US2819450A - Molecular resonance modulators and demodulators - Google Patents

Molecular resonance modulators and demodulators Download PDF

Info

Publication number
US2819450A
US2819450A US498643A US49864355A US2819450A US 2819450 A US2819450 A US 2819450A US 498643 A US498643 A US 498643A US 49864355 A US49864355 A US 49864355A US 2819450 A US2819450 A US 2819450A
Authority
US
United States
Prior art keywords
gas
energy
frequency
absorption
source
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
US498643A
Other languages
English (en)
Inventor
Charles H Townes
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 NL84979D priority Critical patent/NL84979C/xx
Priority to FR960575D priority patent/FR960575A/fr
Priority claimed from US744236A external-priority patent/US2707235A/en
Application filed by Bell Telephone Laboratories Inc filed Critical Bell Telephone Laboratories Inc
Priority to US498643A priority patent/US2819450A/en
Application granted granted Critical
Publication of US2819450A publication Critical patent/US2819450A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
    • H03L7/00—Automatic control of frequency or phase; Synchronisation
    • H03L7/26—Automatic control of frequency or phase; Synchronisation using energy levels of molecules, atoms, or subatomic particles as a frequency reference
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03C—MODULATION
    • H03C3/00—Angle modulation
    • H03C3/30—Angle modulation by means of transit-time tube
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03C—MODULATION
    • H03C7/00—Modulating electromagnetic waves
    • H03C7/02—Modulating electromagnetic waves in transmission lines, waveguides, cavity resonators or radiation fields of antennas

