US1772558A - Loading system - Google Patents

Loading system Download PDF

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Publication number
US1772558A
US1772558A US198459A US19845927A US1772558A US 1772558 A US1772558 A US 1772558A US 198459 A US198459 A US 198459A US 19845927 A US19845927 A US 19845927A US 1772558 A US1772558 A US 1772558A
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United States
Prior art keywords
loading
line
frequency
impedance
loaded
Prior art date
Legal status (The legal status 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 status listed.)
Expired - Lifetime
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US198459A
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English (en)
Inventor
Timothy E Shea
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AT&T Corp
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Bell Telephone Laboratories Inc
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Filing date
Publication date
Priority to BE351381D priority Critical patent/BE351381A/xx
Application filed by Bell Telephone Laboratories Inc filed Critical Bell Telephone Laboratories Inc
Priority to US198459A priority patent/US1772558A/en
Priority to GB14377/28A priority patent/GB292096A/en
Priority to FR655498D priority patent/FR655498A/fr
Application granted granted Critical
Publication of US1772558A publication Critical patent/US1772558A/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
    • H04B3/02—Details
    • H04B3/26—Improving frequency characteristic by the use of loading coils

Definitions

  • This invention relatesto loading systems for telephone lines and theflike,v and has for lan object to improve :the impedance characteristics of loaded lines.l Y. t
  • this invention comprises an-openl wireline or cable periodically loaded means of loadi nnits 'comprising inductancefcoilsand ,con ensers connectedin parallel with eachother in each side of the line.
  • These loadingv units maybe distributed along the lineat approximately tlie Sfarnel distances apartfas'lare thefllo'adin coils in linesloaded by the" ⁇ Pupinfmetho Ina modifiedvform,uthis ⁇ invention prises acompositefiloaded vsystemuin ⁇ which Nhenterniinatediinid-coil; such a system has a characteristic impedance whichis a sub?" stantially constantresistance throughout the transmission rangefff 9 the sectionv'or sections at eachterminal are loaded Vaccording"to the-method of this illvention ⁇ ⁇ as-abovej described i the intermediate sections are loadedy according to the Y ordinary-metliod,iieiythePiipin method, ⁇
  • Fig. 2i1l1 istrates the equivalent network of; Fig ⁇ .1 combined with the u Sllaltype'offload-- infrcoils and terminated mid-coil; 'f
  • Cigy shows'schematically a portion i withr the loading transmission line loaded units of this invention; l t d Figrfl shows a network equivalent toa sin-f ⁇ gle,l lnid-coil terminated section ofV the l present invention; and g 6 [hows schematicallya composite typeof loaded, linesot ⁇ this inventions l "It e sletion ofcable crepe, wire line which the series resistance. ⁇ and shunt Capacity are the controlling factors, be represented by y the equivalent T networkshown in. Fg-V 1.
  • R- is thetotalf seriesiresistance; ofthe section and S and fC are respectively Lthe length ofy the eablesection andthe ,Capacity for eaclilnnit oflen th,so thattlieprodnct SC "ifsthe totalcapa'city, such a section loaded inthe usiial. manner inay be represented lby' tlienetwork shown in Fig. ⁇ 2, where Lv'isvjthe ⁇ totahinductanceof theloading coil.
  • the Cut-off frequency gf thelcded Sectin is pproxmatelyggive fe-M/gf@ t ,e thel ilnpedance-.fifqeeiei characteristics of cables loaded .in the ordi- Vnary'manner and in accordancel vviththe 70 i sov full coil bein installed at the end of the first complete loa ing section.
  • the network of Fig. 2 represents a mid-coil terminated section.
  • Curve B represents the im nce-,frequency characteristic of a cab e loaded in the ordinary manner (Pupin method) with mid-coil termination, and as shown, the impedance decreases with increasing'frequency, .approaching zero at the cutolf frequency which for this case is about 2800 cycles per second.
  • Curve A shows the impatience-frequency characteristic for the same type of cable with mid-section termination, and, as shown, in this case the impedance increases rwith increasing frequency, ap-V l proaching infinity at the cut-oil" frequency.
  • Curve C is the impedance-frequency charac-V teristic of a non-loaded openwire line of approximately thesame nominal impedance. t is therefore obvious that if the ordinary type of loading is employed and the loaded cable having either termination is oined directly to a non-loaded open wire line, large reflections will occur at the junction due to this difference in the impedances. y
  • Fig. 3 vshows a line or cable loaded in accordance with the method of this invention in which anti-resonant networks, each of which consists of an inductance coil connected in parallel with a condenser, replace the ordinary type of loading coils.
