US2147182A - Electronic oscillator - Google Patents

Description

Patented Feb. 14, 1939 ELECTRONIC OSCILLATOR Irving Wolff, Merchantville, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application May 26, 1936, Serial No. 81,810

Claims.

My invention relates to electronic oscillators of the Barkhausen-Kurz or magnetron type. More specifically, this invention relates to electronic oscillators in which the emission or mo- 5 tion of energy absorbing electrons is reduced,

thereby increasing the efiiciency of the oscillatory currents.

It is well known to those skilled in that art that the term electronic oscillator is applied to electronic oscillatory devices in which the electron transmit time is of the order of the duration of the oscillatory cycle. Such oscillators, operating on microwave lengths, develop relatively low power outputs. One of the reasons for the low power output is low efiiciency which is due, in part, to the emission or movement of energy absorbing electrons. It is, therefore, one of the objects of this invention to increase the efficiency of an electronic oscillator by controlling the emission or movement of electrons.

Another object is to prevent the emission of electrons, which absorb energy from the oscillatory circuit. A still further object is to limit the emission of electrons to such times at which the motion of the electrons will be of proper phase to add to the energy in the oscillatory circuit. An additional object is to prevent the emission or movement of energy absorbing electrons by creating a space charge, about the cathode, which is controlled by the phases of the oscillatory current.

In the accompanying figures,

Figure 1 is a schematic circuit diagram of my invention applied to a Barkhausen-Kurz oscillator,

Fig. 2 is a circuit diagram of the arrangement of Fig. 1 applied to a magnetron oscillator, and

Fig. 3 is a schematic diagram of a push-pull electronic oscillator with space charge controlling means applied in accordance with my invention.

In Fig. 1 within an evacuated envelope I are suitably mounted a cathode 3, a control electrode 5, an accelerating electrode 1 and an outer electrode 9. The various electrodes may be coaxially arranged about the cathode; although my invention is not limited to any particular arrangement. The cathode 3 is connected through a pair of radio frequency choke coils ll, I3 to a battery [5 or other suitable source of energy. The accelerating electrode 5 may be grounded and connected through a radio frequency choke I! to the positive terminal of a biasing battery [9. The negative terminal of the biasing battery is connected to the cathode circuit.

A tuned circuit, which may be a transmission line comprising leads 2 l-23, is connected to the cathode 3 and outer electrode 9, and a dipole antenna 25. The dipole antenna is open circuited with respect to direct currents, by the inclusion 5 of a blocking condenser 21. The outer electrode 9 may be biased slightly negative with respect to the cathode 3 by a battery 29 which is connected to the transmission line by radio frequency choke coils 3|33. If the control electrode 5 and its circuit 35 were omitted, the foregoing arrangement would operate as an electronic oscillator in accordance with the accepted theory. That is, some of the electrons emitted by the cathode move through the accelerating electrode and approach the outer electrode 9. Some of these electrons, upon approaching the outer electrode are repelled and proceed toward the cathode. This cycle is repeated and, by virtue of the cloud of electrons moving between cathode and outer electrode, oscillatory currents are established in the tuned transmission line connected to the dipole antenna.

The operation of electronic oscillatory phenomenon has been explained as due to the group-- ing of electrons, some of whose motions are of such phase with respect to the generated voltage that they lose their energy of motion and thus deliver energy to an external circuit. Other electrons have a motion with respect to the generated voltage which causes them to be accelerated and thus abstract energy from the circuit. Fortunately, the former group of electrons exist in greater numbers and therefore the electronic oscillations are persistent. However, if the latter 35 group could be entirely suppressed or eliminated, the efficiency of an electronic oscillator would be greatly increased.

The first group, or electrons which give up energy, will be essentially in phase with oscillatory 40 current, and will be called in phase electrons. The latter group, or electrons which abstract energy, will be essentially out of phase with the oscillatory current and will be called out of phase electrons. By means of the control electrode 5 which is serially connected through a phase adjusting circuit 31, bypass capacitor 39, and adjustable contact M to the transmission line 2!, a varying voltage may be impressed on the control electrode of the proper phase and 50 magnitude to prevent the emission of electrons with out of phase motions.

' The control electrode may be given a steady initial bias by a battery 43. I prefer to make the control electrode negative with respect to cathode. Since the control electrode establishes a space charge of the proper phase with respect to the currents in the oscillatory circuits, the space charge will tend to suppress the out of phase electrons. Likewise, the control electrode will establish a space charge in proper phase to aid the movement of electrons which have a proper phase of motion with respect to the oscillatory currents. Thus these electrons give up energy and thereby increase the operating efficiency.

In Fig. 2 a magnetron oscillator is shown. In most respects the circuit of Fig. 2 is essentially the same as the Barkhausen-Kurz oscillator of Fig. 1. Similar reference numerals have been used in this and the other figures to indicate similar elements. The accelerating electrode of the Barkhausen-Kurz oscillator is emitted and the outer electrode becomes an anode in the magnetron. A magnetic field is established by a permanent magnet, an electro-magnet or a solenoid energized by a battery 41 as shown. The operation of the magnetron follows the normally accepted theory with the addition of the control electrode '5, which applies the phase controlling voltages as previously described in connection with Fig. 1.

