US2243216A - Frequency modulation - Google Patents

Description

May 27, 1941- N. E. LINDENBLAD FREQUENCY MODULATION Filed Dec. 21, 1940 3 Sheets-Sheet 1 JZEZ BL 06K IN G CONDENSERS INVENTOR. EZ/ NDENB LAD lV/ZS BY 77%? ATTORNEY.

y 1941- N. E. LKNDENBLAD 2,243,216

FREQUENCY MODULATION Filed Dec. 21, 1940 5 Sheets-Sheet 2 lwmau MODULATION l/ACl/l/M 708E SWITCH CIRCUIT INVEN T OR.

7flsgfz/N ENBl;AD BY 1 ATTORNEY.

y 27, 1941- N. E. LINDENBLAD I 2,243,216

FREQUENCY MODULATION Filed Dec. 21, 1940 s Sheets-Sheet s A I a Mad/7s 5'.LV7d 51: $38 I 2% 835 E i OSC/LZATOR PL A 75 SUPPLY INVEN TOR.

ATTORNEY.

Patented May 27, 1941 ilJNi TEE STATEfi RATE FREQUENCY MQDULATEON Delaware Application December 21, 194$,Serial No. 371,116

.35. Claims.

This application is a continuation-in-part of my application Serial No. 237,178, filed October 27, 1938, in turn a division of my United States application, Serial No. 13,886, filed March 30, 1935, now United States Patent No. 2,143,891.

Among the limitations often encountered'in frequency modulation systems are the following: The range of frequency variation produced in the high frequency oscillator is relatively small; the changes in frequency with modulation voltage are not always linear; undesirable amounts of amplitude modulation may be introduced; and also, there have been limitations as to frequency of modulation in that certain proposed systems have not been fast enough for higher modulation frequencies such as are used in television, for instance.

To overcome these shortcomings, is the principal object of my present invention. In carrying my invention out I feed back, through balanced electron discharge tube circuits, a certain amount of energy from the oscillator to its frequency controlling circuit. The phase and amplitude of the energy fed back is, however, varied by the modulating or control waves, as a consequence of which the efiective capacity or inductance or both of these characteristics of the frequency controlling circuit is so'varied that linear frequency modulation over a very wide range, much wider than the absolute frequency values of the modulating waves, is obtained. A particular advantage of my present invention resides in the fact that no moving parts are required, and further advantages are found in the freedom from amplitude modulation and the linear change in the frequency of the high frequency waves with respect to the modulating waves, potentials or currents.

In the accompanyingidrawings, which are only illustrative of my present invention, and which are not to be considered in any way limitative thereof, Figure 1 illustrates a high frequency oscillator, a frequency control circuit and a modulator coupled to said oscillator and to said frequency control circuit'to control the character thereof, and frequency modulate the produced waves;

Figure 2 is a modification in which the inductance and capacity of the frequency controlling circuit are simultaneously varied by means of phase and amplitude control in a balanced feedback circuit energy;

Figure 3 is a circuit explanatory of Figure 2; and

Figure 4 is an arrangement similar to Figure 2.--

(Cl. r17917 1.5)

Turning to Figure 1, the grids 2, 4 of the pushpull connected oscillation generator vacuum tubes 6, 8 are coupled through the loops l9, l2 in phase opposition with each other to the quarter wave frequency controlling line Mconcentrically mounted within the outer grounded metallic cylinder it. The frequency controlling line system H, I6 is preferably substantially one quarter the length of the waves to be generated as has been more fully described in patents of F. H. Kroger #2,108,895 and #2-,077,800, C. W. Hansell Patent #2095980, and in my Patent #2,095,980, hereinabove referred to, and may be of the type described by Kroger in that the cylinder or tube M is made substantially invariable in length despite ambient temperature changes. In fact, as a further precaution to insure frequency stability, the entire line controlling system I4, 16 may be housed within a constant temperature oven, not shown. The method of coupling the push-pull connected tubes 9, 8 in phase opposition to a quarter wave length line is more fully described and claimed in my Patent #2,121,158, dated June 21, 1938. For determining proper operation of the system the thermogal- 'vanometer i8, capacitively coupled by the metallic stud 20 to the free end or high potential end of line It, is provided. This measuring system is described and claimed more fully in my Patent #2,095,990, dated October 19, 1937. ,Grid bias for'the grids 2, 4 is obtained by means of the grid leak and condenser connections 22, 2

