US2042571A - Signal translating and modulating system - Google Patents

Description

June 2, 1936. H. A. WHEELER` SIGNAL TRANSLATING' AND MODULATING SYSTEM Filed March 27, 1935 ATTORNEY.

www' v" UNITED STATES PATENT OFFICE SIGNAL TRANSLATING AND MODULATING SYSTEM Harold A. Wheeler, Great Neck, N. Y., assigner to Hazeltine Corporation, a corporation of Delaware Application March 27, 1935, Serial No. 13,227

21 Claims. (Cl. Z50-20) i My invention relates to signal-translating and In the system described above, there is a certain -modulating systems, and more particularly to amount of unavoidable capacitive coupling be- :g such systems including a vacuum tube providedj tween each of the several electrodes upon which with a virtual cathode; that is, a secondary source,l is impressed a voltage and all of the other elecof electrons controllable independently of thef trodes, this coupling being eiective to transfer electron stream from the main cathode. g currents from any given electrode to the circuits The invention is directed specically to an arassociated with the other electrodes. These currangement for neutralizing, or compensating for, rents develop in such circuits voltages which apany regenerative or degenerative feedback effect pear on their associated electrodes, and which l0 upon a signal-translating or -amplifying control are dependent upon the impedances of the cir- 10 electrode of another electrode or electrodes, incuits at the frequency of the voltage impressed cluded in the same vacuum tube, and their conupon the given electrode. These induced voltages nected circuits, such other electrodes usually coon the other electrodes of the vacuum tube modioperating in the formation of the virtual cathfy the effect of the given electrode upon the relo ode; and for neutralizing or compensating for'any sultant electron current flowing to the anode of 15 leInOdulating 0I' demOdulating eiect 0f the Signaithe vacuum tube and its associated output cirtranslating or -amplifying control electrode and cuit. The effect of these induced voltages may its connected circuit upon the modulating action be either aiding or opposing, depending upon in the same vacuum tube. whether the circuits in which they appear are in- It has been proposed heretofore to utilize as a ductively or capacitively reactive at the fre- 20 modulator of a signal-translating system, a multiqueney in question, electrode vacuum tube including means for form- The capacitive couplings between the several ine a virtual cathode or secondary source of electrodes in e multi-electrode vacuum tube of electrons. Such a virtual cathode may be estabthe type described above, provided with a virtual lished by a pair of closely spaced electrodes, the cathode, is mede up of two components, the mst 25 one nearer the CathOde being maintained at a being the usual geometrical capacitance, which DCSitiVe potential With respect theretO and the is dependent primarily upon the physical relationother at a nEgatiVe pOtential With leSpeCt thel'eship of the electrodes within the vacuum tube. to. The latter electrode is effective to retard The second Component, which is peculiar to this the iiow of electrons beyond the first electrode type 0f vacuum tube including a, virtua1 cathode, 30 and to form a cloud or mass of slow-moving elecmay be termed a, space-Charge coupung and is trcns having characteristics very similar to those due to variations or fluctuations in the space of the actual cathode. The intensity of the vir- Charge of the mass or Cloud of electrons consti.. tual cathode may be @Ont/rolled by an emiSSiOn tuting the virtual cathode and positioned between control electrode interposed between the virtual the vjrtua1cath0def0rming e1ectr0de5 It wm 35 and actual cathodeS. The eleCtiOn Stream from be understood that variations in the space charge this virtual cathode may be C0nt1011ed by a SUitcapacitively induce displacement currents in the able electrode disposed between the virtual cath- Circuits of any electrodes Subject to the electro. V:ode and an output electrode further from they; static eld of the space Charge.