Definitions

  • MOLECULAR RESONANCE MODULATORS AND DEMDDULATQRS Jharles H. Townes, New York, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Original application April 26, 1947, Serial No. 744,236,
  • This invention relates to systems and methods for modulating electromagnetic wave energy, particularly energy in the microwave range.
  • An object of the invention is to provide a simple and efiicient system for modulating microwave energy by audio or other signaling waves to produce amplitude modulations thereof representative of such signals.
  • Another object of the invention is to provide a simple and efficient system for demodulating microwave energy to recover the signal with which it has been amplitudemodulated.
  • a particular characteristic of the gas resonant absorption efliect is utilized to produce modulation and demodulation of microwaves.
  • This phenomenon is the dependency of the absorption coefiicient to electromagnetic waves of one frequency upon the energy level of electromagnetic waves of a different frequency to which the gas is simultaneously subjected.
  • This effect is due to the fact that the sharp, selective absorption of electromagnetic wave energy of one frequency by such a gas is dependent upon the numbers of the gas molecules that are at the various possible energy levels.
  • the molecular population at these energy levels can be varied by subjecting the gas to electromagnetic wave energy of a frequency different from that of the energy being absorbed. This energy varies the number of molecules in the various energy states, consequently varying the absorption due to molecular resonance of the electromagnetic energy of the first frequency being transmitted through the gas.
  • microwaves which are desired to be modulated are transmitted through a confined body of gas exhibiting molecular resonant absorption at the frequency of the microwaves. Simultaneously the gas is irradiated by other electromagnetic wave energy such as infrared rays.
  • other electromagnetic wave energy such as infrared rays.
  • Fig. 1 shows an amplitude modulator of microwaves utilizing the molecular resonance absorption of a gas irradiated by an auxiliary infrared source
  • Fig. 2 shows a corresponding demodulator
  • the absorption coefficient of many molecularly resonant gases for microwaves or the like is dependent on the presence or absence of an auxiliary electromagnetic field of a different frequency. This permits the energy absorbed from incident electromagnetic waves to be varied at will by subjecting the gas at low pressure to the irradiation by electromagnetic energy of a different frequency.
  • amplitude modulation may be imparted to a microwave frequency or frequencies by passing the microwaves through a molecularly resonant gas and irradiating the gas by a source of different frequency, such as other microwaves, light, or infrared radiations, and varying the irradiation of the gas thereby under the control of a desired modulating signal.
  • the absorption by a molecularly resonant gas of microwave energy may be modified in amount by irradiating the gas with electromagnetic waves of a different frequency.
  • the microwave absorption at low pressures by ordinary ammonia gas of the molecular resonance line at 23,870 megacycles is about 0.2 decibel per foot of length of the gas chamber, for a single energy pass.
  • the gas is irradiated by infrared radiation
  • the absorption of the ammonia resonance line is considerably reduced.
  • the effect may be an increase of absorption. Whether it be a reduction or an increase depends in a complicated fashion on the various characteristics of the particular molecule in question and the frequency of the disturbing radiation. In general, however, there can be a marked alteration in the absorption of microwaves of a first frequency by molecular resonance when the gas molecules are irradiated by a different frequency radiation.
  • a microwave oscillation source lit which may be similar to that described in connection with my aforementioned application or of any desired variety, delivers energy from its resonant cavity 1'7 to a gas-containing molecular absorption cell by way of a wave guide 22.
  • the input frequency to the cell 17% should be substantially equal to the frequency at which the gas is resonant; e. g., if the gas is ordinary ammonia, the frequency should be 24,000 megacycles (more precisely, 23,870 megacycles) and the oscillation source in should be tuned to this frequency and stabilized thereat.
  • the resonant gas cell 170 may be provided with a mica window 24 at the point at which the input wave guide 22 is coupled to it and with a window 25 at the point to which an output wave guide 26, leading to an amplifier 171 and a load circuit, e. g., an antenna 172, is coupled to it.
  • the gas may be introduced by way of a valve 32 and its pressure adjusted by means of a pump 33.
  • the cell 170 may be a wave guide, preferably of the resonant type hereinabove discussed. Its dimensions should be selected so that its resonant frequency, regarded as a tuned cavity, coincides with the resonant frequency of the gas, and its tuning should preferably be substantially broader than the resonant absorption band of the gas.
  • An infrared radiation source 174 for example, an electrically heated platinum ribbon or a caesium vapor lamp, is provided, whose rays 175 may be reflected on a suitable mirror 176, for example a polished copper surface, to enter the resonant gas chamber 170 by way of a window 177 which is transparent to infrared radiation. of the frequency in question, for example a window of silver chloride.
  • the mirror may be caused to vibrate in accordance with a signal, being mounted, for example, in the familiar manner of a galvanometer element, the oscillating signal being derived from an audio frequency source 173.
  • the reflected infrared beam 179 will be caused to swing on and oif the silver chloride window 177 in relation to the signal, and infrared radiation will enter the gas chamber 170 by way of the silver chloride window in greater or lesser amount in dependence on the amplitude of the audio frequency signal.
  • the population of molecules in their various energy states is altered by the incident infrared, and this view is useful in visualizing the phenomenon involved.
  • the resonant absorption of the ammonia gas to the microwave energy of 24,000 megacycles has its full value of 0.2 decibel per foot of passage through the gas.
  • the reflected infrared beam 179 is centered on the Window 177, this absorption is reduced.
  • the microwave energy passing through the chamber 170 and into the output wave guide 26 is alternately increased and reduced in accordance with the signal of the source 178; i. e., amplitude modulation of the microwaves of the source through the medium of a molecularly resonant gas is provided.
  • Fig. 2 shows a system for demodulating microwave energy which may be received, for example, after radio transmission, and which bears a desired signal in the form of amplitude modulation.
  • the incoming amplitude-modulated microwaves may be picked up by an antenna 130 and supplied by way of a wave guide 181 and a mica window 24 into a resonant gas chamber 182 as before.
  • An infrared radiation source 183 is provided in a position such that its rays 184 shine directly into the gas chamber 182 by way of a suitable window 1&5, for example of silver chloride.
  • a suitable window 1&5 for example of silver chloride.
  • another silver chloride window 186 is provided through which emerges the infrared radiation 184 which has not been absorbed by the gas in the chamber 182.
  • the amount of absorption of infrared radiation is dependent on the excitation of the gas by the incoming microwave energy; and since the strength of the latter varies in accordance with the signal which is amplitude-modulated thereon, so the transmitted infrared radiation varies similarly.
  • the transmitted infrared radiation 184 now modulated in accordance with the signal, may be applied to a suitable detector 187, for example a bolometer thermistor of the type described in an application of I. A. Becker, Serial No. 602,261, filed September 26, 1946, Patent 2,414,792, January 28, 1947.
  • the output of this detector 187 may be amplified as desired and reproduced in a suitable manner, for example, by a telephone receiver 188.
  • demodulation or detection of amplitude-modulated microwave radiation is etfected through the medium of the resonant absorption band of a gas.
  • Apparatus for modulating the amplitude of oscillations derived from a microwave source which comprises a gas at low pressure characterized by sharp resonance lines of selective absorption of incident microwave energy of the frequency of said source in an amount dependent on the numbers of the molecules of said gas in the various possible energy levels, means for guiding waves of said source through said gas, whereby energy of said source is absorbed by said gas, an auxiliary source of electro magnetic waves of a higher frequency, means for subject ing said gas to the field of said auxiliary source to alter the said numbers and so the amount of said absorption, and means for varying the strength of said auxiliary source field under control of a modulating signal.
  • a body of gas characterized by the sharp molecular resonance absorption of incident electromagnetic wave energy of one frequency in an amount dependent upon the numbers of the molecules of said gas in the various possible energy levels as determined by the energy level of electromagnetic waves of a second higher frequency also incident upon said gas, means for impressing electromagnetic wave energy of said one frequency on said gas, means for impressing electromagnetic wave energy of said second frequency on said gas at energy levels varying in accordance with a signal, and means responsive to the electromagnetic wave energy of said one frequency after transmission through said gas for communicating said signal.
  • a signalling system comprising a generator of microwaves, a hollow wave guide connected thereto, a resonant cavity interposed in said wave guide having therein a gas at pressures sufiiciently low in the millimeter pressure range to provide sharp molecular resonance absorption, a source of energy for irradiating said gas to vary the absorption coefiicient of said gas whereby the amplitude of the microwaves transmitted through said gas is varied, and means utilizing the microwaves transmitted through said gas.
  • a signalling system comprising a wave guide, a gas at low pressure confined in said wave guide to provide sharp molecular resonance lines, a source of microwaves of frequency corresponding to one of said resonant lines, means for transmitting waves from said source through said wave guide, another source of electromagnetic waves of frequency higher than said microwaves, means for irradiating said gas by waves from the second source, means for varying in accordance with a signal the energy of waves irradiating said gas to vary the absorption coefiicient of said gas whereby amplitude modulation of the microwaves is produced.