The cathodes 26, 23 are connected together in parallel for heating currents by means of conductors S9, 32, which act cophasally for high frequency currents. This cophasal action is enhanced'by means of by-passing condensers 34, 36, 3B. The filament system or the cathode heating system may be structurally made as shown 40' in my Patent #2,052,888, dated September 1, 1936, and my Patent #2952576, dated September 1, 1936, and are energized by the filament heating source 30. If desired, a variable condenser'42 may be provided for adjusting the filament or cathode impedance. The plates 34, 29 of the oscillator tubes 6, B are connected in phase opposition through the'loop circuit lB, 59' which may be made adjustable in length and tuned to the operating frequency. To assist in this adjustment a variable condenser 52 may be provided. Output energy from the oscillator may be taken from the loop 54 coupled to the cathode system or may be taken inductively from the loop 58 coupled to the'anode circuit i8, 50, 52.

Voltage from the output of t andSis fed through blocking condensers 60, 62 to the grids 64, 66 of the coupling and modulating tubes 68, 10. The condensers 60 and 62 are connected to points of opposed polarity on the lines 48 and 50 so that potentials displaced substantially 180 in phase are impressed on the grids of tubes 68 and 10. The filament circuit 12 for the cathodes 14, 16 of the tubes 68, 10 may be made identical to that of the oscillator tubes 6, 8 and hence need not be described in detail. The plates 18, 80 of tubes 68, 10 are connected together as shown and through conductor 82 to the loop 84 tuned by means of condensers 85, 88 which, though not essential, are helpful for adjustment purposes. Plate potential for tubes 68, 10 is supplied through lead 99. The loop 84 is connected to the metallic stud 92, provided with a capacity element or plate 94 adjacent, and preferably facing the high voltage end 96 of the quarter wave length line l4 which preferably is made hollow and cylindrical. The stud 92 may be insulatingly supported within the metallic cylinder [6 in a manner similar to the insulating support shown for stud 26, but this insulating support has been omitted for the sake of drawing clarity.

Modulating voltages are applied through the transformer I and radio frequency chokes I02, I64 in phase opposition to the grids of the tubes 63, 19, grid bias being fed through the secondary of the transformer I00 from the grid biasing source 106. Preferably the tubes 68, are both biased to operate near the lower bend of their characteristic curve. The modulating waves fed through the transformer I00 maybe of audio frequencies or may be super-audible frequency waves or low radio frequency waves, as found desirable or useful.

By virtue of the phase opposition connection of the grids 64, 66 of the modulating tubes 68,

'50, and the bias on said grids, the phase of the energy fed back to the capacity stud 94 is varied or reversed in accordance with reversals of the modulating waves or potentials fed to the transformer I00. The amplitude of the modulating waves, which is also variable, also controls the amount of energy fed back to the modulating tubes. Hence, by virtue of this differential biasing scheme, the capacity element or stud 92, 94 carries potential of reversible phase and of varying amplitude with respect to the end 96 of the frequency controlling line H. These potentials of varying phase and varying amplitude oppose or add to the potentials on the stud as the relative phases of the original energy and energy fed back changes to'an extent dependent upon the amplitude of the voltages fed back. Hence, there is a variation in the distribution of the electric flux from the end of the line in accordance with the modulating voltages in. transformer I90 and this is equivalent to a variation in the capacity at the end of the line M. This variation in capacity changes the natural period of the line l4 and hence the frequency of operation of the oscillator tubes 6, 8. The variation in frequency will be found to occur linearly over an extremely wide range depending upon the adjustments of the circuits used, and it will be found that the frequency modulated waves produced in the output circuits 54, 56 of the oscillator are remarkably free of amplitude modulation.

