US1815976A - Coupling between carrier and transmission lines - Google Patents

Coupling between carrier and transmission lines Download PDF

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Publication number
US1815976A
US1815976A US145899A US14589926A US1815976A US 1815976 A US1815976 A US 1815976A US 145899 A US145899 A US 145899A US 14589926 A US14589926 A US 14589926A US 1815976 A US1815976 A US 1815976A
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United States
Prior art keywords
coupling
carrier
ground
impedance
capacity
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Expired - Lifetime
Application number
US145899A
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English (en)
Inventor
Estill I Green
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
AT&T Corp
Original Assignee
American Telephone and Telegraph Co Inc
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Publication date
Application filed by American Telephone and Telegraph Co Inc filed Critical American Telephone and Telegraph Co Inc
Priority to US145899A priority Critical patent/US1815976A/en
Application granted granted Critical
Publication of US1815976A publication Critical patent/US1815976A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/54—Systems for transmission via power distribution lines
    • H04B3/56—Circuits for coupling, blocking, or by-passing of signals

Definitions

  • This invention relates to transmission lines and more particularly to arrangements for improving the efliciency of coupling between carrier apparatus and transmission 5 lines.
  • the arrangements of the invention are particularly applicable to cases where it is impossible or undesirable to associate carrier apparatus directly with the line circuit over which the carrier transmission is accomplished, and where some form of coupling device such as a loop or antenna must therefore be employed. Such cases frequently arise in connection with power line carrier systems, in many of which a coupling antenna or loop is employed in order to separate the carrier apparatus from the high voltage on the power lines.
  • a further field of application for the arrangements of the invention may be in connection with carrier systems for communication with moving vehicles, such as trains, where it is impossible to connect the carrier apparatus directly to the transmission line.
  • FIG. 1 is shown a power line having carrier apparatus cow led thereto.
  • Fig. 2 is a schematic equivaent of Fig. 1.
  • Fig. 3 is shown carrier apparatus coupled to a power line with the arrangements of this invention.
  • Figs. 4 and 5 illustrate modifications of the invention. Similar reference characters have been utilized to denote like parts in all of the figures.
  • a common method of coupling carrier apparatus to a power line is shown schematically in Fig. 1.
  • the carrier apparatus is connected through a suitable transformer T to a coupling wire or antenna CC, whereby the carrier current may be transmitted to the power line LL by electrostatic induction.
  • the power line LL which will ordinarily consist of several wires, is shown as terminating at the sending end in the impedance to ground, shown as Z, of the transformer which supplies power to the wires LL.
  • Z the impedance to ground
  • the power line may be assumed for a long line at carrier frequencies to be terminated in the characteristic impedance to ground Z For practical purposes, this characteristic impedance Z becomes at carrier frequencies a pure resistance.
  • Fig. 2 is shown the approximate equivalent of the arrangements shown in Fig. 1.
  • the impedance looking back into the transformer T is shown as consisting of the inductance L and resistance R.
  • the capacity of the coupling wire to the power wires is shown as C
  • the capacity of the coupling wire to ground is shown as C
  • the power transformer impedance to ground Z is shown as a capacity G with a loss, ordinarily small, represented by 7.
  • the efliciency is the ratio of the power utilized in Z to the total power delivered to the circuit. Neglecting for the moment the power transformer capacity and loss, it can be shown that to obtain maximum efiiciency the following three conditions should be fulfilled.
  • R Z (1) where R is the resistance component looking into the transformer T, and Z is the characteristic impedance of the power wire to ground.
  • R is the resistance component looking into the transformer T
  • Z is the characteristic impedance of the power wire to ground.
  • the third condition for maximum efliciency is that an additional inductance L (shown in dottedlines) should be connected in parallel with C and that L should be chosen so that which involves the use of means not shown in Fig. 1 to obtain an anti-resonant circuit be-' tween the coupling wire and ground, is one of the primary objects of this invention.
  • the power transformer capacity which was neglected may have some slight effect on the validity of the first two conditions, but can have none of the third. From a physical standpoint the third condition amounts to giving the coupling wire a very high impedance to ground so that most of the energy will choose the low impedance path to the power line.
  • This high impedance to ground is obtained by loading the coupling wire with one or more inductance elements, such as L and L as shown in Fig.3.
  • two loading networks, such as K and K would be congive two difi'erent points of anti resonance with the wire capacity.
  • FIG. 5 Another method of coupling, in which the coupling wire CC is grounded at the dis, tant end, is shown in Fig. 5.; This is obviously a type of electromagnetic induction, in contrast to the electrostatic method heretofore illustrated.
  • the effect of the capacity of the coupling wire to ground will be to shunt off the current, and the efiiciency of the arrangement will be'improved by raising the impedance to, ground so that all the current enters the ground at O.
  • the loading devices L and L Coupling devices which utilize a combination of electrostatic and electromagnetic coupling may be similarly loaded.
  • the same general plan of loading may be from those described.
  • a metallic loop is used instead of a ground wire loop the capacity of the loop will still introduce loss which can be eliminated by loading.
  • the coupling is made with a metallic circuit on the transmission line this circuit will have considerable capacity to ground, so that it is still advantageous to eliminate the effect of the capacity of the coupling device to ground.
  • the loading is entirely independent of other expedients, such as tuning the coupling device, matching impedance, etc.,' which are also employed to improve the efliciency of the system for a particular fre-' quency or frequencies.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Train Traffic Observation, Control, And Security (AREA)
  • Near-Field Transmission Systems (AREA)
US145899A 1926-11-02 1926-11-02 Coupling between carrier and transmission lines Expired - Lifetime US1815976A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US145899A US1815976A (en) 1926-11-02 1926-11-02 Coupling between carrier and transmission lines

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US145899A US1815976A (en) 1926-11-02 1926-11-02 Coupling between carrier and transmission lines
GB13166/27A GB295669A (en) 1927-05-17 1927-05-17 An arrangement for coupling carrier-wave signalling apparatus to a transmission line

Publications (1)

Publication Number Publication Date
US1815976A true US1815976A (en) 1931-07-28

Family

ID=10018063

Family Applications (1)

Application Number Title Priority Date Filing Date
US145899A Expired - Lifetime US1815976A (en) 1926-11-02 1926-11-02 Coupling between carrier and transmission lines

Country Status (4)

Country Link
US (1) US1815976A (en(2012))
BE (1) BE343072A (en(2012))
FR (1) FR635967A (en(2012))
GB (1) GB295669A (en(2012))

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2442851A (en) * 1940-08-03 1948-06-08 Farnsworth Res Corp Traffic signaling system
US2531498A (en) * 1947-02-20 1950-11-28 Union Switch & Signal Co Wayside station line coupling means for train communication systems
US2591022A (en) * 1947-12-13 1952-04-01 Westinghouse Air Brake Co Inductive train communication system

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2442851A (en) * 1940-08-03 1948-06-08 Farnsworth Res Corp Traffic signaling system
US2531498A (en) * 1947-02-20 1950-11-28 Union Switch & Signal Co Wayside station line coupling means for train communication systems
US2591022A (en) * 1947-12-13 1952-04-01 Westinghouse Air Brake Co Inductive train communication system

Also Published As

Publication number Publication date
FR635967A (fr) 1928-03-29
BE343072A (en(2012))
GB295669A (en) 1928-08-17

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