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US2205843A - Double balanced modulating system - Google Patents

Double balanced modulating system Download PDF

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Publication number
US2205843A
US2205843A US193637A US19363738A US2205843A US 2205843 A US2205843 A US 2205843A US 193637 A US193637 A US 193637A US 19363738 A US19363738 A US 19363738A US 2205843 A US2205843 A US 2205843A
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US
United States
Prior art keywords
bridge
carrier
source
rectifiers
conductive
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
US193637A
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English (en)
Inventor
Robert S Caruthers
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
Application filed by Bell Telephone Laboratories Inc filed Critical Bell Telephone Laboratories Inc
Priority to US193637A priority Critical patent/US2205843A/en
Priority to GB1218/39A priority patent/GB523897A/en
Priority to FR850909D priority patent/FR850909A/fr
Priority to DEI63970D priority patent/DE735909C/de
Application granted granted Critical
Publication of US2205843A publication Critical patent/US2205843A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03C—MODULATION
    • H03C1/00—Amplitude modulation
    • H03C1/52—Modulators in which carrier or one sideband is wholly or partially suppressed
    • H03C1/54—Balanced modulators, e.g. bridge type, ring type or double balanced type
    • H03C1/56—Balanced modulators, e.g. bridge type, ring type or double balanced type comprising variable two-pole elements only
    • H03C1/58—Balanced modulators, e.g. bridge type, ring type or double balanced type comprising variable two-pole elements only comprising diodes

