US2210015A - Electron oscillation generator and phase modulator - Google Patents

Description

1940- I a. 1.. USSELMAN 2.210.015

ELECTRON OSCILLA'IION GENERATOR AND PHASE llODULATdR Filed lay 29. 5 Sheets-Sheet 1 OUTPUT SOURCE L5 INVENTOR aim/551,144

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ELECTRON OSOILLATION GENERATOR AND PHASE MODULATOR Filed lay 29. 1937 5 Sfieets-Sheet 5 'swauaL saunas INVENTOR 6. L. USSELMAN w'u-bx/ ATTORNEY 30 equivalent means.

Patented Aug. 6, 1940 UNITED STATES PATENT "OFFICE ELECTRON OSGILLATION GENERATOR AND PHASE MODULATOR George Lindley Usselman, Port Jefferson, N. Y assignor to Radio Corporation of America, a

corporation of Delaware Application May 29, 1931, Serial No. 145, A

18 Claims.

electrodes which form part of a tube structure,

' modulating the electron stream in accordance with the produced oscillations, and impressing on said oscillations and said prior modulation effect,

phase variations in accordance with signals, and

thereby producing high frequency oscillatory energy in the anode circuit of substantially constant' mean frequency and of a phase characteristic of the modulations impressed at signal frequency on the oscillations.

A feature of the invention is the combined oscillation generator and phase modulator of the electron coupled type. The circuit may be neutralized or reaction may be prevented by the use of a grounded electrode intermediate the electron 5 generating electrodes and the output electrodes.

The oscillation generators of my novel invention in several of theirmo'dified forms, have no resonant electrical circuit associated directly with the oscillating circuit except a crystal or This circuit being electronically coupled by the electron stream only in the tube to the anode is unaffected by changes in impedance which are produced in the anode circuit due to the, variations in phase in the energy 3 produced therein such as those which might be produced by changes in -tuning or changes in load. Thus, stable operation of high efllciency is obtained. Stabilization and efiiciency is further enhanced by utilizing shielding means between 40 the crystal electrodes and between the electron generator electrodes and the output electrodes and by neutralizing the oscillation generation circuits. In other modified forms of my invention the output circuit is also substantially un- 5 tuned in which case additional stabilization is obtained.

In all of the modifications wherein the output circuit is tuned the same may be tuned to the frequency of the frequency stabilizing element in piezo-electric type. The anode electrodes are connected in push-pull relation with an output circuit which electrodes and circuit may be isolated with respect to the generating circuits by shielding electrodes which may be grounded for 5 the produced oscillations or by neutralizing means. In corresponding leads to like controlling v electrodes I insert phase displacing reactances which produce relative phase displacement of the oscillations generated. erThese displacing re- 10 actances' may also be disposed in the leads to the output circuit from the anode. By modulating the impedances of the tubes in phase opposition at signal frequency the two tubes supply varying amounts of high frequency energy to the output 15 circuit so that the resultant energy in the output circuit has a phase determined to a large extent by the phase of the energy supplied by that tube supplying the most energy at the particular in-' stance.

The modulating potentials may be applied at any of the several controlling electrodes including the cathodes and the anodes of the tubes.

Due to the symmetrical arrangement the oscillator circuit has excellent frequency stabilization together with high energy output. The entire high frequency circuit is well balanced as is the modulating circuit, so that phase modulation as applied to the circuit is well balanced thereby producing a good output with small distortion so and little amplitude modulation.

While, for purposes of illustration I have shown my invention as applied to generators and modulators of the push-pull type, it will be understood that the same is operative with a single tubeor substantially one-half of the circuits illustrated. In the latter case some amplitude modulation may-be inherently accomplished during the phase modulation process but this can be removed by expedients well known in the art, such as amplitude limiting, etc.

In describing my invention reference will be made to the drawings throughout which, insofar as possible, like reference characters indicate like parts and in which Figures 1 to 8 inclusive show various modifications of my novel oscillation generator and/or means for phase modulating oscillations generated by the same.

