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WO2007013052A1 - Module d'interference electromagnetique pour communication de donnees equilibree - Google Patents

Module d'interference electromagnetique pour communication de donnees equilibree Download PDF

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Publication number
WO2007013052A1
WO2007013052A1 PCT/IL2005/000803 IL2005000803W WO2007013052A1 WO 2007013052 A1 WO2007013052 A1 WO 2007013052A1 IL 2005000803 W IL2005000803 W IL 2005000803W WO 2007013052 A1 WO2007013052 A1 WO 2007013052A1
Authority
WO
WIPO (PCT)
Prior art keywords
sef
transmission line
ground
absorption filter
layer
Prior art date
Application number
PCT/IL2005/000803
Other languages
English (en)
Inventor
Alex Axelrod
Zeev Shpiro
Original Assignee
Alex Axelrod
Zeev Shpiro
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Alex Axelrod, Zeev Shpiro filed Critical Alex Axelrod
Priority to PCT/IL2005/000803 priority Critical patent/WO2007013052A1/fr
Publication of WO2007013052A1 publication Critical patent/WO2007013052A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0264—Arrangements for coupling to transmission lines
    • H04L25/0272—Arrangements for coupling to multiple lines, e.g. for differential transmission
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
    • H03H7/42—Networks for transforming balanced signals into unbalanced signals and vice versa, e.g. baluns
    • H03H7/425—Balance-balance networks
    • H03H7/427—Common-mode filters
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/08—Modifications for reducing interference; Modifications for reducing effects due to line faults ; Receiver end arrangements for detecting or overcoming line faults
    • H04L25/085—Arrangements for reducing interference in line transmission systems, e.g. by differential transmission
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H1/00—Constructional details of impedance networks whose electrical mode of operation is not specified or applicable to more than one type of network
    • H03H2001/0021—Constructional details
    • H03H2001/0035—Wound magnetic core
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
    • H03H7/01—Frequency selective two-port networks
    • H03H7/0107—Non-linear filters
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
    • H03H7/01—Frequency selective two-port networks
    • H03H7/17—Structural details of sub-circuits of frequency selective networks
    • H03H7/1741—Comprising typical LC combinations, irrespective of presence and location of additional resistors
    • H03H7/175—Series LC in series path
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
    • H03H7/01—Frequency selective two-port networks
    • H03H7/17—Structural details of sub-circuits of frequency selective networks
    • H03H7/1741—Comprising typical LC combinations, irrespective of presence and location of additional resistors
    • H03H7/1775—Parallel LC in shunt or branch path

Definitions

  • the present invention generally relates to balanced data communication systems, and more particularly to filters for reducing or eliminating electromagnetic interference (EMI) in balanced data communication systems.
  • EMI electromagnetic interference
  • Electromagnetic interference is one of the factors that limits range and data rate in data communication systems. In order to reduce interference from ambient electromagnetic environment, data communication systems typically use balanced transmission lines.
  • DM differential mode
  • CM common mode
  • the present invention in preferred embodiments thereof, seeks to provide an electromagnetic interface module (EIM) for balanced data communication with improved filtering capabilities.
  • EIM electromagnetic interface module
  • CM common mode
  • EMI electromagnetic interference
  • the apparatus including a first Single Ended Filter (SEF) operatively associated with a first path of the balanced transmission line, and a second SEF operatively associated with a second path of the balanced transmission line, wherein a ground terminal of the first SEF and a ground terminal of the second SEF are electrically connected to a local ground.
  • SEF Single Ended Filter
  • the ground terminal of the first SEF and the ground terminal of the second SEF are electrically connected to the local ground via at least one of the following connections: a direct connection, a connection via a capacitor, and a connection via low-impedance circuitry.
  • the local ground preferably includes at least one of the following: a local conductive chassis ground, a shield of host equipment, a housing of host equipment, a massive printed circuit ground plane, and a massive conductive plate.
  • the first SEF and the second SEF have substantially similar electrical characteristics.
  • Each of the first SEF and the second SEF preferably includes a SEF having an insertion loss which is below an insertion loss threshold at least within the specified frequency band.
  • each of the first path and the second path includes at least one conductor, and each conductor is associated with at least one SEF.
  • the balanced transmission line preferably includes a twisted pair of conductors.
  • at least one of the apparatus is included in a data link interface module.
  • the data link interface module may also include at least one of the following connectors: an RJ45 connector, a Universal Serial Bus (USB) connector, and a D-type connector.
  • an absorption filter for reducing electromagnetic interference (EMI) in a transmission line including at least one conductor carrying functional signals propagating over the transmission line, at least one layer of composite absorbing material at least partially coating the at least one conductor, the at least one layer of composite absorbing material including a mixture of amorphous metal particles and an isolating material, and at least one conductive layer substantially coating the at least one layer of composite absorbing material, wherein the at least one conductive layer is conductively connected to a local ground.
