US2049143A - Phase modulation - Google Patents

Phase modulation Download PDF

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Publication number
US2049143A
US2049143A US602487A US60248732A US2049143A US 2049143 A US2049143 A US 2049143A US 602487 A US602487 A US 602487A US 60248732 A US60248732 A US 60248732A US 2049143 A US2049143 A US 2049143A
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Prior art keywords
tubes
phase
circuit
electrodes
frequency
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US602487A
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English (en)
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George L Usselman
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RCA Corp
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RCA Corp
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Priority to US602487A priority Critical patent/US2049143A/en
Priority to DER87653D priority patent/DE609327C/de
Priority to GB9999/33A priority patent/GB411638A/en
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    • HELECTRICITY
    • H03ELECTRONIC CIRCUITRY
    • H03CMODULATION
    • H03C3/00Angle modulation
    • H03C3/10Angle modulation by means of variable impedance
    • H03C3/24Angle modulation by means of variable impedance by means of a variable resistive element, e.g. tube
    • H03C3/26Angle modulation by means of variable impedance by means of a variable resistive element, e.g. tube comprising two elements controlled in push-pull by modulating signal

Definitions

  • This invention relates to a method of and means for impressing phase modulations on radio waves or oscillations to be transmitted, and in particular to an improved method of and means for accomplishing phase modulation by the use of modulator tubes having output, as well as input, electrodes connected in push-pull relation.
  • phase modulated high frequency carriers are less subject to fading elfects than the same carrier modulated otherwise. Further, that satisfactory transmission of short waves which are phase modulated can be carried on over distances heretofore impossible with the use of short Waves modulated in amplitude or frequency.
  • phase modulated waves are less subject to the effects of fading than the same waves modulated otherwise and since phase modulated short waves can be transmitted over distances which cannot be covered by waves modulated otherwise, the practical application of the same is of the greater importance.
  • the use of phase modulated signals in diversity reception enhances materially the quality of said reception.
  • the primary object of this invention is to provide an improved modulation method and system especially applicable to situations wherein a two line balanced input and two line balanced output is required.
  • An advantage of a push-pull phase modulator as disclosed in the present invention is that neutralizing of the plate to grid capacities of the amplifying modulator may be accomplished more satisfactorily than it can be done in phase modulators known heretofore in the art whether a single tube per stage is used or symmetrical tubes are used.
  • the above objects are attained in accordance with the present invention by the supplying of excitation voltages from a suitable oscillator to the grids of two modulator tubes through a phase changing device connected in series with each grid.
  • the anodes of the two modulator tubes are connected to a common oscillating tank circuit.
  • This oscillating tank circuit can function at only one frequency and phase at any given instant but the phase of oscillations may be shifted from time to time by giving one tube more power input than is given to the other tube. This is accomplished by changing the bias to the grids of the modulator tubes.
  • the phase shift in the modulator tubes changes or modulates the phase of the output frequency of the transmitter.
  • phase modulated transmitters constructed in accordance with the present invention the frequency and the power output remain constant but the phase of the energy is advanced or retarded relative to a normal constant frequency about an average phase angle.
  • the rate at which the phase is advanced or retarded depends upon the frequency of the modulating potentials.
  • the amount of phase advance or retardation will depend upon the amplitude of the modulating potentials and also upon the amount of xed phase shift caused by the phase changing devices in the grid circuit.
  • Figure 1 illustrates the basic idea of the present invention
  • Figure 2 shows a modification of the arrangement of Figure 1.
  • A is a balanced type constant frequency oscillator of any known type in use today, as, for example acrystal controlled oscillator of the type disclosed in Hansells United States application Serial No. 540,310, filed May 27, 1931, or any other oscillator in use by radio engineers today, or a long line controlled oscillator such as disclosed by James L. Finch and James W. Conklin in their United States application Serial No. 363,660, i'lled May 16, 1929, or any other long line frequency control generator known to radio engineers.
  • the lines P and Q connect the oscillator output to a tuned grid tank circuit H by way of capacities I and 2 respectively.
