US2338237A - High-frequency electron discharge apparatus - Google Patents

Description

Jan. 4; 1944. FREMLlN 2,338,237

HIGH FREQUENCY ELECTRON DISCHARGE APPARATUS Filed Dec. 10, 1940 TO SIGNAL MODl/M 7' IIVG Sou/r65 T0 JIGML MODl/LA TING SOURCE IN VEN TOR JOHN HEAVEI? FfiEMU/V ATTORNEY Patented Jan. 4, 1944 UNITED STATES v PATENT- Fl=lCE azaazs'z HIGH-FREQUENCY ELECTRON DISCHARGE John Beaver Fremlin, London, England, asaignor to International Standard Electric Corporation,

New York, N. Y.

Application December 10, 1940, Serial No. 369,431

In Great Britain December 22, 1939 Claims. (CL 250-275) This invention relates to ultra-high frequency apparatus comprising resonators of the cavity type.

It is proposed, in accordance with the invention, to modulate or change the frequency of a resonator of the cavity type by varying the dielectric constant withina portion of the reso-v nator, by varying an electronic space charge or by varying the intensity or velocity of an electron beam traversing that portion.

The invention is primarily applicable to electron discharge apparatus using the principles of velocity modulation of electrons for the excitation of a resonator effective at very high frequencies.

Briefly such apparatus usually comprises a single resonator or a pair of coupled resonators of cavity type, electrons being passed through two successive gaps therein to be modulated in velocity in the first gap and to yield energy at the second gap for the maintenance or oscillations.

In either single or double resonator apparatus utilising velocity modulation of electrons, an auxiliary electron beam may be fired across some part of one of the resonators. This auxiliary beam, if of suitable velocity will change the dielectric constant and hence the natural frequency of the resonator. In the case of a single resonator, therefore, modulation of the auxiliary beam will give a frequency modulation of the high frequency output, while in a double resonator it will give an amplitude modulation (owing to the detuning of one resonator with respect to the other), probably combined with some degree of frequency modulation.

The illustration of the single cavity and double cavity tubes in accordance with this invention are shown in the drawing in which, Fig. 1 shows a single cavity arrangement, and Fig. 2 a double cavity arrangement.

In the drawing the illustrations are made diagrammatically.

In Fig. 1 an electron emitting cathode l0 emits electrons which are accelerated by accelerator electrode I l and centered by the control electrode l2 to produce a cathode beam shown in dotted lines at l3. This beam is transmitted through a pair of grids l4, l5, located in the wall of resonant cavity l6 and tube ll, respectively, after which it is again subject to the effect of a control potential between grid l8 and the end wall of chamber it. Such a tube is known in the prior art and energy may be extracted from the tube due to the retarding effect caused between l8 and the end wall.

In accordance with my invention modulation of the signal beam is provided by means of a second beam traversing the cavity through which the beam passes so as to change the dielectric constant effective in this area. Thi is accomplished by a cathode 20, an accelerating electrode 2| to which a signal modulating source is coupled, a concentrating electrode 22 to form the electrons emitted from cathode 20 into a beam,

and a target electrode 23 which serves to prevent electrons from the beam from returning into the space. The signal modulations applied to electrode 2| serve to vary the concentration of the beam emitted from cathod 20 and so to vary the tures shown invFig. 2 may, if desired, be applied to Fig. 1 and similarly the features of Fig. 1 which differ from Fig. 2 may be applied to this other arrangement.

What is claimed is:

1. High frequency discharge apparatus including a tube, means coaxial with and surrounding said tube, forming a hollow resonant chamber, a plurality of aligned grids, one in one end of said means, a second in one end of said tube and adjacent said first grid, and a. third at the other end of said tube, a source of electrons aligned with said grids and adapted to discharge and-direct electrons along ,a path through all of said grids, and means for varying the dielectric constant of said chamber, comprising a second source of electrons and a target positioned within said chamber, forming an electron discharge path across said chamber between said third grid and the other end of said resonant chamber forming means.

2. Modulated high frequency discharge apparatus comprising a hollow resonator having a predetermined dielectric constant, means for maintaining oscillations in the resonator including means for directing a stream of electrons along a main discharge path through the resonator, and means for modulating said oscillations including means for directing a second stream of electrons along a second discharge path through the resonator and means for modulating said second stream.

3. Modulated high frequency discharge apparatus as set forth in claim 2, including means for velocity modulating the first stream of electrons in one part of the resonator, and means for transferring energy from said stream to the oscillating field in a second part of the resonator, and in which the second stream of electrons passes through said second part of the resonator.

4. Frequency modulated high frequency discharge apparatus comprising a hollow resonator having a predetermined dielectric constant and an oscillation frequency determined by said constant, means for maintaining oscillations in the resonator including means for directing a stream of electrons along a main discharge path through the resonator, and means for modulating the frequency of said oscillations including mean for directing a second stream of electrons along a 20 second discharge path through the resonator and means for modulating said second stream.

5. Amplitude modulated high frequency discharge apparatus comprising a hollow resonator having a predetermined dielectric constant and formed with two resonant cavities, means for maintaining oscillations in the resonator including means for directing a stream of electrons along a main discharge path passing through both cavities of the resonator, and means for amplitude modulating the frequency of said oscillations including means for directing a second stream of electrons along a second discharge path through the second cavity of the resonator, located adjacent the discharge end of the first stream of electrons, and modulating said second stream, said detuning action of one cavity with respect to the other producing amplitude modulation.

JOHN HEAVER FREMLIN.

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