US1341211A - Modulation of high-frequency currents - Google Patents

Description

R. A. HEISING.

MODULANON OF HIGH FREQUENCY CUHRENTS. APPLICATION FILED AUG.25,1915.

W/Tnesses: /n we n/o r: 67%. M Raymond A He/5mg.

Patented May 25, 1920.

UNITED STATES PATENT OFFICE.

RAYMOND A. HEISINGyOF EAST ORANGE, NEW JERSEY, ASSIGNOR, BY MESNE ASSIGN- KENTB, TO WESTERN ELECTRIC COMPANY, INCORPORATED, A. CORPORATION OF NEW YORK.

MODULATION OF HIGH-FREQUENCY CUBRENTS.

Patented May 25, 1920.

Application filed August 25, 1915. Serial No. 47,332.

To all whom it'may concern:

Be it known that I, RAYMOND A. Hmsixo, a citizen of the United States, residing at East Orange, in the county of and State of New Jersey, have invented certain newand useful Improvements in Modulawith the signals to be transmitted.

In view of the extreme sensitivity of a generator electro-motive force to variations in the current of the fieldwindings, it has been. su gested that the signaling device he put in t e field circuit, the current of which will be modulated in accordance with speech. However, althoughthe power used in the field windings is small compared to the output of the generator. it is still true that the wet required for the field is excessively arge for a telephone transmitter. Furthermore, the impedance of the field coil is large compared to that of the usual modu lator or: signaling device. such as the microphone trii'iismitter, -\vhereas-cithas been found desirable that they should be of about the same magnitude. or that the impedance 1 of the modulator should be greater than that of the field coil. This isnecessar-y in order to obtain etlicient or complete modulation. In other words. itis necessary that the modulator shall becapable of absorbing as much power as the field coils. Moreover, when a 'microphone is placed directly in the circuit of the field coil, the time constant is not ordinarily thereby reduced to a value which will 'prevent undue distortion of the, modulating currents because of the low-resistance of the microphone.

According to this invention the above noted defects are overcome or greatly reduced by placing the field or energizing winding in circuit with a space discharge device and pro erly proportioning the impedance of sait device with respect to that of the energizing winding. For maximum etliciency it has been found desirable to make the impedance of the space discharge device of the same orderot magnitude as that of the field winding. as explained above. However it may sometimes be desirable to provide a lower space discharge impedance in case the time constant is for any reason to be increased and 111 case maximum efliciency is not the primary consideration. If

desired, the impedance of the space discharge device may be increased toa value greater than that of the field coil for the purpose of reducing the time constant of the field circuit. A spacedischarge device suitable for this purpose is one, such as that described below. having a heated cathode and having the property of amplifying voltage variations impressed upon its input circuit.

Referring to the figure, an elevated antenna or other suitable radiating system, is in circuit with the high frequency generator 2 which is connected to the antenna on the one side and to the earth on the other. Sustained oscillations will thus be radiated from the elevated antenna. The field wind ing '3 of the generator 2 is connected in series to the output circuit of the thermionic space discharge device 4. This device ashere shown is substantially the same as that which is now employed as an amplifier of, telephonic currents- It comprises an evacuatedvessel in which there is a heated cathode "5. an impedance varying element 6. in

the form of a grid. and a plate anode 7. Any known form of discharge device having an element by means of which the impedance of the discharge path may be varied, may be employed, The grid circuit of the discharge device includes the secondary of the transformer 9, the primary of which contains the battery 10 and microphone transmitter 11. or its equivalent.

The impedance of that part of the discharge device which is in circuit with the energizing winding of the generator is made of the proper value to give the desired re sults in accordance with the principles set" therefore modulated in accordance with the signals impressed on the microphone. This modulated field current will impress corresponding modulations. upon the high frequency power radiated from the antenna.

Although the primary object of this invention is to provide a method and means for modulating the high frequency power used in wireless telegraphy or telephony in accordance with the signals to be transmitted, certain features of the invention. as defined in the appended claims. are capable of quite general application. as will be evidentto those skilled in the art. The invert 'Ifli-lOIL. may. lie employedcin sygiteng ma king use of a transmission hne in place of antennae. It is obvious also that the receiving relay current may be used for any desired purpose, such as the distant control of switching or other mechanism. The microphone 11 may be replaced by other controlling means such ascircuit controlling means used in telegraph systems.

