US2271716A - Electron discharge device - Google Patents

Description

Feb. 3, 1942. B. sALzBERG 2,271,716

ELECTRON DISCHARGE DEVICE Filed Aug. 18, 1939 /NPUT Patented Feb. 3, 1942 ELECTRON DISCHARGE DEVICE Bernard Salzberg, East Orange, N. J., assigner to Radio Corporation of America, a corporation of Delaware Application August 18, 1939, Serial No. 290,719

7 Claims.

My invention relates to electron discharge devices, more particularly to so-called converter or double modulation of the.- electron stream from the cathode to the anode is to producean intermediate frequency voltage in the anode or `output circuit of the tube.

In tubes of this kind, when used at high frequencies, two undesirable effects are encountered; first, even with the signal grid negative an electron current may be observed in the grid circuit; second, the input-shunt resistance of the tube becomes progressively'lower as the frequency is raised to a greater 'extent than when the tube is operated for example as an amplifier. I

These effects are believed to be due to the following phenomenon. When the oscillator or No. 3 grid potential is decreasing some of the electrons which are travelling toward this grid are turned back towards the positive screen or No. 2 I

grid. Depending upon theelectrode spacings, the frequency of operation and the voltages applied to the electrodes, these returning electrons may acquire suicient energy to over-come the retarding field in the space between the No. 1,5

and No. 2 grids and be forced into the No. 1 or signal grid. 'I'his may be vobserved as electron current in the signal gridcircuit. In any event the presence of returned electrons causes high frequency current to be induced in the signal.

grid. In general, such a current will be out of phase with the applied high frequency signal voltage and may be of suflcient magnitude vat high frequencies to result in a decreased input shunt resistance. ing feature in mixer tubes of the type considered. This decreased shunt resistance of course reduces the sensitivity as well as the output of the tube. Hence, it is a principal object of m'y invention to provide an electron discharge device particularly suitable for use as a mixer in converter circuits.

More specifically, it is an object of my invention to provide a tube of the kind described in which the electrical and structural arrangements This appears to be the limitg (Cl. Z50- 175) are such that electrons, which may be vturned back when the voltage on the oscillator grid is decreasing, are prevented from returning to the region of the signal grid.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims, but the invention itself will best be understood by reference to the following description taken in connection with the accompanying drawing in which Figure 1 is a schematic diagram of a tube made according to my invention and its associated circuit, and Figure 2 is a modification of the tube shown in Figure r1 and a circuit to be used with such a tube.

Briefly, in accordance with my invention the cathode and output anodes, preferably of rectangular shape, are spaced laterally with respect to each other and lie in parallel planes. Accelerating electrodes and a solenoid produce combined electrostatic and electromagnetic fields which act to cause electrons to move in arcuateshaped paths from the cathode to the output anode. Electrons are modulated upon leaving the cathode by a grid adjacent the cathode and again modulated by the oscillator grid adjacent the anode on approaching the output anode. Electrons which are repelled by a negative charge on the oscillator grid are again caused to travel arcuate-shaped paths to another electrode spaced laterally with respect to the output anode and collected by this electrode so that they are removed from the electron stream and rendered ineffective to decrease the shunt resistance of the input circuit of the tube.

In Figure 1 the -envelope I0 contains the cathode II, laterally spaced collector electrode or anode I2 and a second collector or waste electrode I3. Electrons leaving the cathode II are made to travel the arcuate paths indicated by means of the electrostatic eld established by accelerating electrodes I4 oppositely disposed to the cathode and anode and by means of a magnetic eld produced by the electromagnetic coil I5 which generates a magnetic field longitudinally of the tube envelope and along the longitudinal axis of the tube, the magnetic field and electric field being transverse to each other. The electrons leaving cathode Il are modulated by the signal control grid II and again modulated by the oscillator grid I1 adjacent the output electrode or anode l2. Screen grids I8 and I 9 may be provided for the first collector or anode I2 and the second collector or waste electrode I3. If it is desired to obtain multiplication action, an auxoscillator frequency by grid I1.

iliary electrode 26 coated with secondary emitting material may be interposed between cathode II and output electrode I2. The input transformer 2I is connected between cathode I'I and signal grid I6, the proper bias for the grid being furnished by a source of voltage 22. The oscillator grid may be connected to a separate and exterior local oscillator 23, a proper biasing Voltage being applied by a source of voltage 24. Although the output circuit, that is the intermediate frequency transformer 26, could be connected between the output electrode I2 and ground or cathode I I, in the particular arrangement shown the intermediate frequency output circuit is connected between the output electrode I2 and electrode I3. The voltage source 21 provides all of the necessary voltages to be applied to the electrodes, the positive voltage on accelerating electrodes I4 being taken off the voltage divider 28 so that the voltage is increased in the direction from cathode to electrode I3.

