US3697896A - Signal transmission system - Google Patents

Signal transmission system Download PDF

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Publication number
US3697896A
US3697896A US114621A US3697896DA US3697896A US 3697896 A US3697896 A US 3697896A US 114621 A US114621 A US 114621A US 3697896D A US3697896D A US 3697896DA US 3697896 A US3697896 A US 3697896A
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United States
Prior art keywords
ground
shield
utilization system
signal
impedance
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Expired - Lifetime
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US114621A
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English (en)
Inventor
Miklos Sarkozi
Andras I Szabo
Perry J Hite
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Westinghouse Electric Corp
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Westinghouse Electric Corp
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Publication of US3697896A publication Critical patent/US3697896A/en
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/02—Details
    • H04B3/28—Reducing interference caused by currents induced in cable sheathing or armouring

Definitions

  • SIGNAL TRANSMISSION SYSTEM [54] Inventors: Miklos Sarkozi, Monroeville; An-
  • ABSTRACT A signal transmission system comprising a means for eliminating or substantially reducing noise in a circuit including a transmission line for transmitting signals from a signal source for example a transducer to a utilization circuit, wherein the transducer has a predetermined ground and the transmission line comprises a pair of insulated signal conductors surrounded by a conductive shield with an insulated, shield-current relief conductor extending longitudinally along the signal conductors and parallel thereto outside of the shield and closely adjacent thereto.
  • the shield relief conductor is grounded at one end to the transducer ground and means are provided at the other end for providing a connection to ground either through an intentional actual impedance or a stray impedance at the signal utilization circuit. This impedance may be of various types inherent in the utilization circuit or adapted to suit the utilization circuit.
  • This invention pertains generally to a signal transmission system noise minimizing circuitry and more particularly to a system for transmitting relatively low input signals from a grounded transducer to a distant utilizing circuit, with means for minimizing the effect of electromagnetic and other electrical potential noise interferences with the signal transmission.
  • a voltage e.g., a differential ground potential
  • a differential ground potential may exist between ground points of the transducer and at the utilization circuit. Connecting these ground points, as through ground connections of the shield at the two transmission line terminals, results in the flow of a differential ground loop current due to this differential ground potential.
  • This can produce a differential mode noise in the information signal conductors, both by inductive and capacitive coupling therewith.
  • the present invention provides a signal transmission system, including a shielded transmission line having at least two signal conductors connecting a signal source for example a transducer with a predetermined ground to a utilization system, with a shield-current relief conductor extending along the signal conductors parallel thereto and grounded at one end to the transducer ground with means for providing a connection to ground either through an actual or stray impedance at the other end thereof at the signal utilization system.
  • the signal conductors and the shield-current relief conductor are insulated conductors and the shield relief conductor is outside of the shield, parallel and closely adjacent thereto and minimizes and substantially inhibits the generation of differential mode noise in the shielded information signal conductors by providing a shield-current relief path which diverts the ground loop and other stray currents from the shield through a parallel conductive path outside of and insulated from the shield.
  • the shield relief conductor is connected directly to the converter guard, which, by its distributed capacitance, is coupled to the utilization system ground.
  • the shield relief conductor may be connected to ground at the utilization system end thereof through an impedance network and a third winding of a three winding transformer, the other two windings of which are respectively connected one between each of the two signal conductors of the transmission line and the input of the utilization system.
  • Each of the windings has the same number of turns and is wound and connected so that any common mode voltage induced in the signal conductor connected windings by current flow in the third winding will be opposed and equal to any common mode voltage induced in the signal conductors, thereby cancelling most of the common mode noise at the input to the utilization system.
  • the ground connection of the transformer third winding may also be through a network which inhibits the flow of dc current but permits the flow of ac currents. This combination ensures normal operations in cases where a large dc potential difference can exist between the transducer ground and the utilization device ground by inhibiting the flow of a dc current which could magnetically saturate the transformer.
  • FIG. 1 is a schematic diagram illustrating the general circuitry of a signal transmission system incorporating this invention
  • FIG. 2 is a schematic diagram illustrating the present invention in a system provided with a guarded analogto-digital converter, or similarly guarded device, at the input of the signal utilization circuit;
  • FIG. 3 is a schematic diagram illustrating the present invention in a system having a three winding commonmode noise cancelling transformer at the input to the signal utilization circuit;
  • FIG. 4 illustrates a cross section of one type transmission line for use in the present invention.
  • FIG. 5 illustrates a cross section of another suitable type transmission line for use in the present invention.
  • FIG. 1 illustrates circuitry applicable in carrying out the present invention, wherein a transducer forms the information signal source for the transmission system and includes a suitable signal generating source 11 connected across a pair of impedances, such as resistors 12 and 13, and the transducer output terminals 14 and 15.
  • the connecting junction point 16 between the resistors 12 and 13 has a predetermined connection 17 to ground for the transducer 10.