Definitions

  • This invention relates to modulating systems and more particularly to those systems in which transmission of the unmodulated carrier and of other undesired wave components is substantially prevented.
  • An object of the invention is to combine two impressed waves in a modulating, demodulating v or detecting arrangement and to take off through a load circuit adesired combination product of the impressed waves while preventing the impressed waves and certain undesired combination products being transmitted to the load circuit.
  • a system of the type to accomplish this result is commonly called a double balanced system.
  • Double balanced systems are already known which employ a plurality of modulating elements together with several balanced inductive wind ber 24, 1935, to F. A. Cowan, is an example of a.
  • circuit employing a minimum number of elements, there being four balanced coils and four modulating elements.
  • the balanced coils may'be called upon to carry a verywide rangeof signal frequencies. Consequently,-the design and manufacture of the I coils may become diiiicult and uneconomical. In all the double balanced systems of which I am aware, one or more .coils are employed and several of these must carry the full range of impressed 4o frequencies constituting the signal band.
  • the modulators are less costly than the coils. Accordingly, to reduce the cost ofa double bal- 45 anced system, particularly for broad band applie cations it is expedient to increase the number of modulators employed where this makes possible a reduction in the number 'of coils required to carry the broad band of frequencies.
  • sixteen modulators are employed with the result that all coils are eliminated from the portion of the circuit traversed by the broad bands of frequencies. While coils are still used in impressing the carrier wave upon the 55 system, these coils need transmit only a single frequency and the balanced coils do not exceed four in number.
  • each of the ratio arms of the primary bridge comprises a group of four rectifiers, gthemselves arranged in the form v of a Wheatstone bridge, referred to hereinafter as a 10 secondary bridge.
  • the rectifiers in the secondary bridges are arranged to be biased simultaneously into a conductive condition or simultaneously into a non-conductive condition under the control of a carrier wave impressed upon one pair of 15 diagonally opposite corners.
  • the secondary bridge is connected into the primary bridge at its other pair of corners.
  • A' multiwinding transformer is provided for impressing the carrier wave upon the four sec- 20 ondary bridges simultaneously in the proper phase relationship to each secondary bridge to make two opposite arms of the primary bridge conductive while the other. two arms are made non-conductive.
  • the signal source and the load '25 circuit are connected in opposite diagonals of the primary bridge.
  • the action of the carrier wave causes periodic reversals of the connections between the signal source and the load. These reversals occur at a rate determined by the car- 80 rierfrequency, with the result that a pure modulated wave, free from the signal wave and from the unmodulated carrier, istransmittedto the load.
  • the transformer need transmit only the carrier frequency since the signal wave and the side-bands of the modulated wave do not traverse any winding of the transformer.
  • Fig. 1 is a schematic representation of an embodiment of the inventiomand Figs. 2 and 3 are diagrams useful in explaining the operation of the circuit of Fig. 1.
  • the junction points A, B, C, D are the corners of the primary bridge.
  • the primary bridge arm AB comprises-a secondary bridge I which in turn is composed of the modulators or rectifiers l I, l2, l3, l4.
  • the arm BC comprises a secondary bridge 2 with the arms,-composed of rectiflers 2
  • the arm CD comprises bridge 3 with secondary arms BI, 32, 33, 34;
  • the arm- DA comprises bridge 0 with secondary arms 4
  • the sixteen rectiflers are preferably substantially alike, the 56 iii) conductive direction of each being indicated by the direction of the arrow in the symbol for the rectifier according to a common convention.
  • a signal source represented by the block is connected in the primary bridge diagonal BD and a load circuit represented by the block 3 in the diagonal A0.
  • a carrier source b is connected to the primary winding til of a transformer T having a plurality of secondary windings til, 62, 53, 6 3.
  • Thesecondary windings are assumed to be wound all in the same direction so that the induced currents at any instant are to be taken as flowing either from bottom to top in all the coils, or
  • the actual direc tion of the windings in an embodiment of the transformer may, of course, be chosen in any convenient way and the connections between the coils and the bridge made such as to preserve the desired phase relationships as specified. To determine these phase relationships assume the currents to flow from the bottom to the top of all the coils. The connections to the secondary bridge are then to be made so that the current in coil 6!
  • the primary bridge except for the action of the carrier source Eyis balanced, so that the's'ignal source 5 can pass substantially no current'into the load I.
  • the carrier source by its action upon the recti+ fiers. serves to unbalance the bridge first on one side and then on the other alternately; allowing.
  • the bridge serves to reverse the connections between the signal source and the load at a rate determined by the carrier frequency.
  • thebridge acts as a commutator at the carrier frequency.
  • rier source and load circuit occupy mutually conjugate positions in the system.
  • simple transmission here is meant transmission without frequency change and without the intervention of a modulation process of some sort.
  • the carrier wave is balanced in each sec ondary bridge and thus the carrier source cannot send current to the signal source or to the load circuit at any time.
  • the balance of the secondary bridges is not disturbed during operation of the system. In other words, the system functions to suppress the carrier wave.
  • each rectifier shown in Fig. 1 may be composed of two or more rectifiers in order to secure more nearly identical bridge arms.
  • the use of a plurality of rectifiers is, of course, a means of obtaining an average operating characteristic which will match the average for another set of rectifiers more nearly thanthecharacteristic of one rectifier matches that of another rectifier.
  • , 52, 63, 6 21 should also be well balanced, that is, preferably all identical and symmetrically related to coil 60. These windings,
  • the signal source 5 andthe load circuit 1 may be interchanged without aifecting the essential operation of the circuit.
  • the modulators may be of any desired or suitable type and need not be rectifiers. For example, they may be any devices whichconduct unequally in two directions, and they may be controlled by grids in known manner, or by other means heside direct application of the carrier wave.
  • the signal source may also be replaced by a source of modulated waves in which case the circuit of Fig. 1 may be operated as a detector or demodulator and the detected or demodulated signals received in the load circuit.
  • a modulating system comprising a plurality of rectifiers, a source of signal waves, a load circuit, a source of carrier waves, four branch circuits for carrier waves each coupled to said carrier source and each branch circuit including at least one of said rectifiers, a pair of carrier equipotential points in each of said branch circuits between which points no material potential difference is developed by waves from said carrier source, and a bridge arrayhaving the usual four bridge arms and two bridge diagonals, said bridge arms including said four branch circuits respectively, each connected-in at the said pair of carrier equipotential points, and said source of sigof which bridge forms a ratio arm of a larger bridge including allsixteen rectifying elements,
  • a multiwinding transformer a carrier source connected through said transformer across the free diagonal of each of said smaller bridges, and a signal source and a load circuit connected in v opposite diagonals of said larger bridge.
  • a system accor to claim 2 in which the rectifying elements are individually so poled that the application of a carrier wave from the carrier source causes alternate pairs of opposite arms of the larger bridge to become conductive and causes the other two arms to be non-conductive while an the first two are conductive.
  • a modulating system comprising 21. Wheatstone bridge network with the usual four corners, two diagonals, and fourv ratio arms, each ratio arm containing four rectiiiers connected series-parallel, each parallel branch containing two rectiflers with their conductive directions opposed to each other, one parallel branch in each ratio arm comprising two rectifiers each with its conductive direction toward the nearest corner of the bridge,
  • each remaining rectifier having its conductive 4 direction away from its nearest bridge corner, a. plurality of inductive windings, one in each bridge arm, each winding being connected between the inner junction of the rectifiers in one parallel fad branch and the inner Junction of the rectiflers in the other parallel branch, a source of carrier waves inductively coupled with each oi. said windings, the poling of the windings being such that the carrier wave at any instant renders the rectigg tiers of two opposite bridge arms conductive and renders the remaining rectiflers non-conductive,
  • 'A modulating system comprising a primary bridge network, a signal source and a load circuit connected in opposite diagonals of the network, a plurality of secondary bridges composed of rectiflers, means for connecting one secondary bridge in each arm of said primary bridge, a carrier source, a transformer coupling said carrier source to the secondary bridges and having a plurality of secondary windings, and means for so connecting the secondary windings that the rectiflers in one pair of opposite primary bridge arms are made conductive during one half-cycle of the carrier wave and the remaining rectifiers are made conductive during the succeeding halfcycle.
  • a modulating system comprising a primary bridge, a signal source in one diagonal of the bridge, a load circuit in the other diagonal of the bridge, a plurality of secondary bridge networks cohtaining rectiflers, said secondary bridges being disposed one in each arm of the primary bridge, a carrier source, a transformer coupling said carrier source to said secondary bridges through a plurality of secondary windings, and means for connecting said secondary windings so that alternate pairs of primary bridge arms are rendered conducting successively in synchronism with the alternations of the carrier wave.
  • a modulating system comprising a primary -bridge network each arm of which contains a secondary bridge composed of rectiflers, a signal source and a load circuit connected in opposite diagonals of the primary bridge, a carrier source, a multiwinding transformer coupling the carrier source to the secondary bridges, and means for connecting the windings of said transformer so that thephase of the carrier wave impressed upon one pair of opposite primary bridge arms is made opposite to the phase of the carrier wave impressed upon the other pair of primary bridge arms.

