US1830166A - Frequency modulation - Google Patents

Frequency modulation Download PDF

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Publication number
US1830166A
US1830166A US264102A US26410228A US1830166A US 1830166 A US1830166 A US 1830166A US 264102 A US264102 A US 264102A US 26410228 A US26410228 A US 26410228A US 1830166 A US1830166 A US 1830166A
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United States
Prior art keywords
frequency
current
saturation
source
circuit
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Expired - Lifetime
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US264102A
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English (en)
Inventor
Clarence W Hansell
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RCA Corp
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RCA Corp
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Priority to BE359252D priority Critical patent/BE359252A/xx
Application filed by RCA Corp filed Critical RCA Corp
Priority to US264102A priority patent/US1830166A/en
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Publication of US1830166A publication Critical patent/US1830166A/en
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03C—MODULATION
    • H03C3/00—Angle modulation
    • H03C3/10—Angle modulation by means of variable impedance
    • H03C3/12—Angle modulation by means of variable impedance by means of a variable reactive element
    • H03C3/18—Angle modulation by means of variable impedance by means of a variable reactive element the element being a current-dependent inductor
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/02—Amplitude-modulated carrier systems, e.g. using on-off keying; Single sideband or vestigial sideband modulation
    • H04L27/04—Modulator circuits; Transmitter circuits

