US2390250A - Cathode ray tube and circuit - Google Patents

Description

Dec, 4, 1945. c, w. HANSELL CATHODE RAY TUBE AND CIRCUIT Filed Nov. 3, 1942 2 Sheets- Sheet 1 ,3 OUTPUT M m H a iTlT A. C. INPUT l l l l i 25 BEAM INVENTOR. CLARENCE 14 HANSELL ATTORNEY.

Dec. 4, 1945. -c. w. HANSELL CATHODE RAY TUBE AND CIRCUIT Filed Nov. 5, 1942 2 Sheets-Sheet 2 K T 21 111m u.

INVENTOR C LflkF/VCE m f/fl/VJEZL BY '/g ATTORNEY Patented Dec. 4, 1945 UNITED STATES PATENT QFFTCE CATHODE RAY TUBE AND CIRCUIT Clarence W. Hansell, Port Jefi'erson, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application November 3, 1942, Serial No. 464,325

6 Claims. (Cl. 250151) a deflecting plate electrode 3, a pair of rod-like electrodes 4, 4 symmetrically positioned on opposite sides of the axis of the tube, a metallic cylinder 5 surrounding the rod electrodes 4, 4, a pair of electron collectors or anodes 6, 6 and an axially electrodes under the influence of a deflecting 5 positioned shield or screen plate electrode 1 for electric field. The present invention is a conshielding the anodes from each other. tinuation-in-part of my copending application The cathode ray tube is illustrated as being Serial No. 324,053, filed March 15, 1940, now used for the amplification of alternating cur- United States Patent 2,305,617, granted December rents, and has connected to it a suitable input 22, 1942. circuit 8 extending to a source of signal waves An object of the present invention is to provide to be amplified, not shown, and coupled via a an electronic amplifier of alternating currents parallel tuned circuit 9 to the deflecting plate which is extremely sensitive and has a large ratio electrode 3. The rod-like electrodes 4, 4 are each of controlled current and power to control curmaintained at a relatively high positive potential rent and power. with respect to the cathode over individual paths Another object is to provide means for conwhich include leads [5, I5, resistors l0, l0 and tinuously increasing the angular deflection of an opposite sides of a potentiometer II to an interelectron beam during the interval of travel from mediate point of which is connected a lead l2 the cathode to the electron collecting electrode. extending to the positive terminal of a source A further object of the present invention is to of unidirectional potential 25. The anodes 6, 6 provide an electric field for a cathode ray tube are connected to the opposite terminals of poof such configuration that it continuously acts tentiometer ll over individually tunable output on the electron beam over the major part of its circuits [3, l3, the latter being coupled by means path of travel to increase the initial deflettion, of transformer M to a suitable common utilizaand is only effective after the beam has been tion circuit, not shown. The shield 1, cylinder pulled off center. 5 and" deflecting electrode 3 are maintained at A still further object is to provide a high fresubstantially the same positive potential relative quency amplifier of the electron beam type which to the cathode although at a less positiv potenhas' a greater sensitivity and greater control of 0 tial than the rods 4,.4 and anodes 6, 6. the current and power in the tube than conven- The electric field distribution between the rods tional beam type tubes now in use. 4, 4 and. cylinder 5 is shown in Fig. 2 which illus- These objects and others will be more readily trates a cross-section of the vacuum tube of Fig. 1 understood from a reading of the following dealong the dash lines 22. In Fig. 2, the electron scription which is accompanied by drawings, beam which normally passes along the axis of wherein: the tube in the absence of deflecting potentials, Figs. 1, 4 and 6 illustrate dilferent embodiments is shown by th dotted circular lines in the center of cathode ray tubes embodying the principles of the cylinder. It should be noted that the elecofthe invention; tric field is substantially zero along the axis of Figs. 2 and 5 ar fragmentary cross-section 40 the cylinder but increases rapidly between the views of Figs. 1 and 4, respectively, showing the axis and the rods 4, '4. Electrons traveling positioning of the most important electrodes of through the cylinder which are not on the axis the tubes and the electric field distribution therewill therefore be deflected by the electric field etwee toward one or the other of the rod-like elec- Fig. 3 illustrates a cross-section of a modifica- 4 trodes 4, 4. It Will be evident that when the election of the tube of Fig. 1; and tron beam travels down the axis of the cylinder Fig. 7 is a fragmentary cross-section of a tube 5, its center line will be substantially unaffected showing electron paths and is given to aid in by theelect'ric field within the cylinder. Howan understanding of the operation of Fig. 6. ever, if the beam is deflected off the axis toward Throughout the figures, the same or equivalent one or the other of the rod-like electrodes 4, 4, parts are represented by the same reference the beam will be-acted on by the electric field to numerals. increase the deflection. Putting it another way, Referring to Fig. l in more detail, there is the initial deflection of an electron toward one shown a cathode ray tube having within an evacrod 4 will cause a greater movement toward said uated envelope i electron emitting cathode 2, one rod by virtue of the positivepotential on this rod. The oppositely located rod 4 will not have an exact counter attraction on this electron because of the field distribution shown in Fig. 2. As soon as th electron is pulled or drawn off the axis or center toward one rod electrode 4, the force on this electron increases in a direction toward the said one rod.

