US2249494A - High frequency apparatus - Google Patents

Description

July 15, 1941. s. RAMO 2,249,494

HIGH FREQUENCY APPARATUS Filed Dec. 22, 1939 2 Sheets-Sheet 1 Fig. l. /6 /0 {.9 Z2) lhventor: Simon Ramo,

fi a 7?) y His Attorney.

July 15, 1941. s. RAMO HIGH FREQUENCY APPARATUS 2 Sheets-Sheet 2 Filed Dec. 22, 1939 Fig. 5.

Y i m R ww mn u V O Tmmwm a Patented July 15, 1941 HIGH FREQUENCY arrana'ms Simon Ramo, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application December 22, 1939, Serial No. 310,510

5 Claims. (01. 250-36) The invention described herein comprises an improved form of electronic apparatus for use at ultra-high frequencies. While not limited thereto, the invention is especially useful as a frequency multiplier.

In a preferred embodiment, the invention utilizes the combination of means for producing a beam of electrons and a static magnetic field for causing a serpentine deflection of the beam as it progresses through the field. BY Providing an input system for cyclically changing the condi-* tion of the beam as it enters the magnetic field and an output system adapted to be affected by the beam after its passage through the field it proves possible to' obtain certain useful high frequency effects, the nature of such effects being described more fully hereinafter.

The features which I desire to protect herein are pointed out with particularity in the appended claims. The invention itself, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the drawings, in which Fig. 1 is a sectional view of a discharge device suitably embodying the invention; Fig. 2 is a separate perspective view of the magnetic structure employed in the device of Fig. 1; Fig. 3 is a diagrammatic exploded view showing the relationship between the various electrode elements of the device of Fig. 1; Figs. 4 and 5 are diagrammatic representations useful in explaining the invention; and Fig. 6 is a schematic view of an alternative embodiment of the invention.

Referring particularly to Fig. 1 there is shown an evacuated envelope l consisting of glass or other suitable material. Within the envelope and at one end thereof there is provided a cathode I2 and an apertured accelerating electrode l3, these elements constituting an elementary form of electron gun for producing a concentrated beam of electrons. After the electron beam leaves the electrode l3, it is caused to traverse a substantially field-free space defined by the combination of a hollow conductive structure I of rectangular cross-section (see Fig. 3) and by a transversely extending plate IS. The beam is enabled to enter the space referred to by the provision of an appropriate opening II in the plate It. The end of the hollow structure l5 remote from the plate It is assumed to be fully open so as to permit egress of the beam at a variety of different points.

In accordance with my present invention, the electron beam, as it traverses the hollow structure I5, is subjected to a static magnetic fleld of such character as to cause a serpentine deflection of the beam. In the embodiment shown,

this end is accomplished by the use of two elongated magnetic structures l9 and 20 which are so arranged as to produce a magnetic flux in a direction. transverse to the beam path. These structures, which are shown separately in Fig. 2, are so related as to establish two separate parallel regions ofJnagnetic influence within which the flux lines extend in opposite directions. This may be done, for example, by energizing the structures by lengthwise wound coils 22 and 23 which are associated with a source of D. C. potential 24, and which are so connected as to cause the resultant north and south poles of the respective core structures to occupy opposed positions as indicated in the drawings. With an arrangement such as that described, it is possible to cause the electron beam traversing the magnetic structure to describe a serpentine path provided its initial entry to the structure is not colinear with the axis of symmetry of the structure. Dissymmetry of the desired character can be realized, for example, by positioning the entrance opening l! at a point toffset from the central vertical plane of the strucure.

With the aforementioned condition realized, the electron beam is immediately deflected by electromagnetic action as it enters the region 26 which exists between the south pole of the magnet l9 and the north pole of the magnet 20. The subsequent performance of the beam is as indicated in Fig. 4 which is a view looking down at the upper face of the magnetic structure 20. Referring particularly to .the serpentine line A, which may be taken to represent the course of the electron beam for a first selected condition of operation of the apparatus, it will be noted that the first lateral deflection of the beam is followed by an opposite deflection as the deflected beam enters the region 21 between the north pole of the magnet l9 and the south pole of the magnet 20. This reversal of deflection is repeated many times as the beam successively enters the two parallel regions of magnetic infiuence. 4

In order that the action referred to may be employed in the production of useful high frequency eflects, my invention contemplates the provision of an output system arranged to be excited by the beam after its issuance from the magnet structure. Such a system may comprise, for example, a pair of electron-collecting electrodes 29 and 30 connected in push-pull relation factor, it will be readily understood that excita tion of the circuit 32, 33 may be accomplished if some means is provided for causing the beam to oscillate from one electrode to the other at a frequency which approximates the resonant frequency of the circuit.

