US1696212A - Selective-translation system - Google Patents

Description

Patented Dec. 25, 1928.

' UNITED STATES PAT ENT OFFICE.

JOHN PETER SGHAFER, OF RICHMOND HILL, NEW YORK, ASSIGNOR TO WESTERN I ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y; A CORPORATION OF NEW YORK.

SELECTIVE-TRANSLATION sYsT iiu.

Application filed December 22, 1923. Serial No. 682,180,

This invention relates to selective translation systems.

One object of the invention is to selectively control the transmission of waves through a circuit.

Another object of this invention is to receive electric wave energy and to selectively transmit this energy to a receiving device.

Another object of the invention is to eliminate interference between energy of different frequencies impressed upon "a receiving circuit.

Afurther obj ectof the invention is to selec tively receive energy of a plurality of frequencies representing different signals.

An additional object of the invention is to provide a duplex radiant energy signaling system employing a single antenna for reception and transmission of signal waves.

A feature of the invention concerns a vacuum tube amplifier provided with a resonant circuit connected between its input and output circuits foreliminating current of a given frequency from said output circuit.

Another feature of the invention relates to means in the output circuit of a space discharge amplifier to prevent the flow of current of a given frequency through said circuit.

A further feature relates to a duplex radio transmission system having means to substantially prevent any energy of the transmitted frequency from reaching the local 'ev ceiving device.

A still further feature relates to resonant circuits connected with the input and output circuits of a space discharge amplifier to exclude current of a particular frequency and y i a particularharmonic of this frequency from the output circuit;

A form of this invention which has been chosen for the purpose of illustration com prises a radio transmitting and receiving system. A transmitting and receiving circuit are coupled to an antenna, the receiving 011* cuit being arranged to receive messages without interference from the transmitted waves. The receivingcircuitcomprises aspace discharge amplifier provided with a tuned cirjcuitcoupledbetween its input and output circuits and another tuned circuit connected in shunt to its output circuit. These tuned circuits function "to exclude energy of the een y ran mitted fr m ewes rcuit of the amplifier and also certain harmonies thereof. Thus signal waves are transmitted to a rece ving device coupled to the amplifier output circuitgvithout disturbance from extraneous waves.

Anequation based upon the constants of the thermionic tube and the connected circuits is employed to determine the values of the constants of the resonant circuit to be connected between the input and output circuits;

The drawing represents the terminal circuit of a duplex radio transmission system or the terminal of atwochannel receiving circuit including thefeatures of this invention.

Referring to the drawing, an aerial 10 is connected to ground'through a seriescircuit comprising variable condenser 11 and Winding 12 of a high frequency transformer 13. Block 15 represents any desiredform of radio transmitting system or it may represent a receiving circuit which is a duplicate of that about to be described in detail. Primary winding 14 of transformer 15 is connected to the transmitting system 15 for coupling it to the antenna 10.

The receiving system comprises an amplifier 20 comprising three electrode space dis charge tubes 21 having an input circuit 22 and a load circuit 23. The circuit 22 is connected to the grid and filament oftube 21 and includes a grid polarizing battery 24 in series with resonant circuit 26,127,which is preferably tuned to the frequency of waves that it is desired to receive. The inductance 26 constitutes a winding of the transformer 13 whereby the amplifier20 is coupled tothe antenna 10. By means of the variable concuit is made possible.

denser 27 the tuning of the resonant cir- Load circuit 23 is connected to the plate form of detector or den'iodulator having a signal receiver connected thereto. The receiver 35 may be immediate to the amplifier 20 or at the end of atransmission line.

A resonant circuit l0 which is connected between the input and output circuits of the amplifier 20 comprises an inductance 37, a condenser 38 and an adjustable resistance 39.

Inductance 41 in series with variable condenser 42 constitutes a series resonant circuit connected in shunt to the load circuit 23.

In an article by H. N. Nichols in the Physical Review, Lancaster, Pil N. S. Vol. XIII, 6, June 19, 1919, page 4:04, it is shown that a vacuum tube such as tube 21 connected in a circuit such as shown in the drawing may be considered as a virtual source of alternating electromotive force. However, in the drawing, amplifier 20 may be considered to have two alternating current generators, connected in series through associated alternating current resistances. For example, resonant circuit 26, 27 supplies an electromotive force acting through the impedance of resonant circuit 40; tube 21 supplies a virtual alternating electromotive force which acts through the internal alternating current resistance of tube 21. In addition the electromotive force of tube 21 is 180 out of phase with the electromotive force produced by resonant circuit 26, 27. It has, furthermore, been shown that an alternating current of a given frequency,produced by on electromotive force in the resonant circuit 26, 27 may be excluded from the load circut 23. By referring to the drawing it is seen that the circuit 23 is connected between the junction points connecting one of these alternating current generators with its associated impedance to the other alternating current generator and its associated impedance. Energy of this frequency is excluded from the load circuit 23 by tuning resonantcircuit 10 to resonance at the frequency which it is desired to exclude and by further adjusting the resistance 39 to a valuehaving that relation to the value of the alternating current resistance of tube 21, which is explained more fully later. When the resistance 39 is adjusted to the proper value and when resonant circuit -10 is tuned to the frequency tobe excluded, variations in the electromotire force of this frequency supplied by resonant circuit 26, 27 will not produce any variation of this frequency in the current in circuit 23.

