US2565410A - Controllable electrical delay means - Google Patents

Description

g- 21, 1951 J. w. TILEYI H 2,565,410

CONTROLLABLE ELECTRICKL DELAYMEANS Filed Sept. 20, 1944 2 Sheets-Sheet 1 FIG. 1

n. n rH n, 1

IN V EN TOR.

Aug. 21, 1951 J. w. TILEY 2,565,410

CONTROLLABLE ELECTRICAL DELAY MEANS Filed Sept. 20, 1944 2 Sheets-Sheei'. 2

70 FIG 5 i 4.

32 35 MO DULATING 1 VOLTAGE soulzcz EWCITER Patented Aug. 21, 1951 2,565,410 CONTROLLABLE ELECTRICAL DELAY MEANS John W. Tiley, Philadelphia, Pa., Philco Corporation, Philadelphia,

ration of Pennsylvania Application September 20, 1944, Serial No. 554,960 8 Claims. (Cl. 313-457) The present invention relates to space discharge apparatus and concerns particularly apparatus of the type in which an electric emission beam or electronic beam is produced.

An object of the invention is to provide improved methods and apparatus for producing time delay effects.

Another object is to provide improved methods and apparatus for controlling delay of high frequency signals without employing filter networks.

Another object is to provide arangements for producing the same absolute delay for all ire. quency components of a signal.

Still another object is to provide arrangements for utilization or for control of transit time effects.

An additional object of the invention is to provide means in electron beam apparatus for lengthening the beam which may be utilized within a given space.

Still another object of the invention is to provide transit time apparatus in which the length of an electronic beam may be varied to vary time delay of the signal or for phase modulation.

Other objects of the invention are to provide means for varying the length of an electronic beam spiral for varying the tightness or pitch of such a spiral and for varying the radius of such a spiral.

A further object of the invention is to provide means for multiplying the effective length of the path of a stream of electrons.

Other and further objects, features and advantages of the invention will become apparent as the description proceeds.

In carrying out the invention in one of the preferred embodiments thereof, an evacuated tube or the like is provided having a concentric electrode arrangement with a cathode at the center, a ring-shaped anode and means for producing a magnetic field having a magnetic axis substantially coaxial with the anode and the cathode of the tube. Suitable beam forming and focusing electrodes are provided so that, disregarding the magnetic field, an electronic beam or a plurality of electronic beams tends to leave the cathode and to travel radially toward the anode. As a result of the action of the magnetic field, however, the paths of the electrons are twisted or if a single beam is employed, the electronic beam is twisted or coiled into a flat spiral form. Inasmuch as the beam forming and focusing electrodes impart a constant velocity to the electrons, the transit time o! the assignor to Pa., a corpoelectrons in traveling from the cathode to the anode or collector is very greatly increased since the path has been lengthened from a simple radius to a spiral, the number of convolutions of which may be made very great by selecting the magnetic field of suflicient strength.

If an intensity controlling grid or control electrode is provided with a signal or carrier voltage applied thereto, the signal will be received by the collector anode with a time delay determined by the transit time of the electrons.

Phase modulation of such a signal or carrier may be produced by varying the length of the electronic path, for example by varying the strength of the beam-twisting magnetic field.

The path of an electron or the shape of an electronic beam is made to take the form of a spiral. The spiral may either be a flat one in a single plane forming what is known as a pancake coil" or may take any other spiral form desired such as along the surface of a cone or along the surface of a cylinder, for example, in the latter case forming what is known as a helix or helical spiral.

The length of electron path and accordingly the transit time of the electrons may be varied by varying the length of the spiral regardless of the shape thereof. This may be done either by means of varyin the strength of a beam twisting magnetic field as already mentioned or also by other means such as by a device for distorting the electron beam path such as electrostatic deflection means, for example.

A better understanding of the invention will be ail'orded by the following detailed description considered in conjunction with the accompanying drawings, and its scope will be set forth in the claims.

In the drawing,

Fig. 1 is a schematic diagram of one embodiment of the invention representing an elevation with certain portions of the interior of the apparatus in section to leave other parts visible.

