US2789285A

US2789285A - Directional radio systems

Info

Publication number: US2789285A
Application number: US322102A
Authority: US
Inventors: Ortusi Jean; Robert Andre
Original assignee: CSF Compagnie Generale de Telegraphie sans Fil SA
Current assignee: Thales SA
Priority date: 1951-11-27
Filing date: 1952-11-22
Publication date: 1957-04-16
Anticipated expiration: 1974-04-16

Description

A ril 16, 1957 I J. ORTUSI ETAL 2,789,285

I DIRECTIONAL RADIO SYSTEMS Filed Nov. 22, 1952 I 4 Sheets-Sheet 2 INVENTDKS N RFUSI ANJR Rosenj, AGENTS i l 5, 1957 J. ORTUSI ETAL 2,789,285

' mamc'rroum. RADIO SYSTEMS Filed Nov. 22, 1952 4 Sheets-Sheet s PULSE GENERATOR SYNCHRO. VOLTAGE 6 GENERATOR.H [L5 F 1 v i 6 in C SAW-TOOTH 6, GENERATOR 64 W .8 \l\l\l\l g p I f I 7 v6 r fl INVENT'MS JEAN ORTUSI mum R am To. AENTs April 16, 1957 J. ORTUSl ETAL 2,789 ,285

DIRECTIONAL RADIO SYSTEMS Filed Nov. 22, 1952 4 Sheets-Sheet 4 2 2 L3 E E 3- 85 g5: p. u 5 525 1 u H90 6 'lNVENToRs JEAN oxruslmwfiiin 31 ra a.-

AGENTS United States Patent DIRECTIONAL RADIO SYSTEMS Jean Ortusi and Andr Robert, Paris, France, assignors to Compagnie Generale de Telegraphic Sans Fil, a corporation of France Application November 22, 1952, Serial No. 322,102

Claims priority, application France November 27, 1951 9 Claims. (Cl. 343-107) This invention relates to directional radio systems and more particularly to directional radio systems for use on very high frequencies.

Very high frequency directional radio transmitting and receiving systems are often required, for example in apparatus of the radar type, for obtaining the accurate bearing or direction of a target. They are also required for ascertaining the direction of an incoming ultra-high frequency wave and for other purposes.

In general, most known directional radio systems, whether transmitting or receiving, depend for their operation upon the directional qualities, i. e. the polar diagram of a transmitting or receiving aerial.

However, the polar diagram of an aerial, even an ultra short wave aerial, cannot be made as sharp and narrow as is desired except by making it of such dimensions as to be very inconvenient if not impracticable. In practice, it is difficult if not impossible to make the angle of the principal lobe of the polar diagram less than a few degrees, and consequently the directions taken with an aerial having such a diagram are prone to an angular error of at least a few degrees.

It has been proposed in directional radio systems to make use of two overlapping polar diagrams. By oscillating an ultra short wave aerial between directions defining a small angle between one another, and symmetrically disposed one each side of a predetermined fixed direction which bisects that angle, two polar diagrams which overlap are obtained, said predetermined direction being termed the axis of the system and being characterised (if the diagrams are identical) by equal field strengths. The axial direction is thus easily determined by reason of this equality of strength but any other direction off the axis can only be determined by making absolute measurements of field strengths obtained on the two diagrams, a complex and ditficult matter and one prone to considerable error in view of the liability to erratic atmospheric field strength variations. Measurement of absolute values can be avoided and any direction can be determined by arranging for mechanical movement of the aerial system to bring its equi-field strength axis into the direction to be determined, but this expedient has the obvious difficulties, defects and disadvantages inherent in mechanical movement, more especially the difliculties of training an aerial accurately over small, accurately measured angles and changing direction rapidly.

. The present invention has for its object to avoid the difficulties and defects above referred to, and to provide improved and simple radio directional systems whereby directions may be determined rapidly and with precision without requiring any mechanical movement of the aerial system used ,and without involving absolute measurements of field strengths and whereby the momentarily determined direction may be swept, rapidly if desired, through an arc.

