US2411205A

US2411205A - Electron discharge device

Info

Publication number: US2411205A
Application number: US451444A
Authority: US
Inventors: Norval H Green; William B Rupp
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1942-07-18
Filing date: 1942-07-18
Publication date: 1946-11-19
Anticipated expiration: 1963-11-19

Description

Nay. 19,1946. N, E N ETAL 2,411,205

ELECTRON DISCHARGE DEVICE Filed July 18. L942. v 2 Sheets-Sheet 1 Fig.1.

Z0001. arc/name D Nov. 19,- 1946. N. H. GREEN ETAL ELECTRON DISCHARGE DEVICE File y 9 2 Sheets-Sheet 2 INV NTORS m r 'ifl TTORNEY Patented Nov. 19, 1946 ELECTRON DISCHARGE DEVICE Norval H. Green, Wood-Ridge, and William B. Rupp, East Orange, N. J., assignors to Radio Corporation of America, a corporation of Delaware Application July 18, 1942, Serial No. 451,444

8 Claims.

Our invention relates to electron discharge devices, particularly suitable for use at ultra high frequencies and utilizing a beam of electrons periodically deflected.

In one device of this kind a beam of electrons is directed through a focusing and deflecting electrode system to a collector. The focusing and deflecting electrode system comprises a tubular member having a plurality of successively spaced apertured partitions with the apertures in alignment. the apertures being elongated and of very small width. The deflecting electrodes are positioned between the apertured elements.

Serious problems present themselves in the manufacture and assembly of such devices. One of the difficulties encountered is that of aligning the apertures with the electron beam from the cathode assembly. Further difliculties are experienced in attempting to punch the transverse elements or partitions out of thin sheet metal since the apertures are of such small dimensions that conventional punches will not withstand the pressure necessary to provide the apertures.

A still further diiflculty is experienced with this i high frequencies the transit time of the electrons between the deflecting electrodes or plates is an appreciable part of the period of the applied deflecting voltage. As a result an electron passing between the plates may not receive the maximum deflection which a given voltage would normally cause. This may be explained in the following manner.

Considering an electron entering the space between the deflecting plates at the moment of zero potential difference between the plates, as the electron travels along between the plates, the voltage differential increases to maximum and then decreases to a zero value, and then again increases in the opposite direction. So long as the voltage on the' plates has the same sign the electrons will continue to be deflected in one direction but with the voltage reversed the electrons are deflected in the opposite direction. The result if an electron spends more than a half-period between the plates is a deflection less than that which would occur under optimum conditions, and the transconductance is reduced. In a copending application of Kilgore, Serial No. 342,625, flled June 27, 1940, and assigned to the same assignee as the present invention, this matter of transit time is discussed and certain relationships kind. The reason for this is that at the ultra described for obtaining optimum deflection. It has been found, however, that under certain conditions of operation, the expected deflection is not always obtained.

It is thus an object of our inventionto provide an electron discharge device of the beam deflection type, which can be easily constructed and assembled, and in which difliculty of alignment of electrode elements is substantially reduced.

Another object of our invention is to provide an electron discharge device of the type described which will avoid the difliculties pointed out in connection with forming apertured elements.

A still further object of our invention is to provide an electron discharge device which is particularly suitable for use at ultra high frequencies and in which the deleterious effects of transit time may be substantially reduced and the transconductance increased.

The novel features which we believe to be char-, acteristic of our invention are set forth with particularity in the appended claims, but the invention itself will best be understood by reference to the following description taken in connection I with the accompanying drawings in which Figure 1 is a longitudinal section of an electron discharge device made according to our invention, Figure 2 is a longitudinal section of the device shown in Figure 1 and rotated 90 with respect to the section taken in Figure 1 and its associated circuit, Figure 3 is an enlarged longitudinal section of a cathode assembly and Figure 4 is a section taken along the line 44 of Figure 3, Figure 5 is a view showing details of construction and Figure 6 is a view showing the elements shown in Figure 5 in the process of assembly, Figures 7 and 8 are views of a jig used in assembling the elements shownin Figures 5 and 6, and Figure 9 shows details of construction of the elements shown in Figures 5 and 6.

An electron discharge device made in accordance with our invention is shown in longitudinal section in Figure 1. The device comprises an evacuated envelope I 0 provided with the usual base ll. Mounted at one end of the envelope is the cathode assembly comprising an elongated cathode l3 and beam forming and shielding electrode l4, both of which are supported between the pair of insulating spacer members I5 and I6,

preferably of mica. Positioned at the other end of the envelope is collector I! in the form of a loop and supported by means of glass bead assemtron. beam from the cathode assembly. The cath- The transverse section of the device shown in I Figure 1 rotated 90 is shown in Figure ?)with one circuit suitable for use with this type of device. It will be noted that the deflecting electrodes 24 and 24' are of L-shape and supported from the transverse element 22 by means of the bead construction 24". The transverse element 22 and deflecting elements 24 and 24' are maintained in fixed position in a jig pending fixing of these elements with respect to each other with the bead construction shown. The apertured element 22 and deflecting electrode elements 24 and 24' provide a lens action as described in the copending application of Kilgore mentioned above. While for optimum results for deflection sensitivity it has been found desirable to make the length of the deflecting plates in the direction of travel of the electron beam equal to the distance travelled by an electron during a halfperiod, we have found that the capacity between the plates, or the input capacity can be greatly reduced, while decreasing the sensitivity to only a small extent by making the length of the deflecting plates in the direction of travel of the electron beam equal substantially to a third of the distance travelled by an electron during one period of the applied controlling voltage. Such a reduction of input capacity is very desirable at high frequencies.

