US1959459A - Frequency changing system - Google Patents

Frequency changing system Download PDF

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Publication number
US1959459A
US1959459A US645301A US64530132A US1959459A US 1959459 A US1959459 A US 1959459A US 645301 A US645301 A US 645301A US 64530132 A US64530132 A US 64530132A US 1959459 A US1959459 A US 1959459A
Authority
US
United States
Prior art keywords
carrier
waves
modulating
output circuit
bridge
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
US645301A
Other languages
English (en)
Inventor
Frank A Cowan
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
American Telephone and Telegraph Co 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 American Telephone and Telegraph Co Inc filed Critical American Telephone and Telegraph Co Inc
Priority to US645301A priority Critical patent/US1959459A/en
Priority to DEI47919D priority patent/DE711547C/de
Priority to GB31383/33A priority patent/GB428293A/en
Priority to FR763697D priority patent/FR763697A/fr
Application granted granted Critical
Publication of US1959459A publication Critical patent/US1959459A/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 frequency changing systems, such as modulators, demodulators, or detectors of the carrier suppression type and more particularly to those employing physically inert non-linear resistance elements as modulating devices.
  • An object of the invention is to improve the economy, stability and reliability of modulating or frequency changing systems.
  • Another object is to secure increased suppression of the carrier wave from the output of a modulator.
  • a number of non-linear resistance elements are arranged in the form of a Wheatstone bridge and interposed between an input circuit and an output circuit.
  • a carrier wave is applied to the bridge network from a source which is connected in conjugate relation to the output circuit, thereby insuring 20 carrier suppression.
  • a suitable biasing means is provided to insure the operation of the resistance elements over a range of continuously variable resistance values.
  • the figure shows a modulating system in which a Wheatstone bridge network containing physically inert non-linear resistance elements is connected in shunt relation to a pair of filters.
  • the input filter FV is adapted to pass a band of signal frequencies from a source 24 such as a microphone and is directly connected to the output filter FSB, which latter passes a band of side frequencies lying adjacent to the carrier.
  • the filter is connected to a load impedance 25.
  • the leads joining the filters are connected also to points 18 and 19, respectively, which are two diagonally opposite corners of the bridge.
  • the bridge comprises the physically inert non-linear conductors 11, 12, 13 and 14.
  • Terminals 15 and 16 constitute the remaining two corners of the bridge.
  • a carrier generator 1'7 is connected through a transformer 21 to the bridge terminals 15 and 16.
  • a polarizing battery 20 is inserted in series with the secondary winding of transformer 21 and preferably between two balanced sections of said winding.
  • the non-linear resistance elements 11, 12, 13 and 14 may be of any known type.
  • copper oxide rectifiers are found to be well adapted. It is not necessary, however, that the wave in the secondary of transformer 21 a non-linear conductor be a rectifier, but any nonlinear device may be used including one which conducts equally well in either direction.
  • An exner as for example, according to the drawing in which rectifiers l1 and 12 are so poled, as indicated by arrows, that each is conductive in the direction toward the common terminal 15 and rectifiers 13 and 14, also indicated by arrows, are so poled that each is conductive away from 7 the common terminal 16.
  • the polarizing battery 20 is poled in such manner as to pass current through all the rectifiers in the conductive direction.
  • Signals or modulating currents are supplied from the source 24. These currents after passing through the filter FV establish an alternating potential of signal frequency across each non-lim ear conductor.
  • the carrier voltage applied to the bridge by the generator 1'? causes the. non linear conductors to vary their resistance in a cyclical manner in synchronism with the alter nations of the generator.
  • the varying resistance 5 of the bridge network produces a variation or modulating action by which the carrier currents and modulating currents are combined in the well known manner to produce a si modulated carrier wave. 7
  • the biasing battery should be of sufii'cient voltage so that the bombined voltage of the battery and the induced from generator 17 will always be unidirectional tors will never become reversed.
  • the carrier voltage impressed upon the individual non-linear conductor should be preferably greater than the modulating voltage, although the adjustment of these voltages need not be very critical.
  • the bridge arrangement may be balanced to a high degree of accuracy by the use of four substantially identical resistance elements produced in a similar manner from similar materials. Moreover, after a balance has once been secured the balanced condition is substantially permanent.
  • the system constitutes an improvement over a balanced arrangement employing vacuum tubes, as the latter must be readjusted at frequent intervals to maintain a good balance.
  • the system illustrated will function equally well as a demodulator and may be so used by supplying a side band current to the filter FSB and connecting the filter FV to a receiver.
  • the side band wave is demodulated with the carrier wave in the non-linear conductors, producing a wave which contains the demodulated signals as a component.
  • a modulating system of the carrier suppression type comprising a source of modulating waves, an input circuit selective to said waves, an output circuit selective to a desired modulated wave, a balanced bridge network comprising four physically inert, non-linear resistance elements interposed between said input and output circuits, and a source of carrier waves connected to said bridge network in conjugate relationship to said output circuit, whereby carrier waves are modulated by combination with modulating waves in said non-linear resistances and modulated waves free from unmodulated carrier are transmitted to said output circuit.
  • a modulating system of the carrier suppression type comprising a source of signal waves, an input circuit selective to the signal waves, an output circuit selective to a desired modulated wave, a bridge network of similar rectifying devices in parallel with said input and output circuits, and a source of carrier waves connected to the bridge in conjugate relation to said output circuit to effect suppression of the carrier waves in said output circuit, said rectifying devices being so disposed and poled that the bridge network substantially short-circuits said output circuit once during each cycle of the carrier wave, whereby said signal waves are interrupted in such manner as to form a modulated wave in said output circuit.
  • a modulating system of the carrier suppression type comprising a source of modulating waves, an input circuit selective to said waves, an output circuit selective to a desired modulated wave, a normally balanced bridge network of twoterminal non-linear resistance elements interposed between said input and output circuits and a source of carrier waves connected to said bridge network in conjugate relationship to said output circuit whereby carrier waves are modulated by combination with modulating waves in said nonlinear resistances and modulated waves free from unmodulated carrier are transmitted to said output circuit.
  • a modulating system of the carrier suppression type comprising a source of modulating waves, an input circuit selective to said waves, an output circuit selective to a desired modulated wave, a normally balanced bridge network of solid non-linear resistance elements interposed between said input and output circuits and a source of carrier waves connected to said bridge network in conjugate relationshipto said output circuit, whereby carrier waves are modulated by combination with modulating waves in said nonlinear resistances and modulated waves free from unmodulated carrier are transmitted to said output circuit.
  • a modulating system of the suppressed carrier type comprising four rectifiers serially connected in a closed loop in the manner of a Wheatstone bridge and being so poled that each rectifier is flanked by two adjacent rectifiers the conductive directions of which are opposed to one another around the loop, a source of signal waves and a load circuit parallel connected in that diagonal of the bridge determined by the 'two corners each lying between adjacent rectifiers whose conductive directions around the loop are the same, and a source of carrier waves connected in the remaining diagonal whereby the bridge network substantially short-circuits said output circuit once during each cycle of the carrier waves and said signals are interrupted in such manner as to form a modulated wave in said output circuit.

