US2400753A - Electron discharge device and associated circuit - Google Patents

Description

m y 21, 6- A. v. HAEFF zA-mfis ELECTRON DISCHARGE DEVICE AND ASSOCIATED CIRCUIT Filed July 25,- 19 42 '5 Sheets-Sheet 1.

VENTOR May 21, 1946.

A. V. HAEFF ELECTRON DISCHARGE DEVICEAND ASSOCIATED CIRCUIT Filed July 25,1 1942 3 "Sheets-Sheet 2' May 21, I946.

A. v. HAEFF 2,4,753

ELECTRON DISCHARGE DEVICE AND ASSOCIATED CIRCUIT Filed July 25, 1942 3 Sheets-Sheet 3 output as useful energy. This grid emission cur- 50 end to the tubular member H, the other end of ELECTRON DISC GE DEVICE AND ASSOCIATED CHtCUI'K Andrew V. Haefi, Washington, ll). (3., assignor to Radio Corporation of America, a corporation of Delaware Application July 25 1942, Serial No. 452,302

9 Claims. (Cl. 250-275) My invention relates to electron discharge deplate emciency. Itis desirable to have the elecvices and associated circuits particularly suittrons collected by the plate at a low velocity and able for ultra high frequencies as high power outto remove the electron receiving surface away puttubes which are useful as amplifiers or oscilfrom the grid to reduce heat absorbed by the lators. I grid. But with the usual three-electrode ar- In electron discharge devices intended for high ransement with the collector anode at a high power output and particularly for use at ultra po itive ta in der to d t necessary high frequencies, close spacing of the electrodes plat ur e t, t is s n t nt yf as l and high operating voltages are requisites. Op- It is therefore, an object of my invention to timum operating conditions for maximum output 10 p vide an lectron dis harge device having ahie require a maximum instant grid voltage and a power output and which is suitable for use at minimum instant plate voltage when the peak ultra high frequencies as an amplifier or oscillaplate current flows. However, for the usual elector. tron discharge device undesired grid emission due More Sp y. it is another jec o y to electron bombardment from the cathode and invention to provide n electron disch r e deheating of the grid by radiated heat from the vice in which grid emission is substantially reelectron collecting surface of the anode or colduced. lector may result. Grid and plate circuit load- A still further object of my invention is to proing, burning out of the grid and increased heat-. vlde an electron discharge device in which the ing at the anode, which represents wasted enelectrons may be collected at a low velocity to ergy and hence a lowering of the efficiency of reduce the energy dissipated in heat.

the electron discharge device, may occur under These d t r Objects W l pp hereinthese conditions. after.

In the case of oscillators either self-biasing re- The novel features which I believe to be charsistors may be used or fixed bias may be used to acteristic of my invention are set forth with parobtain the proper biasing voltage on the grid. ticularity in the appended claims, but the inven- Where a self-biasing resistor is used between grid v tion itself will best be understood by reference to and cathode, when the grid is positive, electrons the following description taken in connection strike the grid and cause secondary emission, with the accompanying drawings in. which Figwhich results in current flowing in the grid cirure 1 is a longitudinal section of an electron discuit. This results in a higher positive bias being ha ge device and associated circuit made ac-- placed on the grid, thus further increasing the cording to my invention and Figures 2, 3, 4 and positive grid potential and the velocity of the elec- 5 show longitudinal sections of modifications of trons bombarding the grid. This building up of the electron discharge device shown in Figure l.

