US1442146A - Modulating and transmitting system - Google Patents

Description

Jan. 16, 1923. 1,442,146. R. A. HEISING.

MODULATING AND TRANSMITTING SYSTEM- HLED APR. 13, 1918.

Patented Jan. 16, 1923'.

UNITED, STATES 1,442,146 PATENT OFFICE.

RAYMOND A. HEISING, EAST ORANGE, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

Application'filed April 13, 1918. Serial No. 228,416.

1'0 all whom it may concern:

Be it known that I, RAYMoNn-A. HEISING, a citizen of the United States, residing at East Orange, in the-county of Essex and State of New Jersey, have invented certain new and useful Improvements in Modulatinq and Transmitting Systems, ofwhich the following is a full, clear, concise, and exact description. r

This invention relates to means for generating, modulating and'transmitting electrical oscillations, and more particularly to generating oscillations by means of electrical discharge devices.

An object of the invention is to effect an improvement in the manner in which electrical discharge devices may be associated in signaling and other systems.

Another object is to provide a system in which a plurality of electrical discharge devices are associatedwith suitable circuits to act as oscillation generating means.

' Further objects are to produce a signaling system with which modulated and unmodulated signals may be sent, and in which a vacuum tube oscillates directly into an antenna. a

The invention is exemplified herein in a radio signal transmitting system wherein the antenna itself is included in and forms a frequency-determining element of a highfrequency oscillating circuit, and is directly associated with a vacuum tube oscillator ,or a series ofvacuu'ni tubes acting as an oscillator. The oscillation frequency is determined by the circuit which includes the antenna. Vacuum tubes for modulating have been provided to efiect the signaling modulation of the oscillations to be transmitted.

In the accompanyin drawings 1 represents diagrammatica ly a form 0 he invention adapted to be used as a radio telephone transmitting station; Fig. 2 is a modified form of that part of Fig. 1 to the right of the line X-X and Figf3 is a circuit arrangement adapted for telegraphy.

i The general organization as shown in Fig, 1 includes an oscillator and a modulator therefor which is controlled by a 'micro phone. In detail, the antenna circuit 1 con-. sists of the aerial 2, inductance coil 3, condenser 4, which is connected to ground at G. Adjustment of condenser 4 causes the alternating voltage impressed upon the grid to be varied. Coil 3 has an adjustable connection to the plate ot'the oscillating tube O through conductor 5. Conductor (S connects the lower end of coil 3 to the grid of tube 0 through stopping condenser 7. Conductor 6 may be adjustably connected to coil 3, as shown in dotted lines. it it is desired to use this means of regulating the feed-back coupling ot' the oscillator instead of varying condenser 4f. Leak resistance 8 of a large'numerical value, is provided to allow an excess negative charge to leak from the grid of tube 0, and resistance 9 is adjustably connected to resistance 8 and to the gridof tube M through conductor 10, for applying a suitable average value of negative potential to the grid of the tube M. The source of electrical energy E which may be any suitable source and is here represented as a battery, furnishes plate-filament current for both the tubes and M which passes through the large choke coil 11 having an iron core. (oil 11 tends to keep the current through itself constant and thus any variation of internal impedance of the tube M affects the potential between the anode and cathode of the tube 0. The connection from coil 11 to the plate of tube 0 includes high frequency choke coil 12, conductor 13, coil 3.

and conductor Since coil 11 consists of many turns it will have considerable capacity reactance at high frequencies, which would tend to act as a shunt upon the capacity 4, and the function of the coil 12Iis to make inductive reactance predominate and prevent short-circuiting of condenser 4. The coil 12 is a radio frequencyinduction coil and necessarily has small distributed capacity in order to make inductive reactance predominate in the circuit at high frequencies. It is well known that such coils may be constructed ot a single layer of spaced turns, but other constructions may be used. Battery E, heats the filamentary cathodes of both tubes, being connected to conductors 14 and 15, while the conductor 16 grounds the negative terminals of both batteries. Microphone 17 is connected to the tube M through transformer 18 whose secondary is connected across the resistance 19, one end of which is connected to the grid or control electrode of the modulator M, and the other to the filament or cathode through conductor 10, capacity 20 and conductors 21 and 15. The capacity-2O is .of low impedance to speech frequency currents as compared withthe rid-to-filamentjmpedance of the tube M. he input circuit of the tube M may be considered as including the arran ement constituting the capacity in para el with the resistance 9 and a part of resistance 8. This arrangement avoids the necessity of providing a grid battery for the tube M.

