US2442304A

US2442304A - Pulse keying circuit

Info

Publication number: US2442304A
Application number: US518534A
Authority: US
Inventors: Louis F Mayle
Original assignee: Farnsworth Research Corp
Current assignee: Farnsworth Research Corp
Priority date: 1944-01-17
Filing date: 1944-01-17
Publication date: 1948-05-25
Anticipated expiration: 1965-05-25

Description

May 25, 1948. MAYLE 4 2,442,304

PULSE KEYING CIRCUIT Filed Jan. 17, 1944 POWER AMPLIFiER INVENTOR r LOUIS F. MAYLE Patented May 25, 1948 PAT ENT ornce PULSE KEYING CIRCUIT Louis -F. Mayle, Fort Wayne, Ind., assignor, by

mcsne assignments, to Farnsworth Research Corporation, a; corporationof Indiana Application January 17, 1944; seriarNo; 518,534

4' Claims. 1;

invention: relates generally to synchronizing circuits and more particularly to-a: pulse keying-circuit for keying; a power ampli-fier circu'it to=produce carrier modulations correspondingato synchronizing signals.

Prior art pulse generating circuits generally include aplurality of amplifying tubes for increasing: the e'fiective' amplitude of a synchro-- nizi-ng-lpul'se. Theefficiency-of such" a system is necessarilyilow by reason'of' the-number of tubes involved. Therefore; it would bedesira'ble to obtain. a simplified circuit comprising a minimum number-"oi-tubes for generating pulses-of the required amplitude;

Theiprincipal object of this invention is" to pro vide:anove1: synchronizing pulse keying circuit fo'rikey-in'g a-poweramplifier circuit.

A further objector theinvention-is to provide asimplified: pulse keying circuit: wherein the number of" circuitcomponents is =materially re duced and wherein there is provided a "comparatively high amplitude synchronizing pulse.

In general; the invention comprises an ampliher for amplifying pulses generated by-apulse generator; axgas'discharge-keying device includin'g a storagefcondenser connected to its cathode together: witha diode: connected in the output circuitlof the gas. discharge tube in series with The storage condenser isflin' turns connected to the anode'circuit of a power: amplifier such,- for example, as a carrier:

the storage condenser.

frequency: amplifier" stage in'sa transmitter circuitz- The" storage condenser normally charged to approximately 750 volts, and when the gas discharge tubeis fired the voltage on the" storage condense'r is increased byapproximately 750 voltswhereby there is produced; in" addition to the anode voltage of I the power: amplifier; a -voltage: the-charge on the" storage con denser; thereis producedra high amplitude represented 1 by variation; inthe carrier signal to betransmitted, representative of the synchronizing pulse.

For a-betten understanding of the invention,-

together with otherandifurther objects thereof; reference is-made tothe following description;

taken: in connection with: tha accompanying.-

drawings, andiits 'scope'will' be pointed" out in the appended'claimsi- In the accompanying drawings the single-fig? pledb'y rneans of'condenser anamplifier-triode 4, There is provided a grid leal resistor 5, connected betweenground and the grid of tube 4; together-with 'a-c'athode resistor 6 and shunt condenser 1 connected between the cathode and ground; Resistor's li'and IitOget'her with condenser T are provided to energize triode 4 in a conventional manner.

The anode of-tube i is 'energ-ized'through a loadresistor'fl from-voltage source Band is coupled to the control grid of agas' discharge tube I2 through a coupling condenser M. The anode circuit is also coupled tothe anode of tube [2 by a condenser l5;- Thereis provided a grid rosisto'r I6 connected to groundthrough resistor l8 In series with the cathode'oitubel2 and resistor Hi, there is provided a resistor 20 whereby to provide a cathode follower circuit. Source 9 is-conn'ected through resistor 2| directly to thecatho'deof tube l2 for normally biasing the tube below the threshold of firing. The'anode circuit of tube: Itineluclesa source of potential 24 tog-ether'with an inductance'coil 25; Between the inductance coil 25 and the cathode of tube l2 there is connected a storage condenser 28 and a diod'e rectifier 30'. The output of the entire circuit is taken' off the'common connection between thecathode'of tube 30' and theconde'nser 2-8 and applied to the anode circuit of power amplifier 3-2: Amplifier 32' is illustrated to represent any convenient-stage of a carrier frequency amplifier'in a television transmitter whereby'condenser 28 may be connected to any desirable stage of such an amplifier.

Assuming} that the operation of the circuit commences at a" time between synchronizin pulses, the gas discharge tube I2 is nonconducting by reason of-the fact that current flows from;

source 9 through resistor 2|, resistor 20 and ,re-

-sist0r l8 to ground whereby the voltage dIQp across resistor- 'm holds gas discharge tube 12- biased below thethreshold of firing. Meanwhile,

condenser 28 is charged to approximately 750" volts with=respect toground through rectifier'30';

When a negative'pulse from source l'isimpressed on the-"grid; of tube 4 through coupling condenser 2, a positive pulse results in the anode circuit of tube 4 which is impressed on the control grid of gas discharge tube 12 through condenser Hi and also on the anode of tube 12 through condenser l5, The leading edge of this pulse raises the potential of the grid to fire the gas tube l2, and in addition the leading edge of the pulse impressed on the series combination of condenser i and inductance coil 2-5 will produce positive transient on the anode of tube l2 to facilitate firing of the tube.