According to this invention, two overlapping polar diagrams are produced and the relative amplitudes of these 2,789,285 Patented Apr. 16, 1957 "ice are varied in accordance with a predetermined periodic law to vary the direction ofthe axis of the system. The periodic law of amplitude variation may be a saw tooth law, but other laws are possible for example triangular.

A system according to the invention may comprise a Y directional aerial with two associated wave guides providing two overlapping secant polar diagrams having their maxima at a small angle to one another, the required amplitude variation being obtained by electrically controlled means for oppositely modifying in alternation the transmission coefficients of the guides. Instead of using two guides and a common aerial there may be two separate guides and aerials.

The electrically controlled means associated with each guide may be a magnetron, the fields of which are such, that it cannot oscillate, said magnetron being coupled to its guide so as to impart therein a variable impedance dependent on the anode cathode voltage of the magnetron, control being effected by varying this voltage.

Control may be effected by producing two square waves which are applied one to each of the two magnetrons, these waves having impulses and intervals of equal durations and having their pulse amplitudes varied in opposite senses, said waves being applied to control said magnetrons sothat when one cuts ofi its associated guide the other opens its guide introducing therein a transmission coefficient proportional to the impulse amplitude and vice versa.

For transmission the two guides may be fed from the same source of energy of very high frequency.

For reception the two guides may feed a comparison receiver adapted to determine the moments of input signal amplitude quality from the two guides.

The invention is illustrated in and further explained in connection with the accompanying drawings in which:

Figure l is a graphical figmre illustrating the polar diagrams of a known equi-field strength system, the abscissae representing angles and the ordinates the field strengths.

Figure 2. is a similar graphical representation illustrating the operation of this invention.

Figure 3 is a block diagram showing principal parts of a system according to the invention.

Figure 4 shows diagrammatically a transmitter system embodying the invention.

Figure 5 shows an electronic modulator which may be used in the system of Figure 4.

Figure 6 is a curve connecting the transmission coeflicient in the region 30 of the guide 3 of Figure 5 with voltage V applied at point a to the magnetron in Figure 5.

Figures 7 and 8 represent graphically voltage waves for application at a, and a respectively of Figure 4 in order to sweep the axis of field strength equality through the desired angle.

Figure 9 represents in greater detail the generator 7 of Figure 4 which provides the voltages of Figures 7 and 8.

Figures 10 and 11 represent two recurrent voltage wave forms for the generators G1 and G2 used in Figure 9 for modulation to obtainsweeping of the axis.

Figure 12 represents diagrammatically apparatus which may be connected to the apparatus of Figure 3 to provide a receiving system.

In the well known so-called equi-signal method of determining ultra-high frequency signal direction conventionally illustrated in Figure 1, an aerial has its direction alternated between two values x(+a,,) and x(-u such that there are two overlapping identical polar diagrams L1 and L2 alternately produced, overlapping on the-"line :OX (0) -with "regard to which they are symmetrical, the't-wo diagrams A appearing-alternately in. an predetermined rhythm or periodic manner. The direction OX(0) is characterised by the existence of the same field--strength---whichever d-iag-ra'm L-i or-Lz is-present.

In order to ascertain the direction of a signal 'in'some other-'di-rection x'(u-) making an angle a with OX(0), either the whole system must be swung :through the angle a to point in the new direction, or the field strengthens Ei andIE'z due to-the diagrams L1 and'L'z respectively must be measured, the difference (E 1-Ez) enabling the value ofu'to be deduced if: the forms of the diagrams L1 and L2 are known with precision. It is, however, usu-. ally not convenient to swing the who'le=system,'= and it is "difficult to ascertain. direction "by determining-.E1E2 with an acceptable degree of accuracybecausethe absolute 'values' ofsthe fields :E'i and E2 must bemeasured.