Electrons leaving the cathode I l are modulated by the signal grid I6, due to the voltage applied to this grid, through input circuit 2l. As electrons enter the electrostatic and electromagnetic fields, the combined eiect of the fields extending between electrodes I4 and electrodes II, 26, I2 and I3 causes the electrons to travel the arcuateshaped paths indicated. Electrons which reach the output electrode I2 are modulated at the Electrons which are repelled by this grid when it swings negative do not return to the signal grid I6, but due to theV combined electrostatic and electromagnetic fields are caused to travel to the electrode I3.

The electrode I3 could be used merely as a waste electrode, but, as described above, is used in combination with electrode I2 and the connected intermediate frequency circuit to obtain the advantages discussed below.

The circuit shown makes it possible to double the intermediate frequency output voltage. The midpoint of the primary of the intermediate frequency transformer 23k is at radio frequency ground. As a result the electrode I2 at maximum radio frequency potential is as much above Vground as the electrode I3 is below ground. The

output voltage, however, is taken across the entire primary and as a result the voltage difference between the two ends of the primary as well as the secondary is twice that which it would be if only one side of the transformer were at ground potential and the other side connected to only one output electrode. With this arrangement, therefore, it is possible for a given tube to deliver twice the output for a given heater power and a given cathode surface making the tube more suitable for higher frequency. The reason for this is that although twice the output is obtained the interelectrode capacities are not doubled but remain those which would exist if only the usual output were obtained and inasmuch as interelectrode capacity is one of the limiting features of high frequency operation, doubling the output, without at the same time increasing the capacity between the electrodes, is quite an advantage. Likewise, the input loading is less for larger power outputs at the higher frequencies. It can also be shown that the carrier voltage does not appear l in the intermediate frequency output which under certain conditions is a desirable characteristic. At the usual frequencies employed for transmission, the transit time of the electrons from grid I1 to the electrode I2 or to the electrode I3 is immaterial since it is comparatively small in comparison to the frequency at which the tube is operating. However, where the transit times are important the tube is so designed that the transit time of the electron from the surface of the grid I1 to electrode vI2 is the same as the transit time from the surface I1 to the electrode I3, so that electrons will arrive in proper phase relationship to obtain a double voltage output in the intermediate frequency transformer.

A modification of the device shown in Figure 1 is shown in Figure 2. Additional electrodes are included and two separate and distinct output circuits are also shown. yIn this embodiment of my invention the envelope 30 contains cathode 3 I, output electrode 32. and collector 33, the accelerating electrodes 34 and solenoid 35 producing the necessary electrostatic and electromagnetic fields for causing electrons to travel to arcuate-shaped paths indicated. The signal grid 36 modulates the electron stream at signal frequency. A screen 31 may also be provided. In this embodiment. at the anode 32 screens y39 and 40 are provided in addition to the oscillator grid 38 and also a suppressor grid 4I, which may be tied back to the cathode. A screen grid 42 is also provided adjacent the collector or second output electrode or anode 33. If desired, secondary emitting electrodes 43 and 44 may be provided to obtain electron multiplication. An input circuit 45 is connected between cathode and signal grid 36, and intermediate frequency output circuit 41 between the source of voltage supply and the output electrode 32. The oscillator voltage is applied through input transformer 46. A second output circuit 48 may be connected between the voltage source and the electrode 33.

Whether electrode 33 is used as an output electrode or merely as a collector, the tube functions to prevent electrons returned by the oscillator grid from returning toward the cathode to produce the undesirable effects discussed above.

While I have indicated the preferred embodiments of my invention of which I am now aware and have also indicated only one specic 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.

. What I claim as new is:

1. An electron discharge device having a cathode for emitting electrons, an anode and a collector electrode spaced laterally of said cathode and in the order named, accelerating electrodes spaced opposite said cathode, anode and collector electrodes respectively for providing an electrostatic iield, and means for generating a magnetic field between said accelerating electrodes and said cathode, anode and the collector electrode, the electrostatic field being transverse to the magnetic field for causing electrons from said cathode to travel successive arcuate-shaped paths from said cathode to said anode and collector electrode, a signal grid adjacent the cathode for modulating the electrons leaving the cathode at signal frequency, and an oscillator grid in the path of the electrons and adjacent the anode for modulating the electrons at a different frequency and varying between positive and negative values. said collector electrode for receiving electrons turned back by the oscillator grid when said oscillator grid becomes negative during operation of said device, and a screen grid between the oscillator grid and anode, and a second screen grid adjacent the collector electrode.

