US2342987A

US2342987A - Frequency changing apparatus

Info

Publication number: US2342987A
Application number: US443154A
Authority: US
Inventors: Francois Joseph Gerard V Bosch
Original assignee: VACUUM SCIENCE PRODUCTS Ltd
Current assignee: VACUUM SCIENCE PRODUCTS Ltd; VACUUM-SCIENCE PRODUCTS Ltd
Priority date: 1939-05-25
Filing date: 1942-05-15
Publication date: 1944-02-29
Anticipated expiration: 1961-02-28
Also published as: FR865749A

Description

TOP

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Patented Feb. 29, 1944 FREQUENCY CHAN GING APPARATUS Francois Joseph Gerard van den Bosch, East Croydon, England, assignor to Vacuum-Science Products Limited, London, England, a British ompany Original application May 20, 1940, Serial No. 336,308. Divided and this application May 15, 1942, Serial No. 443,154. In Great Britain May 4 Claims. (01. 250-20) This application is a division of my co-pending United States application No. 336,308, filed May 20, 1940, Patent No. 2,295,919, granted September 15, 1942, for improvements in Electron discharge devices.

This invention relates to electron discharge devices adapted to operate as frequency-changing apparatus, and of the kind comprising an electrode assembly having one or more electrodes employed for the purpose of producing a secondary electron emission inorder to obtain electron multiplication. Usually, such electron multiplication assembly comprises a primary cathode, one or more secondary cathodes and a collector enclosed in an envelope and so arranged that electrons emitted by the primary cathode are caused to impinge on the secondary cathode and liberate other electrons which impinge on the next secondary cathode, when more than one, and so on in succession to the collector.

According to the present invention a homodyne or frequency-changing apparatus comprises an electron discharge device having a thermionic cathode structure, two electrode assemblages associated with said structure, one of which is adapted to eiTect electron multiplication, means-associated with the other electrode assemblage for generating a local oscillation, means for applying said oscillations to the first said electrode assemblage, and means for applying a received signal also to the electrode assemblage whereby the received signal and local oscillations are mixed and amplified by the electron multiplication. The first said electrode assemblage includes one or more secondary cathodes, two control electrodes and a collector anode, and the local oscillations are applied to one of said electrodes, while the output from a radio receiver is connected to the other control electrode.

The following is a'desc'ription of two forms of electron-discharge device suitable for use in the invention, and the electric circuit to be employed therewith, reference being made to the accompanying drawing, in which- Figure 1 is a section through the electron-discharge device, showing the disposition of the various electrodes; I

Figure 2 is a diagrammatic view showing the manner in which the electrodes are connected with the external circuits, and

Figure 3 shows an alternative form of thermionic cathode structure.

Referring to Figure 1 of the drawing, the 9311 119919 ll9ll$ comp i es e 1 2 953 1 tu I? 11? ing an enlarged disc-like part II at one end. The outer surface of this disc-like part is provided with a coating 28 freely emitting electrons, such as a coating of barium oxide or strontium oxide, and constitutes the cathode element of the electron multiplier assembly. The electron emission from this cathode element is controlled by two grid electrodes l2 and I3 between'which there is provided another electrode M in the form of aplate with a single aperture through which the electrons are directed towards a secondary cathode I5. The secondary cathode I5 is an apertured electrode consisting ofa perforated plate, for instance, as described in the specification of United States application No. 276,883, filed June 1, 1939, Patent No. 2,254,- 128 granted August 26, 1941, but it may alternatively be constituted by a wire grid or mesh. Other secondary cathodes similar to the secondary cathode 15 are provided, as indicated at l6, l1, l8 and IS with a final secondary cathode 29 of disc form and a collector electrode 2| in the form of a grid interposed between the secondary cathodes l9 and 2B. The secondary cathodes I8, l1, l8 and H] are each provided with an auxiliary electrode 22 to the front, as described in the specification of United States application No. 326,813, filed March 29, 1940,

' Patent No. 2,285,848, granted June 9, 1942, and

connected electrically to the secondary cathode.

The tube I0 also has a second emissive coating 29 surrounded by a cylindrical grid electrode 23 and a cylindrical anode 24 together constituting a thermionic triode.

' A heating element 9 is provided within the tube 10 for indirectly heating the tube and thus the cathode elements provided by the emissive coatings on the tube. It is convenient to operate the cathode element providing the emission for electron multiplication at a lower tempera- I ture than the other cathode element, so that the heater preferably does not extend fully to the disc-like part II. For instance, the heater may be arranged to lie within the tube 10 only adjacent that part which has the emissive coating for the triode assembly.