the positive bias on the grid may cause the grid In Figure 1 I provide an. apparatus which can to burn out. be used as a high power triode amplifier or as an In the case of a fixed bias, while the bias itself oscillator. It includes an indirectly heated cathdoes not increase, nevertheless when the grid is ode l0 followed by a grid II and an anode or at positive peak and the plate voltage is at a collector l2 having cooling fins l2. The enminimum positive voltage, electrons striking the 40 velope is formed by means of the conducting colgrid cause it to heat up, thus causing emission lar member l3 closed at one end by the cupfrom the grid. Electrons emitted from the grid shaped insulating member I l and at its other during the next half cycle, when the grid is negend by the insulating collar member l5 and ative and the anode positive, cause the electrons collector l2 provided with the collar member 21 from the grid to be accelerated toward the sealed to the collar l5. The cathode heater l0 anode with maximum velocity. These high veis provided with a lead 16 extending through the locity electrons strike the anode with considerenvelope. The cathode I0 is supported by means able force and dissipate their energy in heat. of the conductors and leads l8 arranged in a Thus, energy is wasted and does not go into .the circle around conductor l6 and secured at one rent, of course, also loads down the plate circuit, the tubular member I! being secured to the leads another undesirable factor, l9 extending through the envelope. Members In order to minimize grid emission, lower peak I1, I13 and it serve as the other lead for the oathgrid voltages are required, which as pointed out ode heater and as the cathode lead. Insulatabove means higher plate voltages with lower ing disc 20 properly-centers conductor it with respect to tubular member ll. The grid II is supported by means of conducting collar member 2| 'secured to the tubular conducting member |3 forming part of the tube envelope, the grid and cathode supports being separated by means of the insulating disc 22. The collector I2 is provided with the member 25 decreasing in diameter toward the grid to protect the seal and provide a proper field for the electrons. .Across the opening is placed the wire mesh 25 for bringing about the proper field formation through which the electrons pass from the grid to the interior of the collector l2. This has the effect of minimizing effective transit time between grid and anode.

The input circuit connected between the grid and cathode comprises the outer tubular member 28 electrically connected to the. collar memher I3 and an inner tubular member 23 capacity coupled at its inner end to the element 32 contacted by the spring-like elements 30 secured to the cathode leads. The member 32 electrically connected to the elements. 30 provides one conductor through which the heating current flows to the cathode heater. The inner conductor I5 is engaged by means of a spring clip member 34 positioned on element 33 capacity coupled to element 32. through which the cathode direct current flows to the heater and at the same time provides a path for radio frequency currents. It will thus be observed that the grid collar 2|, collar l3, member 28, member 29, capacity coupling element 32, leads 30 and I9, tubular member I! and leads l8 provide a coaxial line type resonant cavity circuit completely isolated from other circuits. It is tuned by means of the collar-like element 35 slidably supported on the inner tubular member 29 by means of the insulator support 35'.

The output circuit includes a drum-like member 36 electrically connected to collar l3 of the envelope and provided with a disc-like element 31 capacity coupled to the disc-like element 38 positioned transversely of the collar member 21 of the collector 2. and electrically connected thereto. Energy from the output tank circuit is coupled back to the input circuit by means of the coaxial transmission line comprising inner conductor 39 and outer conductor 40. This line is made adjustable to insure proper phase rela tionship of the energy feedback with respect to the voltages in the input circuit, the inner conductor being provided with coupling loops 4| and 42. This adjustable transmission line is described in greater detail and claimed in my copending application Serial No. 455,175, filed August 18, 1942, and assigned to the same assignee as the present application. These' couplingvloops could be made adjustable to control the amount of feedback. This arrangement permits both the input and output circuits to be adjustedindependently of each other and for optimum operating conditions. The output is taken by means of loop 45 which feeds into the coaxial transmission line 41.

- voltage applied between the grid II and cathode ,,|0 ,modulates'the electron streampassing tothe collector l2. Themodulated electron stream in passing across the gap between the grid II and This arrangement provides means.

within the coaxial transmission line acting as the input resonant cavity circuit and comprising members 25 and 29. Tuning of the input circuit is accomplished by means of the tuning collar 35 which may be moved longitudinally of the input circuit. Output may be taken from the resonator 35 by means of the coupling loop 46- and coaxial transmission line 41. In order to feed the energy from the output resonator to the input resonant cavity circuit in proper phase,

the length of the transmission line 33-43 may be varied by varying the position of the movable U-shaped element 40' of this line to increase or decrease the length of the line.

