US2803782A - Triode thermionic tube - Google Patents

Description

. A118- 20, 1957 vGL DIEMER V2,803,782

TRIODE THERMIONIC TUBE Filed Aug. 14. 195] RSheeMf-Sheet 1 mvENToR Gesinus em r By QWI* nl 20,1957 G. Dir-:MER 2,803,782 `Tmoms manicure TUBE;

piled Aug. 14. 19g-z INYENTOR Gesinus Diem r B y Agen United States Patent @hte ZABJSZ Patented Aug. 20, 1957 TRIODE THERMIUNIC TUBE Gesnus Diemer, Eindhoven, Netherlands, assignor, by

mesne assignments, to North American Philips Company, Inc., New York, N. Y., a corporation of Delaware Application August 14, 1951, Serial No. 241,796

Claims priority, application Netherlrunuls` September 22, 1950 2 Claims. (Cl. 315-40) This invention relates to apparatus for operating at very high radio frequencies (1000 mc./s. and higher) comprising a triode having hat electrodes, wherein the grid consists of a plurality of parallel wires stretched over a hole provided in a conductive ring which is supported by a conductive disc sealed into the wall of the tube and separating the cathode space from the anode space. Furthermore the invention relates to triode tubes intended for such device.

It is known that in devices of the aforesaid type, the magnetic eld of the grid wires gives rise to a reaction or feedback from the anode space to the cathode space.

Furthermore it is known that the self-inductance of the grid supply lead causes a similar reaction in a tube of rather classical constructie It is held that this reaction involves an apparent increase in an anode-cathode capacity.

The present invention has for its object to utilize to advantage the aforesaid reaction due to self-inductance of the grid wires.

According to the invention, in apparatus for operating at very high radio frequencies comprising a triode having flat electrodes, wherein the grid consists of `a plurality of thin parallel wires stretched over a hole provided in a conductive ring which is supported by a conductive disc sealed into the wall of the tube and separating the cathode space from the anode space, the self-inductance of the grid wires is such that the resultant reactionor feedback from the anode space to the cathode space entirely or substantially entirely corrects for the reaction due to the static capacity between the anode and cathode. In order to ensure optimum compensation as a result of the self-inductance of the grid wires, the device is adjusted in a range of frequencies about the angular frequency C.. w* omega,

In a particular embodiment of the invention an inductanceand capacity-free resistor having a value of 1 wzcagcgcg is connected between the anode and the cathode.

It has, in effect, both theoretically and experimentally been found that the anode-cathode capacity approximately has the apparent Value of Q Mgsnc) is connected in parallel with the said apparent capacity. For the self-inductance of the grid wires practically only that part is of importance which is located between the point of attachment of the wires and their portion partaking in the discharge, the same holding for the resistance.

It appears that if CM CGECKCLI the reaction from the anode space to the cathode space is a minimum and may be designated by the aforesaid negative resistance, which may consequently be compensated by a positive resistance.

lf the device is to be used in a large frequency range, more particularly above 5000 mc./s., it is advisable that the length of the grid Wires between the ring and their portion partaking in the discharge should be reduced as much as possible. This is ensured by mounting the grid ring such that its non wire-stretched side faces the anode and by providing that the hole therein is not much larger than is necessary for the discharge, i. e. not more than 0.3 mm. at both sides, and by bevelling the hole in the ring.

In order that the invention may be readily carried into effect, an example will now be described in detail with reference to the accompanying drawings, in which:

Fig. 1 represents an electric discharge tube for use in a device according to the invention,

Fig. 2 shows the stretched grid ring for this discharge tube,

Fig. 3 represents a measuring arrangement with this tube, l

Figs. 4 and 5 show the measuring results obtained with this tube, and

Fig. 6 represents a bevelled grid ring for this tube.

`In Figs. l and 2, the reference numerals, 1, 2 and 3 designate three chrome iron discs which, jointly with the substantially cylindrical glass parts 4, 5 and 6, constitute the discharge tube. Into a disc 1 is screwed a cathode ring 7 to which a molybdenum cylinder 9 is secured with the aid of a thin tantalum foil 8. The cylinder contains a heater coil 10 and has welded to it a porous tungsten cap 11 containing barium strontium oxide 12. The cathode ring is provided with three gauze-covered holes 13 and is held in place by means of three bolts 14 comprising clamping rings.

