US1673548A - Carrier-wave telephone system - Google Patents

Description

June 12, 1928. 1,673,548 C. A. BODDIE CARRIER WAVE TELEPHONE'SYSTEM Filed Aug. 18, 1923 wnusssss; INVENTOR C/armceflfioddle.

' TTORNEY Patented June 12, 1928.

UNITED STATES 1,673,548 PATENT ounce.

CLARENCE A. 120mm, 025 WILKINSIBTURG, PENNSYLVANIA, assmnoa T0 mam HOUSE nnso'raxc & MANUFACTURING COMPANY. ACOIRPORA'I'ION or PENNSYL- VANIA.

oanamaswavn TELEPHONE .sYsTEm.

Application filed August 18, 1923. Serial No. 658,041. l

My invention relates to carrier-wave tele phone systems and particularly to the transmission of signals by radio-frequency elecltl'lc current.

Broadly speaking, the object of my invention is to provide means for the duplex operation of radio signalling systems.

More specifically, the object of my invention is to provide a compensatingmeansfor transferring energy from a radio sending equipment to an adjacent radio receiving equipment in such way as to cause the trans ferred energy to neutralize energy transferred from the radio sending set to the adjacent radio receiving set byiwayof their respective aerials and the ether.

In the prior art of transmission of signals by radio communication methods, it hasbeen customary in a great many cases to shut down the. receiving apparatus during the time in which it was desired to send signals and likewise to shut down the sendingapparatus when it was desired to receive signals. It .was found that the relatively tremendous amount of energy in the sending system produced a decided influence on the adjacent receiving system. So much transferred to the receiving system when the sending system was in operation under ordinary conditions as to make it impossible to .necei ve signals from a distance. The energy thus received would render. receiving tubes inoperative in case vacuum tube detectors were employed, and in the case .otanyother .deteotor would entirely overpower signals from the remote station, Because ofthis tact, one-way operation only was ordinarily possible.

A number of attempts have been made "by inventors to find means of overcoming this difliculty, and thereby to permit duplex, or two-way, .operationso that it would-not be necessary to put the sending system .out oi operation when it was desired to receive signals. This object was especially .deslred in connection with radio telephone systems, in which duplex operation is very desirable. This object has been partially attained in the prior, art in number for ways. 'lhe receiving station and the sending station .may be geographically separated asubstaaitial d'stance and connected by a suitable transmission line, in which case duplex operation is to a certain extent possible, although .interterence is not entirely preenergy was vented. Some side tones remain regardless of the distance of separation of the stations. Attempts have been made to use the same aerial tor both receiving and sending. This has been done by means of a double sending helix. One "half of the helix is connected through the aerial and ground circuit and the other half is connected through an inductance andcapacitance equivaleutto the inductance and capacity of the-aerial system. I This inductance and capacity assembly forms what may be called a dununy aerial, which absorbs one-half oi" the input energy. In doing so it produces currents in the second half of the winding helix which are equal and opposite in phase to currents in the first half. Each ofthese currents then neutr liz'es the etiect ofthe other upon an inductively coupled coilin the receiving circuit. This arrangement permits the incoming sig nal current to be received-by the receiving system and does not; Permit the loi'rial'power current to interfere. This system is objectionable becauseof thetact that it wastes "one half of the total sending energy.

Another system, separates the receiving and sending-stations by a substantial geographical distance and connects them electrically by a singe transmission line, which line serves to carry audio frequency control current and also carries a small amount of" radio frequency energy from the sending apparatus to thereceiving apparatus for the purpose of neutralizing the enei'gy'picked up by the receiving aerial having radiated from the sending aerial. This system also gives approximate neutralization but it is objectionable because of the required goo graphical separation and because it does not give complete compensation. H

It has been proposed to employ two antenna syste1ns, one for receiving and one for sending, and a single-circuit inductive energy a transfer connection between sending and receiving apparatus. "lhissystem gives only the form of alternating currentl'las a specificphase relation to current in the sending aerial. To neutralize the et'fec.t of this energ in producing interference, a pre .cisely equal amount ot'energy at the same trequency and in precise phase opposition may be impressed upon the receiving system. If this is done, complete neutralization will be obtained. My invention efiects this result by means of a plurality of conductive channels from the sending apparatus to the receiving apparatus without requiring a geographic separation between sending and receiving stations.

Other objects and structural details of my invention will be apparent from the following description and claims when read in connection with the accompanying drawings, wherein I Figure l, is a diagrammatic sketch of apparatus and circuit connections embodying my invention and Fig. 2 is a vector diagram of the phase relations of the currents in the receiving apparatus.

in F i". 1, a sending system aerial 1 is located adjacent to the receiving system aerial Aerial l is connected to a tuning helix 3 by a lead-in wire 4;. A ground 5 is provided and connected by a lead wire 6 to helix 3 at a point above its bottom turn. This point is located in accordance with the desired wave, length or sending frequency. Energy is transferred to this coil from any convenient source as indicated by the prior art. This source may be a triode tube oscillator, with or without a modulator, according to whether or not it is desired to send voice modulated signals, or the source of energy may be an arc, spark, or other suitable source.