Fig. 2 is a view, looking from above, of a cross-section of the apparatus of Fig. l represented as cut by a plane 2-2 indicated in Fig. 1.

Fig. 3 is a view corresponding to Fig. 1 illustrating an embodiment of the invention in which electrostatic beam deflection is employed for modulation purposes, and

Fig. 4 is a schematic diagram of an embodiment of the invention in which the electronic beam takes a helical or corkscrew form.

Like reference characters are utilized throughout the drawing to designate like parts.

The apparatus forming an illustrative embodiment of the invention as illustrated in Figs. 1 and 2 comprises a relatively flat circular evacuated envelope assumed to be composed of glass for simplicity in the explanation and illustration, containing electron emitting means such as a cathode l2 in the form of a cylinder at the center of the envelope II, and a ringshaped anode or collector l3 which is substantially coaxial with the cathode l2. Suitable beam forming and focusing elements of conventional form may be provided for confining the electron emission to a path along a plane substantially intersecting the envelope perpendicular to its axis l4. Such electron directing and beam forming elements may take the form, for example, of a substantially tubular shield I5 surrounding the cathode l2 and having a radial opening It for projecting a beam of electrons ll which will tend to move radially except for the means hereinafter to be described.

For controlling the intensity of the electron beam, that is the number of electrons leaving the cathode |2 at a given time, a beam intensity control grid l8 may be provided which surrounds the cathode I2 if no individual beam is employed, or may merely be placed in front of the opening IS in the shield |5 if such an element is provided. If desired, a constant velocity grid I9 may also be provided, which is analogous to a focusing anode or lens member of a conventional cathode-ray oscilloscope tube.

For twisting the electron beam H, or for correspondingly twisting the paths of individual electrons issuing from the cathode |2, in case no beam forming element I5 is provided, a magnetizing member such as a permanent magnet or a pair of pancake coils 2| and 22 is provided, having a magnetic axis lying along or parallel to the axis I4 of the cathode I2 and the anode l3, the coils being on opposite sides of the tube.

For maintaining the shield I5 and the constant velocity grid l9 at suitable potentials, sources of unidirectional voltage such as batteries 23 and 24 may be provided, and a power supply source is provided for energizing the anode l3 which may take the form of an additional battery 25 connected in series with the lower voltagebatteries 23 and 24.

If the apparatus is to be employed for reproducing a grid signal in the anode circuit, a load resistor 26 may be connected in series with the anode |3 to the positive terminal of the power supply 25, and conductors 21 and 28 may be connected across the ends of the load resistor 26 for supplying a signal receiving device represented by a load 29.

For impressing a signal upon the control grid l8, a signal input source 3| represented by a rectangle may be provided, or if the apparatus is to be utilized for producing phase modulation of a carrier, a carrier source or exciter may represent the input source 3|.

If it is desired to provide adjustability of the delay inthe signal applied to the control,

tors 21 and 28, means are provided for varying H, the electrons are diverted from what would otherwise be a radial path from the cathode |2 to the anode l3 and are twisted into the spiral form shown in Fig. 2, the outer portion of the spiral being represented by the reference numeral IT. The pitch or tightness of the spiral depends upon the strength of the magnetic field H, and accordingly the point 33 at which the beam ll impinges upon the ring cathode or collector I3 is determined by the strength of the magnetic field H produced by the modulating voltage source 32.

For convenience, a single spiral beam H or the spiral path ll of a single electron has been shown. It is to be understood, however, that where a relatively large output is required it may be preferable to allow the electron emission to take place in all directions radially from the cathode parallel to the plane of the tube II, that is the plane of the top or bottom surface of the tube The same principle of operation will take place as before, however. Even though there may be innumerable spiral paths corresponding to the path each such path, will have a linear dimension or length, and consequently an electron transit time determined by the strength'of the magnetic field H. If

precision is employed in the construction of the tube and the electrodes, all of such paths should strike the ring anode l3 at substantially the same time, and accordingly a delayed signal appears at the anode l3 which is a counterpart of the signal applied to the intensity control and 22 up to a. point approaching the cut-oil of plate current, and this is accomplished with a minimum number of electrodes;