In the apparatus shown in Figure 1, the input and output circuits are completely isolated from each other. Due to the fact that electrons are collected at a surface far removed from the grid little radiated heat is absorbed by. the grid. This eliminates much of the difllculty due to grid emission caused by absorption of heat due to the energy dissipated at the surface of the collector; The large collar-like support 2| for the grid acts as a means for conducting heat away from the grid rapidly to thus further maintain the grid at a low temperature. In'eflect close spacing of the electrodes is obtained by means of the structure shown without actually placing the collecting surface close to the grid, thus making the device suitable for use at ultra high frequencies where transit time between the electrodes becomes important. The capacity colipling between theoutput circuit and the anode or collector permits different voltages to be applied to the circuit and the collector and yet at the same time provides a resonant cavity type of circuit which is particularly suitable for use at ultra high frequencies. The apparatus shown in Figure 1 can be used either as an amplifier or oscillator by controlling the amount and phase of the energy fed into the input circuit.

In Figure 2 is shown a modification of the device shown in Figure 1 and employing ring type seals. The modification shown in this figure has an added advantage in that the collector may be maintained at a low voltage with respect to some other electrodes within the tube so that the electrons can be collected at a lower velocity than is possible in the apparatus shown in Figure 1, thus further increasing the efliciency of the tube. a ,The envelope 50 contains an indirectly heated cathode 5|, grid 52, output and accelerator electrode 53,- ring-like secondary electron suppressor 54 and cup-shaped collector 55. The cathode, grid and accelerator electrodes are supported by means of ring members 55, 51 and 55 sealed through the glass envelope. These ring members provide low loss, low inductance leads for the electrodes and merge into the circuits utilized with the device.

The input circuit comprises a flat drum-like member 60 electrically connected to the ring 51 and capacitively coupled to the cathode ring 56 by means of the disc-like member 55' electricallyconnected to the cathode ring 55. The output resonant cavity comprises the drum-like member 5| having a wall 62 capacitively coupled to the flat disc-like element 63 electrically connected to the accelerator electrode ring 58. The two circuits are coupled by means of a transmission line formed by an annular shaped member 65 surrounding the input circuit. Within member 54 is supported the inner conductor 55 having coupling loop 65 positioned within the input circuit and a, coupling loop 67 positioned in the output circuit. This transmission line permits in efiect along line occupying a small space.

Cathode heating energy is supplied by means of the transformer 68 and the grid biasing voltage supplied by means of the dropping resistor 59. The collector electrode and suppressor electrode voltages are supplied by means of the voltage source 15, the suppressor being at the lower potential. The output is taken in the usual way by loop With the arrangement shown the accelerator The input circuit comprises the outer tubular member 8'! electrically connected to the inner tubular member 58 by means of the closure member M. The inner tubular member 58 is capacitively coupled to the'collar 89 secured to the outer ends of the leads andsupports 52, the insulating electrode 53 is maintained at a high potential suflicient to draw a large cathode current. Practically no current is drawn by the accelerator 53 so that little energy is dissipated in this electrode. Collector 55 which is outside the radio frequency circuit may be maintained at a lower potential than would be the case if it acted as an output electrode and hence electrons are collected at a lower velocity so that energy wasted as heat is reduced. The input and output circuits are completely isolated from each other and the amount of feedback can be controlled as well as its phase by means of the transmission line which can be made adjustable. 1

In the apparatus shown in Figure 2 an alternating high frequency voltage applied between cathode 5! and grid 52 modulates the electron stream from cathode 5i and which passes to the accelerator and output electrode 53 and is collected by collector 55, secondaries from 55 being suppressed by electrode 55. The modulated electron stream collar 55 serving to separate members 88 and 85. The input circuit may be tuned by a member 92 slidable longitudinally of the input circuit.

The output tank circuit includes the resonant cavity structure comprising the member 53 and having one wall 55 provided with an outside annular member 95 in which the conducting disc 55 is supported by means of insulating discs 51 and 98. This disc is provided with spring contact engaging members 55 contacting member 85. This construction permits the envelope to be withdrawn from the output tank circuit and disengaged therefrom. Another wall it of the resonant cavity is supplied with spring contact members Iii! engaging the conductors supporting the grid. The cathode heating circuit ineludes transformer I66 connected to leads 5! and 82 by spring contact members 8! and 82'. Voltage source lllt supplies accelerator electrode is maintained at a higher potential than the collector by means of voltage source I 59. Thus, the envelope and its electrodes may be disengaged from the circuits by pulling the envelope to the right.

