US1628905A - Wireless telephone system - Google Patents

Description

May v 17 1927. 1,628,905

A. NYMAN.

WIRELESS TELEPHONE SYSTEM Filed Sept. 2, 1921 8 Q w & N

--'\ WITNESSES: \v I INVENTOR i I iiamadmfl /wiid Patented May 17, 1927.

UNITED STATES.

1,628,905 PATENT OFFICE.

ALEXANDER NYMAN, or w'mxlnsnono, rnnnsvnvaum, assrenon 'ro wnsrmenoosn nnnc'mro a umraoronmo COMPANY, A CORPORATION or PENNSYL- VAHIA.

WIRELESS TELEPHONE SYSTEM.

Application filed September 2, 1921. Serial No. 497,951.

My invention relates to wireless systems and more especially to wireless telephone modulating systems.

Broadly speaking, the ob ect of my invention is to provide an improved system of modulation for use in connection with wireless telephonesystems, whereby the trans mission of speech by electromagnetic waves may be more readily eflected.

More specifically, one object oi my inven tion isto provide a modulating system which is applicable to wireless telephone systems radiating relatively large amounts of power.

Another object of my invention is to provide a modulating system of such characteristics that the microphone transmitter is required to handle only small amounts of energy.

Other objects of my invention will be apparent from the following description when taken in connection with the accompanying drawings and claims.

In the art of wireless telephony, various modulating systems have been proposed for modulating the high-frequency energy in ac cordance with the voice vibrations to be transmitted; In one such system, varying amounts of high-frequency energy are diverted from the antenna systemv and dissipated in an absorbing circuit in accordance with the varying intensity of sound waves.

In another system, an energy absorbing device is inserted directly in the antenna circuit and its impedance is varied in accordance with the signals to be transmitted.

In the wireless telephone system embodying my invention, however, modulation of the radiated ener is efiected by varying the frequency an the amplitude of the high-frequency currents in an oscillatory circuit in accordance with sound waves, as hereinafter described. In a modification, the amplitude variations are still further mcreased by impressing the modulated radiofrequency currents upon a radiating circuit which is tuned to a frequency slightly different from that of the impressed curents.

My I invention, however, may best be understood by reference to the accompanyingrdrawings, wherein: Y ig. 1 is a diagrammatic view of a simple tuned circuit showing means for controlling the constants thereof in accordance with sound waves.

Fig. 2 is a diagrammatic view of circuits 4 and apparatus embodying my invention in a wireless'transmission system.

Fig. 3 is a similar view to that of Fig. 2, but showing an alternative system of modulation.

Fig. 4 is a view showing the diagrams referred to hereinafter.

In Fig. 1, I have shown a simple oscillatmg circult 1 consisting of an inductance coil 2 and a condenser 3, t

cause large variations in the resultant.

capacity effect of the condensers 3 and 5. Thus, by varying the resistance of the element 6, it is possible to vary both the amplitude and the frequency of such currents as are caused to traverse the tuned circuit 1.

While I have shown a capacitive reactor 5 as connected in series with the variable-impedance element 6, the results just mentioned may also be'obtained by replacing the capacitive reactor5 by an inductive reactor. In the following diagrams, the variable impedance element 6 has been shown as a thermionic tube, though I do not wish'to be limited to such device.

Referring to Fig. 2, I have shown a thermionic tube 7 adapted to serve as an oscillator tube in connection with a radiating tion 11 of an inductance coil 12 and a ground lead 13; Y

e latter being shunted vby al clrcult 4 which includes a relatively The thermionic tube 7, whichserves as an I oscillation generator, comprises an anode 14, a grid 15 and a cathode 16, the latter being energized by means of a source of energy 17 through a resistor-18. A plate-filament circuit comprises a conductor 19 connecting the anode 14 to the tuning coil 12, a sto ping condenser 20, which is included in sai conductor, a portion 21 of the tuning coil 12, the ground conductor 13 and a conductor 22 connecting the ground conductor and the filament 16. The condenser 20 serves to revent the tuning coil 12 from short-circuit- 1ng thedirect-current source which ener izes the tube,-as will be hereinafter described. A grid-filament circuit comprises a conductor 23, which serves to connect the grid 15 to one end of the coupling coil 12, a portion 24 of the'coupling coil 12, the ground conductor 13 and the conductor 22.

The oscillator tube 7 may be energized by means of a direct-current generator 25, the positive terminal of which is connected to the anode 14 by a conductor 26, and the negative terminal of which is connected to the filament 16, by a conductor 27. A It'ldlO: frequency choke coil 28 is serially included in the conductor 26. The thermionic tube 29 comprises an anode 30, a controlling grid 31 and a hot cathode 32, the latter being energized from a source of energy 33 through a resistor 34. The cathode 32 is directly connected to the negative terminal of the source of energy 25 and to the hot cathode 16 of the tube 7 by means of the conductor 27. The anode 30 is connected to the conductor 26 through a resistor 35, the

resistance thereof being determined by the plate-voltage ratingof the tube 29.

