US2374872A - Attenuation equalizer - Google Patents

Attenuation equalizer Download PDF

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Publication number
US2374872A
US2374872A US482081A US48208143A US2374872A US 2374872 A US2374872 A US 2374872A US 482081 A US482081 A US 482081A US 48208143 A US48208143 A US 48208143A US 2374872 A US2374872 A US 2374872A
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United States
Prior art keywords
impedance
equalizer
variable
network
resistor
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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US482081A
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English (en)
Inventor
Walter R Lundry
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
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Bell Telephone Laboratories Inc
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Filing date
Publication date
Priority to NL76851D priority Critical patent/NL76851C/xx
Priority to BE474907D priority patent/BE474907A/xx
Application filed by Bell Telephone Laboratories Inc filed Critical Bell Telephone Laboratories Inc
Priority to US482081A priority patent/US2374872A/en
Application granted granted Critical
Publication of US2374872A publication Critical patent/US2374872A/en
Priority to FR981566D priority patent/FR981566A/fr
Priority to GB21762/47A priority patent/GB636620A/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
    • H04B3/14—Control of transmission; Equalising characterised by the equalising network used
    • H04B3/141—Control of transmission; Equalising characterised by the equalising network used using multiequalisers, e.g. bump, cosine, Bode
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/02—Details
    • H04B3/04—Control of transmission; Equalising
    • H04B3/14—Control of transmission; Equalising characterised by the equalising network used
    • H04B3/143—Control of transmission; Equalising characterised by the equalising network used using amplitude-frequency equalisers
    • H04B3/145—Control of transmission; Equalising characterised by the equalising network used using amplitude-frequency equalisers variable equalisers

