Патент USA US2406360код для вставки
A118» 27» 1946' w. B. ELLwooD 2,406,360 COMMUNICATION BETwEENsHIPs Filed oct. 4, 1944 /NVENTOR WB. ELLWOOD er” . Afro/MEV Patented Aug. 27, v1946 2,406,3to » UNITED STATES PATENT 'o1-‘FICE ì 2,406,360 . . COMMUNICATION BETWEEN sHIPs Walterß. Ellwood,r New York, N. Y., assîgnor - to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York v Application October 4, 1944,`Serial No. 557,194 8 Claims. (ci. 17a-t2) This invention relates to communication sys tems and more particularly communication sys ber 1928, vol. 7, pp, 762-796. See also “Magnetic hysteresis at low flux densities? by Ellwood, pub lished in Physics for July 19,35, vol. 6, pp. 215-226, and “Study of magnetic losses at low flux densi ties in permalloy sheets” byEllwood and Legg, tems employing low frequency electromagnetic fields. ’ , An object of this invention is to provide an improved communication system employing low published in the Journal of Applied Physics for or audio frequency alternating magnetic fields. ` May 1937, V01. 8, DD. 313-358. In accordance with the present invention an ~ » One possible explanation for theimproved re improved receiving device is provided capable of sults obtained at low ñelds isY that the Bark responding to extremely Weak alternating cur 10 f hausen steps are much smaller at low iields than rent electromagnetic fields in the audio Vfrequency at high ñelds. Consequently, the lmaterial re range and giving an amplified output. I sponds to smaller changes‘in' the applied field. In accordance> with an exemplary embodiment Furthermore, since the steps are smaller the am plitude of the noise dueto this-effect is smaller. ` of the present invention an elongated core o-f magnetic material is placed in the electromag suitable magnetic material which is provided When-a magnetic >device >in accordance with this invention is operated in this region it be with windings for producing voltages in accord ance with the electromagneticfñeld. In order to produces a ,considerablyÁ greater »voltage output netic field. The core has a center section of comes extremely sensitive‘to small applied fields, l improve the sensitivity of the device ,a source of 20 for said small iields, and produces less noise than is produced by the magnetic devices of the prior alternating current is applied to certain of the art. windings and the output voltage derived from other of the windings. ' . n l ' .I-Ioweven since it is necessary to operate the material at extremely low values- ofapplied field ~ Magnetic detectors and` amplifiers provided and flux, it is necessary to accurately. control ' with somewhat similar cores and windings have the bias or operating point on the magnetization been employed in the past to detect and produce curve and to balance out >'the core flux from amplified voltages in response to electromagnetic sources other than thesourcefrom which it is fields. In the devices employed for thispurpose desired to receive signals. ‘Devices of this-type in the past, the alternating current or the, alter :are capable of responding to electromagnetic nating current field has been sufficient to, or ex 30 iields considerably weakerthan the earth’s mag ceeded, that required for saturation of the mag netic field. Consequently, it is also necessary to netic material. However; the devices of the lprior balance out the ñux of the earth’s magnetic field art are not suitable rfor detecting weak fields; from the core or cores of the present device. In first, because they are not sensitive to weak ñelds; order to provide the necessary balancing cur and second, because they generate. appreciable i rents or voltages, the output of the device is ram noise which tends to mask or interfere with the pliiied and the amplified components of ythe out received signals. ^ 1 put having frequencies below the signaling»y fre In accordance with the present invention .the quency, including direct current, are employed alternating current supplied to the. device does to neutralize the earth’s field and other stray low not tend to saturate the magnetic material of -' frequency fields having frequencies belowf the the cores employed. Instead the magnitude of signaling `frequency. . ` the alternating current is maintained suñiciently small so. that the ilux in the material does not saturate the material or even approachthe so ' The foregoing objects and features and other objects and features of the present invention may be more fullyunderstood from the following de called ‘knee” of the magnetization curve. 