At this point attention may be called to the fact that one particular advantage of the foregoing system of frequency, modulation is that the tuning of the coupling tube circuit, that is to say, the modulation tube circuit, may be made as broad as needed without adversely affecting the power factor of the frequency controlling circuit l4, Hi. In addition, the power which the coupling tubes 68, 10 are required to handle is also very small as they are only required to affect a very small portion of the total oscillating power in the frequency controlling circuit, in the case shown, the line controlling system [4, I6. Since tuning of the stud circuit increases the impedance of said circuit and results in high mutual energy transfer from stud to line and from line to stud, due to enhanced unity power factor feed conditions, this stud circuit is often operated somewhat out of tune with the frequency of the system.

In Figure 1 the capacity of the frequency controlling circuit for an oscillation generator was varied in order to vary the frequency of oscillation in accordance with the modulating waves. In the scheme shown in Figure 2, both the capacity and inductance of a frequency controlling line or frequency controlling system or circuit is varied by the phase and amplitude controlled feed back.

For a better understanding of the system shown in Figure 2, reference is made to the schematic diagram shown in Figure 3. Turning to Figure 3, the generator G delivers power to the two tuned circuits C1, L1, and C2, L2. These two circuits are coupled to each other and have a mutual inductance M. By means of the switch connected as shown the phase of one of the circuits can be reversed with respect to the other. Because of this reversal of phase and due to the fact that the circuits have mutual reactance, the natural period of the combination will be different for the two positions of the switch and will also vary with respect to the amoimt of current drawn by each circuit.

With th foregoing principles in mind, the system of Figure 2 may readily be understood. The oscillator 500 of Figure 2 is frequency controlled by a frequency controlling resonant transmission line system 502 one-half wave length long. The oscillator 500 is more fully described in my Patent No. 2,095,990, dated October 19, 1937. A portion of the oscillator output is fed through the loosely coupled pickup coil to the vacuum tube switching circuit 506 which replaces the switch S of Figure 3. The vacuum tube switching circuit 506 is supplied with modulating waves through the modulation transformer I 00 so as to alternately render tubes 508 or 510 conductive, in this way reversing the feedback to the half wave line 504 which is coupled to the line 502. It is to be noted that line 504 corresponds to circuit C1, L1 of Figure 3, and line 502 to the circuit C2, L2 of Figure 3 and that the switch S of Figure 3 has been replaced in Figure 2 by the tube arrangement 506.

The two pairs of tubes 508, 5|0 form two pushpull coupling stages in which the phase of the grids in one pair is opposite to the phase of the grids in the other pair. As before explained, the plates are connected to a deflector or auxiliary line 504.

When there is no modulation potential in the transformer I06, the system is balanced so that the generator control line receives no energy from the four plates of the tube switching circuit 506. When, however, modulation is supplied, the tubes in which the grids are made more positive will provide a greater coupling than those which are made negative, as a result of which the effect upon the oscillator frequency controlling line 582 is the same as if-the reflector 504 had been moved back and forthwith respect to it, or is the same as if the inductance and capacity of the frequency controlling line 582 had been simultaneously varied. Preferably, the lines or circuits 594, 5&2 which exhibit parallel resonance effects are housed within a shielded compartment or within a metallic cylinder and temperature controlled.

Figure 4 is a system substantially identical to Figure 2 with the exception that the frequency controlling lines having distributed inductance and capacity have been replaced by the circuits 61111 and C2L2 shown in Figure 3 having lumped inductance and capacity.

As in Figure 2, the grids of tubes 598, 5538' of Figure 4 are excited by waves from the pickup coil 595)? in phase opposition. Similarly the grids of tubes 5H] and 5!!! are excited in phase opposition by waves from coil 5MP but the excitation of the grids of the pair of tubes 588, 508' is opposite, as explained above, to the excitation of the grids of tubes 5H], 5H). In other words, the r grids of tubes 568' and 5E0 are excited cophasally with waves from loosely coupled pickup coil 5MP and out of phase or in phase opposition with modulation waves from transformer I00. Sim.-

ilarly the grids of tubes 5138 and 5H! are excited cophasally with waves from coil scar and in phase opposition with modulation or lower frequency control waves from the secondary of transformer Hi9.