  • the transducer also may be shielded by an enclosing conductive guard 18, which also may be connected to the transducer ground 17 by a suitable connection 19.
  • a transmission line 20 is provided having a pair of signal conductors 21 and 22, respectively connected to transducer terminals 14 and 15.
  • the input of the utilization system 30 is of the balanced or differential type, for example having in its input a differential amplifier 32.
  • the system 30 includes a guard 33 for shielding against stray electromagnetic and electrostatic fields.
  • These signal conductors are individually insulated, as shown at 23 and 24, respectively, in both illustrative cross-sectional views, FIGS. 4 and 5, and are enclosed in a suitable electrically conductive shield 25 which at its source end is electrically connected to the source ground 17.
  • the term electrically connected refers to a connection that is capable of passing direct current.
  • the two conductors 21 and 22 are longitudinally twisted, as is conventional, in order to provide a substantially uniform exposure of these conductors to stray industrial and other environmental electromagnetic fields 26 along the transmission line.
  • the shield 25 may be formed by a braided wire mesh or by a conductive foil spirally wrapped around the conductors 21 and 22. In the latter case the effectiveness of the shield can be enhanced by a third conductor 27 which is uninsulated and extends along the signal conductors parallel thereto and in good electrical contact with the shield 25. As shown in FIG. 4, the bare conductor 27 may be on the outside of the shield 25; or, as shown in FIG.
  • the bare conductor 27 and thereby the shield 25 at one end thereof, such as shown at the transducer end (i.e., the source end) of the transmission line. This can conveniently be done by electrically connecting it to the transducer ground connection 17.
  • transducers often are spaced a considerable distance from the utilization circuit, and a consequent potential difference may exist between the system ground and the conductors of the cable at the utilization circuit.
  • This voltage difference is normally referred to as the common-mode voltage.
  • a common-mode potential is prevented from causing current flow in the transmission line shield which might induce noise voltages in the signal transmission conductors by the provi sion of a fourth transmission line conductor 28 which extends longitudinally along the signal conductors parallel thereto outside of the shield 25, closely adjacent to and parallel to the shield.
  • This fourth conductor 28 is individually insulated, as shown at 29, FIGS. 4 and 5, so that it has no electrical contact with the shield 25 or any of the other three conductors along the transmission line.
  • the conductor 28 is electrically connected to the transducer ground 17 at the transducer end of the line and is connected to ground through either an actual or a stray impedance Z at the utilization system.
  • Impedance Z may for example be stray impedance inherent in system 30 with or without intentionally added impedance.
  • the impedance 2 should impede dc and pass common mode frequencies. Thus, any tendency for current to flow through the shield 25 is relieved by the conductor 28 path which diverts such currents from the shield through this shield-current relief path.
  • Both the bare conductor 27 and the insulated shield relief conductor 28 may be twisted around the other conductors. In the FIG. 4 arrangement, both could be twisted around the outside of the shield 25; and in the FIG.
  • the three conductors 21, 22, and 27 could be twisted longitudinally around each other and enclosed by the shield 25, with the conductor 28 twisted longitudinally of the shielded conductor assembly.
  • a suitable insulating covering 31 encases all of the conductors and the shield.
  • FIG. 2 illustrates a specific application of the present invention, wherein the circuitry generally is the same as that previously described. It is here used in a signal transmission system in which the signals are supplied by the transmission line 20 to a floating guarded utilization system 30.
  • the signal conductors 21 and 22 are shown connected to the input of an analog-todigital converter 32 which forms the input to a utilization circuit.
  • the converter 32 is shielded by a guard 33 having a distributed or stray capacitance coupling 34 to ground at the utilization system.
  • a guard 33 having a distributed or stray capacitance coupling 34 to ground at the utilization system.
  • FIG. 3 illustrates a signal transmission system utilizing the present invention generally as previously described but using a special three-winding common mode noise trap transformer 40, of the type disclosed in the previously mentioned concurrently filed application Ser. No. 1 14,473 pending in 255.
  • This transformer does not per se form part of this invention.
  • the three winding transformer 40 is provided with windings having equal numbers of turns, and with two of the windings 41 and 42 connected one between each of the signal conductors 21 and 22 respectively,
  • the transformer windings 41 and 42 are connected in the system such that any common mode voltages induced therein by current through the third winding 42 will be opposed to common mode voltages which may appear at the terminals of signal conductors 21 and 22.
  • an insulated shield current relief conductor located externally of, adjacent to, and extending along the length of said shield, said relief conductor at the source end thereof being electrically connected to said source ground, and
  • said effective impedance comprises actual impedance made intentionally a part of the utilization system.
  • said effective impedance comprises stray impedance of the utilization system.
  • said signal utiliz tion s stem includes elect onic circuitr with a guard therezi round that 15 free of electncal corinection to ground at the utilization system, and the utilization system end of said relief conductor is electrically connected to said guard.
  • one of said windings being connected between an end of one of said signal conductors and an input terminal of said utilization system, a second of said windings being connected between an end of the other signal conductor and another inputter terminal of said utilization system, and the third of said windings being connected between the utilization system end of said shield relief conductor and ground at said utilization system.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
US114621A 1971-02-11 1971-02-11 Signal transmission system Expired - Lifetime US3697896A (en)

