US2500328A

US2500328A - Pulsed oscillator of the magnetron type

Info

Publication number: US2500328A
Application number: US585024A
Authority: US
Inventors: Percy L Spencer
Original assignee: Raytheon Manufacturing Co
Current assignee: Raytheon Co
Priority date: 1945-03-27
Filing date: 1945-03-27
Publication date: 1950-03-14
Anticipated expiration: 1967-03-14

Description

March 14, 1950 P. L. SPENCER 2,500,328

PULSED OSCILLATOR OF THE MAGNETRON TYPE Filed March 27, 1945 lllll u l; um

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I mam rm Br e 4. Sff/VCi/fl Fatenied ar. 14, 195G UNITED STATES OFFIE Percy L. Spencer, West Newton, Mass, assignor to Raytheon Manufacturing Company, Newton, Mass, a corporation of Delaware Application March 27, 1945, Serial No. 585,024

Claims.

This invention relates to an electron discharge device of the magnetron type and more particularly to such a device which is operated by supplying pulses of voltage between the cathode and anode thereof so as intermittently or periodically to energize the device.

In devices of this kind the magnitude of the magnetic field ordinarily is such as to require magnet structures of considerable size and weight.

An object of my invention is to devise such an arrangement in which the massive magnet structure heretofore required may be subtantially eliminated.

Th foregoing and other objects of this invention will be best understood from the following description of an exemplification thereof, reference being had to the accompanying drawing wherein:

Fig. 1 is a diagrammatic view of an arrangement incorporating my invention showing a magnetron tube in longitudinal cross section taken along line |l of Fig. 2; and

Fig. 2 is a transverse cross section of the magnetron taken along line 2-2 of Fig. 1.

lhe magnetron illustrated comprises a glass envelope I which is closed at on end by a reentrant stem 2 supporting an electrode structure. This electrode structure consists of an anode 3 and a cathode t centrally disposed therein. The cathode l may be of the thermionic filamentary type coated with suitable emitting oxides.

The anode comprises a hollow box 5 made of suitable highly conducting material such as copper. Fastened to the upper wall of said box and extending inwardly therefrom is a pair of anode plates 6. Between the anode plates 6 and on each side thereof is a corresponding pair of anode plates I fastened to the lower Wall of said box 5 and extending inwardly therefrom. It will be noted that a circuit is completed between each adjacent pair of anode arms 6-! which extends through the walls of the box 5. Each circuit thus defined contains capacity and inductance and constitutes a cavity resonator so that when the device is operated so as to produce oscillations therein, the frequency of said oscillations is determined by the natural frequency of such cavity resonator.

The anode is electrically connected to and supstandards [0 and H. The standards 8, l0. and 55 I l are electrically connected to lead-in wires l2, l3, and M which are sealed through the press 2 and extend to the exterior of the tube whereby electrical external connections may be made thereto.

When the device as described above is energized with proper voltage and a strong magnetic field is created transverse to the direction of electron fiow between the cathode 4 and the anode plates 6 and l, the device generates ultra-high frequency oscillations. These oscillations may be led out from the tube by a coupling loop l5 extending into the hollow box 5 in the proper position to be coupled to the magnetic vector of the oscillations within said box. One end of the coupling loop US may be electrically connected at E6 to the box 5. The other end of said loop may pass through an opening H in the sid wall of said box 5. The ends l8 and IQ of said loop l5 are sealed through the side wall of the envelope l and constitute a transmission line whereby the oscillations may be fed to asuitable consumption device.

In order to create the magnetic field necessary to produce the magnetron operation, there is supported within the box 5 a coil 20 of high conducting, material capable of carrying large values of current. One end of said coil may be electrically connected to the box 5 as by being welded to the upper end of anode standard 8. The other end of the coil 20 passes out from the hollow box 5 through an insulator 2| and is connected to a conducting standard 22 sealed in the press 2. The standard 22 has connected thereto a lead-in conductor 22' sealed through the press 2 and extending xteriorly of the tube.

The filamentary cathode 4 may be supplied with heating current from a transformer 23 having a primary 24 connected to a suitable source of alternating current and having a secondary 25 connected to the lead-in conductors l3 and i l.

As previously indicated the magnetron is to be operated so as to supply pulses of ultra-high frequency oscillations. For this purpose the device is supplied with pulses of power from a condenser 20 which is charged from a suitable sourc of direct current 27 through a currentdimiting resistance 28. The negative end of the condenser 26 is connected by means of a conductor 20 to a center tap on the secondary winding 25. The positive side of condenser 26 is connected through a switch 30 to the lead-in conductor E2. The switch 30 may be periodically closed at any desired repetition rate. This may be of the order of 1000 cycles per second or more. Of course, it

is to be understood that switch 31) could be operated according to any other desired time pattern.

