US2086904A - Frequency multiplier - Google Patents

Description

July 13, 1937. J. EVANS FREQUENCY MULTIPLIER Filed Nov. 30, 1934 INVENTOE QQSQQ ERIE basi .8

description when'read in connection'with the 35 and of a shunt connected variable capacitor Patented July 13, 1937 UNITED STATES FREQUENCY MULTIPLIER John Evans, Riverside, N. J., assignor, by mesne assignments, to Radio Corporation of America,

New York, N. Y., a

corporation of Delaware Application November 30, 1934, Serial No. 755,392

8 Claims.

This invention relates to frequency multipliers and more particularly to a device in which frequency multiplication is obtained by ,suitable control of an electron beam in a cathode ray tube whereby a fundamental frequency impressed upon the deflecting circuits of such a tube may be multiplied to any desired frequency, harmonic or otherwise.

My invention has particular utility in ultra high frequency work. It has been found very diflicult to economically obtain satisfactory frequency stabilization of ultra high frequencies. My solution of the problem enables one to use a crystal-controlled oscillator or any other oscillator of a fundamental frequency which can be accurately regulated and then to develop oscillations of any desired harmonic frequency under control of the fundamental frequency. The apparatus for accomplishing this result is so characterized that the fundamental frequency may be multiplied many fold. The desired factor of multiplication is obtained by suitable design of one of the electrodes in a cathode ray tube. For a given tube this factor remains invariable, although, according to one modification of my invention presently to be described, a choice between several factors may be had.

In carrying out my invention I have chosen to utilize a cathode ray tube because it provides a dependable means for multiplying the frequency of any desired fundamental source without resort to apparatus having any movable mass. My application of the cathode ray tube, therefore, provides further evidence of the many advantageous r uses to which such a device maybe put.

As is well known, energy can be so applied to the deflection of a focused beam of electrons as to produce a motion which is substantially devoid of inertia.

It is among the obj'ectsof my invention to provide a frequency multiplier of the type. hereinabove suggested in which any desired factor of multiplication may be obtained.

It is anotherobject'of my invention to provide a frequency multiplier in which currents of considerable amplitude andat ultra high fre-' quency may be generated. Y

Still another object of my invention is to proa vide suitable apparatus for stabilizing; an ultra high frequency current. v

The foregoing and other objects and advantages of my invention will be more clearly understood uponreference to the following detailed accompanying drawing in which Figure 1 shows diagrammatically the circuit arrangements and electrode arrangements for a cathode ray tube as used in my invention, and

Fig. 2 is a plan view of a modified form of one of the electrodes such as may be used in the cathode ray tube otherwise shown in Fig. l.

Referring now to Fig. 1, I show a specially constructed cathode ray tube l, the envelope of which contains a usual cathode 3 having, if desired, a separate heater element 5, a beam focusing anode I, an accelerating anode 9, and further accelerating electrodes, l3 and 15. Beam deflecting means may beprovided in the form of electrostatic plates l1 and [9 for horizontaland vertical deflection respectively. In place of the electrostatic plates, magnetic deflecting coils (not shown) may be provided, if desired. In either case, the deflecting elements are included in circuits from a single-phase or polyphase source of energy. If a single-phase so'iirce only is available, 'as shown at 2!, then a phase shifting device 23 may be provided in one of the circuits which includes the deflecting means ll. One of the electrostatic plates [l and also one of the plates l9 may, if desired, be grounded as at 25. In order to control the amplitude of beam defiection I may provide a rheostat 21 having a movable tap 29 which is also grounded.