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US11462171A 1971-02-11 1971-02-11

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US (1) US3697896A (cg-RX-API-DMAC10.html)
FR (1) FR2126840A5 (cg-RX-API-DMAC10.html)

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4017845A (en) * 1975-06-16 1977-04-12 Fmc Corporation Circuitry for simultaneous transmission of signals and power
FR2672451A1 (fr) * 1991-01-31 1992-08-07 Pioneer Electronic Corp Circuit d'isolation de masse pour circuits electroniques.
US5181000A (en) * 1992-01-21 1993-01-19 Perfectionist Audio Components Inc. Digital interference filter for audio systems
US5208560A (en) * 1989-11-27 1993-05-04 Fujitsu Limited Signal transmission circuit
US5287008A (en) * 1990-07-31 1994-02-15 Tandberg Data A/S Electrostatic discharge noise suppression method and system for electronic devices
US5465013A (en) * 1993-07-12 1995-11-07 The Government Of The United States Of America As Represented By The Secretary Of The Department Of Health And Human Services Electric field shielding system for AC electrically powered device with a two-blade plug
US5467061A (en) * 1993-07-16 1995-11-14 Tut Systems, Inc. Flat cable to flat parallel wire cable
EP0739780A1 (en) * 1995-04-27 1996-10-30 Honda Giken Kogyo Kabushiki Kaisha Automobile multiplex communication system
US5765040A (en) * 1994-06-24 1998-06-09 Fujitsu Limited Disk subsystem using a pair of unidirectional control lines for exchanging control information in bit-serial between control device and plural disk units through up/down directions
US5850114A (en) * 1996-12-23 1998-12-15 Froidevaux; Jean-Claude Device for improving the quality of audio and/or video signals
US5970138A (en) * 1995-12-04 1999-10-19 Fujitsu Limited Terminal equipment for telecommunications and information processing
WO2003077266A1 (en) * 2002-03-05 2003-09-18 Whidden Robert H Method of transmitting electrical power
US6885258B2 (en) * 2000-05-17 2005-04-26 Nec Corporation Method and apparatus for reducing radiant noise energy by radiating noise energy from a quasi-ground into a signal wire
US20050164666A1 (en) * 2002-10-02 2005-07-28 Lang Jack A. Communication methods and apparatus
WO2008008091A3 (en) * 2006-07-07 2008-06-12 Technology Res Corp Interruption circuit with improved shield
US20100301965A1 (en) * 2007-03-04 2010-12-02 Rohde & Schwarz Gmbh & Co. Kg Waveguide System with Differential Waveguide
US8058879B1 (en) * 2009-01-06 2011-11-15 Atherton John C Voltage indicating coupling for metal conduit systems

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US955142A (en) * 1909-07-17 1910-04-19 Minor M Davis Device for preventing induction in electrical conductors.
GB423516A (en) * 1933-08-04 1935-02-04 Kolster Brandes Ltd Improvements in transmission networks for coupling an antenna to a radio receiving system
US2064227A (en) * 1931-02-25 1936-12-15 Rca Corp Radio frequency distribution system
US2280950A (en) * 1941-05-13 1942-04-28 Westinghouse Electric & Mfg Co Pilot wire system with means for neutralizing induced voltages
US2376101A (en) * 1942-04-01 1945-05-15 Ferris Instr Corp Electrical energy transmission
US2447168A (en) * 1942-05-12 1948-08-17 Telegraph Constr & Maintenance High-frequency electric conductors and cables
US2663752A (en) * 1950-03-10 1953-12-22 Bell Telephone Labor Inc Shielded electrical conductor with grounding strand
US3518577A (en) * 1969-07-25 1970-06-30 Baum Elektrophysik Gmbh Radiation protected cables
US3534146A (en) * 1968-10-24 1970-10-13 Teletype Corp Double shielded rfi enclosure