In Figure 1 the pair of electron tubes V1 Vzare connected substantially in push-pull relation at their outputs, which are electronically coupled to the crystal stabilized oscillation generating circuits connected with the controlling electrodes. The phase shifting reactances C and L crossconnect electrodes of the crystal with the conbe made to Figure 3 of the drawings which show applied to the controlling grids. Shield grids are provided to further isolate the output circuit and the oscillation generating circuits;

Figure 2 is similar in many respects to Figure 1. In Figure 2, however, the phase shifting reactances C and L are connected somewhat differently while the modulating potentials are applied to the screening electrodes and neutralizing cir cuits are provided. I

In Figure 3 the oscillation generator circuits only are shown and cross-neutralizing between the screeningelectrodes which form the anodes of push-pull oscillation generator and the controlling.electrodes is used. Any of the electrodes may be subjected to modulating potentials. Figure 3 shows this new' crystal oscillator circuit without means for modulation. This circuit is the basis for the circuit in which modulating means are provided.

In Figure 4, which is in some respects quite similar to the arrangement of Figure 1, modulation is applied to different grid electrodes, which also serve as the anodes of the oscillation generator circuits. Here again, cross-neutralization is used but the connections between the crystal and tube electrodes are uncrossed which is important as will be seen later since the mode of oscillation is different from that in the preceding figures.

The circuit in Figure 5 includes features of the circuit in Figures 1 and 3 and in addition utilizes from the prior flguresin that tubes of different types having additional electrodes areutilized. Both Figure 6 and Figure-'7 like Figure 4, have uncrossed connections to the crystal electrodes.

Figure 8 is a modification of the arrangement of Figure 7.

The novel method of and means for producing oscillatory energy will now be described and in. describing said method and means reference will been designated by reference numbers I, 2, and 3,

respectively. The tubes may also each include a ground shield not shown between the pairs of electrodes on each end of the crystal. The

heater electrodes H1 H2 are connected with any source of potential such as for example, shown at Band to ground as shown. The cathode electrodes K1 K2 are connected to the respective heater electrodes and to ground. The piezoelectric crystal X has two pairs of electrodes E1 E:

and E3 E1. E1 E2 are connected as shown to grids I in the two tubes V1 and V2. These may, in practice, be the controlling grids. Electrodes Ez'and E1 are cross-connected as shown to #2 grids in tubes V2 and V1. Grids I of tubes V1 and V11 are also connected together as shown by appropriate resistances R1 R: and the electrical center of these 7 resistances is connected to ground by an addisource by a by-pass condenser C4.

wave energy directly to any output circuit or to k R 2,210,016 trolling grids. The modulating potentials are A tional resistance R3 shunted by a by-pass condenser Cs. Grids 2 of tubes V1 and V: are connected together. by resistances R1 and R5, the electrical center on R1 R5 being connectedto a point of appropriate positive potential on source, 3 relative to the cathodes as shown. The potential source included in this latter circuit is shunted by by-passing condenser. C1. The additional electrodes 3 are connected together by resistances R6 R7, the junction points of the said resistances being connected to a point of positive potential relative to the cathodes. Radio frequency potentials as generated are shunted around these resistances and the energizing source by condensers C1 C2 connected as shown. The anodes A1 A: are connected together by a tuned circuit C; L1, a point on the inductance L1 of which is connected to a point of positive potential relative to the cathodes. High frequency potentials appearing in this circuit are shunted around the potential L1 may supply an output circuit coupled thereto as shown at In.

In some cases and in particular where high frequency oscillations are to be generated in the circuits connected between the cathodes and thecontrolling electrodes I and 2, it may be desirable .to neutralize the capacity between grids I and 2.

This may be done as shown'by connecting grid I of V to grid 2 of V2 through neutralizing condenser N1 and by connecting grid I of V3 to grid 2 of V1 through neutralizing condenser N2. These neutralizing condensers N1 and N2 neutralize the effect of capacity feedback between grids 2 and grids I in the crystal oscillator circuit.

It may be stated .here that Figure 3 maybe modified by connecting grids I and 2 in;each tube uncrossed to the crystal electrodes.- In thisbase the neutralizing connections would have to -be crossed. Crossed and uncrossed grid to crystal connections produce different modes of oscillation.

The oscillations generated in a manner described more in detail hereinafter may be modulated in phase. by providing means in corresponding circuits either in the oscillation generating circuits or the output circuits for producing relative phase shift in the voltages reaching corresponding electrodes or leaving corresponding electrodes and then varying in phase opposition the tube impedances. The tube impedances may be varied in phase opposition by applying modulating potentials to any of the electrodes therein in phase displaced relation. When the cathodes are modulated in phase displaced relation means must of course be provided for raising the same above ground alternating currentpotential.