`A grid ring 16 with wires 17 stretched thereon and soldered thereto is pressed against grid ring 2 by means of three bolts with clamping rings 15. A copper anode 18 is soldered to the chrome iron disc 3.

Fig. 3 shows how the tube depicted in Fig. l is arranged in a measuring arrangement constituted by two elongated Wave guides 19 and 20 having a common wall 21. Four pistons 22 provide for the tuning of the wave guides. The grid disc is clamped in the common wall 21 by a ring of resilient bent tags. A mica ring 23 is provided for insulation between the cathode disc and the lower Wall of the wave guide 19, a mica ring 24 for insulation being provided between the clamping means for the anode head and the upper wall of wave guide 2t). The end of the coaxial supply cable 25 extends into wave guide 19. A crystal detector 27 is mounted in wave guide 20 so as to be insulated therefrom by a mica bush 26. lf a signal is sent into the lower wave guide through a cable 25, this signal is detected to a greater or less degree in the crystal detector 27 in accordance with the reaction from the anode space to the cathode space. .Thus the reaction from the cathode space to the anode space is actually measured, but this reaction is equal to that from the anode space to the cathode space. The measurements are invariably effected at such tube voltages that the cathode, when heated, does not carry current. In the case of a cold cathode this additional step is not necessary. The higher the voltage required to be applied through cable 25 to the lower cavity resonator to detect a particular signal in the crystal detector 27, the lower the reaction between anode space and cathode space.

Y In Fig. 4, this signal is plotted in an arbitrary measure along a vertical axis as a function of the frequency in m.c/s. and more particularly in curve A for a cold tube and in curve B for a cathode temperature of 600 C. For controlling purposes the curve C is shown with removed grid and a conductive rod provided between anode and cathode, so that the input electrode and the output electrode 'are directly connected through a short-circuit.

Fig. shows the same for another tube, in curve D for a tube with a cold cathode and in curve E for a cathode temperature of 1000 C., curve F representing the control with the aforesaid short-circuit between inlet and outlet.

From these curves it is evident that the voltage required atl inlet asafunction of the frequency has a maximum, so that in this case the reaction as a function of the frequency is a minimum. from minimum reaction towards lower frequencies at higher cathode temperatures appears from the drawing.

This also ts with the expectations, since theV arrange'- ment is such that the grid-cathode capacity increases upon thermal expansion of the cathode. The structural details of the measured tubes are as follows: the hole in the grid'ring is 4 mms. square, the molybdenum ring itself being 0.5 mm. thick. The cathode and the anode have a diameter of 3 mms. The tungsten grid wires are 10a thick and gold-plated to a thickness of 0.1M. The distance of the cathode from the centre of the grid wires isl40,u., this being 2501i for the anode. In the cold state Ofthe tube the grid-cathode capacity is 1.1 ggf., it being 1.5 auf. at a cathode temperature of 1050 C. The gridaiiode capacity is 0.45 auf. and the cathode-anode capacity amounts to 15 X 10-3 auf.

If for the self-inductance of the grid wires only the length between the ring and the active part thereof is taken and assuming them to be equispaced from the anode andfrom the cathode by this length, it is found that Lg` 0.10 10"9 henries. By means of the aforesaid expression it can be calculated that the frequency of minimum reaction with a cold and hot cathode is 2900 and 2500 m.c/S. respectively which roughly fits with the curves measured.

The triode shown in Fig. 6 differs from that shown in Fig. l only in that the side of the grid ring 16 where the wiresv are stretched on it is remote from the anode. The circular hole in the ring has a bevelled edge 28 and is only slightly larger that the anode, viz. 0.3 to 0.4 mm. in diameter.

