US1934924A - Radio communication system - Google Patents

Description

Nov. 14, was. iR -r 1,934,924

RADIO COMMUNICATION SYSTEM Filed March 26, 19:50 2 Sheets-Sheet 1 INVENTOR.

RALPH M. H IIYTZ m {IQ -fli ATTORNEY Nov. 14, 1933. R. M. HEINTZ RADIO COMMUNICATION SYSTEM Filed March 26, 1930 2 sheets-sheet 2 INVENTOR. 2A1 PH m #:wvrz

M Q/ @o( TTORNEY HlSA Patented Nov. 14, 1933 1,934,924 mmro COMMUNICATION SYSTEM Ralph M. Heintz, Palo Alto, Calif.', assignor to Heintz & Kaufman, Ltd., San Francisco, Calif.,

a corporation of Nevada Application March 26, 1930. Serial No. 439,054

16 Claims. (01.250-2) My invention relates to systems of radio communication, and particularly to a system for transmitting a plurality of messages on a single wave-length and without interference.

An object of my invention is to provide a meth-' od of transmitting a plurality ofradio messages on a single wave-length, and of discriminating between these messages at the receiving point or vide a means of discriminating between odd and even reflections of the free waves emitted by a transmitter should more than one reflection reach for purposes of. clarification only and are not.

the receiver.

The invention possesses numerous other objects and features of advantage, some of which with the foregoing, will beset forth in the following description of my invention. It "is to be understood that I do not' limit myself tolthis disclosure of species of my invention, as I may adopt variant embodiments thereof within the scope of the claims.

'In general terms, my invention-comprises the and translated to sound through an ordinary head set or equivalent translating device, or the translating device itself may be made polyphase.

Referring to the drawings: I

:Figure 1 illustrates one form of the polyphase antenna system, the showing being a semi-diagrammatic perspective'view. Figure 2 is a diagram showing the reversal of direction of polarization by the reflection of the polarized wave from the Kennelly-Heaviside layer. Y

. Figure 3 is a plan view'of the antenna systemof Figure l,showing the coupling of ,the antenna to a three phase oscillating circuit.

Figure 4 is a circuit diagram of a three phase oscillating system. I I

Figure 5 is a diagram showinga receiving cir-I cuit. In this figure is shown the 'method. of mixing the incoming signalswith the polarizin oscillation at the receiver. 1 v

, Figure 6 is a schematic receiver diagram, showing the method of separating the messages car ried by two oppositely rotary polarized waves received by a single antenna system... 1

In the foregoing and succeeding disclosure 1 have used theterms reflections and, reflectedwaves Whether the waves are. reflected by layer is a controversial point. It is to be under-1' stood that while-the diagrams show and refer-; j ence is made to reflections, such references are.

tobe taken as favoring either concept of the natural phenomenon.

In order to generate the rotary-polarized Wave,

a polyphase oscillator is used. This oscillator the oscillators are three delta-connected... oscillatingcircuits, each consisting'of a pair of separately shielded coils 7 and 8, connected series and bridged by a condenser 9. :Plate current from a suitable source .11, iswsupplied through a radio frequency 'choke coil*12,which. is cofinected between the coils 7 and 8, of eachofthe oscillating circuits. It is to be .notedthat a single coil 12, connected to any of the oscillating circuits, would be sufficient to supply all three tubes; the three coilsare used for the sake of connecting with the'common filament circuit 16.

Power is'drawn from the circuit from the coils l7 which are coupledwith the coils'7. In'order' 79.; or are refracted through the Kennelly-I-Ieaviside oscillator system shown in Figure 1.

17 are the only portions of the transmission The oscillator may be modulated in the same manner as any single-phase oscillator, e. g., by a key in series with the plate supply 11, or by Varyingthe voltage or current supplied to the tubes from the-platesupply at voice frequency, it being noted that since all of the phases are modulated together no particular form of modulating circuit is required. c

The polyphase oscillation'is radiated through an antenna system whichmay be of the type shown in ,Figure 1. Three antennas 21 are sym metrically supported fromthemasts 22. Each of these antennas is one-half wave length long, and is fed at its mid point by a high frequency transmission line 23, which is an integral number of quarter-wave-lengths long. Insulators 24, are provided at the ends of the" individual antennas in the usual. manner.