In Figure 1 phase modulation is accomplished by connecting a-modulating potential source 0 in phase opposition to points on resistances R1 and R2 to control in phase opposition the potentials on electrodes I of tubes V1 and V2. In a particular application this modulating circuit may include a transformer T having its primary winding connected to the modulating potential source and a secondary winding having its terminals connected to points on R1 and R: and its midpoint connected to the terminal of R3 and to a point intermediate two coupling condensers III and I2 separating biasing and modulating re sistors R1 and R2. The phase shifting reactances designated by L and C are cross-connected between the electrodes E1 and E2 of crystal X and controlling grids I of tubes V2 and V1 respectively in Figure 1.

L are directly (uncrossed) connected between electrodes E1 and E2 and controlling grids I of tubes Vl' and V2 respectively. In Figure 1 no neutralizing circuits are used. The electrodes 3 are at ground radio frequency potential and shield the output electrodes and circuits from the generation and modulation circuits. In Figure 2 the electrodes I and 2 of tubes V1 and V2 are connected to the grids 2 and I of V2 as in Figure 3. The electrodes E3 E4 and grids 2 are cross-connected as in Figure 3. The circuits of Figures 1 and 2 are otherwise sufliciently similar to the cir cuit of Figure 3, described in detail hereinbefore to render undesirable further description thereof.

The phase shifting reactances L and C need i not necessarily be connected in the leads to electrodes I of tubes V1 and V since obviously they may be removed therefrom and inserted in the leads to electrodes 2 of tubes V1 and V2 or in the leads connected between the anodes of V1 and V2 and the tank circuit L1 'Cs.

The operation of the crystal controlled .osci1-- lator as illustrated in Figures 1, 2, and 3 and in particular in Figure 3 is as follows. The grids I and 2 of tubes V1 and V2 are cross-connected or coupled through the crystal X so that the oscillating potentials on grids I and 2 in each tube will oppose in phase sufficiently to maintain oscillations in the tubes and circuits when the crystal oscillates. These oscillations in the crystal are of the well known thickness vibrations, e. g., of a frequency determined by the thickness of the crystal. Electrical energy oscillations are fed to the crystal from #2 grids which keep the crystals oscillating mechanically. These mechanical oscillations are converted to electrical potential osgillations and then delivered to #I grid of each tu e. out of phase relation between grids #I and #2 in each tube which will produce oscillations.

The amplified oscillations in the tubes are fed to grids #2 and the process is repeated or accumulativeso that sustained oscillations of substantially constant frequency are produced in the tubes and circuits.

Positive potential is supplied to #2 grids through resistors R4 and R5 from the source B. Negative bias potential is obtained through current rectification in the circuits to the #I grids which produce biasing potentials in resistances R3, R1, and R2, the resistance R3 being by-passed by a radio frequency by-pass condenser C6.

The resistors R1, R2, R4, R5 supply grid and anode circuit impedance, without which oscillations would be of low amplitude resulting in inefllcient and poor operation.

As to the oscillator generator circuits, grids #3 of each tube being grounded for high frequency wave energy by condensers C1 and C2 which serve as s eens or shields to prevent capacity reaction between the primary anodes A1 and A: and the oscillation generating circuits of the tube including the grid-like electrodes 2 which serve as anodes for the oscillation generating circuits.

In the modification shown in Figures 1, 2, and 3 the only oscillating means in the circuits producing the oscillations is the crystal X 50 that,

due'to the natural stabilization of the crystal,-

The resulting oscillations are more than out hereinbefore.

amplitude for reasons pointed The anode circuit obtains its energy or potentials through electron stream .coupling solely, which stream passes through the screening electrodes 3 of each tube. Thus, the anode tuned .circuit L1 C5 may be adjusted to resonance by means of variable condenser C5 and such adjustment of -the anode circuit or external changes of any other impedance which is produced therein due to load oscillation, is of minimum effect on the oscillating generating circuits and consequently on the frequency produced by said circuits. With zero temperature coefficient crystals this entire circuit becomes extremely stable in frequency since changes in the load circuit have substantially no effect on the crystal oscillations.