In operation, variations of potential of sound or speech frequency are impressed upon the grid of tube M which cause variations in its internal impedance. As coil 11 tends to maintain constant current through itself, there will be variations of anodecathode potential across the continuously oscillating tube 0, which will cause its oscillationsto be modulated in amplitude in accordance with the fluctuating potentials induced by microphone '17.

The arrangement of Fig. 2 may be sub-- stituted for that part of Fig. 1 which 'lies to the right of the line X-X and. is designed to prevent the positive terminal of the battery 15 from being directly connected to the antenna. This is accomplished by having conductor 13 connected to conductor 5 instead of to conductor 6, as in Fig. 1. A capacity 22 is then placed between the junction point of conductors 5 and 13 and the coil 3. dental grounding of the antenna 2, such as might occur if this system is used on aeroplanes or'boats, would not short-circuit the battery E This arrangement has the additional important advantage that the electromotiv force' of speech frequency which is impressed across the anode-cathode terminals of the tube 0 is not materially shunted through the circuit comprising ca: pacity 22, coil 3 and capacity 4, since two small condensers (as regards speech frequencies) are included therein. This prevents waste of energy and also causes the impedance offered by the circuit comprising elements 22, 3 and 4 to highspeech frequencies to be almost the same as to low speech frequencies. This circumstance causes the impe ance across the anode-cathode terminals of the'oscillator to be .substan-;

tially the same for the entirekrange of speech frequencies and therefore produces In the case where the modulating frequency or frequencies im-' better modulation.

pressed upon the generator 0 are other than speech frequencies, as in Figure 3, the requirements are somewhat similar since, al-- though the modulating wave mayconsist "of a single frequency or av narrow .band of frequencies, it may differ from the high frequency by a. smaller percentage thanin e case of speech modulation. V The transmitting system .shown in Fig. 3

' is intended for transmitting both modulated and unmodulated telegraphic signals, al-

WVith this arrangement, acci closely analogous to that of Figs. 1 and 2,

and the parts which bear identical reference characters can be identified by referring to the preceding description. A low frequency oscillator O and a series of modulators M are combined with a series of tubes 0 which constitute a high frequency oscillating system, the tubes 0 being arranged in parallel. A filter 23 in the condu'ctor 5 consists of an adjustable capacity and an inductance and is tuned to a frequency approximating that of the low frequency oscillator O to prevent low frequency oscillations from passing along conductor-13 to the grids of tubes 0 through the coil 3, capacity 7 and conductor 6. The condenser 22 also aids in preventing such action. The low frequency oscillator O has an oscillation circuit consisting of variable capacity 24 and inductances- 25 and 26. Stopping condenser 27 is also included in .the oscillation circuit. Stopping condenser the inductance 26 which changes the fre quency of oscillator .O'. Oscillations generated by the tube 0' cause corresponding v changes of potential and of space current across the tubes M which serve to modulate the high frequency oscillations generated by tubes 0 in the same manner in which the tube M in Fig. 1 operates. It will be noted that the source of current E and choke coil 11 are common to the circuit of tubes capacity that high frequency will pass there- M and O in both figures. Resistance 30 may be provided to cause tube 0' to work at a' lower plate-filament potential than tubes M and O. The resistance 30 also serves to stabilize the output of tube 0 and to eliminate harmonics.

Referring again to the antenna, the capacity 31 may be in shunt with the aerial capacity and serves as a convenient means of tuning and adjusting the antenna capacity, and hence the frequency. Capacities 31 and 32are not essential features ofthe invention and either or both of them may be omitted without. rendering the circuit inoperative. Condenser .32 may bev omitted,

but if present must be of sufficiently large through readily. It will prevent either tel.-

- minal of the battery system from being.

grounded, in which case an accidental,

ground on either the aerial or some other part of the system will not short-circuit the battery. This feature is of utility in systems used upon aeroplanes or boats. Condenser 32 also aids the filter 23 in preventing the relatively low frequency electromotive force impressed across the anodecathode terminals of the tube 0 from being shunted through or impressed upon the aritenna circuit. Capacity 4 consists of adjustable capacity 4: in series with the large capacity 4*, which latter is shunted by key 'K.