  • the lines P and Q should be of substantially equal electrical length and similar in other characteristics relative to each other, to ground, etc., in order that oscillations of substantially equal amplitude reach the tank circuit H over each line from the generator A.
  • the tank circuit H comprises a symmetrically tapped inductance 3 andV variable tuning capacity Il. The center point of the tank circuit 3 is grounded through a blocking condenser W as shown.
  • One terminal of the tank circuit H is connected through a phase retarding means in the form of an inductance I to the grid 6 of thermionic modulator tube 1, while the other terminal of the inductance 3 ofV circuit H is connected through a phase advancing means in the form of a capacity J to the grid 8 of a thermionic modulator tube I0.
  • phase retarding inductance I adjacent the grid 6, is also connected to a resistance R1, the other terminal of R1 is grounded for radio frequency by means of a blocking condenser M connecting the terminal of resistance R1 to the cathode I2 of tube 1.
  • the terminal of the phase advancing capacity J adjacent the grid 8 is'also connected to one terminal of resistance R2, the other terminal of R2 is connected by means of radio frequency by-passing condenser N to the cathode I4 of tube I0.
  • the low potential ends of resistorsRi and R2 are also connected in phase opposition to the terminals of a tapped secondary winding I6 of transformer T, the primary winding I8 of which is connected to an audio frequency modulating source B as shown.
  • the cathode electrodes I2 and I4 of modulator tubes 'I and Iii respectively are connected tothe battery or power source 20 as shown.
  • Ai constant direct current biasing potential is applied through the secondary winding I6 and resistances R1, R2 to the control electrodes 6 and 8 of modulator tubes 'I and I0 respectively by means of a connection I9 between the negative terminal of'V the source 2l'and the center point on the lsecondary winding I6 of transformer T.
  • a tank circuit 22 comprising a capacity 2I and inductance 23, is tuned to normally oscillate at the frequencyof the wave or oscillations to be modulated.
  • the anodes 24, 26 of modulator tubes 'I and I0 respectively are connected in phase opposition. This is accomplished by connecting the anodes 24 and 26, as shown, to opposite ends of the oscillation circuit 22.
  • the center point of the inductance 23 is connected to the positive terminal of the source 20 so that a charging potential is applied from the source 2E) to the anodes 24 and 26 respectively. Radio frequency oscillations are shuntedaround the source 2i!
  • Radio frequencyA oscillations appearing in the tank circuit 22 are prevented from passing through the source'20 by means of a capacity 2'1.
  • the phase modulated oscillations appearing in the tank circuit 22 may be utilized in any manner. For example, they may be fed to an amplier and/or frequency multiplier F by way of capacities U ⁇ and V in the balanced lines connected to the output of the tank circuit C.
  • the fre- Y quency multiplier may be of'any type, as, for example, as shown -in Hansell, United States Patent No. 1,878,308; or Green, United States Patent No. 1,878,309; or any v other frequency -multiplier known to radio engineers. In general, pure phase modulation is accomplished by this arrangement as disclosed. However, in the event thatthere has been .some Vamplitude modulation taking place,I Vthe balanced lines, ⁇ including.
  • the condensers U and V may be caused to feed the energy to the amplifier and/or multiplier F by way of an amplitude limiter device D. Since this amplitude limiter device D and amplifier or frequency multiplier F per se form no part of the present invention, a detailed description thereof is thought unnecessary here.
  • oscillator A is supplying power at constant frequency to the input tank circuit H.
  • This power is supplied to the grid tank circuit H, through the balanced lines I and 2, and blocking condensers P and Q.
  • Oscillations will be set upon in tank circuit H, the tuning or response of which is determined by inductance 3 and capacity 4.
  • Excitation voltage at constant frequency will be supplied from the tank circuit H through inductance I and condenser J to the grids 6 Yand 8 respectively of modulator tubes 'I and Il) respectively in substantial phase opposition -or in push-pull fashion.
  • phase of the Voltage excitation applied to the grid 6 of modulator tube 'I will be retarded to some extent by the inductance I, while the phase of the voltage excitation applied to the grid 8 of modulator tube IIJ will be advanced to some extent by the capacity J.
  • the amount of retardation and advancement in the phase of the excitation applied tothe grids of these tubes may be changed and will depend upon the retarding or inductive 0 value given to the inductance I and the advancing or capacitive value given to the condenser J, and also on the value ofthe resistance of resistors R1 and R2 respectively.
  • each side of the grid circuit H should be kept balanced, then if both modulator tubes 'I and IB have the same direct current bias, which is the case when no modulation energy is being supplied from B, the power supplied byeachmodulator tube to the tuned tank circuit 22 will be equal and the potential oscillations in circuit 22 will have a constant phase which will coincide with the average phase position of the excitation voltage, keeping in mind that the oscillations in circuit C are of constant frequency.