  • EMI electromagnetic interference
  • the transmission line includes one of the following: at least one single-ended transmission line, and at least one balanced transmission line.
  • the isolating material preferably includes a dielectric material having at least one of the following properties: a dielectric loss greater than a dielectric loss threshold value, and a dielectric constant greater than a dielectric constant threshold value.
  • the isolating material may include Barium Titanate.
  • the local ground includes at least one of the following: a local conductive chassis ground, a shield of host equipment, a housing of host equipment, a massive printed circuit ground plane, and a massive conductive plate.
  • the at least one conductor preferably includes at least one of the following: a metallic conductor, a conductive adhesive, a conductive paint, a conductive plastic material, and a resin loaded with a conductive material.
  • the at least one conductor includes a plurality of pairs of conductors arranged in an arrangement in which an electromagnetic (EM) field generated by a differential-mode (DM) functional signal within a volume occupied by the at least one layer of composite absorbing material is below an EM field threshold level.
  • the at least one conductor may include two pairs of conductors arranged in a quad configuration.
  • the at least one conductor includes at least one of the following: a pair of twisted wires, a multiple of pairs of twisted wires, and a multiple of two pairs of twisted wires.
  • the absorption filter, or a plurality thereof is included in a data link interface module.
  • CM common mode
  • EMI electromagnetic interference
  • CM common mode
  • EMI electromagnetic interference
  • a method for reducing electromagnetic interference (EMI) in a transmission line including providing at least one conductor carrying functional signals propagating over the transmission line, at least partially coating the at least one conductor by at least one layer of composite absorbing material, the at least one layer of composite absorbing material including a mixture of amorphous metal particles and an isolating material, substantially coating the at least one layer of composite absorbing material by at least one conductive layer, and conductively connecting the at least one conductive layer to a local ground.
  • EMI electromagnetic interference
  • a method for reducing electromagnetic interference (EMI) in a balanced transmission line including providing at least four wires arranged in a quad transmission configuration and carrying functional signals propagating over the balanced transmission line, at least partially coating the at least four wires by at least one layer of composite absorbing material, the at least one layer of composite absorbing material including a mixture of amorphous metal particles and an isolating material, substantially coating the at least one layer of composite absorbing material by at least one conductive layer, and conductively connecting the at least one conductive layer to a local ground.
  • EMI electromagnetic interference
  • Fig. 1 is a simplified block diagram illustration of a prior art electromagnetic interface module (EIM) for a single balanced communication interface;
  • EIM electromagnetic interface module
  • Fig. 2 is a simplified partly pictorial partly block diagram illustration of a preferred implementation of an EIM constructed and operative in accordance with a preferred embodiment of the present invention
  • Fig. 3 is a simplified block diagram illustration of a preferred implementation of an integrated EIM comprising more than one of the EIM of Fig. 2, the integrated EIM being constructed and operative in accordance with a preferred embodiment of the present invention;
  • Fig. 4 is a simplified partly pictorial partly block diagram illustration of a preferred implementation of apparatus in the EIM of Fig. 2 for reducing a CM electromagnetic interference in a balanced transmission line which carries a differential signal occupying a specified frequency band, the apparatus being constructed and operative in accordance with a preferred embodiment of the present invention;
  • Fig. 5 is a circuit diagram of a typical low-pass Single-Ended Filter (SEF);
  • Fig. 6 is a circuit diagram of a typical band-pass SEF;
  • Figs. 6A and 6B demonstrate CM rejection of an EIM including the apparatus of Fig. 4 (shown in Fig. 6B) versus CM rejection of commercially available integrated interface modules (shown in Fig. 6A);
  • Fig. 7 is a simplified partly pictorial partly block diagram illustration of a preferred implementation of a single-ended absorption filter, the single-ended absorption filter being constructed and operative in accordance with a preferred embodiment of the present invention
  • Fig. 8 is a graph showing differential mode (DM) attenuation performance of the absorption filter of Fig. 7 with an interaction length of 100mm and utilization of a twisted pair of round wires
  • Fig. 9 is a graph showing common mode (CM) rejection performance of the absorption filter of Fig. 7 with an interaction length of 100mm;
  • Fig. 10 is a simplified partly pictorial partly block diagram illustration of a preferred implementation of two single-ended absorption filters on a balanced transmission line in accordance with a preferred embodiment of the present invention
  • Fig. 11 is a simplified partly pictorial partly block diagram illustration of a preferred implementation of a balanced absorption filter, the balanced absorption filter being constructed and operative in accordance with a preferred embodiment of the present invention
  • Fig. 12 is a simplified pictorial illustration of a preferred implementation of an absorption filter operating on a quad transmission line, the absorption filter being constructed and operative in accordance with a preferred embodiment of the present invention
  • Fig. 13 is a simplified pictorial illustration of another preferred implementation of an absorption filter operating on a quad transmission line, the absorption filter being constructed and operative in accordance with a preferred embodiment of the present invention
  • Fig. 14 is a simplified pictorial illustration of an absorption filter having a coil shape, the absorption filter being constructed and operative in accordance with a preferred embodiment of the present invention
  • Fig. 15 is a simplified flowchart illustration of a preferred method of operation of the apparatus of Fig. 4;
  • Fig. 16 is a simplified flowchart illustration of another preferred method of operation of the apparatus of Fig. 4;
  • Fig. 17 is a simplified flowchart illustration of a preferred method of operation of the absorption filter of Fig. 7; and
  • Fig. 18 is a simplified flowchart illustration of a preferred method of operation of any of the absorption filter of Fig. 12 and the absorption filter of Fig. 13.