What I claim is:

1. An electron discharge device adapted for operation at a given frequency above 1000 mc./s. comprising an envelop'e, a cathode within said envelope having a at electron emissive surface which includes a porous tungsten cap containing barium strontium oxide and which provides an electron beam of high current density; an anode within said envelope having a flat electron receiving surface disposed opposite said electron emissive surface; a conductive disc having an aperture therein for the passage of said electron beam interposed between said electron-emissive surface and said electron receiving surface, said disc being sealed into the wall of the envelope; a conductive ring supported by said disc; and a plurality of thin spaced parallel wires stretched over the ring constituting a grid, said wireshaving a length and spacing at which that part Furthermore, the frequency shiftv of said wires between said ring and said electron beam has a given value of self-inductance Lg, said wires defining with the emitting surface and the receiving surface a cathode space and an anode space, respectively, the self-inductance Lg of said wires having a value at which the coupling between the anode space and the cathode space due to the self-inductance Lg of the wires substantially compensates for the feedback due to static capacity between the electron emissive surface and the electron receiving surface at said given frequency in a range about an angular frequency which lies Cac denoting static anode-cathode capacity, Cag denoting static anode-grid capacity, and Cgc denoting static cathodegrid capacity.

2. An electron discharge device adapted for operation at a given frequency above 1000 mc./s. comprising an en disc being sealed into the wall of the envelope; a conducf tive ring supported by said disc; a plurality of spaced thin parallel wires stretched over the ring constituting a grid, said wires having a length and spacing at which that part of said wires between said ring and said electron beam has a given value of self-inductance Lg, said wires deiining with the emitting surface and the receiving surface a cathode space and an anode space, respectively, the selfinductance Lg of said Wires having a value at which the coupling between the anode space and the cathode space due to the self-inductance Lg of the Wires substantially corrects compensates for the feedback due to static capacity between the electron emissive surface and the electron receiving surface at said given frequency, which lies in a range of frequencies about an angular frequency Cac Y VC..0..L.

v References Cited in the le of this patent UNITED STATES PATENTS 1,981,058 Marconi et al Nov. 20, 1934 2,025,075 Samuel Dec. 24, 1935 2,037,231 Heintz Apr. 14, 1936 2,413,689 Clark et al. Jan. 7, 1947 2,416,565 Beggs Feb. 25, 1947 2,451,249 Smith et al. Oct. l2, 1948 2,459,859 Weston Jan. 25, 1949 2,461,303 Watson Feb. 8, 1949 2,624,100 Foulkes Jan. 6, 1953

Claims (1)

1. AN ELECTRON DISCHARGE DEVICE ADAPTED FOR OPERATION AT A GIVEN FREQUENCY ABOVE 1000 MC./S. COMPRISING AN ENVELOPE, A CATHODE WITHIN SAID ENVELOPE HAVING A FLAT ELECTRON EMISSIVE SURFACE WHICH INCLUDES A POROUS TUNGSTEN CAP CONTAINING BARIUM STRONTIUM OXIDE AND WHICH PROVIDES AN ELECTRON BEAM OF HIGH CURRENT DENSITY; AN ANODE WITHIN SAID ENVELOPE HAVING A FLAT ELECTRON RECEIVING SURFACE DISPOSED OPPOSITE SAID ELECTRON EMISSIVE SURFACE; A CONDUCTIVE DISC HAVING AN APERTURE THEREIN FOR THE PASSAGE OF SAID ELECTRON BEAM INTERPOSED BETWEEN SAID ELECTRON-EMISSIVE SURFACE AND SAID ELECTRON RECEIVING SURFACE, SAID DISC BEING SEALED INTO THE WALL OF THE ENVELOPE; A CONDUCTIVE RING SUPPORTED BY SAID DISC; AND A PLURALITY OF THIN SPACED PARALLEL WIRES STRETCHED OVER THE RING CONSTITUTING A GRID, SAID WIRES HAVING A LENGTH AND SPACING AT WHICH THAT PART OF SAID WIRES BETWEEN SAID RING AND SAID ELECTRON BEAM HAS A GIVEN VALUE OF SELF-INDUCTANCE LG, SAID WIRES DEFINING WITH THE EMITTING SURFACE AND THE RECEIVING SURFACE A CATHODE SPACE AND AN ANODE SPACE, RESPECTIVELY, THE SELF-IN-

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