actual cathode. A signal-translating and -mOd- However, as between certain of the electrodes ulating system utilizing a Vacuum tube 0f met; of a multi-electrode vacuum tube, the capacitive i type J'llSt described is disclosed and Claimed mii coupling is negligible, either because they are re1- U' s' Letters Patent No' ,1958027 granted May atively remote or because of their electrostatic 4, 81934 upon my applica/mon' isolation by means of an interposed auxiliary 45 The aldantages of such a' System aie set forth screen electrode; for example, a screen adjacent m tietatnolr atthatnaggg 'lrllb the anode, which anode would otherwise produce tilii in an oscillator-modulator circuit, the the mst ntlceajble dlsturbmg eeci upon the signal amplification control or emission control bias of the amplifying control electrode, or sigy ma be variedy as b an au electrodes because of the relatlvely high voltage nal Input electrode y y at which the anode operates. Further, the cirtomatic volume control circuit, without disturbing the characteristics of the oscillator circuit in- Cults aSSoClated with certain of the electrodes are cluding two electrodes nearer the actual cathode, usually tuned to widely different frequencies so which generally constitute the grid and anode that the impedances of certain of the circuits are of the oscillator section of the tube. low at the frequency of the voltage impressed upon a given electrode, so that the voltage developed across such circuits is negligible.

In particular, there exists an undesirable capacitive coupling, comprising mainly geometric capacitance such as described above, between the signal input or amplification control electrode and the electrode which cooperates therewith to form a virtual cathode and which usually constitutes also the anode of the oscillator section of the vacuum tube. This relatively high capacitive coupling is due particularly to the relatively close spacing of these two electrodes. This coupling results in two effects which may modify the overall conversion gain of the system.

In the first place, the trans-conductance between the signal input electrode and the adjacent electrode nearer the cathode, which may constitute the oscillator anode, produces a variation in the current in the circuit of this latter electrode and develops upon the electrode a voltage of signal input frequency dependent in phase and magnitude upon the impedance of this circuit. This voltage, in turn, capacitively induces a current in the signal input circuit which develops upon the signal input electrode a voltage dependent in phase and magnitude upon the impedance of the signal input circuit and which may either aid or oppose the impressed signal input voltage. Since the trans-conductance between these electrodes is negative as compared with an ordinary triode, an inductive impedance in the oscillator anode circuit with respect to the signal frequency produces an effect which opposes that of the impressed signal input voltage; that is, eiectively reduces this voltage. This result is the usual one in systems in which the oscillator frequency is higher than the signal frequency and the oscillation circuit is inductive at the signal frequency. This effect may be termed, broadly, regeneration and may be positive or negative (degeneration) dependent upon whether it increasesor decreases, respectively, the signal input voltage. Although this regeneration does not directly affect the conversion gain of the tubeVits effect on the signal input voltage results in a change in the overall conversion gain of the system.

'Ihe capacitive coupling between the signal input electrode and the adjacent electrode nearer the cathode, that is, the oscillator anode, similar- 1y gives rise to a voltage of the oscillator frequency on the signal input grid which may aid or oppose the action of the emission control electrode. This eifect may be termed, broadly, remodulation and may be positive or negative (demodulation) dependent on whether it aids or opposes, respectively, that of the emission control electrode. This effect directly and correspondingly modies the conversion gain of the tube. Again, since the signal frequency is ordinarily below the oscillator frequency, the oscillator voltage on the adjacent electrode is of opposite polarity to that on the emission control electrode, and the signal input circuit is capacitive with respect to the oscillator frequency, this voltage on the signal input grid is of opposite polarity to that of the emission control electrode or oscillator grid, and therefore produces a remodulating effect.

A third effect is due to what may be termed the space-charge coupling between the virtual cathode and the signal input electrode. Variations in the space charge of the virtual cathode are produced primarily by the emission control electrode and, since a positive voltage on this electrode increases the negative space charge and thus the positive charge induced upon the signal input grid, the space-charge coupling may be considered as a negative capacitance between the two control grids. The nature of this coupling is thus opposite to that of the capacitive coupling between the signal input electrode and the oscillator anode but, due to the fact that the oscillator grid and anode voltages are also opposite in phase, the resultant remodulating 10 effect of the space-charge coupling is similar to,

and cumulative with, that of the geometric capacitive coupling described above, thus modifying the conversion gain of the tube in a similar manner. 15

Thus it is seen that, under the particular conditions described, that is, and oscillator-modulator in which the oscillator frequency is higher than the signal input frequency, all three factors described above contribute to a reduction in the 20 overall conversion gain of the system.