  • Fig. 1 is a simplified block diagram illustration of a prior art electromagnetic interface module (EIM) 100 for a single balanced communication interface.
  • EIM electromagnetic interface module
  • the EIM 100 is associated with a printed circuit board (PCB) 101 and system terminals 102 and includes commercially available components comprising: a common mode chock (CMC) 103; a line isolation transformer 104; a cable connector 105 connected to a data communication cable
  • PCB printed circuit board
  • CMC common mode chock
  • line isolation transformer 104 a line isolation transformer 104
  • cable connector 105 connected to a data communication cable
  • the EIM 100 may be used on conventional 10/100BaseT and lOOOBaseT local area network (LAN) interfaces.
  • EIMs suffer from low common mode (CM) rejection at frequencies above 150MHz.
  • CM common mode
  • EMC electromagnetic compatibility
  • Fig. 2 is a simplified partly pictorial partly block diagram illustration of a preferred implementation of an EIM 200 constructed and operative in accordance with a preferred embodiment of the present invention.
  • the EIM 200 preferably includes apparatus 210 for reducing a CM electromagnetic interference (EMI) in a balanced transmission line 220 which carries a differential signal occupying a specified frequency band, and an absorption filter 230.
  • EMI CM electromagnetic interference
  • balanced transmission line is used throughout the present specification and claims to include a line having conductors with equal resistance per unit length and equal capacitance and inductance between each conductor and ground.
  • the apparatus 210 is preferably operatively associated with conventional system terminals
  • the EIM 200 may optionally include a conventional CMC 250 in which case the absorption filter 230 is operatively associated with the CMC 250.
  • the CMC 250 is connected to a line isolation transformer 260 that is also comprised in the EIM 200, and the line isolation transformer 260 is connected to the balanced transmission line 220 via a cable connector 270.
  • the absorption filter 230 is preferably operatively associated with the line isolation transformer 260.
  • FIG. 3 is a simplified block diagram illustration of a preferred implementation of an integrated EIM 250 comprising more than one of the EIM 200 of Fig. 2, the integrated EIM 250 being constructed and operative in accordance with a preferred embodiment of the present invention.
  • the integrated EIM 250 is associated with N channels 260, where N is an integer greater than one.
  • N is an integer greater than one.
  • Each of the N channels 260 is operatively associated with an EIM 200, and all the EIMs 200 that are associated with the N channels 260 are preferably comprised in the integrated EIM 250.
  • the integrated EIM 250 is preferably operatively associated with a PCB 270.
  • Fig. 4 is a simplified partly pictorial partly block diagram illustration of a preferred implementation of the apparatus 210 in the EIM 200 of Fig. 2, the apparatus 210 being constructed and operative in accordance with a preferred embodiment of the present invention. It is appreciated that at least one of the apparatus 210 may be comprised in a data link interface module (not shown) and/or in a balanced data communication system (not shown).
  • the data link interface module may preferably include at least one of the following: an RJ45 connector; a Universal Serial Bus (USB) connector; and a D-type connector.
  • the apparatus 210 preferably includes a first Single Ended Filter (SEF) 310 and a second SEF 320.
  • SEF Single Ended Filter
  • the term "Single Ended Filter” is used throughout the present specification and claims to include an unbalanced filter circuit, as when one part of the unbalanced filter circuit is grounded.
  • the SEF 310 is preferably operatively associated with a first path 330 of a balanced transmission line, and the SEF 320 is preferably operatively associated with a second path 340 of the balanced transmission line.
  • the SEF 310 and the SEF 320 are preferably separate from each other, that is, there is no electrical connection between the SEF 310 and the SEF 320.
  • each of the first path 330 and the second path 340 includes at least one conductor which is associated with at least one of the SEF 310 and the SEF 320.
  • the balanced transmission line preferably includes a twisted pair of conductors in which case the first path 330 preferably includes a first conductor of the twisted pair, and the second path 340 preferably includes a second conductor of the twisted pair.