'In connection with Figs. 1 and 2, an arrangement has been described for producing modulation or for adjusting signal delay by varying the strength of the beam twisting magnetic field to vary the length of the beam or of the spiral electron path; however, the invention is not limited thereto. The effective length ,of the beam path may also be varied by distortion of the shape thereof. For example, the plane spiral ll of Figs. 1 and 2 may be distorted into conical form so as to lie along the surface of a cone of greater or less angle according to the strength of a modulating voltage in order to produce variable delay. An arrangement for accomplishing modulation in this manner is illustrated in Fig.

3. The corresponding elements of Figs. 1 and 3 have been designated by the same reference numerals, The coils 2| and 22 may be connected to a source of constant direct current 10 as shown or permanent magnets may be provided grid 3 as it reappears at the output conducconstant field H.

the strength of the beam-twisting magnetic elements 2| and 22. For example, the elements 2| and 22 may take the form of' pancake coils connected in series to modulating voltage source 32. As a result ofthe magnetic field H produced by the solenoid coils 2| and 22, in a direction normal to the path of the electron beamv in the arrangement In place of the annular or ring lector anode |3, a disc shaped anode collector l3 may be provided. For distorting the shape of the spiral path H of Figs. 1 and 2, washershaped deflecting electrodes 36 and 31 may be provided. The beam deflecting electrodes or deflection plates 36 and 31 are mounted near the of Fig. 3forproducingfa shaped col- 2 upper and lower ends of the cathode I2 and are directly connected or coupled to the modulating voltage source 32. In order to minimize defocusing efiect of the anode I3, a second complementary anode 38 may be provided having substantially the same shape and size as the anode l3 but located near the lower surface instead of the upper surface of the tube II, or vice versa, but preferably the anode 38 is maintained at a po tential higher than that of the collector anode 13' by suitable means such as by means of a supplementary voltage supply or battery 39 connected between the anode 38 and the positive 7 terminal of the power supply 25 of the anode l3. It will be understood, of course, that iiipreferred, both of the anodes l3 and 38 may be connected in the load circuits, that is in series with the re sistor 26 so that an input of either polarity from the modulating voltage vsource 32 will produce a phase modulation in the same direction in the output signal taken from the conductors 21 and 28.

In the arrangements of Figs. 1 and 3 in which the magnetic field H is caused to pass parallel to the axis (4 of the tube or envelope H, normal to the radii emanating from the cathode l2, the twisting of the electron paths into spirals gives rise to a circular component of electric current owing to the moving electrons, which in turn produces a magnetic field which acts parallel to the magnetic field H but in the opposite direction. However, the electric current efiect of the moving electrons is relatively small and is compensated by the use of a magnetic field H of adequate strength.

If desired, the beam forming shield l may be modified in construction and in the arrangement of its aperture IS in such a manner that electrons are allowed to issue only at a small point and would travel within a single plane, namely the horizontal center plane of the tube H were no modulating voltage applied to the deflecting plates 36 and 31. The presence of a small direct voltage between the plates 36 and 31 tends to warp the electron beam from a spiral path in such a horizontal plane so as to follow a path of a conical spiral as the result of which the end of the conical spiral beam ll strikes the anode I3 at a point 33'. A sufilcient voltage to warp the electron beam path into the shape represented by the conical spiral is provided by a deflecting circuit bias voltage source such as a battery 4 I.

If the deflecting voltag is increased as the result of a signal applied by the modulating voltage source 32, the conical spiral I1 is further distorted from a flat plane and follows the surface of a cone of sharper apex angle as represented by a conical spiral path 42 impinging upon the cathode l3 at a point 43. Inasmuch as the radial pitch of the electron beam is relatively unchanged by the variaton in modulating voltage, the path of the beam is made shorter as the result of the decreased radius, since the point 43 is closer to the center of the tube and the cathode |2 than the point 33'. Thus, in the arrangement of Fig. 3, variation in transit time effect is accomplished by varying the radius of the splral beam to vary the length thereof as the result of the warping of the beam into a cone of sharper apex angle.