It is an object of my invention, therefore, to provide a signal-translating and -modulating system, including a vacuum tube of the type described above, in which the behavior of the 2 modulator and associated circuits is substantially independent of the capacitive coupling of various kinds between the several electrodes thereof.

More specifically, it is an object of my invention to provide a signal-translating and -modu- :zo lating system, including a vacuum tube of the type described above, in which an external interconnection between the signal input electrode and the emission control electrode effects a transfer of current therebetween to compensate for, and to neutralize the effects of, the transfer of current between these circuits by the capacitive coupling therebetween, namely, the geometrical and/or the space-charge coupling.

In accordance with my invention, a signaltranslating and -modulating system including a vacuum tube having a cathode, a virtual cathode, an output electrode, and control electrodes for independently controlling the electron current from the cathode and from the virtual cathode, is provided with means for supplying currents to the signal input or amplification control electrode circuit and the emission control electrode circuit, the eifects of which are equal and opposite to the capacitive coupling effects noted above. More specifically, in accordance with my invention, the means for reducing the above-noted effects of the capacitive coupling between the electrodes comprises external capacitive couplings between the signal input or amplification control electrode and between the emission control electrode and points in the system the potential variations of which are related in a proper manner in phase and magnitude to those of the electrodes which give rise to the described disturbing eifects. For example, the coupling may be made between the amplification control electrode and the emission control electrode adjacent the actual cathode, in case the tube is included in an oscillator-modulator system. In general, the value of this external coupling necessary to compensate for the geometrical capacitive coupling, described above, may be determined from the relation that the ratio of the value of the external coupling to that of the inherent coupling between two electrodes is substantially equal to the ratio of the amplitude of the potential variations of the electrode giving rise to the disturbing effects to that of the point at which the external coupling is made. The value of the external coupling necessary to comsinner eww ai '.'Jamaaasxf pensate for the space-charge coupling may best be determined experimentally by adjusting the value of this coupling to neutralize the undesired capacitive couplings and thereby to secure normal conversion gain.

For a better understanding of my invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

The single figure of the drawing is a schematic circuit diagram of a complete superheterodyne radio receiver including an oscillator-modulator embodying my invention.

Referring now more particularly to the drawing, there is shown schematically a circuit diagram of a complete superheterodyne receiver modified in accordance with my invention. This receiver comprises an input circuit I0 for connection between an antenna I I and ground, connected to a radio-frequency amplifier I2, the output circuit of which is connected to a coupling transformer I3 tunable by a condenser I4. The tunable circuit I 3-I 4 is connected to the signal input or amplification control electrode I5a of a vacuum tube I5 provided also with the usual cathode |5b of any suitable type and an anode |5c. Included in the circuit from cathode to ground is a biasing resistor I6 and a by-pass condenser II.

The radio-frequency energy derived from the input circuit I0 may be utilized to modulate a source of local oscillations generated either in a separate tube or, as shown, in the tube I5 which i is provided with additional electrodes I5d and I5c. The electrode I5e constitutes the emission control electrode or oscillator grid, while electrode I5d comprises the oscillator anode and is connected to a suitable source of direct voltage, indicated as +B, through a resistor 22. The oscillation circuit comprises a variable tuning condenser |9, and an aligning condenser 2| connected in series across an inductance 20, this circuit being connected between the oscillator grid I5e and ground. A grid leak a is preferably connected from the junction of inductance 20 and condenser 2| to the cathode |5b, as illustrated. A feedback from the oscillator anode circuit to the grid circuit is provided by means of an inductance 23 included in the anode circuit and coupled to the inductance 20; a condenser 24, directly coupling the lower terminals of the inductances 20 and 23; and the aligning condenser 2|, which is common to the oscillator grid and anode circuits. The vacuum tube I5 is preferably provided also with a screen grid I5f interposed between the amplification control electrode I5a and the anode I5c and connected to a suitable source of direct voltage, indicated as -l-Screen, through a resistor 25 and a by-pass condenser 2B. The tuning condensers I4 and I 9 are mechanically interlocked for unicontrol, as indicated by the dash lines interconnecting them, which unicontrol may be utilized also to tune the circuits of the radio frequency amplifier I2.