By characterizing the frequency of the oscillations produced by the generator as high, it is meant that this frequency is high as compared with essential voice or signaling frequencies. It is obvious that the invention is applicable toany form of generator in which there is an energizing wind ing having a source of current for supplying initial energy for the generation of the oscillations.

at is claimed is: 1. The method of controlling the amplitude and distortion of the output waves of an alternating current generator having a 'wind-ingsupplied with current partat-Jeast of the energy of which current is employed in the production of said output waves. which method comprises generating control currents, causing a part of the energy of said supplied current to be absorbed without inductive action. and simultaneously variably controlling the energy thus absorbed in accordance with said control currents. A

2. The method of controlling fluctuating currents produced by a generator having a winding supplied with current. part at least of the energy from which is employed in the production of said fluctuating currents, which method comprises causing a part of the energy of said supply current to be absorbed in a space discharge. and simultaneously variably controlling the energy thus absorbed.

3. The method of controlling fluctuating electrostatically variably controlling during such absorption the portion of energy thus absorbed.

:l. The method of controlling high frequency oscillations produced by a generator having a winding supplied with current, part at least of the energy of which current is.cmployed in the production of said high frequency oscillations, which method comprises causing a part of the energy of said current to be absorbed without inductive action, and simultaneously electrically controlling in accordance with speech currents the energy thus absorbed. j. The method of controlling currents proddee d by a generator having a winding supplied with current, part at least of the energy of which current is employed in the production of the generated currents, which method comprises causing part of the energy of said supply current to be absorbed in a space discharge and simultaneously controlling the energy thus absorbed.

(3. The method of controlling current produced by a generator having a winding supplied with current, part at least of the energy of which current is employed in the production of the generated currents, which method comprises causing a part of the energy of said supply current to be absorbed in a space discharge and simultaneously controlling the energy thus absorbed by varying the impedance of the space .discharge path.

7. The method of controlling currents produced by a generator having a winding supplied with current. part at least of the 'rnergywt' .whichcurrentds employedin the production of the generated currents, which method comprises causing a part of the energy of said supply current to be absorbed in a space discharge and simultaneously controlling the energy thus absorbed by varying the electric field in the vicinity of the space discharge.

8. In a high frequency signaling system. a generator of high frequency oscillations having a field winding, a source of low power oscillations. a large variable impedance of at least the same order of magnitude as that of said field winding controlled by said source, and means whereby the variations in said impedance control the current in the field winding of said generator.

9. In a high frequency signaling system, a generator of high frequency oscillations having a field winding, a telephone transmitter for producing low power signaling oscillations, a variable impedance of approximately the same value as the impedance of said field winding. said variable impedance being adapted to be varied by said low power oscillations. and means for connecting said variable impedance to said field winding, thereby controlling the current in said field winding in accordance with said variable impedance. I

10. In a high frequency signaling'system;

a generator of high frequency oscillations havin a field windin a sourceiof'low fre 5 n I a I quency oscillations, a variable impedance having a value at least of the same order of magnitude as the impedanceofsaid-field' winding. said variable impedance being adapted to be varied by saii'l low frequency' source, and means forassociating said variable nnpeda-nce witli'f-said field wind ng,

thereby controlling thecurrent in said field winding in accordance I with r said" variable impedance.

11. In a high frequency signaling system, a generator of high frequency oscillations having a field-winding, a source oflow frequency oscillations, a variable impedance having aval-ue of approximately the same order of magnitude as the impedance of a generator of high frequency oscillations ha'v1ng a field winding, a thermionic amplifier connected to said field Winding, and

v a'signaling device associated with said amplifier to modulate the impedance of said field winding in accordance with signals to be transmitted, said field winding having an impedance greater than that of said signaling device.

In witness whereof, I hereunto subscribe my name this 19th day of August, A. D. 1915.

RAYMOND A. HEISING.

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