US2248462A - Modulation system - Google Patents

Modulation system Download PDF

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Publication number
US2248462A
US2248462A US324255A US32425540A US2248462A US 2248462 A US2248462 A US 2248462A US 324255 A US324255 A US 324255A US 32425540 A US32425540 A US 32425540A US 2248462 A US2248462 A US 2248462A
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United States
Prior art keywords
phase
output
radio frequency
auxiliary
modulating
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
US324255A
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English (en)
Inventor
Pollack Dale
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
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Filing date
Publication date
Priority to NL60868D priority Critical patent/NL60868C/xx
Priority to US232482A priority patent/US2226942A/en
Priority claimed from US232483A external-priority patent/US2224314A/en
Priority to GB23213/39A priority patent/GB532006A/en
Application filed by RCA Corp filed Critical RCA Corp
Priority to US324255A priority patent/US2248462A/en
Application granted granted Critical
Publication of US2248462A publication Critical patent/US2248462A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
    • H03F1/08—Modifications of amplifiers to reduce detrimental influences of internal impedances of amplifying elements
    • H03F1/14—Modifications of amplifiers to reduce detrimental influences of internal impedances of amplifying elements by use of neutralising means
    • H03F1/16—Modifications of amplifiers to reduce detrimental influences of internal impedances of amplifying elements by use of neutralising means in discharge-tube amplifiers
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
    • H03F1/02—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation
    • H03F1/04—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation in discharge-tube amplifiers
    • H03F1/06—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation in discharge-tube amplifiers to raise the efficiency of amplifying modulated radio frequency waves; to raise the efficiency of amplifiers acting also as modulators
    • H03F1/07—Doherty-type amplifiers