Landscapes

  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Electromagnetism (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)
US498643A 1947-04-26 1955-04-01 Molecular resonance modulators and demodulators Expired - Lifetime US2819450A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
NL84979D NL84979C (pt) 1947-04-26
FR960575D FR960575A (pt) 1947-04-26
US498643A US2819450A (en) 1947-04-26 1955-04-01 Molecular resonance modulators and demodulators

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US744236A US2707235A (en) 1947-04-26 1947-04-26 Frequency selective systems
US498643A US2819450A (en) 1947-04-26 1955-04-01 Molecular resonance modulators and demodulators

Publications (1)

Publication Number Publication Date
US2819450A true US2819450A (en) 1958-01-07

Family

ID=27052899

Family Applications (1)

Application Number Title Priority Date Filing Date
US498643A Expired - Lifetime US2819450A (en) 1947-04-26 1955-04-01 Molecular resonance modulators and demodulators

Country Status (3)

Country Link
US (1) US2819450A (pt)
FR (1) FR960575A (pt)
NL (1) NL84979C (pt)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2982855A (en) * 1959-01-29 1961-05-02 Thompson Ramo Wooldridge Inc Neutron detector
EP3791233A4 (en) * 2018-05-10 2021-10-27 Texas Instruments Incorporated COMPACT MILLIMETRIC WAVE SYSTEM

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2955262A (en) * 1957-12-10 1960-10-04 Itt Gas cell for frequency selective system
DE1278555B (de) * 1959-05-01 1968-09-26 Int Standard Electric Corp Atomares Frequenznormal
FR2477766A1 (fr) * 1980-03-05 1981-09-11 Anvar Cellule d'absorption destinee a recevoir un gaz ou une vapeur rarefie, utilisable pour la stabilisation en frequence d'un oscillateur electrique et la spectrometrie

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2106770A (en) * 1938-02-01 Apparatus and method fob receiving
US2423383A (en) * 1944-06-15 1947-07-01 Rca Corp Absorptive gas microwave measuring system

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2106770A (en) * 1938-02-01 Apparatus and method fob receiving
US2423383A (en) * 1944-06-15 1947-07-01 Rca Corp Absorptive gas microwave measuring system

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2982855A (en) * 1959-01-29 1961-05-02 Thompson Ramo Wooldridge Inc Neutron detector
EP3791233A4 (en) * 2018-05-10 2021-10-27 Texas Instruments Incorporated COMPACT MILLIMETRIC WAVE SYSTEM
US11204588B2 (en) 2018-05-10 2021-12-21 Texas Instruments Incorporated Compact millimeter wave system
US11675316B2 (en) 2018-05-10 2023-06-13 Texas Instruments Incorporated Compact millimeter wave system

Also Published As

Publication number Publication date
NL84979C (pt)
FR960575A (pt) 1950-04-20

Similar Documents

Publication Publication Date Title
US2106770A (en) Apparatus and method fob receiving
US2283575A (en) High frequency transmission system
US3967202A (en) Data transmission system including an RF transponder for generating a broad spectrum of intelligence bearing sidebands
US3431504A (en) Acoustical light signal-translating apparatus
US2819450A (en) Molecular resonance modulators and demodulators
US2707235A (en) Frequency selective systems
US2123242A (en) Ultrashort wave receiver
US2314707A (en) Signaling system
US3020398A (en) Sideband intermediate frequency communications system
US2483768A (en) Microwave-acoustic wave translator
US4809355A (en) Method for operating a transmitting/receiving circuit and an apparatus for implementing the method
US2871295A (en) Automatic frequency correction in suppressed carrier communication systems
US3237011A (en) Optical heterodyne demodulator
US1642011A (en) Light telephony
US2095050A (en) Signaling
US2832885A (en) Superheterodyne receiver with local oscillator operating at intermediate frequency for simultaneously monitoring plural channels
US3171031A (en) Optical maser modulators
US3351761A (en) Fm light communications system
US2707231A (en) Frequency stabilization of oscillators
US2423254A (en) Frequency modulation light beam transmission
US2406803A (en) High-frequency electrical communication system
US3694753A (en) System for improving signal-to-noise ratio of a communication signal
US3251997A (en) Optical communication system
US2954477A (en) Radiation detection
US2073409A (en) Signaling system