US2547631A

US2547631A - Electron tube and circuit therefor

Info

Publication number: US2547631A
Application number: US74590A
Authority: US
Inventors: Jr William E Evans
Original assignee: Individual
Current assignee: Individual
Priority date: 1949-02-04
Filing date: 1949-02-04
Publication date: 1951-04-03
Anticipated expiration: 1968-04-03

Description

April 3, 1951 w. E. EVANS, JR

ELECTRON TUBE AND CIRCUIT THEREFOR Filed Feb. 4, 1949 I N VEN TOR. l Vi/fiam 5 Evan 5, Jr W A rrozA/svs ll 2 a a 9 n 3 m h h c c N 8 9 3 3 II II|III|PIIIIII 2w It L? 5 3 II llllllLllll a 3 S B Patented Apr. 3, 1951 UNITED STATES PATENT OFFECE Claims. I

This invention relates generally to vacuum tubes of the electron beam type, and to circuits making use of the same.

In the p-astradio systems have been proposed which make use of twohigh frequency amplifier channels connected in opposed phase relationship to a common antenna output. Each channel is phase modulated in response to a common source of modulating frequency, whereby the resuiting unbalance in the phase relationship between the two channels provides an intensity modulated output to the antenna. Circuits which have been proposed for such systems (sometimes referred to as phase-to-amplitude systems) are unduly complicated, due largely to the type of electron or vacuum tubes employed for phase modulation.

It is an object of the present invention to provide an electron tube which is capable of greatly simplifying systems of the type described above,

. and which incorporates in its construction all that is necessary for securing simultaneous phase modulation of two high frequency channels:

Another object of the invention is to provide an electron tube of the above character capable of supplying relatively large output energy for a tube of given size.

Another object of the invention is to provide a new circuit of the phase-to-amplitude type,

making use of my tube, and which is simpler and more effective than prior available systems. Further objects of the invention will appear from the following description in which the preferred embodiment has been set forth in detail in conjunction with the accompanying drawing.

Referring to the drawing: Figure l is a side elevational view of an electron. tube incorporating the present invention.

Figure 2 is a fragmentary view of the tube shown in Figure 1, but with the parts rotated through 90.

Figure 3 is a circuit diagram illustrating the tube of Figures 1 and 2 incorporated in. a circuit for phase-to-amplitude modulation.

, The electron tube illustrated in Figures 1 and 2 is of the beam type, is provided with an electron gun of the electrostatic lens type for forming an electron beam and for accelerating and focu ing the beam upon collecting means. The collect n means consists of two extended collecting electrodes which are disposed at an angle with respect to each other, and also inclined with respect to the normal axis of the beam. Th se collecting electrodes are separated by an additional element as will be presently explained. In addition the tube is provided with a grid for varying the beam intensity, and

with deflecting electrodes adapted to receive voltages for deflecting the beam laterally. In place of an'electron gun of the electrostatic lens type, I can employ any other type of gun struccontrol grid IS, the accelerating anode l4, and

the focusing electrode I 5. Deflecting electrodes IE, which are disposed upon opposite sides of the axis of the beam, can be connected to separate external'terminals IT. A pair of collecting electrodes I8 are provided which are in the form of elongated metal strips. These electrodes can be connected to and supported by the external terminals l9. As illustrated they are planar in form, although in some instances they may be formed with a predetermined amount of curvature to obtain a desired nonlinear modulation characteristic.

It will be noted from Figure 1 that the two collecting electrodes I8 extend at an angle of substantially with respect to each other, and that each element is at an angle of substantially 45 with the axis of the tube (which axis corresponds to the normal undefiected axis of the electron beam) Normally the focusing electrode 15 is so shaped, and is maintained at such a potential, that the electron beam produced is substant ally rectangular in transverse cross-sectional contour. The length of the cross-sectional contour of the beam in the vicinity of the electrodes l8 should be ample to insure simultaneous impingement over eoual areas on both of the col ecting electrodes. The width of this crosssectional contour should be such that the areaof impingement upon each collecting electrode at any one instant is a minor fraction of the length of the electrode. For exa ple where each collecting electrode may be say 2 inches in length, the extent of impingement may be for the full width of the electrode, and for a distancealong the length of the electrode of say 0.1 inch.

The electrode 2! which is interposed between the collecting electrodes [8 is normally positively biased. As will be presently explained, in operation secondary emission occurs from the collecting electrodes 18, and such secondary emission is utilized in conjunction with electrode 2| to remove the physically long electron beam and return path from a high frequency output circuit, and to obtain some power gain for the output.

Figure 3 illustrates a complete system utilizing the tube of Figures 1 and 2. In this system a suitable power supply 26 is shown connected to the cathode i2, the accelerating electrode Hi and the focusing electrode l5. The focusing electrode can be grounded as illustrated. There is also a connection, through the high frequency choke 2'! to the control grid E3, in order to properly bias the same. A source of modulating voltage 28 is shown connected to the two deflecting electrodes I6. A high frequency source .29, such as a pilot oscillator and amplifier, is connected to supply voltages of a desired carrier frequency to the grid l3, through the coaxial transmission line 3i and the coupling means 32.

The output terminals I? of the tube are shown connected to the coaxial transmission lines 33.

Y which are adjusted to be resonant to the frequency of the source 29. Thus the effective electrical length of each line is made equal to onequarter wave length. A conductor 35 connects with th terminal 22, and leads to the power" supply 26 or some other source of voltage for maintaining a desired positive bias upon the electrode 2!. A high frequency by-pass condenser 37 connects between the terminal 22 and ground. Coaxial taps 33 are connected to the transmission lines 33, and serve to supply energy to the two high frequency channels 39. These channels may include high frequency electronic amplifying means, and their outputs are connected in opposed phase relationship to the common antenna 4 l which forms an output load.

