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US2140492A - Distortion correction in wave transmission - Google Patents

Distortion correction in wave transmission Download PDF

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Publication number
US2140492A
US2140492A US158294A US15829437A US2140492A US 2140492 A US2140492 A US 2140492A US 158294 A US158294 A US 158294A US 15829437 A US15829437 A US 15829437A US 2140492 A US2140492 A US 2140492A
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US
United States
Prior art keywords
phase
modulation
repeater
repeaters
amplifier
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
Application number
US158294A
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English (en)
Inventor
Harold S Black
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
Bell Telephone Laboratories Inc
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
Priority to BE429535D priority Critical patent/BE429535A/xx
Application filed by Bell Telephone Laboratories Inc filed Critical Bell Telephone Laboratories Inc
Priority to US158296A priority patent/US2140900A/en
Priority to US158294A priority patent/US2140492A/en
Priority to CH239303D priority patent/CH239303A/de
Priority to FR841940D priority patent/FR841940A/fr
Priority to GB23601/38A priority patent/GB517601A/en
Application granted granted Critical
Publication of US2140492A publication Critical patent/US2140492A/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
    • H04B3/04—Control of transmission; Equalising

Definitions

  • a more general purpose .of this invention is to provide means for reducing the interchannel modulation which would otherwise be present in this type of system. As will be pointed out later, the results are accomplished by bringing in certain phase frequency relationships in each repeater section by which the modulation voltage product will increase less rapidly than the number of repeaters.
  • Fig. 1 isa schematic representation of a transmission line with a large number of repeaters in tandem and which at the same time incorporates the features of my invention
  • Fig-2 is a modification of the circuit of Fig. 1;
  • Fig. 3 is a detailed circuit of one of the repeater stations providing automatic compensation for temperature or other variations in the repeater sections;
  • Fig. 4 is a detail relating to Fig. 3;
  • Fig. 5 is a furthermodification of Fig. 1;
  • Fig. 6 is a phase frequency curve used to illustrate my invention.
  • the resistance line in the previous example is replaced by a telephone cable for which the velocity of transmission of a wave is the same for all frequencies, then there will be a time delay as one passes over a repeater cable section. but the wave shape at the input of one repeater is identically the same as the wave shape at the output of the previous repeater.
  • Such a condition is quite closely approximated over a Wide frequency band in the so-called coaxial cable and it will be apparent from what has been said heretofore that by suitable poling at the successive repeaters it is possible to balance out even order terms but the odd order modulation voltage terms are those of a single amplifier multiplied by the number of amplifiers.
  • the actual phase shift, expressed in radians, as one passes over a repeater section is proportional to the frequency and would be represented by a phase frequency characteristic which is a straight line passing through zero, as indicated by curve A of Fig. 6.
  • a transmitting station T1 and'a receivingstation T2 there is shown a transmitting station T1 and'a receivingstation T2,
  • phase frequency characteristic for a repeater section of cable plus the equalizer may take on a large variety of forms, any departure from the simple relationship of curve A of Fig. 6 tending to bring about the desired effect. Since the summation in expression (3) is rendered small through an averaging process it is obvious that a large number of terms will be required to bring about a high degree of precision; nevertheless even with a relatively small number of repeaters such averaging as is obtained would, in general, represent a reduction in the modulation output over that obtained without this shift. A certain amount of phase shift or distortion is ordinarily present in any cable section but frequently, and especially in the'case of the coaxial cable, this will not be sufficient to assure the extent of phase shift which is brought about by additional phase distortion.
  • phase equalizers will of course have a cumulative phase distorting effect upon the signal itself,,quite aside from the effect SOUS it has on the modulationproducts.
  • phase distortion of the signal if it becomes appreciable, can be compensated for completely at one point or another in the transmission line, such, for example, as at the receiving end where there is shown an inverse phase equalizer IPE.
  • phase equalizer in front of each repeater, it is apparent that this may not be necessary in some cases, but that, as shown in Fig. 2, there may be a phase equalizer for groups of two, or three, or more repeaters.
  • the group of repeaters plus their cables associated with one phase equalizer may be considered as the equivalent of one of the repeaters plus its cable in Fig. 1.
  • the line may even be divided into but two sections at any desired point and still yield substantial improvement with properchoice of phase shift. In general, however, it is desirable but not necessary that the number of points at which the phase equalizers are introduced should be sufliciently large so that statistical conditions tend to hold.
  • the phase shift for one section may vary either because of temperature or humidity variations as they affect the cable, or because of aging of the repeaters, or for other rea-
  • such variations may not be significant but in the case of a line involving, for example, several hundred or several thousand repeaters in tandem the accumulated effect may be very substantial and in this case it may be desirable to make the phase equalizer at the input of a repeater variable in such a manner as to compensate for the variations arising otherwise .in the repeater section.
  • a large variety of circuit arrangements may be used for this purpose and one such arrangement is shown in Fig.
  • this nals of these frequencies are impressed on the repeater section and are shown as being taken off at the output of the repeater R by sharply selective filters, such as crystal filters CF1 and CFz.
  • These two frequencies may now be amplified and passed through a suitable detecting device D which will have an output the phase and amplitude of which are dependent on the phase relationship between f1 and f2, and they may be used to control some device such as a motor M to change the phase equalizer by an amount sufficient to compensate for the variation which has taken place in the repeater section.
  • the motor for example, may be used to control a variable air condenser.
  • the detecting device D may take on a large variety of forms, one such form is shown in Fig. 4 for illustrative purposes.
  • the output of the filter CF1 is impressed by means of a transformer on a circuit comprising two rectifiers l and 2, such as copper-oxide rectifiers.
  • the circuit also includes an impedance such as the resistances 3 and 4.
  • particular network is a transformer the primary of which is supplied from the output of the filter CFz.
  • the direction of flow of the rectified current in the resistances will be in the one direction or the other depending upon whether there has been a shift in phase in one direction or the other of one of the pilot signals'with respect to the other.
  • Corrections such as described may be added at and for each repeater or each phase equalizer or in groups of repeaters in any desired arrangement, dependent on the nature and magnitude of the variations.
  • a signal transmission system comprising a transmission line with a plurality of repeaters in tandem
  • the method of reducing the ratio of modulation products to signal intensity which consists in introducing phase frequency distortion throughout the entire transmitted band at a plurality of intermediate points on the transmission system to introduce phase displacement between the even and odd order modulation products at one point in the line and the corresponding modulation products generated at subsequent points on the line.
  • a signal transmission system comprising a transmission line with a plurality of repeaters in tandem
  • the method of reducing the ratio of modulation products to signal intensity which consists in introducing phase frequency distortion at a plurality of intermediate points on the transmission system to introduce phase displacement between the modulation products at one point in the line and the modulation products generated at subsequent points on the line, such phase frequency distortion incidentally producing cumulative phase distortion in the desired. signal. and introducing at a point in the line a correcting network for the phase distortion given to the desired signal.
  • a signal transmission system comprising a transmission line with a plurality of repeaters in tandem
  • the method of reducing the ratio of mod ulation products to signal intensity which consists in introducing phase frequency distortion at a plurality of intermediate points on the trans-- mission system to introduce phase displacement between the even and odd order modulation products at one point in the line and the corresponding modulation products generated at subsequent points on the line and introducing near the end of the transmission line a correcting network for the phase distortion given to the desired signal at the plurality of intermediate points.
  • the method of reducing the ratio of modulation products to signal intensity which consists in introducing phase frequency distortion at a plurality of intermediate points on the transmission system to introduce phase displacement of the various modulation products in such manner that the modulation vectors at the plurality of intermediate points have phase angles random- 1y distributed with respect to each other.
  • a signal transmission system comprising a transmission line with a plurality of repeaters in tandem
  • the method of reducing the ratio of modulation products to signal intensity which consists in introducing phase distortion at a plurality of points of such number and of such magnitude that the net result of the modulation products increases approximately in accordance with I the square root of thenumber of repeaters.
  • a broad band signal transmission system comprising a transmission line with a multiplicity of spaced repeaters in tandem relation in the line with intermediate sections of line between the said repeaters, phase distorting networksassociated with the individual repeaters, each of said networks together with the corresponding section having a resultant phase frequency characteristic which is non-linear over the transmitted band.
  • phase distorters at distributed points along the system producing phase frequency distortion throughout the entire transmitted band for so introducing phase displacement between modulation products of even and odd order generated in the successive repeaters as to cause said products generated in the various repeaters to add to a total resultant modulation for the system less than the total resultant modulation that would be obtained in the absence of the aforesaid phase distorters.