Definitions

  • a T TORNEV in a transmission either direction from over-all fiat loss may Patented May 1, 1945 UNI ED STAT S PATENT ornca ATTENUATION EqUAL'rzEa Walter R. Lundry, Maplewood, N. J., asslgnor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application April 7, 1943, SerlalNo. 482,081
  • This invention relates to wave transmission networks and more particularly to variable attenuation equalizers for use as regulating networks.
  • the principal object of the invention is to compensate for changes in the attenuation distortion line or the like caused, for ex'- ample, by variations in temperature or humidity.
  • 'A feature of the invention is anattenuation equalizing network which operates over two separated frequency ranges and is independently variable over one or ,both of the ranges.
  • the attenuation distortion in a telephone circuit varies continually due to changes in temperature or humidity.
  • Continuously variable attenuatlon equalizers which may be varied in a constant fiat loss are employed to compensate for these variations.
  • the practice heretofore has been to use two equalizers, with a resistance pad lbetween, thus more than doubling the flat loss of a single equalizer.
  • By employing special coupling arrangements between the equalizers the be reduced somewhat, but in long circuits the total becomes very large.
  • the attenuation equalizer in accordance with the present invention operates over two'separated frequency ranges but of a single equalizer.
  • the equalizer may be made independently varialble over one or both of the ranges.
  • the variable elements may, for example, be only two variable resistors which are readily adapted for automatic regulation.
  • the equalizer which is of the general type disclosed in'United States Patent 2,096,027, issued October 19. 1937, to H. W. Bode, comprises a variable impedance coupling branch connected in series or in parallel with the wave source impedance and the load impedance.
  • the coupling branch comprises a fixed resistor connected atone end of a subsidiary four-terminal bridged-T network terminated at its other end in a variable impedance which may be either a variable resistor or a four-terminal constant resistance buildingcut network terminated in a variable resistor.
  • the subsidiary network comprises a reactive bridging impedance branch and a reactive shunt impedance branch which are inversely related and two series branch'es, either a variable resistor, a fixed frequency-dependent impedance or a variable frequency-dependent impedance.
  • This last-mentioned impedance may include a second four-terminal! introduces only the flat loss one of which may be Ill constant resistance building-out network terminated by a variable resistor.
  • the equalizer may be designed to provide substantially independent
  • Fig. 1 is a schematic circuit showing one form of the two-range attenuation equalizer of the invention, employing a series coupling branch which comprises two building-out networks terminated in variable resistors:
  • Fig. 2 is a schematic circuit showing another form of the equalizer similar to one shown in Fig. 1 except that the coupling branch is connected in parallel;
  • Fig. 3 shows an equalizer circuit similar to the one of Fig. 1 except that the building-out networks are omitted;
  • Fig. 4 is a circuit similar 'to the one shown in Fig. 2 but with the building-out networks omitted:
  • Fig. 5 shows a circuit similar to the one of Fig.3 except that one of the variable resistors 'is replaced by a frequency-dependent impedance; v
  • Fig. 6 is a circuit similar to the one shown in Fig. 4 'but with a frequency-dependent impedance substituted for one of the variable resistors;
  • Fig. 7 is a schematic circuit showing the structure of Figs. 1 and 2 formed into a bridged-T network; 1
  • Fig. 8 shows the structures of Figs. 5 and '6 formed into a bridged-l network
  • Fig. 9 shows two equalizers of the type shown in Fig. l coupled by resistors to provide a fourrange network.
  • Fig. 1 shows a series type of two-range attenuation equalizer in accordance with the invention.
  • the network which is of'the same general configuration as the one shown in Fig. 11 of the abovementioned Bode patent, has a pair or input terminals l, 2 to which is connected a wave source of impedance Zs and voltage E and a pair of output terminals 3, 4 to which the load impedance Zn is connected.
  • a variable impedance coupling branch 5 which comprises a fixed resistor of value R and a four-terminal subsidiary network 6 .of the bridged-T type having two pairs of terminals 1. 6 and 9, ill.
  • the resistor R is connected. between the terminals I and I of the load impedances and the terminals I and 6 of the network 6 are connected respectively, to the terminals of the resistor R.
  • the network 6 is terminated at its other end in a variable impedance which comprises a four-terminal building-out network N1 terminated in a variable resistor R1.
  • the subsidiary network 6 comprises a reactive bridging impedance Z1 and a reactive shunt imp'edance Z2, which are inversely related to each other with respect to R0, and two series branches.
  • One of the series branches is the fixed resistor of value R and the other is constituted by a second four-terminal building-out network N: terminated in a secondvaria-ble resistor R2.
  • the building-out networksNi and N have image impedances equal to the subsidiary network pedance of Ra.
  • Equation 3 shows/that, in-g'eneral, the presence of the building-out networks N1 and N2 reduces the maximum loss swing that would be obtained if they were omitted. It follows, therefore, that the impedancs Z1 and Z2. which are general in character, must be chosen to give a somewhat greater swing than is desired from the network as a whole. Furthermore, in order to insure substantial independence of regulation over two frequency ranges, Z1 must be large compared to R0 over the range in which p: is to control the regulation and Z2 must be large compared to R0 over the range where 91 is to control.
  • the change in insertion los a-ao be substantially proportional to min the one frequency range and to p: in the other range. From Equation 3 it is apparent that, in the range where p1 controls, the desired result maybe accomplished in one of the following ways: flrst,-'by setting R2 equal to Ray sec- 0nd, by making the real part of 2+o4) large compared to unity; or, third, by making the phase angle of pz+ i) equal to 45 degrees.
  • any two or all three of these conditions may be approximated at the same time.
  • R1 controls either R1 is set at the value R41, the real part of (pH-(pa) is made large compared to unity or the phase angle of (oi-i-r a) is made equal to 45 degrees.
  • the two-range attenuation equalizer shown schematically in Fig. 2 is of the shunt type, having the same general configuration as shown in Fi s. 15 and 2'7 of the above-mentioned Bode patent.
  • the variable impedance coupling branch H which is connected between the points l2 and It in parallel with the load impedances Z5 and Zn, comprises a fixed resistor R: and a subsidiary bridged-T network 6 similar to the subsidiary network used in the equalizer of Fig. 1.
