US2305617A - Cathode ray tube and circuit - Google Patents

Description

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GATHODE RAY TUBE AND CIRCUIT Filed March 15, 19.40 2 Sheets-Sheet 1 (WIMP .4. 0. INPUT l3 aurpur ELECTRON BEAM INVENTOR. CLARENCE w HA NSELL ATTORNEY.

Wm. 22, 1942. c. w. HANSELL 2,305,617

CATHODE RAY TUBE AND CIRCUIT Filed March 15, 1940 2 Sheets-Sheet 2 MW W INVENTOR.

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Patent 1942 ctrr Clarence Hall, Port .iefl'erson, N. Y assignor to Radio Corporation of America. a corporation of Delaware Application in,

. l5 Elaims.

This invention relates to improvements in cathode ray type electron discharge devices and circuits therefor, and particularly concerns a cathode ray device wherein an electron stream is shifted between a pair of electron collecting elecgrtfies under the influence of a deflecting electric An object of the present invention is to provide an electronic amplifierol alternating currents which is extremely sensitive and has a large ratio of controlled current and power to control current and power.

Another object is to provide means for continuously increasing the angular deflection of an electron beam during the interval of travel from the cathode to the electron collecting electrode.

A further object of the present invention is to provide an electric field for a cathode ray tube oil such configuration that it continuously acts on the electron beam over the major part of its'path of travel to increase the initial deflection, and is only effective after thebeam has been pulled ofi center.

A still further object is to provide a high frequency amplifier of the electron beam type which has a greater sensitivity and greater control of the current and power in the tube than conventional beam type tubes now in use.

These objects and others will be more readily understood from a reading of the following description which is accompanied by drawings, wherein:

Figs. 1, ii and 6 illustrate different embodiments oi cathode ray tubes embodying the principles of the invention;

Figs. 2 and 5 are 'iragrnentary cross section views of Figs. 1 and i, respectively, showing the positioning of the most important electrodes oi the tubes and the electric field distribution thereioetween; and

Fig. 3 illustrates a cross-section of a modification of the tube oi Fig. 1.

Throughout the figures the same or equivalent parts are represented by the same reference nuinerals.

Referring to Fig. l in more detail, there is shown a cathode ray tube having within an evacuated envelope i an electron emitting cathode i, a deflecting plate electrode 3, a pair of rod-like electrodes i, i symmetrically positioned on opposite sides of the axis oi the tube, a metallic cylinder 5 surrounding the rod electrodes t, t, a pair of electron collectors or anodes t, t. and an axially positioned shield or screen plate ch is, 1940. Serial No. 824.0%

(or. sac-2r) 1 of unidirectional potential it.

electrode i for shielding the anodes from each other.

The cathode ray tube is illustrated as being used for the amplification of alternating currents, and has connected to it a suitable input circuit 8 extending to a source of signal waves to be amplified, not shown, and coupled via a parallel tuned circuit 9 to, the deflecting plate electrode 8. The rod-like electrodes i, d are each maintained at a relatively high positive potential with respect to'the cathode over individual paths which include leads it, it, resistors ill, ill and opposite'sides of a potentiometer ii to an intermediate point of which'is connected 2. lead i2 extending to the positive terminal of a source The anodes t, t are connected to the opposite terminals of potentiometer it over individually tunable output circuits ii, ii, the latter being coupled by means of transformer i l to a suitable common utilization circuit, not shown. The shield i, cylinder i and deflecting electrode i are maintained at substantially the same positive potential relative to the cathode although at a less positive potential than the rods t, i and anodes it, t.

The electric field distribution between the rods ii, i and cylinder t is shown in Fig. 2 which illustrates a cross-section of the vacuum tube of Fig. 1 along the dash lines 22. In Fig. 2, the electron beam which normally passes along the axis of the tube in the absence of deflecting potentials, is shown by the dotted circular lines in the center of the cylinder. It should be noted that the electric field is substantially zero along the axis of the cylinder but increases rapidly between the axis and the rods i, i. Electrons traveling through the cylinder which are not on the axis will therefore be deflected by the electric'flelcl toward one or the other of the rod-like electrodes ii, ii. It will be evident that when the electron beam travels down the axis or the cylinder i, its center line will be substantially unafiected by the electric field within the cylinder. However, if the the beam is deflected ofl the axis toward one or the other of the rod-like electrodes t; t, the beam will be acted on by the electric fleld to increase the deflection. Putting it another way. the initial deflection of an electron toward one rod i will cause a greater movement toward said one rod by virtue of the positive potential on this rod. The oppositely located rod i will not have an exact counter attraction on this electron because of the field distribution shown in Fig. 2. As soon as the electron is pulled or drawn ofl the axis or center toward one rod electrode i, 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 t, 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 rodlilre electrodes l. 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 deflected beam will impinge predominantly on that one of the anodes t which is nearest the rod l toward which the beam is moving. The electrodes t, d 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 ii, t. At extremely high frequencies there may be several waves within the cylinder at any instant of time. These waves start with small amplitudes near the control electrode t 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 by 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 may he, 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 i5, It to the rod-like electrodes-and the potentiometer arrangement ii enables the direct current or low frequency potentials derived from the anodes 6, ii, to control the average or direct current potentials on the rods d, d in a direction to keep the mean position of the center of the electron beam properly centered. As an illustration, assuming that one anode ii 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 ii and a corresponding lowering of the 'positive potential applied to that rod ii 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 defiections.