The anode circuit L1 C5 may be tuned to select either the fundamental crystal oscillator frequency or any odd harmonic thereof. Even harmonies could only be produced by connecting both anodes tothe same end of the anode circuit L1 Cs. I

In describing the manner lations produced are modulated in phase, reference will first be made to Figure 1 of the drawings. InductanceL connected between crystal electrode E2 andgrid I of tube V1 together with resistor R1 connected between grid I of tube V1 and ground through by-passing condenser I0 produce a lagging phase in the excitation delivered from the crystal to the grid I of tube V1. Ina similar manner capacity C and -re- .sistor R2 connected between grid I of tube V11 and ground through by-passing condenser I2,

produces a leading phase in the excitation voltage delivered to grid I of tube V2 by crystal X. In other words, there is produced a fixed although adjustable phase angle or difference between the excitation voltage delivered to the #I grids of tubes V1 and V2. This causes each tube to deliver or repeat or amplify these electrical oscillations on impulses with the same phase shift or difference. With proper electrode bias and equal or zero modulating potentials on the #I grids each tube supplies equal amounts of energy to the tank circuit L1 C5 (which might be zero or any value of energy within a reasonable range) so that the resultant energy in L1 C5 takes up a mean fixed phase position. In the presence of exact symmetry this resultant mean fixed phase relation should be in synchronism as to phase and frequency with the oscillations generated in the generator electrodes and circuits or harmonics thereof. As to the oscillation gen erator circuits per se, because of the inertia or fiy-wheel effect of the crystal it tends to operate at a substantially constant frequency with a phase angle substantially the average of that delivered by the tubes V1 and V2. However, in the presence of modulating potentials the potentials on the #I grid of tubes V1 and V2 are varied in phase opposition at signal frequency. This causes the tube which has the more favorable grid potential to deliver more power'to the tank circuit L1 C5 and thereby cause the phase of the energy in said tank circuit to approach the phase of the energy delivered by the said tube. Consequently as each tube has its impedance varied or modulated in phase opposition, the phase of the output energy in circuit L1 C5 is caused to swing back and forth in accordance with the modulating potentials between limits determined by the initial limiting phase shift in}- parted to the excitation voltages by phase shifting reactances L and C.

The frequency of the phase swing is determined by the signal frequency and the degree or amount of phase swing varies in accordance with the signal intensity or amplitude.

In Figure 2 the modulating potentials are applied to the screening electrodes 3 to modulate in a manner similar to that described hereinbefore in connection with Figure l the ability of the tubes to deliver current to the tank circuit L1 Ca. These modulating potentials being in phase opposition cause tubes V1 and V2 to supply instantaneously, various amounts of current to the tank circuit so that the resultant current therein takes up a phase position corresponding more closely to the phase position of that tub'e supplying the most energy which in turn corresponds to the application at' signal frequency of the more favorable controlling potential to the tube electrode.

In a preferred embodiment as illustrated in Figure-4, the modulating potentials are supplied or applied in phase opposition to the #2 grids which also serve as the anodes of the oscillation generator circuits of tubes V1 and V2. The operation of this modification will be readily under stood from the description of the phase modu lators illustrated in Figures 1 and 2 and need not be repeated at this point. Applicant wishes to note, however, that in the arrangement of Figure .4 as compared to, say, Figures 1, 2, and 3, the

grids I and 2' in Figure 4 as to their connections with the crystal are un-crossed. That is to say,

rids #I and #2 of each tube are connected to crystal electrodes on the sameside of the crystal. Theoretically at least, the oscillator, of Figure 4 is more correct and is more flexible than the oscillator of Figures 1, 2, and 3. In the circuit of Figure 4 cross-neutralization is utilized as in Figures 2 and 3. In Figure 4, however, a grounded shield S is inserted between the electrodes E1 E2 and E1 Eran'd astri-de the-crystal as shown. The shield S does not touch the crystal but does I come between the pairs of electrodes on the crystal to thereby prevent electrostatic coupling between the pair of electrodes on one end of the crystal and the pair of electrodes on-the other end of the crystal. Thus, the only coupling'between the #I grids of the tubes V1 and V2 and the #2 grids of the tubes VI. and V2 which act as the crystal oscillation circuit anodes is through the mechanical coupling of the crystal because the neutralizing condensers N1 N2 neutralize the capacity of the tube elements. This circuit was found to oscillate readily and produce sustained oscillations of substantially --constant amplitude and frequency and to have other features such as to make it a most desirable modification. The circuit has greater frequency stabilization and it also operates or functions in accordance with a readily understandable theory. The phase reversal (approximately 180) between the #I controlling electrodes and the #2 grid-like anodes occurs in the crystal X. Assume #2 grid in tube V1 positive and #2 grid in tube V2 negative and that the current is flowing through the crystal X from electrode E to electrode E4. Then, itis known that the current flow in the crystal X between electrodes E1 and E2 will be in the same direction that is a fixed or' generated current. Consequently, the voltage on electrodes E1 and E2 is a counter-voltage which is the reverse of the voltage on the electrodes E3 and E4. Therefore the voltage of control grids I in tubes V1 and V2 is in phase opposition to the voltages on the anbde-like grids I in tubes V1 and V: which additional feature not found in the prior figure.