In the arrangement shown the output is taken between the collector I and the tubular member 20 by means of the output transformer 26. Condenser 29 and resistors 21 and 28 permit the application of different D.-C. potentials on the collector and to the tubular member 20 and transverse element 23. When used as a mixer the signal may be applied to the deflecting electrodes by means of the transmission line system 38 tuned and shorted by means of the condenser shorting bar 3|, the signal being applied by transmission line 32. The local oscillator voltage may be applied by local oscillator 33 and transmission line 34, the biasing *eoltage being supplied by means of voltage source 35. The cathode shield and beam forming electrode l4 may be biased by means of the voltage source 36'. The electron disiharge device is of course useful in other circm s. I

The details of the cathode assembly are best shown in Figures 3 and 4. The cathode l3 and the cathode shield and beam forming electrode M are positioned to extend through apertures provided in the insulating spacer members l5 and I6, the element l4 being locked in position by means of the tabs I4. The insulating spacer members are provided with finger-like elements I5 and I6 which extend through the transverse apertured element 2|, the assembly being maintained in position by means of the rods I4" sealed to the element 20 and directed through apertures in the insulating elements. Due to the arrangement disclosed the emitting surface |3"' of the cathode I3 is exactly aligned with the aperture a 4 2| in the first apertured element 2|, so that the beam is not misdirected through the aperture.

As pointed out above it is diflicult to provide the transverse elements with elongated apertures of very small width due to the difficulty of providing the proper tools for this operation. In accordance with our invention we have overcome this difliculty with the construction shown in Figures 5 and 6 and by means of the method described in connection with Figures 5 to 8, inelusive.

As shown in Figure 5, apertured transverse element 23 comprises a disc-like member having positioning apertures 39 and another aperture 39" over which the plate-

like elements

36 and 31 are positioned and secured to provide the slot. Longitudinally of the slot is positioned a rod-like element 38 which will be described in more detail below, to provide a double aperture.

In Figures 7 and 8 is shown a jig arrangement for assisting in the assembly of the transverse,

element 23. It comprises a base 40' having a pair of pin-like elements 4| and an elongated element 42 with a rectangular cross section which as observed is off center with respect to the pin-like member 4|. In assembly, element 23 is positioned over the pins 4| which extend through apertures 39. The element 36 is then positioned against the stop member 42 which fits into' the recessed portion 36' of the element 36 and is welded in position. The entire arrangement is then lifted from the jig and rotated 180 and the element 31 then positioned in place in the same manner as element 36 was secured in place. The aperture is then fixed with respect to the element 23'.

To properly center and flx the rod-like element 38 to provide in eflect a double aperture, the

elements

36 and 31 are beveled on their underside adjacent the aperture as shown at 36" and 31" in Figure 9, and the wire 38 is of such diameter that it fits with slidable contact between

elements

36, 31 and the element 23. Only one end of this rod-like element 38 is secured to the disc 23 to thereby permit longitudinal expansion and contraction of the element due to changes in temperature during operation. The element 38 is thus positively fixed in position with respect to the aperture but at the same time is permitted to expand and contract without causing the element to bow or bend and thereby adversely aiIect the control voltage characteristic of the device.

Thus we provide an electron discharge device utilizing a periodically deflected beam whichmay be easily formed and assembled and in which alignment of the electrode elements is assured.

In accordance with our invention transit time effects are reduced to a minimum so that the transconductance of the tube may be large.

While we have indicated the preferred embodiments of our invention of which we are now aware and have also indicated only one specific application for which our invention may be employed, it will be apparent that our invention is by no means limited to the exact forms illus-' collector for receiving said electrons and means intermediate said cathode means and collector for focusing and controlling the beam of electrode assembly including a cathode and a pair of l! spaced supporting insulating members provided with elements extending from said supporting insulating members and having oppositely disposed aperturu receiving the ends of said cathode, one of said transverse elements having apertures for receiving the elements on said insulating members whereby said cathode and the other apertures of the transverse elements are positively aligned.

2. An electron discharge device having a cathode means for supplying a beam of electrons, a collector for receiving said electrons and means intermediate said cathode means and collector for focusing and controlling the beam of electrons, the intermediate means having a plurality of elements transverse to the path of said beam and provided with apertures, said apertures being aligned, said cathode means comprising an electrode assembly including a cathode and a pair of spaced supporting insulating members, said insulating members comprising fiat plate-like elements having fingers extending from one edge thereof and oppositely disposed, and having oppositely disposed apertures receiving the ends of said cathode, one of said transverse elements having apertures for receiving the fingers on said insulating members whereby said cathode and the other apertures of. the transverse elements are positively aligned.

