US2534545A - Device comprising an electric discharge tube for ultra high frequencies - Google Patents

Description

F. COETERIER 2,534,545 1 DEVICE COMPRISING AN ELECTRIC DISCHARGE TUBE v FOR uummmn FREQUENCIES Filed July 20, 1946 Dec. 19, 1950 FRZDfR/A OZ 7273/51? Patented Dec. 19, 1950 CHARGE TUBE QUENCIES FOR ULTRA HIGH FRE- Frederik Coeterier, Eindhoven, Netherlands, as-

signor to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application July 20, 1946, Serial No. 685,148 In the Netherlands September 10, 1943 Section 1, Public Ilaw 690, August 8, 1946 Patent expires September 10, 1963 3 Claims.

This invention relates to a device comprising an electric discharge tube for amplifying ultrahigh frequencies, and has more particularly for its purpose to reduce the input damping of such a tube.

When operating with ultrahigh frequencies, such as those associated with wavelengths of decimeters and centimeters, th difliculty is experienced that the damping of the input circuit steadily increases. This is primarily due to the fact that the transit time of the electrons is no' longer short with respect to the frequency of the control voltage at the control electrode. This involves phase displacements, due to which the control is no longer energyless. This control energy causes a damping of the input circuit.

Efforts have now been made to reduce this difliculty as much as possible by reducing the distance between cathode and control electrode, in order to keep the transit time short. This expedient entails, however, the drawback that the cathode-control electrode capacity increases, due

to which the input circuit is short-circuited capacitatively.

Furthermore, it has been sought materially to increase the velocity of the electrons by forming the" stream of electrons into a beam and by making use of high voltages, thus shortening sufilciently the transit time, so that comparatively large cathode-control grid distances can be used, whilst the cathode-control grid capacity remains 7 comprising a plurality of auxiliary electrodes,

amongst which at least one control electrode, and in which the electrons issuing from the cathode are concentrated into a beam, in such a manner that the transit time of the electrons from cath- 'ode to control electrode amounts to half a period of oscillation of the control frequency or to a multiple thereof. Between cathode and control electrode are provided one or more auxiliary electrodes, such as an accelerating grid having a positive potential and a suppressor grid having zero potential or a negative potential.

A device according to the invention has various advantages, as will be explained by reference to the accompanying drawing in which a device in accordance with the invention is diagrammatically represented. v

In the figure, the reference number i deno a cathode, 2 a control electrode, 3 an accelerating electrode, 4 a suppressor electrode for secondary electrons, 5 an anode or collector electrode, and 6 and I the output electrodes for carrying off energy. An evacuated envelope encloses the electrodes. Voltage supplies and input and output circuits are indicated in a self-explanatory manner. Parallel with the axis of the electrode system is produced a magnetic field which extends between the poles 8. This magnetic field brings about such a concentration of the electrons that they follow paths approximately parallel with the axis of the tube. The voltages on the electrodes are so chosen that the transit time of the electrons from the cathode l to the control electrode 2 amounts to one half cycle of the control voltage on 2 or to a multiple thereof. In this case the electrons repelled by the control electrode reach again the space 9 between cathode i and accelerating electrode 3 after 2X /2 cycle. These paths of the electrons are concentrated by the magnetic field in such a manner that the electrons spread as little as possible. Consequently, in the space 9 between the cathode I and the electrode 3 a considerable space charge ensues which suppresses the cathode current. The returned elec-' trons now travel several times to and fro be tween the electrode 2 and th cathode l before passing through the control electrode 2. The operation is as follows: Suppose the control grid 2 has just become positive. The electrons will flow from the cathode to 2. Upon these electrons arriving at 2 after half a cycle, the control voltage will again have dropped to zero and the negative half cycle of the control voltage will begin. Part of the arriving electrons will consequently be checked and sent back. These electrons reach the cathode space 9 half a cycle later when 2 just becomes positive again. This is repeated. Owing to the space charge at 9 a decrease in cathode current will occur. The practical result is that the anode current is not only reduced by the negative control voltage of 2, but also by the space charge at 9. Thus an increased control efiect occurs, which is stronger as the spreading of the electrons is smaller and the returning electrons travel to and fro more often.