An antenna of the. type described, fed

vector being horizontal. The phase of this wave. varies'in azimuth, depending upon the direction from which it isviewed; As seen from above the generated wave is rotary-polarized,its-direction i of rotary-polarization depending upon the phase countofat the receivingstation.

a This offers a method of discriminating between the firstior usefulrefiection of the Wave and the mission; t'em could be used with a three-phase transmit- 1 ting system, .or a star connected three-phase:re-

ceiving system may be used in connect-ionwith the delta-connected transmitting system; This follows from the fact that any'polyphase bal-' sequence of the oscillator generating it. It will 40'" be appreciated that the ground wave emitted by such an antenna is no different from that transmittedfrom any horizontal antennainsofar as its effect/upon a receiving apparatus is concerned. The free wave, however, is rotary-polarized, and since-it is from the free wave that practically all short wave :long distance trans-: mission eflects are obtained,z-it is with this wave that we are most concerned. Assuming such a wave to be dextro-rotary as itleavesthe transmitting. antenna, it will. bev transmitted with this .direc'tioniof rotation until:

it' strikes the reflecting Kennelly l-leaviside layer,

The reflected wave is polarized in the Lopposite direction, i. e., it is levulo-rotary. "A secondirefiection will, of course, again reverseits direction ofpolarization, and this fact'must be taken'acsecond and "fourth reflections which -causepernicious 'echoefiectsf The preferred type of receiving antenna is also polyphase, such asshown in Fig. '3, but it need not beeithenof the same number of phasesor the same type of antenna as that used for trans- Thus aquarter-phase receiving sysa anced transmitter'will generate an electrostatic field-which maybe represented by a single ro+ tatingvector. As long .as the. supply of power to maintain. this field isuniformly and symmletri to avoid confusion in the drawing these coils,

cally applied, the number of points of this application and the question of star or mesh connection are immaterial.

Figure .5 shows a simple form of polarized receiver, the antenna system in this case being considered as star connected, symmetrically spaced,,and comprising the antennas 31, each coupled through a coil 32, to a coil. 33, which comprises the inductor of an oscillating circuit tuned by a condenser 34, and leading into a del tector tube 38 through a grid condenser 37, and leak 38. v

Also-coupled to the coils 33, are the coils 39, whichcarry an oscillating current supplied by thepolyphase oscillator 40. As here shown the coi1s 39,,are starconnected, and have a phase sequence opposite to that of the currents generated in "the antenna coils 32, by the incoming wave. In the present instance, the output circuit of the tubes 36, comprises a T-connected audio frequency circuit having a pair .of transformers- 41 and 42, whose-secondaries supply quarter-phase current to the amplifier tubes 43 and 44, each of which is connectedto one phone 'of the-head set-4'7.

The current generatedin the coils 33, by the received wave may be represented by a single rotating vector; M i the sign of the exponent indicating the direction of rotation. As-

suming the. positive. sign, therpotential produced by the oscillator 39 may be expressed: as e i), and the potentials applied to thetube grids by the Vector sumof ,these two'expressions,

there is present in the output circuit a potential-proportional to the square of the latter term. The vector portion of this expression is (a+.1pt)+ (biqt))2 V 1 7 e (B-+ipt)+2 l +b+j(pq) l g2( lq frequencyis the difference frequency of the re ceived wave and the current generated by the oscillator 40. I

It will be noted that there is in this case no component having the frequency due to the sum of the two waves. Had the current generated by the incoming wave and the local generator had the same phasesequence, the current represented by the. second term would have contained a sum frequency only and the diiference frequency would havev been absent. Since a plane polarized Wave may be represented by two oppositely rotating vectors, a wave of this character will generate both-sum and difference frequency com ponentsin the output circuits.

. By transmitting two oppositely polarized waves, each modulated byasuitable message, on the same wave-length and from the same or diiferent transmitting points, thesewaves may be separated or discriminated between at the receiving station by theirdirec'tion of polarization-and the capacity of a single wave channel doubled thereby;- One method of receiving two-such waves on the same-receiving antenna is shown diagramdetectors 58.and 59. A threeephase current from the oscillator 6,1'isfed through the star connected coils 62 and 63, which are inductively coupled with themixing coils 56 and 57, but'these coils are so connected that their phase sequence with respect to the current from the amplifier 52, arein opposite directions.

Thus, considering-only the wave whose phase sequence in the amplifier output is a b c, it, is mixed in the coils 56, with. currents from the oscillators whose phase sequence is a c b, and the detected component in the output of detector 58 will be the difference frequency of the two oscillations. The. same wave produces currents which are mixed in the coil 57, with currents from the oscillator 61,'in phase sequence a b c, and hence only sum, frequency detected currents are produced in the output circuit of detector 59, by this wave. The wave of opposite rotation produces opposite effects. The output from the detector 58, will therefore. carry the message modulated upon one of the rotary-polarized waves from the transmitter, while that from the detector 59, will carry the message modulated upon the other wave.