Definitions

  • This invention relates to frequency modulation, and more particularly to a method and means for obtaining frequency modulation which will accurately follow variations 1n a control current.
  • a change in the magnitude of the control current changes 'the saturation of the saturable impedance, or magnetic frequency wobbler, and this causes a change in impedance which finally results in changing the natural frequency of the frequency control circuit.
  • llt is exceedingly desirable, and in fact, 1n the case of multiplexing, essential, that the frequency shift produced'by the magnetic frequency wobbler be in linear relation to the change in magnitude of the control current.
  • the range of wobble should be limited, and should be located .at a relatively straight portion of the magnetization curve of the wobbler. This may be done by feeding to the saturation winding of the wobbler a steady current proper in magnitude to cause the desired mean saturation.
  • This requires an absolutely constant supply of current, much more so than is available .from an ordinary power supply line, and t0 irovide a source of constant current in combination-with a frequency Wobbler is a further object of my invention.,
  • I supply direct. potential from a suitode current is used as the normal saturation current for the wobbler.
  • an intermediate amplifier preferably the same electron emission tube as was already em loyed for obtaining constant direct current fJor the normal saturation
  • FIG. 1 there is an oscillator tube 2, with which is associated regeneratively coupled coils 4 and 6, which form a portion of a frequency control circuit 8, the remainder of which comprises a tuning condenser 10, the radio frequency windings 12 and 14 of a magnetic frequency wobbler 16, and blocking condensers 18 and 20, which shunt radio frequency currents by the sources of direct anode and control electrode potential.
  • a tuning condenser 10 the radio frequency windings 12 and 14 of a magnetic frequency wobbler 16
  • blocking condensers 18 and 20 which shunt radio frequency currents by the sources of direct anode and control electrode potential.
  • the magnetic frequency wobbler 16 comprises two similar cores 28 and 30, each of which is composed of a stack of thin laminations in the form of annular disks.
  • the radio frequency windings 12 and 14 are wound around an annular portion of the cores, that is, they are threaded through the center and around the outside of each of the cores, so that magnetic flux flows around the annular rings.
  • the coils 12 and 14 are connected in series with each other and with the tuned frequency controlling circuit 8.
  • the control current is applied to the saturation windings 32 and 34, which are wound like the radio frequency windings, and which also are connected in series, but which are connected in opposite sense to the radio frequency windings, so that radio frequency ener induced in them is neutralized, the coils eing connected relatively in opposition.
  • the steady saturation current for the saturation windings 32 and 34 is obtained from the anode circuit of an electron emission tube 36, energized by connection at points 38 and 40 to a potentiometer resistance 42, which is connected across a direct current line 44, and optionally through an intermediate control rheostat 46.
  • the control electrode of the tube 36 is connected, as shown, to the potentiometer 42 at a point 48 which is more negative than the point 38 to which the filament is connected.
  • the anode current may be kept perfectly constant. Since the point 48 will not, in general, provide the correct grid bias when properly located for current correction, a C battery 50 may be provided, in order to obtain the desired anode current. This battery will have long life at constant voltage because there is no grid current fiow.
  • the primary control or modulating current may be superimposed on the normal saturation current by connection at any suitable point in the circuits described, but preferably is coupled by means of a suitable transformer 54 to the input circuit of the vacuum tube 36.
  • the control or modulation current may be speech, from a microphone 56 in series with a direct current source, or code signalling by means of alternating current from a generator 57 controlled by a key 58.
  • a plurality of such alternating current circuits of differing frequencies may be used to multiplex, as is more fully disclosed in my copending application Serial Number 212,192, filed Aug. 11, 1927.
  • the frequency modulated energy may be taken from either or both of the coils 4 and 6, and after suitable amplification, directly used for transmission.
  • the intermediate .frequency energy is fed from the coils 4 and 6 to the coil 66, which is coupled to the modulator tubes 66 in series.
  • the output coil 70 is connected to the tube anodes in series also, in consequence of which the carrier components oppose in the halves of the coil 70 and are neutralized. @f the side bands the filter 72 selects one, and this is amplified in a power amplier T4. rllo insure constant energy output a limiter may be used, and preferably the power amplifier 74 is itself made to act as a limiter, by increasing the amplitude of the excitation on cach stage beyond the point Where an increase in excitation causes appreciable increase in output. This incidentally is the adjustment which is desirable to secure high energy efficiency in an amplifier which is to be operated at constant output or with keyed modulation. rlThe amplifier output is radiated in a suitable antenna circuit 7 6.
  • the method of causing the frequency variations obtained from a magnetic frequency wobbler. the normal saturation current for which is fed from a direct current source, to accurately follovi7 variations inthe control current despite variations in the potential of the direct current source which includes applying potential from the source to the anode circuit of an electron emission tube, applying potential from the same source to the control electrode of the tube in opposite sense and proper proportion to counteract the effect of the potential fluctuations of the source, and using the resulting constant anode current as the normal saturation current for the magnetic frequency wobbler.
  • the method of causing the frequency variations obtained from a magnetic frequency wobbler to accurately follow variations in the control current despite losses in the wobbler which includes applying the control current to the wobbler through an intermediate amplifier, and feeding a portion of the output energy of the amplifier to the input thereof in proper phase and degree to counteract the effect of losses in the wobbler.
  • the method'of causing the frequency variations obtained from a magnetic frequency wobbler to accurately follow7 variations in the control current which includes applying potential from a direct current powersource to the anode circuit of a vacuum tube, applying potential from the same source to the control electrode of the tube in opposite sense and proper proportion, to counteract the effect of potential fluctuations of the source, using the resulting constant anode current' as a normal saturation current for the wobbler, applying the wobble control current to one of the circuits of the tube, and' feeding a portion of the anode circuit energy to the control electrode circuit of the tube in proper phase and degree to counteract the effect of losses in the wobbler.
  • a frequency modulator comprising a tuned frequency controlling circuit, a saturable impedance in said tuned circuit, a saturation Winding associated with the core of the saturable impedance for controlling the saturation thereof, a source of control current coupled to the saturation Winding, and means to apply thereto an additional current variation of proper magnitude'and phase t0 counteract the effect of losses in the saturable impedance.