3 Owing to this efiect the control action of 2 is thus strengthened. As a result of the large distance between cathode l and control grid .2 and of the screening effect of the electrodes 3 and 4, the cathode-control grid capacity is very low, and yet a sensitive control i ensured. The energy may be carried oii according to the induction or drift principle by means of the electrodes 6 and 1. Consequently, it is essential to take care that the transit time of the electrons between cathode and control electrode has exactly the correct value. The additional control effect thus obtained is much strengthened by the concentration of the electron paths, since without forming the electron paths into a beam the returning electrons would immediately or very soon find their way to the accelerating electrode 3"for the reater part. Hence, an incorrect value of the concentrating magnetic field (which may be replaced by any suitable concentrating device) makes the mutual conductance quickly fall to about In a practical form of constructionaccording to the invention the distance between cathode l and control electrode 2 is 8 mms, similarly to the distance between electrode 2 and anode-5. A positive potential of about 760 volts is applied to electrodes 3, E and l as well as to the anode 5. Electrode 2 operates at zero potential. In this arrangement the transit time between cathod and control grid amounts to /2 of a period of oscillation at a wavelength of mms.

In an arrangement in which the cathode-control grid spacing is 4 mms. and with the above noted voltage applied to the electrodes, a transit time equal to one period of oscillation is obtained.

What I claim is:

1. An ultra high frequency electron discharge device having a substantially predetermined operating frequency, comprising an evacuated envelope, a cathode within said envelope, a collector electrode within said envelope, a control electrode interposed between said collector elect-rode and cathode, an accelerating electrode interposed between said control electrode and said cathode, beam forming means including means to produce a magnetic field of predetermined intensity en closing the electron path and having lines of force substantially parallel to the electron path from the cathode to the collector electrode and terminal means for said control electrode for applying thereto a voltage of predetermined mag-'- nitude, said control electrode being spaced at-a distance from the cathode at which the transit timeof electron travel from said cathode tosaid controlelectrode at said predetermined. voltage.

is substantially equal to n half periods .of. said operating frequency where n is. a whole number and that electrons repelled from said control electrode are returned to substantially their point-of emission from said cathode.

2'. An ultra-high. frequency electron discharge tube system having a substantially predetermined operating frequency, comprising an evacuated envelope, a cathode within said envelope, a collector electrode within said envelope, a control electrode interposed between said collector electrode and said cathode and havinga D.-C. po-

tude, said control electrode being spaced at a distance from the cathode at which the transit time of electron travel from said cathode to said control electrode at said predetermined voltage is substantially equal to n half periods of said operating frequency where n is a wholenumber and that electronsrepelled from said control electrode are returned to substantially their point of emissionfrom said cathode.

3. An ultra-high frequency electron discharge tube system having a substantially predetermined operating, frequency, comprising an evacuated. envelope, a set of elements within said envelope.-

comprising a cathode, a collector electrode, an accelerating electrode interposed between said cathode and said collector electrode, a suppressor electrode interposed between said accelerator.

electrode and. said collector electrode, a control electrode interposed between said suppressor electrode and said collector electrode, a first output electrode interposed between said collector electrode and said control electrode, anda second; out-put electrode interposed. between said first,

output electrode and said collector electrode, each of said elements having a D..-C. potential with. respect to each other to form electrons emanate.

ing from said cathode into an electron beam. di-

rected toward said collectorelectrode, means to.

produce a magnetic field of predetermined intensity enclosing theelectron path and having lines of force substantially parallel to the -elec-.

tron path from the cathode to the collector electrode,. and terminal means for said control elec-,

trode for applying thereto a voltage of predetermined magnitude, said. control electrode being spaced at a distance from the cathode. at which the transit time of. electron travel from said.

cathode to said control electrode at said prede termined voltage issubstantially equal to n halt periodsof saidoperating frequencywhere n is a whole. number and that electrons repelled from said control electrode are. returned, substantially.

totheir point of emission fromv saidcathode.

FREDERIK COETERIER;

REFERENCES CITED The following references are of record in the.

file of this patent:

UNITED STATES PATENTS Number Name Date 2,149,024 Lindenblad Feb. 28, 1939 2,239,677 Jobst Apr. 29, 1941 2,244,747 Varian et a1. June 10, .1941 2,272,605 Heising Feb. 10,1942 2,347,797 Posthumus et all May '2, 1944

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