Landscapes

  • Rectifiers (AREA)
  • Amplitude Modulation (AREA)
  • Coils Or Transformers For Communication (AREA)
US193637A 1938-03-03 1938-03-03 Double balanced modulating system Expired - Lifetime US2205843A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US193637A US2205843A (en) 1938-03-03 1938-03-03 Double balanced modulating system
GB1218/39A GB523897A (en) 1938-03-03 1939-01-13 Double balanced modulating systems for carrier wave signalling
FR850909D FR850909A (fr) 1938-03-03 1939-02-27 Systèmes modulateurs d'ondes électriques
DEI63970D DE735909C (de) 1938-03-03 1939-03-04 Modulationsanordnung

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US193637A US2205843A (en) 1938-03-03 1938-03-03 Double balanced modulating system

Publications (1)

Publication Number Publication Date
US2205843A true US2205843A (en) 1940-06-25

Family

ID=22714417

Family Applications (1)

Application Number Title Priority Date Filing Date
US193637A Expired - Lifetime US2205843A (en) 1938-03-03 1938-03-03 Double balanced modulating system

Country Status (4)

Country Link
US (1) US2205843A (de)
DE (1) DE735909C (de)
FR (1) FR850909A (de)
GB (1) GB523897A (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2530528A (en) * 1944-11-01 1950-11-21 Bell Telephone Labor Inc Phase comparator for underwater signaling
US2961610A (en) * 1949-08-18 1960-11-22 Hans H Hosenthien Reflected nonlinear modulators in alternating current electrical analog computers
US2988706A (en) * 1958-10-29 1961-06-13 Don L Bonham Vibrato circuit comprising a bridge having non-linear impedance elements
US3275951A (en) * 1963-08-01 1966-09-27 Joachim A Maass Ring modulator with large dynamic operating range
US3443249A (en) * 1966-11-22 1969-05-06 Bell Telephone Labor Inc Wave limiter circuit and apparatus

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2530528A (en) * 1944-11-01 1950-11-21 Bell Telephone Labor Inc Phase comparator for underwater signaling
US2961610A (en) * 1949-08-18 1960-11-22 Hans H Hosenthien Reflected nonlinear modulators in alternating current electrical analog computers
US2988706A (en) * 1958-10-29 1961-06-13 Don L Bonham Vibrato circuit comprising a bridge having non-linear impedance elements
US3275951A (en) * 1963-08-01 1966-09-27 Joachim A Maass Ring modulator with large dynamic operating range
US3443249A (en) * 1966-11-22 1969-05-06 Bell Telephone Labor Inc Wave limiter circuit and apparatus

Also Published As

Publication number Publication date
FR850909A (fr) 1939-12-29
DE735909C (de) 1943-06-01
GB523897A (en) 1940-07-25

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