US2442576A - Mixing tube - Google Patents

Description

Patented June l, 1948 s'r'res PATENT orties MIXING TUBE Application April 20, 1943, Serial No. 483,768 In the Netherlands August 5, 1939 Section 1, Public Law 690, August 8, 1946 Patent expires August 5, 1959 4 claims. l

This invention relates to an electric discharge tube comprising a cathode, an anode and at least ve intermediate electrodes, i. e. to a so-called pentagrid or octode. In addition the invention concerns a mixing circuit including such a tube.

Pentagridand octode-constructions have come to be known wherein all electrodes placed between cathode` and anode are constructed as grids; in this case the rst two electrodes next to the cathode may act as oscillator electrodes, the third one as a screen-grid, the fourth one as an input control grid, while the ith and sixth intermediate electrodes are then used as screen and suppressor grids respectively. The functions may also be divided in another way and this in such manner that of the first four grids next to the cathode the rst one is used as an input ccntrol grid, the second one as a screen grid and the third and fourth ones as oscillator electrodes. If the oscillator electrodes are nearer the cathode than the input control grid it is furthermore known to omit the first screen grid and to use the oscillator anode as a screen grid at the same time. Again when using two oscillator electrodes, it has been suggested to make the oscillator anode consist only of a few rods or plates.

According to another well known construction of a pentagrid or octode the electrons issuing from the cathode are formed into a number oi beams; in this case various variations are possible. One may, for instance, make use of two beams issuing on either side of a flat cathode; however it has also been suggested to form the electrons into four beams which remain sharply separated by a denite configuration of the electrodes. In this case a grid common to all electrons directly surrounds the cathode, then two beams serve exclusively for the oscillator part and two other beams for the mixing part.

Both forms oi construction of these tubes set out above have the same objection, that the electronic stream issuing from the cathode cannot be completely used both ior the mixing part and for the oscillator part. In the first mentioned. case, i. e. when all electrodes situated between the cathode and the anode are shaped as grids, a part of the cathode stream is lost as a screen grid stream because particularly the iirst screen grid attracts a fair amount of current. In the second case when the electrons are concentrated in beams either the cathode surface is insufficiently utilized in the case of two beams, or, in the case of four beams, the electronic stream issuing from the cathode is divided between the two functions of the tube. Due to this the mutual conductance viz. both that of the oscillator and that of the mixing part are smaller than is desirable in many cases.

This diiiiculty can be largely met whenv making use of a discharge tube according to the present invention, which tube comprises a cathode, an anode and at least five intermediate electrodes of which, moving from the cathode onwards, the iirst, fourth, ith and, if present, the sixth one are constructed as grids, the third electrode only consisting of some rods or plates, and the second electrode being built up from or at least comprising a number of rods, plates, or sirnilarmembers, which bring about uniform spreading of the electrons past this electrode.

In such a tube the above mentioned drawback can be avoided for the greaterI part and, in addition, a number of other advantages are obtained when making use of these mixing tubes.

The rst two electrodes next to the cathode together with the cathode constitute the local oscillator; in this case the second electrode has a very extensive function; it serves as an oscillator anode and as a result of its particular shape it produces a certain concentration into a beam and uniform spreading of the electrons thus prometing anV increase in mutual conductance of the mixing part. Moreover, this electrode is so shaped that it attracts a fairly large number of electrons so that this tube has a high oscillator` slope; in addition, this electrode provides for a suicient quantity of electrons for the virtual cathode to be formed before the input control grid. Electrons returning from this virtual electrode also impinge on the parts oi the electrode described above which also promotes the oscillator slope.

InV order to perform these functions the electrode described above may have various shapes; it may, for instance, consist of a number oi screen plates secured to rods, of a number of rods say four, which are arranged close together in pairs to form a rectangle so as to permit the issue oi two spread beams. Finally it is also possible to design this electrode as a grid which must then be wound fairly widely on a number of rods which themselves involve a certain concentration into a beam and spreading. At any rate this electrode must be constructed so as to ensure this spreading, and at the same time there must be sufficient elements to feed the virtual cathode and to obtain a high oscillator slope.

An increase in mutual conductance of the mixing part is promoted by the presence of the third electrode succeeding the cathode which electrode consists of only some rods or plates; since this electrode does not comprise grid wires, deflection Y in the paths of the electrons is avoided and ayer-y steep slope of the mixing part can be obtained. Furthermore this third electrodeis provided in order to make up for the high'capacity between the second and fourth electrode; to .this end-this third auxiliary electrode is preferably connected, either inside or outside the tube directly, to -the first grid. Although this does not yield a. de-

crease in capacity between the second and fourth auxiliary electrode, compensation of both capacities is ensured by an increase in capacity between the first and fourth electrodes; same time this makes up for the induction eiect on the fourth auxiliary electrode. Finally ka -considerable saving in energy is obtained since the third auxiliary electrode has no wires.