  • the bias applied to the electrodes 6 and B of tubes 'I and I0 respectively will vary in phase opposition and the tube having the lower bias at any particular instance will supply the most power to the tuned tank circuit 22. Since the excitation to the grids 6 and 8 of the two modulator tubes l and Il] respectively has a phase difference the power supplied to the tank circuit 22, by the anodes 24, 26 of the two modulator tubes 'I and I0, will have a phase difference. The phase of the oscillations appearing in circuit 22 will change or approach that of the tube having the lower grid bias and therefore supplying the more power.
  • the amount of phase change in the circuit 22 l will be substantially proportional to the difference in power delivered by the tubes 'I and I0 to the circuit 22. It is obvious, however, that there may be no greater phase shift in the tank circuit 22 than there is phase difference of excitation applied to the grids of tubes 'I and I0 respectively.
  • This circuit also provides all of the advantages attendant on the use of push-pull tubes since the plates or anodes are connected so that they deliver power in push-pull fashion and in phase opposition.
  • This circuit also readily lends itself to grid neutralization and to other schemes of balancing applied to radio frequency circuits.
  • Figure 2 is shown a modication of the arrangement of Figure 1.
  • screen grid tubes are used, thereby eliminating ⁇ the necessity of neutralizing the inter-electrode capacity as was the case in the arrangement of Fig. l.
  • This arrangement also differs from the arrangement shown in Figure 1 in that the audio frequency modulation is introduced, as shown, on the screen grid electrodes of the modulator tubes instead of on the the present arrangement are amplified before be-V ing used to phase modulate the carrier.
  • the oscillation generator A of Figure 2 and the means by which oscillations at a carrier frequency, the phase of which are alternately advanced or retarded an amount determined by the inductance I and capacity J, are caused to appear in the tank circuit 22, is the same as the corresponding elements and means of the arrangement of Figure 1.
  • the tubes 1 and i9 are ofvth screen grid type and the modulating frequencies are impressed on the screen grid electrodes 36 and 31 respectively to thereby vary the conductivity of the tubes 1 and I9 respectively, and in that manner modulate the phase of the carrier ⁇ oscillations at a rate determined by the frequency of the modulating potentials and by an amount determined by the amplitude of the modulating potentials limited,Y of course, by the alternating phase advancing and retarding effect imparted to the carrier frequency oscillations by the inductance I and capacity J.
  • the modulating potentials are applied to screen grid electrodes 36, 31 from the anodes 34, 35 respectively of'a pair of thermionic tubes 28, 29 having their anodes connected in parallel through resistances R3, R4 to a point on a potentiometer 38 in parallel with source 29.
  • the modulating potentials obtained from the source B are impressed on charging potentials by way of resistances R3, R4V respectively, which also supply charging poten-V tial for the anodes 34, 35 of the tubes 28 and 29 respectively.
  • Biasing potential for the tubes 28 and 29 is supplied by way of a lead I9 connected with the source 29 and the midpoint of winding I6.
  • Biasing potential for the grid electrodes of the tubes 1 and I ilV respectively issupplied by way of 'a lead I9 connecting the resistances R1, Rz to a point on the potentiometer 39 connected in parallel'with the source 20.
  • the modulating frequency potentials are applied in phase opposition to'the control electrodes A32 and 33, of tubes 28 and Z9 respectively. These tubes become alternately more conducting and less conducting at a degree and-frequency determined by the intensity and frequency of the modulating potentials.
  • tube 28 becomes more conductive the anode circuit thereof, including the resistance R3, draws more current, which causes an increase in voltage drop across resistor R3.
  • the voltage drop across Y a resistor opposes the potential which causes the current to flow, so that an increase in current through resistor R3 decreases the positive potential on the screen grid electrode 31.
  • This potential variation applied to screen grid 31 governs the amount of energy supplied to the tank circuit 22 connected with the anode 26 of tube IU. f In this case the energy supplied by tube i9 is reduced.
  • tube 29 is rendered less conductive so that less current ows in resistance R4.
  • This causes less voltage dro-p in resistance R4, which results in an increase of positive potential applied to the screen grid electrode 36 of tube 1, therebycausing the anode 24 of tube 1 to draw more current' and to supply more energy to the tank circuit 22.
  • the energy in tank circuit 22 is mostly from tube 1, the phase of the energy supplied from tube 1 to a great extent determines the phase of the energy in the tank circuit.V
  • the modulating potentials applied to-the secondary windings I6 reverse in sign the reversed operation takes place.