  • a ground terminal electrode 350 of the first SEF 310 and a ground terminal electrode 360 of the second SEF 320 are electrically connected to a local ground 370.
  • the SEF 310 and the SEF 320 are therefore preferably grounded via an electrical connection.
  • the electrical connection preferably includes at least one of the following connections: a direct connection; a connection via a capacitor; and a connection via low-impedance circuitry.
  • the local ground 370 preferably includes a local chassis ground comprising at least one of the following: a local conductive chassis ground; a shield of host equipment; a housing of host equipment; a massive printed circuit ground plane; and a massive conductive plate.
  • the SEF 310 and the SEF 320 have substantially similar electrical characteristics.
  • Each of the SEF 310 and the SEF 320 preferably includes at least one of the following: a low-pass filter (LPF); and a band-pass filter (BPF).
  • LPF low-pass filter
  • BPF band-pass filter
  • Each of the SEF 310 and the SEF 320 preferably includes a SEF having an insertion loss which is below an insertion loss threshold at least within a specified frequency band occupied by a differential signal carried over the balanced transmission line.
  • the insertion loss threshold may, for example, be IdB within a frequency band below 80MHz which is occupied by a 100BaseT differential-mode signal, as in many commercially available RJ45 connectors integrated with EMI filters
  • each of the SEF 310 and the SEF 320 includes at least one of the following types of SEF: a Butterworth SEF; a Chebyshev SEF; an Elliptic SEF; and a ladder SEF.
  • a typical embodiment of each of the SEF 310 and the SEF 320 in a configuration of a low-pass SEF of the ladder type is depicted in Fig. 5.
  • a typical embodiment of each of the SEF 310 and the SEF 320 in a configuration of a band-pass SEF of the ladder type is depicted in Fig. 6.
  • the low-pass SEF in Fig. 5 preferably includes at least one capacitor referred to ground.
  • a capacitor 400 is referred to ground 410 and a capacitor 420 is referred to ground 430.
  • the capacitors 400 and 420 are preferably referred to ground via ground terminals 440 and 450 that are preferably connected by a low-impedance connection to the ground 410 and the ground 430, respectively.
  • Each of the ground 410 and the ground 430 preferably includes a local ground comprising at least one of the following: a local conductive chassis ground; a shield of host equipment; a housing of host equipment; a massive printed circuit ground plane; and a massive conductive plate (all not shown).
  • the low-pass SEF is preferably connected in series to one of the paths 330 and 340 of Fig. 4 via terminals 460 and 470. It is appreciated that transient protection elements, such as Transient Voltage Suppressor (TVS) diodes 480 may optionally be comprised in the low-pass SEF. It is further appreciated that junction capacitances of TVS diodes are part of SEF capacitance.
  • TVS Transient Voltage Suppressor
  • the band-pass SEF in Fig. 6 also preferably includes at least one capacitor referred to ground terminals.
  • a capacitor 500 is referred to a local ground 510 and a capacitor 520 is referred to a local ground 530.
  • the capacitors 500 and 520 are preferably referred to ground via ground terminals 540 and 550 that are preferably connected by a low-impedance connection to the ground 510 and the ground 530, respectively.
  • Each of the ground 510 and the ground 530 preferably includes a local ground comprising at least one of the following: a local conductive chassis ground; a shield of host equipment; a housing of host equipment; a massive printed circuit ground plane; and a massive conductive plate (all not shown).
  • the band-pass SEF is preferably connected in series to one of the paths 330 and 340 of Fig. 4 via terminals 560 and 570.
  • the local ground 370 is provided for grounding of the ground terminals 350 and 360 of the SEFs 310 and 320.
  • the SEF 310 is preferably operatively associated with the first path 330 of the balanced transmission line, for example by connecting the SEF 310 in series to each conductor in the first path 330.
  • the SEF 320 is preferably operatively associated with the second path 340 of the balanced transmission line, for example by connecting the SEF 320 in series to each conductor in the second path 340.
  • the ground terminal electrode 350 of the SEF 310 and the ground terminal electrode 360 of the SEF 320 are preferably electrically connected to the local ground 370, for example, via a low-impedance connection to the base.
  • LPFs are used in differential-mode (DM) configurations. Such LPFs do not have a ground terminal bonded to a local ground, such as an equipment chassis. Naturally, such LPFs provide filtering of DM signals and are not effective for CM rejection.
  • the present invention in preferred embodiments thereof, provides an electromagnetic interface (EIM) for balanced data communication in which ground terminals of SEFs are electrically connected to a local ground to obtain CM reduction or rejection.
  • EIM electromagnetic interface
  • the apparatus 210 is intended to provide low DM attenuation within a frequency band occupied by a spectrum of the DM signal, high attenuation in all other frequencies, and as much as possible CM noise rejection at any frequency.