'I'hel 45 scription of an exemplary embodimentvthereof magnetic material is operated exclusively in the low iiux density region where the magnetization -curve or the hysteresis loop is approximately defined by Rayleigh’s law. >The manners and _modes of operation-.of magnetic material'` inthe lo‘w'- flux reg-ion is described >in greater detail in La paper kry E.v Peterson entitled “HarmonicPro yductiomin ferromagnetic materials at` low-fre quencies an'd low yflux densities”'and published «inthe Bell' System Technical* Journal for Octo 55 when said description is read‘with referenceïto Y the drawing-which shows in schematic form the various elements' which cooperate to -provide an improved receiving‘device for receiving -audio fre quency electromagnetic waves. The following de scription is not in anyway intended to limit or increase the scope of ‘the claims appended hereto .which` speciiicallv` point out the novel features of this invention. y f l - - ~ Referring now to the drawing l and 2 repre ,t 3 , to a paper published in Journal of Applied Physics for May 1937, vol. 8, pp. 313-358 by Ellwood and Legg entitled “Study of magnetic losses at low flux densities in permalloy sheets.” Output terminals 23and 24 areconnected to» ' ¿band-pass filter II. The bandfpass filter II may be of any suitable type and as shown in Fig. 1 is frequency or frequency range but may be em designed to pass a frequency lrange of from 940 cycles to 1060 cycles. This band-pass filter is em ployed to prevent the higher harmonics and ex ployed'in magnetic fields of any suitable fre quency. Inasmuch as such low frequency fields,Y are frequently employedl in communication be 4 “Magnetic hysteresis at low flux densities” and sent an elongated core of magnetic material. This core is placed in the region where the mag-1 netic field is to be detected. For the purpose of illustration, it is assumed that it is desired to receive an electromagnetic field of 25 cycles. It will be apparent to persons skilled in the art that the invention is not limited to any particular` traneous noisekfrom affecting the operation of the remainder of the system. Band-pass filter I I may be of any suitable type typical examples of 15 whichr are described in detail in United States >-Patents 1,227,113 and 1,227,114 granted to Camp tween ships the core will be madeY relatively long> y and mounted aboard ship preferably above- deck and away from the major portionV of the magnetic material and structure of the ship, as -for example, 10 to 15 feet above the Ideck of the ship.' When desired this coreand coil structure vmaybe made ' in the form of a cable and towed by the ship. It may be necessary to float the device inquiet water if extreme range is desired. ` bell onMay 22, 1917, or any ,suitable modiñcation of such filters. The output of the filter I I is con nected to an amplifier I2 which is capable of am 20 The core- is'composed ofv a plurality-of sections 'I,v 2.' and 3, as lshowni'n Fig. 1; ï These core sections maybe made of ‘any suitable magnetic material as, for example; any of the various iron-nickel -alloys-which have a high'permeability at low 25 Imagnetic ñelds. The core sections I and 2 are separated by cen ter section 3 comprising a magnetic core having at least two legs 4 and 5.l The center section 3 is 30 made of magnetic material which possesses eitherl a'high hysteresis coeñicient or a high rate of plifying the frequency-band passed'by filter II. Such amplifiers are well'known and operate in their usual-manner when> employed in combina tionwith the other elements of the present in- v vention. The output of ampliñer I2 is connected f to thein'put »circuit of a mixer or modulating ‘de -vice I3. A source of alternating current I0, which may be 1000 cycles in the specific embodiment shown in thedrawing, is also connected to the mixer I3 through a suitable attenuator I4. The -attenuator I4 may be of any suitable type and usually comprises a ‘resistance network, certain elements of which are lusually variable. ' ` I2 Mixer I3 combines the output of amplifier v - change of permeability'witn field at low values of ' applied field or flux or both. A particularly Suit _ and the output of the-attenuator I4 Iso as to ob able type >of core material is' describedin-detail tain an output which is a product of the input in the United States Patent 1,768,443 granted toY V35 from theampliñer I2 and the attenuator I4. The -Elmen June 24, 1930, which -patent is hereby made mixer or modulator I3V may be of any suitable part of the present application by reference as type which are well known as mixers