Energy may be returned to the input circuit to neutralize input losses or cause the tube to function as an oscillator by means of the transmission line having inner conductor W5 and 5 outer conductor I02, one end being provided with coupling loop 803 and the other with coupling loop EM. Intermediate the concentric transmission line is a U-shaped adjustable portion comprising the conductors Hi5 and mr, which are in passing across the gap between grid 52 and 4 telescopicallyengaged with the coaxial line. Thus,

accelerator 53 induces a voltage acrossthe gap, causing energizationof the resonator 6!. The accelerator 53 is capacitively coupled by means of the element 58 and wall 62 of resonator M, the R. F. field being confined within this resonator. The collector, therefore, is extemalto the R. F. circuit. The input resonant cavity circuit comprises resonator Gt electrically connected to the grid 52 through collar 51 and capacitively coupled for R. F. to the cathode by means of elements 56' and the radially directed ring-like conducting support 56 of the cathode 5|. Energy is fed back into the input circuit by means of the transmission line comprising the loop 51', coil 55 within the annular box-shaped arrangement 65 and loop 66 within the input resonator. This causes the device to operate as an oscillator.

In Figure 3 is shown a further modification of the construction shown in Figure 2 and provided further with an adjustable transmission line for controlling the phase of feedback. In this modification the envelope 15 contains the indirectly heated cathode 16, grid 11, output and accelerator electrode 18, suppressor electrode 19 and collector 80, the cathode heater being supplied through the conductor 8| and conductors 82 surrounding the conductor BI and serving as a. support for the cathode. The gridis supported on collar 83, which in turn is supported on leads and support wires 85 surrounding conductors 82 and extending through the envelope of the tube. The accelerating electrode is supported by means of radially directed collar 85 connected to and supported by the radially directed ring-like conductor 86 extending through the envelope.

by varying the length of this line the phase relationship of the energy fed back from the output circuit to the input circuit can be controlled to insure the desired phase relationship. The output is taken by means of coupling loop H5. Otherwise the apparatus functions in a manne similar to that shown in Figure 2.

, electrodes.

The cathode m is provided with an inner heater conductor Il'l and'outer conductors and leads H8 surrounding conductor N1, the input circuit being provided by means of the tubular member I20 capacitively coupled to the outer tubular member l2! by means of the collar I23 having a supporting disc 123' connected between it and the inner tubular member I25. Member IN is connected to grid leads 2" connected to collar H2! of grid 2.

The output electrode H3 is provided with a radially extending supporting and conducting member H4 electrically connected to the disc I26 closing one end of the tubular member I214 .which is closed at the other end by means of the disc I25 to provide the output tank circuit of the resonator type connected between the 75 grid and output electrode. The output circuit er or oscillator.

4 I is energized in the usual way by inductive effect when the modulated stream of electrons passes across the gap between grid II! and output electrode II I. Tuning ofthe input circuitis accom-' ,axially of the output circuit.

Coupling between the input and output circuits is provided by means of the coupling loop I3I, the output being taken by means of output coupling loop I32; Cathode heating current is provided by voltage source I33 and proper bias on the grid by means of dropping resistor Ill. The collector voltage is supplied by means of voltage source Ill.

Thus the electrode II 3, which is maintained at control grid potential serves to minimize capacitance between the control grid and collector. Large capacitance between the, collector and electrode II3 serves to bypass radio frequency currents. The electron collecting area of the collector is far removed from the control grid and cathode so that the grid may be run quite cool.

In Figure 5 is shown another arrangement in which the collector may be maintained at a lower positive'potential than the output electrode or accelerator. A separate high positively biased electrode is used to get high peak currents. This electrode does not take current. The collector is outside of the radio frequency circuit and has a potential applied only suflicient to collect the electrons. Thus, there results a high efiiciency apparatus of the kind shown in Figure 3, but

without the need of an external capacity coupling arrangement.

In this arrangement the envelope I66 contains the cathode I50, and grid I60 supported on collar I 6|. The screening and shielding electrode I6! is supported by the radially extending support and lead arrangement I63 which extends through the wall of the envelope. The collector I64 is positioned to receive electrons from the cathode, the accelerator I65 being positioned within the screen electrode I62.