  • a plurality of the apparatus 210 may be used for CM noise rejection in a plurality of balanced data communication channels. It is appreciated that connection of the ground terminal electrode 350 of the SEF 310 and the ground terminal electrode 360 of the SEF 320 to the local ground 370 results in significantly enhanced attenuation for both DM and CM interference signals when compared to conventional implementations. Demonstrations of CM rejection of an EIM including the apparatus 210 versus CM rejection of commercially available integrated interface modules are shown in Figs. 6B and 6A, respectively. It is appreciated that the apparatus 210 provides CM reduction in the range of at least 80MHz - 1.3GHz where conventional CM chokes and LAN transformers have relatively degraded performance. The apparatus 210 also enables low-cost manufacturing and miniature packaging.
  • Fig. 7 is a simplified partly pictorial partly block diagram illustration of a preferred implementation of a single-ended absorption filter 600, the single-ended absorption filter 600 being constructed and operative in accordance with a preferred embodiment of the present invention.
  • the absorption filter 600 is preferably used for reducing EMI in a transmission line (not shown).
  • the transmission line preferably includes one of the following: at least one single-ended transmission line; and at least one balanced transmission line. It is appreciated that absorption filter 600 may be comprised in a data link interface module
  • the absorption filter 600 includes the following elements: at least one conductor 610; at least one layer of composite absorbing material 620; and at least one conductive layer 630.
  • the at least one conductor 610 preferably carries functional signals propagating over the transmission line.
  • the at least one conductor 610 preferably includes at least one of the following: a metallic conductor; a conductive adhesive; a conductive paint; a conductive plastic material; and a resin loaded with a conductive material.
  • the metallic conductor preferably includes at least one of the following: a pair of twisted wires; a multiple of pairs of twisted wires; and a multiple of two pairs of twisted wires. It is appreciated that the at least one conductor 610 may be coated by an isolation layer 640.
  • the at least one layer of composite absorbing material 620 at least partially coats the at least one conductor 610.
  • the at least one conductive layer 630 preferably substantially coats the at least one layer of composite absorbing material 620.
  • the at least one conductive layer 630 is conductively connected to a local ground (not shown) at least at one location (not shown).
  • Conductive connection of the at least one conductive layer 630 is preferably obtained via an electrical connection.
  • the electrical connection preferably includes at least one of the following connections: a direct connection; a connection via a capacitor; and a connection via low- impedance circuitry.
  • the local ground preferably includes at least one of the following: a local conductive chassis ground; a shield of host equipment; a housing of host equipment; a massive printed circuit ground plane; and a massive conductive plate (all not shown).
  • the at least one layer of composite absorbing material 620 preferably includes a mixture of amorphous metal particles and an isolating material.
  • the amorphous metal particles are preferably immersed in the isolating material.
  • the amorphous metal particles include a Cobalt-based alloy comprising Cobalt (Co) as the principal material.
  • the Cobalt-based alloy includes, for example which is not meant to be limiting, one of the following compositions of materials:
  • a composition of materials comprising, in weight, the following: 0.067% Oxygen, 11.709% Boron, 12.648% Silicon, 3.605% Chromium, 4.269% Iron, 0.051% Nickel, and 67.651% Cobalt.
  • composition of materials comprising, in weight, the following: 0.083% Oxygen, 11.143% Boron, 12.569% Silicon, 3.732% Chromium, 3.625% Iron, 0.151% Nickel, and 68.697% Cobalt.
  • Cobalt-based alloy compositions similar to the Compositions (1) and (2) but with weights deviating from the weights in each of the Compositions (1) and (2) by up to +/-20% in quantity of each material are also appropriate.
  • the isolating material preferably includes a dielectric material having at least one of the following properties: a dielectric loss greater than a dielectric loss threshold value; and a dielectric constant greater than a dielectric constant threshold value.
  • the dielectric constant threshold may, for example, be a relative dielectric constant of several tens, several hundreds or even several thousands.
  • the dielectric loss threshold value may, for example, be tan( ⁇ ) ⁇ 0.01.
  • the isolating material includes Barium Titanate.
  • the absorption filter 600 is intended to provide enhanced CM attenuation at frequencies above 200-300MHz, and even higher CM attenuation at frequencies of 1 - 20 GHz.
  • the absorption filter 600 attenuates CM interference signals by at least 40-5OdB above IGHz.
  • the absorption filter 600 may be complimentary to conventional EMI L-C filters above 1-2GHz, where parasitic elements of EMI L-C filters deteriorate their performance.
  • the absorption filter 600 also preferably provides appropriate low attenuation to DM signals, typically up to 2-3dB DM loss in a frequency band up to several hundreds of MHz. Thus, the absorption filter 600 is useful for highspeed data communication applications.
  • DM Attenuation performance of the absorption filter 600 with an interaction length of 100mm and utilization of a twisted pair of round wires is shown in Fig. 8.