If desired, the cylinder 5 maybe 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 that the 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, i8 substituted therefor. One such arrangement, given by way of example, is shown in Fig. 4. The field distribution between rod-like electrodes l, i and the plates is shown in Fig. 5 which represents a cross-section of the tube of Fig. 4 along the line 55. It will 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 it which has integral therewith a circular shield I? for removing stray electrons. The electrode Ill and plates Iii, iii 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 l, ii and anodes 6', t. The anodes 6, t are shown as being hollow or cupshaped to minimize the effects 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 'i' is somewhat different in form from shield i of Fig. 1. Shield 1' is maintained at a positive potential relative to the cathode, and is composed of a central plate part IQ for enabling axially travelling 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 the present invention is concerned is substantially identical with that of Fig. 1.

Although rod-like electrodes ti, l of Figs. 1 to ii have been shown as being parallel 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 functions by means of a magnetic field, instead of the electrostatic fields of Figs. 1 to i. In Fig. 6 there is provided a field coil 23 which replaces the cylinder, plates and rod-like electrodes of the other figures. Coil til is energized by a source of unidirectional potential it and provides a desired non-uniform fan-shaped magnetic field throughout the space traversed by the beam in the manner indicated by the dash lines, the intensity of which increases toward the point of origin of the beam. It will be observed from an inspection of Fig. 6 that the direction of the field changes according to the distance from the axis. The field coil 23 provides the same result as the electrostatic field of Figs. 1 to 5.

I prefer to call the circuit of my invention a "growing wave amplifier because the control potentials on electrode it 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 effect 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 travelled 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 modiflcations may be made without departing from the spirit and scope of the invention. For example, the cylinder 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 oi the glass envelope can be coated with metal to simulate the metallic cylinder or ellipse.

What is claimed is:

l. The method of influencing a stream of electrostatically charged particles which comprises surrounding the stream over the greater portion of its travel with an electric field whose transverse value is substantially zero along the normal axis of the stream and whose intensity .increases in at least one direction with distance from said axis, whereby an initial deflection of said stream in said one direction will produce an increase of deflection in the same direction as the electrons travel through said field.

2. In an electrical discharge device having means for producing a stream of charged particles alon the axis of said device and means responsive to deflection of the stream in a particular plane, means for producing a transverse electric field around said stream over the greater portion of travel of said stream and whose value is substantially zero along the said axis and which increases rapidly with distance from said axis along said plane, and means adjacent said stream near the beginning of its travel and responsive to alternating currents for deflecting said stream in said plane, whereby a deflection of said stream caused by said last means will increase in size as said stream passes through said field.

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 also located between said cathode and said anodes for producing a substantially transverse electric fieldwhose value is substantially zero along said axis and which increases rapidly in a predetermined plane at right angles to said axis, said means including a pair of rod-like elec-. trodes symmetrically positioned in said plane on opposite sides of said axis, and connections for maintaining said rod-like electrodes at positive potentials relative to said cathode, said deflecting electrode functioning to deflect said beam in said plane toward one or the other of said rod-like electrodes.

4. 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,

arranged with respect to the axis of said device,

connections from said rod-like electrodes and said tubular surface to sources of unidirectional potential for maintaining said elements at suitable polarizing potentlals, said deflecting electrode functioning to deflect said beam in said plane toward one or the other of said rod-like electrodes. I l a 5. Apparatus in accordance with claim 4, characterized in this that said hollow tubular surface is a cylinder.

6. Apparatus in accordance with claim 4, characterized in this that said hollow tubular surface has the form of an ellipse with its flat sides parallel to said predetermined plane.