  • Fig. 4 shows a T type network equivalent to a single midcoil terminated section of the system of Fig. 3,.
  • This type of loading unit like the usual type, has a low pass characteristic, and its cut-off frequency is approximately ffm/m .(4)
  • the characteristic impedance of a cable terminated at mid-load (mid-coil) Hwith the anti-resonant type of loading is, however, affected by the series condensers and 1s approximately wherefoo', the anti-resonantfrequency of the loading network, is
  • curve D shows the im edancefrequency'characteristic for a loade line of the type shown inFig. 3 in which the anti-reso# nantfrequency is 1.25 times the cutoi frequcncy,t at is, Y
  • the cut-off frequency is somewhat lower than for the ordinary type of loading, as can be seen b' comparing Equation (4) with Equation l), the amount of reduction of the kcut-off frequen depend'm on thechoice of anti-,resonant equency o the loading networks.
  • the anti-resonant type of loading gives attenuation and phase characteristics which are nearly' the same as for the ordinarytype of loading, except at frequencies near the cut-off frequency.
  • the difference kin transmission characteristics may be roughly expressed bysaying that the Cut-.off frequency .is somewhat reduced as Yau misses compared with the erdinary type loading, ai-
  • nary type of loading andthe same ,values of loading coil inductance and the 'samefspacingy are chosen as in the case ofk ordinary loading' 540() cycles and the impedance yof the cable would be'practically the saine as that ofthe vopen yWire line throughout theentire eii'ective transmission range. Also the attenua- ⁇ tion and phase shiftA characteristics would be practically identical with those ofthe cable loaded in the ordinary manner. f
  • Fig'. 6 shows a composite type' of loaded line in which some ofthe sections are loaded ⁇ vvitli anti-resonantnetworks and some are loaded in the ordinary manner. This arrangement y is possible because the mid-sectioncharacter# istic impedance with either type of loading may be made very closely the same by choos ingthe same cut-olf frequencies and nominal impedances.
  • a "ave transmission system comprising a plurality of sectionsV of'line, inductive means 'for periodically'loadin one of said sections in accordance with the upinsystem, and loading networks each comprisingin'-v ductance and capacity elements connected "in parallel with one another for periodically loadinganother of said'sections' Yfor substantially the samerange of frequ'enciesl 2.
  • AWave transmission system comprising intermediate andrterminal sections of line, inductive means for periodically,loadingsaid intermediate 'section according'fto the Pupiln method, and loading 'networkseach comprisf ing-inductance and capacity elements co'n- ⁇ nected'in parallel with each ⁇ otherfor pe riodically loading'one of said terminal sections for substantially the sanie'range'of frequencies.
  • a Wave transmission system according* to the next preceding claim and a loadinglnet- Work for4 terminating said. terminal section and comprising inductance and capacity ele- ⁇ ments connected nparallel with each other and each having van impedance which is; a fraction of the impedancel of the correspond ing element of' said other loading networks.
  • a Wave transmission system comprising intermediate vand terminal sections of line,-
  • inductive meansV for periodically loading said* intermediate section accordingto' the' Pupin method
  • 'and loading networks' each comprising inductance and capacity elements ifo connectedin parallelY with each other forpe'- ricdicll'y leading one v01E said terminal sections for substantially' thesarne rangeof frequencies, said elements being so proper@ tioned asto givesaid 'terminal section substantially the sa'mecut-oi freq'uencyfl as said intermediated section and 4the Aimpe'dance' of the elements of the terminating network being substantially one-half the impedance' of the correspondingl elements of the other net'- works. ⁇
  • networks for waves of a plurality of frequencies, which consists in inserting at regular intervals along the line and in series therewith, networks comprising inductance and capacitance in parallel wit-h each other, and assigning to said networks such values as to cause said networks to become anti-resonant at a frequency which is substantially greater than loading cut-off frequency and greater than any frequency to be transmitted by said line, whereby the line is givena substantially constant impedance throughout a large portion ofthe transmission frequency range.
  • a method of loading a transmission line for waves of a plurality of frequencies which consists of inserting at regular intervals alongthe line and in series therewith, networks comprising inductance and capacitance in parallel with each other, and assigning to said networks-such values as to make said networks anti-resonant at a frequency which is substantially 25% greater than the loading cut-off frequency, whereby the line is given a substantially constant impedance throughout a large portion of the transmission frequency range.