Landscapes

  • Amplitude Modulation (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
US645301A 1932-08-25 1932-12-01 Frequency changing system Expired - Lifetime US1959459A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US645301A US1959459A (en) 1932-08-25 1932-12-01 Frequency changing system
DEI47919D DE711547C (de) 1932-08-25 1933-09-09 Modulations- bzw. Demodulationseinrichtung
GB31383/33A GB428293A (en) 1932-08-25 1933-11-10 Arrangements for use in electric signalling systems
FR763697D FR763697A (fr) 1932-08-25 1933-11-10 Perfectionnements aux systèmes modulateurs ou démodulateurs de signaux électriques

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US428293XA 1932-08-25 1932-08-25
US645301A US1959459A (en) 1932-08-25 1932-12-01 Frequency changing system

Publications (1)

Publication Number Publication Date
US1959459A true US1959459A (en) 1934-05-22

Family

ID=26719666

Family Applications (1)

Application Number Title Priority Date Filing Date
US645301A Expired - Lifetime US1959459A (en) 1932-08-25 1932-12-01 Frequency changing system

Country Status (4)

Country Link
US (1) US1959459A (de)
DE (1) DE711547C (de)
FR (1) FR763697A (de)
GB (1) GB428293A (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2438948A (en) * 1944-01-21 1948-04-06 Bell Telephone Labor Inc Modulating system
US2814780A (en) * 1953-07-20 1957-11-26 Engineering Lab Inc Bridge-type modulator mixer
US2830180A (en) * 1955-05-27 1958-04-08 Scott L Shive Noisy signal detector
US2881312A (en) * 1955-05-18 1959-04-07 Hogan Lab Inc Synchronous detector circuit

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE936698C (de) * 1952-08-12 1955-12-22 Telefunken Gmbh Ringmodulatorschaltung
GB849102A (en) * 1955-09-23 1960-09-21 Nat Res Dev Improvements in or relating to fog detecting and like visibility measuring systems
DE1062765B (de) * 1956-09-03 1959-08-06 Suedwestfunk Baden Baden Gleichstromeinspeisung zum Ringmodulator fuer sehr hohe Frequenzen, vorzugsweise Fernseh-frequenzen

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2438948A (en) * 1944-01-21 1948-04-06 Bell Telephone Labor Inc Modulating system
US2814780A (en) * 1953-07-20 1957-11-26 Engineering Lab Inc Bridge-type modulator mixer
US2881312A (en) * 1955-05-18 1959-04-07 Hogan Lab Inc Synchronous detector circuit
US2830180A (en) * 1955-05-27 1958-04-08 Scott L Shive Noisy signal detector

Also Published As

Publication number Publication date
DE711547C (de) 1941-10-02
GB428293A (en) 1935-05-10
FR763697A (fr) 1934-05-03

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