A push-pull Barkhausen-Kurz oscillator, similar to the single oscillator of Fig. 1, is schematically illustrated in Fig. 3. The tuned or resonant transmission line 2l--23 is connected between the pair of outer electrodes. A second tunable transmission line 5| is connected between the pair of cathodes 33. The bridging member 53 is adjustably arranged to permit tuning of the transmission line 5|. The voltages for controlling the potential of the control electrodes 5-5 are determined in this instance from taps 4| 0n the cathode tuned circuit 5|. These connections or taps 4| could have been made to the transmission line 2 I 23 connected to the anodes 9-9, inasmuch as voltages of the proper phase may be derived from either tuned circuit. The final adjustment of the phase may be made by adjusting the effective length or reactance of the phasing circuits 31, 3?. The operation of the push-pull oscillator is essentially the same as the single oscillator of Fig. 1 with respect to the control of electrons having an out of phase motion.

My invention is not limited to the precise arrangements of the several illustrations which have been given by way of example. It should be understood that the push-pull oscillator may be applied to the magnetron as well as to the Barkhausen-Kurz oscillator. The connection from the control electrode may be made to any part of the tuned circuit or transmission line which may be connected between any suitable combination of electrodes. The control electrode is not limited to use in thermionic tubes but may be applied in a similar manner to electronic oscillators whose cathode have photo-emissive or secondary electronic emissive properties.

I claim as my invention:

1. An electronic oscillator including in combination a tube having an electron emitting cathode and a plurality of electrodes, a tuned circuit connected between two of said electrodes, means for establishing an oscillatory current in. said tuned circuit, and means including an additional electrode and a source of variable bias voltage obtained from said tuned circuit and applied to said electrode for preventing electrons having a motion in out of phase relationship with respect to said oscillatory current from absorbing energy from said current.

2. An electronic oscillator including in combination a thermionic tube having an electron emitting cathode, control electrode, accelerating electrode, and outer electrode, a tuned circuit connected between said cathode and outer electrode, means for establishing oscillatory currents in said tuned circuit and a connection from said control electrode to said tuned circuit for preventing the electrons having an out of phase motion with respect to said oscillatory current from absorbing energy from said current.

3. A magnetron oscillator including a thermionic tube having an electron emitting cathode, a control electrode, and an anode, a tuned circuit connected between said anode and cathode, means for establishing oscillatory currents in said tuned circuit including a magnetic field, and

a connection from said control electrode to said tuned circuit for preventing the electrons having an out of phase motion with respect to said oscillatory currents from absorbing energy from said currents.

l. In a device of the character of claim 2,

means for adjusting the phase of the voltages impressed on said control electrode.

5. In a device of the character of claim 3, means for adjusting the phase of the voltages impressed on said control electrode.

6. A push-pull electronic oscillator comprising, in combination, a pair of thermionic tubes each having an electron emitting cathode and a plurality of electrodes, a tuned circuit connected between an electrode in each of said tubes, a second tuned circuit connected between said cathodes,

means for establishing oscillatory currents in said tuned circuits, and means including an additional electrode and a source of variable bias voltage obtained from said second tuned circuit and applied to said electrode for preventing electrons having out of phase motions with respect to said oscillatory currents from absorbing energy from said currents.

7. A push-pull electronic oscillator comprising, in combination, a pair of thermionic tubes, each of said tubes having an electron emitting cathode, a control electrode, an accelerating electrode, and an outer electrode, a tuned circuit connected between said outer electrodes, a second tuned circuit connected between said cathodes, means for establishing oscillatory currents in said tuned circuits, means for deriving a voltage from one-of said tuned circuits, and means for impressing said voltage on said control electrodes in proper phase to prevent electrons having out of phase motions with respect to said oscillatory currents from absorbing energy from said currents.

8. In a device of the character of claim 7, means for adjusting the phase of the voltage impressed on said control electrodes.

9. In a device of the character described, means including a plurality of electrodes for establishing electronic oscillations, a tuned circuit connected between two of said electrodes whereby electronic oscillations are established within a region within said means and within said circuit, and a connection between said tuned circuit and another of said electrodes whereby a variable bias voltage is derived from said tuned circuit and applied to said other electrode for preventing the entry of out of phase electrons Within said region.

10. In a device of the character described, means including a plurality of electrodes for establishing electronic oscillations, a tuned circuit connected between two of said electrodes whereby electronic oscillations are established within a region within said means and within said circuit, a connection between said tuned circuit and another of said electrodes whereby a variable bias voltage is derived from said tuned circuit, and means for adjusting the phase of said bias voltage and applying said phase adjusted voltage to said other electrode for preventing the entry of out of phase electrons within said region. 5

IRVING WOLFE.

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