Whenever the switch 3B closes, the anode 3 is made positive with respect to the cathode d. The time constant of the discharge circuit of the condenser 25 is so small that the voltage is applied between the cathode and anode substantially simultaneously with a very high discharge current flow through the coil 2b which creates the necessary magnetic field. The combination of this magnetic held and the anode voltage causes the device to generate a short pulse of oscillations. In pulse operation of this type the duration of the pulse can be very short so that it is a relatively simple matter to design th circuits in such a way that both the anode voltage and the current flow exist for a sufficient period to produce the desired length of pulse. Since the current flows through the coil for only a very short period of time, for example, of the order of several micro-seconds, an enormous value of current can be passed through said coil without in any way tending to damage any of th parts of the device. This value of current may be readily made of such a value as to create a high intensity of magnetic field sufficient to produce the proper magnetron operation.

When the condenser hasbeen discharged the switch 33 is re-opened. The time constant of the charging circuit for the condenser 26 is designed so that said condenser is sufhciently charged to the proper voltage before the switch 38 re-closes.

Of course, it is to be understood that this invention is not limited to the particular details as described above inasmuch as many equivalents will suggest themselves to those skilled in the art. It is accordingly desired that the appended claims be given a broad interpretation commensurate With the scope of the invention within the art.

What is claimed is: v

1. A magnetron oscillator comprising a cathode, an anode adjacent said cathode and spaced therefrom to provide a discharge path for the how of electrons from said cathode to said anode, a coil surrounding said discharge path with the axis of said coil substantiall transverse to the direction of said flow of electrons, means, connected between said cathode and anode, and across said coil, for substantially simultaneously supplying a pulse of voltage between said cathode and anode and a pulse of current through said coil. 7 I 4 2. A magnetron oscillator comprising a cathode, an anode adjacent said cathode and spaced therefrom to provide a discharge path for the flow of electrons from said cathode to said anode, a coil surrounding said discharge path with the axis of said coil substantially transverse to the direction of said fiow of electrons, a condenser, means, connected across said condenser and between said cathode and anode, and establishing a potential difierenc'e between said cathode and anode, and means, connected between said condenser and said coil, for discharging said con- 4 denser through said coil and substantially simultaneously connecting said first-named means between said cathode and anode.

3. A magnetron oscillator comprising a cathode, an anode adjacent said cathode and spaced therefrom to provide a discharge path for the flow of electrons from said cathode to said anode, said anode comprising a plurality of anode arms, each pair of adjacent anode arms, together with that portion of said anode lying therebetween, providing a, cavity resonator, a coil surrounding said anode arms with the axis of said coil substantially transverse to th direction of said flow of electrons, means, connected between said cathode and anode, and across said coil, for substantially simultaneously supplying a pulse of voltage between said cathode and anode and a pulse of current through said coil.

4. A magnetron oscillator comprising a cathode, an anode adjacent said cathode and spaced therefrom to provide a discharge path for the flow of electrons from said cathode to said anode, said anode comprising a plurality of anode arms, each pair of adjacent anode arms, together with that portion of said anode lying therebetween, providing a cavity resonator, a coil surrounding said anode armswith the aids of said coil substantially transverse to the direction of said flow of electrons, a condenser, means, connected across said condenser and between said cathode and anode, for charging said condenser, and establishing a potential difference between said cathode and anode, and means, connected between said condenser and said 0011, for dis;- charging said condenser through said coil and substantially simultaneously connecting said first-named means between said cathode and anode.

5. A magnetron oscillator comprising an anode structure including a cylindrical body closed at its ends by end plates and having inwardlyextending anode arms projecting alternating from said end plates, a cathode axially disposed Within said anode structure, acoil disposed within said anode structure surrounding said anode arms, and means, connected between said cathode and anode structure, and across said coil, for substantially simultaneously supplying a voltage pulse between said cathode and anode structure and a current pulse through said coil.

PERCY L. SPENCER.

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

UNITED STATES PATENTS Certificate of Correction Patent No. 2,500,328 March 14, 1950 PERCY L. SPENCER It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 1, line 13, for subtantially read substantially; column 3, line 64, after the Word and comma anode, and before and insert for charging said condenser; column 4, line 31, after condenser strike out the comma;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Oflioe.

Signed and sealed this 4th day of July, A. D. 1950.

[SEAL] THOMAS F. MURPHY,

Assistant Commz'ssz'oner of Patents.