  • a loading system' comprising line-conductors and loading units connected-in series with each of said conductors for loading said conductors for waves of a plurality of frequencies, each unit including an inductance and a capacity element of such values as to cause the units to'become anti-resonant at a frequency which i is substantially greater than the loading cut-off frequency and greater than any frequency to betransmitted over said line conductors whereby the line is given a substantially constant impedance throughout a large portion of the transmission frequency range.
  • a loading system comprising a pair of line conductors and loading units connected in series with each of said conductors for loading said conductors for waves of a plurality of frequencies, said units being-disposed at regular intervals along the conductors, each unit including an inductance andra capacity element of such values as to cause the units toibecome anti-resonant at aA frequency which is substantially greater than the loading cut-off frequency and greater than any frequency to be transmitted over said line conductors, whereby the line is given a substantially constant impedance throughout a large portion of the transmission range.
  • a wave transmission system comprising a line, a plurality of loading networks periodically distributed ⁇ along said line for loadingsaid line for waves of a plurality of frequencies, each of said networks comprising an inductance element and a capacity element connected in parallel with each other, and assigned such values as to same fraction of the impedance of the corresponding elements of the other loadin networks, whereby the yline is given a su antially-constant impedance throughout a large portion of the transmission frequency range.
  • a loading system arranged in sections, each of which comprises line conductors and loading units ⁇ connected in series with said conductors, each unit including an inductance and a capacity element of such values as to give each section a maximum value of attenuation at a frequency above the cut-olf frequency and a substantial amount of ⁇ attenuation for all frequencies higher than the frequency of maximum attenuation throughout a wide range of frequencies.
  • a loading system comprising line conductors and networks for loading said conductors fora band of telephone frequencies, connected in series with each of said conductors, each network including an inductance and a capacity element of such values as to cause the networks to become antiresonant at a frequency which is substantially greater than the loading cut-off frequency and above the telephone frequency range, ⁇ whereby the line is given a substantially constant impedance throughout a large portion of said band.
  • a loading system comprising a transmission line and recurrent networks inserted at regular intervals along said line and in series therewith to load said line for a plurality of frequencies-to be transmitted, said networks comprising the sole loading elements in said line, each network comprising elements including an inductance and a capacitance in parallelwith eac-h other of such values as to cause the network to become antiresonant at a frequency which is substantially greater than the loading cut-off frequency, each network having the same combination of elements and with the same values as every other network in the line, whereby the line is given a substantially constant impedance throughout a large portion of the transmis- ⁇ sion range.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Coils Or Transformers For Communication (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
US198459A 1927-06-13 1927-06-13 Loading system Expired - Lifetime US1772558A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
BE351381D BE351381A (enrdf_load_stackoverflow) 1927-06-13
US198459A US1772558A (en) 1927-06-13 1927-06-13 Loading system
GB14377/28A GB292096A (en) 1927-06-13 1928-05-16 Improvements in loading systems for telephone lines or the like
FR655498D FR655498A (fr) 1927-06-13 1928-06-08 Système de pupinisation pour lignes électriques

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US198459A US1772558A (en) 1927-06-13 1927-06-13 Loading system

Publications (1)

Publication Number Publication Date
US1772558A true US1772558A (en) 1930-08-12

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US198459A Expired - Lifetime US1772558A (en) 1927-06-13 1927-06-13 Loading system

Country Status (4)

Country Link
US (1) US1772558A (enrdf_load_stackoverflow)
BE (1) BE351381A (enrdf_load_stackoverflow)
FR (1) FR655498A (enrdf_load_stackoverflow)
GB (1) GB292096A (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3496292A (en) * 1965-08-31 1970-02-17 Eric Waldelius Impedance correcting coil-loaded circuits

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3496292A (en) * 1965-08-31 1970-02-17 Eric Waldelius Impedance correcting coil-loaded circuits

Also Published As

Publication number Publication date
GB292096A (en) 1929-06-20
BE351381A (enrdf_load_stackoverflow)
FR655498A (fr) 1929-04-19

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