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US955142A (en) * 1909-07-17 1910-04-19 Minor M Davis Device for preventing induction in electrical conductors.
US2064227A (en) * 1931-02-25 1936-12-15 Rca Corp Radio frequency distribution system
GB423516A (en) * 1933-08-04 1935-02-04 Kolster Brandes Ltd Improvements in transmission networks for coupling an antenna to a radio receiving system
US2280950A (en) * 1941-05-13 1942-04-28 Westinghouse Electric & Mfg Co Pilot wire system with means for neutralizing induced voltages
US2376101A (en) * 1942-04-01 1945-05-15 Ferris Instr Corp Electrical energy transmission
US2447168A (en) * 1942-05-12 1948-08-17 Telegraph Constr & Maintenance High-frequency electric conductors and cables
US2663752A (en) * 1950-03-10 1953-12-22 Bell Telephone Labor Inc Shielded electrical conductor with grounding strand
US3534146A (en) * 1968-10-24 1970-10-13 Teletype Corp Double shielded rfi enclosure
US3518577A (en) * 1969-07-25 1970-06-30 Baum Elektrophysik Gmbh Radiation protected cables

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4017845A (en) * 1975-06-16 1977-04-12 Fmc Corporation Circuitry for simultaneous transmission of signals and power
US5208560A (en) * 1989-11-27 1993-05-04 Fujitsu Limited Signal transmission circuit
US5287008A (en) * 1990-07-31 1994-02-15 Tandberg Data A/S Electrostatic discharge noise suppression method and system for electronic devices
FR2672451A1 (fr) * 1991-01-31 1992-08-07 Pioneer Electronic Corp Circuit d'isolation de masse pour circuits electroniques.
US5181000A (en) * 1992-01-21 1993-01-19 Perfectionist Audio Components Inc. Digital interference filter for audio systems
US5465013A (en) * 1993-07-12 1995-11-07 The Government Of The United States Of America As Represented By The Secretary Of The Department Of Health And Human Services Electric field shielding system for AC electrically powered device with a two-blade plug
US5467061A (en) * 1993-07-16 1995-11-14 Tut Systems, Inc. Flat cable to flat parallel wire cable
US5765040A (en) * 1994-06-24 1998-06-09 Fujitsu Limited Disk subsystem using a pair of unidirectional control lines for exchanging control information in bit-serial between control device and plural disk units through up/down directions
US5648688A (en) * 1995-04-27 1997-07-15 Honda Giken Kogyo Kabushiki Kaisha Automobile multiplex communication wiring structure including shield
EP0739780A1 (en) * 1995-04-27 1996-10-30 Honda Giken Kogyo Kabushiki Kaisha Automobile multiplex communication system
US5970138A (en) * 1995-12-04 1999-10-19 Fujitsu Limited Terminal equipment for telecommunications and information processing
US5850114A (en) * 1996-12-23 1998-12-15 Froidevaux; Jean-Claude Device for improving the quality of audio and/or video signals
US6885258B2 (en) * 2000-05-17 2005-04-26 Nec Corporation Method and apparatus for reducing radiant noise energy by radiating noise energy from a quasi-ground into a signal wire
WO2003077266A1 (en) * 2002-03-05 2003-09-18 Whidden Robert H Method of transmitting electrical power
US20050164666A1 (en) * 2002-10-02 2005-07-28 Lang Jack A. Communication methods and apparatus
WO2008008091A3 (en) * 2006-07-07 2008-06-12 Technology Res Corp Interruption circuit with improved shield
US20100301965A1 (en) * 2007-03-04 2010-12-02 Rohde & Schwarz Gmbh & Co. Kg Waveguide System with Differential Waveguide
US8076989B2 (en) * 2007-04-03 2011-12-13 Rohde & Schwarz Gmbh & Co. Kg Differential waveguide system connected to front and rear network elements
US8058879B1 (en) * 2009-01-06 2011-11-15 Atherton John C Voltage indicating coupling for metal conduit systems

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FR2126840A5 (cg-RX-API-DMAC10.html) 1972-10-06

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