US2463710A - High-frequency generator - Google Patents

Description

HIGH-FREQUENCY GENERATOR Filed Sept. 24, 1945 I) ,2 D O \J 9, t CONTROL 8 OSCILLATOR MIMI lmlml mml q a; LI

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INVENTOR.

ANGELO MONTANI ATTORNEY Patented Mar. 8, 1949 HIGH-FREQUENCY GENERATOR Angelo Montani, Woodhaven, N. Y., assignor to Automatic Electric Laboratories, Inc., Chicago, 111., a corporation of Delaware Application September 24, 1945, Serial No. 618,352

3 Claims. 1

The present invention relates to high frequency generators, and particularly to high frequency generators of the electron beam type.

Previously proposed electron beam high frequency generators have employed various forms of commutators which are scanned by an electron beam. Interception of the beam by alternate commutator segments produces oppositely directed impulses in a resonant circuit coupled to the commutator, thereby sustaining oscillations in the resonant circuit when the number of pairs of commutator segments scanned per second is equal to the natural frequency of the resonant circuit. In these prior art devices the frequency and waveform of the output voltage is determined largely by the nature of the load circuit. When the circuit Q of the resonant circuit is very high, as it is in the case of a cavity resonator, a relatively pure sinusoidal waveform will be produced in the output circuit.

The principal object of the present invention is to provide a new type of high frequency generator. or frequency multiplier, wherein the frequency and waveform of the output voltage is not dependent upon circuit constants, but is instead determined by the physical construction of the generator.

Another object of the invention is to provide an electronic high frequency generator which is adapted to produce an output current having any desired waveform.

Still another object of the invention is to provide an improved means for controlling the generation of high frequency currents by lower frequency currents.

Briefly, these objects are accomplished by providing a specially shaped collecting electrode in a tube structure similar to a conventional cathode ray tube. The collecting electrode is cyclically scanned by an electron beam and is shaped so that the length of the path traversed by the electrons in the beam varies throughout the scanning cycle. This variation in beam length is related to the scanning rate and to the electron velocity so as to produce currents having any desired frequency and waveform in an output circuit connected to the collecting electrode.

The invention will be better understood from the following description when considered in conjunction with the accompanying drawing, in which:

, Fig. 1 discloses one form of the invention in whichthe electron beam is cyclically deflected along a rectilinear scanning path;

' Fig. 2 is a modification of Fig. 1 in which the electron beam is deflected so as to scan a circular path on a ring-shaped collecting electrode;

Fig. 3 illustrates the waves produced in the electron beam when a deflecting voltage of recurrent triangular waveform is applied to the deflecting electrodes of the tube shown in Fig. 1; and

Fig. 4 illustrates the waveform of the current flowing to the collecting electrode of the tube shown in Fig. l for different angular positions thereof when the electron beam is deflected as shown in Fig. 3.

Referring to Fig. l of the drawing, there is shown a cathode ray tube having the conventional heater I, cathode 2, and beam forming electrodes 3, 4 and 5, all of which are energized by a suitable battery 6, or the like. The pencillike electron beam, indicated by the broken line '3, passes between a pair of deflecting electrodes 8, 'which are positioned on opposite sides of the beam axis. It is to be understood that the equivalent magnetic deflecting coils or other suitable means may be substituted for the electrostatic deflecting electrodes, if desired. The electron beam is caused to scan a rectilinear path by ap-- plying an alternating voltage from a suitable source, such as a control oscillator 9, to the deflecting electrodes 8.

The collecting electrode H! is a plate which is positioned in angular relation to the beam axis. The upper and lower portions of the plate are formed at an angle to the center section, as indicated. The collecting electrode is connected to battery 6 through a radio frequency choke ll, across which the output voltage appears when the tube is in operation.

In considering the operation of the tube it will first be assumed that the alternating voltage applied to the deflecting electrodes 8 by the control oscillator 9 is of triangular waveform and has a period several times shorter than the transit time of the electrons from the deflecting electrodes to the collecting electrode. Triangular waves will then be produced in the beam as illustrated in Fig. 3. The electrons all travel in straight lines at the same velocity causing these waves to travel towards the right of the figure. It is obvious that if the collecting electrode was a plane surface located perpendicular to the beam axis, as at A, that the number of electrons impinging on the collecting electrode per unit of time would remain constant. The resulting cur rent in the output circuit is illustrated by the straight line A in Fig. 4. If the collecting electrode were rotated about an axis perpendicular to deflecting electrodes. desiredphase relation may be achieved by conthe beam axis, and to the scanning path, to the position C a large number of electrons would impinge on the collecting electrode simultaneously, following which electrons would impinge thereon at one-half the rate as when the collecting electrode occupied the position A. The resulting output current is shown by curve C in Fig. 4. ,If, the collecting electrode-were rotated to an intermediate position such as'B' in Fig.3 the output current would follow a curve such as B in Fi 4. which one side is approximately perpendicular to the wave axis, is applied to the-defiectingelectrodes in place of a triangular .voltagewave, an output current similar to curve CWlll be obtained with the lower value of current reduced to'Ze-ro. The effect of a commutator may thus be obtained, but with the advantage that all of the energy contained in the beam is utilized.