  • One terminal of the resistor R3 is connected to the point i2 and the other terminal is connected to terminal I of the network 6, terminal 6 of which is connected to the point It.
  • the equalizer of Fig. 2 may be designed in accordance with the principles set forth above to give the sametype of regulation under the control of the variable resistors R1 and-R: as is obtainable with the equalizer of Fig. l.
  • the insertion factor, for the condition that R1 and R: are both set equal to R0, is given by the expression Ra ows-ln) s n( R1+ Rn) (8)
  • the regulation characteristic for other settings of R1 and B: may be found from Equation 3 by multiplying either side by (l).
  • the building-out networks N1 and N are not needed tion characteristic.
  • Fig. 4 shows the alternative shunt typ circuit of Fig. 2 with the networks N1 and N2 omitted.
  • a useful modification of the circuits of Figs. 3 and 4 is to replace one of the variable resistors by either a'fixed or a variable frequency-dependent impedance.
  • the variable resistor R2 is replaced by the frequency-dependent impedance Z3, which may be either variable, as indicated by the arrow, or fixed. If 23 is fixed, the equalizer is, of course, variable over only one range.
  • a two-range equalizer having at each end an image impedance R03 which is a constant resistance may be provided by combining series and shunt type networks in a bridged-T structure.
  • Fig. '7 shows such a bridged-T, with input terminals l4, l5 and output terminals l6, l1, comprising two equal series resistors Ra.
  • Ra an in terposed shunt branch l8 connected between the points I9, 20 and a bridging branch 2i connected to the terminals 22, 23.
  • the bridging branch. 2 I which is similar to the series coupling branch 5 of Fig. 1, comprises a subsidiary bridged-T network 24 of constant resistance image impedance R01, with terminals 22, 28 and 25, 26, similar to the network 6 of Fig. l.
  • the series arms of the network 24 are constituted by a fixed resistor of value R01 and a building-out network N12, also of constant resistance image impedance R01. terminated in a variable resistor R 2.
  • V ZuZis R01 (10)
  • the network 24 is terminated at its terminals 26.
  • the shunt branch it which is similar to shunt ance image impedance Ros, with terminals 2
  • the series arms of the network 21 are constituted by a fixed resistor of value R02 and athird. building-out network N22, also of constant resistance image impedance Roz, terminated in a variable resistor R221.
  • the bridging impedance Zn and the shunt impedance Z22 have the relationship i4, i5 and i6, I I of the equalizer of Fig. 7, the
  • the series type equalizer of Fig. 5. and the shunt type equalizer of Fig. 6 may also be combined in a constant resistance bridged-T structure, as shown in Fig. 8.
  • the circuit of Fig. 8 is similar to the one shown in Fig. '7 except that the building-out networks Nu, Nu, N21 and Na are omitted and the variable resistors R1: and
  • the impedances Zn and Zn may be made adjustable as indicated by the arrows. If the constant resistance image im- P dance R03 is to be maintained the values of the impedances Z13 and Z2: must satisfy Equation 14 for all settings and, therefore, these impedances may conveniently be arranged for unitary control, as indicated.
  • the impedance Z1: and Z2: may, of course, be simple variable resistors such as R: in Figs. 3 and 4.
  • Fig. 9 shows two networks at and II of the type shown in Fig. 1 connected in tandem between the terminal loads Z5 and Zn to provide an equalizer which may be designed to give independent regulation over four frequency ranges. I'hese ranges may, if desired, coincide in pairs to give in eflect double regulation over two ranges.
  • the resistor R and the bridged-T auxiliary net- The resistors R5 and Re correspond to.
  • the two equalizers 84 and l! are coupled by means of a r type resistance pad I. made up of the two shunt resistors R1, Re and the interposed series resistor Rn. It will be noted that the leads 3.
  • a variableattenuatlon equalizer comprising in combination with a wave sourceimpedance and a load impedance a coupling branch interposed between said. impedances, said coupling branch comprising a subsidiary four-terminal bridged-T networ a resistor connected at one end of said subsidiary network and a variable impedance terminating said network at its other end, said network comprising two series branches. an interposed reactive shunt impedance and a reactive bridging impedance, said shunt impedance and said bridging impedance being inversely related to each other and one of said series branches having a frequency-dependent impedance characteristic.
  • variable impedance comprises a fourterminal building-out network.
  • variable impedance comprises a fourterminal building-out network of constant re- 1 which said one series branch and impedance each comprises a tour-terminal buildterminal building-out .ing-out network ingeout network resistance image sistance image impedance terminated by a variable resistor.
  • variable impedance comprises a fournetwork of constant re-' sistance image impedance Ru terminated by a variable resistor and the other of said series branches is a resistor of value R0.
  • a bridged-T attenuation equalizer of constant resistance image impedance Ros comprising a bridging branch and a-shunt branch, each of said branches comprising a subsidiary tour-terminal bridged-T network and a variable impedance terminating said network, each or said networks comprising two series branches, an interposed reactive shunt impedance and a reactive bridging impedance,'said shunt impedance and said bridging impedance being inversely related to each other and one of said series branches having a frequency-dependent impedance characteristic.
  • each comprises a four-terminal buildof constant resistance image impedance Ru terminatedby a variable resistor, the other of said series branches is a resistor of value R0 and said shunt and bridging impedances are inversely related with respect to Re.
  • An equalizer in accordance with claim 20 in which said one series branch comprises a tourterminal building-out network of constant resistance image impedance terminated by a variable resistor.
  • variable impedance comprises a tour-terminal building-out network.
  • variable impedance comprises a four-terminal building-out network of constant resistance image impedance terminated by a variable resistor.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Networks Using Active Elements (AREA)
  • Filters And Equalizers (AREA)
  • Details Of Connecting Devices For Male And Female Coupling (AREA)
US482081A 1943-04-07 1943-04-07 Attenuation equalizer Expired - Lifetime US2374872A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
NL76851D NL76851C (en(2012)) 1943-04-07
BE474907D BE474907A (en(2012)) 1943-04-07
US482081A US2374872A (en) 1943-04-07 1943-04-07 Attenuation equalizer
FR981566D FR981566A (fr) 1943-04-07 1947-07-22 égaliseur d'affaiblissement pour réseaux de transmission
GB21762/47A GB636620A (en) 1943-04-07 1947-08-07 Improvements in or relating to attenuation equalizers