The input'circuit comprises the outer tubular conductor I'Ill connected to the grid leads and supports I6I' and the inner tubular member III which is connected to the cathode leads and support I691. The output circuit comprises the resonant cavity circuit I61 having a wall I66 electrically connected to the radial leads I63 and another wall I66 electrically connected to the tubular member- H0. The two circuits are coupled by means of the coupling loop I12. Cathode heating current is supplied by means of transformer I14 through lead I66 and leads I69 and grid bias voltage by means of 'voltage source I13. The accelerator and collector voltages are supplied by potential sources IIIi and Ill. The output is taken'by coupling loop I86.

In the last arrangement described the collector is maintained at a lower potential than the accelerator.

- High freq'uency apparatus made according to my invention eliminates or substantially reduces the difllculties due to grid emission; Efficiency is increased by providing means for collecting the electrons at low velocity. This is accomplished while at the same time providing high power outputs whether the apparatus is used as an ampli- My apparatus also provides a ready means for disconnecting the electrodes from the associated circuits, thus making avail-' able an electron discharge device and an associated circuit apparatus permitting ready replacement in case of damage to the tube or where replacement is desired for other reasons.

While I have indicated the preferred embodiments of my invention of which I am now aware and have also indicated only one specific application for which my invention may be employed, it will be apparent that my invention is by no means limited to the exact forms illustrated or the use indicated, but that many variations may be -made in the particular structure-used and the purpose for which it is employed without departing from the scope of my invention as set forth in the appended claims. 1

What I claim as new is:

1. An electron discharge device having an envelope containing a cathode for supplying electrons, a control grid electrode and another electrode in the order named, a conductor for said cathode extending through said envelope, said grid electrode being conductively connected to a conducting means having" a conductive surface outside said envelope, a cavity resonator surrounding said envelope and coupled between said control grid electrode and said other electrode,

and including a conducting member coaxial with said control grid electrode and coupled to said conducting means, said conducting means forming a continuation of the wall of said cavity resonator and a cathode-grid resonator coupled between said cathode and grid, and feedback means for controlling the energy feedback connecting said cavity resonator to said cathode-grid resona-. tor.

2. An electron discharge device having an envelope containing a cathode for supplying electrons, a control grid electrode and another electrode within said envelope in the order named, a

lead for said cathode, said control grid electrode being conductively connected to a conducting and supporting means having a conducting surface outside said envelope, a cavity resonator surrounding said envelope and coupled between said control grid electrode and said other electrode, one wall of said cavity resonator being coupled to said conducting surface on the outside of said envelope, said conducting and supporting means forming a continuation of the wall of said cavity resonator and a control grid electrode-cathode cavity resonator coupled between said cathode and control grid electrode, and means connected between said resonators for controlling the energy transferred from one resonant cavity circuit to the other cavity resonator.

3. An electron discharge device having an envelopecontaining a cathode for supplying electrons, a control grid electrode and another electrode lthin said envelope in the order named, a conduc or for said cathode extending through said envelope, said control grid electrode being conductively connected to a conducting and supporting means having a conducting surface outside said envelope, a cavity resonator surrounding said envelope and coupled between said control grid electrode and said other electrode, one

wall of said cavity resonator being coupled to said conducting and supporting means, said conducting and supporting means forming a continuation of the wall of said cavity resonator and a control grid electrode-cathode cavity resonator coupled between said cathode and control grid electrode, said cavity resonator coupled between the cathode. and control grid electrode comprising a velope and coupled the energy transferred from one cavity resonator,

to the other cavity resonator.

4. An electron discharge device having an envelope containing a cathode for supplying electrons, a control grid electrode and another electrode within said envelope in the order named, a conductor for said cathode extending through said envelope, said control grid electrode shielding said cathode from the other electrode and provided with conducting and supporting means having a conducting surface external of said envelope, a cavity resonator surrounding said enbetween said control grid electrode and said other electrode, one wall of said cavity resonator contacting the conducting surface of said conducting and supporting means outside of said envelope, said conducting and supporting means forming a continuation of the wall of said cavity resonator and a control grid electrode-cathode cavity resonator coupled between said cathode and control grid electrode, said cavity resonator coupled betweenthe cathode and control grid electrode comprising a concentric line having the inner conductor coupled to said cathode conductor and the outer conductor coupled to said grid, and a tunable coaxial line connected to said resonators for controlling the feedback between said resonators.