2. An electron discharge device having a cathode for emitting electrons, a secondary emitting electrode, an output electrode, a secondary emitting electrode and a collector electrode spaced laterally of the cathode and of each other and in the order named, accelerating electrodes spaced oppositely of said rst mentioned electrodes and a solenoid for generating a magnetic eld between said accelerating electrodes and the other electrodes and transverse to the electrostatic field between said accelerating electrodes and the other electrodes, a signal grid and a screen grid adjacent the cathode, an oscillator grid and suppressor grid adjacent the output electrode, and -a screen grid between said oscillator and suppressor grids, and a screen grid adjacent said collector electrode.

3. An electron discharge device for use in superheterodyne reception and having a cathode for emitting electrons, an anode and a collector electrode spaced laterally of said cathode and of each other and in the order named along the longitudinal axis of said device, means including magnetic means for causing electrons from said cathode to travel only successive arcuate shaped paths from the said cathode towards said.

anode and then towards said collector electrode, a grid adjacent said cathode for modulating the electrons 1eaving the cathode, and a second grid in the electron path between said first grid and said anode and adjacent the anode for modulating the electrons at a diiferent frequency from said first grid, Said collector electrode for receiving electrons turned back by said second grid during operation of said electron discharge device.

4. An electron discharge device for use in superheterodyne reception and having a cathode for emitting electrons, an anode and a collector electrode spaced laterally of said cathode and of each other and in the order named along the longitudinal axis of said device, means including magnetic means for causing the electrons from said cathode to travel successive arcuatedshaped paths from said cathode towards said anode and then towards said collector electrode, a first control electrode adjacent the cathode for modulating the electrons leaving the cathode,

and a second control electrode in the electron path between the first control electrode and said anode and adjacent the anode for modulating the electrons at a frequency different from the first control electrode, said collector electrode for receiving electrons turned back by the second control electrode during operation of said device, and a screen grid between the anode and the second control electrode adjacent the anode; and a second screen grid adjacent the collector electrode.

5. An electron discharge device for use in superheterodyne reception having a cathode for emitting electrons, an anode and a collector electrode spaced laterally of said cathode and in the order named along the longitudinal axis of said device, means including magnetic means for causing electrons from said cathode to travel only successive arcuate shaped paths from said cathode towards said anode and then towards said collector electrode. a signal grid adjacent the cathode for modulating at a signal frequency the electrons leaving the cathode, and an oscillator grid in the electron path between said signal grid and said anode and adjacent the anode for modulating the electrons at an alternating voltage having negative and positive values with respect to the cathode voltage during operation of the device, a screen grid between the anode and the oscillator grid, said collector electrode for receiving substantially only electrons repelled by the oscillator grid when the voltage on the oscillator grid has a negative value during operation of said device.

6. An electron discharge device for use in superheterodyne reception and having a cathode for emitting electrons, an anode and a collector electrode spaced laterally of said cathode and in the order named along the longitudinal axis of said device, accelerating electrodes spaced opposite said cathode, anode and collector electrode on the opposite side of said longitudinal axis and means for generating a magnetic field between said collector electrodes and said cathode and the accelerating electrodes, the electrostatic eld between the accelerating electrodes, the cathode, anode andy collector electrodes being transverse to the magnetic field for causing electrons from said cathode to travel successive arcuate shaped paths from said c-athode to said anode and collector electrode, a signal grid adjacent the cathode for modulating the electrons leaving the cathode at signal frequency, and an oscillator grid in the path of the electrons between the cathode and the anode and adjacent the anode for modulating the electrons at a different frequency, and a screen grid between said oscillator grid and said anode, said collector electrode for receiving substantially only electrons turned back by the oscillator grid during operation of said device.

'7. An electron discharge device for use in superheterodyne reception and having a cathode for emitting electrons, an anode and a collector electrode spaced laterally of said cathode and in the order named on one side of and along the longitudinal axis of said device, accelerating electrodes spaced opposite said cathode and anode and collector electrode on the oppositeside of said longitudinal axis for providing an electrostatic field and means for generating a magnetic field between said accelerating electrodes and said cathode, anode and the collector electrode, the electrostatic field between the accelerating electrodes, the cathode, anode and the collector electrode being transverse to the magnetic field for causing electrons from said cathode to travel successive arcuate shaped paths from said cathode to said anode and collector electrode, the signal grid adjacent the cathode for modulating electrons leaving the cathode at signal frequency and an oscillator grid in the path of the electrons betweensaid signal grid and said anode and adjacent the anode for modulating the electrons at a different frequency, said collector electrode for receiving electrons turned back by the oscillator grid during operating of said device, and a secondary emitting electrode positioned between the cathode and the anode for electron multiplication, and a screen grid between the oscillator grid and the anode,

BERNARD SALZBERG,

Images