It is obvious that the output of the detectors could be made responsive only to the sum frequencies, and the separation of the two waves effected in this manner. Convenience usually dictates that the difference frequencies be used,

however.

From the analogies between the difference frequency currents in the detector output to the slip currents in the rotor an induction motor or gen- ,erator, they have been termed slip currents, since as in the case of the induction machine, two vectors rotating at different speeds generate a resultant polyphase current of a frequency de-' pendent on the algebraic sum of the rotational;

speeds of the vetcors with respect to a suitable reference frame, in contradistinction to heterodyning which producesboth sum and difference currents. As has been pointed out, they comprise but a single term due to the, combination of the two frequencies fed to the detector circuit, in contradistinction to the ordinary single phase detector circuit which carries both sum and difierence frequency components.

;vectors and not their absolute magnitude.

One form of fading which is very general in ;radio communication is due to change of phase sitely rotating vectors as in the ordinary case,

one-half of its energy is not utilized in the present system. The other half of its energy is always 1 additive to that of the received free wave, and

the only effects of changes in phase of the reflected wave are to produce transient changes in pitch which are vanishingly small, and, where polyphase phones are used, to produce changes in the direction from which the sound in the phones appear to proceed which are noticed by some observers.

I claim: i 1. The method of radio communication which includes the steps of generating a rotary-polarized wave, receiving said wave to produce a polyphase oscillating current, mixing said current with a second polyphase current, and detecting the slip current generated thereby.

2. The method of radio communication which includes the steps of generating'a rotary polarized wave, receiving said wave to" produce a polyphase oscillating current, mixing said current.

with a second polyphase current of opposite phase sequence, and detecting the slip current generated thereby.

3. The method of multiplex radio communication which includes the steps of generating a pair of rotary-polarized waves having opposite directions of rotation, and discriminating be-- tween said, waves through their directions of polarization. i r

4. The method of multiplex radio communication which includes the steps of generating a pair of rotary-polarized Waves having opposite directions of rotation, receiving said waves to produce polyphase oscillating currents, and discriminating between said currents by their phase sequence.

5. The method of multiplex radio communication which includes the steps of generatinga to produce oscillating polyphase currents of op posite phase sequence, mixing said currents separately with locally generated oscillations, and detecting the slip currents generated thereby.

7. The method of multiplex radio communication which includes the steps of generating a pair of rotary-polarizedwaves having opposite directions of rotation, receiving said currents to produce oscillating polyphase currents of opposite phase sequence, mixing said currents separately with locally generated polyphase oscillations of opposite phase sequence with respect to the currents produced by the received waves,

and detecting the slip currents generated thereby.

8. The method of discriminating between received radio waves having opposite directions of rotary-polarization which comprises the steps of mixing the currents produced by said waves with a polyphase oscillation from a separate source, and discriminating between the frequencies of the slip currents produced by said waves.

9. The method of discriminating between received radio waves having opposite directions of rotary-polarization which comprises the steps of .mixing the currents produced by said waves in separate circuits with polyphase oscillations of opposite phase sequence, and detecting'the slip frequencies produced thereby.

10. The method of discriminating between received radio waves having opposite directions of rotary-polarization which comprises the steps of mixing the currents produced by said waves with a polyphase oscillation having a predetermined phase sequence with respect tothecurrent produced by the desired wave, and detecting the slip frequency produced thereby.

11. The method of discriminating between received radio waves having opposite directions of rotary-polarization which comprises the steps of mixing the currents produced by said Waves with a polyphase oscillation having an opposite phase sequence with respect to the current produced by the desired wave, and detecting the slip frequency produced thereby. I

12. A radio communication system comprising means for transmitting arotary-polarized wave, 7 Va polyphase antenna for receiving said wave, and

means for producing a polyphaseoscillation to react with the received wave to produce a slip current in a single predetermined frequency band;

'13. A radio communication system comprising a polyphase transmitting antenna, a polyphase receiving antenna; apolypha'se circuit-associated with said receiving antenna, means'for producing an oscillation in said'circuit having a predetermined phase sequence with respect to waves transmitted from said transmitting antenna, and means for detecting the 'slip current produced by the interaction between the currents generated by said transmitted Wave and the current from said oscillation producing means.

14. The method of minimizing radio fading produced by the interaction of a ground wave and a free wave which comprises the stepsof transmitting the ground wave as a plane polarized wave and the free'wave as a rotary-polar-- ized wave, and mixing the received waves with a polyphase oscillation to produce a slip current. i 15. The method of discriminatingbetween odd and even reflections of a radio wave to minimize echo interferences which comprises transmitting said wave as a rotary polarized wave, mixing the received waves with a polyphase oscillation of different frequency,- and' discriminating between RALPH M. HEINTZL

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