Definitions

  • the current in the antennav of such a transmitter is'varied by the modulating voltage so that the resultant antenna current is the sum of two radio frequency currents during positive peaks of modulation, and is equal to the difference of the two radio frequency currents during negative peaks of the modulating voltage.
  • Vance describes a modulation systemv which provides a new approach to the problem of obtaining efiicient amplitude modulation.
  • the present invention is an improvement of the system therein described.
  • the general system which is employed in theVance application and in the present application; requires the use of a radio frequency power output tube which is designed to supply but one-half the maximum load.
  • An auxiliary tube is called into play to supply an in-phase current which increases the efiective power output during upward peaks of modulation.
  • Downward modulation is accomplished by reversing the phase of the radio frequency current supplied by the auxiliary tube.
  • the auxiliary out of phase current cancels some, or all of the output from the first output tube and thereby reduces the net power which is supplied to the antenna.
  • the present invention is'an improvement over the method described by 'Van'ce', 'i'n that a simplipended claims.
  • a pair of auxiliary power tubes are directly coupled to the antenna. and means are provided for reversing the phase of the radio frequency output of one of the auxto negative peaks of the modulating voltage.
  • t is a further object of this invention to provide a more economical system of modulating a radio frequency carrier.
  • Figure 1 is a schematic drawing of one embodiment of my invention.
  • Figure 2 is a schematic drawing of an alternative embodiment ,of my invention.
  • unmodulated radio frequency energy is supplied to a power output amplifier 3 from a source which is not shown by means of connections to a pair of input terminals 5 and I
  • the amplifier 3 is a power triode amplifier designed in the usual manner but rated at a maximumpower output equal substantially to one-half the desired transmitter output.
  • Anode potential is supplied by a battery 9 which is connected to the anode of amplifier 3 through a radio frequency choke II.
  • the output ,of this amplifier 3 is connected to the input of an impedance inverter I3.
  • the impedance inverter comprises a pair of capacitors I and I1 and an inductor
  • the load circuit which may be an antenna, or the like, is represented by a resistor 2
  • the output of the impedance inverter is connected to the load resistor through a coupling capacitor 23.
  • a low impedance is connected across the output of an impedance inverter, a high impedance effectively appears across the input. The function of this inversion will be explained subsequently.
  • the anode 29 of the first auxiliary triode 25 is connected by means of a coupling capacitor 3
  • the anode 33 of the second auxiliary triode 21 is connected to the anode 29 through a phase inverter circuit 35.
  • the phase inverter circuit consists of a pair of inductors 31 and 39 and three capacitors 4
  • is connected to the anode 33.
  • the junction of the inductor 31 and the output capacitor 43 is connected to the anode 29.
  • the inductors and capacitors which constitute the phase inverter are so chosen that at the frequency of operation the phase of a voltage which is applied across the terminals of capacitor 4
  • This condition is obtained when the circuit constants are chosen so that a half wave resonant filter is obtained, that is the capacitive reactance of' the input and output capacitors is equal to the inductive reactance of the two inductors, and the capacitive 'reactance of the middlecapacitor 45 is equal to one half of this value.
  • Anode potential is supplied by a pair of batteries 41 and 49, or the like, which are respectively connected to the anodes 29 and 33 through radio frequency chokes 5
  • a push pull audio frequency transformer has its secondary 51 connected between the grids Q59 and6l of the auxiliary triodes. Modulating voltage, from a source which is not shown, is
  • Radio frequency energy is also supplied to the two auxiliary triodes.
  • a phase shifting network 61 in series with a lead which connects the radio frequency input termistantially no power is delivered to the load by either of the auxiliary triodes.
  • a modulating voltage is impressed across the terminals of transformer 55 the voltage is impressed on the grid of each auxiliary triode. Due to the push pull connection, however, when the voltage at any instant on the grid 59 of the first auxiliary triode is positive, that on the grid 6
  • a positive modulating impulse therefore, impresses a positive potential on the grid of the first auxiliary triode, permitting it to draw plate current, and to impress a voltage across the load resistor 2
  • a negative modulating impulse causes the second auxiliary triode 21 to draw plate current and the amplified output voltage which is impressed across the load resistor 2
  • the impedance inverter I3 which is connected between the output tube 3 and the load, reflects in opposite sense the change in load impedance which is caused by the action of auxiliary triodes.
  • the load impedance which is presented to the output triode 3 changes in such a direction that its output is also effectively doubled.
  • the condition that the peak output at maximum modulation be four times the average value is met.
  • the embodiment of my invention which is illustrated in Figure 2 differs from that just described in that the radio frequency voltage is applied out of phase to the two auxiliary triodes 25 and 21. This makes it unnecessary to invert the phase of the output of the second auxiliary amplifier 21.
  • the phase inverter 35 is no longer necessary.
  • the anodes 29 and 33 of the two auxiliary triodes are therefore connected directly together and coupled to the load resistor 2
  • the anodes 29 and 33 are also connected directly to the output of the impedance inverter
  • the modulating voltage is applied out of phase to the two grids 59 and 6
  • the radio frequency input to the auxiliary triodes is
  • a push-pull radio frequency transformer 15 impressed on the grids out of phase by means of a push-pull radio frequency transformer 15.
  • the primary 11 of this transformer is connected between the output of the phase shift network 61 and ground.
  • Thesecondary 19 of theradio frequency transformer 15 is connected between the grids of the auxiliary triodes through a pair of coupling capacitors 8
  • the purpose of these capacitors is to prevent the secondary of the radio frequency transformer from short-circuiting the secondary of the audio frequency transformer 55 which is connected across it.
  • a radio frequency choke coil has been connectedin series with one side of the sec ondary winding 51.
  • the auxiliary triodes are biased by a battery 69 so that in the absence of modulation, substantially no current is drawn by either tube.
  • the auxiliary triodes are alternately made to impress a radio frequency voltage on the load resistor in accordance with the modulating voltage. Since .the radio frequency current applied to the two grids is out of phase, it is seen that modulating potentials of one polarity cause an in-phase radio frequency voltage to be impressed across the load, While modulating potentials of the other polarity cause out of phase potentials to be impressed across the load.
  • a solution is found, as in the Vance application, by applying unequal bias to the two auxiliary tubes, or by supplying a radio frequency bias. Either of these methods are applicable to my invention, and in addition, I propose another system.
  • a voltage ratio between input and output may be obtained which is greater or less than unity, as desired.
  • An unbalanced condition is therefore provided which compensates for the difference in plate voltage which appears upon the plates of the tubes.
  • a utilization device a source of unmodulated carrier frequency currents, impedance inverting means for impressing said currents on said utilization device, a source of modulating voltage, a pair of thermionic amplifier tubes having input and output electrodes, means for applying said modulating voltage to said input electrodes in phase opposition, means including a 90 phase shifting network for applying said unmodulated carrier frequency currents in phase opposition to said input electrodes, and means for coupling the output electrodes of said thermionic amplifier tubes to said utilization device, whereby modulating voltages of one polarity increase the effective current in said utilization device and of the opposite polarity decrease the effective current in said utilization device.
  • a utilization device a source of unmodulated carrier frequency currents, impedance inverting means for impressing said currents on said utilization device, a source of modulating voltage, a pair of thermionic amplifier tubes having input and output electrodes, means for applying said modulating voltage to said input electrodes in phase opposition, means for applying said uninodulated carrier frequency currents in phase opposition to said input electrodes, means for coupling the output electrodes of said thermionic amplifier tubes to said utilization device, whereby modulating voltages of one polarity increase the effective current in said utilization device and or the opposite polarity decrease the effective current in said utilization device.
  • a utilization device a source of unmodulated carrier frequency currents, means including a capacitor for impressing said currents on said utilization device, a source of modulating voltage, a pair of thermionic amplifier tubes having input and output electrodes, means for applying said modulating voltage to said input electrodes in phase opposition, means for applying said unmodulated carrier frequency currents in phase opposition to said input electrodes, means including said capacitor for coupling the output electrodes of said thermionic amplifier .tubes to said utilization device, whereby modulating voltages of one polarity increase the effective current in said utilization device and of the opposite polarity decrease the effective current in said utilization device.
  • a utilization device a source of unmodulated carrier frequency currents, means for impressing said currents on said utilization device, a source of modulating voltage, a pair of thermionic amplifier tubes having input and output electrodes, means for applying said modulating voltage to said input electrodes in phase opposition, means including a phase shifting network for applying said unmodulated carrier frequency currents in phase opposition to said input electrodes, means for coupling the output electrodes of said thermionic amplifier tubes to said utilization device, whereby modulating voltages of one polarity increase the efiective current in said utilization device and of the opposite polarity decrease the eifective current in said utilization device.
  • a load device a source of unmodulated carrier frequency currents, means including an impedance inverting network for impressing said unmodulated currents on said load device, a source of modulating voltage, a pair of thermionic amplifier tubes having input and output electrodes, means for applying said modulating voltage to said input electrodes in phase opposition, means including a phase shifting network for applying said unmodulated carrier frequency currents in phase opposition to said input electrodes, means for coupling the output electrodes of said thermionic amplifier tubes to said load device, whereby modulating voltages of one polarity increase the effective current in said utilization device and of the opposite polarity decrease the effective current in said utilization device.
  • a device of the character described in claim 3 which includes a common source of direct energizing potential connected to the output electrodes of said thermionic tubes.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Transmitters (AREA)
  • Amplifiers (AREA)
US324255A 1938-09-30 1940-03-16 Modulation system Expired - Lifetime US2248462A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
NL60868D NL60868C (enrdf_load_stackoverflow) 1938-09-30
US232482A US2226942A (en) 1938-09-30 1938-09-30 Neutralized power amplifier
GB23213/39A GB532006A (en) 1938-09-30 1939-08-11 Improvements in or relating to modulation systems
US324255A US2248462A (en) 1938-09-30 1940-03-16 Modulation system