If desired, of course, the oscillator sac of Figure 4 may be provided with feed-back condensers FC1 and FC2 rather than rely upon interelectrode capacity feed-back of the oscillation generation tubes.

What is claimed is:

1. In a system for generating high frequency oscillatory energy and modulating the frequency thereof, an oscillator comprising, an electron discharge device having input and output electrodes coupled in oscillation generating and frequency controlling circuits including a frequency controlling line, an additional line coupled to said first named line to control the reactance of said first named line, means for feeding Wave energy from one of said oscillation circuits to said additional line, and means for varying the phase of the energy so fed to said additional line at signal frequency to thereby vary the phase of the coupling between said lines to vary the reactance of said first line and the frequency of the oscil- 1 lations generated.

2. A system as recited in claim 1 wherein said lines are inductively coupled.

3. A system as recited in claim 1 wherein said lines are parallel and inductively coupled.

i. In means for generating high frequency oscillatory energy and modulating the frequency thereof, an oscillator comprising, an electron discharge device having input and output electrodes coupled in oscillation generating and frequency controlling circuits including a frequency controlling line, an additional line coupled to said first named line to control the reactance of said first named line, electron discharge tube means for feeding Wave energy from one of said oscillation circuits to said additional line, and means modulating said tube means at signal frequency for varying the phase of the energy so fed to said additional line at signal frequency and varying the phase of the coupling between said lines:

to vary'the reactance 10fTSflid5filfSt lineiandthe frequency of the oscillations-generated.

'5. In asystemfor generating high frequency oscillations andmodula'ting the frequency of the oscillations generated, a pair of electron discharge devices having input and output electrodesicou- .pled in oscillation generating and frequency determining circuits including, a frequency controlling line, anadditionalfrequency controlling line coupled to saidfirst named line, an electron discharge coupling tube having input and :output'electrodes, means coupling theoutput 3619C- trodes of said tube to points on said second line, means for impressing voltages from one of said generator circuits on the input electrodes of said tube, and means for modulating the impedance of the tube at signal frequency to therebymodulate the phase of the voltages fed to said second line to vary the reactance of said firstline- '6. In a system for generating highfrequency oscillationsand modulating the frequencyofthe oscillations generated, an electron discharge device having input and output electrodesicoupled in oscillation generating and frequency determining circuits including a frequency controllingline, an additional frequency controlling linecoupled to said first named line, pairs of electrondischarge coupling tubes, each of said pairs of tubes having input and output electrodes, means coupling the output electrodes of the pairs of tubes together and to points on said second line, means for impressing voltages from one of said generator circuits in phase displaced relation on'the input electrodes of'each tube of said pairs, and means for modulating the impedances of the tubes of each pair in phaseopposition 'at signal frequency to thereby modulate the phase'ofthe voltagesfed to said second line to vary there- ,actance of said first line.

7. In a system for generating high frequency oscillatory energy and modulating the frequency thereof, an oscillator comprising, an electron discharge device having input and output electrodes coupled in oscillation generating and frequency controlling circuits including a resonant circuit having inductance and capacity, an additional resonant circuit coupled to said first namedresonant circuit, means for feeding wave energy from one ofsaid oscillation circuits to saidadditional resonant circuit, and means. for varying the phase of the energy so fed to said additional resonant circuit; at signal frequency to thereby vary the phase of the coupling between said resonant circuits to vary the reactance of said first resonant circuit and the frequency of the oscillations generated.