The modulated carrier wave produced by the foregoing apparatus is transmitted through the tuned coupling transformer I8 to an intermediatefrequency amplifier 21, thence through a detector 28 and an audio-frequency amplifier 29 to a sound reproducing device, such as a loudspeaker 30.

The above-described apparatus constitutes a conventional superheterodyne radio receiver, as modified in accordance with the teachings of my aforementioned patent, and, per se, constitutes no UUUI UII part of my present invention, so that a detailed explanation of its operation is deemed unnecessary. In brief, the signal-modulated carrier wave received from the antenna circuit I0 is amplified in the radio-frequency amplifier I 2 and, thus 5 amplified, is impressed upon the control electrode I5a of the combined oscillator-modulator I5. The cathode |517, oscillator grid I5e and anode I5d, together with their associated coupled oscillatory circuits, constitute a source of local oscillations which are effective to cause a periodic fluctuation in the emission from the cathode |5b and, thus, a periodic fluctuation in the available source of electrons for the amplification modulation section of the tube I5.

As described in more detail in my aforementioned patent, the oscillator anode I5d, which is of grid construction, is maintained at a positive potential by virtue of its connection to the terminal +B and attracts electrons emitted from the cathode |5b which, because of their high velocity, largely pass through the mesh of the electrode |5d. The magnitude of this stream of electrons is caused to fiuctuate periodically by virtue of the oscillator grid I 5e. The amplification control elec- 25 trode I5a, on the other hand, is maintained negative with respect to the cathode I5b by the magnitude of the biasing potential across resistor I6. This latter electrode is effective to retard the progress of the electrons beyond the oscillator 30 anode I5d, and a large portion of them is turned back toward the positively charged electrode I5d. This action results in a mass or cloud of electrons which normally exists between the electrodes I 5d and I5a., which has been termed a virtual cath- 35 ode in that it has many of the characteristics of the actual cathode, although it is not actually a cathode structure.

The electron emission from the secondary or virtual cathode is controlled by the electrode I 5a 40 in a manner very similar to the control by a grid electrode in an ordinary triode. The result of this arrangement is that the signal input voltage, impressed upon the control electrode I5a, is elective to modulate the locally produced oscillations to produce an intermediate signal-modulated frequency which may be amplified and/or converted in any desired manner.

In a circuit arrangement of the type just described where, in general, the composite functions of emission and modulation or amplification control are effected in a single tube, there is a tendency toward a modification of the apparent conversion gain of the oscillator-modulator system due to one or both of the effects of regeneration and remodulation. As stated above, these effects can be traced to the inherent coupling between the amplification or modulation control electrode and the emission control electrode and/0r the interposed electrode, or their connected circuits. The term inherent coupling is employed herein t0 denote the interelectrode capacitance between two electrodes, for example, the electrodes I5a and |5d, as Well as any residual capacitive coupling between their associated circuits.

In accordance with my invention, this effect on the conversion gain of the oscillator-modulator system is substantially eliminated or neutralized by an external coupling from the amplification control electrode I5a and the emission control 70 electrode I 5e to sources of voltage effective to transfer currents to their respective circuits having effects equal and opposite to those resulting from the inherent capacitive coupling of these electrodes with one or more of the electrodes with- 75 in the tube. This neutralizing effect may be derived in any of a number of ways. For example, the amplification control electrode and the modulaton control electrode may be connected to points in the system at which the potential variations are related in phase and magnitude to those which result in the above-described effects.

Specifically, when my invention is applied to an oscillator-modulator of the type described in which the potential variations of the oscillator grid l5e and anode |511 are in phase opposition, the amplification control electrode I5a and the oscillator grid l5e may be externally capacitively coupled in any suitable manner, as by a condenser 3l. By this means not only is there developed on the signal input or amplification control electrode a voltage of oscillation frequency effective to compensate for that developed thereon by the inherent capacitive coupling of this electrode with the oscillator anode 15d and by the space-charge coupling of the virtual cathode tending to effect remodulation, but also there is developed on the emission control electrode a voltage of signal input frequency effective to compensate for that developed upon the oscillator anode ld and, by the inherent capacitive coupling with the control electrode I5a, tending to effect regeneration. Thus, regeneration and remodulation are substantially eliminated and a maximum overall conversion gain of the oscillatormodulator system may be obtained.