According to this invention, two polar radiation diagrams which are symmetrical as regards directivity with relation to .apredetermined: direction are producedand are varied: .in amplitude'in opposite senses in accordance withua predetermined periodic law of variation, so that; when the diagram: to one side of said predetermined. direction is being increased in amplitude, the other is being decreased andvice versa. This-is illustrated in Figure :2 fromlwhich it will be seen .thatall the diagrams to the leftof OX(o)the predetermineddirection.- have directivity'x(a while all those to the right have directivity x(+a the two directives being. symmetrical about the axis'O(-X)o. Six' diagrams are shown, three, L11,.L12, L13 of diiferent amplitudes to the left of.the axis: andu three L21, L22,, L23 of different amplitudesto the right of the axis. The order of productionofi these diagrams is L11 and L21 then L12 and Leg. and then L13 and L2: and so on, the'diagram amplitudes on. ORGY-Side, increasing while those on the other'decrease and, vice versa. When'the diagrams L11 and'L21 are produced, theequi-field strength condition will be produced" for the direction x(+a,) at an angle-H: with the'axisr Whendiagrams L12 and L22 are produced, theequi-field strength direction is the axial direction and whennLuaandxLaa are produced, the equi field strength direction is the direction X(+a,). Although. for sirn-. plicity in drawing, only three diagrams are shown each sideofthe axis, in practice the number employed is very highit may be infinite-sothat as the amplitude on one side increases and that on the other. side decreases and vice versa, the direction of 'equi-field strength. sweeps through an angular sector (x(-a to.x(a

and back. It is preferable to make use only ofthe-substantially linear'regions of the diagrams'thereby toiavoid possible ambiguities, and generallyv to increase the precision and the simplicity of the :apparatus.

An'apparatus for carrying out the invention may comprise as represented diagrammatically in Figure '3, an aerial system 5, 6 constituted by a reflector and two horns. (not-shown) or; by two reflectors each having an. associated horn. The aerial 5, 6 is fed from two' wave guides 3 and 4 which lead to the two horns, one to each (slots or dipoles may be used instead of horns), which energise the aerial. The arrangement is such that when the, feeds to the two horns are equal thegaerialhas two substantially identical overlapping polar radiationdiagrams in directions OX(a )OX(-u which are.v symmetrical with relation to the axis O(x,,). Associated with the guidesS, 4, is-a device 1, 2 electrically controlled by control means 7 as represented by theeleads b,, a,, b,, a,. The device 1, 2 which is controlled, isinessence a variable attenuator arrangement adapted. to modify: the transmission coeflicients of the; guides: so as toincrease-that of guide 3- anddecrease that'of; guide 4 (and. viceversa) smoothly and similarly. The portionsof theguides in advance of the ditferentialat-tenuwtion control'device 1; 2 are; marked 3"and:4-' andiwhen the arrangement is used for directionalv transmission,

4 these are connected to transmitter apparatus for equal energisatiom For... directional. reception... theyt alter. of, course, connected to receiver apparatus.

Figure 4 shows another arrangement which is similar in principle. In Figure 4 there are two distinct aerials or horns 5' and '6' fed fromethe wave guides 3 and 4 respectively. The guide parts 3' and 4 are joined and fed from a conventional:ultra-high.frequencytwave transrnitter.8 such asa magnetrontransrnitter. The wave.

signed for transmission of H01 waves. The. oppositely acting attenuation control means-the means 1, 2 for modulating the transmission coeflicients :of the guides in ure 3 ar.e-.shq n F ure. 4 .as constitu eiby W distinct and separate units 1 and 2, both controlled by the device 7.