In the operation of the device and circuit of Fig. 1, the input energy on line 8 which is to be amplified, is impressed on tuned circuit 9 and causes deflecting electrode 3 to move the electron beam up or down toward one of the rod-like electrodes 4. The initial deflection of the beam produced by the electrode 3 will then be increased by the action of the electric field in the manner described above, and the greatly increased deficted beam will impinge predominantly on that one of the anodes 6 which is nearest the rod 4 toward which the beam is moving. The electrodes 4, 4 are, of course, of such length and the potentials applied are of such value that the electrons do not impinge on these electrodes but pass over the ends to be collected by anodes 6, 6. At extremely high frequencies there may be'several waveswithin the cylinder 5' at any instant of time. These waves start with small amplitudes near the control electrode 3 and then grow to be much larger waves before the output end of the cylinder is reached.

As an illustration of the increase in deflection of the beam obtainable b the tube of the invention, given by way of example only for purposes of exposition and not by way of limitation, if the control electrode potential on 3 can produce 0.01 centimeter initial deflection then the electric field traversed by the beam might increase this deflection to say 0.1 centimeter or more. Therefore, the corresponding gain in amplification maybe, say to 1 in current or 100 to 1 in power, or more. This increase in amplification is effective substantially independently of the frequency of the currents to be amplified.

The separate connections l5, l5 to the rod-like electrodes and the potentiometer arrangement H enables the direct current or low frequency potentials derived from the anodes 6, 6 to control the average or direct current potentials on the rods 4, 4 in a direction to keep the mean position of the center of the electron beam properly centered. As an illustration, assuming that one anode 6 .tends to take more direct current than the other anode, then there-will be a greater current flow and IR drop in one-half of the potentiometer H and a corresponding lowering of the positive potential applied to that rod 4 directly associated with the anode drawing the greater direct current. The frequency response of this beam centering arrangement is such that it does not affect deflections of the beam at the operating frequency but only prevents deflections at lower frequencies and steady state. deflections.

If desired, the cylinder 5 may be flattened to take the approximate form of an ellipse in the manner shown in Fig. 3, without departing from the principles of the invention. It will be noted thatthe field distribution of Fig. 3 is substantially the same as that of Fig. 2.

As; a practical matter, the cylinder of Fig. 1 and the ellipse of- Fig. 3 can be dispensed with and two flat plates I8, l8 substituted therefor. Qne such arrangement, given by way of example, i s wn in Fig. 4. The field distribution between rod-like electrodes 4, 4 and the plates is shown in Fig. 5 which represents a cross-section of the tube of Fig. 4 along the line 55. I I Will trodes of the other figures.

be evident that the field distributions of Figs. 2, 3 and 5 are substantially similar and will cause similar effects on the electron beam. In Fig. 4, there is shown a tubular accelerating electrode l6 which has integral therewith a circular shield H for removing stray electrons. The electrode I6 and plates I8, I8 have suitable positive polarizing potentials applied thereto over leads 2| and 22 which potentials may be of substantially the same value although lower than the positive potential applied to rods 4, 4 and anodes 6', 6'. The anodes 6, 6 are shown as being hollow or cupshaped to minimize the efiects of secondary emission and to insure that secondary electrons do not extend beyond the confines of the anode structure. Of course, any other type of anode structure, such as a plate, can be used instead. The shield 'l' is somewhat different in form from shield 1 of Fig. 1. Shield '7' is maintained at a positive potential relative to the cathode, and is composed of a central plate part M for enabling axially traveling electrons to impinge thereon, and upper and lower apertures 20 for enabling the deflected electrons to pass-through the shield and to impinge on the anodes. The operation of the system of Fig. 4 insofar as theipresent-invem tion is concerned is substantially identical with that of Fig, l.