3. An electron discharge device having a cathode means for supplying a beam 01' electrons, a collector for receiving said electrons and means intermediate said cathode means and cpllector for focusing and controlling the beam of electrons, the intermediate means having a plurality of elements transverse to the path of said beamand provided with apertures, said apertures being aligned, said cathode means comprising an electrode assembly including a cathode and a pair 01! spaced supporting insulating members provided with elements extending from said insulating members and having oppositely disposed apertures receiving the ends of said cathode, one of said transverse elements having apertures for receiving the elements on said insulating members whereby said cathode and the other apertures oi the transverse elements are positively aligned, said intermediate means including a pair of deflecting electrodes adjacent one of the transverse elements for deflecting the beam of electrons across the aperture of a transverse element more closely adjacent to said collector.

4. An electron discharge device having a cathode means for supplying a beam of electrons, a collector for receiving said electrons and means intermediate said cathode means and collector for focusing and controlling the beam of electrons, the intermediate means having a plurality of elements transverse to the path of said beam and provided with apertures, said apertures being aligned, said cathode means comprising an electrode assembly including a pair of spaced supporting insulating members provided with elements extending from said insulating members and having oppositely disposed apertures receiving the ends of said cathode, one of said transverse elements having apertures for receiving the elements on said insulating members whereby said cathode and the other apertures of the transverse elements are positively aligned, the transverse element adjacent the collector comprising a sheetlike element having an aperture centrallylthereoi', a pair oiplate-like elements positioned on and secured to said sheet-like element with their adjacent edges in abutment, the adjacent edges of said plate-like elements being provided with registering recessed portions providing a, narrow slot registering with the aperture in said sheet-like element and of smaller dimensions than said last aperture.

5. An electron discharge device having a cathode means for supplying a beam of electrons, a

collector for receiving'said electrons and means intermediate said cathode means and collector for focusing and controlling the beam of electrons, the intermediate means having a plurality ing members provided with elements extending from said supporting insulating members and having oppositely disposed apertures receiving the ends of said cathode, one of said transverse elements having apertures for receiving the elements on said insulating members whereby said:-

cathode and the other apertures oi the transverse elements are positively aligned, the transverse element adjacent the collector comprising a sheet-like element having an aperture centrally thereof, a pair of plate-like elements positioned on and secured to said sheet-like element with their adjacent edges in abutment, the adjacent edges of said plate-like elements being provided with registering recessed portions for providing a narrow slot registering with the aperture in said sheet-like element and of smaller dimensions than said last aperture, and a rod-like element extending longitudinally of said slot and centrally thereof.

6. An electron discharge device having a cathode means for supplying a, beam ,of electrons, a collector for receiving said electrons and means intermediate said cathode means and collector for focusing and controlling the beam of electrons, the intermediate means having a plurality of elements transverse to the path of said beam and provided with apertures, said apertures being aligned, said cathode means comprising an electrode assembly including a cathode and a pair of spaced supporting insulating members provided with insulating elements extending from said insulating members and having oppositely disposed apertures receiving the ends of said cathode, one of said transverse elements having apertures for receiving the elements on said insulating members whereby said cathode and the other apertures of the transverse elements are positively aligned, said intermediate means in-' 7 of elements transverse to the path of said beam and provided with apertures, said apertures being aligned, said cathode means comprising an electrode assembly including a, cathode andmeans aligning said cathode with the apertures of the transverse elements, said intermediate means including a pair of deflecting electrodes adjacent one of said transverse elements for deflecting the beam of electrons across the aperture in another transverse element nearer to said collector, said deflecting electrodes having a dimension in the direction of travel of the electrons substantially equal to the distance travelled by an electron during substantially onethird of a period of the voltage applied to said deflecting electrodes.

8. An electron discharge device having a, cathode means for supplying a beam of electrons, a collector for receiving said electrons and means intermediate said cathode means and collector 20 for focusing and controlling the beam of electrons, the intermediate means having a plurality oi. elements transverse to the path of said beam and provided with apertures, said apertures being aligned, said cathode means comprising an 25 sheet-like member.

electrode assembly including a cathode and a pair of spaced supporting insulating members 8 provided with fingers extending from said insulating members and having oppositely disposed apertures receiving the ends of said cathode, one of said transverse elements having apertures receiving the fingers on said insulating members whereby said cathode and the apertures in the transverse elements are positively aligned, said intermediate means including a pair of deflecting electrodes adjacent one of said transverse elements for deflecting the beam of electrons across the aperture in a transverse element nearer said collector, said deflecting electrodes having a di-' mansion in the direction of travel of the electrons substantially equal to the distance travelled by an electron during one-third of a period 01' the applied controlling voltage on said deflecting electrodes, the transverse element adjacent the collector comprising a sheet-like member having an aperture centrally disposed thereof, a pair of sheet-like elements positioned over said aperture and having adjacent edges contacting, said ad jacent edges being provided with elongated slotlike recesses cooperating to provide an elongated narrow slot registering with the aperture in said NORVAL H. GREEN. WILLIAM B. RUPP.