Figure 5 shows one suitable form which may be used for attenuation control e. g. for insertion between guide lengths 3 and'3 in Figure-4; In Figure 5, a magnetron Mu' having a cavity anode connected to-earth and aIi axial cathode K heated by a heating filament (not-shown) has the electrical control voltage from; device-7i'(not shown in Figure-5) applied toits cathode front terminala,. pendicular to the plane of the drawingand' is produced" by a magnet of known-type not shown. field and the electric voltage:v applied at a,- are never suchi-as-to perrnit'themagnetron Mn to-oscillatet The magnetron: is coupled; for ultra-high. frequency, with a branch zguide Ba by means ofr'a probe conductor- S. The 1 depth of penetration ofithe prdbe s into the-branch 3ar and' the position: of: a:. piston adjuster P of well 'known forrnprovided' in the end fot the branch=3a are adjustedexperimentally by trial and.:error.-.untili the assembly con sisting of the-branch and1its associated equipmentproduces a. desired'meanvalue of-transmissio'n'coefficientfrom.3.to 3, or in the:oppositeadirection to= 3; As= already -stated: ithe whole. arrangement :is suchtthatwover thewhole range of variation of: the. control voltage-a1) plied at a,, the magnetron cannot. oscillate, and. thus forms a .passiverimpedance with regard to-t-heguidei. This impedance isphowever, variable as a function of the volt-1 age. appliedra-t a This variation is caused byvariations. ofwthe: space charge. around-the cathode.- of themagnetron t Mo-under the influence of variationsof the: electric volt-. age; applied at-a the said variations of: space: charge modifying theimpedance proper Y of the: magnetron twith= regard'gto the-ultra-high frequency waves which circulate in the guide.

Referring to" Figure Gwthe arrangement 'of -Figure.;5. is. experimentally. adjusted so; that of zthe voltage applied at a,- varies; from Vm. to Var, the transmission coefficient. of. the guide: 3101.3" variesv between; Tfm and T'M. The: values 'Oflvrn andrVMareso chosen that operationuoccurs in, the region; whereathe; transmission coefficient- T at point 30, (Figure 5 variessubstantially: linearly; with relation to V; T'mis much lower than unity, so thatthe: guide ispractically cut off'if' the voltage-appliedz at a is below Vin while T.'1vris.in the neighbourhood ofiunity soth-atwith; voltage Vu applied 'theguide is practically: without attenuation at 30.

Thus by applyingata anda (from b and b,) .voltagesas representedzin Figures 7 and 8 respectively, i. et voltage impulses. of. duration T, and' of: amplitude varyinglinearlyas a;function Qf'timein the indicatcd sense, one offthe-guides. will be blocked (T"=0) at any-moment whilst-'theother' offers a transmission coeflicient T""l'ying betweenxT'm and' T'rvr, and vice versa. T varies linearlyasa-function of'time in an opposite sense for thetwo lines; Thuslthe system ofrFigure'4 constructed as described withreference to Figure 5 and controlled by vol-tages as 1 represented in Figures 7 and-'8 will produce-the changing transmission polar diagrams as-described with reference tozFi-gure 2:

The voltages represented intFiguresJ'and 8: are sup- The-magnetic field of the magnetron is per- The magnetic plied by the control device 7 of Figure 4. Figure 9 shows one form for this control device. It comprises a periodic synchronising voltage generator G which controls a generator of square waves or pulses Go in which the pulses and the intervals between them are of equal duration. This generator (it) supplies two such pulse trains or square waves which difier only in that the maxima in one wave occur simultaneously with the minima in the other one wave. One wave is applied to the control grid g1 of one of two conventional triode tubes and the other is applied to the control grid g of the other. These grids are connected to earth through resistances R and R of large values and they also have applied thereto modulating voltages which periodically vary in opposite sense in accordance with saw tooth laws, these voltages being supplied by saw tooth generators G and G2 synchronised by the synchronising generator Gs- The outputs from the'anodes A and A2 of the two triodes are taken from across resistances R1 and R2 through which said anodes are connected to a source of anode voltage at +HT. The triodes are operated over the linear parts of their characteristics. Voltages as shown in Figures 7 and 8 are obtained at b and b,. It is to be understood that the duration 1' of the pulses and the period T of increase and decrease of amplitude of the said pulses are related by the expression n being other than a whole number.

