US1930732A - Means for the elimination of distortion in telephone lines - Google Patents

Means for the elimination of distortion in telephone lines Download PDF

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Publication number
US1930732A
US1930732A US405217A US40521729A US1930732A US 1930732 A US1930732 A US 1930732A US 405217 A US405217 A US 405217A US 40521729 A US40521729 A US 40521729A US 1930732 A US1930732 A US 1930732A
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US
United States
Prior art keywords
line
amplifier
damping
valve
voltage
Prior art date
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Expired - Lifetime
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US405217A
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English (en)
Inventor
Ves Mauritz
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.)
Telefonaktiebolaget LM Ericsson AB
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Telefonaktiebolaget LM Ericsson AB
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Application filed by Telefonaktiebolaget LM Ericsson AB filed Critical Telefonaktiebolaget LM Ericsson AB
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Publication of US1930732A publication Critical patent/US1930732A/en
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/02—Details
    • H04B3/04—Control of transmission; Equalising
    • H04B3/06—Control of transmission; Equalising by the transmitted signal
    • H04B3/08—Control of transmission; Equalising by the transmitted signal in negative-feedback path of line amplifier

Definitions

  • the problem of establishing distortionless transmission of speech currents is solved principally in a quite diiierent manner than that used in said known arrangeinent, said inconvenience being then completely eliminated and besides a practically exact compensation of the distortion attained.
  • the invention is based upon the fact that in a pupinized cable ti e characteristic impedance and darnping vary according to the same function or" the frequency. Said property of such lines is now made use of by including amplifiers as telephone repeaters in the line in v -ich amplifiers the reaction of the anode voltage upon the grid voltage is eliminated by the retranaer of a compensating voltage from the anode circuit to the grid circuit in a manner known per se in modulators (Swedis Patent No.
  • Figure l is a circuit diagram of the arrangement according to one embodiment of the invention.
  • Figure 2 shows a modified embodiment having several amplifying valves in each telephone repeater on the line.
  • Fig. 3 shows an arrangement according to the invention in a pupinized line composed of a number of line sections.
  • the invention may be applied both in twowire and four-wire amplifiers.
  • FIG l, 1 and 1' represent two line sections united by means of a telephone amplifier each of which sections is loaded by Pupin coils l0 and in the usual manner terminates in a line balance 2 or 2 espectively a differential repeating coil 3 and 3' respectively being interconnected between the'line and the line balance.
  • the secondary Winding of said repeating coil is conn cted to the input transformer 4 and 4 respectively of a valve amplifier U and U respectively each comprising a three-electrode valve 5.
  • Each of the amplifiers U and U together with its appertaining parts is surrounded on the drawing by a rectangle indicated by dotted lines.
  • T -e output transformer of the valve is provided with three windings i. e.
  • the winding 8 or 8 respectively has for its purpose to retransfer a compensating voltage from the anode circuit to the grid which voltage is adapted to exactly neutralize the reaction of 8 and 8 respectively to the grid from the anode 110 circuit.
  • ZL L+ valve will in other words operate as a compounded dynamo having constant current.
  • the output voltage of the valve will thus at various frequencies be proportional to the absolute value of the characteristic impedance on the output side, and if new this impedance varies with the frequency in the same manner as does the damping of the line, the output voltage will obviously be proportional to the line damping at the same frequencies. Those frequencies which are most subjected to damping in the line section in front of the amplifier will thus obtain the highest amplification.
  • the line distortion is, however, only partially compensated by the above described arrangement alone.
  • the output voltage of the amplifier for the different frequencies is directly proportional to B1 where [3 is the damping coefficient of the line and lthe length of the line section in question, the damping in the line section in front of the amplifier conforms, on the V2 the voltage on the primary side of the input transformer, and R1 the internal resistance of the amplifying valve.
  • a designates as before the amplification ratio of the valve.
  • the characteristic impedance Z of the line and the damping coefficient 5 vary as above mentioned according to one and the same function of the angular frequency w and are .put side one may evidently put where l is the ratio of the input transformer 4,
  • Figure 2 shows an arrangement in connection with a four-wire amplifier by means of which'arrangement one'inay'be independent of such a fixed station distance.
  • the numerals 9 and 9' represent the ends of the line for instance apupinized cable, in which is inserted a repeater for the one transmission direction comprising two valves Ua and Us each of which together with its appertaining parts is surrounded in Figure 2 by a rectangle indicated by dotted lines.
  • the incoming line 9 is connected to the input side of a valve Us. arranged in the same manner as the valve U in Fig.
  • the output side of said valve Ua is connected to an artificial line AL the characteristic impedance of which varies with the frequency substantially in the same manner as does the damping of the line 9 but which, on the other hand, is practically free from damping.
  • the artificial line in question consists of two mutually parallel connected impedances the one of which consists of a condenser l3.and the other of a resistance 14 in series with an inductance 16 connected in parallel with the condenser 15.
  • the other end of the artificial line is connected to the input side of the second valve Us which is equal to Ua and the output side of which is connected to the outgoing line section 9.