7. 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 also located between said cathode and said anodes for producing an electrostatic field whose value is substantially zero along said axis and which increases rapidly in a predetermined plane at right angles to said axis, said means including a. pair of rod-like electrodes symmetrically positioned in said plane on opposite sides of said axis, and parallel plate electrodes also symmetrically position on opposite sides of said axis but in planes parallel to the plane containing said rod-like electrodes, said plate electrodes being substantially coextensive in length with said rod-like electrodes. and con nections from said rod-like electrodes and said plate electrodes to sources of unidirectional potential for maintaining said electrodes at suitable polarizing potentials.

8. 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 also located between said cathode and said anodes for producing an electrostatic field whose value is substantially zero along said axis and which increases rapidly in a predetermined plane at right angles to said axis, said means including a pair of rod-like electrodes symmetrically positioned in said plane on opposite sides of said axis, one of said rod-like electrodes being on the same side of said axis as one anode while the other rod-like electrode is on the same side of said axis as the other anode, a potentiometer having opposite terminals connected to said anodes and an intermediate point on said potentiometer connected to the positive terminal of a source of unidirectional potential, a connection from a negative terminal of said source to said cathode, and a connection from each of said rodlike electrodes to that terminal on said potentiometer to which the correspondingly located anode is connected, whereby the unidirectional potentials on said anodes automatically control the average direct current potential on said rodlike electrodes for maintaining the normal direction of said beam along said axis in the absence of deflecting potentials.

9.-Apparatus in accordance with claim 8, including a shielding plate positioned between said anodes and in the plane of said axis.

10. The method of influencing a stream of electrically charged particles which comprises surrounding the stream over the major part of its travel with an electric field which is constant 11. 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 located between said deflecting electrode and said anodes for producing a substantially transverse electric field whose value is substantially zero along said axis and which increases rapidly in a predetermined plane at right angles to said axis, saidmeans including a pair of rod-like electrodes symmetrically positioned in said plane on opposite sides of said axis, and connections for maintaining said rod-like electrodes at positive potentials relative to said cathode, said deflecting electrode functioning to deflect said beam in said plane toward one or the other of said rod-like electrodes.

12. In an electrical discharge device, means for producing a beam of electrons substantially along a line through the center of said device, and mean including a pair of electrically-conducting surfaces on opposite sides of said beam and maintained at a predetermined unidirectional potential for producing an electric fleld around said beam for a substantial portion of the path of travel of said beam and which fleld has the following characteristics: (a) is substantially zero along the axis of said beam; (b) is effective only after the beam has been deflected from said axis; and (c) has a component in one direction transverse to the axis which increases with distance from said axis, and an electron deflecting element positioned near the beginning of the path of travel of said beam through said electric field, whereby the electric fleld continuously act to increase the initial deflection of said beam.

13. In an electrical discharge device, means including a cathode for producing a beam of electrons substantially along a line through the center of said device, and means near said cathode for deflecting said beam, and means for enhancing the deflection caused by said deflecting asoaeir means, said deflection enhancing means, including a pair of surfaces on opposite sides of said beam and maintained at a predetermined unidirecticnal potential, producing an electric field around said beam for a substantial portion of the path of travel of said beam and which flld has the following characteristics: (a) is substantially zero along the axis of said beam; (11) is edective only after the beam has been deflected from said axis; and (c) has a. component in one direction transverse to the axis which increases with distance from said axis.

14. In an electrical discharge device having means for producing a beam of electrons, a pair of anodes symmetrically positioned on opposite sides of the normal path of travel of said beam when said beam is undeflected, means for shielding said anodes from one another, a deflecting element adjacent said beam and located between said cathode and said anodes, and means located between said deflecting element and said anodes for producing a substantially transverse electric fleld whose value is substantially zero along said axis and which increases rapidly in a predetermined plane at right angles to said axis, said means including a pair of rod-like electrodes symmetrically positioned in said plane on opposite sides of said axis, and connections for maintaining said rod-like electrodes at positive potentials relative to said cathode, said deflecting element functioning to deflect said beam in said plane toward one or the other of said rod-like electrodes.

15. In a cathode ray device, means including a cathode for producing a beam of electrons, means for deflecting said beam,- and means for enhancing the deflection caused by said deflecting means comprising a pair of spaced metallic elements symmetrically positioned and oppositely disposed with respect to the normal path of travel of said beam and extending over the major portion of the path of travel of said beam, and a pair of spaced metallic surfaces symmetrically positioned and oppositely disposed with respect to said beam, but located on a line at right angles to an imaginary line Joining said pair of elements, said pair of surfaces having a length at least as long as said pair of elements, said surfaces being maintained 7 at a potential which i positive relative to said cathode but less positive than the'potential on said pair of elements.'

CLARENCE W. HANSELL.

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