or first de . if fully' included herein. Howevenit can be shown tectors in the so-called “heterodyne” or “super that-'the device is most effective when the per heterodyne” radio receivers. Receivers of these .meabilities of sections I, 2 and 3 are high and 40 types are described in greater detail in “Prin approximately equal while the material of the ciples of Radio» Communication” by Morecroft, third edition, 1933, on pages 1035 through 1040, also pages 634 through' 646 Vand 765 through 774. .center section 3should have either as high a hys teresis coeiiicient orf as high .a rate of changeV of permeability with ñeld as possible or both. Each of the legs 4 and 540i the center section Vof the core is provided with two windings, 6 and 8, “and 1 and 9, respectively. Windings 6 and 1 Vare vconnected to a source of alternating current .I0 having a frequency which is high compared to the For more modern mixer circuits reference is made 45 ’to chapter 15, pages 99 through 114 of “The ture comprising sections I, 2 and 3„no voltage if fully included herein. The high-pa'ssïiilter I5 Radiotron Designer’s Handbook,” third edition, by F. L. Smith. - The output of mixer I3 is connected to two »ters I5 and I6. Filter I5 is a high-pass ñlter while ~ highest signaling'frequency or vcomponent there V50 fil/ter I6 is a low-pass filter. These two filters of 'to be transmitted while windings 8 an‘d 9 are ‘may be designed and connected together in any connected to the receiving system as will-bel de suitable manner, as for1 example, as described in . scribed hereinafter.' . , greater vdetail in United States Patent 2,076,248 The windings B, 1, 8 and 9 are so connected granted April 6, 1937 , to Norton which patent' is relative to each other that when no external maghereby made a part of the present disclosure a-s l netic ñeld is applied to the composite core struc rappears across the output vterminals 23 and v24 of coils 8 and 9 even when the windings 6 and 'I However, when an 60 . are connected to source I0. external field is applied tothe core structure com » prising elements I, Zand 3.a voltage is produced is connected to an output amplifier I'I which is in turn connected to anysuitabledetector or receiv ing :device I8 responsive to the low frequency sig nallingcurrent.- In the exemplary embodiment of the. invention described herein this'low fre quency current may be either a `25 or 50-cycle current or both depending upon the bias or op material or due tothe change in the permeability 65 erating point vof the core..y Device I8 may include any suitable receiver'such as a headset,-sounder, of the core material orY >both as described in the -between terminals 23` and 24. This output voltage maybe due to either theY hysteresis of the core above-identified publication by Peterson. All. of the above-identified publications are hereby made recorder, or printer, as for example,»a printer of the type shown Lin' United States Patent 1,904,164 V,granted to S. Morton et al. on Aprí1 18, 1933. 70V . Low-pass'iilter I6 is designed to pass all fre quencies below some cri-ticalY frequencyA which , For amore detailed description of the response a part of ythis application as ifA fully included herein. » f . ' of ferromagnetic material in weak magnetic fields and the application of Rayleigh’s law, reference is made'to a paper published in Physics for July .1935, vol.- 6,_ pp.' 215-226k by Ellwood, _entitled critical frequency is below the desired signalling lfrequency. Assume’for purpose> of illustration *thatV filter I6 passes all' frequencies below Y10 cycles. In view of .theifact that the" interfer 2,406,360 5 ence usually encountered in systemsof this type Vis ofalow~ frequency; hfghand low-pass `filters ~will..be..sufltcient to.' separate the. signals< and in. .terferencac In case high frequency interference -is alsol encountered a `band-pass flltermay be; em. .ployed for filter I5 and a band elimination ñlter for filter I6 as will be readily understood by per Sonslskilled in the art. f ` .The output of filter I6 is connected through a a voltage relatedto the valueof the applied field is obtained from the _output of «mixerA I3. yThe high frequencyory signalling component of this vvoltage passes through the highfpass I5 andam Aplifier I'I to thereceiver I8 while the lowjfre yquency component passes- through iilter„|6,`am `plifier I9, manually controlledpower supply`24, phase control apparatus 20,> the kmanuallycon vdirect lcurrent "supply circuit 2| to Wind manually .controlled directcurrent power supply 10 -trolled ings'26 and 21, where* these currents tend to bal .device 24 to amplifier I9 which. amplifier is a so ance ,out the steady and low frequency compo .called direct. current amplifier because itv will i nentsof the applied field.