For the attainment of the object last referred to, provision is made for varying the condition of the electron beam as it enters the magnetic structure. For example, the accelerating electrode l3, which is normally maintained positive with respect to the cathode l2 by means of a battery 35' or other biasing means, may be caused to vary 'in potential in an appropriate manner to produce a change in the scalar magnitude of the beam velocity. Such potential variations may be accomplished, for instance, by connecting a variable voltage source to the electrode 13 as indicated at 31.

Slight consideration will show that variation of the magnitude of the beam velocity will tend to modify the number of deflections which the beam experiences as it traverses the magnetic structures i9 and 20. This may be better understood by referring again to Fig. 4 in which the curve B represents the beam path for a somewhat higher initial beam velocity, than that assumed in connection with the curve A. It will further be noted that as the number of beam reversals changes from odd to even (as in the transition of the beam from the path A to the path B) the efiect of the beam on the output system is simultaneously varied as a result of the shifting V of the beam from electrode 29 to electrode. 30.

As a result of the considerations stated in the foregoing, the relationship between the voltage,

V1, applied to the accelerating electrode l3 and the voltage, V0, developed across the output circuit 32,.33, will be as indicated by the curve C of Fig. 5. (It should be realized, of course, that this curve represents the idealized case and ignores distortion factors which are inevitably present in a system such as that described.) Mathematically, the relationship between these quantities may be either Vo=sin Vi or Vo=COS Vi depending upon the selected point of origin. Furthermore, if V1 is itself a sinusoidally varying quantity (as Vi=E sin wt, or Vi=E cos wt) and if the operating point is properly adjusted, as by variation of the voltage of the biasing battery 35, these relationships may be still further rewritten as Vo=sin (E sin wt) Vo=cos (E cos wt) Another use, and one which I consider to constitute the preferred embodiment of my inven-- tion consists in the accomplishment of frequency multiplication efiects. In this connection it will be understood that if the limits of the cycle of beam velocity variation are made sufliciently broad the total change in the number of beam reversals for a single cycle of such variation can be made very much greater than one. As a consequence, the beam may be :caused to shift from the electrode 23 to the electrode 3! many times for each complete cycle of the voltage applied to the input electrode l3, and frequency multiplication effects will be obtained.

In order that the results which are described in the foregoing may be obtained most effectively, it is desirable that the ratio of average beam velocity to the strength of the magnetic .fleld be low so that a complete reversal of the beam deflection may occur within a relatively short distance measured along the normal axis of the beam. Furthermore, in order that the total number of beam reversals may be relatively great (to permit a correspondingly great change in the number of beam reversals for each cycle of beam velocity variation) the magnetic structure should extend for a substantial distance along the beam path. In some cases the presence of the relatively large masses of metal required by the magnetic structures may make it desirable to connect the tube II] to a continuously operated vacuum pump in order to avoid deterioration of the vacuum within the device by gases occluded by the metal parts.

The effects described in the foregoing may be obtained in an alternative fashion by varying the initial direction of the beam as it enters the magnetic field, rather than by varying only the scalar magnitude of the beam velocity as in the arrangement just described. This alternative mode of operation may be realized, for example, by the use of an arrangement such as that which is illustrated in Fig. 6. (In this figure, parts which function in a manner similar to corresponding parts illustrated in Fig. 1 bear identical numerals.) In this case, the condition of the beam as it enters the magnetic structure is varied by means of a pair of electrostatic deflecting plates 40 and 4|, these plates being connected to an input circuit which includes a source of alternating potential 42. In order that the beam may enter the region defined by the magnetic parts [9 and 20, irrespective of the amount of deflection produced by the electrodes 40 and 4 l the plate I6 is provided with an elongated slot 43 through which the beam may pass. As the direction of the beam entering the magnetic field is caused to vary by the action of the plates 40 and 4 l, a corresponding change will occur in the number of deflection reversals which are produced as the beam progresses through the magnetic structure. Consequently, if 'an appropriate ratio of magnetic field strength to average beam velocity is maintained, the variation in number of deflection reversals can be made greater than one so that a multiple shifting of the beam from electrode 29 to electrode 30' and back will occur for each cycle of variation of the input voltage provided by the source 42. By this means frequency multiplication or other useful effects can be obtained in accordance with the principles previously described.

