US2236016A - Oscillation generator - Google Patents

Description

March 25, 194i. M. STEENBECK Q 2,236,016

OSCILLATION GENERATOR Filed July 12, 1946 70 Source 0/ z E W 75 Source 0/ flea/771g C'ur-r'enf' 21 f/eaf/ny Currerlf 17am:- Skenhecfi 2655M,

Patented Mar. 25, 1941 UNITED STATES PATENT OFFICE OSOILLATION GENERATOR Application July 12, 1940, Serial No. 345,068 In Germany February 10, 1939 6 Claims.

The invention is concerned with an arrangement adapted to the production of electric radio frequency oscillations of short wavelengths. What is meant by short waves are oscillations .whose wavelengths amount to several meters down to fractions of a meter. For the production of oscillations a discharge vessel is employed in'which an auxiliary discharge is maintained for the purpose of supplementing or boosting a discharge plasma. According to the invention such a discharge plasma is in contact with two electrodes which are coupled with oscillable structures and which have a definite mean potential with respect to the neighboring plasma. The radio frequency oscillations produced are taken off from or put out by the electrodes in contact with the plasma.

In order to give the electrodes (main electrodes) in contact with the plasma a definite potential with respect to the latter, it is expedient to con- 20 nect the main electrodes with one of the electrodes of the auxiliary discharge; for instance,

the cathode, by Way of a choke coil. In place of the choke coil, there could also be used a resistance possessing a high value for radio fre- 25 quency. However, the use of choke coils is advantageous inasmuch as they offer practically no resistance to the direct currents flowing to the electrodes.

Exempliiied embodiments of the invention are shown in Figs. 1 and 4 of the appended drawing. Figs. 2 and 3 are fragmentary sectional views of a modification of Fig. 1 showing shielding means for the intermediate electrodes.

Referring to Fig. 1, l denotes a discharge vessel which, for instance, is filled with an ionizable medium such as mercury vapor, or a raregas, or a mixture of mercuryvapor and one .or more rare gases. 2 is a cathode which may be either a directly or indirectly heated cathode, or amercury cathode, or a cold glow-discharge cathode. 3 is the plate or anode. Between the cathode 2 and the anode 3 an auxiliary discharge is maintained with the aid of the battery 4 and stabilizing or ballasting resistance 5. B and l designate the main electrodes which are directly coupled by direct electrical connection with means capable of oscillating in the form of Lecher wires 8 and 9. In order to give the main electrodes 6 and 1 a definite potential with respect to the plasma, they are conductively connected with the cathode 2 by way of choke coils Ill and H and battery 13. It can be shown by experiment that, with an arrangement as illustrated in Fig. 1, electric radio frequency oscillations arise between the main electrodes 6 and I. As far as the production of oscillations is concerned, the following may be said "with a certain amount .of plausibility and probability.

As long as the potential of electrodes 6 and I is negative with respect to the neighboring plasma, 5 so-called Langmuir layers are formed about these electrodes. It can be imagined that in this manner a certain amount of charged particles, especially electrons, are bounded or confined by electrodes 5 and l. The aggregate of 10 these charged particles is represented in Fig. 1 by means .of the dash-line l4 and will be designated hereinafter as electron block. The position of this electron :block between electrodes 6 and 1 is unstable. Foras soon as it leaves its median position and approachesone of the electrodes, the forces between these electrodes in the electron block will increase. A limitation of the movement of the electron block isbrought about by the fact that the electrode is charged by the electrons flowing thereon. Theforces acting between the electron block and the other electrode predominate, so that the electron block reverses its direction of movement, :and the same process just describedrepeats itselfat the other electrode. In order that oscillations may be maintained, the first electrode must be discharged during the interval. This discharge takes place by way of the choke coils l0 and H. Such positive ions as impinge upon the electrodes also take part in the discharge. It can be shown that the frequency of the ensuing oscillations is a function of the ion concentration in the plasma.

In order to prevent any exchange of charge- .carriers or particles between the electrodes and the plasma on the faces of the electrodes 6 and I which are turned away fromeach other and in order to thus prevent damping of the oscilla- 1t1ons,.it:is recommendable to shieldelectrodes 6 and 1 :inrespect to the plasma except the surfaces facingeach other. An electrode assembly of the said sortfis. shown in section andplan, respectively, in Fig. 2 and Fig. 3. lis'thewall orshell of the vessel, and 6 and :l denotethe electrodes. The spaceconfined between the electrodes is laterally screenedand covered by plates ofmica l5 31011116. The ends of electrodes 6 and l are fittedinto openings of mica discs I1 and 18. Hence, a discharge is able to pass only'through the gap or shaft confined between electrodes 6 and I.