Any reactance which may exist between the plate and grid of tube 21 maybe compensated for in the tuning of resonant circuit 40 so that the arallel paths comprising this reactance and the impedance of resonant circuit 40 will form a resonant circuit for the frequency to be excluded from the output circuit.

As shown in the article referred to above, it has been found thatthe following equation applies to the circuit shown in Fig. 1 where t represents the amplification constant of the tube 21, I the current flowing in the output circuit 28 in response to the alternating potential e, and R the alternating current resistance between the cathode and anode of the In the above equation Z, represents the impedance of resonant circuit 40, Z represents the impedance of load circuit 23. By adjust ing the resistance 39 of the impedance Z,,, at a frequency corresponding to zero rcactance of the impedance Z, in accordance with the equation: R

where 1' represents the resistance 39, it will be seen that the numerator of the second member of the equation (I) becomes zero, or in other words the current I in the output circuit of the amplifier will be zero for the freuency at which Z is equal to 1'. If 1' is adusted to values other than in accordance with equation (2), above, the magnitude of the output current of the frequency at which Z, is of zero reactance may be varied to any desired value. y

In the operation of this system, wave energy of a frequency represented by f, is transmitted from the system indi-ntcd by block 15 to the antenna 10 from which it is radiated. In the alternative arrangement in which the circuit 15 is a receiving circuit energy of this same frequency may be received by the antenna 10 and transmitted to the system 15. The receiving device 35 is arranged to receive energy of frequency rcprcsented by f.,. Energy of the frequency f, is necessarily impressed on the input cir' cuit of tube 21 but by adjusting resonant circuit 40 in accordance with the method al ready described, the energy of the frequency 7, may be excluded from the load circuit 23 and consequently from the receiving device 35. It is found, however, that under certain conditions, energy having a frequency which is a harmonic of the frequency f, may be transmitted to the output circuit through the amplifier and to exclude energy of this harmonic frequency from load circuit 23, a resonant circuit 41, 42 is providedin shunt thereto. By means of variable condenser 42, this resonant circuit is adjusted to resonance at the harmonic frequencywhich it is desired to exclude. This circuit then comprises a path of low impedance to the harmonic frequency whereby the latter is prevented from flowing through the load circuit 23. It will in general be desirable to tune resonant circuit t1, (2 to the frequency of the second harmonic. The resonance circuit 41, e2 offers high impedance to waves of the frequency which it is desired to receive and consequently llU lit

they are transmitted through the load circuit to receiving device 35.

Although this invention has been described in connection with a specific embodiment, it is not intended that its scope should be limited thereto.

What is claimed is:

1. In an electric: circuit, a relay device having input and output circuits, an impedance element connected between said circuits to prevent the flow of waves of given frequency through said output circuit, and ah impedance element connected to said output circuit to prevent the flow of waves harmonic to said given frequency in said output circuit.

2. In a radiant energy transmission system, means for generating waves of frequency f means for impressing waves of said frequency upon an antenna, means for receiving energy of frequency f, coupled to said antenna, said last named means comprising a space discharge amplifier having input and output circuits, means coupled to said circuits to exclude energy of frequency f, from said output circuit, and aseries resonant circuit in shunt to said output circuit, said resonant circuit being tuned to the frequency 2 3. In combination, a space discharge amplitier having input and output circuits, a resonant circuit connected between said input and output circuits, and a resonant circuit in said output circuit to supply low impedance paths to energy of a given frequency and the second harmonic thereof respectively whereby energy of these frequency is ex cluded from said output circuit.

4. In combination, an amplifier having an input circuit and an output circuit, means connected between said circuits to selectively prevent the transmission through said output circuit of waves of a given frequency, and means in shunt to said output circuit of substantially Zero impedance to waves of twice said given frequency but of high impedance to waves of other frequencies.

5. In a radiant energy transmission system,

a receiving system and a transmitting system coupled to a common antenna, a space discharge amplifier in one of said system having input and output circuits, adjustable means connected between said circuits to exclude energy of the frequency produced by said transmitting system from said output circuit, and means of substantially zero impedance to waves having a frequency harmonic to that of Waves from said transmitting system but of high impedance to waves of other frequencies connected across'said output circuit.

6. In a duplex transmission system, an antenna, a transmitting system and a selective receiving system coupled to said antenna, said receiving system comprising an amplifier having input and output circuits, and a resonant circuit connected in shunt to said output circuit and a second resonant circuit connectedvbetweenr said input and output circuits, said resonant circuits being tuned to the frequency assigned to said transmitting system and a given harmonic thereof, whereby said frequencies are prevented from flowing in an output circuit of said amplifier.

7. In a signaling system, a receiving conductor, a pluralit of circuits coupled to said conductor, said circuits having predetermined assignmentof carrier frequencies,

and a plurality of resonant circuits associated with one of said circuits to preventiit terference from waves of the carrier frequency assigned to another circuit and a given harmonic thereof. i 8. In an electric circuit a relay device having input and output paths, a, tuned circuit 7 connected between said paths to prevent the transmission of waves of a given frequency to said output path, and a second tuned circuit connected in said output path to prevent the flow of another given frequency therein, one of said given frequencies being a harmonic of the other.

In witness whereof,vI hereunto subscribe my name this 19 day of December, A. D. 1923.

J. PETER SCHAFER.

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