Suitable switches 8 may be provided to cut off the .current supply from the battery system.

This system 1s capable of operating in two distinct ways. If the oscillation system 0 is working at a normal frequency of, for example, 100,000 cycles, and key K is closed, the frequency will change to, for example 99,000 cycles if the adjustments are proper. At a suitable receiving station a local generator having a suitable frequency will give a heterodyne beat note when key K is closed, and a different or inaudible note when key K is open.' This action will be independent of the action of tubes 0' and M which may meanwhile be left either operative or inoperative.

. Suppose, however, the generation system including tubes 0 is operating at a frequency.

of 100,000, and generator O'at a frequency of 15,000 cycles. When key K is closed, the frequency of generator 0' will change to, for example, 14,000 cycles. In this case the waves may be receive-d at a receiving station having'a detector for deriving the lower fre quency from the modulated wave and asuitable heterodyne local source of oscillations of proper frequency.

While certain specific modifications have been illustrated herein and described in de tail, the invention is capable of embodiment in various physical forms, and the appended claims are intended to include all equivalent arrangements, or where only a .group of ele ments is defined in the claims, it is intended to include the use of such group in any equ1v-.

alent system. While radio systems only have been described herein to illustrate the invention, systems employing wires might also have been used as illustrations; Since, under certain circumstances, it may be' desirable to modulate oscillations at a receiving stat-ion or elsewhere, as'well -as at a transmitting station, it is not'intended to limit thi or other features of the invention to use for transmitting.

What is claimed is:

1. In a radio signaling system, an antenna circuit, a vacuum tube, an anode and a conducting element in'said tube, means forimpressing a low frequency-voltage between said anode and said element, a conductor connecting said anode to said antenna circuit, and a'plurality of elements constituting a low frequency filter located in said conductor for preventing the flow of current therethrough due to said voltage.

2. In a radio signaling system, an antenna circuit, adischarge tube, an anode therein, a conductor. connecting said anode to said antenna circuit, said conductor and a portion of said antenna circuit constituting a'shunt path to said tube with respect to a source of modulating waves, and an impedance means located in said conductor constituting a high impedance to relatively low frequencies for tor, a second oscillation generator, said gen- 3 erators each including a vacuum tube having electrodes therein, alternating current input, output and feed-back circuits for said generators, means whereby the oscillations of the second generator may be modulated in accordance with the oscillations of the first mentioned generator, said means including a plurality of conductive connections between electrodes of different of said tubes.

5. In combination, an oscillatlon generator, a second oscillation generator, said generators each including a discharge device having a plurality of electrodes, alternating current input, output and feed-back circuits for said generators, and means whereby the oscillations of one of said generators may be modulated in accordance with the oscillations of the other, said means including conductive. connections between said electrodes. 6. In combination, an oscillation generator, a second oscillation generator, means whereby the oscillations of the second generator may be modulated in accordance with the oscillations of the first mentioned generator, means whereby theoscillations of one of said genera-tors may be varied tosignal, and means whereby the oscillations of the other of said generators may be independentlyvaried to signal.

7. A modulating system comprising a source of electrical waves, means for causing an interaction between the waves from said source and other waves to produce modulated waves, said source and said means each 1nclud-1ng a space discharge device having a cathode and an impedance varying element,

-a leak path, conductive to direct current extending from one of said cathodes to the corresponding impedance varying element,

c and a tap connection conductive to direct current extending-from a point on said path to the impedance'varying element of the other said space discharge device.

8. In a signaling system, a low frequency vacuum tube oscillator associated with a high frequency vacuum tube oscillator, means for varying the frequency of each of said oscillators, means for operatively connecting said oscillators so that a change of frequency of either will have anegligible effect upon the oscillation frequency of the other, and means for causing a characteristic of the oscillations of one of said generators to change in accordance with the oscillations of the other.

9. In combination, a discharge tube, an antenna circuit directly associated with said tube so as to determine the frequency of oscillation thereof, a set of modulating tubes operatively associated with said first mentioned tube, and a control tube operatively associated with said modulating tubes.

10. In a transmitting system, an oscillating means, a modulating means capable of oscillating 'at two constant frequencies, and means for signaling by intermittently causing said modulating means to oscillate at each of saidfrequencies.