Fig. 4 shows another exemplified embodiment of the invention. Such parts as appear in Fig. 1 bear here the same reference numerals. The main electrodeszfiand .21 in the tube accordingto this embodiment are concaveor hollow and on .55

tential being substantially negative;

may enter the discharge space at the surfaces located opposite each other they have openings I8. Inside the main electrodes 26 and 21 is disposed a source of electrons such as an incandesced cathode l9 and 20, respectively, in such a way that the electrons given off therefrom are able to fly through the openings l8 into the discharge space. The heating current is supplied to the cathodes l9 and 20 through radio frequency choke coils 2|. In respect to the main electrodes 26 and 21, they are maintained at a suitable and conveniently adjustable potential. The pressure of the vapor or gas prevailing inside the discharge space as well as the form of the electrodes and the interelectrode spaces, the size of the apertures l8 and the position and the distance of the electron sources l9 and 20 in respect to the main electrodes are so fixed and chosen that no spontaneous or unsupported discharge is able to arise between electron sources l9 and 20 and the auxiliary discharge between cathode 2 and anode 3, with the result that the emergence of electrons through the openings 18 will remain a function of the field intensities in the neighborhood of the said openings. If arrangements are made in a way as stated, the emergence of electrons through the openings l8 brings about an additional generation of oscillations of the electron block between electrodes 26 and 21. This will be understood if it is kept in mind that with growing distance of the electron block from one of the electrodes, say 21, because of the shift of field intensity anteriorly of the cathode towards more positive values which is associated therewith, the emergence of electrons increases and in connection therewith there happens a reduction of the restoring force tending to retard or impede the motion of the electron block. To be sure, this may be attended with a change in the frequency, Electrodes 26 and 21 are kept at a negative potential in respect to the neighboring plasma; as a result they become covered with a Langmuir layer upon the surfaces being in contact with the auxiliary discharge. In respect to them, the auxiliary discharge may be at a poas a result, theelectrons leaving the electrodes 26 and 21 a considerable rate of velocity. Although it is unlikely for the speeds of the electrons being accelerable to a level so that inside a period of oscillation the electrons will be able to cover the distance between the two electrodes 26 and 21 twice, it will nevertheless be possible to make conditions so that the ensuing oscillations will correspond to a higher harmonic, say the third harmonic of the to and fro cycles of the electrons. It is thus feasible to put energy into the mechanism taking a part in the generation of the oscillations supplied from the battery l3 by means of which the electrodes 26 and 21 are endowed with a negative potential in respect to the neighboring plasma.

In the exemplified embodiments shown in Figs. 1 to 4 the auxiliary discharge is caused to pass at a distinct anode 3. However, it would also be feasible to make arrangements so that electrodes 6 and 1, or electrodes 26 and 2! become the anode for the auxiliary discharge, provided that ballasting resistances are used designed to insure their participating to the'same extent in the discharge.

What is claimed is:

1. An electron discharge device comprising an envelope containing an ionizable medium, a cathode and an anode disposed at substantially opposite ends of said envelope, means for maintaining said anode at a positive potential relative to said cathode, a pair of electrodes within said envelope and located between said cathode and anode on opposite sides of the longitudinal axis of said envelope, means for maintaining said pair of electrodes at a negative potential relative to said cathode, and an oscillatory circuit coupled between said pair of electrodes.

2. An electron discharge device comprising an envelope containing an ionizable medium, a cathode and an anode disposed at substantially opposite ends of said envelope, means for maintaining said anode at a positive potential relative to said cathode, a pair of electrodes within said envelope and located between said cathode and anode on opposite sides of the longitudinal axis of said envelope, an electrically conductive connection from each of said pair of electrodes to said cathode including a choke coil, and means for maintaining each electrode of said pair at a negative potential relative to said cathode, and an oscillatory circuit coupled between said pair of electrodes.

3. An electron discharge device comprising an envelope containing an ionizable medium, a cathode and an anode disposed at substantially opposite ends of said envelope, means for maintaining said anode at a positive potential relative to said cathode, a pair of electrodes within said envelope and located between said cathode and anode on opposite sides of the longitudinal axis of said envelope, an electrically conductive connection from each of said pair of electrodes to said cathode including a choke coil, and means for maintaining each electrode of said pair at a negative potential relative to said cathode, means for preventing the engagement of ions within said envelope with those surfaces of said pair of electrodes which do not confront each other, and an oscillatory circuit coupled between said pair of electrodes.

4. An electric discharge device comprising an envelope containing an ionizable medium, a cathode and an anode disposed at substantially opposite ends of said envelope, means for maintaining said anode at a positive potential relative to said cathode, a pair of hollow metallic electrodes within said envelope and located on opposite sides of the longitudinal axis of said envelope, a source of electrons within each of said hollow electrodes, each of said hollow electrodes being apertured to permit electrons emanating from the source therein to enter the space between said electrodes, and means for maintaining said pair of hollow electrodes at a negative potential relative to said cathode.

5. An electric discharge device comprising an envelope containing an ionizable medium, a cathode and an anode disposed at substantially opposite ends of said envelope, means including a stabilizing resistor for maintaining said anode at a positive potential relative to said cathode, a pair of electrodes within said envelope and located between said cathode and anode on opposite sides of the longitudinal axis of said envelope, means for maintaining said pair of electrodes at substantially the same mean potential relative to plasma produced within said envelope, said last means including a connection having an impedance serially connected therein extending from each of said pair of electrodes to a source of unidirectional potential, and an oscillatory circuit coupled between said pair of hollow electrodes.

6. A radio frequency oscillator comprising an electric discharge device whose envelope contains an ionizable medium, a cathode and an anode within said envelope, means for maintaining said anode at a positive potential relative to said cathode to produce a plasma, a pair of electrodes within said envelope and located between said anode and cathode on opposite sides of an imaginary line directly connecting said anode and cathode, connections from said pair of electrodes to unidirectional potential means for maintaining said pair of electrodes at a mean potential relative to said plasma, said connections each including an impedance of high value to radio frequency currents. 5

MAX STEENBECK.

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