Around this triode assembly there is provided a cylindrical screen '25 formed of a wire grid or mesh. This screen has an end member 26 having an opening 21 in which the disc-like cathode element H of the multiplier assembly is located. The disc-like cathode element Il may be a close fit in the opening 21 and the screen is electrical- 1:! connected t t t mate i! 9? the c thod trut ture. The cylindrical screen 25 may be formed by a metal tube instead of a grid or mesh.

One application of this electron-discharge de vice is as in frequency-changing apparatus, for instance in a radio receiver of the super-heterodyne type. In this case the thermionic triode assembly is connected with an external circuit indicated at 30 in known manner for producing,

These local with the triode, local oscillations. oscillations are fed to the control electrode H! of the electron multiplier assembly and to the control electrode I2 the incoming signals are applied direct or through a preselecting amplifier 3i. A mixing of the local oscillations and applied signals is thus obtained and subsequent amplification is produced through the. several multiplier stages of the electron multiplier assembly. Progressively increasing potentials positive with respect to the cathode element It are applied, to, the accelerator Hi, the secondary cathodes l5, H5, l1, l8, l9 and 2B and the collector 2| through the resistance potentiometer 35. The amplified output at intermediate frequency may thus .be applied to a tuned intermediate frequency circuit 32 from the collector electrode 2| and utilised in any known manner for the reproduction of the signals. Thus, the intermediate frequency signals from the circuits 32 may be applied to a detector 33, followed by an output signal. amplifier 34. The electron-discharge device may similarly be used in a homodyne circuit,

The electron multiplier assembly is provided with operating potentials in known manner in that the secondary cathodes I to 2B and the collector 2| are provided with progressively increasing positive potentials with respect to the cathode tube It and the electrode M is also operated at a potential which is positive with respect to the cathode tube H] but generally lower than that of the first secondary cathode l5.

It is to be understood that the invention is not restricted to the specific construction hereinbefore described with reference to Figure 1. For instance, a plurality of additional electron assemblies may be employed having cathode elements spaced apart lengthwise of the tube Ill and comprising two or more electrodes.

In the modification shown in Figure 3 the tube i0 is extended and has an additional coating 36 freely emitting electrons, around which there is mounted a tubular anode 31, to form a thermionic diode. In this case the cylindrical screen 25 is extended to surround the diode and a metal disc 38 is provided across this screen between the diode assembly and the triode assembly.

In Figure 3 a modification of the metallic end member 26 is shown in which this member is formed with a small opening 21 through which the tube H! passes with the disc-like element ll situated above this end member. In this case a short tube 3.9 is provided around the disclike element l I and is secured to theend member 26 of the screen;

I claim:

1. A homodyne Or frequency changing apparatus comprising an electron discharge device having two electrode assemblages, a primary cathode structure common to both said assemblages, an anode in each said assemblage, so arranged with respect to said cathode as to produce two separate streams of electrons, at least one secondary electron emitting electrode in one of said assemblages, means for applying a potential thereto for producing electron multiplication, an electric circuit coupled with the other assemblage and adapted to generate local oscillation', means for applying said oscillations to the stream of electrons to be multiplied, and means for applying a received signal also to that stream.

2. A homodyne or frequency-changing apparatus comprisingan electron discharge device,

two electrode assemblages, one of which assemblages is adapted to effect electron multiplication and includes two. control electrodes, at least one secondary cathode, and a collector electrode, means associated with the other electrode assemblage for generating local. oscillations, means for applying said oscillations to one ofsaid control electrodes in. the first said assemblage, and means for applying areceived signalto the other electrode of that assemblage.

3. A homodyne or rrequencyrchanging apparatus comprising an electron discharge device having two electrode assemblages, a primary cathode structure common to both said assemblages, an anode in each said assemblage. so arranged with respect to cathode as to produce two separate streams of electrons, one of which assemblages is adapted to effect electron multiplicationin the stream with which it is associated, and includes two control electrodes, at least one secondary cathode and the aforesaid anode, means associated with the other electrode assemblage for generating local oscillations, means for applying said oscillations to one of said control electrodes of the first assemblage, and a radio receiver connected with the other control electrode for applying a received signal thereto.

4. An electron discharge device having two electrode assemblages, a primary cathode structure common to both said assemblages, and an anode in each said. assemblage so arranged with respect to the cathode asto produce two separate streams of electrons, one of which electrode assemblages also includes a secondary cathode, and is adapted to effect electron multiplication, the other of which electrode assemblages is adapted for operation other than by electron multiplication, circuit means connected with the second electrode assemblage for producing therewith a local oscillation, means for feeding the local oscillation to one of the-control electrodes of the first assemblage, means'for applying received signals to the other of said control electrodes, whereby said signals and said local oscillations are combined and amplified in the first said electrode assemblage, and means for extracting an output from the anode of the first said assemblage.

FRANCOIS JOSEPH GERARD VAN DEN bOEZCH.