  • Each of the two output transformers l2 and 19 are inconformity with the output transformer 6, '7, 8 in Figure 1 provided'with a compensating winding 8 to retransfer compensating potential to the grid in above described manner.
  • the circuit arrangement according to Figure 2 represents thus a combination of two amplifier units separated by a line section free of damping.
  • the artificial line AL has the same characteristic as the natural line the incoming oscillations is in the first valve Ua subjected to an amplification which, as regards all of the incoming frequencies, nearly compensates the damping for a line distance of the length Ln.
  • the line section in front of the amplifier station may thus in this case be of the double length 2Ln in comparison with that in the arrangement having only one amplifying valve.
  • the amplifier station may be composed by three or more amplifying units in sequence and mutually separated by artificial lines constituting reproductions free of damping of a line section of the length Ln. Distortionless transmission may thus be established in line sections of the length Ln, 2Ln, 3Ln etc.
  • the arrangement may, however, be completely independent of the calculated unit length Ln and the distance between the amplifier stations may then be selected solely in regard to the geographic conditions. This is rendered possible simply thereby that the number of amplifier valves connected in sequence in the amplifier station is chosen in such a manner that the amplifier station by itself compensates the damping of the number of whole unit lengths Ln which just eX- ceeds the length of the next line distance, be-
  • an artificial line d consisting of series inductances and shunt capacities and having the same characteristic impedance .as the line and a damping which is smaller than Z Neper and so chosen that the sum of the dampings of the line and the artificial line (1 corresponds to a number of whole unit lengths Ln. It may be assumed .for instance that the length Z of the line is equal to l, 8 unit length and that accordingly the damping of the artificial line d is 0,2 Neper.
  • the valve amplifier may be of the kind described in Fig. 2 comprising two unit valves Us and Us separated from one another by an artificial line AL having the same 7 characteristic impedance as the line.
  • An arrangement for eliminating distortion in a transmission line comprising in combination, a valve amplifier, means compensating substantially the reaction of the anode voltage of the valve amplifier .upon its grid voltage, and means causing the output impedance of the valve amplifier to vary with the frequency substantially in the same manner as does the damping of the transmission line.
  • An arrangement for eliminating distortion in a loaded transmission line, the characteristic impedance and damping of which vary substantially according to the same function of the frequency comprising in combination a valve amplifier inserted between consecutive sections of said line, and means compensating substantially the reaction of the anode voltage of the valve amplifier upon its grid voltage.
  • An arrangement for eliminating distortion in a loaded transmission line comprising in combination a valve amplifier inserted between consecutive sections of said line, means compensating substantially the reaction of the anode voltage of the valve amplifier upon its grid voltage, and means causing the characteristic impedance on the output side and the damping of the line to vary substantially according to the same function of the-frequency.
  • An arrangement for eliminating distortion in a transmission line comprising in combination, a valve amplifier, a feed back connection for retransferring a compensating voltage from the anode circuit to the grid circuit of the valve amplifier so as to eliminate substantially the re-; action of the anode voltage upon the grid voltage, and means causing the output impedance of the valve amplifier to vary with the frequency substantially in the same manner as does the damping of the transmission line.
  • An arrangement for eliminating distortion in a transmission line comprising in combination, a valve amplifier, a feed back connection adapted to retransfer, independently of the frequency, a constant fraction of the anode potential substantially eliminating the reaction of the anode voltage upon the grid voltage, and means causing the output impedance of the valve amplifier to vary with the frequency substantially in the same manner as does the damping of the transmission line.
  • valve and the ratios of transformation l and ,uz of the input and output transformer respectively, counted in the direction of the propagation of the oscillations are so selected in relation to the line characteristic Z0 at low frequencies that an amplifier composed of a number of lvalves, means for compensating.substantially the reaction of the anode voltage upon the grid voltage in each of said valves, an artificial line inserted between each two consecutive amplifiers said artificial line being nearly free of damping and having a characteristic impedance varying with the frequency substantially in the same manner as thus the damping of the line, and means causing the output impedance of the amplifier to vary with the frequency substantially in the same manner as does the damping of the line.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Amplifiers (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
  • Microwave Amplifiers (AREA)
US405217A 1928-11-09 1929-11-06 Means for the elimination of distortion in telephone lines Expired - Lifetime US1930732A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
SE338352X 1928-11-09

Publications (1)

Publication Number Publication Date
US1930732A true US1930732A (en) 1933-10-17

Family

ID=20308300

Family Applications (1)

Application Number Title Priority Date Filing Date
US405217A Expired - Lifetime US1930732A (en) 1928-11-09 1929-11-06 Means for the elimination of distortion in telephone lines

Country Status (5)

Country Link
US (1) US1930732A (enrdf_load_stackoverflow)
DE (1) DE597401C (enrdf_load_stackoverflow)
FR (1) FR684558A (enrdf_load_stackoverflow)
GB (1) GB338352A (enrdf_load_stackoverflow)
NL (1) NL28756C (enrdf_load_stackoverflow)

Also Published As

Publication number Publication date
FR684558A (fr) 1930-06-27
NL28756C (enrdf_load_stackoverflow)
GB338352A (en) 1930-11-20
DE597401C (de) 1934-05-24

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