The action of the cathode ray tube. insofar as it is controlled by the electrodes thus far described, is such as to project a beam of electrons rotatably-against the target electrode ll. Some of the electrons in the stream are, therefore, permitted to accelerate through the apertures 3| and to continue their course in the direction of the electrode l3. sharply focused that substantially the full force of the electron gun will be directed at one time through a single hole 3! and next against the wall of the target ll adjacent two of the holes. The beam is, therefore, intermittently intercepted. The electrons emerge intermittently on the other side of the target H and are further directedand controlled in their course back and :forth in the cylindrical zone bounded by the electrodes ll andl3 at the two ends thereofand by acircumferential' electrode l5 which is preferably located mid-way between the other two. A source of direct current 33 is provided in connection with the electrode {5 so as to render a The electron beam is so 31. A mid-tap on the inductance 35 connects with the negative side of the source 33. Suitable potentials are applied between the remaining electrodes of the cathode ray tube as indicated at 39, M and 43, respectively.

It has been found desirable to provide still further means for directing the course of the electrons after they have emerged from the orifices 36 so that their paths shall be substantially parallel with the axis of the electron gun up until they are attracted to the ring-shaped anode l5. Such a means may comprise a magnetic coil d5 so surrounding the enlarged cylindrical portion of the cathode ray tube I as to produce a magnetic field having its lines of force substantially parallel to the tube axis. Any suitable energizing source such as the battery 41 may be provided for the coil 65. The velocity of the electrons is made such that the secondary electrons emitted by the impact of the primary electrons progress back and forth repeatedly between the electrodes ii and i3, gradually releasing more and more electrons from these emissive elements until the beam itself attains considerable magnitude compared with that of the beam projected by the electron gun. It is, therefore, possible under these circumstances to control the generation of oscillations of ultra high frequency in an output circuit which includes the shunt connected impedance 35 and capacitor 31, this result being obtained by the employment of comparatively low power applied to the electron gun and to the defiecting circuits. The increase in power output is derived'largely from the source 33 which has no efiect upon the action of the electron beam prior to its emergence through the apertures 3i According to a modification of my invention as shown in Fig. 2, the target Ha may be provided with apertures of diiferent shapes and sizes so that different factors of multiplication may be obtained by merely controlling the radius of curvature of the electron beam as it is intercepted by this target. Thus suitable adjustment of the rheostat 21-29 enables one to vary the deflecting force as applied both to the horizontal and to the vertical deflecting elements simultaneously. The circular path of the electron beam is, therefore, maintained; but in one case if its radius is as shown at r, a low factor of multiplication will be obtained because only the apertures 3la extend to Within this radius. If the deflecting force is increased to an intermediate value, then the path of the electron beam may have a radius r so as to comprehend both the apertures 3i... and additional apertures 3'11. With the employment of a maximum deflecting force, the radius of the electron beam may be increased to 1 thereby comprehending all of the apertures in the target Ha including apertures 3h, 3 lb and Me. Thus different factors of multiplication may be obtained at will.

It is apparent that upon the employment of 7 any fundamental frequency a multiplication of that frequency may be obtained, the factor of multiplication being determined solely by the aoeaoos Utilization of the multiplied frequency may be had by suitable connections or coupling with the output circuit in any well known manner.

Although I have disclosed herein certain specific means for accomplishing the objects of my invention, these are given merely by way of example and are not to be construed as limitations to the scope of my invention. It will be apparent to those skilled in the art that my invention is not thus limited, but many modifications may be made without departing from the scope of my invention as set forth in the appended claims.

I claim as my invention 1. In a device of the class described, an electron discharge tube, an apertured electrode separating two portions of said tube and including therein a plurality of equally spaced apertures uniformly disposed with respect to the center of said electrode, means including other electrodes in one portion of said tube for projecting a stream of electrons successively through different apertures in the first said electrode and into the other portion of said tube, additional electrodes in the last said portion of said tube, a resonant output circuit connected between one of the last said electrodes and the apertured electrode for producing secondary emission under control of the stream of electrons first mentioned, whereby oscillations of high frequency and high power are set up and a source of polarizing potential connected between another of said additional electrodes and a point intermediate the ends of said resonant output circuit.

2. Apparatus in accordance with claim 1 further characterized in that the first mentioned electrode and one other electrode of the tube portion into which the electron stream is last projected are made emissive and another of said additional electrodes is a ring shaped anode interposed between said emissive electrodes, and charged positively with respect to said emissive electrodes.