  • Tube '29 now draws more current while tube 28 draws less current so that the positive potential applied to the screen grid electrode v36 decreases and the positive potential applied to the screen grid electrode 31 increases.
  • Tube 1 now becomes less conductive and tube I9 becomes more conductive.
  • the energy in the tank circuit 22, therefore, is mostly. energy supplied from the anode 26 of tube i9.
  • the phase of the energy intank circuit 22, at this particular instant is determined to a great extent by the phase of the energy supplied from the tube I9.
  • the high frequency oscillations supplied from A, through high frequency phase shifting means I and J to tubes 1 and I9 respectively are modulated in phase at a degree and rate ⁇ determined by the intensity and frequency of the modulatingpotentials produced in B.
  • the object of this arrangement except as otherwise vindicated above, is thesame as the object of the arrangement shownin Figure l.
  • the present arrangement includes all of the4 advantages of the arrangement of Figure 1 and, in addition thereto, eliminates the necessity of the use of neutralizing capacities to prevent reaction between input and output circuits of the modulator tubes.
  • the amount of desired sideband energy and the amount of undesired sideband energy, resulting from the phase modulation of the carrier at signal frequency accomplished inthe devices of Figures 1 and 2, depends in part on the amplitude of thecarrier orof the modulating potentials. By regulating the amplitude of either the carrier or the modulating potentials, the amount of the undesired sideband or ,components may be diminished or increased at will ⁇
  • the amplitude ofi the modulating Vpotentials at the source B in either of the arrangements shown in V Figure- 1 or 2, or by adjusting the lead I9 along the potentiometer 39 of Figure 2 to control the amplification of the modulation frequency amplifiers 28 and19
  • the amplitude of the modulating potentials ⁇ acting on the impedances of tubes 'l and lll may be regulated, thereby controlling the amount of desired and undesired sideband energy appearing in the circuit 22.
  • the amplitude components and other undesired energy of the same nature may be removed in the unit D.
  • Transmitting means comprising a source of oscillations, a pair of thermionic tubes of the screen grid type, connections between said source and the control electrodes of said tubes for applying oscillations in phase opposition to the control electrodes of said tubes, means for phase modulating said oscillations comprising phase shifting means in each of said connections, a tank circuit connecting the .anodes of said tubes in push-pull relation, a source of modulating potentials, and means for impressing the modulating potentials in phase opposition on the screen vgrid electrodes of said tubes.
  • Means for amplifying and phase modulating high frequency energy comprising, a pair of thermionic tubes of the screen grid type having their input electrodes energized in phase opposition by carrier frequency ⁇ potentials, means for retarding the phase of the carrier ⁇ frequency potentials applied to'one of said grid electrodes, and means for advancing the phase of the carrier frequency potentials applied to the other cf said grid electrodes, a tank circuit connected between the anodes of said tubes, and means-for impressing modulating potentials in phase opposition on the screen grid electrodes of said tubes.
  • Means for impressing phase Amodulations at signal frequency on high frequency oscillations comprising, a pair of thermionic tubes of the screen grid type, means for impressing high frequency oscillations in opposition on the control electrodes of said tubes, phase shifting means interposed between the control electrodes of one of said tubes 'and said impressing means, a load circuit connected between the anodes of said tubes, a pairv of thermionic amplifiers, means for impressing modulating frequencies on the control electrodes of said amplifiers in phase opposition, a connection between the anode of each of said amplifiers and the Screen grid in one of said screen grid tubes, and means for connecting the andoes of said last named tubes to aV source of potential.
  • a source of carrier frequency oscillations of a phase modulator comprising, a pair of thermionic tubes having their control grids connected by reactances of different electrical characteristic to said source of oscillations, their anodes connected in push-pull relation by an output circuit ⁇ and their anode to' control grid capacities neutralized by variable capacities, a source of modulating potentials connected by way of thermionic repeaters in phase opposition to the impedances of the tubes in said modulator wherebycarrier oscillations from said source are modulated in phase at signal frequency and inadvertently modulated in amplitude, an amplitude limiter connected with the output circuit of said tubes whereby the amplitude modulation inadvertently accomplished is removed from the modulated energy, and a frequency multiplier coupled with said limiter to increase the degree of phase modulation accompli-shed.