> In this manner.` cores >amplify. continuous aswell as alternating Acurrent 4 and 5 are in effect subjected to only the signal .voltages and produce a continuous as well as an field orV fields having frequencies of the desired ¿alternating current voltagelor vcurrentï- output. 15 signalling frequency band. In~ this manner itis output of amplifier. I9 is connected to a possible to maintain the total fiux through the ` phase control circuit 20 which >is provided to cores 4 and 5 to an extremely low value and thus properly control the phase of the current to be 'provide the maximum 'sensitivity for the device. .fed back t0 the windings 25 and 26 on the core In case it is desirable to apply a small biaspto sections I and 2 respectively so the entire detect 20 the core structure lit will be` necessary Ito accu ing> arrangement will be stable. For a morecom rately control' the magnitude of the biasso that plete description of a phase control equipmentv 20 the total net or effective >field applied tothe >core and the requirements thereof, reference is made .Will not extend beyond the desired region. Fur to an article entitled “Relation between attenua it is necessary toacCurately :control tion and phase in feedbackv amplifier design,” by 25 thermore, the operating point to increase the stability and H. yW. Bode, inv the Bell .System Technical Jour reliability‘ofv -operation of the device. ' I Í na1,'vol. 19, July 1940, beginning on page 421, l Inorder to apply a bias to the core source 2| which article is hereby made a part of the pres or more usuallyk `24 will bef-adjusted to supply -a ent application as if fully included herein. small voltage which will either add to orzoppose Y As shown in the drawing, the output of the 30 the. earth’s field. , 'I'he veffect. of this vvoltage'will phasecontrol apparatus 2i)v is connected to a bereducedl due to the operation of the feedback manually .controlled> direct current power sup circuit. However, a small fraction of this volt ply. In the exemplary embodiment of this inven age will still be `effective and act as a small bias tion shown in thel drawing, themanually con trolled power supply comprisesy two batteries 22 or other suitable source» of direct current and a manually controlled potentiometer 23. The for the core structure.> , Under these circum stances the operation. of the. remainder of the‘cir‘ cuits and apparatus rwill be as described above. Due to the degenerative action of the feedback arrangement the effect of. small changes in the manually l.controlled power supplies 2| and> 24 may be employed Ito control the. bias or operating magnitude of sources 2I vand 24 lare reduced so . point: of the core ofthe device.. The manually 40 that the bias~ is accurately maintained atpthe controlled supply 2| may also be used to relieve desired level and at the. same time the effects. of the amplifier I9 and the.- remainder of thewsys tem'> ofv alarge part of the. burden cfproviding the yvery low frequency and direct current necessary .to counter-balance the. earth’s field. Usually supply 2|; will be employed to reduce the output required froml amplifiery while supply 24 will be Y ,used to accurately control. the bias or operating stray fields. and currents, including the earth’s field, is largely balanced out of the core soits sensitivity to the desired field or signals will be maintained, f ` In the foregoing description reference has been made tospecific types of equipment suitablefor use in combination with the other elements »of point of thefmagnetic materiall of the core struc the present invention. Persons skilled'in the art,> ture of the entire device. If' the device isy located 50 however, will readily appreciate that many otherA aboard. ship and supply 2| is used to reduce the types of equipment andA apparatus aresuitable burden on. amplifier I9 it will be necessary to pro for the various components of the present» inven vide a. chart or table or both, showing the posi , tion and may be employed therein without mate tion of thee ship.V asv well as its bearing and indi rial modification. 'I'his invention‘is accordingly cate the proper setting of the manually con 55 not limited toany‘ of the specific devices specif trolled power supply system. ically referred to above. _f As: -will@ be readily understood »by persons What is claimed is: I I -SkillerlA in' the art, the manually controlled sup 1. In a.