8. In means for generating high frequency oscillatory energy and modulating the frequency thereof, an oscillator comprising, an electrondischarge device having input and output electrodes coupled in oscillation generating and frequency controlling circuits including a resonantjcircuit, an additional resonant circuit coupled to, said first named resonant circuit, electron discharge tube means for feeding Wave energy from one of said oscillation circuits to said additional resonant circuit, and means modulating said tube means at signal frequency for varying the phase of the energy so fed to said additional resonant circuit at signal frequency and varying the'phase 0f the coupling between said resonant circuits to vary the reactance ofsaid first resonant circuit and the frequency of the oscillations generated,

v9. In .a system forgenerating high frequency oscillationsand modulating the frequency of the oscillations generated, a pair of electron discharge devices having input and output electrodes coupled in oscillation generating and frequency determining circuits including, a frequency controlling circuit exhibiting parallel resonance, an additional circuit exhibiting parallel resonance coupled to said frequency controlling circuit, an electron discharge coupling tube having input and output electrodes, means coupling the output electrodes of said tube to points on said additional circuit, means for impressing voltages from one of said generator circuits on the input electrodes of said tube, and means for modulating the impedance of the tube at signal frequency to thereby modulate the phase of the voltages fed to said additional circuit to vary the reactance of said frequency controlling circuit.

10. In a system for generating high frequency oscillations and modulating the frequency of the oscillations generated, an electron discharge device having input and output electrodes coupled in oscillation generating and frequency determining circuits including a resonant circuit, an additional circuit having inductance and capacity coupled to said resonant circuit, pairs of electron discharge coupling tubes, each of said pairs of tubes having input and output electrodes, means coupling the output electrodes of the pairs of tubes together and to said additional circuit, means for impressing voltages from one of said generator circuits in phase displaced relation on the input electrodes of each tube of said pairs, and means for modulating the impedances of the tubes of each pair in phase opposition at control frequency to thereby modulate the phase and amplitude of the voltages fed to said circuit having inductance and capacity to thereby vary the frequency of oscillation of said resonant circuit.

11. A variable frequency system comprising a pair of electron discharge systems connected in push-pull to a frequency determining system having inductance and capacity, a pair of electron discharge control systems each having a control grid and an anode, a coil inductively coupled to and deriving waves from said pushpull connected system and feeding said waves in push-push to the control electrodes of said discharge control systems, means for feeding control voltages in push-pull to the control grids of said discharge control systems, and means for coupling the anodes of said control systems to points of opposite instantaneous high frequency voltage in said frequency determining system having inductance and capacity.

12. A transmitter comprising in combination, a. push-pull connected electron discharge tube oscillation generator having a frequency determining system having inductance and capacity, a coil inductively coupled to said oscillation generator, a pair of electron discharge control systems each having a plurality of electrodes, means coupling said coil to electrodes of said control systems to vary the impedance of said electron discharge control systems cophasally with waves derived from said oscillation generator, means for oppositely varying the impedance of said discharge control systems with signal modulation voltages, means coupling output electrodes of said control systems in phase opposition to the frequency determining system of said oscillation generator to thereby vary the frequency of oscillations generated by said generator, and an output circuit coupled to said generator for transmitting said oscillations of varied frequency.

13. A variable frequency system comprising an electron discharge oscillating system connected to a frequency determining system having inductance and capacity, a pair of electron discharge control systems each having a control grid and an anode, means for deriving waves from said oscillating system and feeding said waves in push-push to the control electrodes of said control systems, means for feeding control voltages in push-pull to the control grids of said control systems, and means for connecting the anodes of said control systems to points of opposite instantaneous high frequency voltage in said frequency determining system having inductance and capacity.

14. In combination, an electron discharge tube oscillation generator having a frequency determining system having inductance and capacity, a pick-up coil loosely coupled to said oscillation generator, 2. pair of electron discharge control systems each having a plurality of electrodes, means connecting said coil to electrodes of said control system to vary the impedance of said I control systems cophasally with Waves derived from said oscillation generator, means for oppositely varying the impedance of said discharge control systems with control voltages, and means connecting output electrodes of said control systems in phase opposition to the frequency determining system of said oscillation generator.

15. A variable frequency system comprising a pair of electron discharge systems connected in push-pull to a frequency determining system having inductance and capacity, a pair of electron discharge control systems each having a control grid and an anode, a coil for picking up Waves from said push-pull connected system and feeding said waves in push-push to the control grids of said control systems, means for feeding control voltages in push-pull to the control grids of said control systems, means for connecting the anodes of said control systems to points of opposite instantaneous high frequency voltage in said frequency determining circuit having inductance and capacity.