In Figure 5 the generated oscillations are stabilized as to frequency by means of a. line of low power factor or low loss or a line in which the energy displaced per cycle of alternating current is extremely low as compared to the circulating current. This line comprises elements A and B which replace the usual crystal. The line A,'B' is of the double ended or push-pull type although any suitable type may be, used, such as for example, any line following the teaching of P. S. Carter and C. W. Hansell in their publication Frequency control by low power factor line circuits appearing in the April 1936 I. R. E. at page 597. The small impedance link Z is provided in order not to destroy the coupling between the two halves A and B of the line. The #I grids of tubes V1 and V1: are connected as shown to spaced points on the inner member B while the electrodes 2 of tubes V1 and V: are cross connected to spaced points on the inner member Bv of the line. The line is preferably of a half wavelength or shorter and when energized and connected as shown with the tube electrodes feeds potentials in phase opposition to. the #I grids which are amplified in the tube and fed from the #2 grids back to the line. The connections are such that the potentials on the grids I and 2 in each tube are in phase opposition which is again the ideal condition for the production of oscillations.- from the line to the tubes and from the tubes to the line so that a fiy-wheel oraccumulative effect is produced and oscillations are produced in the tubes, circuits and line of a frequency determined by the dimensions of the line A, B. Modulation is accomplished as in Figure 1.

In Figure 6, which is in many respects similar to the arrangement shown in Figure 4, the tuned output circuit has been replaced by a resistive circuit including resistors Ra Ra. Thus, in this arrangement we have no tuned or resonant circuits either in the output of the tube or in the oscillation generator portion of the system other than the crystal. Obviously improved operation is obtained by this circuit as far as frequency stabilization and waves of constant amplitude linearly phase modulated is concerned. This circuit will operate only on the fundamental frequency of the crystal since there are no tuned circuits to select harmonics.

In the arrangement of Figure 7, which in some respects is somewhat like Figures 4 and 6, I have utilized at V1 and V2 tubes of the RCA 6L7 type having five grids. This arrangement is in other respects similar to the arrangement discussed in connection with the prior figure. The additional grids 5 may be connected as shown to ground or if desired may be maintained at a potential slightly above or below ground potential. Here again the output circuit electrades are connected with impedances Ra Ra which may be resistances or reactances or may be replaced by a tuned circuit which in turn may be tuned either to the crystal frequency or to a harmonic of the frequency of the crystal.

Potentials are fed Y The oscillation generator electrodes are connected with the crystals as in Figures 4 and 6.

I odes and the oscillation generator circuit which feeds energy to the anodes by way of the electron stream due to the additional electrodes and to the eifect of the screening electrodes 4. Neutralizing condensers are unnecessary in this arrangement and, as will be seen, have been omitted. Figure 7 may use any of the features used in the preceding figures. For instance, we may use aresonant line in Figure 7 instead of the crystal, as shown in Figure 5.

It is important to note here that by suitable arrangements modulating potentials from S1 and T may be applied to #5 grids instead of the other grids as it has been done in the preceding figures. This modification is shown in Figure 8. By introducing the modulation on grids 5 no reaction whatever will be induced in the crystal oscillator circuits from the modulating potentials.

This is important since it would give a very practical and stable circuit. In this case grids 5 would be by-passed to cathode by small conden- .sers and the grids 5 would also be connect d in phase opposition to transformer T. These grids could be supplied with any desirable bias potential'from zero to any positive or negative value which is practical.

Iclaim: 1. A phase modulation system comprising in combination, an electron discharge tube having a plurality of electrodes some of which are connected in oscillation generating circuits and an-' other of which is connected in an output circuit coupled to said oscillation generating circuits substantially by the electron stream of said tube only, phase shifting means in-'one of said circuits, additional means for separating said gencuit coupled to said oscillation generating circuits by the electron stream of said tube only, frequency stabilizing means in the form of .a resonant low loss line connected with. said oscillation generating circuits,a source of modulating potentials and means for modulating'the phase of the oscillations generated in accordance with said modulating potentials.