> communication system a receiving> de ply 2l maybe completely eliminated by providing viceÍ comprising an elongated core of ferromag properly designed amplifier, ters, and phase 60 netic material, a. center portion thereof having a control circuitsV if it is so desired. - high rate of change of permeability with low val The output of the phase control and manual .ues ofA field; intensity,V meansV for applying a low ' supply system is connected to' coils 25 and 26 amplitude. high frequency field to said core,A a re surrounding .the coresections I and 2. respectively ceiving amplifier, windings'- on said core connect amt-aire> so.v connected as' to produce a flux which 65 ed to said amplifier, and~ `feed-back;windings also is in- opposition'r to and neutralizes the flux pro duced by the4 external magnetic field applied to thecore structure I, 2 and 3*., , VAupon. saidcore connected> to said amplifier for neutralizing the. effects upon. said core of »all fields applied thereto. except a field having the >In operation, the core structure I,> 2 and 3 is same frequency as the signalling frequency of said ' >mountedfin- apositionso as to be subjected to the 70 system and except said high frequency ñe'ld. -electromagnetic field which itis desired to receive `2. A receiving device responsive to electromag from., When.- an external field is applied to this netic waves. comprising a core' of ferromagnetic cores structurel voltages will be> induced in leads material, means for providing a plurality of mag 23 and 24 which voltages are amplified by ampli neticlpaths through a portion of" said core, apf ñerlî Iì2î and their dëmodulated by mixer 23 so that 75 'vpar'atusî for applying a low intensity high> fre' 2,406,360 7 quencyA field tof'each ofsaîd paths in different' di rections orïphases, loutput -windings interlinking 8 ingìthe> plurality of said pathsand connected.A so ' that nov output 'potential differenceîis'developed saidîmagnetic pathsî and. connected in* Vsuch va manner: that no output voltage is wdeveloped. across across. the output terminals: thereof. ,whenïn'oï ex yternall'field is applied tojsaid core; an amplifier connected to' saidoutput terminal, ya _mixing or »said windings when no external 'field is applied cn modulating device; connected to 'the .output .of _said ` Vto saidcore, an amplifierconnected to said out-` amplifier and to said high„f'requencyr :source -for put windings, 'feedback windings. also interlink?, developing a voltage having afrequencyiwhich’is the said core, >operativeïconnections between 111g _the difference between' the 'frequency 1of.- saidzout'saidA amplifier andsaid' feedback windings“ for put’voltagefand the frequency of said high-fre. 10 »neutralizing the effects of all external fields upon »quency current, filter equipment connected to the lsaid core and; means rendering said=neutralizing` Y output of- said mixing equipment for` selectingthe windings' ineffective. at the signalling .frequency signal frequency- 5 thereof, :feedback windings<„also interlinking said core, connected'equipmentffor Íof:said system. , . ' - ` > - , . ‘ >3. In a telegraph system .9, Vreceiving device comprising a long core V.of ferromagnetic -mate-` ' connecting said feedbackV winding tosaid feed ` ’ rial, acenter portion thereof having a, plurality of magnetic paths and composed of ferromagnetic alloy having a high rate of'change of permeabil ity atlow values of field intensity, a source of relatively high. frequency alternating ' current, 20 windings'interlinking said plurality of paths'con-` nected to said source of high frequency current -forvapplying to said magnetic paths an alternat-` fing. current, field of low intensity’ in the; region `wherethe hysteresis loop of said material is de fined by Rayleigh’s law, output windings inter linking said magnetic paths, a receiving ampli-` back equipment so as to `feedbackall frequencies exceptlsaid signalV frequency and Íthe, frequency .of said source, and'phase. control equipment for causing the phase’of. all l,of thefeedbackcurrents to substantially'neutralize all _the externalfields applied to rsaid core exceptÍ the.I signaling-:fre quency. Y _. 