16. In combination, an electron discharge tube oscillation generator having a high frequency circuit consisting of a coil and a condenser connected in parallel, a pick-up coil loosely coupled to said circuit, a pair of electron discharge control systems each having a plurality of electrodes, means connecting said pick-up coil to electrodes of said control systems to vary the impedances of said control systems in phase opposition with waves derived from said circuit consisting of a coil and a condenser connected in parallel, means for oppositely varying the impedance of said control system with control voltages, and means connecting output electrodes of said discharge control systems directly together and to said oscillation generator.

17. A variable frequency system comprising an electron discharge oscillator system having connected thereto a frequency determining system having inductance and capacity, a pair of electron discharge control systems each having a control electrode and an anode,.means for picking up waves from said oscillator system and feeding said waves in push-push to the control electrodes of said control systems, means for feeding control voltages in push-pull to the control electrodes of said control systems, and means for coupling the anodes of said control systems in opposition and to said frequency determining circuit having inductance and capacity; a second pair of electron discharge control systemsvarying the impedances of said second pair of control systems with control voltages, and

means coupling-output electrodes'of said second pair of control systems in phase oppositionand to the frequency determining system of said oscillation generator.

18. In combination, an oscillation generator having a frequency controlling system, a' frequency varying arrangement for said oscillation generator comprising a pair of electron dis charge tubes each having an anode, a cathode and a grid, means for'feedingwaves from said oscillation generator cophasally to the'grids of said tubes, means for feeding control waves in phase opposition to the grids of said tubes, and means for coupling the anodes of said'tubes to points of opposite instantaneous highfrequency' potential in said frequency controlling'system whereby the frequency of oscillations generated by said generator is varied'bysaid control waves;

19. In combination, an oscillation'generator havin a frequency controlling system; a frequency Varying arrangement for said oscillation generator comprising a pair of electron discharge tubes each having an anode; a cathode and a grid, means for feeding Waves from said oscillation generator cophasally to the grids'of'said tubes, means for feeding control waves in phase opposition to the grids of said tubes, and means for coupling the anodes-of -said tubes in phase opposition to said frequency controlling system;

20. In combination, an oscillation generator having a'frequency control-ling system, a frequency varying arrangement for said oscillation" generator comprising a pair of electron discharge paths each having electron emitting, control and electron receiving electrodes, means for feeding waves from said oscillation generator cophasally to like control electrodes of said paths, means for feeding control waves in phase opposition to like control electrodes of said paths, and means'for connecting the electron receiving electrodes of said paths to points-oi opposite instantaneous high frequency potential in said frequency determining .system.

21. In combination, an oscillation generator having a frequency controlling system, a frequency varying arrangement for said oscillation generator comprising a pair of electron discharge paths having electron emitting, control and electron receiving electrodes, means for feedingwaves from said oscillation generator cophasally to like electrodes of said paths, means for feeding control waves in phase opposition to like electrodes of said paths, and means for coupling the electron receiving electrodes of said paths in phase opposition to said frequency determining system.

22. In combination, a push-pull connected electron discharge tube system having a frequency controlling system having inductance and capacity connected to the control electrodes of the tube system, a coil coupled to said oscillation generator, a pair of frequency control tubes each having electrodes including an anode and having their anodes connected in phase opposition and coupled-to said frequency controlling system hav-- ing inductance and capacity, and meansforfeeding-Waves picked up by said-coil cophasally to contubes of said generator, a coil coupled to'said tuned plate circuit, -a pair of control tubes each having an anode, a cathode, and a grid, means for exciting the grids of said control tubes in phase opposition with modulating voltages, means exciting the grids of said control tubes cophasally with'waves picked up by said coil, and means coupling the anodes of said tubes in phase opposition to a circuit of said push-pull connected oscillation generator.