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US232483A US2224314A (en) 1938-09-30 1938-09-30 Modulation system
US324255A US2248462A (en) 1938-09-30 1940-03-16 Modulation system

Publications (1)

Publication Number Publication Date
US2248462A true US2248462A (en) 1941-07-08

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Family Applications (1)

Application Number Title Priority Date Filing Date
US324255A Expired - Lifetime US2248462A (en) 1938-09-30 1940-03-16 Modulation system

Country Status (3)

Country Link
US (1) US2248462A (enrdf_load_stackoverflow)
GB (1) GB532006A (enrdf_load_stackoverflow)
NL (1) NL60868C (enrdf_load_stackoverflow)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3084329A (en) * 1959-08-06 1963-04-02 Electronic Communications Noise suppression technique for radio circuits
US7129872B1 (en) * 2005-05-25 2006-10-31 Audio Note Uk Ltd. Audio signal analog-to-digital converter utilizing a transformed-based input circuit
US20160190990A1 (en) * 2014-12-26 2016-06-30 Samsung Electro-Mechanics Co., Ltd. Concurrent dual-band signal amplifier

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3084329A (en) * 1959-08-06 1963-04-02 Electronic Communications Noise suppression technique for radio circuits
US7129872B1 (en) * 2005-05-25 2006-10-31 Audio Note Uk Ltd. Audio signal analog-to-digital converter utilizing a transformed-based input circuit
US20160190990A1 (en) * 2014-12-26 2016-06-30 Samsung Electro-Mechanics Co., Ltd. Concurrent dual-band signal amplifier
US9673765B2 (en) * 2014-12-26 2017-06-06 Samsung Electro-Mechanics Co., Ltd. Concurrent dual-band signal amplifier

Also Published As

Publication number Publication date
GB532006A (en) 1941-01-15
NL60868C (enrdf_load_stackoverflow)

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