1 „ f_f 6. A Vmagnetic-,device responsive to A.magnetic fields comprising acore'structure-of laminated ferromagnetic material, a source-.of«¿high .fre quency alternating currentpower supplyïforlsaid device, power windings connectedto saidsource and >interlinking said core, voutput windings also interlinking’ said core and connected '.to'output connected to said filter networks, and feedback 3.0 terminals for developing a voltage betweenfthe output terminals which is'a function of the exter fierîconnected to said'windings, .filter networks -connected to( said amplifienia receivingî device windings interlinking said lcore also- connected Vto ` nal field applied to said core, a mixer or ,demodu- ' said network for maintainingy the total field with in said magnetic material in Yal1 except lthe sig nallin'g frequency range and the frequency of said source within thelregionv wherein the hys 35 and to Vsaid sourceofhigh frequency „alternating teresis loss is defined by >lìtayleigh’s law. ' 4; In a telegraph system a receiving device the applied'external magnetic ñeld. lator connected Vto said outputwinding 'terminals current for deriving an output havingV a wave form substantially the samev as the wave' form .of ' " 7..,Asignal receiving device,..comprising a.core of ferromagnetic material, alternating current magnetic paths and .composed of ferro-magnetic ,40 power supply windings interlinking said core, 'out' put windings interlinkingv said core Aand connected Vallow having 'a high hysteresis coeñicientlfat low to` develop an output which isfjointly afunction values of field intensity,l a source of vrelatively of said’power supply alternating current and all high frequency alternating current, windings in other magnetic ñelds to ,which saidcore is "sub terlinking said plurality- of paths connected to comprising a long core of ferromagnetic material, a> centerV portion thereto having a plurality of said source of high frequency current. for apply ing'to said magnetic paths Van alternatingcur -rent field of vlow intensity in the regionk where the hysteresisY -loop' of said material is defined by jected, a mixer or demodulator .connected to said output windings and provided with a power input terminal for deriving an output having a'wave form substantially the same* as the .wave »form'of f the magnetic field to whichsaid core is subjected 1Rayleigh’s law, output windings interlinking said V`magnetic paths, a receiving amplifier connected 50 vexclusive of the field created by said power sup' ply windings, feedback windings 'interlinking `said to said windings, filter networks connected to said core, filter and phase control networks‘connected _ampliñen a receiving 'device connected to ’said >between said mixer andY said feedback windings filter networks, feedback windings 4«interlinking Vfor re'ducingfthe field to which said core is sub' said- core also connected :to said networks for maintaining the total fieldiwithin said> magnetic 55 jected except for specified> frequencies or fre‘ material in all except the signalling frequency -and the frequency of said source range within the ' region wherein the hysteresis loss is defined by quency ranges. , .f " fp l „ Y 8.- A magnetic device responsive- to external » magnetic fields comprising a >core of ferromafg- f vnetic material, a source of Valternating current of direct current connected in said feedback wind 60 having a frequency which is high compared tothe frequencies of said external vfield'torwhich said ings for neutralizing the effect of the constant ,device is responsive, .power windings interlink-v Y portion of earth’s magnetic field upon said core. ingv said core, outputrwi'ndings also'interlinking 5. Apparatus responsiveV to electromagnetic -said core for developing ayoltage which is- a func' fields comprising a core structure including end sections and a center.section,'a plurality of mag 65 tion` of the external >field rappliedrto. saidî core, Rayleigh’s law, and amanually controlled source feedback windings also interlinking's'aid"core,` a Yfeedback circu'itsextendingv from'said output tei" minals- and including said feedbackïwindings'to current power supply windings interlinking said supply current to said feedback‘windingsV t‘o »neu paths through said center section, a source of rel atively high frequency alternating current', in 7,0 tralize- a portionof the effect of the externalfield applied. to, Vsaid'c‘ore, a -directA current., source' of terconnections betweenv said ysource and said 'potentialïconnected in said feedback-circuitîï'to windings for supplying alrelatively high fre--v rapplyya bias 'to' saidY core through said feedback quency alternating current field vof low intensity to each of said plurality of paths ina different netic paths extending between each of ' said end ' Ysections through said center section, alternating windings;v` ,phase> relation, outputj windings „also interlink; 75 ¿l ' ^ ~ ' f p ’ ~» .Y ‘ . _Y f , ., ;, ,.