24. In combination, a pmh-pull connected electron discharge tube system having a frequency controlling system having inductance and capacity connected to the control electrodes of the tube system, a coil loosely coupled to the output circuit of said oscillation generator, a pair of frequency control tubeseach having electrodes including an anode and having their anodes connected in phase opposition and to said frequency control circuit having inductance and capacity, means-for feeding waves picked up by said coil cophasally to control electrodes of said control tubes, and means for applying modulating voltages in phase opposition to control electrodes of said control tubes, whereby the frequency of waves generated by the push-pull generator is varied.

25. In combination, a vacuum tube oscillation generator having a parallel tuned output circuit, a coil coupled to said tuned circuit, a pair of control tubes each having an anode, a cathode and a grid, means for exciting the grids of said control tubes in phase opposition with control voltages, means exciting the grids of said control tubes cophasally with waves picked up by said coil, and means coupling the anodes of said tubes in phase opposition to a circuit of said oscillation generator.

26. In combination, a push-pull connected electron discharge tube system having a frequency controlling system having inductance and capacity connected to the control electrodes of the tube system, a coil coupled to said oscillation generator, a pair of frequency control tubes each having an anode and a control electrode and having their anodes connected in phase opposition and coupled to said frequency control circuit having inductance and capacity, and means for feed.- ing waves picked up by said coil cophasally to the control electrodes of said control tubes, means for applying modulating voltages in phase op- I position to the control electrodes of said control tubes, a second pair of control tubes each having an anode, a cathode and a control electrode, means for exciting the control electrodes of said secondpair of control tubes in phase opposition with control voltages, means exciting the control electrodes of said second pair of control tubes charge systems having output electrodes coupled in phase opposition and to said frequency controlling system having inductance and capacity, means for feeding waves from said generator system cophasally to like electrodes of said discharge control systems, means for applying control voltages in phase opposition to like electrodes of said pair of control discharge systems, a second pair of control discharge systems, means for exciting like electrodes of said second pair of control discharge systems in phase opposition with said control voltages, means exciting like electrodes of said second pair of control discharge systems cophasally with waves from said generator system, and means coupling the output electrodes of said second pair of control discharge systems in phase opposition and to said oscillation generator, the cophasal excitation of said second pair of discharge systems being in opposition to the cophasal excitation of said first pair of electron discharge systems.

28. In combination, a regenerative oscillation generator having a parallel resonant circuit comprising a coil and a condenser connected in parallel, a circuit loosely inductively coupled to said parallel resonant circuit and constituting a first source of control voltage, a pair of electron discharge paths each having electron emitting and electron receiving electrodes, a second relatively low frequency source of control voltage, means applying said voltages to said electron paths whereby one source varies the conductivity of said paths cophasally and the other source varies the conductivity of said paths in phase opposition, and means coupling the electron receiving electrodes of said paths to a frequency controlling circuit of said regenerative oscillation generator for feeding waves of reversed phase and varied amplitude to said frequency controlling circuit, the phase of the waves so fed depending upon the polarity of the control voltages of relatively low frequency and the amplitude of the waves so fed depend upon the amplitude of the said relatively low frequency control voltage, whereby the frequency of oscillations generated by said generator changes in direction an amount in accordance with the polarity and amplitude, respectively, of the relatively low frequency control voltage applied to said electron discharge paths.

29. In combination, an oscillation generator having a frequency controlling system having inductance and capacity, a frequency varying arrangement for said oscillation generator comprising a pair of electron discharge systems, means for feeding Waves from said generator to said discharge systems to vary the conductivity thereof cophasally, means for feeding control waves to said discharge systems to vary the conductivity thereof in phase opposition, and means for feeding the outputs of said discharge systems in phase opposition to said frequency controlling system to vary the frequency of oscillations generated by said generator in accordance with the control Waves fed to said discharge systems.