11. A source of high frequency oscillations, a plurality of space discharge devices associated therewith so that the internal im pedance of-said devices determines a characsaid electrode, a lead from a point on said path to the control element of an electron discharge device for maintaining a given average working potential on said secondmentioned control element, and a condenser connecting a point in said lead and .said electrode.

13. In an electrical system, .a series arrangement of impedance elements adapted to have high impedance at a relatively low range of frequencies and high impedance at a relatively high range of frequencies comprising an inductance coil having a magnetic core for producing the desired high impedance at the low range of frequencies, and an inductance coil in series therewith having sufficiently high impedance at the relatively high range of frequencies to more than counteract the capacity effect of the first named coil at the high range of frequencies and thereby produce the desired high impedance.

,14. In an electrical system, a series arrangement of impedance element: havin relatively high impedance at a high range of frequencies and relatively high impedance at a low range of frequencies and being conductive to direct current comprising a choke coil having the desired high impedance at the low range of frequencies but having a capacity effect sufiicient to produce a relatively low impedance at the high range of frequencies, and an inductance coil in series therewith having suflicient inductive reactance at the high range of frequencies to produce the desired high impedance.

15. In an electric system, a circuit, aninductive impedance means therein for maintaining a-constant direct current in a part of said circuit, said impedance means having a capacity reactance at high frequencies, and an inductance coil in said circuit to counteract said capacity reactance.

16. In combination in a transmitting system, an antenna including an aerial, an inductance and a capacity, a vacuum tube oscillating system connected to said antenna, a

cathode, an anode and an impedance-varying element included by said oscillating system, said cathode, anode and impedance-varying element being connected to points of normally different potential in said antenna when the system is operating; a vacuum tube modulating system for said oscillating system, an anode, a cathode and an impedancevarying element in said modulating system, a space current path in said modulating system and a space current path in said oscillating system, said paths being in parallel with respect to a source of electromotive force, a circuit in which saidsource is located, and means in said circuit for maintaining the sum of the space currents in said paths constant, a second oscillating vacuum tube system associated with said modulating system for causing variations of impedance of a conductive part thereof, an oscillating circuit for said second system, and means for controlling the constants of said oscillating circuit. 7

'17. An electron discharge system having a control element, a second electron discharge system, and means whereby said control element is maintained at a suitable average working potential by said second systein; said means including an input path for said first-mentioned system; said input path including at least a portion of a leak path of said second system, a shunt path to said portion, and means for reducing the reaction of said first system on said second system due to varying potential differences across said shunt ath. 18. system comprising an electron discharge oscillator, means including an electron discharge device having an impedance varying element and a cathode for causing said oscillator to produce modulated waves, and'means including conductive connections 'tential with respect to said cathode.

19, The combination in an electricaLcircuit of means for producing a high impedance at a relatively low range of frequencies and a high impedance at a relatively high range of frequencies comprising a highly inductive choke coil having a large number of turns and a large inherent and undesired distributed capacity between said turns with an inductance coil of small distributed ca-' pacity to more than compensate forthe capaclty reactance of said choke coil at high frequencies and thereby produce the desired impedance at the high range of frequencies.

20. In a signal transmission system the combination of a source of low frequency variations, a sourceof high frequency variations, and means to impress said low frequency variations upon said high frequency source without impressing said high frequency variations upon said low frequency source comprising a highly inductive low frequency choke coil in shunt with said high frequency source as viewed from said low frequency source, and a high frequency choke coil in series with said low frequency source as viewed from said high frequency source.

21. In combination, an electrical system including a discharge device and means to vary the impedance thereof at a relatively low frequency rate, a second discharge device and means to vary the impedance thereof at a'relatively high frequency rate, a low frequency choke coil in parallel with said second device as viewed from said first device, and a high frequency choke coil to counteract the effect of the distributed capacity of said low frequency choke coil located in series with said low frequency, choke coil as viewed from said second discharge device.

22. A modulating system comp-rising avariable impedance, a source of constant current supply, a high frequency generator in parallel with said impedance with respect to said source of supply, means for varying the impedance of said impedance device at signal frequencies, a shunt path around said generator comprising means whereby the impedance of said path for currents ofthe signal frequencies is rendered large 'compared to the impedance of said generator.