The modulating voltages V0. VG2 supplied by the generators G1 and 62 may be, as already stated, saw tooth waves as shown in Figure 10, in which case the equi-field strength axis of the system will sweep across in one direction and return sharply, the transmission or reception circuits (as the case may be) being blocked during flyback. It is, however, possible to modulate by voltages V0. V6 as shown in Figure 11, in which case the axis will sweep back and forth at the same speed. This form of law is herein termed a triangular law.

Of course, modulation may be effected in the triodes of Figure 9 by superimposing voltages from sources G1 and G2 on the anodes of the valves or in any other known way.

Figure 12 shows receiving apparatus which may be used in conjunction with the apparatus represented in Figure 3 to provide a receiving system.

Referring to Figure 12 the guide parts 3 and 4' (of Figure 3) feed into detectors D1 and D2 whose modulation outputs are fed to a comparison circuit C. The latter controls one pair of deflection plates P and P1 of a cathode ray tube 05 which are arranged to supply a vertically deflecting signal thereto when the outputs from Dr and D2 are equal. The second pair of plates P2 and P2 is controlled by a time base generator Ba, which is connected to the comparison circuit C through terminals C1, C2 and the lead shown, this connection serving to synchronise the time base by voltages detected at Dr and D2, so that the said time base is synchronised with the period of sweep of the axis. Accordingly the trace of the spot on the screen of the cathode ray tube will exhibit a peak indicating the direction of the incoming signal.

In the arrangement of Figure 4 as described for transmission, the ultra-high frequency energy supplied by the transmitter 8, may be continuous wave energy as has been assumed. It is, however, equally possible to use a pulse generator at 8 i. e. a generator supplying pulses of ultra-high frequency. In this case the pulse generation is preferably synchronised with the unit 7. This is indicated in Figure 4 by a connection c-d. The terminal d of unit 7 (Figure 4) then corresponds to the terminal. d of the synchronising generator Gs of Figure 9. With this arrangement the impulses from generator 8 will coincide with those of Figures 7 and 8 (and thus with those of the generator Go in Figure 9') and the said impulses from unit 8 will be inside those of Figures 7 and 8.

Again if desired, transmitter 8 may have supplementary signal modulation for synchronising the time base sweep of the cathode ray tube in a co-operating receiver. Where the transmitter is thus modulated, a co-operating receiver may be of known type, or it may be as described herein. Where however an ordinary transmitter is used, the receiver must be as described herein.

We claim:

1. A method of radio direction determination by ultrahigh frequency waves which consists in producing alternately two overlapping radiation polar diagrams whose line of intersection defines the direction, and oppositely varying the amplitudes of said diagrams according to a predetermined periodic law having a period substantially greater than the duration of the production of said polar diagrams.

2. A method as claimed in claim 1 wherein the said law is a saw tooth law applied so that the variation of amplitude of one of the said diagrams is in opposite sense to that of the other.

3. An ultra-high frequency directional radio system comprising radio directional means connected with two wave guides and adapted to provide, in cooperation therewith, two secant polar diagrams which overlap, the maximum directions of said diagrams being inclined to one another, and electrically controlled means in each of said guides for modifying alternately the values of the transmission coefficients for electro-magnetic waves in said guides in accordance with two similar but opposite periodic laws of increase and decrease.

4. A system according to claim 3 wherein the said electrically controlled means comprise two magnetrons each having an anode and a cathode, means for applying to said magnetrons magnetic and electro-static fields such that they are always outside the range of self oscillation, means for coupling one of said magnetrons to each of said guides to impart therein a variable impedance dependent on the electric voltage applied between the magnetron anode and cathode, and means for varying said voltage.