  • a frequency modulator comprising a tuned frequency controlling circuit, a saturable impedance in said tuned. circuit, a saturation Winding associated with the core of the saturable impedance for controlling the saturation thereof. a source of constant cunrent coupled to said Winding to establish a desired normal saturation, a source of control ,current coupled to the saturation Winding,
  • a frequency modulator comprising a tuned frequency controlling circuit, a saturable impedance in said tuned circuit, a saturation Winding associated with the core of the saturable impedance for controlling saturation thereof, a direct current source, a resistance connected thereto, an electron emission tube having its anode and control electrode circuits so coupled to the resistance that the normal anode current remains constant despite variations in the potential of the source, means connecting the saturation Winding in series with the anode circuit of the tube, and a source of control current coupled to the input circuit of the tube.
  • a frequency modulator comprising a tuned fre uency controlling circuit, a saturable impe ance in said tuned circuit, a saturation Winding associated with the core of the saturable impedance for controlling the saturation thereof, an electron emission tube having anode and control electrode circuits, means coupling the saturation Winding to the anode circuit, a source of control current, means coupling the source to the control electrode circuit, and means regeneratively coupling the control electrode and anode circuits to compensate for losses in the Wobbler.
  • a frequency modulator comprising a tuned frequency controlling circuit, a saturable impedance in said tuned circuit, a saturation Winding associated with the core of the saturable impedance for controlling the saturation thereof, an electron emission tube having anode and control electrode circuits, means coupling the saturation winding to the anode circuit, a source of direct current, a resistance connected thereto, means so coupling the anode and control electrode circuits to said resistance that the normal anode current remains constant despite variations in the I tential of the source, a source of control current coupled to the control electrode circuit of the tube, and mea-ns regeneratively coupling the control electrode and anode circuits of the tube to compensate for losses in the Wobbler.
  • a frequency modulation transmitter comprising an intermediate frequency oscillator having a tuned frequency controlling circuit, a saturable impedance in said turned circuit, a saturation Winding 'associated with the core of the saturable impedance for controlling the saturation thereof, a source of modulation current coupled to the saturation Winding, a source of constant high frequency energy, means for combining the intermediate and high frequency energies to produce side band energy, and means for radiating a portion of the side band energy so produced.
  • a frequency modulation transmitter comprising an intermediate frequency oscillator having a tuned frequency controllin circuit, a saturable impedance 1n said tune circuit, a saturation Winding associated with the core of the saturable impedance for controlling ⁇ the saturation thereof, a direct current source, a resistance connected thereto, an electrony emission tube having its anode and ⁇ control electrode circuits so cou led to the resistance that the normal anode current remains constant despite variations in the potential of the source, means connecting the saturation winding in series with the anode circuit of the tube, a source of modulation current coupled to one of the circuits of the tube, a source of constant high frequency energy, means for combining the high frequency energy and intermediate frequency energy from the intermediate frequency oscillator to produce side band energy, means for amplifying a portion of the side band energy, and means for radiating the amplified side band energy.
  • a frequency modulation transmitter comprising an intermediate frequency oscillator having a tuned frequency controlling circuit, a saturable impedance in said tuned circuit, a saturation Winding associated with the core of the saturable impedance for controlling the saturation thereof ⁇ an electron emission tube having anode and control electrode circuits, means coupling the saturation-Winding to the anode circuit, a source of direct current, a resistance connected thereto, means so coupling the anode and control electrode circuits to said resistance that the normal anode current remains constant despite variations in the potential of the source, a source of modulation current coupled to the control electrode circuit of the tube, means regeneratively coupling the coutrol electrode and anode circuits of the tube to compensate for losses in the Wobbler, a source of constant high frequency energy, means for combining the high frequency energy and intermediate frequency energy from the intermediate frequency oscillator to produce side band energy, means for amplifying a portion of the side band ener and means for transmitting the ampli ed side band energy.
  • a frequency modulation transmitter comprising an intermediate frequency oscillator having 'a frequency controlling circuit, a saturable impedance in said frequency controlling circuit, a saturation Winding associated with the core of the saturable impedance for controlling the saturation thereof, a source of modulation energy coupled to the saturation Winding, a source of constant high frequency energy, means for combining the high frequency energy with energy from the frequency controlling circuit, and means for transmitting some of the combined energy.
  • a frequency modulation transmitter comprising an intermediate frequency oscillator having a frequency controlling circuit, a saturable impedance in said controlling circuit, a saturation Winding associated With the core of the saturable impedanceifor controlling the saturation thereof, a diiect current source, an impedance connected thereto, an electron emission tube having its anode and control electrode circuits so coupled to said last mentioned impedance that the normal anode current remains constant despite variations in the potential of the source, means coupling the saturation winding with the anode circuit of the tube, a source of modulation energy coupled to one of the circuits of the tube, a source of constant high frequency energy, means for combining ener from the high frequency source and rom the fre uency controllin circuit to produce side (iiand ener and means for transmitting a portion of t e side band energy so roduced.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Power Engineering (AREA)
  • Stabilization Of Oscillater, Synchronisation, Frequency Synthesizers (AREA)
US264102A 1928-03-23 1928-03-23 Frequency modulation Expired - Lifetime US1830166A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
BE359252D BE359252A (enrdf_load_stackoverflow) 1928-03-23
US264102A US1830166A (en) 1928-03-23 1928-03-23 Frequency modulation

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US264102A US1830166A (en) 1928-03-23 1928-03-23 Frequency modulation

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2433361A (en) * 1940-01-20 1947-12-30 Submarine Signal Co Method and apparatus for echo ranging

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2433361A (en) * 1940-01-20 1947-12-30 Submarine Signal Co Method and apparatus for echo ranging

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BE359252A (enrdf_load_stackoverflow)

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