US2295351A - Modulating system - Google Patents

Modulating system Download PDF

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Publication number
US2295351A
US2295351A US275370A US27537039A US2295351A US 2295351 A US2295351 A US 2295351A US 275370 A US275370 A US 275370A US 27537039 A US27537039 A US 27537039A US 2295351 A US2295351 A US 2295351A
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US
United States
Prior art keywords
impedance
impedances
antenna
modulator
variable
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
US275370A
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English (en)
Inventor
David G C Luck
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.)
RCA Corp
Original Assignee
RCA Corp
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 NL58726D priority Critical patent/NL58726C/xx
Application filed by RCA Corp filed Critical RCA Corp
Priority to US275370A priority patent/US2295351A/en
Priority to GB9216/40A priority patent/GB540804A/en
Priority to CH219821D priority patent/CH219821A/de
Application granted granted Critical
Publication of US2295351A publication Critical patent/US2295351A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/005—Control of transmission; Equalising
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03C—MODULATION
    • H03C1/00—Amplitude modulation
    • H03C1/08—Amplitude modulation by means of variable impedance element
    • 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
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
    • H03H7/38—Impedance-matching networks
    • H03H7/40—Automatic matching of load impedance to source impedance
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H5/00—One-port networks comprising only passive electrical elements as network components

Definitions

  • This invention relates to modulating systems, and more particularly to an improved modulator of the absorption or phase opposition type in which a constant load impedance is presented to the radio frequency output tubes so that fre-: quency and phase distortion is reduced.
  • the impedance of the load to which the generator is connected varies between wide limits.
  • the impedance presented to the generator through the impedance inverter is high, while, during upward modulating peaks, when the absorption or modulatortube is biased below plate current cut-off,
  • phase or frequency modulation is produced and the output tubes of the generator are not able to operate at their greatest efllciency over the entire operating cycle.
  • the absorption and phase opposition modulators have another common feature. In both instances, modulation is accomplished by dissipating energy in a circuit which represents a complete loss insofar as the radiated energy is concerned.
  • the modulator tubes must absorb and dissipate as heat the output of the output amplifier tubes, and for intermediate degrees of modulation at least some of the generated energy is absorbed and dissipated as heat loss.
  • Figures 1 and 2 are simplified diagrams to aid in the explanation of the operation of this invention
  • Figure 3 is a block diagram illustrating a modulator in accordance with this invention
  • v Figures 6 and 7 are modifications of the arrangement shown in Figures 4 and 5
  • Figure 8 is the circuit diagram of a modulator.
  • R1 represents the impedance of an antenna
  • Re represents the equal impedance of a second similar antenna, or an absorbing network of identical characteristics
  • R1 and Re represent variable impedances which are controlled by'modulating voltages
  • Fig. 3 an arrangement is shown in which impedances R1 and R1 have been replaced by antennas I3 and I5, respectively; R1 and R2 have been replaced by modulators l1 and I9, respectively; and a generator 2
  • the generator is any suitable radio frequency source such as an oscillator or power amplifier, or the like.
  • a modulating voltage is applied to the input of the two modulators by suitable connections to terminals 23. 25. It is now necessary to consider means for varying the impedances R1 and R2 of the modulators I1 and I9 so that they maintain the relation of Equation 3.
  • Fig. 4 an arrangement is shown in which the modulator impedance R2 of Fig. 1 has been replaced by a quarter wave line 21 or equivalent impedance inverting network, having at its outer end a modulator 29 whose impedance is equal to R1.
  • the two impedances R1 and R: are equal to the constant impedance R0.
  • the characteristic impedance Z of the quarter wave line is made equal to the desired input impedance of the system R0.
  • impedances R1, R2, or the specific value R represent either the impedance of an antenna, or of a dissipating network. If two antennas are used they preferably have different directional characteristics so that a modulated field is produced as the output is shifted from one to the other. If a single antenna and a dissipating network are used, the antenna may be nondirectional, since the total output is divided alternately between a nonradlating network and the antenna.
  • Figs. 6 and 7 Various modifications of circuit arrangements may be employed. Two of which are illustrated in Figs. 6 and 7. The arrangements illustrated employ several quarter wave lines, or their equivalent, and may be convenient for various reasons.
  • one modulator R1 is connected in series with the antenna impedance R0 and in series with a quarter wave line 33.
  • a second line 35 is connected in series with line 33.
  • the second line is similar to the first except that it includes the additional impedance inverter 21.
  • each antenna, or the antenna and the dissipating network has been removed from the generator terminals 9, ll.
  • Fig.- 7 represents an equivalent arrangement in which similar apparatus is designated as before and will usually be the preferred arrangement.
  • Fig. 8 is the schematic diagram of a modulator which may be employed in connection with this invention.
  • the modulator comprises a pair of triode tubes 31, 39 whose grid and cathode electrodes are connected together.
  • the input modulating potential is applied between the cathode and grid electrodes.
  • the anode electrodes are returned to cathode through suitable choke coils 43 and 45.
  • the impedance between the two anode electrodes is a function of the applied modulating voltage, and corresponds to the impedance R1.
  • Two such modulators are utilized, illustrated at [1, I 9, in Fig. 3, for example, and their inputs are connected in parallel. While I have illustrated a specific modulator, this is merely by way of example, as other types will be apparent to those skilled in the art.
  • a modulator operating.on the phase opposition principle in which radio frequency voltages are produced in series with the two antennas, the phase of said voltages with respect to that impressed across the terminals 9, I I being varied by the modulating potential.
  • the constant impedance system has many applications. For example, it may be used to provide a readily variable source of radio frequency voltage in connection with a signal generator. The output voltage could be taken across resistor R1 while resistor R: would be within the device. Because of its constant impedance, the tendency to cause the oscillator frequency to drift as the output is varied is greatly reduced.
  • the system is useful in many applications which require controlled variation of a current, alternating or direct, in response to a signal.
  • the controlling signal may be either a voice representing voltage or a regular or intermittent impulse. Relays may be operated by the voltages across the fixed resistors, and the device is therefore useful as a switching relay.
  • a constant impedance load device including separate current paths, one of said paths comprising serially connected fixed and variable impedances, and the other of said paths including a fixed impedance and a variable impedance, said fixed impedances having equal values, one of said variable impedances being connected in series with said fixed impedance through an impedance inverter, and means for varying said variable impedances in like sense and amount to wary the relative impedances of said paths and to maintain constant the input impedance of said load device.
  • a constant impedance load device including parallel current paths, each 01 said paths including in series a fixed and a variable impedance, and means for varying the impedance of said paths in accordance with the equation where R1 is the instantaneous impedance of the variable portion of-one oi said paths, R2 is the instantaneous impedance of the variable portion of the other of said paths, and R0 is the fixed impedance portion of each or said paths.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Variable-Direction Aerials And Aerial Arrays (AREA)
  • Transmitters (AREA)
  • Plasma Technology (AREA)
  • Waveguide Aerials (AREA)
US275370A 1939-05-24 1939-05-24 Modulating system Expired - Lifetime US2295351A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
NL58726D NL58726C (fr) 1939-05-24
US275370A US2295351A (en) 1939-05-24 1939-05-24 Modulating system
GB9216/40A GB540804A (en) 1939-05-24 1940-05-24 A constant impedance load device, particularly for modulating systems
CH219821D CH219821A (de) 1939-05-24 1941-01-13 Zweipol-Netzwerk mit konstanter Impedanz bei teilweise veränderlichen Zweigimpedanzen.