  • Transmitting means comprising the combination of, a constant frequency oscillation generator, a pair of modulator tubes each having control grid a-nd anode electrodes, an input circuit, phase shifting reactances of different character connecting the control grids of said modulator tubes in push-pull relation by waykof said input circuit, an output circuit connecting the anodes' potentials to the control grid electrodes oi each of said tubes and energizing potentials to the anodes of each of said tubes, and means for phase modulating the oscillations from said oscillation generator comprising a balanced means for differentially applying modulating potentials to like electrodes in each of said tubes.
  • a phase modulating means comprising, a pair of thermionic tubes each having anode and control electrodes, a tank circuit adapted to be energized by carrier frequency oscillations, a reactance connecting one terminal of said tank circuit to the control electrodes of one of said tubes, a reactance connecting the other terminal of said tank circuit to the control electrode of the other of said tubes to excite the same in out of phase relation, a circuit connecting the anodes of said tubes in push-pull relation, a source of modulating potentials, and a circuit for applying said potentials from said last named source in phase opposition to like electrodes in each of said tubes.
  • a constant frequency oscillator a modulator stage of the thermionic tube type having input electrodes and output electrodes connected in push-pull circuits each of which includes an inductance, and a load circuit, a balanced line connecting said oscillator to points on the inductance connected with the input electrodes of said tubes, a balanced line connecting points on the inductance connected with the output electrodes of said modulator tubes to said load circuit, phase shifting means connected with the input electrode of each of said modulator tubes, said phase shifting means being of different character, a source of modulating potentials, and a circuit for applying modulating potentials from said source in phase opposition to like electrodes in each of said tubes.
  • a constant frequency oscillator a modulator stage including, thermionic tubes connected in push-pull relation by input and output circuits each circuit including an inductance, and a load circuit, a balanced line connecting said oscillator to points on the inductance in the input circuit of said modulator stage, a balanced line connecting points on the inductance in the output circuit of said modulator stage to said load circuit, an inductive reactance connected between the inductance in said input circuit and the input electrode of one of said tubes in said stage, a capacitive reactance connected between the inductance in said input circuit and the input electrode in the other of said tubes in said modulator stage, and a circuit for applying modulating voltages in phase opposition to the impedance between two electrodes of each tube in said modulator stage.
  • Means for impressing phase modulations at signal frequency on high frequency oscillations comprising, a pair of thermionic tubes of the screen grid type, each having anode, cathode, control grid and screen grid electrodes, a circuit for impressing high frequency oscillations in phase opposition on the control grids of said tubes, phase shifting reactances interposed between the control grid of each of said tubes and a different point on said impressing circuit, a load circuit connected with the anodes of said tubes, a pair of thermionic amplifier tubes each having an anode and a control grid, circuits connected with the control grids of said amplier tubes for impressing modulating potentials in phase opposition on the control grids of said amplifier tubes, and connections between the anode of one of said amplier tubes and the screen grid in one of said screen grid tubes and between the anode of the other of said amplifier tubes and the screen in the other of said screen grid tubes.
  • a pair of thermionic tubes each having a control grid and a cathode, a tank circuit adapted to be energized by high frequency oscillatory energy, an inductive reactance connecting one terminal of said tank circuit to the control grid of one of said tubes, a capacitive reactance connecting the other terminal of said tank circuit to the control grid of the other of said tubes, a connection between a point on said tank circuit and the cathodes of said tubes whereby said control grids are excited substantially in phase opposition by oscillatory energy in said tank circuit, and a source of modulating voltages connecting the control grids of said tubes in phase opposition.

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US602487A 1932-04-01 1932-04-01 Phase modulation Expired - Lifetime US2049143A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
US602487A US2049143A (en) 1932-04-01 1932-04-01 Phase modulation
DER87653D DE609327C (de) 1932-04-01 1933-04-01 Phasenmodulierte Senderschaltung
GB9999/33A GB411638A (en) 1932-04-01 1933-04-03 Improvements in or relating to modulated carrier wave transmitters

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2508270A (en) * 1946-01-22 1950-05-16 John M Kaar Phase shift modulation system

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2508270A (en) * 1946-01-22 1950-05-16 John M Kaar Phase shift modulation system

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DE609327C (de) 1935-02-12
GB411638A (en) 1934-06-14

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