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Application Number Priority Date Filing Date Title
US482081A US2374872A (en) 1943-04-07 1943-04-07 Attenuation equalizer

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US2374872A true US2374872A (en) 1945-05-01

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US482081A Expired - Lifetime US2374872A (en) 1943-04-07 1943-04-07 Attenuation equalizer

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US (1) US2374872A (en(2012))
BE (1) BE474907A (en(2012))
FR (1) FR981566A (en(2012))
GB (1) GB636620A (en(2012))
NL (1) NL76851C (en(2012))

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2510283A (en) * 1949-01-18 1950-06-06 Bell Telephone Labor Inc Variable equalizer
US2607851A (en) * 1947-11-18 1952-08-19 Bell Telephone Labor Inc Mop-up equalizer
US2694184A (en) * 1951-03-16 1954-11-09 Bell Telephone Labor Inc Equalizer
US2718622A (en) * 1953-03-16 1955-09-20 Bell Telephone Labor Inc Attenuation equalizer
US2792552A (en) * 1953-11-27 1957-05-14 Bell Telephone Labor Inc Attenuation equalizer
DE1242272B (de) * 1959-01-13 1967-06-15 Standard Elektrik Lorenz Ag Anordnung zur einstellbaren, frequenzabhaengigen Amplitudenentzerrung in UEbertragungssystemen

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2607851A (en) * 1947-11-18 1952-08-19 Bell Telephone Labor Inc Mop-up equalizer
US2510283A (en) * 1949-01-18 1950-06-06 Bell Telephone Labor Inc Variable equalizer
US2694184A (en) * 1951-03-16 1954-11-09 Bell Telephone Labor Inc Equalizer
US2718622A (en) * 1953-03-16 1955-09-20 Bell Telephone Labor Inc Attenuation equalizer
US2792552A (en) * 1953-11-27 1957-05-14 Bell Telephone Labor Inc Attenuation equalizer
DE1242272B (de) * 1959-01-13 1967-06-15 Standard Elektrik Lorenz Ag Anordnung zur einstellbaren, frequenzabhaengigen Amplitudenentzerrung in UEbertragungssystemen

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GB636620A (en) 1950-05-03
NL76851C (en(2012))
FR981566A (fr) 1951-05-28
BE474907A (en(2012))

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