In the arrangements thus far described, the electrons would travel in radial paths unless twisted into spiral paths by the transverse magnetic field. However, the invention is not limited thereto, and includes arrangements in which the electrons are twisted from some other normal rectly heated cathode 46, a conventional intensity control grid 41 adapted to be coupled to a signal input source represented by terminals 3| and a screen grid or focusing electrode 48 held at a suitable positive potential by means of a voltage source represented as a battery 49.

At the opposite end of the tube 44, there is a conventional collector anode 5| lying in a plane substantially perpendicular to the axis of the tube 44 and connected to an anode voltage source represented as a battery 52 with a load resistor 26 connected in series with the voltage supply 52.

Where modulation or adjustment of signal dela is to be accomplished electrostatically, the magnet 45 may take the form of a tubular permanent magnet composed of suitable high coercive force magnetic material such as aluminum, nickel, cobalt alloy, for example, or it may take the form of a solenoid or coil of current-conducting wire connected to a source of constant direct current represented by a battery 53. When the magnet 45 is used in this manner, it serves to lengthen the path of the electrons or to increase the transit time of the electron beam 55 between the cathode 4'6 and the collector anode 5|. 'lhe electron gun, comprising elements 46, 41 and 48, is preferably :0 arranged as to produce electron beam deviating slightly from the axis of the tube 44 and the magnetic axis of the magnet 45 or the electron gun is arranged to produce a divergent cone of electron rays in order that the electron streams will have a component normal to the magnetic axis of the magnet 45, whereby twisting action may be produced.

Where the modulation is to be accomplished magnetically, the source of magnetizing current 53 is made variable in response to modulation or a separate source is connected across a current limiting resistor 56 in series with the constant current source 53 and the solenoid coil 45. Terminals 32' for connection to a modulating voltage source such as the source 32 in Figs. 1 and 3 or some other source of a delay control voltage, may be connected directly to the solenoid coil 45 or may be connected through an impedance-matching transformer 51.

The tightness of the spiral beam 55, that is the pitch and radius, are varied by varying the strength of the magnetic field produced by the solenoid 45 in response to variations in the input signal through the terminals 32. A resultant variation in transit time of the electrons varies the delay in the signal appearing across the load resistor 26 serving as a counter-part of the signal supplied at the intensity control grid 41 through the signal input terminals 3|.

Ii electrostatic delay control or phase control is desired instead of magnetic, a pair of velocity control electrodes 58 and 59 may be provided which are preferably relatively close to the electron gun and to the anode 5 1' respectively in order to exert the maximum control over electron ve- 76 locity. In this case the impedance matching transformer 51 is connected to the electrodes 58 and 58 instead of to the solenoid coil 45, and a constant current is supplied to the coil 45 for producing a relatively long helical-electron beam path 55. To represent the change over from one form of modulation to the other, a double-throw, double-pole switch 6| has been shown having a pair of blades 62 connected to the impedance matching transformer 51, having one pair of stationary contacts 63 connected across the resistor 56 and having two other stationary contacts 64 and 65 connected to the velocity control electrodes 58 and 59 respectively. When the switch blades 62 are moved from the position illustrated to a right hand position making connection with the stationary contacts 64 and 65, modulating or delay-controlling voltages 180 degrees apart are applied to the electrodes 58 and 59, but preferably a bias source 66 is provided for preventing the electrodes 58 and 59 from drawing current. When the electrodes 58 and 59 are to be utilized, the bias source 66 is connected to a tap 61 of a secondary winding of the transformer 51 by closing a switch 68.

It will be understood that the coils 2l--22 in Fig. l and the magnetic beam twisting coil 45 in Fig. 4 may be so shaped as to produce any desired variation in magnetic field strength along the ordinary electron path which would exist if the magnetic coils were not present. For example in the case of the coil 45 of Fig. 4, the ends of the coil may be tapered as at 45a so as to cause the magnetic field strength to increase gradually as the beam 55 enters the magnetic field and to,

cause the magnetic field strength to recede gradually again as the beam leaves the field of the coil 45 in order to cause the beam 55 to enter and leave the helical spiral form gradually.