3. In an oscillation generator, a cathode ray tube having heater, cathode, and focusing electrodes of the electron gun type and having both horizontal and vertical beam deflecting means, and a plurality of additional electrodes for producing an accelerating electronic emission beyond the zone of beam deflection, one of said additional electrodes having a plurality of apertures concentrically spaced and increasing in number with increasing distances from the center of said electrode and being so related as to alternately intercept and pass electrons therethrough, means for producing electron multiplication between said apertured electrode and one of said additional electrodes by secondary emission from each of the last said electrodes, an output circuit connected between said apertured electrode and one of said additional electrodes and reso nant to the frequency of interception and passage of said electrons, and means for biasing the electrodes connected to-said output circuit with respect to one of said additional electrodes positioned intermediate said two connected electrodes comprising a connection intermediate the ends of said output circuit and a source of potential connected between said connection and said one additional electrode.

4. In a frequency multiplier, an electron discharge tube having a cathode, a beam focusing electrode, horizontal and vertical beam deflecting means and a plurality of accelerating electrodes, one of the last said electrodes having apertures therein through difierent ones of which in electron beam may be successively projected, a. source of single phase alternating current, means for splitting said alternating current into at least two phases and acting upon the beam deflecting means for timing recurrent rotative deflections of the electron beam, means includin said apertured electrode for producing secondary emission and multiplication of electrons in that portion of the beam beyond the apertured electrode, a polarized output circuit for said discharge tube connected to said means for producing secondary emission and characterized in that an alternating current may be produced therein at a frequency determined by the rate of interception of said electron beam by different por- "tions "of said apertured electrode between the apertures thereof, and further characterized in that said output circuit includes an inductance having a center-tap and a capacitance shunting said inductance, the center-tap being connected through a source of direct current potential to a ring-shaped anode, and the terminals of. the inductance being connected respectively with different ones of the electrodes comprised in the means for producing secondary emission, whereby said output circuit is made resonant to the frequency of the passage of electrons through said apertured electrode.

\5, A frequency multiplier in accordance with claim 4 further characterized in that there is provided a source of magnetic flux the lines of which co-mingle with said electron beam beyond said apertured electrode and have a trend parallel to the direction of said beam.

6. A frequency multiplier in accordance with claim.4 further characterized in that said output circuit is tuned to a frequency harmonically related to the frequency of said alternating current that acts upon the beam deflecting means.

7. In an oscillation generator and frequency multiplier, a source of two-phase current of. a fundamental frequency, a target having apertures disposed in circular formation, the number of apertures being determined by the multiplication factor to be applied to the fundamental frequency, a cathode ray tube having said target as one of its anodes, and having other electrodes serving as an electron gun, beam deflecting means for so controlling an electron discharge from said gun as to direct the beam successively through diflferent ones of the apertures in said target, connections from said source of two-phase current to said beam deflecting means for controlling said beam, and secondary emission means including additional electrodes on the opposite side of the target with respect to said electron gun and said apertured target and including a tuned output circuit interconnecting the additional electrodes and the target for producing an amplified alternating current at the desired multiple frequency, and comprising a center tapped inductor and a capacitor and a source of a biasing potential connected between said center tap and a ring shape electrode intermediate said secondary emission means. a

8. In an oscillation generator, an electron discharge device having a cathode, a beam-focusing anode, and an accelerating anode, horizontal and vertical beam deflecting means for said device, means including a source of alternating current and a phase-shifting device for so energizing said deflecting means as to effect a rotary movement of the electron beam within said discharge device, a shield having a plurality of holes arranged in the path of said electron beam, means for accelerating electrons after they are shot through said shield, said means comprising additional electrodes in said device, and means including a source of energy and an output circuit comprising a center-tapped inductor and a capacity connected with said shield and with said additional electrodes for producing secondary emission'from said shield said source of energy being connected between said center tap and a ring shape electrode positioned between said secondary emission electrode and for generating in said output circuit oscillations of a frequency which is determined by the speed of rotation of the electron beam and by the number of holes in said shield.

JOHN EVANS.

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