5. A system according to claim 3 wherein the said electrically controlled means comprise two magnetrons each having an anode and a cathode, means for applying to said magnetrons magnetic and electro-static fields such that they are always outside the range of self oscillation,

means for coupling one of said magnetrons to each of said guides to impart therein a variable impedance dependent on the electric voltage applied between the magnetron anode and cathode, means for producing two recurrent electric voltages having the form of impulses of equal duration, means for varying the amplitudes of said voltages in opposite senses and means for applying the amplitude varied recurrent voltages to the magnetrons so that when one of the magnetrons cuts 01f the associated guide the other one opens its associated guide introducing therein a transmission coefficient proportional to the amplitude of the impulse applied thereto and vice versa.

6. A system according to claim 3 wherein the said electrically controlled means comprise two magnetrons each having an anode and a cathode, means for applying to said magnetrons magnetic and electro-static fields such that they are always outside the range of self oscillation, means for coupling one of said magnetrons to each of said guides to impart therein a variable impedance dependent on the electric voltage applied between the magnetron anode and cathode, means for producing two recurrent electric voltages having the form of impulses of equal duration, means for varying the amplitudes of said voltages in opposite senses, means for applying the amplitude varied recurrent voltages to the magnetrons so'that when one of the magnetrons cuts oflf the associated guide the other one opens its associated guide introducing therein a tr ansmissiqu coelficientpropgrtional to the arn- Plitqgle of the impulse-{applied ithereto and viee versa,

and-a common ultia high frequency transmitter coupled to b th 2 ..d 1

71A system according to claim 3 wherein. the, said eleot-rically controlled means comprise two magnetrons c i ha n l. a 92 and tlh m ans f l n to saidmaguetron s magnetic andel eet'r -static fields such a hey reia i ts d e ran e of lf-v a ti n means for coupling one of said magnetrons IOCElQll' of said guides to impart therein a variable impedance dependent on the. electric voltage applied between the magnetron anode and cathode, means for producingtwo recurrent electrie voltages ha ving the form of impulses of :equal duration, means forvarying -the. arn litutiles of:

said voltages in opposite senses, means for applying the amplitude varied recurrent voltages to the magnetrons so that. when one of the maguetrons' cuts off the associated guide the other one opens its associated guide introd uoing therein a transmission coeifieient proportional to the amplitude ,ofthe impulse appliedtthereto and vice versa, anda common signal comparing receiveradapted to determine and indicate-the moments of equality of amplitude of the signals fedthereto from said guides.

'8.- A method of'determining; the angular position of afirst point with respect to afseeor d point and to-an axis passing through said second point comprising the.

steps ofr'emittingultra-high frequency energy from one offsaid points, alternately Concentrating said energy at said se condjaoint into two lobe patterns intersectiug each other while continuously switchi ng said energy from one k equal for each of said lobe patterns, receiving 'salid a:

from one of said pointsg receiving said energy; at-the (it said energy in sai d lobes; the period'of 'the vanaho'igio lobe to the other, oppositely varyingfi e amplitude o f said lobe patterns according to a p' diet 'iie'd 1 law, the-interseetion of said' lobefpatterns deterimni n direction which is along said axis when the famp lit'iid'e highffrequency energy at the other'of 'saidfpoint's, and determining the i stant of equality between the e nergy' respectively receivedjfrom both" said lobes whereby the absolute angular position ot sai d first-point'with to said agris is determined,

' 9. In th e method of determining the-angular position of a first poi ntwith respeet to a second point and to an; axis passing V through said second point of "the t pe-c m pi'is ingrthe steps of'radiating ultra -high frequency energy of said points, con centratingi said energy at'eitherpfsaid; points into two lobe, patterns intersecting alon g said axis and continuously switehing saidlenergyxfroni lobe to: I theother the step of goppos'itely varying tliarn lit 0f said amplitude being substantially greaterthan ot' switching said 'lobes.

ReferencesCitedin-the file of-this patent- UNITED sures ermits 1,910,427 amqnst -v- Mai- 3511932 2: 2,408,425 Jenks et a1. Oct. 1, 1946 2,421,023 Frink May 27, 1947 2,509,230 1950 Himmel May 30,