Although rod-like electrodes 4, 4 of Figs l'to 5 have been shown as beingparallel to each other and perfectly straight, they can be arranged at a diverging angle and,if desired, curved slightly outward from the axis of the device to correspond to the shape of the path of the beam.

Fig. 6 shows a cathode ray tube in accordance with another embodiment of the invention, which functionsby means of a magnetic field, instead of the electrostatic fields of Figs. 1 to 4. In Fig. 6,. there is provided a field coil 23 which replaces the cylinder,.plates and rod-like elec- Coil 23 is energized by a source of unidirectional potential 24 and provides a desired non-uniform spreading or fan-shaped cross-section of the magnetic field throughout the space traversed .by the, beam, roughly in the manner indicated byrthe light solid lines labeled A. The magnetic field intensity is greatest at or near the origin of the beam.

In the arrangement of Rig. '6, electrons from an indirectly heated cathode 2 are drawn' to a more positively charged screen H. A portion'of the electrons, passing through a. hole in the screen l7, provide an electron beam which in the absence of disturbing (i. e., deflecting) forces, travels in a straight line B to impinge upon the approximate center of screen electrode 1. In following this undisturbed path, electrons travel parallel to the magnetic field along" the path and the presence of the field tends to prevent elec-'- trons straying from this path in accordance with the well recognized phenomenon of magnetic field focussing or restriction of the path of electron beams in cathode ray tubes. pposenow that; a high frequency potential is applied to an electrode 3, position-ed beside the electron beam, near its source. As a result of the alternating current potential, electrons are given components of velocity, and energy, in directions at right angles to the undisturbed direction of flow of electrons. Asa result of these components of velocity,the electrons no longer follow a nearly central straight path but acquire a spiral motion due to moving out away from the central path and then being returned to. the central path again by the influence of the magnetic field. The spiral paths of the deflected electrons are represented by dash-lines labeled C.

Suppose that, for magnetic field values of the strength existing in the region of electrode 3, the electrons, as viewed endwise to the original undisturbed beam path follow a'path in circles of diameter as shown at I in Fig. 7. If the magnetic field were uniform, the path of electrons, as viewed thus, would remain in circles as the electrons moved all the way to the screen 1'. However, if the magnetic field strength decreases between screens H and I, as illustrated in Fig. 6, then the diameter of the circles formed by projection of the path will increase as the electrons move into the weaker magnetic field. This 7, is in accordance withwelLknown physical phe-.

nomena in which electrons moving at uniform velocity and energy, at right angles to a magnetic field, move in circles whose diameters are inversely proportional to the intensity of the magnetic field.

By giving electrons components of velocity both parallel to and at right angles to a magnetic field, we force them to follow a spiral path in which the diameter of the spiral is inversely proportional to the intensity of the magnetic field.

In the arrangement of Fig. 6, rather small diameter spiral motions, given to the electron paths by the alternating current potential on electrode 3, in the most intense part of the magnetic field, grow to large diameter spiral motions as the electrons move toward screen electrode 1', into a weaker magnetic field. Thus, a relatively small amplitude, of electron stream wave motion at one end of the electron stream path will grow to a large amplitude of wave motion at the other end of the path.

This growing wave motion may be utilized to control and increase the control of the distribution of electron current between screen electrode 1' and anodes 6', 6'. In the circuit arrangement shown. currents flow alternately to one or the other of electrodes 6' at a frequency corresponding to the frequency of the input potential applied to electrode 3. Thus, the arrangement functions as a relatively high gain beam deflection type amplifier.

The arrangement of Fig. 6 may be used as a frequency doubler. by connecting a tuned output circuit between screen electrode 1 and paralleled anodes B, 6'. It may also be used as a detector by connecting a suitable frequency selective detector output circuit between screen electrode 7' and paralleled anodes 6', G. In fact, all of the functions possible with other electron beam deflection vacuum tubes may be performed with the improved tube of the invention.