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US275370A US2295351A (en) 1939-05-24 1939-05-24 Modulating system

Publications (1)

Publication Number Publication Date
US2295351A true US2295351A (en) 1942-09-08

Family

ID=23051996

Family Applications (1)

Application Number Title Priority Date Filing Date
US275370A Expired - Lifetime US2295351A (en) 1939-05-24 1939-05-24 Modulating system

Country Status (4)

Country Link
US (1) US2295351A (fr)
CH (1) CH219821A (fr)
GB (1) GB540804A (fr)
NL (1) NL58726C (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2498059A (en) * 1947-12-11 1950-02-21 Bell Telephone Labor Inc Modulation of high-frequency generators
US2543827A (en) * 1948-12-30 1951-03-06 Rca Corp Percentage modulation control network
US2623993A (en) * 1950-09-12 1952-12-30 Westinghouse Electric Corp Amplitude modulator with double yield
EP0179591A2 (fr) * 1984-10-12 1986-04-30 AT&T Corp. Technique d'amélioration du fonctionnement d'un système radio pendant un fading

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2498059A (en) * 1947-12-11 1950-02-21 Bell Telephone Labor Inc Modulation of high-frequency generators
US2543827A (en) * 1948-12-30 1951-03-06 Rca Corp Percentage modulation control network
US2623993A (en) * 1950-09-12 1952-12-30 Westinghouse Electric Corp Amplitude modulator with double yield
EP0179591A2 (fr) * 1984-10-12 1986-04-30 AT&T Corp. Technique d'amélioration du fonctionnement d'un système radio pendant un fading
EP0179591A3 (fr) * 1984-10-12 1986-12-17 AT&T Corp. Technique d'amélioration du fonctionnement d'un système radio pendant un fading

Also Published As

Publication number Publication date
GB540804A (en) 1941-10-30
CH219821A (de) 1942-02-28
NL58726C (fr)

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