3. In a signalling system in combination, an

electron discharge device having a cathode, a plurality of auxiliary electrodes, and an anode, circuit means connected with at least two of said auxiliary electrodes and said cathode for producing oscillations in said device of substantially constant amplitude and frequency, an aperiodic output circuit connected with the anode of said device and coupled to said oscillation generating electrodes and circuits by way of the electron stream only of the device, and means for modulating the phase of the produced oscillations comprising a phase shifting reactance in said circuit means and a source of modulating potentials coupled to electrodes in said device for modulating the impedance thereof and consequently the phase of the oscillations produced at signal frequency.

4. In a signalling system in combination, a-

plurality of electron discharge devices each having a cathode, a plurality of auxiliary electrodes, and an anode, circuits connected with at least two of said auxiliary electrodes and said cathode in each of said devices for producing oscillations in said devices and circuits, phase shifting reactance of different character in corresponding portions of said circuits, an output circuit connected with the anodes of said devices, said output circuit being coupled to said oscillation gen erating electrodes and circuits substantially by way of the electron streams only of the devices, means for shielding said output circuit from said auxiliary electrodes and means except for said electron stream coupling, and means connected with an electrode ineach of said devices controlling the gain of said devices in opposition at signal frequency for modulating thepscillations produced at signal frequency.

5. In a signalling'system in combination, a plurality of electron discharge devices each having a cathode, a plurality of controlling electrodes, and an anode, circuits connected with at least two controlling electrodes and the cathode of each device for producing oscillations in said a phase displacement between the oscillations supplied by said devices to said output circuit, and means connected with an electrode in each of said devices controlling the operativeness of said devices at signal frequency for modulating.

the phase of the oscillations produced at signal frequency. I

6.A phase modulated wave signalling system comprising in combination, a source of modulating potentials, an electron discharge device comprising oscillation generator electrodes and an output electrode, circuits interconnecting said oscillation generator electrodes for the production of oscillations, an output circuit connected with said output electrode and coupled to said generator electrodes and circuits substantially by the electron stream only of said electron discharge system, and means in said circuits connected with=the electrodes of said discharge device for modulating the phase of the oscillations generated.

7. A phase modulated wave signalling system comprising in combination, a source of modulating potentials, an electron discharge device an output electrode, circuits interconnecting said oscillation generator electrodes forthe production of oscillations, an output circuit connected with said output electrode and coupled to the comprising oscillation generator electrodes and generator electrodes and interconnecting circuits substantially by the electron stream only of said electron discharge device, means for shielding said generator electrodes from said output electrodes, and means in said circuits connected.

with the electrodes of said device for modulating the phase of the oscillations generated.

8. In a system for producing oscillatory energy of substantially constant frequency-and modulating the phase of the said energy in accordance with signalling potentials, a pair of electron discharge'tubes each having a cathode, a plurality of controlling electrodes, and an anode rality of terminals, circuits inter-connecting a pair of controlling electrodes in each of said tubes and terminals of said crystal, means for energizing said electrodes whereby oscillations are produced in said tubes and circuits, phase shifting reactances connected corresponding controlling electrodes. in each of said tubes to produce a of constant frequency and modulating the. phase modulating potentials and means coupling said source of modulating potentials in phase opposition to like electrodes in said tubes.

9. In a system for producing oscillatory energy of the said energy in accordance with signalling potentials, a pair of electron-discharge'tubes each having a cathode, a plurality of controlling electrodes, and an anode electrode, a piezo-eleotric crystal having a pluralityof terminals, circuits inter-connecting a pair. of controlling electrodes in each of said tubes and terminals of said crystal, means for energizing said electrodes whereby oscillations are produced in said tubes and circuits, phase shifting reactances connected with corresponding controlling electrodes in each of said tubes to produce a relative phase displacement of the oscillations produced by each tube, a nonreactive circuit connected with the anodes of said tubeaa source of modulating potentials and means coupling saidsource of modulating potentials in phase, oppositionto like electrodes in said tubes. i

10. A system as recited in claim 8 wherein said output circuit is tuned to a harmonic of the natural period of said crystal.