30. A transmitter for transmitting waves varied in frequency in accordance with a signal to be transmitted as distinguished from waves varied in amplitude by a signal comprising, in combination, a high frequency oscillation generator having a frequency controlling system having inductance and capacity, a frequency varying arrangement for said oscillation generator comprising a pair of electron discharge systems, means for feeding waves from said generator to said discharge systems to vary the conductivity thereof cophasally, means for feeding waves of signal frequencies to said discharge systems to vary the conductivity thereof in phase opposition, means for feeding the outputs of said discharge systems in phase opposition to said frequency controlling system to vary the frequency of oscillations generated by said high frequency generator in accordance with the signaling waves fed to the said discharge systems, and an output circuit coupled to said high frequency generator for transmitting therefrom the modulated waves of varied frequency.

31. In combination, an oscillation generator having a frequency controlling system having inductance' and capacity, a frequency varying arrangement for said oscillation generator comprising a pair of electron discharge systems, means for feeding Waves from said generator to said discharge systems to vary the conductivity thereof cophasally, means for feeding control waves to said discharge systems to vary the conductivity thereof in phase opposition, and means for feeding the outputs of said discharge systems in phase opposition to said frequency controlling system to vary the frequency of oscillations generated by said generator in accordance with the control waves fed to said discharge systems, a second pair of electron discharge systems, means for feeding waves from said generator to said second pair of discharge systems to vary the conductivity of the second pair cophasally, but in phase opposition with respect to the first mentioned pair, means for feeding control waves to said second pair of discharge systems to vary the conductivity thereof in phase opposition, and means for feeding the output of said second pair of discharge systems in phase opposition to said frequency controlling system.

32. A transmitter for transmitting frequency modulated waves comprising, in combination, a vacuum tube high frequency oscillation generator having a parallel tuned output circuit, a coil inductively coupled to said tuned circuit, a pair of control tubes each having an anode, a cathode and a grid, means for exciting the grids of said control tubes in phase opposition with signal modulation voltages, means exciting the grids of said control tubes cophasally with waves induced in said coil, means coupling the anodes of said tubes in phase opposition to a circuit of said oscillation generator whereby the frequency of said generator is varied in direction in accordance with the polarity of said signal voltages and in amount in accordance with the amplitude of said signal modulation voltages, and an output circuit coupled to said generator for transmitting the frequency modulated output thereof.

33. A transmitter for generating and transmiting waves varied in frequency in accordance with'signal voltage waves comprising an oscillation'generator having a frequency controlling system, a frequency modulating arrangement for said oscillation generator comprising a pair of electron discharge tubes each having an anode, a cathode and a grid, means for feeding waves from said oscillation generator cophasally to the grids of said tubes, means for feeding signal voltage waves in phase opposition to the grids of said tubes, means for coupling the anodes of said tubes to points of opposite instantaneous high frequency potential in said frequency controlling system whereby the frequency of oscillations generated by said generator is varied by said signal voltage Wave, and an output circuit coupled to said generator for transmitting the frequency modulated wave output thereof.

34. A transmitter for transmitting waves varied in frequency by signaling voltage waves comprising, an electron discharge tube oscillation generator having a high frequency circuit consisting of a coil and a condenser connected in parallel, a pick-up coil loosely coupled to said circuit, a pair of electron discharge control systems each having a plurality of electrodes including an output electrode, means connecting said pick-up coil to electrodes of said control systems to vary the impedances of said control systems in phase opposition with waves derived from said circuit consisting of a coil and a condenser connected in parallel, means for oppositely varying the impedances of said control systems with signal voltages, means coupling the output electrodes of said discharge control systems directly together and to said oscillation generator, and an output circuit coupled to said oscillation generator.

35. A high frequency transmitter comprising, in combination, an electron discharge tube high frequency oscillation generator having a frequency determining system having inductance and capacity, a pair of electron discharge control systems each having a plurality of electrodes including an output electrode, means coupled to said generator and to electrodes of said control systems to vary the impedances of said control systems cophasally with Waves derived from said oscillation generator, means for oppositely varying the impedances of said discharge control systems with signal modulating voltages, means connecting the output electrodes of said control systems in phase opposition to the frequency determining system of said oscillation generator, and an output circuit coupled to said oscillation generator.

NILS E. LINDENBLAD.

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