23. A modulating system comprising a variable impedance, a source of constant current supply, a high frequency generator in parallel with said impedance as viewed from said source, means for varying the im-' pedance of said impedancedevice at a plurality of signaling frequencies, and a shunt path around said generator comprising means whereby the impedance of saidpath is rendered negligibly different for currents of the various signaling frequencies.

24. A circuit including three vacuum tube systems, each system having a grid circuit and a plate circuit, connections between the grid circuit of the first system and the grid circuit of the second system whereby the first acts upon the second, and connections between the plate circuit of the secondand the plate circuit of the third whereby the second acts upon the third, said connections including an impedance element across which differences of potential are produced by the second mentioned system and impressed upon the plate circuit of the third mentioned system.

25. A transmitting circuit comprising three vacuum tube systems, a cathode; an anode and a control element for each system, a grid-to-grid and cathode-to-cathode connection bet-ween the first and the second system for supplying from said first to said second system, an anode-to-anode and cathode-to-ca-thode connection between the second and third systems, and a shunt path containing an impedance element connected across said last mentioned connections.

26. A discharge device for generating oscillations having an anode, a cathode and an impedance control element, a second discharge device connected thereto by means whereby it varies a generating characteristic an anode, a cathode and an impedance control element, and a common means for applying to each control element an average potential different from the potential of the associated cathode.

27. A discharge device for generating oscillations having an anode, a cathode and an impedance control element, adischarge device for varying a generating characteristic of said first mentioned device including an anode, a. cathode and an impedance control element, a leak path between the control element and the cathodeof said first mentioned device, and means for applying between the control element and the cathode of the second mentioned device a portion of the potential difference across said leak path.

28. In an "electrical system, a series arrangement of elements for producing relatively high impedance at a low range of frequencies and relatively high impedanceat a high range of frequencies comprising an inductive winding having high 1m- .pedance to low frequencies but low imbut low impedance to higher;

frequencies due to capacity effect, and means for causing a series circuit including said winding to have high inductive reactance to both. high and low frequencies without causing the impedance to direct current and low frequencies to be substantially greater than the impedance of said winding comprising an inductive winding in series circuit relation with said first mentioned Windthrough said connections to said source.

A through said source of modulating waves.

31. A source of modulating Waves comprising a thermionic device and means for varying its impedance at a modulating wave frequency, means including a second thermionic modulating device for; producing carrier waves modulated by waves from said source, circuit connections between said devices, and an impedance element of relatively low impedance to said modulating waves but of relatively high impedance to said carrier waves to prevent the passage of currents of the carrier wave frequency 32. In combination, a plurality of connected systems, one of said systems including a device for producing modulated car-- rier frequency waves and the other of said systems being a discharge device including an anode, a cathode and a control element, means for varying the impedance of the discharge device at 'a frequency lower than the carrier frequency, andmeans for preventing currents of the carrler frequency from being impressed on sald discharge device While allowing currents of said lower frequency tion in the plate circuit of the first device .lations, a second electron discharge device having a cathode, an anode and a grid and to be impressed from said discharge device 5 upon said device for producing modulated Waves.

33. In a'high frequency system, a space discharge device having an anode, a cathode and a control element, means for varying the impedance of said device-at a carrier frequency, a second space discharge device having an anode, a cathode, and a control element, means for varying the impedance of said second device at a modulating frequency, a source of current for supplying said devices, means for maintaining the sum of the supplied currents constant as regards modulating frequency variations, and a common means for heating both of said cathodes.

34. A high frequency signalling system provided with an electron discharge device having a cathode, an anode and a grid and having plate and grid circuits coupled together to produce radio frequency 0scilla-. tions, a second electron discharge device having a cathode, an anode and a grid for producing an audio frequency potential variaand-means for impressing a radio frequency current from the first device upon the grid circuit of the second device to maintain a negative potential upon the grid of 'the second device;

35. A high frequency signalling system provided With an electron discharge device having a cathode and anode and a grid, and having plate and grid circuits coupled together to produce radio frequency oscila grid circuit forproducing an audio frequencypotential variation in the plate circuit of the first device, and a condenser shunted by a resistance forming a part of the. grid circuit of the first device, a part at least of said resistance being included in the grid circuit of the second device.

In witness whereof, I hereunto subscribe 95.

my name this 9th dayof April A. 1)., 1918.

RAYM-oiu) A. HEIsINe;

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