The trailing edge of the positive pulse appearing in the anode circuit of tube 4' will have no efiect on the control grid of tube 12, but the trailing edge of the pulse effects the generation of a transient negative pulse on the anode of tube 82, thereby to reduce momentarily the potential of the anode and interrupt the flow of current through the tube to extinguish it.

During nonconductive periods of tube I2, current flows from source 24 through rectifier 30 to the anode circuit of power amplifier 32 and because the internal resistance of tube 30 is extremely small during its conductive periods, the plate of condenser 28 which is connected to the cathode of rectifier 30 is at the voltage of source 24. When gas tube I2 is fired, its resistance also becomes substantially nil so that the plate of condenser 28 which is connected to the cathode of tube 12 is raised in voltage from the voltage corresponding to the normal drop through resistors 20 and I 3 to the voltage of source 24. In eiTect, this is a switching or reversing operation wherein tubes i2 and 30 constitute electronic switching devices. The voltage on the other plate of condenser 28 is raised proportionately until it is substantially double the normal value. Because of the increased potential on condenser 28 and on the cathode of tube 30, this tube becomes inoperative during the periods that tube I2 is conductive and during these same periods the potential on the anode circuits of power ampliher 32 is substantially doubled. Thus the carrier signal in the amplifier circuit is keyed to include high amplitude variations representative of syn chronizing pulses.

When tube [2 is extinguished by the trailing edge of the synchronizing pulse impressed on the grid and plate thereof, the plate of condenser 28 which is connected to the cathode of tube [2 assumes the normal potential impressed thereon by source s whereby rectifier 30 again becomes conductive to supply normal voltage to amplifier 32.

It is not intended that this invention shall be limited to the use of any particular circuit elements or circuit values, but purely by way of example there follows a table of circuit values which it is believed would cause the herein described circuit to operate in accordance with the foregoing.

Resistor 20 1,000 ohms 4 Resistor 2| 50,000 ohms Source 24 750 volts Inductance coil 25 microhenries Condenser 28 1 microfarad Tube 30 Type 5Y3GT While there has been described what is at present considered the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

I claim:

1. In combination, a power ampilfier including an anode circuit, a charge storage device connected to said anode circuit, a source of potential and a rectifier connected to said anode circuit and said charge storage device for applying operating potential to said anode circuit and for charging said charge storage device to a predetermined potential, a gas discharge tube including a cathode, a control grid and an anode, said anode being connected to said source of po tential and said cathode being connected to said charge storage device, a source of potential connected for normally biasing said discharge tube inoperative, and a source of pulses connected to the control grid and anode of said discharge tube for periodically firing and extinguishing said discharge tube thereby to intermittently connect said first source of potential to said charge storage device for impressing increased potential on said power amplifier anode circuit.

2. A pulse keying circuit comprising a source of pulses, a gas discharge tube including a grid, cathode and anode, means connected between said grid and said source for impressing pulses on said grid, means connected between said source and the anode of said gas discharge tube for impressing pulses on the anode of said tube and means connected to said anode and responsive to said pulses for generating transient voltages corresponding to the leading and trailing edges of said pulses for firing and extinguishing said tube.

3. A pulse keying circuit comprising a source of pulses, a gas discharge tube including a grid, cathode and anode, coupling means connected between said grid and said source for impressing pulses on said grid and firing said tube, coupling means connected between said source and the anode of said gas discharge tube for impressing pulses on the anode of said tube and impedance means connected to said anode and responsive to said pulses for generating transient voltages corresponding to the leading and trailing edges of said pulses for firing and extinguishing said tube.

4. A synchronizing pulse keying circuit comprising a source of synchronizing pulses, a gas discharge tube including a grid, cathode and anode, coupling means connected between said grid and said source for impressing pulses on said grid and firing said tube, coupling means connected between said source and the anode of said gas discharge tube for impressing pulses on the anode of said tube, impedance means connected to said anode and responsive to said pulses for generating transient voltages corresponding to the leading and trailing edges of said pulses for firing and extinguishing said tube, a signal output circuit, rectifier means connected between said anode impedance and said output circuit and charge storage means connected between the cathode of said gas discharge tube and said output circuit whereby one plate of said charge storage means is normally at a certain potential when said discharge tube is non-conductive and at a higher potential when said discharge tube is conductiv LOUIS F. MAYLE.

REFERENCES CITED The following references are of record in the file of this patent:

Number 6 UNITED STATES PATENTS Name Date Blomberg May 2, 1933 Cockcroft et a1. Feb. 26, 1935 Schade Mar. 2, 1937 FitzGerald Apr. 27, 1937 Burnside Nov. 26, 1942 Jones Apr. 29, 1941 Baldwin Oct. 14, 1941 Robins May 26, 1942 Livingston Oct. 5, 1943