  • CM Rejection performance of the absorption filter 600 with an interaction length of 100mm is shown in Fig. 9.
  • the absorption filter 600 also provides a high degree of isolation between receive and transmit channels.
  • the absorption filter 600 also may be implemented in a miniature package and offers low-cost manufacturing.
  • the operation of the absorption filter 600 is based upon different spatial distribution of electromagnetic fields generated by DM and CM currents propagating along data communication transmission lines. Attenuation versus frequency response may be controlled by the at least one layer of composite absorbing material 620, cross-sectional geometry, and length of interaction between the transmission line and the at least one layer of composite absorbing material 620.
  • confinement of a dissipated electromagnetic field of an interference signal inside the at least one layer of composite absorbing material 620 is achieved by longwise coating of the at least one layer of composite absorbing material 620 by the at least one conductive layer 630.
  • Absorption preferably occurs on the surfaces of the amorphous metal particles. Isolation between the metal particles enables better penetration of the electromagnetic field into the composite absorbing material. Conventional methods may be applied in order to achieve a desired isolation between the metal particles.
  • Fig. 10 is a simplified partly pictorial partly block diagram illustration of a preferred implementation of two single-ended absorption filters 700 and 710 on a balanced transmission line in accordance with a preferred embodiment of the present invention.
  • the balanced transmission line is operatively associated with the absorption filters 700 and 710 at an input port 720 and at an output port 730.
  • Each of the absorption filters 700 and 710 may be similar in structure and functionality to the absorption filter 600 of Fig. 7.
  • the absorption filters 700 and 710 are preferably conductively connected to a local ground at locations 740.
  • the absorption filters 700 and 710 attenuate both DM signals and CM signals. Such unselected attenuation implies that a configuration as depicted in Fig. 10 may be used only for low-speed signals with a spectrum occupying low frequencies, where the absorption filters 700 and 710 have negligible loss.
  • Fig. 11 is a simplified partly pictorial partly block diagram illustration of a preferred implementation of a balanced absorption filter 800, the balanced absorption filter 800 being constructed and operative in accordance with a preferred embodiment of the present invention.
  • the balanced absorption filter 800 is intended to reduce DM insertion loss as well as to provide CM rejection.
  • the absorption filter 800 is similar in structure and functionality to the absorption filter 600 except that the absorption filter 800 embeds a twisted pair of isolated wires 810 and 820 carrying DM functional signals and CM interference signals that propagate from an input side 830 of a balanced transmission line to an output side 840 of the balanced transmission line.
  • Each of the wires 810 and 820 may be electrically isolated by dielectric layers 850 and 860, respectively.
  • dielectric layers 850 and 860 respectively.
  • the pair of wires 810 and 820 may also be surrounded by a layer of low-loss dielectric material 870.
  • the layer 870, together with the pair of wires 810 and 820, preferably forms a cylinder with a diameter which is approximately a diameter of the dielectric layers 850 and 860 multiplied by a factor of 2. It is appreciated that the layer 870 is optional in applications that use signals that occupy frequencies below 200MHz.
  • the layer 870 is preferably surrounded by at least one layer of absorption material 880 which is preferably coated by at least one layer of conductive material 890.
  • Fig. 12 is a simplified pictorial illustration of a preferred implementation of an absorption filter 900 operating on a quad transmission line, the absorption filter 900 being constructed and operative in accordance with a preferred embodiment of the present invention.
  • the absorption filter 900 is also intended to reduce DM insertion loss as well as to provide CM rejection.
  • quad transmission line is used throughout the present specification and claims to include a transmission line having a series of four separately insulated conductors, generally twisted together.
  • conductive wires 910, 920, 930 and 940 constitute a quad transmission line configuration in which wires 910 and 920 are at the same positive signal potential, and wires 930 and 940 are at the same negative signal potential.
  • Such a quad configuration may be achieved by making electrical contact connections between wires 910 and 920, and between wires 930 and 940 at both input and output sides of the absorption filter 900. There may be additional contacts between the wires 910 and 920 at other locations along the absorption filter 900. Similarly, there may be additional contacts between the wires 930 and 940 at other locations along the absorption filter 900.
  • the quad transmission line is surrounded by at least one layer of low-loss dielectric composite absorbing material 950, covered by a conductive layer 960.
  • the conductive layer 960 is preferably conductively connected to a local ground (not shown) at least at one location (not shown). Conductive connection of the conductive layer 960 is preferably obtained via an electrical connection.
  • the electrical connection preferably includes at least one of the following connections: a direct connection; a connection via a capacitor; and a connection via low-impedance circuitry.
  • the local ground preferably includes at least one of the following: a local conductive chassis ground; a shield of host equipment; a housing of host equipment; a massive printed circuit ground plane; and a massive conductive plate (all not shown).