5. An electron discharge device having an envelope containing a cathode for supplying electrons, a control grid electrode and another electrode within said envelope in the order named, conducting and supporting means for said cathode extending through said envelope, said control grid electrode shielding said cathode and provided with conducting and supporting means having a conducting surface external of said envelope, a cavity resonator surrounding said envelope and coupled between said control grid electrode and said other electrode and having one wall contacting said grid electrode conducting and supporting means, said conducting and supporting means forming a continuation of the wall of said cavity resonator, and a control grid electrodecathode circuit comprising a cavity resonator coupled between said cathode and control grid electrode, and means connected between said resonators for controlling the energy transferred from one cavity resonator to the other cavity resonator,

said other electrode and said ,cavity resonator coupled thereto being insulatingly separated to permit difierent direct voltages to be applied to said other electrode and to the cavity resonator coupled to said other electrode.

6. An electron discharge device having an envelope, a cathode, control grid electrode, and another electrode within said envelope and positioned in the order named, and conducting means for said cathode extending through said envelope, said control grid electrode being conductively connected to a conducting means outside said envelope, a cavity resonator coupled between said control grid electrode and said other electrode, and a cathode-control grid electrode cavity resonator coupled between said cathode and control grid electrode, and including a tubular member coaxial with said control grid electrode and electrically coupled to said conducting means outside said envelope, said last conducting means forming a continuation of the wall of said cathodecontrol grid electrode cavity resonator, said last cavity resonator including a conducting member coaxial with and inside said tubular member and electrically coupled to said cathode conducting means, and conducting means positioned between said tubular member and conducting member and movable longitudinally thereof for tuning said cathode-control grid electrode cavity resonator.

7. An electron discharge device having an envelope containing a cathode for supplying electrons, a control grid electrode and another electrode in the order named, a conductor for said cathode extending through said envelope, said control grid electrode shielding said cathode and having conducting and supporting mean having a conducting surface external of the envelope, a cavity resonator surrounding said envelope and electrically connected to the control grid conducting and supporting means and provided with an element of extended area, and means connected to said other electrode and extending outside of the envelope of said tube and capacity coupled to the member of extended area of said cavity resonator, and aninput resonator connected between the cathode and grid electrode and comprising a coaxial line cavity resonator electrically connected at one end to said grid conducting and supporting means and capacitively coupled at its other end to said cathode.

8. An electron discharge device having an envelope, a cathode, control grid electrode and other electrode within said envelope andpositioned in the order named, a lead for said cathode, said control grid electrode enclosing said cathode and having a conducting and supporting means communicating with the outside of said envelope, a cavity resonator surrounding said envelope and coupled between said control grid electrode and said other electrode, and including a member coaxial with said control grid electrode and electrically coupled to said control grid electrode conducting and supporting means on the outside of said envelope, said control grid electrode conducting and supporting means forming a continuation of the wall of said cavity resonator, a cathode control grid electrode-cavity resonator coupled between said cathode and grid, and means coupled between said resonators for controlling the energy transfer between said cavity resonator.

9. An electron discharge device having an envelope, a cathode, control electrode and another electrode within said envelope and positioned in the order named, conducting means for said cathode extending through said envelope, said control electrode being conductively connected to conducting means extending to the outside of said envelope, a cavity resonator coupled between said control electrode and other electrode, and a cavity resonator coupled between said cathode and control electrode and including a tubular member coaxial with said control electrode-and electrically coupled to said control electrode conducting means, said control electrode conducting means forming a continuation of the wall of the cathode-control electrode-cavity resonator, said last cavity resonator including a conducting member coaxial with and inside said tubular member and electrically coupled to said cathode conducting means, and an adjustable transmission line coupling said cavity resonators together.

ANDREW V. HAEFF.

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