I prefer to call the circuit of my invention a growing wave amplifier because the control potentials on electrode 3 cause the electron stream to deflect in such a way as to produce a wave in the stream which travels along the length of the tube with a velocity equal to the velocity of electrons in the stream. This wave starts with small amplitude near the deflecting electrode and grows to be a very much larger wave before the output end of the tube is reached.

There is a crude analogy between the efiect of the electric field in the cylinder increasing the wave amplitude and an effect which might be produced with surface waves on water. If we passed a strong current of air parallel to the surface of water in a long trough, this air would give little if any energy to the water so long as the water surface was perfectly smooth. However, if we deliberately produced small Waves in the water at the end of the trough from which the air comes, the presence of the waves would provide a coupling between water and air which would cause the waves to grow in amplitude as they traveled down the trough. In this water wave case We have another example of means to cause waves deliberately produced to grow in strength with passage of time and distance but, at all times, the waves are controllable by the input wave power.

It should be understood that the invention is not limited to the precise arrangements of parts shown and described since various modifications may be made without departing from the spirit and scope of the invention. For example, the cylinder 5 of Fig.1 or the ellipse of Fig. 3 can be dispensed with and at least a large part of the envelope made of metal, or the inner surface of the glass envelope can be coated with metal to simulate the metallic cylinder or ellipse.

What is claimed is:

1. The method of influencing a stream of electrically charged particles which comprises surrounding the stream over substantially its entire path of travel with a magnetic field the axis or center of which is parallel to the direction of principal motion of the stream, but which field is more intense at and near the beginning of the path of travel of the stream than at other portions of said path, and deflecting said stream near the beginning of its travel, whereby said field produces a constantly increased deflection as the stream progresses from its point of initial deflection.

2. The method of influencing a stream of electrically charged particles which comprises surrounding the stream of the major portion of its travel with a magnetic field, the axis or center of which is parallel to the direction of principal motion of the stream but which becomes progressively weaker as the stream moves further away from its origin, and deflecting said stream near its origin, whereby said field produces a constantly increased deflection as the stream moves further away from its point of initial deflection.

3. In an electrical discharge device having a cathode for producing an electron beam along the axis of said device, a pair of anodes symmetrically arranged on opposite sides of said axis, a deflecting electrode adjacent said beam and located between said cathode and said anodes, and means for producing a magnetic field whose axis is parallel to the direction of principal motion of said beam and is effective over the major portion of the travel of the beam but which becomes progressively weaker as the beam moves further away from said deflecting electrode.

4. In an electrical discharge device having a cathode for producing an electron beam along the axis of said device, a pair of anodes symmertically arranged on opposite sides of said axis, a deflecting electrode adjacent said beam and lo cated between said cathode and said anode, a magnetic field coil surrounding said beam and being effective over substantially the entire path of travel of said beam on both sides of said deflecting electrode, and a source of direct current energizing said coil, said coil being so arranged that the axis ,or center of its field is parallel to the direction of principal motion of said beam. 5. In an electrical discharge device having a cathode at one end thereof for producing an electron beam along the axis of said device, and an anode near the other end of said device, said anode being located to one side of said axis, a deflecting electrode adjacent said beam and located between said cathode and said anode, and means for producing a magnetic field having an axis or center which is parallel to the direction of principal motion of said beam and is effective over substantially the entire distance between said cathode and anode but which becomes progressively weaker as the beam moves further away from said deflecting electrode.

6. In an electrical discharge device having an indirectly heated cathode at one end thereof for producing an electron beam, a pair of anodes at the'other end of saiddevice symmetrically arranged on opposite sides of the ;longitudinal axis of said discharge device, a positively charged screen having an aperture registering with said axis located adjacent said cathode, a deflectin electrode located adjacent said screen 'on the side thereof opposite the cathode and also-being adjacent said beam, another screen electrode 1ocated adjacent said anodes and positioned between said anodes and said cathode, said. last screen having electron permeable surfaces radjacent both of said anodes, and means for producing a magnetic field havingan axis or center which is parallel to the direction of principal motion of said beam and is effective over the entire distance between said cathodeandlsaid anodes but which is relatively-strong. near said first screen and relatively weakvnear said other screen. I I.

, CLARENCE W.

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