  • all four wires 910, 920, 930 and 940 constituting the quad transmission line are twisted, which leads to a reduction of a magnetic field generated by differential current mode within the composite absorbing material 950 with respect to a magnetic field generated by currents in a twisted pair of wires.
  • a magnetic field generated by CM currents remains, more or less, at the same level.
  • the quad transmission line configuration may be replaced by a configuration comprising a plurality of pairs of conductors, which plurality of pairs of conductors include more than two pairs of conductors.
  • the plurality of pairs of conductors is preferably arranged in an arrangement in which an electromagnetic (EM) field generated by a DM functional signal within a volume occupied by the least one layer 950 is below an EM field threshold level.
  • the EM field threshold level may, for example, correspond to a 2-3dB DM signal attenuation.
  • the configuration comprising a plurality of pairs of conductors may include a 2xN (N is an integer greater than two) arrangement in which first N wires include a path for direct current of a DM signal, and second N wires include a path for return current of the DM signal.
  • first N wires include a path for direct current of a DM signal
  • second N wires include a path for return current of the DM signal.
  • “positive" and “negative” wires are interleaved in a way that provides minimum EM field outside a volume occupied by the 2xN arrangement of wires.
  • the 2xN wires may be located at equal spaces from each other along a periphery of some low-loss round dielectric core, and each "positive" wire may be surrounded by two "negative” wires, and vice versa.
  • Fig. 13 is a simplified pictorial illustration of another preferred implementation of an absorption filter 1000 operating on a quad transmission line, the absorption filter 1000 being constructed and operative in accordance with a preferred embodiment of the present invention.
  • the absorption filter 1000 is also intended to reduce DM insertion loss as well as to provide CM rejection.
  • the absorption filter 1000 is similar in structure and functionality to the absorption filter 900 of Fig. 12 except for quad transmission line structure.
  • conductive wires 1010, 1020, 1030 and 1040 constitute a quad transmission line configuration in which wires 1010 and 1020 are at the same positive signal potential, and wires 1030 and 1040 are at the same negative signal potential.
  • Each of the wires 1010, 1020, 1030 and 1040 may be coated by an optional isolation layer.
  • the wires 1010, 1020, 1030 and 1040 are arranged over a surface of a dielectric cylinder core 1050 in a spiral (twisted) way. Due to quad configuration, an electromagnetic field generated by DM functional signal is primarily concentrated inside the dielectric cylinder core 1050. Field confinement within the dielectric cylinder core 1050 is better than in a twisted pair configuration thus resulting in lower DM insertion loss.
  • Each of the absorption filters 800 of Fig. 11, 900 of Fig. 12, and 1000 of Fig. 13 provides a relatively low attenuation to DM functional signals, and much greater attenuation to CM interference signals.
  • an outer side of the corresponding layers of composite absorbing material is coated by at least one conductive layer.
  • both sides of the at least one conductive layer are low- inductively connected or bonded to a local ground, where the local ground preferably includes at least one of the following: a local conductive chassis ground; a shield of host equipment; a housing of host equipment; a massive printed circuit ground plane; and a massive conductive plate (all not shown).
  • the corresponding composite absorbing material preferably includes a composite of magnetic powder immersed in a non-conductive dielectric binding material.
  • the magnetic powder may include, for example, a mixture of magnetic metal powder and ferrite powder.
  • the magnetic powder may include an amorphous metal alloy composed of Cobalt (Co), Iron (Fe), Nickel (Ni) and other elements.
  • the dielectric binding material may include, for example, a composition of plastic, or lacquer, or any other appropriate compound material.
  • the dielectric binding material may be loaded by (mixed with) a dielectric powder having a high dielectric constant, such as Barium Titanate.
  • CM attenuation of each of the absorption filters 600 of Fig. 7, 700 and 710 of Fig. 10, 800 of Fig. 11, 900 of Fig. 12, and 1000 of Fig. 13 strongly depends upon a length of interaction between current-carrying conductors and the corresponding composite absorbing material. Different attenuation may thus be achieved by varying absorption filters lengths.
  • a length of each of the absorption filters 600, 700, 710, 800, 900 and 1000 is considerably greater than a corresponding diameter of the absorption filters 600, 700, 710, 800, 900 and 1000.
  • longwise filter structures may be curled, coiled in one or more layers, made in a zigzag form, or packaged in any other appropriate way and installed, as necessary, on a substrate for convenient placement on a printed circuit board (PCB), or inside an EIM, such as the EIM 200 of Fig. 2.
  • PCB printed circuit board
  • Fig. 14 is a simplified pictorial illustration of an absorption filter 1100 having a coil shape, the absorption filter 1100 being constructed and operative in accordance with a preferred embodiment of the present invention.
  • the absorption filter 1100 preferably includes one of the absorption filters 600, 700, 710, 800, 900, and 1000.
  • the absorption filter 1100 is preferably placed on a substrate 1110.
