 51.
Referring once again to
In summary, not only are the symmetry and balance of the first conductor structure 4 and the second conductor structure 5 in the electromagnetic field improved, suppression of mode conversion problems in differential signals are improved as well.
While the present invention has been described in connection with what are considered the most practical and preferred embodiments, it is understood that this invention is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.
Number | Date | Country | Kind |
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102200792 | Jan 2013 | TW | national |