Receiving aerial 2 is connected to a suitable adjacent receiving set 7. The details of this set are not important. In the diagrammatic sketch, a simple system is shown com prising a series condenser 8, a tuning inductance 9, a triode detector 11. with its asso ciated grid leak and condenser 12, an A" battery 13, a B battery 14, telephones 15 or other signal receiver, lead-in wire 16, serving as connection between aerial 2 and receiving apparatus and lead wire 17 connecting receiving apparatus 7 to'the ground 18. A connection is made between receiving set Tat point 19, which is the point of connection between the series condenser and the tuning helix, and the sending system apparatus. This connection consists of two circuits, one circuit 21 containing a variable point of connection of duces oscillating current in the receiving apparatus which has the same frequency as the current flowing in the aerial sending system.

Referring to Fig. 2, this energy is indicatedby vector 25, this vector representing the electromotive force of the energy which produces interference in the receiving apparatus to prevent the reception of signals from a distant station. This clcctromotive force is neutralized by an equal electrometive force in precise phase opposition, which may be represented by vector 20. It is not however, possible to convey this amount of energy at this phase relation from the sending apparatus to the receiving apparatus by a single conductor, inasmuch as resistance loss and'inductive and capacitive effects do not permit of the ready development of an electromotive force at precisely 180 phase difference.

This electromotive force at the proper phase displacement can be readily obtained, however, by two successive increments of energy. The portion of sending helix 3 which lies below the ground lead connection (5 develops an electromotive force which is approximately at a phase displacement of 180. A suilicient electromotive force is, therefore, transferred from this lower portion of coil 3 by way of conductor 21 and condenser 22 to point 19 in the receiving set. This is represented by vcctorZB. This energy will give partial neutralization of the interfering energy. A further increment of energy represented by vector 27 may be conveyed from the sending set to the receiving set to give precise neutralization of interfering energy, by means of conductor 23' and variable resistance 24. Adjustment of resistor 24'and condenser 22 thus controls the phase relationand the magnitude of the conductively transferred electromotive force to the value which gives precise neutralization of the interference.

In practice, this system of a plurality of 'conductive connections between adjacent sending and receiving sets transfers energy from the sending to the receiving set which is inprecise phase opposition and equal in magnitude to energy transferred from the sending to the receiving apparatus by way of their respective aerials and the ether, thereby permitting duplex operation of the sending and the receiving apparatus.

WVhile I have shown only one embodiment of my invention in the accompanying drawing, it is capable of various changes and modifications without departing from the spirit thereof. I desire that it be not restricted to radio-frequency interference phenomena and that. therefore, only such limitations shall be placed thereon as indicated in the prior art or in the appended claims.

I claim as my invention.

1. In a -duplex system of radio signaling,

a station comprising a sending apparatus, a receiving apparatus, and a plurality of circuits linking said sending and receiving apparatus, said sending apparatus comprising an aerial, a tuning helix operatively connected thereto, a ground, a metallic connec: tion between said ground and said helix, said connection being made to said helix at a point other than the bottom turn thereof, and a source oi high frequency energy, said receiving apparatus comprising an aerial, a receiving inductance, a ground connection, detecting means, and signal indicating means, a circuit linking turns of said tuning helix below said ground connection to the junction between said receiving inductance and said aerial through a variable condenser, and an additional circuit linking turns of said tuning helix above said ground connection to the same junction between said receiving inductance and said aerial through a variable resistance.

2. In a duplex system of radio signaling, a station comprising a sending apparatus, a receiving apparatus, and a plurality of circuits linking said sending and receiving apparatus, said sending apparatus comprising an aerial, a tuning helix, a metallic ground connection for said helix, said connectionbe ing made to said helix at a point other than the bottom turn thereof, and a source of high frequency energy, said receiving apparatus comprising an aerial, a receivinginductance, a ground connection, detecting means, and signal indicating means, a circuit linking turns of said tuning helix below said groun-d connection to the junction between said receiving inductance and said aerial through a variable condenser, an additional circuit linking turns of said tuning helix above said ground connection to the same I junction between said receiving inductance and said aerial through a variable resistor,

and additional linking circuits comprising inductive, capacitive, resistive and conductive elements.

3. In a radio system, a sending set including an antenna, a coil and means for energizing said coil, a receiving set including an antenna and receiving instruments associated therewith and means for compeneating the efi'ect of the sending antenna on the receiving antenna comprising a closed circuit connecting twopoints of said coil at opposite potentials, said circuit including a resistor and a reactor in series at least one of which is adjustable, and a connection from a point in said circuit between said re-- sistor and reactor to a point in the receiving set.

In testimony whereof, I have hereunto subscribed my name this 13th day of August, 1923.

CLARENCE A. BODDIE.

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