In the preceding paragraph it was assumed thatgatriangular voltage .wave was applied to the deflecting electrodes for simplicity of explana- ..tion. If the deflecting voltage is sinusoidal then sinusoidal waves will .beproduced in the beam similar; to the triangular waves shown in Fig. 3.

.These .Waves are nottrue sinusoids, of course,

since the amplitude increases progressively with -.the.distance, along the :beamaxis. .In this case the output current will stillbe constant if the collecting electrode is a plane surface positioned as.at, A of. Fig. 3. If the collecting electrode was rotated to the position C an output current similarto that shown in curve C of Fig. 4' will be obtained, but with. rounded corners. With the col- ,lecting electrode rotated. to the position B the rounding of the corners in the output wave would bemore pronounced. and wouldresult in a wave in, orderto use the tube as: a-self-excited oscilla- .tor.

.Instead. of using, a. collecting electrode having a singleplane surface, the invention contemrplates the use-ofa collectingelectrodev havinga plurality of intersecting plane surfaces which are successively-scanned bythe electron beam as i]- lustrated in. Fig. 1. ,-For each scanning cycle the .output current wil1:pass.through ,a. number of cycles equal. to .thehnumber. of -plane. surfaces in .the.collecting-electrode. .Thus with the collectingv electrode shaped ,as-in Fig. 1..an-. output cur- .rent having threetimes the frequency of. the defleeting voltage will be obtained.

.. In. order to provide vagreater frequency multi- D1ication.factor the collecting electrode may be .made inthe fOIfm.0f a corrugated ring l2 as showninFig. 2. Anadditional pair of deflecting electrodes l3 are provided fordeflecting the electron beam perpendicular to ,the plane of the drawing. 'The e1ectron'beam 1 iscaused' to scan a circular path byapplying deflecting voltages which are. in phase quadrature to the two sets of By way of example, the

necting .a suitable 90 phase-shifting network l4 "between theoscillator 9 andthe deflecting electrodes 8. In thiscase, instead of producing waves in the beam 1 ,a conical spiral will be formed thereby. If the, collecting electrode was a plane ring jshaped electrode located perpendicular to If a saw-toothed voltage wave,-::of

- tating beam,

.desired output waveform. The potentials applied tothe accelerating electrodes of the beam forming-gun must be adjusted to provide an electron velocity which isproperly related to the depth of; the corrugations in the collecting electrode and the scanning rate of the beam in order to obtain the optimum, conditions for maximum output.

"'Whiie what is now considered to be the preerred-form of the invention has been illustrated,

it is to be understood that numerous modifications may be incorporated therein Without departing from thetrue spirit and scope of the .invention as defined in the subjoined claims.

.What is claimed is:

1.-,In a high frequency generator, means ;-f,or

producing a beam of electrons, meansfor causi-ng said beam to cyclicallyscan a fixed path,-.a

collectin electrode disposed in said -path,.said

collecting electrode being shaped sov as to cause the transit time of the electrons impinging thereon to cyclically increase anddecrease during'each scanning cycle to thereby produce a currentfiow having a waveform dependent on the-shape-of said collecting electrode.

.2. Ina waveproducer, a source of electrons, means for deriving a, beam of electrons from-said source, means for rotating said beam, a collecting electrode disposed in the patriot said r0 said collecting electrode being shaped so that the distance traversed by the electrons in said beam between said source and" the point where they impinge on said collectingfelectrode :alternately increases and decreases in ;a

continuous and periodic manner during rotation of said beam.

3. -,In a frequency multiplier, a source: of. electrons, means for deriving a beam *of electrons having a constantvelocity: and uniform density from. said source, means for causing said beam' to cyclically scan a fixed path a collecting electrode disposed in said path, said electrode being shaped so asto cause the length of said beam, measured from saidsource to the pointat whichtheelectrons impinge upon said electrode, to increase during a portion of each scanning cycle. and to decrease during .another portion of each scanning -cycleto thereby cyclically vary said beam length a. plurality ofv times during; each scanning, cycle, whereby a current having a frequencywhich-is a multiple of the scanning frequency. is produced insaid collecting electrode.

ANGELO. MONT-AMI.

-REFEBENCES CITED The following references are ofrecord ,inthe file of this patent:

UNITED STATES PATENTS Number Name Date 2,026,892 Heintz Jan. 7,1936 2,157,749 Du Mont ..May 9,1939 2,173,193 Zworykin Sept. 19,;1939 2,288,694 Fry July 7,,1942 2,307,69 3 Linden Jan.'5,;1943

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