As stated above, the value of the capacitance lof the coupling condenser 3l required to neutralize that component of the capacitive coupling comprising the geometrical capacitive coupling between the electrodes, is determined by the relation that the ratio of the capacitance of the condenser 3l to that of the inherent coupling between the oscillator anode I5d and the control electrode |5a is substantially equal to the ratio of the amplitude of the potential variations of the electrode l5d to that of the oscillator grid l5e at which the external coupling is made. The value of the external coupling necessary to compensate for the inherent space-charge coupling can be determined only experimentally under normal operating conditions, but it is generally of the order of a few micromicrofarads. The coupling condenser 24 may be adjusted to aid in neutralizing this latter coupling. In a specific circuit, utilizing a pentagrid converter of the A1 type as the tube l5, a value of capacitance for the condenser 3l of from 1.0 to 1.3 micromicrofarads was found to be satisfactory.

While I have indicated sources of direct voltage symbolically denoted as -l-Screen and +B, it is to be understood that any suitable source of operating voltage for the system as a whole may be utilized, such as a conventional battery or a rectifier and filter.

While I have described what I at present consider the preferred embodiment of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from my invention, and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What is claimed is:

1. A signal-translating and -modulating system including a vacuum tube having a cathode, an output electrode, and a plurality of grid electrodes interposed therebetween, an input circuit connected to a rst of said grid electrodes, a circuit of substantial impedance connected to an adjacent grid electrode nearer said cathode, whereby a voltage of input frequency developed on said latter electrode has a regenerative effect on said input circuit, and means for substantially eliminating the effect of said regenerative action on the conversion gain of the system comprising means for supplying to one of said grid electrodes a current of input frequency having an effect on the resultant electron stream to said anode equal and opposite to that of said regenerative effect.

2. A signal-translating and -modulating systern including a vacuum tube having a cathode, at least three grid electrodes and an output electrode spaced in the order named, a signal input circuit connected to the third of said grid electrodes, a circuit of substantial impedance connected to the second of said grid electrodes, whereby a voltage of input frequency developed on said second electrode has a regenerative effect on said input circuit, and means for substantially eliminating the effect of said regenerative action on the conversion gain of the system comprising means for supplying to said first grid electrode a current of input frequency having an effect on the resultant electron stream equal and opposite to that of said regenerative effect.

` 3. A signal-translating and -modulating system including a vacuum tube having a cathode, an output electrode, and a plurality of grid electrodes interposed therebetween, an input circuit connected to a first of said grid electrodes, a circuit of substantial impedance connected to an adjacent grid electrode nearer said cathode, whereby I a Voltage of input frequency developed on said latter electrode has a regenerative effect on said input circuit, and means for substantially eliminating the effect of said regenerative action on the conversion gain of the system comprising an external capacitive coupling from one of said grid electrodes to a point in said system the potential variations of which are related in phase and magnitude to those developed on scid second-named electrode.

4. A signal-translating and -modulating system including a vacuum tube having a cathode,an output electrode, and a pluralityof grid electrodes interposed therebetween, a signal input circuit connected to a first of said grid electrodes, a circuit including a source of oscillations and having a connection to at least one of the other of said grid electrodes, an inherent capacitive coupling between said input electrode and said other grid electrode, whereby a voltage of oscillation frequency developed on said signal input electrode has a remcdulating effect on the output of said tube, and means for substantially eliminating the effect of said remodulating action on the conversion gain of the system comprising means for supplying to one of said grid electrodes a current of oscillation frequency having an effect on the resultant electron stream to said anode equal and opposite to that of said remodulating effect.