A microphone transmitter 36 is operative- 1y connected to a grid-filament circult of the modulator tube 29 through a coupling transformer 37, the primary winding 38 of which includes the microphone transmitter 36 and asource of energy 39, and the secondary winding 41 of whichis included in the grid-filament circuit just mentioned. A. conductor, which includes an inductance coil 42 and a stopping condenser 42a, extends from the anode 30 of the modulator 29'to an adjustable point 43 on the tuning coil 12 and serves to connect the plate 30 and the filament 32 of the tube 29 in shunt to. a portion 44 of the tuning coil 12.

In Fig. 3 is shown an oscillator generator system 45 operatively associated with an antenna circuit 46. The antenna circuit 46 includes an antenna 47, a coupling coil 48, which is associated with the oscillation generator system 45 and a ground lead 49. An absorbing circuit 51, which comprises a variable condenser 52,'acoupling coil 53 and an energy-absorbing element 54, is also operatively associated with the oscillationgenerator system 45.

Referring more specifically to the oscillation-generator system 45. I have shown an oscillator tube 55 comprising an anode 56, a grid 57 and a hot cathode 58 which may be energized by means of a source of energy 59 through a resistor 61. The source of energy 25 may be connected'to' the tube by conductors 62 and 63 which are connected to the anode 56 and to the hot-cathode 58, respectively, through choke 'coils 64 and 65. A modulator tube 66, which is similar to that shown in Fig. 2, may be energized from a separate source of energy 67 through a reactor 68.

The plate-filament circuit of the oscillation generator 55 comprises a stopping condenser 69, a portion 7 0 of a coupling coil 71 a conductor which extends from the anode tube.

renames and a return conductor 72. The grid-filament circuit includes a conductor 73, a portion 74 of the coil 71 and the return conductor 72. A circuit, which includes a fixed condenser 75 and a variable condenser 76, is shown as shunted across the plate-filament circuit of the tube 55. A condenser 77 of relatively small capacity, in comparison with that of the condenser 75, is included in of the tube 66 to an intermediate point in the circuit connecting the condensers and 76. The advantage of such capacity coupling of the modulator tube to the oscillation-generator system is that a much smaller modulator. tube may be employed by reason of the lower voltage and current requirements.

In operation, referring to Fig. 2 and assuming the thermionic tube 7 to be functioning as anoscillation generator, when voice vibrations enter the microphone 36, varying potentials are impressed upon the grid 31 of the modulator tube 29, thereby causing corresponding variations in the impedance of the plate-filament circuit of the Since the portion 44 of the coupling coil 12 is shunted. by the inductance coil 42 and the condenser 42a in series, with the plate-filament circuit just mentioned, the variations in the impedance produce corresponding changes in the amplitude and frequency of the radiated energy.

In the modification of my invention shown in Fig. 3, the radiating circuit 46 and the absorbing circuit 51 are tuned to different frequencies.v The generator circuit 45 is tuned to frequencies intermediate the frequencies of the radiating and absorbing circuits, whereby a change in the frequency of 105 the generator circuit is accompanied by substantially equal and opposite changes in the currents drawn by the radiating and absorbing circuits, respectively. The total current, representing the load on the generato'r circuit, is, therefore, substantially constant.

Referring to Fig. 4, the currents L and i induced in the radiating and absorbing circuits, respectively, for different frequencies of the currents in the generator circuit 45, are indicated. The maximum currents .drawn by the circuits 46 and 51 correspond to the frequencies F and F respectively.

The generator circuit 45 is normally tuned tor circuit 45, may be caused to correspond approximately with the slope of the curve I representing the current'in the radiat ing circuit over a given operating range. This has been indicated in Fig. 4 by means of a dotted-line curve R representing the relation between the frequency of the generator circuit and the resistance of the modulatortube 66. In this way, distortion of the, sound Waves may be largely prevented.

While I have shown only three embodiments of my invention in the appended drawings, I do not wish to be limited therebg, but I desire that only such limitations 5 all be imposed thereon as are indicated in the appended claims.

I claim as my lnventionz' 1. In a W1I l8S transmission system, an

.oscillation generator system including condensive and reactive elements, a constant supply of excltlng energy therefor, an antenna circuit and an absorbing circuit operatively associated therewith, and .a modulating circuit includin reactance elements, one of which is a variable-impedance element adapted to vary the amplitude and the frequency of the hi 'h-frequency energy generated by said osci lation-generator system in 3 accordance with sound waves, said antenna and absorbing circuits being so tuned that said modulations in frequency effect opposite variations in the power absorbed by each circuity 2. In a radio transmission system, the combination with a radiating circuit, of a. high-frequency supply circuit comprising inductive and capacitive lieactors, a variableimpedance device connected in parallel relaable-impedance device bein so adjusted that the variations in the impedhnce thereof produce var atlons 1n frequency cau'slng c0rrespondlng variations in the current in said radiating circuit, whereby sound distortion.

is largely prevented.

In testimony whereof, I have hereunto subscribed my name this 29th day of August,

ALEXANDER NYMAN.

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