US2019341A

US2019341A - Transmission system

Info

Publication number: US2019341A
Application number: US708619A
Authority: US
Inventors: Robert B Dome
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1934-01-27
Filing date: 1934-01-27
Publication date: 1935-10-29
Anticipated expiration: 1952-10-29

Description

Oct. 29, 1935. R B, DOME 2,019,341

TRANSMISSION SYSTEM Filed Jan. 27, 1954 Fig.1.

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b His Attorne g.

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Patented Get. 29, 1935 UNITED STATES PATENT orrios TRAN SllIISSION SYSTEM New York Application January 2'1, 1934, Serial No. 708,619

Claims.

My invention relates to transmission systems and more particularly to high frequency transmitting systems in which it is desired to couple a plurality of sources of oscillations to a common 5 load circuit.

It frequently happens, for example, in connection with radio transmitting systems, that it is desired to radiate the energy of a plurality of transmitters from a common antenna. These transmitters may operate at difierent frequencies and the carrier waves produced thereby may be modulated with difierent signals. If their output circuits be connected together as to a common antenna, unless special means be provided,

the energy from one transmitter will be supplied to the output of a difierent transmitter and become modulated with the signal with which the carrier wave of the other transmitter is modulated. In this way each carrier wave radiated may become modulated, not only with its own signal, but with one or more signals with which the carrier waves produced in the other transmitters are modulated, with the result that all of the various signals are received in any receiver notwithstanding that the receiver be extremely selective to any desired one of the transmitted carrier waves.

One of the objects of my invention is to provide means whereby interference produced by such intermodulation of the various waves radiated from the common antenna may be avoided.

A further object of my invention is to provide means whereby a plurality of transmitters may be connected to a common output circuit and whereby the transmission of energy from any transmitter to another is avoided.

Still a further object of my invention is to provide means whereby the above results are obtained without the use of filters.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation together with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawing in which Figs. 1 and 2 represent embodiments of my invention and Fig. 3 is a graphical representation of oscillations from transmitters l and 2.

In Fig. 1 I have represented by the rectangles I and 2 a plurality of high frequency transmitters which are connected respectively through conductors 4 and- 5 to a transmission line 6 leading to antenna 1 which is represented as of the balanced type. Transmitters l and 2 may comprise electron discharge devices and may operate at different frequencies. Commonly they include electron discharge amplifiers in their output cir- 5 cuits by means of which the modulated carrier waves to be radiated are amplified. The anode circuits of these amplifiers of course act as rectifiers of any oscillations supplied thereto from the external output circuit. Thus, if oscillations of 10 the frequency produced by the transmitter 2 be supplied through the conductors 5 and 4 to the output of transmitter l, they will be rectified in the output circuits of the electron discharge devices of the transmitter l. At the same time they 15 become modulated. with the signal with which the carrier wave transmitted by the transmitter l is modulated, with the result that any receiver responding to the carrier wave transmitted by the transmitter 2 will not only receive the signal 20 with which the transmitter 2 is modulated but will also receive the signal with which the carrier wave transmitted by transmitter l is modulated. This is avoided in accordance with my invention by connecting the lines 4, 5 and 6 together at a 25 point at which the voltage of each of the different wave lengths has a value which is a relatively small portion of the maximum instantaneous value of the respective wave-length.

This conection can best be understood by reference to Fig. 3 where I have plotted curves 8 and 9 to represent oscillations from the transmitters l and 2. These curves are at maximum in-phase values at the extreme left end of the figure. This extreme left end may correspond to the ends of antenna 1 at which the voltages of the two Wave lengths are maximum. These curves also represent maximum in-phase values at the extreme right end of the figure whereas at a point II], for example, intermediate the two ends the curves represent maximum opposed voltages. At points H and I2 approximating nodal points adjacent to this point I!) both curves represent voltages of extremely small value. Either of these points may correspond to the point of interconnection of the lines 4 and 5. That is, the transmission line 6 is so adjusted in length that the point of interconnection of the lines 4, 5 and 6 corresponds on the voltage waves to the points II or I2 of Fig. 3. In this way the voltage which is supplied from either transmitter l or 2 to the opposite transmitter is a minimum. At these points H and I2 it will be observed that the two voltages are in-phase. The desired connection, however, may be eftwo voltages are of opposed phase but nevertheless are of extremely small value. The various lines may also be connected at points corresponding to points I5, l6, etc. with varying degrees of effectiveness.

In Fig. 2 I have shown my invention employed in connection with an antenna I! of the grounded type, the line 6 beingconnected to the antenna through a suitable line terminating unit l8. This unit may of course include elements whereby the effective length of the line 6 may be so adjusted as to cause the point of interconnection of the lines 4 and 5 to fall upon one of the points referred to of the voltage waves.

While the degree of effectiveness with which my invention may be employed is dependent upon the relation between frequencies to be radiated, nevertheless irrespective of this relationship marked advantages may be obtained. If the difierent frequencies are of the relation of fundamental and odd harmonic a common point can be found at which each of the different Waves has a nodal point of voltage. This is an ideal point of interconnection of the different lines since when so connected no voltage is supplied from either transmitter to the other. The poorest case is that in which the two frequencies are in the relation of fundamental and even harmonic, but even in this case a point may be found 'upon the voltage waves where the two lines may be interconnected with a minimum of voltage transmitted between sources.

The impedance of the line 6 looking from the point of interconnection of the different lines preferably is adjusted to a value relatively small compared with the output impedance of the sources I and 2 looking from the same point, so that practically all of the energy transmitted from any of the sources flows toward the load end of the transmission line 6 rather than toward the opposite transmitter.

While I have shown particular embodiments of my invention it will of course be understood that this is by way of illustrating the principles involved, and that I intend by the appended claims to cover any modifications of the arrangements shown which may be made without departing from the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:-

1. In combination, a plurality of sources of 2,019,341 fected at a point l3, for example, where the oscillations operating at diiferent respective frequencies, a load circuit common to all of said sources, said load circuit having a point approximating a nodal point of the voltage impressed by all of said sources, and connections from each 5 of said sources to said common load circuit, the connection from each of said sources being made to the load circuit at said point approximating a nodal point of voltage impressed on the load circuit by all of said sources. 10

2. In combination, a plurality of sources of oscillations operating at difierent respective frequencies, a common load circuit therefor, and means to prevent oscillations supplied to said load circuit by one of said sources from being impressed on another of said sources, said means comprising connections including said sources in branches between the same two points on said load circuit between which two points the voltage from said one source has a relatively small portion of its maximum instantaneous value.

3. In combination, a plurality of high frequency transmitters operating at different wave lengths, a load circuit, and connections for supplying oscillations from each of said transmitters to said load circuit, each of the respective connections to the load circuit being made at the same point of said load circuit, said point having substantially zero voltage of the frequency produced by both of said transmitters.

4. In combination, an antenna, a transmission line connected thereto, and a plurality of sources of oscillations operating at different wave lengths connected to said transmission line at a common point, said transmission line having such an eifective electrical length that the voltage of each of said wave lengths at said common point has a value which is a relatively small portion of its maximum instantaneous value.

5. In combination, an antenna, a transmission 49 line connected thereto and a plurality of sources of oscillations operating at different wave lengths connected to said transmission line at a common point, said transmission line having such an effective electrical length that the voltage of each of said wave lengths at said common point has a value which is a relatively small portion of its maximum instantaneous value, and the relation between the impedance of said sources and said transmission line locking from said point being 50 such that practically all of the energy from each of said sources flows toward said antenna.

ROBERT B. DOME.