Brieiiy summarizing, when using a tube according to the present invention, the advantages which the known constructions have are each individually utilized in combination, the obtainable slopes being steeper than in the known constructions and the tube according to the invention permitting simple and economical mass production.

The invention will be more clearly understood by reference to the accompanying drawing wherein Figure l diagrammatically represents the electrodes of an electric discharge tube according to the present invention, Figure 2 representing a circuit arrangement which comprises such a tube.

In Figure 1 an electron discharge devise has an envelope Iil containing a cathode I, for instance a directly heated cathode consisting of a number of wire parts. Around this cathode there are successively arranged a grid 2 having grid side rods 2", an electrode consisting of rods 3 and plates 4, an electrode consisting of rods 5, a grid E, grids 'I and 8 and-an anode 9. As indicated in the drawing by lines I and II the electrodes 5 and 8 are directly connected to the grid 2 and the cathode I respectively. As has already been set out, however, this connection need not take place within the tube, since it may also be established on the exterior thereof. Furthermore, for the attainment of the results by means of the tube according to the present invention it is not necessary to provide a grib 8 (suppressor grid) in the tube.

In the circuit arrangement represented in Figure 2 the reference numbers I, 2, 3, 4, 5, 6, 'I, 8 and S designate'the sameV electrodes as in Figure l, the connections IQ and II being also represented in Figure 2. The incoming oscillations are supplied through a transformer I2 to a circuit I3 inserted in the lead for the control grid 6. The local oscillations are produced in the tuned oscillator circuit I 4 which is connected to the first grid 2 through a condenser I5 and resistance I6. The electrodes 3 and 2 together with the cathode i constitute the local oscillator. Furthermore, the anode has. connected: to it an output circuit II which is coupled with anxinter- At the 4 mediate frequency amplifier (not represented) through the intermediary of transformer I8.

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 illustrated or the use indicated, but that many variations may be made in the particular structure used and the Y purpose for which it is employed without departing from the scope of our invention as set forth inthe appended claims.

What I claim as new is:

1. An electron discharge device having a cathode surrounded by a control grid and an anode, said control grid being provided with a single pair of side rods whereby electrons from said cathode-flow from said cathods in only two opposed streams, a pair of oppositely disposed electrodes of .larger area than said side rods positioned on opposite sides of the cathode and between the side rods of the control grid and anode and in the plane of the side rods, and a control electrode surrounding said cathode, grid and oppositely disposed electrodes, and an auxiliary electrode positioned between each of the oppositely disposed electrodes and the control electrode and adapted to be maintained at a potential not greater than that of the rst control grid during operation of the electron discharge device.

2. An electron discharge device having a cathode surrounded by a first control grid, said control grid being provided with a single pair of side rods whereby electrons from said cathode iiow from said cathode in only two opposed streams, a second control grid having side Vrods lying in the plane of the side rods of the first control grid, and an anode, a pair of oppositely disposed anode electrodes positioned between the side rods of said control grids and the iirst and second control grids, said anode electrodes being of larger area than the side rods of said first control grid, and auxiliary electrodes positioned between the anode electrodes and the second control grid and electrically connected to the rst control grid.

3. An electron discharge device having a cathode, a control electrode surrounding said cathode and having only a single pair of oppositely disposed side rods whereby elec-trons from Y said cathode flow from said cathode in only two opposed streams of electrons, a second control electrode surrounding the rst control electrode and provided with oppositely disposed side rods lying in the same plane as the side rods of the rst control electrode, a screen grid, and an anode surrounding said cathode and control electrodes, oscillator anode electrodes positioned between the rst and second control electrodes at said side rods, said oscillator anode electrodes being of larger area than said side rods and auxiliary electrodes positioned between the oscillator anode electrodes and said second control electrode and lying in the plane of said side rods.

4. An electron discharge device having a cathode comprising a plurality of filaments lying in acommon plane, a pair of control grids surrounding said cathode, each of said grids having only a single pair of oppositely disposed side rods, said side rods lying in the plane of the cathode laments, whereby electrons from said cathode ow from said cathode in only two opposed streams of electrons, an anode surrounding said cathode and control grids, oscillator anode elecelectrodes being of larger area. than said side rods and an electrical connection between the irst control grid and said auxiliary electrodes.

GERRIT HENDRIK PETRUS AIMA. HENNY COHN. HENDRICUS JOHANNES LANDSBERGEN.

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

UNITED STATES PATENTS Number Name Date Jonker Oct. 25, 1938 Erichsen Nov. 29, 1938 Jonker June 4, 1940 Overbeek Dec. 17, 1940 Steimel Jan. 14, 1941 Cohn Aug. 3, 1943

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