  • a ground plane 1120 on the upper side of the substrate 1110 is, on one side, in low-inductance conductive contact 1130 with a conductive coating of the absorption filter 1100, and on the other side, in a low-inductance conductive contact with a ground electrode on the bottom of the substrate 1110 (not shown).
  • Such a low-inductance contact may be obtained by means of through holes and/or metallic coating of side walls of the substrate 1110.
  • Fig. 15 is a simplified flowchart illustration of a preferred method of operation of the apparatus 210 of Fig. 4.
  • the method of Fig. 15 is self-explanatory.
  • Fig. 16 is a simplified flowchart illustration of another preferred method of operation of the apparatus 210 of Fig. 4.
  • the method of Fig. 16 is self- explanatory.
  • Fig. 17 is a simplified flowchart illustration of a preferred method of operation of the absorption filter 600 of Fig. 7.
  • the method of Fig. 17 is self- explanatory.
  • Fig. 18 is a simplified flowchart illustration of a preferred method of operation of any of the absorption filter 900 of Fig. 12 and the absorption filter 1000 of Fig. 13.
  • the method of Fig. 18 is self-explanatory.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Filters And Equalizers (AREA)

Abstract

L'invention concerne un appareil permettant de réduire une interférence électromagnétique (EMI) en mode commun (CM) dans une ligne de transmission équilibrée qui supporte un signal différentiel occupant une bande de fréquence spécifiée. Ledit appareil comprend un premier filtre (310) à extrémité unique fonctionnellement associé à un premier chemin (330) et un second filtre (320) à extrémité unique fonctionnellement associé à un second chemin (340) de la ligne de transmission équilibrée, un terminal à la terre (370) du premier filtre à extrémité unique et un terminal à la terre (360) du second filtre (320) à extrémité unique étant connectés à une prise de terre locale (370). L'invention également concerne un appareil et des procédés associés.
PCT/IL2005/000803 2005-07-26 2005-07-26 Module d'interference electromagnetique pour communication de donnees equilibree WO2007013052A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/IL2005/000803 WO2007013052A1 (fr) 2005-07-26 2005-07-26 Module d'interference electromagnetique pour communication de donnees equilibree

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/IL2005/000803 WO2007013052A1 (fr) 2005-07-26 2005-07-26 Module d'interference electromagnetique pour communication de donnees equilibree

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WO2007013052A1 true WO2007013052A1 (fr) 2007-02-01

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Cited By (3)

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EP2779554A1 (fr) * 2013-03-15 2014-09-17 Intel Corporation Procédé, appareil et système pour atténuer l'interférence de fréquence radio à large bande
CN105929214A (zh) * 2016-04-14 2016-09-07 烽火通信科技股份有限公司 一种用于高速光眼图观测的触发信号产生装置及方法
US20230006865A1 (en) * 2020-05-12 2023-01-05 Saic Motor Corporation Limited Bidirectional isolated communication circuit and method for differential signal

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US4486721A (en) * 1981-12-07 1984-12-04 Raychem Corporation High frequency attenuation core and cable
US4888675A (en) * 1987-08-26 1989-12-19 Harris Corporation Switching power supply filter
US5095291A (en) * 1990-11-08 1992-03-10 North Hill Electronics, Inc. Communication filter for unshielded, twisted-pair cable
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US4486721A (en) * 1981-12-07 1984-12-04 Raychem Corporation High frequency attenuation core and cable
US4888675A (en) * 1987-08-26 1989-12-19 Harris Corporation Switching power supply filter
US5095291A (en) * 1990-11-08 1992-03-10 North Hill Electronics, Inc. Communication filter for unshielded, twisted-pair cable
US5825259A (en) * 1994-08-03 1998-10-20 Madge Networks Limited Electromagnetic interference isolator with common mode choke
US20010042632A1 (en) * 1998-11-19 2001-11-22 Advanced Filtering System Ltd Filter for wire and cable
US6778034B2 (en) * 2002-05-07 2004-08-17 G.M.W.T. (Global Micro Wire Technology) Ltd. EMI filters

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2779554A1 (fr) * 2013-03-15 2014-09-17 Intel Corporation Procédé, appareil et système pour atténuer l'interférence de fréquence radio à large bande
US9660734B2 (en) 2013-03-15 2017-05-23 Intel Corporation Method, apparatus, and system to mitigate broadband radio frequency interference
CN105929214A (zh) * 2016-04-14 2016-09-07 烽火通信科技股份有限公司 一种用于高速光眼图观测的触发信号产生装置及方法
US20230006865A1 (en) * 2020-05-12 2023-01-05 Saic Motor Corporation Limited Bidirectional isolated communication circuit and method for differential signal
US11677591B2 (en) * 2020-05-12 2023-06-13 Saic Motor Corporation Limited Bidirectional isolated communication circuit and method for differential signal

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