Preferably suitable means are provided for refocusing and straightening the spiral electron beam 55 before it reaches the cathode 5|. For example, a refocusing electrode 69 may be provided held at a suitable potential by a battery H. With the change over switch 6| thrown to the right hand position making contact with the contacts 64 and 65, the modulating voltage source 32 is in effect connected in push-pull unbalanced relation to the velocity control electrodes 58 and 59. The permanent magnet or the constant current solenoid magnet 45 serves to supply a constant twist to the electron beam 55 for a given electron velocity, and the transit time is then varied by the variation in potential of the electrodes 58 and 59. The variation in velocity also has some efiect on the twist of tightness of the helical-electron path, and accordingly variation in signal delay or phase modulation of the signal applied at the terminal 3| is produced by variation in voltage applied at the terminal 32.

Certain embodiments of the invention and certain methods of operation embraced therein have been shown and particularly described for the purpose of explaining the principle of operation of the invention and showing its application, but it will be obvious to those skilled in the art that many modifications and variations are possible, and it is intended, therefore, to cover all such modifications and variations as fall within the scope of the invention which is defined in the appended claims.

Iclaim:

1. An electron discharge device comprising in combination an emitter for projecting electrons radially with respect to an axis, an intensity control electrode in front of the emitter, a constant velocity electrode in front of the intensity control electrode, a pair of beam deflecting electrodes coaxial with respect to said emitter in the form of washers mounted at the ends of the emitter in planes transverse to said axis, and a collector transverse to said axis.

2. An electron discharge device having an axially located emitter for projecting electrons radially with respect to the axis of said device, a collector anode lying in a plane substantially normal to said axis and near one end of said emitter, means for setting up a magnetic field within said device in a direction parallel to said axis, whereby said electrons are caused to traverse a spiral path lying along the surface of a cone so as to impinge upon said collector anode. and an intensity control electrode coaxially disposed with respect to said emitter and adapted to vary the emission intensity of said emitter in accordance with a signal applied to said control electrode.

3. An electron discharge device having an axialli located emitter for projecting electrons radially with respect to the axis of said device, a collector anode lying in a plane substantially normal to said axis and near one end of said emitter, means for setting up a magnetic field within said device in a direction parallel to said axis, whereby said electrons are caused to traverse a spiral path lying along the surface of a cone so as to impinge upon said collector anode, and a pair of deflection plates disposed parallel to said collector anode and lying on either side of the normal path of projected electrons.

4:. A cylindrical electron discharge device having a longitudinal axis, an emitter of radiall projected electrons located in substantial coincidence with said axisja collector anode concentric with said axis and extending radially outward therefrom near one end of said emitter, a pair of defiection plates of substantially washer form also extending radially outward from said axis, said plates being disposed respectively near the ends of said emitter.

5. A device according to claim 4, further comprising a cylindrical electron-permeable control electrode disposed in coaxial relation with said emitter and adapted to vary the flow of electrons between said emitter and said collector anode.

6. An electron discharge device of generally cylindrical configuration having a longitudinal axis and comprising: an emitter of radially projected electrons, said emitter being located in substantial coincidence with said axis; a collector anode concentric with said emitter and extending in a plane normal to said emitter and near one end thereof; means for maintaining said collector anode at a positive potential with respect to said emitter, thereby causing electrons projected from said emitter to flow toward and impinge upon said collector anode; means for producing a magnetic field of predetermined flux density in a direction parallel to said axis, whereby said electrons are caused to traverse a spiral path between said emitter and said collector anode; and a pair of deflection plates disposed parallel to said collector anode and lying on either side of the normal path of projected electrons.

JOHN W. TILEY.

(References on following page) 9 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Thomas July 19, 1927 Hull Sept. 4, 1928 Steenbeck Dec. 28, 1937 Mendenhall Jan. 18, 1938 Skellett Apr. 12, 1938 Han-sell Nov. 29, 1938 Dallenbach June 27, 1939 Llewellyn June 27, 1939 Number Number

Images