Assuming that there is no voltage difference between the deflecting electrodes It, the electron beam impinges upon the middle portions of the two collecting electrodes I8. High frequency voltages applied to the control grid 53 from the source 29 (for example at a frequency with a range of say from 100 to 300 megacycles), cause intensity modulation of the electron beam, with the result that the collecting electrodes l3 supply high frequency energy to the resonant transmission lines 33, and from thence to the channels 39. For this condition the phase relationship between the outputs of the two channels 39 can be such (as for example about 135) that the resultant output to the antenna ll corresponds to carrier level. Assuming now that a voltage difference is applied to the electrodes Iii from the modulating source 28, the electron beam will be deflected (upwardly or downwardly as the tube viewed in Figure l) and as a result one portion of the beam which impinges upon one collecting electrode I8 is effectively shortened, whereas the other portion of the beam which impinges the other collecting electrode is effectively lengthened. This results in 2. corresponding shift in the phase relationship of the high frequency energy supplied to the two resonant transmission lines 33. Positive modulation serves to bring the two channels more in phase to produce the peaks of modulation, and negative modulation brings the two channels more out of phase, thus reducing the output for producing the modulation troughs. In a typical instance the modulating voltages applied to the deflecting electrodes it will be of video frequency in order to secure amplitude modulation or a television transmitter.

The energy output from the collecting elec trodes I8 is relatively great due to the effect of secondary emission. Thus as a result of impingement of primary electrons upon the electrodes i8, secondary emission occurs, thus causing current flow to occur between each collecting electrode and the intermediate associated electrode 2:. By the use of secondary emission in this fashion a tube of given size will have a relatively high power gain, thus greatly simplifying the design of the tube, and also the design of the amplifying channels 39 and other parts of the electrical. system with which the tube is used.

I claim:

1. In a vacuum tube, means for forming an electron beam, a pair of collecting electrodes oppositely inclined to the normal axis of the beam and adapted to collect electrons from the same, said beam being proportioned to form two adiacent beam sections for impingement on those portions of both the collecting electrodes which are in the path of the beam at any one instant,

' a control grid for controlling the intensity of the beam in accordance with the frequency of voltages applied to the same, and means for causing lateral deflection of the beam to thereby oppositely vary the phase relationship between the frequency of voltages applied to the control electrode and voltages assumed by the collecting electrodes.

2. In a vacuum tube, means for forming an electron beam, a pair of collecting electrodes oppositely inclined to the normal axis of the beam, said beam being proportioned to form two adjacent beam sections for impingement on those portions of both the collecting electrodes which are in the path of the beam at any one instant, a metal element adapted to be positively biased and disposed between the collecting electrodes and parallel to the normal axis of the beam, a control grid for controlling the intensity of the beam, and means for effecting lateral deflection of the beam to thereby oppositely vary the phase relationship between the frequency of voltages applied to the control grid and voltages assumed by the two collecting electrodes.

3. In a vacuum tube, means for forming a beam of electrons, a pair of collecting electrodes onpositely inclined to the normal axis of the beam, said beam being proportioned to form two adiacent beam sections for impingement on those portions of both the collecting electrodes which are in the path of the beam at any one instant,

a metal shied being disposed between the collecting electrodes with its plane para lel to the normal axis of the beam, a control grid for contro ling the intensity of the beam, said sh eld being adapted to be ositive y biased and said collectin electrodes being capable of secondary emi sion, and means for efiecting lateral defl ction of the beam in a plane parallel to said shield.

4. In an. electronic system employing phaseto-inten -ity modul t on, a vacuum tube, said vacuum tube including means forming an electron beam, a pair of collecting electrodes oppositely inclined to the normal ax s of the beam and adapted to collect electrons from the same,

beam being proportioned to form two adjacent beam sections for impingement on those portions of both the collecting electrodes which are in the path of the beam at any one instant, a control grid for controlling the intens ty of the beam in accordance with voltages applied to the frequency energy coupled to apply voltages to the control grid, a pair of output channels coupled to the collecting electrodes, an output load, the outputs of said channels being connected in opposed phase relationship to the load, and means for applying modulating voltages to the deflecting electrodes, whereby deflection of the beam responsive to said modulating voltages causes changes in phase relationship between said channels to efiect intensity modulation of high frequency energy supplied to the load. I

5. In an electronic system employing phaseto-amplitude modulation, a vacuum tube comprising means forming an electron beam, a pair of collectin electrodes oppositely inclined to the normal axis of the beam, said beam being proportioned to form two adjacent beam sections for impingement on those portions of both the collecting electrodes which are in the path of the beam at any one instant, a metal shield disposed between the collecting electrodes with its plane parallel to the normal axis of the beam, said shield being interposed between two adjacent sections of the beam which impinge upon the collecting electrodes, a control grid for controlling the intensity of the beam, and deflecting electrodes for effecting lateral deflection of the beam in a plane parallel to said shield, a source of high frequency energy coupled to the control grid to efi'ect high frequency-intensity modulation of the beam, a source of modulatin voltage coupled to the deflecting electrodes whereby the beam is deflected laterally in ac-' the load of an intensity dependent'upon the magnitude of the modulating voltages,

WILLIAM E. EVANS, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,165,308 Skellett July 11, 1939 2,265,145 Clarke Dec. 9, 1941 2,274,194 Farnsworth Feb. 24, 1942