5. A signal-translating and -modulating system including a vacuum tube having a cathode, at least three grid electrodes and an output electrode spaced in the order named, a signal input circuit connected to the third of said grid electrodes, an oscillation system including connections to said first and second grid electrodes, an inherent capacitive coupling between said signal input electrode and said oscillation system and its associated electrodes, whereby a voltage of oscillation frequency developed on said signal input @gime tNtHljY electrode has a remodulating eiect on the output of said tube, and means for substantially eliminating the effect of said remodulating action on the conversion gain of the system comprising means for supplying to one of said grid electrodes a current of oscillation frequency having an effect on the resultant electron stream to said anode equal and opposite to that of said remodulating effect.

6. A signal-translating and -modulating system including a vacuum tube having a cathode, an output electrode, and a plurality of grid electrodes interposed therebetween, a signal input circuit connected to a rst of said grid electrodes, a circuit including a source of oscillations and having a connection to at least one of the other of said grid electrodes, an inherent capacitive coupling between said input electrode and said other grid electrode, whereby a voltage of oscillation frequency developed on said signal input electrode has a remodulating effect on the output of said tube, and means for substantially eliminating the effect of said remodulating action on the conversion gain of the system comprising an external capacitive coupling from said signal input electrode to a point in said system the potential variations of which are related in phase and magnitude to those developed on said signal input electrode by said capacitive coupling.

7. A signal-translating and -modulating systern including a vacuum tube having a cathode, a rst control electrode, a second control electrode and an output electrode spaced in the order named, said tube having means including a third electrode interposed between said control electrodes for forming a virtual cathode therebetween, a signal input circuit connected to one of said control electrodes, an emission control circuit connected to the other control electrode, said control electrodes having an inherent spacecharge coupling therebetween, whereby a voltage of emission control frequency developed on said signal input electrode has a remodulating effect on the output of said tube, and means for substantially eliminating the eiect of said remodulating action on the conversion gain of the system comprising means for supplying to one of said electrodes a current of emission control frequency having an effect on the resultant electron stream to said anode equal and opposite to that of said remodulating eiect.

8. A signal-translating and -modulating systern including a vacuum tube having a cathode, a rst control electrode, a second control electrode and an output electrode spaced in the order named, said tube having means including a third electrode interposed between said control electrodes for forming a virtual cathode therebetween, a signal input circuit connected to one of said control electrodes, an emission control circuit connected to the other control electrode, said control electrodes having an inherent spacecharge coupling therebetween whereby a voltage of emission control frequency developed on said signal input electrode has a remodulating eiect on the output of said tube, and means for substantially eliminating the effect of said remodulating action on the conversion gain of the system comprising an external capacitive coupling from said signal input electrode to a point in said system the potential variations of which are related in phase and magnitude to those developed upon said signal input electrode by said space-charge coupling.

9. A signal-translating and -modulating system including a vacuum tube having a cathode, a flrst control electrode, a second control electrode and an output electrode spaced in the order named, said tube having means including a third electrode interposed between said control electrodes for forming a virtual cathode therebetween, said control electrodes having an inherent space-charge coupling therebetween and being effective to control the electron stream from said cathode and said virtual cathode, respectively, and a condenser connected between said control electrodes eiective to neutralize said space-charge coupling.

10. A signal-translating and -modulating system including a vacuum tube having a cathode, a rst control electrode, a second control electrode and an output electrode spaced in the order named, said tube having means including a third electrode interposed between said control electrodes for forming a virtual cathode therebetween, a signal input circuit connected to one of said control electrodes, a circuit including a source of oscillations having a connection to the other of said control electrodes, whereby the space-charge coupling between said control electrodes develops a voltage of oscillation frequency upon said signal input electrode having a remodulating effect on the output of said tube, and means for substantially eliminating the effect of said remodulating action on the conversion gain of the system comprising means for supplying to said signal input electrode a current of oscillation frequency having an effect on the resultant electron stream to said anode equal and opposite to that of said remodulating eect.

