US1258548A - Radiotelephony. - Google Patents

Description

C. R. ENGLUND. RADIUTELEPHONY. APPLICATION FILED m. n. 1916.

1,258,548. Patented Mar. 5,1918.

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GMT; JR. ENGL'UNID, OF EAST ORANGE, NEW JERSEY, ASSTGNOB T WESTERN ELECTRIC comm, rnconrona'rnn, or new YonK, IT. 1., A conrona qrlmronx. nanro'rnnnrnonr.

Speeificationcf Letters Patent.

Patented Mar. a, 1918.

Application filed March 11, 1916. Serial No. 83,504.

To all whom may concern:

Be it known that I, CARL R. ENGLUND, a citizen of the United States, residing at East Orange, in the county State of New Jersey, have inventedcertain new and useful Improvements in Radiotelephony, of which the following is a full, clear, concise, and exact description.

This invention relates to radio telephony, and in particular to a system of transmission in which only the modulated portion of a high frequency wave is radiated from the antenna.

in radio telephony it has been customary to establish in a circuit a high frequency oscillation and to modulate the amplitude of this oscillation in accordance with a signal to be transmitted. Now, it is well-known that when a high frequency carrier wave of frequency C is modulated in accordance with a s1gnal wave of frequency S, the re sultant wave radiated from the antenna is made up of three parts of frequencies CS, U and (3-1-55, which components may be considered to be transmitted simultaneously through the ether. It has been proposed as described in British specification No. 17,170 of 1916 of which the serial number under the new British system of consecutive numbering, is 102,503, to eliminate from the antenna the unmodulated component of frequency t), and to transmit only the modulated portions represented by the other two components. When this method is adopted is spoken of as a pure modulated wave. The great advantage of this method is that the waste of power represented by currents of frequency 0 in the antenna is eliminated, and that there is some gain in the quality of received oscillation. in order to receive signals sent in this manner it is necessary to include at the receiving station, in addition to the usual apparatus, a small enerator capable of delivering currents o the elminated frequency C, but since only a very small amount of power of this frequency is required at the receiving station, the auxiliary generator at that station need have but an extremely small power output.

in the s ecification above referred to a 'certain metihod of eliminating the unmo ulated component of the carrier wave is given, and this invention proposes still anat other-- way of accomplish ng this purpose,

of Essex and 'oscillatlon of carrier namely, by superposing upon the modulated wave before it reaches the antenna an oscillation of carrier frequency which is equal in amplitude but opposite in phase to the frequency which represents the unmodulated portion of the wave to be transmitted. By this means the component to be eliminated from the antenna is neutralized in the apparatus between the primary modulating source and the antenna. The invention will be more particularly described in connection with the drawing, in which Figure 1 represents a transmitting station constructed in accordance with this invention and Fig. 2 shows a form of receiving station by which the modulated waves may be received. This receiving station forms no part of this invention.

Referring to Fig. 1, 1 is a generator of oscillations of the frequency C and 2 a trans former by means of which these oscillations are impressed upon the input circuit of a thermionic modulator 8. 4. is a microphone circuit, the variations of current in which are impressed upon the same input circuit through the transformer 5. The result of this arrangement is, as is now well-known, to produce in the output circuit of the modulator 3 a high frequency current whose amplitude is modulated in accordance with the alternating currents set up in the microphone circuit. This output circuit is connected through transformer 6 to the common input circuit of a number of thermionic amplifiers 7 arranged in parallel, their common output circuit being coupled through transformer 8 to the radiating antenna 9.

The system so far described is characterized by the fact that currents of all three of the above mentioned frequencies occur in the antenna 9. By means of the apparatus next to be described the component of frequency 0 is prevented from reaching the antenna by being neutralized in the input circuit of the amplifier 7. To accomplish this, the input circuit of the amplifier 10 is connected through an autotransformer 11 to the terminals of the generator 1, the purpose of this autotransformer connection be-' g" emat te ampli ers 7. It will be clear that this latter voltage will have the frequency C of oscillations "produced by the generator" 1 and that. these'inay be so regulated as to intensity antenna 9. In case the amplifier 10 or the. phase regulating device 12 are not so ad-.

just'ed that the neutralizing current is exactly opposite in phase or equal in intensity to the component of frequency 0 of, the modulated current, a small portion of the said component of frequency C may not be neutralized. In such a case, the system would be operative, but less efficient, as some energy' would he radiated in the form of waves of frequency 0. The expressions equal in intensity and opposite in phase should,

j therefore, be taken to mean substantially equal in intensity and substantially opposite in phase.

Referring to Fig. 2, 14 is a receiving antemia coup ed to a resonant circu t 15 tuned to,.the frequency 0 of the waves to be recived. 16 is athermionic detector Whose output circuit is connected through a transformer to thetranslating device 17. It will be clear that the Waves received by this syster'rriwill lack the component of frequency G, and the function of the auxiliary generator 18 is to supply small oscillations of this frequency. The circuit of this generator may becoupled in'iany suitable manner to the antenna 14; or to the resonant circuit 15.

2 Although this invention has. been described as applying toradio .telephony, it will be clear to those skilled in the art'thata wire telephone line may be substituted for the antenna -9 without departing from the spirit of" this invention. It will further then afipplied to the common input circuit of be obvious'that many other circuit arrange ments may be devised by means of which the oscillation of frequency ,0 may .be neutralized in the input circuit of the amplifier 7. What is claimed is:

1. The method of preventing the radia tion of the unmodulated component of. a signaling wave which consists in superposing upon said wave an unmodulated Wave of equal value,- but of phase opposite to that of the said unmodulated component.

2. The method of preventing the radiation of the unmodulated component of a signaling wave which consists in opposing said compunent by an equal wave.

3. A radio transmitting system comprising in' combination means for generating and modulating high frequency oscillations means for impressing upon said modulated oscillations an unmodulated oscillation of opposite phase, and means for amplifying and transmitti g the resultant of said oscillations.

4. A radio transmitting system comprising in combination means for generating and modulating high frequency oscillations, means for neutralizing the, unmodulated component of said modulated wave, and means for amplifying and transmitting the modulated portion of said wave.

5 In a radio transmitting system, the combination of means for generating high frequency oscillations in two circuits, means for modulating the oscillationsof one of said circuits, means for changing the phase of said unmodulated oscillations in the other circuit so that it is substantially opposite of said-modulated oscillations, and means for impressing said modulated and unmodulated oscillations of changed phase upon a third circuit.

' In witness whereof, I hereunto subscribe my name this 9th day of March A. D.,.1916.

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