11. In a system. for producing oscillatory energy of constant frequency and modulating the phase of the said energy in accordance with signalling potentials, a pair of electron discharge tubes each having a cathode, a plurality of controlling electrodes, and an anode electrode, a resonant low lossline, circuits inter-connecting a pair of controlling electrodes in eachof said tubes and spaced points on saidline, meansfor energizing said electrodes whereby oscillations are produced in said means, line, circuits, and tubes, phase shifting reactances connected with corresponding controlling electrodes in each of said tubes to produce a relative phase displacement of the oscillations produced in each tube,

an output circuit connected with the anodes of said line is the only resonant reactance in all of said circuits.

13. In a system for producing oscillatory en ergy of constant frequency and modulating the phase of said energy in accordance with signals, a pair of electron discharge tubes each having a controlling electrode, a grid-like anode electrode, a shielding electrode, and an anode electrode, a

piezo-electric crystal having at least two pairs' of electrodes, means including phase'displacing reactances of different character connecting the electrodes of one of said pairs'of crystals electrodes to corresponding grid-likeelectrodes in said tubes, means connecting the electrodes of another pair of electrodesof said crystal to dif- L ferent corresponding electrodes in said tubes, '9. source of modulating potentials, means for ap- 2,210,015 electrode, a piezo-electric crystal having a plu-- plying modulating potentials in phase opposition. from said source to corresponding electrodes in said tubes, a' circuit connecting the anodes of said tubes in push-pull relation, and a circuit connecting said shielding electrodes to the cathodes of said tubes.

14. A system as recited in claim 13 whereinthe crystal electrodes of each of said pairs of crystal electrodes are on opposite sides of said crystal and the connections between the electrodes of said crystal and the electrodes of said tubes are direct.

15. In a system for producing oscillatory energy of constant frequency' and modulating the phase of said energy in accordance with signals, a pair of electron discharge devices each having a controlling electrode, a grid-like anode electrode,- an additional grid-like electrode and an' anode electrode adjacent said additional electrode, a piezo-electric crystal having at least two pairs of electrodes on opposite sides thereof, means including phase displacing reactances of different character directly connecting an electrode of one of said pairs of electrodes to the controlling electrodes in said tubes, means directly connecting the other electrodes of said pairs of electrodes of said crystal to the gridlike anode electrodes in said tubes, a source of. modulating potentials, means for applying modulating potentialsin phase opposition from said source to said additional grid-like electrodes in said tubes, and an aperiodic circuit connecting the anodes ofsaid tubes in push-pull relation.

16. In a system-for producing oscillatory energy of I substantially constant frequency and modulating the phase of the said energy in accordance with signalling potentials, a pair of electron discharge tubes each having a cathode,

\ a plurality of controlling electrodes, and-an output electrode, a frequency stabilizing element, circuits inter-connecting a pair of controlling electrodes in each of said tubes and points on said frequency stabilizing element, means for energizing said electrodes whereby oscillations are produced in.said tubes andcircuits, phase shifting reactances connected with corresponding controlling electrodes in each of said tubes to produce a relative phase displacement of the oscillations produced by each tube, an output circuit connected with the output electrodes of said tubes, a source of modulating potentials and means coupling said source of modulating potentials in phase opposition to like electrodes in said tubes.

17. In a system for producing oscillatoryenergy of substantially constant frequency and modulating the phase of the said energy in accordance with signalling potentials, a pair of electron discharge tubes each having a cathod aplurality of controlling electrodes, and an out-I /p'ut electrode, a frequency controlling means, circuits connecting a pair of. controlling electrodes in each of said tubes to said frequency controlling means, means for energizing said electrodes whereby oscillations are produced in said tubes and circuits, an output circuit connectedwith the output electrodes of said tubes 'and' coupled to the oscillation producing electrades and circuits substantially by the electron stream only of said tubes, means for producing a phase diiference between the oscillation supplied by the respective tubes to said output circu t, a source of modulating potentials and means coupling said source of modulating potentials in phase opposition to like electrodes in said tubes.

1 cuits, means for electrostatically shielding the electrodes connected in said oscillation generating circuits from an electrode connected with said output circuit, a source of modulating potentials and means for modulating the phase of the oscillations generatedvin said circuits in accordance with said modulating-potentials comprising a coupling between two electrodes in said tube and said source of modulating potentials.

GEORGE LINDLEY USSELMAN. 1

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