11. A signal-translating and -Inodulating system including a vacuum tube having a cathode, a rst control electrode, a second control electrode and an output electrode spaced in the order named, said tube having means including a third electrode interposed between said control electrodes for forming a virtual cathode therebetween, said control electrodes being effective to control the electron stream from said cathode and said virtual cathode, respectively, an oscillation circuit including connections to one of said control electrodes and said third electrode, and means for substantially eliminating the effect of the capacitive coupling between the other of said control electrodes and said oscillalation circuit and its associated electrodes comprlsing a neutralizing condenser connected between said control electrodes.

l2. A signal-translating and -modulating system including a vacuum tube having a cathode, a rst control electrode, a second control electrode and an output electrode spaced in the order named, said tube having means including a third electrode interposed between said control electrodes for forming a virtual cathode therebetween, a signal input circuit connected to one of said control electrodes, an oscillation circuit including connections to the other of said control electrodes and to said third electrode, an inherent` capacitive coupling between said input electrode and said third electrode, whereby a voltage of oscillation frequency developed on said signal input electrode has a remodulating effect on the output of said tube, said control electrodes having an inherent space-charge coupling therebetween, whereby an additional voltage of oscillation frequency developed on said signal input electrode has an additional remodulating effect, and means for substantially eleminating the effect of said remodulating actions on the conversion gain of the system comprising means for supplying to one or more oi.' said electrodes a current of oscillation frequency having an eiect on the resultant electron stream to said anode equal and opposite to that of said remodulating effects.

13. A signal-translating and modulating system including a vacuum tube having a cathode, an output electrode, and a plurality of grid electrodes interposed therebetween, an input circuit connected to a first of said grid electrodes, a circuit of substantial impedance connected to an adjacent grid electrode nearer said cathode, whereby a voltage of input frequency developed on said latter electrode has a regenerative effect on said input circuit, a circuit including a source of oscillations and having a connection to at least one of said grid electrodes other than said input electrode, an inherent capacitive coupling between said input electrode and said last-mentioned electrode whereby a voltage of oscillation frequency developed on said signal input electrode has a remodulating effect on the output of said tube, and means for substantially eliminating the eiect on the conversion gain of the system of said regenerative and remodulating actions comprising means for supplying to one of said grid electrodes a current of input frequency having an effect on the resultant electron stream to said anode equal and opposite to that of said regenerative effect and means for supplying to one of said grid electrodes a current of oscillation frequency having an effect on said resultant electron stream equal and opposite to that of said remodulating eiect.

14. A signal-translating and -modulating system including a vacuum tube having a cathode, a rst control electrode, a second control electrode and an outputelectrode spacedin the order named, said tube having means including a third electrode interposed between said control electrodes for forming a virtual cathode therebetween, a signal input circuit connected to one of said control electrodes, an oscillation circuit including connections to the other of said control electrodes, a circuit of substantial impedance connected to said third electrode, an inherent capacitive coupling between said input electrode and said third electrode whereby a voltage of input frequency developed on said latter electrode has a regenerative eiect on said input circuit and whereby a voltage of oscillation frequency developed on said signal input electrode has a remodulating effect on the output of said tube, said control electrodes having an inherent spacecharge coupling therebetween whereby an additional voltage of oscillation frequency developed on said signal input electrode has an additional remodulating eiiect, and means for substantially eliminating the effect of said regenerative and remodulating actions on the conversion gain of the system comprising means for supplying to said signal input circuit a current of oscillation frequency equal and opposite to the currents induced therein by said couplings and for supplying a current of signal input frequency to one of said electrodes having an eiect on the resultant electron stream to said anode equal and opposite to that of said regenerative effect.

15. A signal-translating and -modulating system including a vacuum tube having a cathode, a rst control electrode, a second control electrode and an output electrode spaced in the order named, said tube having means including a third electrode interposed between said control eleQ- trodes for forming a virtual cathode therebetween, a signal input circuit connected to one of said control electrodes, an oscillation circuit including connections to the other of said control electrodes, a circuit of substantial impedance connected to said third electrode, an inherent capacitive coupling between said input electrode and said third electrode whereby a voltage of input frequency developed on said latter electrode has a regenerative effect on said input circuit and whereby a voltage of oscillation frequency developed on said signal input electrode has a remodulating effect on the output of said tube, said control electrodes having an inherent space-charge coupling therebetween whereby an additional voltage of oscillation frequency developed on said signal input electrode has an additional remodulating eiect, and means for substantially eliminating the effect of said regenerative and remodulating actions on the conversion gain of the system comprising an external capacitive coupling between said control electrodes.