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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)
  • Radio Relay Systems (AREA)
US158294A 1937-08-10 1937-08-10 Distortion correction in wave transmission Expired - Lifetime US2140492A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
BE429535D BE429535A (xx) 1937-08-10
US158296A US2140900A (en) 1937-08-10 1937-08-10 Distortion correction in wave transmission
US158294A US2140492A (en) 1937-08-10 1937-08-10 Distortion correction in wave transmission
CH239303D CH239303A (de) 1937-08-10 1938-07-29 Fernmeldeanlage.
FR841940D FR841940A (fr) 1937-08-10 1938-08-09 Systèmes de communication électrique
GB23601/38A GB517601A (en) 1937-08-10 1938-08-10 Distortion correction in electric wave transmission

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US158294A US2140492A (en) 1937-08-10 1937-08-10 Distortion correction in wave transmission

Publications (1)

Publication Number Publication Date
US2140492A true US2140492A (en) 1938-12-20

Family

ID=22567463

Family Applications (1)

Application Number Title Priority Date Filing Date
US158294A Expired - Lifetime US2140492A (en) 1937-08-10 1937-08-10 Distortion correction in wave transmission

Country Status (5)

Country Link
US (1) US2140492A (xx)
BE (1) BE429535A (xx)
CH (1) CH239303A (xx)
FR (1) FR841940A (xx)
GB (1) GB517601A (xx)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2449174A (en) * 1942-04-13 1948-09-14 Decca Record Co Ltd Antenna supply phase and amplitude control
US2554153A (en) * 1948-04-14 1951-05-22 Bell Telephone Labor Inc Telephotograph system, including a pilot gain control channel
US20040213573A1 (en) * 1999-12-29 2004-10-28 Philips Electronics North America Corp. Amplifier composite triple beat (CTB) reduction by phase filtering

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2449174A (en) * 1942-04-13 1948-09-14 Decca Record Co Ltd Antenna supply phase and amplitude control
US2554153A (en) * 1948-04-14 1951-05-22 Bell Telephone Labor Inc Telephotograph system, including a pilot gain control channel
US20040213573A1 (en) * 1999-12-29 2004-10-28 Philips Electronics North America Corp. Amplifier composite triple beat (CTB) reduction by phase filtering
US7474150B2 (en) * 1999-12-29 2009-01-06 Broadband Royalty Corporation Amplifier composite triple beat (CTB) reduction by phase filtering

Also Published As

Publication number Publication date
CH239303A (de) 1945-09-30
FR841940A (fr) 1939-06-01
GB517601A (en) 1940-02-02
BE429535A (xx)

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