It is recognized that velocity is a vectorial quantity having both a scalar component of mag- I nitude (commonly designatedfspeed) anda comvariation produces a in speed, or a simultaneous variation of both speed and direction.

While I have described my invention by reference to particular embodiments thereof, it will be understood that numerous modifications may be made by those skilled in the art without departing from the invention. 1, therefore, aim in the appended claims to cover all such equivalent variations as come within the true spirit and scope of the foregoing disclosure.

What I claim as new and desire to secure by Letters Patent of the United States, is: v

1. High frequency apparatus including means for generating a beam of electrons, means for producing in adjacent regions bounding the beam path static electron-deflecting fields of opposite deflecting efiect, whereby the beam is caused to follow a. serpentine course as it is affected first by one field and then by the other, an output circuit to be excited by the beam after multiple deflection thereof by the said fields, the circuit being of such character that the effect of the beam thereon is variable with the number of deflection reversals, and means acting on the beam prior to its traversal of the said fields to vary its susceptibility to deflection by the fields and thereby correspondingly to vary the excitation of the output circuit.

2. High frequency apparatus including means for generating a beam of electrons, means for producing on opposite sides of the beam path oppositely directed static magnetic fields transverse to the beam whereby the beam is caused to follow a serpentine course as it is affected first by one field and then by the other, an output circuit to be excited by the beam after multiple deflection thereof by the said fields, the nature of such excitation being variable with the number of deflection reversals, and means acting on the beam prior to its traversal of the said fields to change its susceptibility to deflection and thereby correspondingly to vary the excitation of the output circuit.

3. A frequency multiplier including means for generating a beam of electrons, means for producing on opposite sides of the beam path oppositely directed static magnetic fields transverse to the beam whereby the beam is caused to follow a serpentine course as it is affected first by one field and then by the other, the total number of deflection reversals experienced by the beam being a function of the initial beam velocity, an output system having a component thereof positioned to be variably affected by the beam depending upon whether the number of beam reversals is odd or even, and means for cyclically varying the initial velocity of the beam between limits sufficiently broad so that one cycle of such charge greater than one in ducing on opposite sides of the beam path oppositely directed static magnetic fields transverse to the beam whereby the beam is caused to follow a serpentine course as it is affected first by one field and then by the other, the total number of deflection reversals being a function of the initial direction of the beam as it enters the region of influence of the said magnetic fields, an output system having a component thereof which is variably affected by the beam depending upon Whether the number of beam reversals is odd or even, and means acting on the beam prior to its traversal of the said magnetic fields for cyclically varying the initial direction of the beam between limits sufficiently broad so that one cycle of variation produces a change greater than one in the number of deflection reversals experienced by the beam, whereby the frequency of variation of the effect of the beam on the output system is a multiple of the frequency of variation of the initial beam direction.

5. A frequency multiplier including means for producing a beam of electrons, means producing a first static magnetic field in a region which extends for a substantial distance along the beam path, said field being transverse to the beam path so that it produces lateral deflection of the beam, means providing a second magnetic field in opposite direction to the first and in a region closely adjacent to the first whereby it tends to reverse the deflection of the beam initially produced by the first field, both said fields being of sufficient spatial extent to assure a multiple reversal of the beam deflection as a result of their conjoint action, the number of such reversals being a function of the velocity of the beam as it enters theflrst field. an output circuit having a component thereof arranged to be affected by the beam after its issuance from the said magnetic fields, the said circuit component being so positioned that the effect of the beam thereon is variable in accordance with whether the number of beam deflection reversals is odd or even, and means for cyclically varying the initial velocity of the beam within limits sufficiently wide so that one cycle of such variation produces a change greater than one in the number of deflection reversals, whereby the frequency of variation of the effect of the beam on the said output circuit is a multiple of the frequency of the said beam variation.

SlMON RAMO.

Images