16. A signal-translating and -modulating system including a vacuum tube having a cathode, a rst control electrode, a second control electrode and an output electrode spaced in the order named, said tube having means including a third electrode interposed between said control electrodes for forming a virtual cathode between said control electrodes, a signal input circuit connected to said second control electrode, an oscillation system including connections to said first control electrode and to said interposed electrode, and means for substantially eliminating the eiect on the conversion gain of the system of the inherent coupling between said signal input electrode and said oscillation system and associated electrodes comprising a coupling between said control electrodes.

17. A signal-translating and -modulating system including a vacuum tube having a cathode, a first control electrode, a second control electrode and an output electrode spaced in the order named, said tube having means including a. third electrode interposed between said control electrodes for forming a virtual cathode between said control electrodes, a signal input circuit connected to one of said control electrodes, an oscillation system including connections to said first control electrode and to said interposed electrode, said oscillation circuit operating at a. frequency substantially higher than said signal input circuit, and means for substantially eliminating negative regeneration due to the inherent coupling between said signal input electrode and said oscillation system and associated electrodes comprising a coupling between said control electrodes.

18. A signal-translating and -modulating system including a vacuum tube having a cathode, a rst control electrode, an auxiliary electrode, a second control electrode, a screen electrode, and an output electrode spaced in the order named, said auxiliary electrode and said control electrode remote from said cathode together forming a virtual cathode, a. signal input circuit connected to one of said control electrodes, an oscillation circuit including connections to the other of said control electrodes and to said auxiliary electrode, a circuit including a source of voltage for maintaining said screen electrode positive with respect to said cathode, and means for substantially eliminating the eiect on the conversion gain of the system of the inherent coupling between said signal input electrode and said oscillation circuit and associated electrodes comprising an external capacitive coupling between said control electrodes.

19. A signal-translating and -modulating system including a vacuum tube having a cathode, a first control electrode, a second control electrode and an output electrode spaced in the order named, said tube having means including a third electrode interposed between said control electrodes for forming a virtual cathode between said control electrodes, a signal input circuit connected to one of said control electrodes, an oscillation system including coupled circuits one connected between said cathode and said first control electrode and the other between said cathode and said interposed electrode, and means for substantially eliminating the effect on the conversion gain of the system of the inherent coupling between said signal input electrode and said oscillation system and associated electrodes comprising a capacitive coupling between said control electrodes and a second capacitive coupling between the coupled circuits of said oscillatory system.

20. A superheterodyne radio receiver comprising means for seletingndiamplifying a signalmodulated carrier wave, an oscillator-modulator for converting said carrier Wave into one of lower frequency comprising a vacuum tube having a cathode, a rst control electrode, an auxiliary electrode, a second control electrode and an output electrode spaced in the order named, said auxiliary electrode and said second control electrode cooperating to form a virtual cathode, a circuit coupling the output section of said ampli- GEUCH H001 fying means to a rst of said control electrodes, an oscillation circuit including connections to the other of said control electrodes and to said auxiliary electrode, means for substantially eliminating the effect on the conversion gain of the receiver of the inherent coupling between said first control electrode and said oscillation circuit and associated electrodes comprising an external coupling between said control electrodes, means coupled to the output electrode of said oscillatormodulator for amplifying the output modulation frequency thereof, means for detecting said amplified modulation frequency, and a signal-reproducing device coupled to said detecting means.

21. In a superheterodyne radio receiver, a fresaid first controlAelectogndsaid,cathode, andr a capacitance elementggonnutedmbetween said control electrodes and proportioned substantially to neutralize atY therpsilwlatin frequency the space-charge couplingj/rompsaid rst,cnnt1;ol electrode to said second control electrode caused by said virtual cathode.

HAROLD A. WHEELER.

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